Merge pull request #3592 from karalabe/hw-wallets

accounts: initial support for Ledger hardware wallets

122 files changed, 36084 insertions, 909 deletions

diff --git a/accounts/abi/bind/auth.go b/accounts/abi/bind/auth.go
index dbb235c14..e6bb0c3b5 100644
--- a/accounts/abi/bind/auth.go
+++ b/accounts/abi/bind/auth.go
@@ -22,7 +22,7 @@ import (
 	"io"
 	"io/ioutil"
 
-	"github.com/ethereum/go-ethereum/accounts"
+	"github.com/ethereum/go-ethereum/accounts/keystore"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/crypto"
@@ -35,7 +35,7 @@ func NewTransactor(keyin io.Reader, passphrase string) (*TransactOpts, error) {
 	if err != nil {
 		return nil, err
 	}
-	key, err := accounts.DecryptKey(json, passphrase)
+	key, err := keystore.DecryptKey(json, passphrase)
 	if err != nil {
 		return nil, err
 	}
diff --git a/accounts/account_manager.go b/accounts/account_manager.go
deleted file mode 100644
index 01dd62e25..000000000
--- a/accounts/account_manager.go
+++ /dev/null
@@ -1,350 +0,0 @@
-// Copyright 2015 The go-ethereum Authors
-// This file is part of the go-ethereum library.
-//
-// The go-ethereum library is free software: you can redistribute it and/or modify
-// it under the terms of the GNU Lesser General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-//
-// The go-ethereum library is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-// GNU Lesser General Public License for more details.
-//
-// You should have received a copy of the GNU Lesser General Public License
-// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
-
-// Package accounts implements encrypted storage of secp256k1 private keys.
-//
-// Keys are stored as encrypted JSON files according to the Web3 Secret Storage specification.
-// See https://github.com/ethereum/wiki/wiki/Web3-Secret-Storage-Definition for more information.
-package accounts
-
-import (
-	"crypto/ecdsa"
-	crand "crypto/rand"
-	"encoding/json"
-	"errors"
-	"fmt"
-	"os"
-	"path/filepath"
-	"runtime"
-	"sync"
-	"time"
-
-	"github.com/ethereum/go-ethereum/common"
-	"github.com/ethereum/go-ethereum/crypto"
-)
-
-var (
-	ErrLocked  = errors.New("account is locked")
-	ErrNoMatch = errors.New("no key for given address or file")
-	ErrDecrypt = errors.New("could not decrypt key with given passphrase")
-)
-
-// Account represents a stored key.
-// When used as an argument, it selects a unique key file to act on.
-type Account struct {
-	Address common.Address // Ethereum account address derived from the key
-
-	// File contains the key file name.
-	// When Acccount is used as an argument to select a key, File can be left blank to
-	// select just by address or set to the basename or absolute path of a file in the key
-	// directory. Accounts returned by Manager will always contain an absolute path.
-	File string
-}
-
-func (acc *Account) MarshalJSON() ([]byte, error) {
-	return []byte(`"` + acc.Address.Hex() + `"`), nil
-}
-
-func (acc *Account) UnmarshalJSON(raw []byte) error {
-	return json.Unmarshal(raw, &acc.Address)
-}
-
-// Manager manages a key storage directory on disk.
-type Manager struct {
-	cache    *addrCache
-	keyStore keyStore
-	mu       sync.RWMutex
-	unlocked map[common.Address]*unlocked
-}
-
-type unlocked struct {
-	*Key
-	abort chan struct{}
-}
-
-// NewManager creates a manager for the given directory.
-func NewManager(keydir string, scryptN, scryptP int) *Manager {
-	keydir, _ = filepath.Abs(keydir)
-	am := &Manager{keyStore: &keyStorePassphrase{keydir, scryptN, scryptP}}
-	am.init(keydir)
-	return am
-}
-
-// NewPlaintextManager creates a manager for the given directory.
-// Deprecated: Use NewManager.
-func NewPlaintextManager(keydir string) *Manager {
-	keydir, _ = filepath.Abs(keydir)
-	am := &Manager{keyStore: &keyStorePlain{keydir}}
-	am.init(keydir)
-	return am
-}
-
-func (am *Manager) init(keydir string) {
-	am.unlocked = make(map[common.Address]*unlocked)
-	am.cache = newAddrCache(keydir)
-	// TODO: In order for this finalizer to work, there must be no references
-	// to am. addrCache doesn't keep a reference but unlocked keys do,
-	// so the finalizer will not trigger until all timed unlocks have expired.
-	runtime.SetFinalizer(am, func(m *Manager) {
-		m.cache.close()
-	})
-}
-
-// HasAddress reports whether a key with the given address is present.
-func (am *Manager) HasAddress(addr common.Address) bool {
-	return am.cache.hasAddress(addr)
-}
-
-// Accounts returns all key files present in the directory.
-func (am *Manager) Accounts() []Account {
-	return am.cache.accounts()
-}
-
-// Delete deletes the key matched by account if the passphrase is correct.
-// If the account contains no filename, the address must match a unique key.
-func (am *Manager) Delete(a Account, passphrase string) error {
-	// Decrypting the key isn't really necessary, but we do
-	// it anyway to check the password and zero out the key
-	// immediately afterwards.
-	a, key, err := am.getDecryptedKey(a, passphrase)
-	if key != nil {
-		zeroKey(key.PrivateKey)
-	}
-	if err != nil {
-		return err
-	}
-	// The order is crucial here. The key is dropped from the
-	// cache after the file is gone so that a reload happening in
-	// between won't insert it into the cache again.
-	err = os.Remove(a.File)
-	if err == nil {
-		am.cache.delete(a)
-	}
-	return err
-}
-
-// Sign calculates a ECDSA signature for the given hash. The produced signature
-// is in the [R || S || V] format where V is 0 or 1.
-func (am *Manager) Sign(addr common.Address, hash []byte) ([]byte, error) {
-	am.mu.RLock()
-	defer am.mu.RUnlock()
-
-	unlockedKey, found := am.unlocked[addr]
-	if !found {
-		return nil, ErrLocked
-	}
-	return crypto.Sign(hash, unlockedKey.PrivateKey)
-}
-
-// SignWithPassphrase signs hash if the private key matching the given address
-// can be decrypted with the given passphrase. The produced signature is in the
-// [R || S || V] format where V is 0 or 1.
-func (am *Manager) SignWithPassphrase(a Account, passphrase string, hash []byte) (signature []byte, err error) {
-	_, key, err := am.getDecryptedKey(a, passphrase)
-	if err != nil {
-		return nil, err
-	}
-	defer zeroKey(key.PrivateKey)
-	return crypto.Sign(hash, key.PrivateKey)
-}
-
-// Unlock unlocks the given account indefinitely.
-func (am *Manager) Unlock(a Account, passphrase string) error {
-	return am.TimedUnlock(a, passphrase, 0)
-}
-
-// Lock removes the private key with the given address from memory.
-func (am *Manager) Lock(addr common.Address) error {
-	am.mu.Lock()
-	if unl, found := am.unlocked[addr]; found {
-		am.mu.Unlock()
-		am.expire(addr, unl, time.Duration(0)*time.Nanosecond)
-	} else {
-		am.mu.Unlock()
-	}
-	return nil
-}
-
-// TimedUnlock unlocks the given account with the passphrase. The account
-// stays unlocked for the duration of timeout. A timeout of 0 unlocks the account
-// until the program exits. The account must match a unique key file.
-//
-// If the account address is already unlocked for a duration, TimedUnlock extends or
-// shortens the active unlock timeout. If the address was previously unlocked
-// indefinitely the timeout is not altered.
-func (am *Manager) TimedUnlock(a Account, passphrase string, timeout time.Duration) error {
-	a, key, err := am.getDecryptedKey(a, passphrase)
-	if err != nil {
-		return err
-	}
-
-	am.mu.Lock()
-	defer am.mu.Unlock()
-	u, found := am.unlocked[a.Address]
-	if found {
-		if u.abort == nil {
-			// The address was unlocked indefinitely, so unlocking
-			// it with a timeout would be confusing.
-			zeroKey(key.PrivateKey)
-			return nil
-		} else {
-			// Terminate the expire goroutine and replace it below.
-			close(u.abort)
-		}
-	}
-	if timeout > 0 {
-		u = &unlocked{Key: key, abort: make(chan struct{})}
-		go am.expire(a.Address, u, timeout)
-	} else {
-		u = &unlocked{Key: key}
-	}
-	am.unlocked[a.Address] = u
-	return nil
-}
-
-// Find resolves the given account into a unique entry in the keystore.
-func (am *Manager) Find(a Account) (Account, error) {
-	am.cache.maybeReload()
-	am.cache.mu.Lock()
-	a, err := am.cache.find(a)
-	am.cache.mu.Unlock()
-	return a, err
-}
-
-func (am *Manager) getDecryptedKey(a Account, auth string) (Account, *Key, error) {
-	a, err := am.Find(a)
-	if err != nil {
-		return a, nil, err
-	}
-	key, err := am.keyStore.GetKey(a.Address, a.File, auth)
-	return a, key, err
-}
-
-func (am *Manager) expire(addr common.Address, u *unlocked, timeout time.Duration) {
-	t := time.NewTimer(timeout)
-	defer t.Stop()
-	select {
-	case <-u.abort:
-		// just quit
-	case <-t.C:
-		am.mu.Lock()
-		// only drop if it's still the same key instance that dropLater
-		// was launched with. we can check that using pointer equality
-		// because the map stores a new pointer every time the key is
-		// unlocked.
-		if am.unlocked[addr] == u {
-			zeroKey(u.PrivateKey)
-			delete(am.unlocked, addr)
-		}
-		am.mu.Unlock()
-	}
-}
-
-// NewAccount generates a new key and stores it into the key directory,
-// encrypting it with the passphrase.
-func (am *Manager) NewAccount(passphrase string) (Account, error) {
-	_, account, err := storeNewKey(am.keyStore, crand.Reader, passphrase)
-	if err != nil {
-		return Account{}, err
-	}
-	// Add the account to the cache immediately rather
-	// than waiting for file system notifications to pick it up.
-	am.cache.add(account)
-	return account, nil
-}
-
-// AccountByIndex returns the ith account.
-func (am *Manager) AccountByIndex(i int) (Account, error) {
-	accounts := am.Accounts()
-	if i < 0 || i >= len(accounts) {
-		return Account{}, fmt.Errorf("account index %d out of range [0, %d]", i, len(accounts)-1)
-	}
-	return accounts[i], nil
-}
-
-// Export exports as a JSON key, encrypted with newPassphrase.
-func (am *Manager) Export(a Account, passphrase, newPassphrase string) (keyJSON []byte, err error) {
-	_, key, err := am.getDecryptedKey(a, passphrase)
-	if err != nil {
-		return nil, err
-	}
-	var N, P int
-	if store, ok := am.keyStore.(*keyStorePassphrase); ok {
-		N, P = store.scryptN, store.scryptP
-	} else {
-		N, P = StandardScryptN, StandardScryptP
-	}
-	return EncryptKey(key, newPassphrase, N, P)
-}
-
-// Import stores the given encrypted JSON key into the key directory.
-func (am *Manager) Import(keyJSON []byte, passphrase, newPassphrase string) (Account, error) {
-	key, err := DecryptKey(keyJSON, passphrase)
-	if key != nil && key.PrivateKey != nil {
-		defer zeroKey(key.PrivateKey)
-	}
-	if err != nil {
-		return Account{}, err
-	}
-	return am.importKey(key, newPassphrase)
-}
-
-// ImportECDSA stores the given key into the key directory, encrypting it with the passphrase.
-func (am *Manager) ImportECDSA(priv *ecdsa.PrivateKey, passphrase string) (Account, error) {
-	key := newKeyFromECDSA(priv)
-	if am.cache.hasAddress(key.Address) {
-		return Account{}, fmt.Errorf("account already exists")
-	}
-
-	return am.importKey(key, passphrase)
-}
-
-func (am *Manager) importKey(key *Key, passphrase string) (Account, error) {
-	a := Account{Address: key.Address, File: am.keyStore.JoinPath(keyFileName(key.Address))}
-	if err := am.keyStore.StoreKey(a.File, key, passphrase); err != nil {
-		return Account{}, err
-	}
-	am.cache.add(a)
-	return a, nil
-}
-
-// Update changes the passphrase of an existing account.
-func (am *Manager) Update(a Account, passphrase, newPassphrase string) error {
-	a, key, err := am.getDecryptedKey(a, passphrase)
-	if err != nil {
-		return err
-	}
-	return am.keyStore.StoreKey(a.File, key, newPassphrase)
-}
-
-// ImportPreSaleKey decrypts the given Ethereum presale wallet and stores
-// a key file in the key directory. The key file is encrypted with the same passphrase.
-func (am *Manager) ImportPreSaleKey(keyJSON []byte, passphrase string) (Account, error) {
-	a, _, err := importPreSaleKey(am.keyStore, keyJSON, passphrase)
-	if err != nil {
-		return a, err
-	}
-	am.cache.add(a)
-	return a, nil
-}
-
-// zeroKey zeroes a private key in memory.
-func zeroKey(k *ecdsa.PrivateKey) {
-	b := k.D.Bits()
-	for i := range b {
-		b[i] = 0
-	}
-}
diff --git a/accounts/accounts.go b/accounts/accounts.go
new file mode 100644
index 000000000..640de5220
--- /dev/null
+++ b/accounts/accounts.go
@@ -0,0 +1,155 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+// Package accounts implements high level Ethereum account management.
+package accounts
+
+import (
+	"math/big"
+
+	ethereum "github.com/ethereum/go-ethereum"
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/event"
+)
+
+// Account represents an Ethereum account located at a specific location defined
+// by the optional URL field.
+type Account struct {
+	Address common.Address `json:"address"` // Ethereum account address derived from the key
+	URL     URL            `json:"url"`     // Optional resource locator within a backend
+}
+
+// Wallet represents a software or hardware wallet that might contain one or more
+// accounts (derived from the same seed).
+type Wallet interface {
+	// URL retrieves the canonical path under which this wallet is reachable. It is
+	// user by upper layers to define a sorting order over all wallets from multiple
+	// backends.
+	URL() URL
+
+	// Status returns a textual status to aid the user in the current state of the
+	// wallet.
+	Status() string
+
+	// Open initializes access to a wallet instance. It is not meant to unlock or
+	// decrypt account keys, rather simply to establish a connection to hardware
+	// wallets and/or to access derivation seeds.
+	//
+	// The passphrase parameter may or may not be used by the implementation of a
+	// particular wallet instance. The reason there is no passwordless open method
+	// is to strive towards a uniform wallet handling, oblivious to the different
+	// backend providers.
+	//
+	// Please note, if you open a wallet, you must close it to release any allocated
+	// resources (especially important when working with hardware wallets).
+	Open(passphrase string) error
+
+	// Close releases any resources held by an open wallet instance.
+	Close() error
+
+	// Accounts retrieves the list of signing accounts the wallet is currently aware
+	// of. For hierarchical deterministic wallets, the list will not be exhaustive,
+	// rather only contain the accounts explicitly pinned during account derivation.
+	Accounts() []Account
+
+	// Contains returns whether an account is part of this particular wallet or not.
+	Contains(account Account) bool
+
+	// Derive attempts to explicitly derive a hierarchical deterministic account at
+	// the specified derivation path. If requested, the derived account will be added
+	// to the wallet's tracked account list.
+	Derive(path DerivationPath, pin bool) (Account, error)
+
+	// SelfDerive sets a base account derivation path from which the wallet attempts
+	// to discover non zero accounts and automatically add them to list of tracked
+	// accounts.
+	//
+	// Note, self derivaton will increment the last component of the specified path
+	// opposed to decending into a child path to allow discovering accounts starting
+	// from non zero components.
+	//
+	// You can disable automatic account discovery by calling SelfDerive with a nil
+	// chain state reader.
+	SelfDerive(base DerivationPath, chain ethereum.ChainStateReader)
+
+	// SignHash requests the wallet to sign the given hash.
+	//
+	// It looks up the account specified either solely via its address contained within,
+	// or optionally with the aid of any location metadata from the embedded URL field.
+	//
+	// If the wallet requires additional authentication to sign the request (e.g.
+	// a password to decrypt the account, or a PIN code o verify the transaction),
+	// an AuthNeededError instance will be returned, containing infos for the user
+	// about which fields or actions are needed. The user may retry by providing
+	// the needed details via SignHashWithPassphrase, or by other means (e.g. unlock
+	// the account in a keystore).
+	SignHash(account Account, hash []byte) ([]byte, error)
+
+	// SignTx requests the wallet to sign the given transaction.
+	//
+	// It looks up the account specified either solely via its address contained within,
+	// or optionally with the aid of any location metadata from the embedded URL field.
+	//
+	// If the wallet requires additional authentication to sign the request (e.g.
+	// a password to decrypt the account, or a PIN code o verify the transaction),
+	// an AuthNeededError instance will be returned, containing infos for the user
+	// about which fields or actions are needed. The user may retry by providing
+	// the needed details via SignTxWithPassphrase, or by other means (e.g. unlock
+	// the account in a keystore).
+	SignTx(account Account, tx *types.Transaction, chainID *big.Int) (*types.Transaction, error)
+
+	// SignHashWithPassphrase requests the wallet to sign the given hash with the
+	// given passphrase as extra authentication information.
+	//
+	// It looks up the account specified either solely via its address contained within,
+	// or optionally with the aid of any location metadata from the embedded URL field.
+	SignHashWithPassphrase(account Account, passphrase string, hash []byte) ([]byte, error)
+
+	// SignTxWithPassphrase requests the wallet to sign the given transaction, with the
+	// given passphrase as extra authentication information.
+	//
+	// It looks up the account specified either solely via its address contained within,
+	// or optionally with the aid of any location metadata from the embedded URL field.
+	SignTxWithPassphrase(account Account, passphrase string, tx *types.Transaction, chainID *big.Int) (*types.Transaction, error)
+}
+
+// Backend is a "wallet provider" that may contain a batch of accounts they can
+// sign transactions with and upon request, do so.
+type Backend interface {
+	// Wallets retrieves the list of wallets the backend is currently aware of.
+	//
+	// The returned wallets are not opened by default. For software HD wallets this
+	// means that no base seeds are decrypted, and for hardware wallets that no actual
+	// connection is established.
+	//
+	// The resulting wallet list will be sorted alphabetically based on its internal
+	// URL assigned by the backend. Since wallets (especially hardware) may come and
+	// go, the same wallet might appear at a different positions in the list during
+	// subsequent retrievals.
+	Wallets() []Wallet
+
+	// Subscribe creates an async subscription to receive notifications when the
+	// backend detects the arrival or departure of a wallet.
+	Subscribe(sink chan<- WalletEvent) event.Subscription
+}
+
+// WalletEvent is an event fired by an account backend when a wallet arrival or
+// departure is detected.
+type WalletEvent struct {
+	Wallet Wallet // Wallet instance arrived or departed
+	Arrive bool   // Whether the wallet was added or removed
+}
diff --git a/accounts/accounts_test.go b/accounts/accounts_test.go
deleted file mode 100644
index b3ab87d50..000000000
--- a/accounts/accounts_test.go
+++ /dev/null
@@ -1,224 +0,0 @@
-// Copyright 2015 The go-ethereum Authors
-// This file is part of the go-ethereum library.
-//
-// The go-ethereum library is free software: you can redistribute it and/or modify
-// it under the terms of the GNU Lesser General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-//
-// The go-ethereum library is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-// GNU Lesser General Public License for more details.
-//
-// You should have received a copy of the GNU Lesser General Public License
-// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
-
-package accounts
-
-import (
-	"io/ioutil"
-	"os"
-	"runtime"
-	"strings"
-	"testing"
-	"time"
-
-	"github.com/ethereum/go-ethereum/common"
-)
-
-var testSigData = make([]byte, 32)
-
-func TestManager(t *testing.T) {
-	dir, am := tmpManager(t, true)
-	defer os.RemoveAll(dir)
-
-	a, err := am.NewAccount("foo")
-	if err != nil {
-		t.Fatal(err)
-	}
-	if !strings.HasPrefix(a.File, dir) {
-		t.Errorf("account file %s doesn't have dir prefix", a.File)
-	}
-	stat, err := os.Stat(a.File)
-	if err != nil {
-		t.Fatalf("account file %s doesn't exist (%v)", a.File, err)
-	}
-	if runtime.GOOS != "windows" && stat.Mode() != 0600 {
-		t.Fatalf("account file has wrong mode: got %o, want %o", stat.Mode(), 0600)
-	}
-	if !am.HasAddress(a.Address) {
-		t.Errorf("HasAccount(%x) should've returned true", a.Address)
-	}
-	if err := am.Update(a, "foo", "bar"); err != nil {
-		t.Errorf("Update error: %v", err)
-	}
-	if err := am.Delete(a, "bar"); err != nil {
-		t.Errorf("Delete error: %v", err)
-	}
-	if common.FileExist(a.File) {
-		t.Errorf("account file %s should be gone after Delete", a.File)
-	}
-	if am.HasAddress(a.Address) {
-		t.Errorf("HasAccount(%x) should've returned true after Delete", a.Address)
-	}
-}
-
-func TestSign(t *testing.T) {
-	dir, am := tmpManager(t, true)
-	defer os.RemoveAll(dir)
-
-	pass := "" // not used but required by API
-	a1, err := am.NewAccount(pass)
-	if err != nil {
-		t.Fatal(err)
-	}
-	if err := am.Unlock(a1, ""); err != nil {
-		t.Fatal(err)
-	}
-	if _, err := am.Sign(a1.Address, testSigData); err != nil {
-		t.Fatal(err)
-	}
-}
-
-func TestSignWithPassphrase(t *testing.T) {
-	dir, am := tmpManager(t, true)
-	defer os.RemoveAll(dir)
-
-	pass := "passwd"
-	acc, err := am.NewAccount(pass)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	if _, unlocked := am.unlocked[acc.Address]; unlocked {
-		t.Fatal("expected account to be locked")
-	}
-
-	_, err = am.SignWithPassphrase(acc, pass, testSigData)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	if _, unlocked := am.unlocked[acc.Address]; unlocked {
-		t.Fatal("expected account to be locked")
-	}
-
-	if _, err = am.SignWithPassphrase(acc, "invalid passwd", testSigData); err == nil {
-		t.Fatal("expected SignHash to fail with invalid password")
-	}
-}
-
-func TestTimedUnlock(t *testing.T) {
-	dir, am := tmpManager(t, true)
-	defer os.RemoveAll(dir)
-
-	pass := "foo"
-	a1, err := am.NewAccount(pass)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	// Signing without passphrase fails because account is locked
-	_, err = am.Sign(a1.Address, testSigData)
-	if err != ErrLocked {
-		t.Fatal("Signing should've failed with ErrLocked before unlocking, got ", err)
-	}
-
-	// Signing with passphrase works
-	if err = am.TimedUnlock(a1, pass, 100*time.Millisecond); err != nil {
-		t.Fatal(err)
-	}
-
-	// Signing without passphrase works because account is temp unlocked
-	_, err = am.Sign(a1.Address, testSigData)
-	if err != nil {
-		t.Fatal("Signing shouldn't return an error after unlocking, got ", err)
-	}
-
-	// Signing fails again after automatic locking
-	time.Sleep(250 * time.Millisecond)
-	_, err = am.Sign(a1.Address, testSigData)
-	if err != ErrLocked {
-		t.Fatal("Signing should've failed with ErrLocked timeout expired, got ", err)
-	}
-}
-
-func TestOverrideUnlock(t *testing.T) {
-	dir, am := tmpManager(t, false)
-	defer os.RemoveAll(dir)
-
-	pass := "foo"
-	a1, err := am.NewAccount(pass)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	// Unlock indefinitely.
-	if err = am.TimedUnlock(a1, pass, 5*time.Minute); err != nil {
-		t.Fatal(err)
-	}
-
-	// Signing without passphrase works because account is temp unlocked
-	_, err = am.Sign(a1.Address, testSigData)
-	if err != nil {
-		t.Fatal("Signing shouldn't return an error after unlocking, got ", err)
-	}
-
-	// reset unlock to a shorter period, invalidates the previous unlock
-	if err = am.TimedUnlock(a1, pass, 100*time.Millisecond); err != nil {
-		t.Fatal(err)
-	}
-
-	// Signing without passphrase still works because account is temp unlocked
-	_, err = am.Sign(a1.Address, testSigData)
-	if err != nil {
-		t.Fatal("Signing shouldn't return an error after unlocking, got ", err)
-	}
-
-	// Signing fails again after automatic locking
-	time.Sleep(250 * time.Millisecond)
-	_, err = am.Sign(a1.Address, testSigData)
-	if err != ErrLocked {
-		t.Fatal("Signing should've failed with ErrLocked timeout expired, got ", err)
-	}
-}
-
-// This test should fail under -race if signing races the expiration goroutine.
-func TestSignRace(t *testing.T) {
-	dir, am := tmpManager(t, false)
-	defer os.RemoveAll(dir)
-
-	// Create a test account.
-	a1, err := am.NewAccount("")
-	if err != nil {
-		t.Fatal("could not create the test account", err)
-	}
-
-	if err := am.TimedUnlock(a1, "", 15*time.Millisecond); err != nil {
-		t.Fatal("could not unlock the test account", err)
-	}
-	end := time.Now().Add(500 * time.Millisecond)
-	for time.Now().Before(end) {
-		if _, err := am.Sign(a1.Address, testSigData); err == ErrLocked {
-			return
-		} else if err != nil {
-			t.Errorf("Sign error: %v", err)
-			return
-		}
-		time.Sleep(1 * time.Millisecond)
-	}
-	t.Errorf("Account did not lock within the timeout")
-}
-
-func tmpManager(t *testing.T, encrypted bool) (string, *Manager) {
-	d, err := ioutil.TempDir("", "eth-keystore-test")
-	if err != nil {
-		t.Fatal(err)
-	}
-	new := NewPlaintextManager
-	if encrypted {
-		new = func(kd string) *Manager { return NewManager(kd, veryLightScryptN, veryLightScryptP) }
-	}
-	return d, new(d)
-}
diff --git a/accounts/errors.go b/accounts/errors.go
new file mode 100644
index 000000000..9ecc1eafd
--- /dev/null
+++ b/accounts/errors.go
@@ -0,0 +1,68 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package accounts
+
+import (
+	"errors"
+	"fmt"
+)
+
+// ErrUnknownAccount is returned for any requested operation for which no backend
+// provides the specified account.
+var ErrUnknownAccount = errors.New("unknown account")
+
+// ErrUnknownWallet is returned for any requested operation for which no backend
+// provides the specified wallet.
+var ErrUnknownWallet = errors.New("unknown wallet")
+
+// ErrNotSupported is returned when an operation is requested from an account
+// backend that it does not support.
+var ErrNotSupported = errors.New("not supported")
+
+// ErrInvalidPassphrase is returned when a decryption operation receives a bad
+// passphrase.
+var ErrInvalidPassphrase = errors.New("invalid passphrase")
+
+// ErrWalletAlreadyOpen is returned if a wallet is attempted to be opened the
+// secodn time.
+var ErrWalletAlreadyOpen = errors.New("wallet already open")
+
+// ErrWalletClosed is returned if a wallet is attempted to be opened the
+// secodn time.
+var ErrWalletClosed = errors.New("wallet closed")
+
+// AuthNeededError is returned by backends for signing requests where the user
+// is required to provide further authentication before signing can succeed.
+//
+// This usually means either that a password needs to be supplied, or perhaps a
+// one time PIN code displayed by some hardware device.
+type AuthNeededError struct {
+	Needed string // Extra authentication the user needs to provide
+}
+
+// NewAuthNeededError creates a new authentication error with the extra details
+// about the needed fields set.
+func NewAuthNeededError(needed string) error {
+	return &AuthNeededError{
+		Needed: needed,
+	}
+}
+
+// Error implements the standard error interfacel.
+func (err *AuthNeededError) Error() string {
+	return fmt.Sprintf("authentication needed: %s", err.Needed)
+}
diff --git a/accounts/hd.go b/accounts/hd.go
new file mode 100644
index 000000000..e8bc191af
--- /dev/null
+++ b/accounts/hd.go
@@ -0,0 +1,130 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package accounts
+
+import (
+	"errors"
+	"fmt"
+	"math"
+	"math/big"
+	"strings"
+)
+
+// DefaultRootDerivationPath is the root path to which custom derivation endpoints
+// are appended. As such, the first account will be at m/44'/60'/0'/0, the second
+// at m/44'/60'/0'/1, etc.
+var DefaultRootDerivationPath = DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0}
+
+// DefaultBaseDerivationPath is the base path from which custom derivation endpoints
+// are incremented. As such, the first account will be at m/44'/60'/0'/0, the second
+// at m/44'/60'/0'/1, etc.
+var DefaultBaseDerivationPath = DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0}
+
+// DerivationPath represents the computer friendly version of a hierarchical
+// deterministic wallet account derivaion path.
+//
+// The BIP-32 spec https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki
+// defines derivation paths to be of the form:
+//
+//   m / purpose' / coin_type' / account' / change / address_index
+//
+// The BIP-44 spec https://github.com/bitcoin/bips/blob/master/bip-0044.mediawiki
+// defines that the `purpose` be 44' (or 0x8000002C) for crypto currencies, and
+// SLIP-44 https://github.com/satoshilabs/slips/blob/master/slip-0044.md assigns
+// the `coin_type` 60' (or 0x8000003C) to Ethereum.
+//
+// The root path for Ethereum is m/44'/60'/0'/0 according to the specification
+// from https://github.com/ethereum/EIPs/issues/84, albeit it's not set in stone
+// yet whether accounts should increment the last component or the children of
+// that. We will go with the simpler approach of incrementing the last component.
+type DerivationPath []uint32
+
+// ParseDerivationPath converts a user specified derivation path string to the
+// internal binary representation.
+//
+// Full derivation paths need to start with the `m/` prefix, relative derivation
+// paths (which will get appended to the default root path) must not have prefixes
+// in front of the first element. Whitespace is ignored.
+func ParseDerivationPath(path string) (DerivationPath, error) {
+	var result DerivationPath
+
+	// Handle absolute or relative paths
+	components := strings.Split(path, "/")
+	switch {
+	case len(components) == 0:
+		return nil, errors.New("empty derivation path")
+
+	case strings.TrimSpace(components[0]) == "":
+		return nil, errors.New("ambiguous path: use 'm/' prefix for absolute paths, or no leading '/' for relative ones")
+
+	case strings.TrimSpace(components[0]) == "m":
+		components = components[1:]
+
+	default:
+		result = append(result, DefaultRootDerivationPath...)
+	}
+	// All remaining components are relative, append one by one
+	if len(components) == 0 {
+		return nil, errors.New("empty derivation path") // Empty relative paths
+	}
+	for _, component := range components {
+		// Ignore any user added whitespace
+		component = strings.TrimSpace(component)
+		var value uint32
+
+		// Handle hardened paths
+		if strings.HasSuffix(component, "'") {
+			value = 0x80000000
+			component = strings.TrimSpace(strings.TrimSuffix(component, "'"))
+		}
+		// Handle the non hardened component
+		bigval, ok := new(big.Int).SetString(component, 0)
+		if !ok {
+			return nil, fmt.Errorf("invalid component: %s", component)
+		}
+		max := math.MaxUint32 - value
+		if bigval.Sign() < 0 || bigval.Cmp(big.NewInt(int64(max))) > 0 {
+			if value == 0 {
+				return nil, fmt.Errorf("component %v out of allowed range [0, %d]", bigval, max)
+			}
+			return nil, fmt.Errorf("component %v out of allowed hardened range [0, %d]", bigval, max)
+		}
+		value += uint32(bigval.Uint64())
+
+		// Append and repeat
+		result = append(result, value)
+	}
+	return result, nil
+}
+
+// String implements the stringer interface, converting a binary derivation path
+// to its canonical representation.
+func (path DerivationPath) String() string {
+	result := "m"
+	for _, component := range path {
+		var hardened bool
+		if component >= 0x80000000 {
+			component -= 0x80000000
+			hardened = true
+		}
+		result = fmt.Sprintf("%s/%d", result, component)
+		if hardened {
+			result += "'"
+		}
+	}
+	return result
+}
diff --git a/accounts/hd_test.go b/accounts/hd_test.go
new file mode 100644
index 000000000..83ec34adb
--- /dev/null
+++ b/accounts/hd_test.go
@@ -0,0 +1,79 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package accounts
+
+import (
+	"reflect"
+	"testing"
+)
+
+// Tests that HD derivation paths can be correctly parsed into our internal binary
+// representation.
+func TestHDPathParsing(t *testing.T) {
+	tests := []struct {
+		input  string
+		output DerivationPath
+	}{
+		// Plain absolute derivation paths
+		{"m/44'/60'/0'/0", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0}},
+		{"m/44'/60'/0'/128", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 128}},
+		{"m/44'/60'/0'/0'", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0x80000000 + 0}},
+		{"m/44'/60'/0'/128'", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0x80000000 + 128}},
+		{"m/2147483692/2147483708/2147483648/0", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0}},
+		{"m/2147483692/2147483708/2147483648/2147483648", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0x80000000 + 0}},
+
+		// Plain relative derivation paths
+		{"0", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0}},
+		{"128", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 128}},
+		{"0'", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0x80000000 + 0}},
+		{"128'", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0x80000000 + 128}},
+		{"2147483648", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0x80000000 + 0}},
+
+		// Hexadecimal absolute derivation paths
+		{"m/0x2C'/0x3c'/0x00'/0x00", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0}},
+		{"m/0x2C'/0x3c'/0x00'/0x80", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 128}},
+		{"m/0x2C'/0x3c'/0x00'/0x00'", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0x80000000 + 0}},
+		{"m/0x2C'/0x3c'/0x00'/0x80'", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0x80000000 + 128}},
+		{"m/0x8000002C/0x8000003c/0x80000000/0x00", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0}},
+		{"m/0x8000002C/0x8000003c/0x80000000/0x80000000", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0x80000000 + 0}},
+
+		// Hexadecimal relative derivation paths
+		{"0x00", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0}},
+		{"0x80", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 128}},
+		{"0x00'", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0x80000000 + 0}},
+		{"0x80'", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0x80000000 + 128}},
+		{"0x80000000", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0x80000000 + 0}},
+
+		// Weird inputs just to ensure they work
+		{"	m  /   44			'\n/\n   60	\n\n\t'   /\n0 ' /\t\t	0", DerivationPath{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0}},
+
+		// Invaid derivation paths
+		{"", nil},              // Empty relative derivation path
+		{"m", nil},             // Empty absolute derivation path
+		{"m/", nil},            // Missing last derivation component
+		{"/44'/60'/0'/0", nil}, // Absolute path without m prefix, might be user error
+		{"m/2147483648'", nil}, // Overflows 32 bit integer
+		{"m/-1'", nil},         // Cannot contain negative number
+	}
+	for i, tt := range tests {
+		if path, err := ParseDerivationPath(tt.input); !reflect.DeepEqual(path, tt.output) {
+			t.Errorf("test %d: parse mismatch: have %v (%v), want %v", i, path, err, tt.output)
+		} else if path == nil && err == nil {
+			t.Errorf("test %d: nil path and error: %v", i, err)
+		}
+	}
+}
diff --git a/accounts/addrcache.go b/accounts/keystore/account_cache.go
index a99f23606..3fae3ef5b 100644
--- a/accounts/addrcache.go
+++ b/accounts/keystore/account_cache.go
@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU Lesser General Public License
 // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
 
-package accounts
+package keystore
 
 import (
 	"bufio"
@@ -28,6 +28,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/ethereum/go-ethereum/accounts"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/logger"
 	"github.com/ethereum/go-ethereum/logger/glog"
@@ -38,23 +39,23 @@ import (
 // exist yet, the code will attempt to create a watcher at most this often.
 const minReloadInterval = 2 * time.Second
 
-type accountsByFile []Account
+type accountsByURL []accounts.Account
 
-func (s accountsByFile) Len() int           { return len(s) }
-func (s accountsByFile) Less(i, j int) bool { return s[i].File < s[j].File }
-func (s accountsByFile) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
+func (s accountsByURL) Len() int           { return len(s) }
+func (s accountsByURL) Less(i, j int) bool { return s[i].URL.Cmp(s[j].URL) < 0 }
+func (s accountsByURL) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
 
 // AmbiguousAddrError is returned when attempting to unlock
 // an address for which more than one file exists.
 type AmbiguousAddrError struct {
 	Addr    common.Address
-	Matches []Account
+	Matches []accounts.Account
 }
 
 func (err *AmbiguousAddrError) Error() string {
 	files := ""
 	for i, a := range err.Matches {
-		files += a.File
+		files += a.URL.Path
 		if i < len(err.Matches)-1 {
 			files += ", "
 		}
@@ -62,60 +63,63 @@ func (err *AmbiguousAddrError) Error() string {
 	return fmt.Sprintf("multiple keys match address (%s)", files)
 }
 
-// addrCache is a live index of all accounts in the keystore.
-type addrCache struct {
+// accountCache is a live index of all accounts in the keystore.
+type accountCache struct {
 	keydir   string
 	watcher  *watcher
 	mu       sync.Mutex
-	all      accountsByFile
-	byAddr   map[common.Address][]Account
+	all      accountsByURL
+	byAddr   map[common.Address][]accounts.Account
 	throttle *time.Timer
+	notify   chan struct{}
 }
 
-func newAddrCache(keydir string) *addrCache {
-	ac := &addrCache{
+func newAccountCache(keydir string) (*accountCache, chan struct{}) {
+	ac := &accountCache{
 		keydir: keydir,
-		byAddr: make(map[common.Address][]Account),
+		byAddr: make(map[common.Address][]accounts.Account),
+		notify: make(chan struct{}, 1),
 	}
 	ac.watcher = newWatcher(ac)
-	return ac
+	return ac, ac.notify
 }
 
-func (ac *addrCache) accounts() []Account {
+func (ac *accountCache) accounts() []accounts.Account {
 	ac.maybeReload()
 	ac.mu.Lock()
 	defer ac.mu.Unlock()
-	cpy := make([]Account, len(ac.all))
+	cpy := make([]accounts.Account, len(ac.all))
 	copy(cpy, ac.all)
 	return cpy
 }
 
-func (ac *addrCache) hasAddress(addr common.Address) bool {
+func (ac *accountCache) hasAddress(addr common.Address) bool {
 	ac.maybeReload()
 	ac.mu.Lock()
 	defer ac.mu.Unlock()
 	return len(ac.byAddr[addr]) > 0
 }
 
-func (ac *addrCache) add(newAccount Account) {
+func (ac *accountCache) add(newAccount accounts.Account) {
 	ac.mu.Lock()
 	defer ac.mu.Unlock()
 
-	i := sort.Search(len(ac.all), func(i int) bool { return ac.all[i].File >= newAccount.File })
+	i := sort.Search(len(ac.all), func(i int) bool { return ac.all[i].URL.Cmp(newAccount.URL) >= 0 })
 	if i < len(ac.all) && ac.all[i] == newAccount {
 		return
 	}
 	// newAccount is not in the cache.
-	ac.all = append(ac.all, Account{})
+	ac.all = append(ac.all, accounts.Account{})
 	copy(ac.all[i+1:], ac.all[i:])
 	ac.all[i] = newAccount
 	ac.byAddr[newAccount.Address] = append(ac.byAddr[newAccount.Address], newAccount)
 }
 
 // note: removed needs to be unique here (i.e. both File and Address must be set).
-func (ac *addrCache) delete(removed Account) {
+func (ac *accountCache) delete(removed accounts.Account) {
 	ac.mu.Lock()
 	defer ac.mu.Unlock()
+
 	ac.all = removeAccount(ac.all, removed)
 	if ba := removeAccount(ac.byAddr[removed.Address], removed); len(ba) == 0 {
 		delete(ac.byAddr, removed.Address)
@@ -124,7 +128,7 @@ func (ac *addrCache) delete(removed Account) {
 	}
 }
 
-func removeAccount(slice []Account, elem Account) []Account {
+func removeAccount(slice []accounts.Account, elem accounts.Account) []accounts.Account {
 	for i := range slice {
 		if slice[i] == elem {
 			return append(slice[:i], slice[i+1:]...)
@@ -134,43 +138,44 @@ func removeAccount(slice []Account, elem Account) []Account {
 }
 
 // find returns the cached account for address if there is a unique match.
-// The exact matching rules are explained by the documentation of Account.
+// The exact matching rules are explained by the documentation of accounts.Account.
 // Callers must hold ac.mu.
-func (ac *addrCache) find(a Account) (Account, error) {
+func (ac *accountCache) find(a accounts.Account) (accounts.Account, error) {
 	// Limit search to address candidates if possible.
 	matches := ac.all
 	if (a.Address != common.Address{}) {
 		matches = ac.byAddr[a.Address]
 	}
-	if a.File != "" {
+	if a.URL.Path != "" {
 		// If only the basename is specified, complete the path.
-		if !strings.ContainsRune(a.File, filepath.Separator) {
-			a.File = filepath.Join(ac.keydir, a.File)
+		if !strings.ContainsRune(a.URL.Path, filepath.Separator) {
+			a.URL.Path = filepath.Join(ac.keydir, a.URL.Path)
 		}
 		for i := range matches {
-			if matches[i].File == a.File {
+			if matches[i].URL == a.URL {
 				return matches[i], nil
 			}
 		}
 		if (a.Address == common.Address{}) {
-			return Account{}, ErrNoMatch
+			return accounts.Account{}, ErrNoMatch
 		}
 	}
 	switch len(matches) {
 	case 1:
 		return matches[0], nil
 	case 0:
-		return Account{}, ErrNoMatch
+		return accounts.Account{}, ErrNoMatch
 	default:
-		err := &AmbiguousAddrError{Addr: a.Address, Matches: make([]Account, len(matches))}
+		err := &AmbiguousAddrError{Addr: a.Address, Matches: make([]accounts.Account, len(matches))}
 		copy(err.Matches, matches)
-		return Account{}, err
+		return accounts.Account{}, err
 	}
 }
 
-func (ac *addrCache) maybeReload() {
+func (ac *accountCache) maybeReload() {
 	ac.mu.Lock()
 	defer ac.mu.Unlock()
+
 	if ac.watcher.running {
 		return // A watcher is running and will keep the cache up-to-date.
 	}
@@ -188,18 +193,22 @@ func (ac *addrCache) maybeReload() {
 	ac.throttle.Reset(minReloadInterval)
 }
 
-func (ac *addrCache) close() {
+func (ac *accountCache) close() {
 	ac.mu.Lock()
 	ac.watcher.close()
 	if ac.throttle != nil {
 		ac.throttle.Stop()
 	}
+	if ac.notify != nil {
+		close(ac.notify)
+		ac.notify = nil
+	}
 	ac.mu.Unlock()
 }
 
 // reload caches addresses of existing accounts.
 // Callers must hold ac.mu.
-func (ac *addrCache) reload() {
+func (ac *accountCache) reload() {
 	accounts, err := ac.scan()
 	if err != nil && glog.V(logger.Debug) {
 		glog.Errorf("can't load keys: %v", err)
@@ -212,10 +221,14 @@ func (ac *addrCache) reload() {
 	for _, a := range accounts {
 		ac.byAddr[a.Address] = append(ac.byAddr[a.Address], a)
 	}
+	select {
+	case ac.notify <- struct{}{}:
+	default:
+	}
 	glog.V(logger.Debug).Infof("reloaded keys, cache has %d accounts", len(ac.all))
 }
 
-func (ac *addrCache) scan() ([]Account, error) {
+func (ac *accountCache) scan() ([]accounts.Account, error) {
 	files, err := ioutil.ReadDir(ac.keydir)
 	if err != nil {
 		return nil, err
@@ -223,7 +236,7 @@ func (ac *addrCache) scan() ([]Account, error) {
 
 	var (
 		buf     = new(bufio.Reader)
-		addrs   []Account
+		addrs   []accounts.Account
 		keyJSON struct {
 			Address string `json:"address"`
 		}
@@ -250,7 +263,7 @@ func (ac *addrCache) scan() ([]Account, error) {
 		case (addr == common.Address{}):
 			glog.V(logger.Debug).Infof("can't decode key %s: missing or zero address", path)
 		default:
-			addrs = append(addrs, Account{Address: addr, File: path})
+			addrs = append(addrs, accounts.Account{Address: addr, URL: accounts.URL{Scheme: KeyStoreScheme, Path: path}})
 		}
 		fd.Close()
 	}
diff --git a/accounts/addrcache_test.go b/accounts/keystore/account_cache_test.go
index e5f08cffc..554196321 100644
--- a/accounts/addrcache_test.go
+++ b/accounts/keystore/account_cache_test.go
@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU Lesser General Public License
 // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
 
-package accounts
+package keystore
 
 import (
 	"fmt"
@@ -28,23 +28,24 @@ import (
 
 	"github.com/cespare/cp"
 	"github.com/davecgh/go-spew/spew"
+	"github.com/ethereum/go-ethereum/accounts"
 	"github.com/ethereum/go-ethereum/common"
 )
 
 var (
 	cachetestDir, _   = filepath.Abs(filepath.Join("testdata", "keystore"))
-	cachetestAccounts = []Account{
+	cachetestAccounts = []accounts.Account{
 		{
 			Address: common.HexToAddress("7ef5a6135f1fd6a02593eedc869c6d41d934aef8"),
-			File:    filepath.Join(cachetestDir, "UTC--2016-03-22T12-57-55.920751759Z--7ef5a6135f1fd6a02593eedc869c6d41d934aef8"),
+			URL:     accounts.URL{Scheme: KeyStoreScheme, Path: filepath.Join(cachetestDir, "UTC--2016-03-22T12-57-55.920751759Z--7ef5a6135f1fd6a02593eedc869c6d41d934aef8")},
 		},
 		{
 			Address: common.HexToAddress("f466859ead1932d743d622cb74fc058882e8648a"),
-			File:    filepath.Join(cachetestDir, "aaa"),
+			URL:     accounts.URL{Scheme: KeyStoreScheme, Path: filepath.Join(cachetestDir, "aaa")},
 		},
 		{
 			Address: common.HexToAddress("289d485d9771714cce91d3393d764e1311907acc"),
-			File:    filepath.Join(cachetestDir, "zzz"),
+			URL:     accounts.URL{Scheme: KeyStoreScheme, Path: filepath.Join(cachetestDir, "zzz")},
 		},
 	}
 )
@@ -52,29 +53,36 @@ var (
 func TestWatchNewFile(t *testing.T) {
 	t.Parallel()
 
-	dir, am := tmpManager(t, false)
+	dir, ks := tmpKeyStore(t, false)
 	defer os.RemoveAll(dir)
 
 	// Ensure the watcher is started before adding any files.
-	am.Accounts()
+	ks.Accounts()
 	time.Sleep(200 * time.Millisecond)
 
 	// Move in the files.
-	wantAccounts := make([]Account, len(cachetestAccounts))
+	wantAccounts := make([]accounts.Account, len(cachetestAccounts))
 	for i := range cachetestAccounts {
-		a := cachetestAccounts[i]
-		a.File = filepath.Join(dir, filepath.Base(a.File))
-		wantAccounts[i] = a
-		if err := cp.CopyFile(a.File, cachetestAccounts[i].File); err != nil {
+		wantAccounts[i] = accounts.Account{
+			Address: cachetestAccounts[i].Address,
+			URL:     accounts.URL{Scheme: KeyStoreScheme, Path: filepath.Join(dir, filepath.Base(cachetestAccounts[i].URL.Path))},
+		}
+		if err := cp.CopyFile(wantAccounts[i].URL.Path, cachetestAccounts[i].URL.Path); err != nil {
 			t.Fatal(err)
 		}
 	}
 
-	// am should see the accounts.
-	var list []Account
+	// ks should see the accounts.
+	var list []accounts.Account
 	for d := 200 * time.Millisecond; d < 5*time.Second; d *= 2 {
-		list = am.Accounts()
+		list = ks.Accounts()
 		if reflect.DeepEqual(list, wantAccounts) {
+			// ks should have also received change notifications
+			select {
+			case <-ks.changes:
+			default:
+				t.Fatalf("wasn't notified of new accounts")
+			}
 			return
 		}
 		time.Sleep(d)
@@ -85,12 +93,12 @@ func TestWatchNewFile(t *testing.T) {
 func TestWatchNoDir(t *testing.T) {
 	t.Parallel()
 
-	// Create am but not the directory that it watches.
+	// Create ks but not the directory that it watches.
 	rand.Seed(time.Now().UnixNano())
 	dir := filepath.Join(os.TempDir(), fmt.Sprintf("eth-keystore-watch-test-%d-%d", os.Getpid(), rand.Int()))
-	am := NewManager(dir, LightScryptN, LightScryptP)
+	ks := NewKeyStore(dir, LightScryptN, LightScryptP)
 
-	list := am.Accounts()
+	list := ks.Accounts()
 	if len(list) > 0 {
 		t.Error("initial account list not empty:", list)
 	}
@@ -100,16 +108,22 @@ func TestWatchNoDir(t *testing.T) {
 	os.MkdirAll(dir, 0700)
 	defer os.RemoveAll(dir)
 	file := filepath.Join(dir, "aaa")
-	if err := cp.CopyFile(file, cachetestAccounts[0].File); err != nil {
+	if err := cp.CopyFile(file, cachetestAccounts[0].URL.Path); err != nil {
 		t.Fatal(err)
 	}
 
-	// am should see the account.
-	wantAccounts := []Account{cachetestAccounts[0]}
-	wantAccounts[0].File = file
+	// ks should see the account.
+	wantAccounts := []accounts.Account{cachetestAccounts[0]}
+	wantAccounts[0].URL = accounts.URL{Scheme: KeyStoreScheme, Path: file}
 	for d := 200 * time.Millisecond; d < 8*time.Second; d *= 2 {
-		list = am.Accounts()
+		list = ks.Accounts()
 		if reflect.DeepEqual(list, wantAccounts) {
+			// ks should have also received change notifications
+			select {
+			case <-ks.changes:
+			default:
+				t.Fatalf("wasn't notified of new accounts")
+			}
 			return
 		}
 		time.Sleep(d)
@@ -118,7 +132,7 @@ func TestWatchNoDir(t *testing.T) {
 }
 
 func TestCacheInitialReload(t *testing.T) {
-	cache := newAddrCache(cachetestDir)
+	cache, _ := newAccountCache(cachetestDir)
 	accounts := cache.accounts()
 	if !reflect.DeepEqual(accounts, cachetestAccounts) {
 		t.Fatalf("got initial accounts: %swant %s", spew.Sdump(accounts), spew.Sdump(cachetestAccounts))
@@ -126,55 +140,55 @@ func TestCacheInitialReload(t *testing.T) {
 }
 
 func TestCacheAddDeleteOrder(t *testing.T) {
-	cache := newAddrCache("testdata/no-such-dir")
+	cache, _ := newAccountCache("testdata/no-such-dir")
 	cache.watcher.running = true // prevent unexpected reloads
 
-	accounts := []Account{
+	accs := []accounts.Account{
 		{
 			Address: common.HexToAddress("095e7baea6a6c7c4c2dfeb977efac326af552d87"),
-			File:    "-309830980",
+			URL:     accounts.URL{Scheme: KeyStoreScheme, Path: "-309830980"},
 		},
 		{
 			Address: common.HexToAddress("2cac1adea150210703ba75ed097ddfe24e14f213"),
-			File:    "ggg",
+			URL:     accounts.URL{Scheme: KeyStoreScheme, Path: "ggg"},
 		},
 		{
 			Address: common.HexToAddress("8bda78331c916a08481428e4b07c96d3e916d165"),
-			File:    "zzzzzz-the-very-last-one.keyXXX",
+			URL:     accounts.URL{Scheme: KeyStoreScheme, Path: "zzzzzz-the-very-last-one.keyXXX"},
 		},
 		{
 			Address: common.HexToAddress("d49ff4eeb0b2686ed89c0fc0f2b6ea533ddbbd5e"),
-			File:    "SOMETHING.key",
+			URL:     accounts.URL{Scheme: KeyStoreScheme, Path: "SOMETHING.key"},
 		},
 		{
 			Address: common.HexToAddress("7ef5a6135f1fd6a02593eedc869c6d41d934aef8"),
-			File:    "UTC--2016-03-22T12-57-55.920751759Z--7ef5a6135f1fd6a02593eedc869c6d41d934aef8",
+			URL:     accounts.URL{Scheme: KeyStoreScheme, Path: "UTC--2016-03-22T12-57-55.920751759Z--7ef5a6135f1fd6a02593eedc869c6d41d934aef8"},
 		},
 		{
 			Address: common.HexToAddress("f466859ead1932d743d622cb74fc058882e8648a"),
-			File:    "aaa",
+			URL:     accounts.URL{Scheme: KeyStoreScheme, Path: "aaa"},
 		},
 		{
 			Address: common.HexToAddress("289d485d9771714cce91d3393d764e1311907acc"),
-			File:    "zzz",
+			URL:     accounts.URL{Scheme: KeyStoreScheme, Path: "zzz"},
 		},
 	}
-	for _, a := range accounts {
+	for _, a := range accs {
 		cache.add(a)
 	}
 	// Add some of them twice to check that they don't get reinserted.
-	cache.add(accounts[0])
-	cache.add(accounts[2])
+	cache.add(accs[0])
+	cache.add(accs[2])
 
 	// Check that the account list is sorted by filename.
-	wantAccounts := make([]Account, len(accounts))
-	copy(wantAccounts, accounts)
-	sort.Sort(accountsByFile(wantAccounts))
+	wantAccounts := make([]accounts.Account, len(accs))
+	copy(wantAccounts, accs)
+	sort.Sort(accountsByURL(wantAccounts))
 	list := cache.accounts()
 	if !reflect.DeepEqual(list, wantAccounts) {
-		t.Fatalf("got accounts: %s\nwant %s", spew.Sdump(accounts), spew.Sdump(wantAccounts))
+		t.Fatalf("got accounts: %s\nwant %s", spew.Sdump(accs), spew.Sdump(wantAccounts))
 	}
-	for _, a := range accounts {
+	for _, a := range accs {
 		if !cache.hasAddress(a.Address) {
 			t.Errorf("expected hasAccount(%x) to return true", a.Address)
 		}
@@ -184,13 +198,13 @@ func TestCacheAddDeleteOrder(t *testing.T) {
 	}
 
 	// Delete a few keys from the cache.
-	for i := 0; i < len(accounts); i += 2 {
+	for i := 0; i < len(accs); i += 2 {
 		cache.delete(wantAccounts[i])
 	}
-	cache.delete(Account{Address: common.HexToAddress("fd9bd350f08ee3c0c19b85a8e16114a11a60aa4e"), File: "something"})
+	cache.delete(accounts.Account{Address: common.HexToAddress("fd9bd350f08ee3c0c19b85a8e16114a11a60aa4e"), URL: accounts.URL{Scheme: KeyStoreScheme, Path: "something"}})
 
 	// Check content again after deletion.
-	wantAccountsAfterDelete := []Account{
+	wantAccountsAfterDelete := []accounts.Account{
 		wantAccounts[1],
 		wantAccounts[3],
 		wantAccounts[5],
@@ -211,63 +225,63 @@ func TestCacheAddDeleteOrder(t *testing.T) {
 
 func TestCacheFind(t *testing.T) {
 	dir := filepath.Join("testdata", "dir")
-	cache := newAddrCache(dir)
+	cache, _ := newAccountCache(dir)
 	cache.watcher.running = true // prevent unexpected reloads
 
-	accounts := []Account{
+	accs := []accounts.Account{
 		{
 			Address: common.HexToAddress("095e7baea6a6c7c4c2dfeb977efac326af552d87"),
-			File:    filepath.Join(dir, "a.key"),
+			URL:     accounts.URL{Scheme: KeyStoreScheme, Path: filepath.Join(dir, "a.key")},
 		},
 		{
 			Address: common.HexToAddress("2cac1adea150210703ba75ed097ddfe24e14f213"),
-			File:    filepath.Join(dir, "b.key"),
+			URL:     accounts.URL{Scheme: KeyStoreScheme, Path: filepath.Join(dir, "b.key")},
 		},
 		{
 			Address: common.HexToAddress("d49ff4eeb0b2686ed89c0fc0f2b6ea533ddbbd5e"),
-			File:    filepath.Join(dir, "c.key"),
+			URL:     accounts.URL{Scheme: KeyStoreScheme, Path: filepath.Join(dir, "c.key")},
 		},
 		{
 			Address: common.HexToAddress("d49ff4eeb0b2686ed89c0fc0f2b6ea533ddbbd5e"),
-			File:    filepath.Join(dir, "c2.key"),
+			URL:     accounts.URL{Scheme: KeyStoreScheme, Path: filepath.Join(dir, "c2.key")},
 		},
 	}
-	for _, a := range accounts {
+	for _, a := range accs {
 		cache.add(a)
 	}
 
-	nomatchAccount := Account{
+	nomatchAccount := accounts.Account{
 		Address: common.HexToAddress("f466859ead1932d743d622cb74fc058882e8648a"),
-		File:    filepath.Join(dir, "something"),
+		URL:     accounts.URL{Scheme: KeyStoreScheme, Path: filepath.Join(dir, "something")},
 	}
 	tests := []struct {
-		Query      Account
-		WantResult Account
+		Query      accounts.Account
+		WantResult accounts.Account
 		WantError  error
 	}{
 		// by address
-		{Query: Account{Address: accounts[0].Address}, WantResult: accounts[0]},
+		{Query: accounts.Account{Address: accs[0].Address}, WantResult: accs[0]},
 		// by file
-		{Query: Account{File: accounts[0].File}, WantResult: accounts[0]},
+		{Query: accounts.Account{URL: accs[0].URL}, WantResult: accs[0]},
 		// by basename
-		{Query: Account{File: filepath.Base(accounts[0].File)}, WantResult: accounts[0]},
+		{Query: accounts.Account{URL: accounts.URL{Scheme: KeyStoreScheme, Path: filepath.Base(accs[0].URL.Path)}}, WantResult: accs[0]},
 		// by file and address
-		{Query: accounts[0], WantResult: accounts[0]},
+		{Query: accs[0], WantResult: accs[0]},
 		// ambiguous address, tie resolved by file
-		{Query: accounts[2], WantResult: accounts[2]},
+		{Query: accs[2], WantResult: accs[2]},
 		// ambiguous address error
 		{
-			Query: Account{Address: accounts[2].Address},
+			Query: accounts.Account{Address: accs[2].Address},
 			WantError: &AmbiguousAddrError{
-				Addr:    accounts[2].Address,
-				Matches: []Account{accounts[2], accounts[3]},
+				Addr:    accs[2].Address,
+				Matches: []accounts.Account{accs[2], accs[3]},
 			},
 		},
 		// no match error
 		{Query: nomatchAccount, WantError: ErrNoMatch},
-		{Query: Account{File: nomatchAccount.File}, WantError: ErrNoMatch},
-		{Query: Account{File: filepath.Base(nomatchAccount.File)}, WantError: ErrNoMatch},
-		{Query: Account{Address: nomatchAccount.Address}, WantError: ErrNoMatch},
+		{Query: accounts.Account{URL: nomatchAccount.URL}, WantError: ErrNoMatch},
+		{Query: accounts.Account{URL: accounts.URL{Scheme: KeyStoreScheme, Path: filepath.Base(nomatchAccount.URL.Path)}}, WantError: ErrNoMatch},
+		{Query: accounts.Account{Address: nomatchAccount.Address}, WantError: ErrNoMatch},
 	}
 	for i, test := range tests {
 		a, err := cache.find(test.Query)
diff --git a/accounts/key.go b/accounts/keystore/key.go
index dbcb49dcf..e2bdf09fe 100644
--- a/accounts/key.go
+++ b/accounts/keystore/key.go
@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU Lesser General Public License
 // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
 
-package accounts
+package keystore
 
 import (
 	"bytes"
@@ -29,6 +29,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/ethereum/go-ethereum/accounts"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/crypto/secp256k1"
@@ -175,13 +176,13 @@ func newKey(rand io.Reader) (*Key, error) {
 	return newKeyFromECDSA(privateKeyECDSA), nil
 }
 
-func storeNewKey(ks keyStore, rand io.Reader, auth string) (*Key, Account, error) {
+func storeNewKey(ks keyStore, rand io.Reader, auth string) (*Key, accounts.Account, error) {
 	key, err := newKey(rand)
 	if err != nil {
-		return nil, Account{}, err
+		return nil, accounts.Account{}, err
 	}
-	a := Account{Address: key.Address, File: ks.JoinPath(keyFileName(key.Address))}
-	if err := ks.StoreKey(a.File, key, auth); err != nil {
+	a := accounts.Account{Address: key.Address, URL: accounts.URL{Scheme: KeyStoreScheme, Path: ks.JoinPath(keyFileName(key.Address))}}
+	if err := ks.StoreKey(a.URL.Path, key, auth); err != nil {
 		zeroKey(key.PrivateKey)
 		return nil, a, err
 	}
diff --git a/accounts/keystore/keystore.go b/accounts/keystore/keystore.go
new file mode 100644
index 000000000..a01ff17e3
--- /dev/null
+++ b/accounts/keystore/keystore.go
@@ -0,0 +1,494 @@
+// Copyright 2015 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+// Package keystore implements encrypted storage of secp256k1 private keys.
+//
+// Keys are stored as encrypted JSON files according to the Web3 Secret Storage specification.
+// See https://github.com/ethereum/wiki/wiki/Web3-Secret-Storage-Definition for more information.
+package keystore
+
+import (
+	"crypto/ecdsa"
+	crand "crypto/rand"
+	"errors"
+	"fmt"
+	"math/big"
+	"os"
+	"path/filepath"
+	"reflect"
+	"runtime"
+	"sync"
+	"time"
+
+	"github.com/ethereum/go-ethereum/accounts"
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/event"
+)
+
+var (
+	ErrLocked  = accounts.NewAuthNeededError("password or unlock")
+	ErrNoMatch = errors.New("no key for given address or file")
+	ErrDecrypt = errors.New("could not decrypt key with given passphrase")
+)
+
+// KeyStoreType is the reflect type of a keystore backend.
+var KeyStoreType = reflect.TypeOf(&KeyStore{})
+
+// KeyStoreScheme is the protocol scheme prefixing account and wallet URLs.
+var KeyStoreScheme = "keystore"
+
+// Maximum time between wallet refreshes (if filesystem notifications don't work).
+const walletRefreshCycle = 3 * time.Second
+
+// KeyStore manages a key storage directory on disk.
+type KeyStore struct {
+	storage  keyStore                     // Storage backend, might be cleartext or encrypted
+	cache    *accountCache                // In-memory account cache over the filesystem storage
+	changes  chan struct{}                // Channel receiving change notifications from the cache
+	unlocked map[common.Address]*unlocked // Currently unlocked account (decrypted private keys)
+
+	wallets     []accounts.Wallet       // Wallet wrappers around the individual key files
+	updateFeed  event.Feed              // Event feed to notify wallet additions/removals
+	updateScope event.SubscriptionScope // Subscription scope tracking current live listeners
+	updating    bool                    // Whether the event notification loop is running
+
+	mu sync.RWMutex
+}
+
+type unlocked struct {
+	*Key
+	abort chan struct{}
+}
+
+// NewKeyStore creates a keystore for the given directory.
+func NewKeyStore(keydir string, scryptN, scryptP int) *KeyStore {
+	keydir, _ = filepath.Abs(keydir)
+	ks := &KeyStore{storage: &keyStorePassphrase{keydir, scryptN, scryptP}}
+	ks.init(keydir)
+	return ks
+}
+
+// NewPlaintextKeyStore creates a keystore for the given directory.
+// Deprecated: Use NewKeyStore.
+func NewPlaintextKeyStore(keydir string) *KeyStore {
+	keydir, _ = filepath.Abs(keydir)
+	ks := &KeyStore{storage: &keyStorePlain{keydir}}
+	ks.init(keydir)
+	return ks
+}
+
+func (ks *KeyStore) init(keydir string) {
+	// Lock the mutex since the account cache might call back with events
+	ks.mu.Lock()
+	defer ks.mu.Unlock()
+
+	// Initialize the set of unlocked keys and the account cache
+	ks.unlocked = make(map[common.Address]*unlocked)
+	ks.cache, ks.changes = newAccountCache(keydir)
+
+	// TODO: In order for this finalizer to work, there must be no references
+	// to ks. addressCache doesn't keep a reference but unlocked keys do,
+	// so the finalizer will not trigger until all timed unlocks have expired.
+	runtime.SetFinalizer(ks, func(m *KeyStore) {
+		m.cache.close()
+	})
+	// Create the initial list of wallets from the cache
+	accs := ks.cache.accounts()
+	ks.wallets = make([]accounts.Wallet, len(accs))
+	for i := 0; i < len(accs); i++ {
+		ks.wallets[i] = &keystoreWallet{account: accs[i], keystore: ks}
+	}
+}
+
+// Wallets implements accounts.Backend, returning all single-key wallets from the
+// keystore directory.
+func (ks *KeyStore) Wallets() []accounts.Wallet {
+	// Make sure the list of wallets is in sync with the account cache
+	ks.refreshWallets()
+
+	ks.mu.RLock()
+	defer ks.mu.RUnlock()
+
+	cpy := make([]accounts.Wallet, len(ks.wallets))
+	copy(cpy, ks.wallets)
+	return cpy
+}
+
+// refreshWallets retrieves the current account list and based on that does any
+// necessary wallet refreshes.
+func (ks *KeyStore) refreshWallets() {
+	// Retrieve the current list of accounts
+	ks.mu.Lock()
+	accs := ks.cache.accounts()
+
+	// Transform the current list of wallets into the new one
+	wallets := make([]accounts.Wallet, 0, len(accs))
+	events := []accounts.WalletEvent{}
+
+	for _, account := range accs {
+		// Drop wallets while they were in front of the next account
+		for len(ks.wallets) > 0 && ks.wallets[0].URL().Cmp(account.URL) < 0 {
+			events = append(events, accounts.WalletEvent{Wallet: ks.wallets[0], Arrive: false})
+			ks.wallets = ks.wallets[1:]
+		}
+		// If there are no more wallets or the account is before the next, wrap new wallet
+		if len(ks.wallets) == 0 || ks.wallets[0].URL().Cmp(account.URL) > 0 {
+			wallet := &keystoreWallet{account: account, keystore: ks}
+
+			events = append(events, accounts.WalletEvent{Wallet: wallet, Arrive: true})
+			wallets = append(wallets, wallet)
+			continue
+		}
+		// If the account is the same as the first wallet, keep it
+		if ks.wallets[0].Accounts()[0] == account {
+			wallets = append(wallets, ks.wallets[0])
+			ks.wallets = ks.wallets[1:]
+			continue
+		}
+	}
+	// Drop any leftover wallets and set the new batch
+	for _, wallet := range ks.wallets {
+		events = append(events, accounts.WalletEvent{Wallet: wallet, Arrive: false})
+	}
+	ks.wallets = wallets
+	ks.mu.Unlock()
+
+	// Fire all wallet events and return
+	for _, event := range events {
+		ks.updateFeed.Send(event)
+	}
+}
+
+// Subscribe implements accounts.Backend, creating an async subscription to
+// receive notifications on the addition or removal of keystore wallets.
+func (ks *KeyStore) Subscribe(sink chan<- accounts.WalletEvent) event.Subscription {
+	// We need the mutex to reliably start/stop the update loop
+	ks.mu.Lock()
+	defer ks.mu.Unlock()
+
+	// Subscribe the caller and track the subscriber count
+	sub := ks.updateScope.Track(ks.updateFeed.Subscribe(sink))
+
+	// Subscribers require an active notification loop, start it
+	if !ks.updating {
+		ks.updating = true
+		go ks.updater()
+	}
+	return sub
+}
+
+// updater is responsible for maintaining an up-to-date list of wallets stored in
+// the keystore, and for firing wallet addition/removal events. It listens for
+// account change events from the underlying account cache, and also periodically
+// forces a manual refresh (only triggers for systems where the filesystem notifier
+// is not running).
+func (ks *KeyStore) updater() {
+	for {
+		// Wait for an account update or a refresh timeout
+		select {
+		case <-ks.changes:
+		case <-time.After(walletRefreshCycle):
+		}
+		// Run the wallet refresher
+		ks.refreshWallets()
+
+		// If all our subscribers left, stop the updater
+		ks.mu.Lock()
+		if ks.updateScope.Count() == 0 {
+			ks.updating = false
+			ks.mu.Unlock()
+			return
+		}
+		ks.mu.Unlock()
+	}
+}
+
+// HasAddress reports whether a key with the given address is present.
+func (ks *KeyStore) HasAddress(addr common.Address) bool {
+	return ks.cache.hasAddress(addr)
+}
+
+// Accounts returns all key files present in the directory.
+func (ks *KeyStore) Accounts() []accounts.Account {
+	return ks.cache.accounts()
+}
+
+// Delete deletes the key matched by account if the passphrase is correct.
+// If the account contains no filename, the address must match a unique key.
+func (ks *KeyStore) Delete(a accounts.Account, passphrase string) error {
+	// Decrypting the key isn't really necessary, but we do
+	// it anyway to check the password and zero out the key
+	// immediately afterwards.
+	a, key, err := ks.getDecryptedKey(a, passphrase)
+	if key != nil {
+		zeroKey(key.PrivateKey)
+	}
+	if err != nil {
+		return err
+	}
+	// The order is crucial here. The key is dropped from the
+	// cache after the file is gone so that a reload happening in
+	// between won't insert it into the cache again.
+	err = os.Remove(a.URL.Path)
+	if err == nil {
+		ks.cache.delete(a)
+		ks.refreshWallets()
+	}
+	return err
+}
+
+// SignHash calculates a ECDSA signature for the given hash. The produced
+// signature is in the [R || S || V] format where V is 0 or 1.
+func (ks *KeyStore) SignHash(a accounts.Account, hash []byte) ([]byte, error) {
+	// Look up the key to sign with and abort if it cannot be found
+	ks.mu.RLock()
+	defer ks.mu.RUnlock()
+
+	unlockedKey, found := ks.unlocked[a.Address]
+	if !found {
+		return nil, ErrLocked
+	}
+	// Sign the hash using plain ECDSA operations
+	return crypto.Sign(hash, unlockedKey.PrivateKey)
+}
+
+// SignTx signs the given transaction with the requested account.
+func (ks *KeyStore) SignTx(a accounts.Account, tx *types.Transaction, chainID *big.Int) (*types.Transaction, error) {
+	// Look up the key to sign with and abort if it cannot be found
+	ks.mu.RLock()
+	defer ks.mu.RUnlock()
+
+	unlockedKey, found := ks.unlocked[a.Address]
+	if !found {
+		return nil, ErrLocked
+	}
+	// Depending on the presence of the chain ID, sign with EIP155 or homestead
+	if chainID != nil {
+		return types.SignTx(tx, types.NewEIP155Signer(chainID), unlockedKey.PrivateKey)
+	}
+	return types.SignTx(tx, types.HomesteadSigner{}, unlockedKey.PrivateKey)
+}
+
+// SignHashWithPassphrase signs hash if the private key matching the given address
+// can be decrypted with the given passphrase. The produced signature is in the
+// [R || S || V] format where V is 0 or 1.
+func (ks *KeyStore) SignHashWithPassphrase(a accounts.Account, passphrase string, hash []byte) (signature []byte, err error) {
+	_, key, err := ks.getDecryptedKey(a, passphrase)
+	if err != nil {
+		return nil, err
+	}
+	defer zeroKey(key.PrivateKey)
+	return crypto.Sign(hash, key.PrivateKey)
+}
+
+// SignTxWithPassphrase signs the transaction if the private key matching the
+// given address can be decrypted with the given passphrase.
+func (ks *KeyStore) SignTxWithPassphrase(a accounts.Account, passphrase string, tx *types.Transaction, chainID *big.Int) (*types.Transaction, error) {
+	_, key, err := ks.getDecryptedKey(a, passphrase)
+	if err != nil {
+		return nil, err
+	}
+	defer zeroKey(key.PrivateKey)
+
+	// Depending on the presence of the chain ID, sign with EIP155 or homestead
+	if chainID != nil {
+		return types.SignTx(tx, types.NewEIP155Signer(chainID), key.PrivateKey)
+	}
+	return types.SignTx(tx, types.HomesteadSigner{}, key.PrivateKey)
+}
+
+// Unlock unlocks the given account indefinitely.
+func (ks *KeyStore) Unlock(a accounts.Account, passphrase string) error {
+	return ks.TimedUnlock(a, passphrase, 0)
+}
+
+// Lock removes the private key with the given address from memory.
+func (ks *KeyStore) Lock(addr common.Address) error {
+	ks.mu.Lock()
+	if unl, found := ks.unlocked[addr]; found {
+		ks.mu.Unlock()
+		ks.expire(addr, unl, time.Duration(0)*time.Nanosecond)
+	} else {
+		ks.mu.Unlock()
+	}
+	return nil
+}
+
+// TimedUnlock unlocks the given account with the passphrase. The account
+// stays unlocked for the duration of timeout. A timeout of 0 unlocks the account
+// until the program exits. The account must match a unique key file.
+//
+// If the account address is already unlocked for a duration, TimedUnlock extends or
+// shortens the active unlock timeout. If the address was previously unlocked
+// indefinitely the timeout is not altered.
+func (ks *KeyStore) TimedUnlock(a accounts.Account, passphrase string, timeout time.Duration) error {
+	a, key, err := ks.getDecryptedKey(a, passphrase)
+	if err != nil {
+		return err
+	}
+
+	ks.mu.Lock()
+	defer ks.mu.Unlock()
+	u, found := ks.unlocked[a.Address]
+	if found {
+		if u.abort == nil {
+			// The address was unlocked indefinitely, so unlocking
+			// it with a timeout would be confusing.
+			zeroKey(key.PrivateKey)
+			return nil
+		}
+		// Terminate the expire goroutine and replace it below.
+		close(u.abort)
+	}
+	if timeout > 0 {
+		u = &unlocked{Key: key, abort: make(chan struct{})}
+		go ks.expire(a.Address, u, timeout)
+	} else {
+		u = &unlocked{Key: key}
+	}
+	ks.unlocked[a.Address] = u
+	return nil
+}
+
+// Find resolves the given account into a unique entry in the keystore.
+func (ks *KeyStore) Find(a accounts.Account) (accounts.Account, error) {
+	ks.cache.maybeReload()
+	ks.cache.mu.Lock()
+	a, err := ks.cache.find(a)
+	ks.cache.mu.Unlock()
+	return a, err
+}
+
+func (ks *KeyStore) getDecryptedKey(a accounts.Account, auth string) (accounts.Account, *Key, error) {
+	a, err := ks.Find(a)
+	if err != nil {
+		return a, nil, err
+	}
+	key, err := ks.storage.GetKey(a.Address, a.URL.Path, auth)
+	return a, key, err
+}
+
+func (ks *KeyStore) expire(addr common.Address, u *unlocked, timeout time.Duration) {
+	t := time.NewTimer(timeout)
+	defer t.Stop()
+	select {
+	case <-u.abort:
+		// just quit
+	case <-t.C:
+		ks.mu.Lock()
+		// only drop if it's still the same key instance that dropLater
+		// was launched with. we can check that using pointer equality
+		// because the map stores a new pointer every time the key is
+		// unlocked.
+		if ks.unlocked[addr] == u {
+			zeroKey(u.PrivateKey)
+			delete(ks.unlocked, addr)
+		}
+		ks.mu.Unlock()
+	}
+}
+
+// NewAccount generates a new key and stores it into the key directory,
+// encrypting it with the passphrase.
+func (ks *KeyStore) NewAccount(passphrase string) (accounts.Account, error) {
+	_, account, err := storeNewKey(ks.storage, crand.Reader, passphrase)
+	if err != nil {
+		return accounts.Account{}, err
+	}
+	// Add the account to the cache immediately rather
+	// than waiting for file system notifications to pick it up.
+	ks.cache.add(account)
+	ks.refreshWallets()
+	return account, nil
+}
+
+// Export exports as a JSON key, encrypted with newPassphrase.
+func (ks *KeyStore) Export(a accounts.Account, passphrase, newPassphrase string) (keyJSON []byte, err error) {
+	_, key, err := ks.getDecryptedKey(a, passphrase)
+	if err != nil {
+		return nil, err
+	}
+	var N, P int
+	if store, ok := ks.storage.(*keyStorePassphrase); ok {
+		N, P = store.scryptN, store.scryptP
+	} else {
+		N, P = StandardScryptN, StandardScryptP
+	}
+	return EncryptKey(key, newPassphrase, N, P)
+}
+
+// Import stores the given encrypted JSON key into the key directory.
+func (ks *KeyStore) Import(keyJSON []byte, passphrase, newPassphrase string) (accounts.Account, error) {
+	key, err := DecryptKey(keyJSON, passphrase)
+	if key != nil && key.PrivateKey != nil {
+		defer zeroKey(key.PrivateKey)
+	}
+	if err != nil {
+		return accounts.Account{}, err
+	}
+	return ks.importKey(key, newPassphrase)
+}
+
+// ImportECDSA stores the given key into the key directory, encrypting it with the passphrase.
+func (ks *KeyStore) ImportECDSA(priv *ecdsa.PrivateKey, passphrase string) (accounts.Account, error) {
+	key := newKeyFromECDSA(priv)
+	if ks.cache.hasAddress(key.Address) {
+		return accounts.Account{}, fmt.Errorf("account already exists")
+	}
+
+	return ks.importKey(key, passphrase)
+}
+
+func (ks *KeyStore) importKey(key *Key, passphrase string) (accounts.Account, error) {
+	a := accounts.Account{Address: key.Address, URL: accounts.URL{Scheme: KeyStoreScheme, Path: ks.storage.JoinPath(keyFileName(key.Address))}}
+	if err := ks.storage.StoreKey(a.URL.Path, key, passphrase); err != nil {
+		return accounts.Account{}, err
+	}
+	ks.cache.add(a)
+	ks.refreshWallets()
+	return a, nil
+}
+
+// Update changes the passphrase of an existing account.
+func (ks *KeyStore) Update(a accounts.Account, passphrase, newPassphrase string) error {
+	a, key, err := ks.getDecryptedKey(a, passphrase)
+	if err != nil {
+		return err
+	}
+	return ks.storage.StoreKey(a.URL.Path, key, newPassphrase)
+}
+
+// ImportPreSaleKey decrypts the given Ethereum presale wallet and stores
+// a key file in the key directory. The key file is encrypted with the same passphrase.
+func (ks *KeyStore) ImportPreSaleKey(keyJSON []byte, passphrase string) (accounts.Account, error) {
+	a, _, err := importPreSaleKey(ks.storage, keyJSON, passphrase)
+	if err != nil {
+		return a, err
+	}
+	ks.cache.add(a)
+	ks.refreshWallets()
+	return a, nil
+}
+
+// zeroKey zeroes a private key in memory.
+func zeroKey(k *ecdsa.PrivateKey) {
+	b := k.D.Bits()
+	for i := range b {
+		b[i] = 0
+	}
+}
diff --git a/accounts/key_store_passphrase.go b/accounts/keystore/keystore_passphrase.go
index 4a777956d..8ef510fcf 100644
--- a/accounts/key_store_passphrase.go
+++ b/accounts/keystore/keystore_passphrase.go
@@ -23,7 +23,7 @@ The crypto is documented at https://github.com/ethereum/wiki/wiki/Web3-Secret-St
 
 */
 
-package accounts
+package keystore
 
 import (
 	"bytes"
diff --git a/accounts/key_store_passphrase_test.go b/accounts/keystore/keystore_passphrase_test.go
index 217393fa5..086addbc1 100644
--- a/accounts/key_store_passphrase_test.go
+++ b/accounts/keystore/keystore_passphrase_test.go
@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU Lesser General Public License
 // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
 
-package accounts
+package keystore
 
 import (
 	"io/ioutil"
diff --git a/accounts/key_store_plain.go b/accounts/keystore/keystore_plain.go
index 2cbaa94df..b490ca72b 100644
--- a/accounts/key_store_plain.go
+++ b/accounts/keystore/keystore_plain.go
@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU Lesser General Public License
 // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
 
-package accounts
+package keystore
 
 import (
 	"encoding/json"
diff --git a/accounts/key_store_test.go b/accounts/keystore/keystore_plain_test.go
index d0713caa0..8c0eb52ea 100644
--- a/accounts/key_store_test.go
+++ b/accounts/keystore/keystore_plain_test.go
@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU Lesser General Public License
 // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
 
-package accounts
+package keystore
 
 import (
 	"crypto/rand"
@@ -30,7 +30,7 @@ import (
 	"github.com/ethereum/go-ethereum/crypto"
 )
 
-func tmpKeyStore(t *testing.T, encrypted bool) (dir string, ks keyStore) {
+func tmpKeyStoreIface(t *testing.T, encrypted bool) (dir string, ks keyStore) {
 	d, err := ioutil.TempDir("", "geth-keystore-test")
 	if err != nil {
 		t.Fatal(err)
@@ -44,7 +44,7 @@ func tmpKeyStore(t *testing.T, encrypted bool) (dir string, ks keyStore) {
 }
 
 func TestKeyStorePlain(t *testing.T) {
-	dir, ks := tmpKeyStore(t, false)
+	dir, ks := tmpKeyStoreIface(t, false)
 	defer os.RemoveAll(dir)
 
 	pass := "" // not used but required by API
@@ -52,7 +52,7 @@ func TestKeyStorePlain(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	k2, err := ks.GetKey(k1.Address, account.File, pass)
+	k2, err := ks.GetKey(k1.Address, account.URL.Path, pass)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -65,7 +65,7 @@ func TestKeyStorePlain(t *testing.T) {
 }
 
 func TestKeyStorePassphrase(t *testing.T) {
-	dir, ks := tmpKeyStore(t, true)
+	dir, ks := tmpKeyStoreIface(t, true)
 	defer os.RemoveAll(dir)
 
 	pass := "foo"
@@ -73,7 +73,7 @@ func TestKeyStorePassphrase(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	k2, err := ks.GetKey(k1.Address, account.File, pass)
+	k2, err := ks.GetKey(k1.Address, account.URL.Path, pass)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -86,7 +86,7 @@ func TestKeyStorePassphrase(t *testing.T) {
 }
 
 func TestKeyStorePassphraseDecryptionFail(t *testing.T) {
-	dir, ks := tmpKeyStore(t, true)
+	dir, ks := tmpKeyStoreIface(t, true)
 	defer os.RemoveAll(dir)
 
 	pass := "foo"
@@ -94,13 +94,13 @@ func TestKeyStorePassphraseDecryptionFail(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	if _, err = ks.GetKey(k1.Address, account.File, "bar"); err != ErrDecrypt {
+	if _, err = ks.GetKey(k1.Address, account.URL.Path, "bar"); err != ErrDecrypt {
 		t.Fatalf("wrong error for invalid passphrase\ngot %q\nwant %q", err, ErrDecrypt)
 	}
 }
 
 func TestImportPreSaleKey(t *testing.T) {
-	dir, ks := tmpKeyStore(t, true)
+	dir, ks := tmpKeyStoreIface(t, true)
 	defer os.RemoveAll(dir)
 
 	// file content of a presale key file generated with:
@@ -115,8 +115,8 @@ func TestImportPreSaleKey(t *testing.T) {
 	if account.Address != common.HexToAddress("d4584b5f6229b7be90727b0fc8c6b91bb427821f") {
 		t.Errorf("imported account has wrong address %x", account.Address)
 	}
-	if !strings.HasPrefix(account.File, dir) {
-		t.Errorf("imported account file not in keystore directory: %q", account.File)
+	if !strings.HasPrefix(account.URL.Path, dir) {
+		t.Errorf("imported account file not in keystore directory: %q", account.URL)
 	}
 }
 
@@ -142,19 +142,19 @@ func TestV3_PBKDF2_1(t *testing.T) {
 
 func TestV3_PBKDF2_2(t *testing.T) {
 	t.Parallel()
-	tests := loadKeyStoreTestV3("../tests/files/KeyStoreTests/basic_tests.json", t)
+	tests := loadKeyStoreTestV3("../../tests/files/KeyStoreTests/basic_tests.json", t)
 	testDecryptV3(tests["test1"], t)
 }
 
 func TestV3_PBKDF2_3(t *testing.T) {
 	t.Parallel()
-	tests := loadKeyStoreTestV3("../tests/files/KeyStoreTests/basic_tests.json", t)
+	tests := loadKeyStoreTestV3("../../tests/files/KeyStoreTests/basic_tests.json", t)
 	testDecryptV3(tests["python_generated_test_with_odd_iv"], t)
 }
 
 func TestV3_PBKDF2_4(t *testing.T) {
 	t.Parallel()
-	tests := loadKeyStoreTestV3("../tests/files/KeyStoreTests/basic_tests.json", t)
+	tests := loadKeyStoreTestV3("../../tests/files/KeyStoreTests/basic_tests.json", t)
 	testDecryptV3(tests["evilnonce"], t)
 }
 
@@ -166,7 +166,7 @@ func TestV3_Scrypt_1(t *testing.T) {
 
 func TestV3_Scrypt_2(t *testing.T) {
 	t.Parallel()
-	tests := loadKeyStoreTestV3("../tests/files/KeyStoreTests/basic_tests.json", t)
+	tests := loadKeyStoreTestV3("../../tests/files/KeyStoreTests/basic_tests.json", t)
 	testDecryptV3(tests["test2"], t)
 }
 
diff --git a/accounts/keystore/keystore_test.go b/accounts/keystore/keystore_test.go
new file mode 100644
index 000000000..60f2606ee
--- /dev/null
+++ b/accounts/keystore/keystore_test.go
@@ -0,0 +1,365 @@
+// Copyright 2015 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package keystore
+
+import (
+	"io/ioutil"
+	"math/rand"
+	"os"
+	"runtime"
+	"sort"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/ethereum/go-ethereum/accounts"
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/event"
+)
+
+var testSigData = make([]byte, 32)
+
+func TestKeyStore(t *testing.T) {
+	dir, ks := tmpKeyStore(t, true)
+	defer os.RemoveAll(dir)
+
+	a, err := ks.NewAccount("foo")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !strings.HasPrefix(a.URL.Path, dir) {
+		t.Errorf("account file %s doesn't have dir prefix", a.URL)
+	}
+	stat, err := os.Stat(a.URL.Path)
+	if err != nil {
+		t.Fatalf("account file %s doesn't exist (%v)", a.URL, err)
+	}
+	if runtime.GOOS != "windows" && stat.Mode() != 0600 {
+		t.Fatalf("account file has wrong mode: got %o, want %o", stat.Mode(), 0600)
+	}
+	if !ks.HasAddress(a.Address) {
+		t.Errorf("HasAccount(%x) should've returned true", a.Address)
+	}
+	if err := ks.Update(a, "foo", "bar"); err != nil {
+		t.Errorf("Update error: %v", err)
+	}
+	if err := ks.Delete(a, "bar"); err != nil {
+		t.Errorf("Delete error: %v", err)
+	}
+	if common.FileExist(a.URL.Path) {
+		t.Errorf("account file %s should be gone after Delete", a.URL)
+	}
+	if ks.HasAddress(a.Address) {
+		t.Errorf("HasAccount(%x) should've returned true after Delete", a.Address)
+	}
+}
+
+func TestSign(t *testing.T) {
+	dir, ks := tmpKeyStore(t, true)
+	defer os.RemoveAll(dir)
+
+	pass := "" // not used but required by API
+	a1, err := ks.NewAccount(pass)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := ks.Unlock(a1, ""); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := ks.SignHash(accounts.Account{Address: a1.Address}, testSigData); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestSignWithPassphrase(t *testing.T) {
+	dir, ks := tmpKeyStore(t, true)
+	defer os.RemoveAll(dir)
+
+	pass := "passwd"
+	acc, err := ks.NewAccount(pass)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if _, unlocked := ks.unlocked[acc.Address]; unlocked {
+		t.Fatal("expected account to be locked")
+	}
+
+	_, err = ks.SignHashWithPassphrase(acc, pass, testSigData)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if _, unlocked := ks.unlocked[acc.Address]; unlocked {
+		t.Fatal("expected account to be locked")
+	}
+
+	if _, err = ks.SignHashWithPassphrase(acc, "invalid passwd", testSigData); err == nil {
+		t.Fatal("expected SignHashWithPassphrase to fail with invalid password")
+	}
+}
+
+func TestTimedUnlock(t *testing.T) {
+	dir, ks := tmpKeyStore(t, true)
+	defer os.RemoveAll(dir)
+
+	pass := "foo"
+	a1, err := ks.NewAccount(pass)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Signing without passphrase fails because account is locked
+	_, err = ks.SignHash(accounts.Account{Address: a1.Address}, testSigData)
+	if err != ErrLocked {
+		t.Fatal("Signing should've failed with ErrLocked before unlocking, got ", err)
+	}
+
+	// Signing with passphrase works
+	if err = ks.TimedUnlock(a1, pass, 100*time.Millisecond); err != nil {
+		t.Fatal(err)
+	}
+
+	// Signing without passphrase works because account is temp unlocked
+	_, err = ks.SignHash(accounts.Account{Address: a1.Address}, testSigData)
+	if err != nil {
+		t.Fatal("Signing shouldn't return an error after unlocking, got ", err)
+	}
+
+	// Signing fails again after automatic locking
+	time.Sleep(250 * time.Millisecond)
+	_, err = ks.SignHash(accounts.Account{Address: a1.Address}, testSigData)
+	if err != ErrLocked {
+		t.Fatal("Signing should've failed with ErrLocked timeout expired, got ", err)
+	}
+}
+
+func TestOverrideUnlock(t *testing.T) {
+	dir, ks := tmpKeyStore(t, false)
+	defer os.RemoveAll(dir)
+
+	pass := "foo"
+	a1, err := ks.NewAccount(pass)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Unlock indefinitely.
+	if err = ks.TimedUnlock(a1, pass, 5*time.Minute); err != nil {
+		t.Fatal(err)
+	}
+
+	// Signing without passphrase works because account is temp unlocked
+	_, err = ks.SignHash(accounts.Account{Address: a1.Address}, testSigData)
+	if err != nil {
+		t.Fatal("Signing shouldn't return an error after unlocking, got ", err)
+	}
+
+	// reset unlock to a shorter period, invalidates the previous unlock
+	if err = ks.TimedUnlock(a1, pass, 100*time.Millisecond); err != nil {
+		t.Fatal(err)
+	}
+
+	// Signing without passphrase still works because account is temp unlocked
+	_, err = ks.SignHash(accounts.Account{Address: a1.Address}, testSigData)
+	if err != nil {
+		t.Fatal("Signing shouldn't return an error after unlocking, got ", err)
+	}
+
+	// Signing fails again after automatic locking
+	time.Sleep(250 * time.Millisecond)
+	_, err = ks.SignHash(accounts.Account{Address: a1.Address}, testSigData)
+	if err != ErrLocked {
+		t.Fatal("Signing should've failed with ErrLocked timeout expired, got ", err)
+	}
+}
+
+// This test should fail under -race if signing races the expiration goroutine.
+func TestSignRace(t *testing.T) {
+	dir, ks := tmpKeyStore(t, false)
+	defer os.RemoveAll(dir)
+
+	// Create a test account.
+	a1, err := ks.NewAccount("")
+	if err != nil {
+		t.Fatal("could not create the test account", err)
+	}
+
+	if err := ks.TimedUnlock(a1, "", 15*time.Millisecond); err != nil {
+		t.Fatal("could not unlock the test account", err)
+	}
+	end := time.Now().Add(500 * time.Millisecond)
+	for time.Now().Before(end) {
+		if _, err := ks.SignHash(accounts.Account{Address: a1.Address}, testSigData); err == ErrLocked {
+			return
+		} else if err != nil {
+			t.Errorf("Sign error: %v", err)
+			return
+		}
+		time.Sleep(1 * time.Millisecond)
+	}
+	t.Errorf("Account did not lock within the timeout")
+}
+
+// Tests that the wallet notifier loop starts and stops correctly based on the
+// addition and removal of wallet event subscriptions.
+func TestWalletNotifierLifecycle(t *testing.T) {
+	// Create a temporary kesytore to test with
+	dir, ks := tmpKeyStore(t, false)
+	defer os.RemoveAll(dir)
+
+	// Ensure that the notification updater is not running yet
+	time.Sleep(250 * time.Millisecond)
+	ks.mu.RLock()
+	updating := ks.updating
+	ks.mu.RUnlock()
+
+	if updating {
+		t.Errorf("wallet notifier running without subscribers")
+	}
+	// Subscribe to the wallet feed and ensure the updater boots up
+	updates := make(chan accounts.WalletEvent)
+
+	subs := make([]event.Subscription, 2)
+	for i := 0; i < len(subs); i++ {
+		// Create a new subscription
+		subs[i] = ks.Subscribe(updates)
+
+		// Ensure the notifier comes online
+		time.Sleep(250 * time.Millisecond)
+		ks.mu.RLock()
+		updating = ks.updating
+		ks.mu.RUnlock()
+
+		if !updating {
+			t.Errorf("sub %d: wallet notifier not running after subscription", i)
+		}
+	}
+	// Unsubscribe and ensure the updater terminates eventually
+	for i := 0; i < len(subs); i++ {
+		// Close an existing subscription
+		subs[i].Unsubscribe()
+
+		// Ensure the notifier shuts down at and only at the last close
+		for k := 0; k < int(walletRefreshCycle/(250*time.Millisecond))+2; k++ {
+			ks.mu.RLock()
+			updating = ks.updating
+			ks.mu.RUnlock()
+
+			if i < len(subs)-1 && !updating {
+				t.Fatalf("sub %d: event notifier stopped prematurely", i)
+			}
+			if i == len(subs)-1 && !updating {
+				return
+			}
+			time.Sleep(250 * time.Millisecond)
+		}
+	}
+	t.Errorf("wallet notifier didn't terminate after unsubscribe")
+}
+
+// Tests that wallet notifications and correctly fired when accounts are added
+// or deleted from the keystore.
+func TestWalletNotifications(t *testing.T) {
+	// Create a temporary kesytore to test with
+	dir, ks := tmpKeyStore(t, false)
+	defer os.RemoveAll(dir)
+
+	// Subscribe to the wallet feed
+	updates := make(chan accounts.WalletEvent, 1)
+	sub := ks.Subscribe(updates)
+	defer sub.Unsubscribe()
+
+	// Randomly add and remove account and make sure events and wallets are in sync
+	live := make(map[common.Address]accounts.Account)
+	for i := 0; i < 1024; i++ {
+		// Execute a creation or deletion and ensure event arrival
+		if create := len(live) == 0 || rand.Int()%4 > 0; create {
+			// Add a new account and ensure wallet notifications arrives
+			account, err := ks.NewAccount("")
+			if err != nil {
+				t.Fatalf("failed to create test account: %v", err)
+			}
+			select {
+			case event := <-updates:
+				if !event.Arrive {
+					t.Errorf("departure event on account creation")
+				}
+				if event.Wallet.Accounts()[0] != account {
+					t.Errorf("account mismatch on created wallet: have %v, want %v", event.Wallet.Accounts()[0], account)
+				}
+			default:
+				t.Errorf("wallet arrival event not fired on account creation")
+			}
+			live[account.Address] = account
+		} else {
+			// Select a random account to delete (crude, but works)
+			var account accounts.Account
+			for _, a := range live {
+				account = a
+				break
+			}
+			// Remove an account and ensure wallet notifiaction arrives
+			if err := ks.Delete(account, ""); err != nil {
+				t.Fatalf("failed to delete test account: %v", err)
+			}
+			select {
+			case event := <-updates:
+				if event.Arrive {
+					t.Errorf("arrival event on account deletion")
+				}
+				if event.Wallet.Accounts()[0] != account {
+					t.Errorf("account mismatch on deleted wallet: have %v, want %v", event.Wallet.Accounts()[0], account)
+				}
+			default:
+				t.Errorf("wallet departure event not fired on account creation")
+			}
+			delete(live, account.Address)
+		}
+		// Retrieve the list of wallets and ensure it matches with our required live set
+		liveList := make([]accounts.Account, 0, len(live))
+		for _, account := range live {
+			liveList = append(liveList, account)
+		}
+		sort.Sort(accountsByURL(liveList))
+
+		wallets := ks.Wallets()
+		if len(liveList) != len(wallets) {
+			t.Errorf("wallet list doesn't match required accounts: have %v, want %v", wallets, liveList)
+		} else {
+			for j, wallet := range wallets {
+				if accs := wallet.Accounts(); len(accs) != 1 {
+					t.Errorf("wallet %d: contains invalid number of accounts: have %d, want 1", j, len(accs))
+				} else if accs[0] != liveList[j] {
+					t.Errorf("wallet %d: account mismatch: have %v, want %v", j, accs[0], liveList[j])
+				}
+			}
+		}
+	}
+}
+
+func tmpKeyStore(t *testing.T, encrypted bool) (string, *KeyStore) {
+	d, err := ioutil.TempDir("", "eth-keystore-test")
+	if err != nil {
+		t.Fatal(err)
+	}
+	new := NewPlaintextKeyStore
+	if encrypted {
+		new = func(kd string) *KeyStore { return NewKeyStore(kd, veryLightScryptN, veryLightScryptP) }
+	}
+	return d, new(d)
+}
diff --git a/accounts/keystore/keystore_wallet.go b/accounts/keystore/keystore_wallet.go
new file mode 100644
index 000000000..7165d2821
--- /dev/null
+++ b/accounts/keystore/keystore_wallet.go
@@ -0,0 +1,139 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package keystore
+
+import (
+	"math/big"
+
+	ethereum "github.com/ethereum/go-ethereum"
+	"github.com/ethereum/go-ethereum/accounts"
+	"github.com/ethereum/go-ethereum/core/types"
+)
+
+// keystoreWallet implements the accounts.Wallet interface for the original
+// keystore.
+type keystoreWallet struct {
+	account  accounts.Account // Single account contained in this wallet
+	keystore *KeyStore        // Keystore where the account originates from
+}
+
+// URL implements accounts.Wallet, returning the URL of the account within.
+func (w *keystoreWallet) URL() accounts.URL {
+	return w.account.URL
+}
+
+// Status implements accounts.Wallet, always returning "open", since there is no
+// concept of open/close for plain keystore accounts.
+func (w *keystoreWallet) Status() string {
+	w.keystore.mu.RLock()
+	defer w.keystore.mu.RUnlock()
+
+	if _, ok := w.keystore.unlocked[w.account.Address]; ok {
+		return "Unlocked"
+	}
+	return "Locked"
+}
+
+// Open implements accounts.Wallet, but is a noop for plain wallets since there
+// is no connection or decryption step necessary to access the list of accounts.
+func (w *keystoreWallet) Open(passphrase string) error { return nil }
+
+// Close implements accounts.Wallet, but is a noop for plain wallets since is no
+// meaningful open operation.
+func (w *keystoreWallet) Close() error { return nil }
+
+// Accounts implements accounts.Wallet, returning an account list consisting of
+// a single account that the plain kestore wallet contains.
+func (w *keystoreWallet) Accounts() []accounts.Account {
+	return []accounts.Account{w.account}
+}
+
+// Contains implements accounts.Wallet, returning whether a particular account is
+// or is not wrapped by this wallet instance.
+func (w *keystoreWallet) Contains(account accounts.Account) bool {
+	return account.Address == w.account.Address && (account.URL == (accounts.URL{}) || account.URL == w.account.URL)
+}
+
+// Derive implements accounts.Wallet, but is a noop for plain wallets since there
+// is no notion of hierarchical account derivation for plain keystore accounts.
+func (w *keystoreWallet) Derive(path accounts.DerivationPath, pin bool) (accounts.Account, error) {
+	return accounts.Account{}, accounts.ErrNotSupported
+}
+
+// SelfDerive implements accounts.Wallet, but is a noop for plain wallets since
+// there is no notion of hierarchical account derivation for plain keystore accounts.
+func (w *keystoreWallet) SelfDerive(base accounts.DerivationPath, chain ethereum.ChainStateReader) {}
+
+// SignHash implements accounts.Wallet, attempting to sign the given hash with
+// the given account. If the wallet does not wrap this particular account, an
+// error is returned to avoid account leakage (even though in theory we may be
+// able to sign via our shared keystore backend).
+func (w *keystoreWallet) SignHash(account accounts.Account, hash []byte) ([]byte, error) {
+	// Make sure the requested account is contained within
+	if account.Address != w.account.Address {
+		return nil, accounts.ErrUnknownAccount
+	}
+	if account.URL != (accounts.URL{}) && account.URL != w.account.URL {
+		return nil, accounts.ErrUnknownAccount
+	}
+	// Account seems valid, request the keystore to sign
+	return w.keystore.SignHash(account, hash)
+}
+
+// SignTx implements accounts.Wallet, attempting to sign the given transaction
+// with the given account. If the wallet does not wrap this particular account,
+// an error is returned to avoid account leakage (even though in theory we may
+// be able to sign via our shared keystore backend).
+func (w *keystoreWallet) SignTx(account accounts.Account, tx *types.Transaction, chainID *big.Int) (*types.Transaction, error) {
+	// Make sure the requested account is contained within
+	if account.Address != w.account.Address {
+		return nil, accounts.ErrUnknownAccount
+	}
+	if account.URL != (accounts.URL{}) && account.URL != w.account.URL {
+		return nil, accounts.ErrUnknownAccount
+	}
+	// Account seems valid, request the keystore to sign
+	return w.keystore.SignTx(account, tx, chainID)
+}
+
+// SignHashWithPassphrase implements accounts.Wallet, attempting to sign the
+// given hash with the given account using passphrase as extra authentication.
+func (w *keystoreWallet) SignHashWithPassphrase(account accounts.Account, passphrase string, hash []byte) ([]byte, error) {
+	// Make sure the requested account is contained within
+	if account.Address != w.account.Address {
+		return nil, accounts.ErrUnknownAccount
+	}
+	if account.URL != (accounts.URL{}) && account.URL != w.account.URL {
+		return nil, accounts.ErrUnknownAccount
+	}
+	// Account seems valid, request the keystore to sign
+	return w.keystore.SignHashWithPassphrase(account, passphrase, hash)
+}
+
+// SignTxWithPassphrase implements accounts.Wallet, attempting to sign the given
+// transaction with the given account using passphrase as extra authentication.
+func (w *keystoreWallet) SignTxWithPassphrase(account accounts.Account, passphrase string, tx *types.Transaction, chainID *big.Int) (*types.Transaction, error) {
+	// Make sure the requested account is contained within
+	if account.Address != w.account.Address {
+		return nil, accounts.ErrUnknownAccount
+	}
+	if account.URL != (accounts.URL{}) && account.URL != w.account.URL {
+		return nil, accounts.ErrUnknownAccount
+	}
+	// Account seems valid, request the keystore to sign
+	return w.keystore.SignTxWithPassphrase(account, passphrase, tx, chainID)
+}
diff --git a/accounts/presale.go b/accounts/keystore/presale.go
index f00b4f502..5b883c45f 100644
--- a/accounts/presale.go
+++ b/accounts/keystore/presale.go
@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU Lesser General Public License
 // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
 
-package accounts
+package keystore
 
 import (
 	"crypto/aes"
@@ -25,20 +25,21 @@ import (
 	"errors"
 	"fmt"
 
+	"github.com/ethereum/go-ethereum/accounts"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/pborman/uuid"
 	"golang.org/x/crypto/pbkdf2"
 )
 
 // creates a Key and stores that in the given KeyStore by decrypting a presale key JSON
-func importPreSaleKey(keyStore keyStore, keyJSON []byte, password string) (Account, *Key, error) {
+func importPreSaleKey(keyStore keyStore, keyJSON []byte, password string) (accounts.Account, *Key, error) {
 	key, err := decryptPreSaleKey(keyJSON, password)
 	if err != nil {
-		return Account{}, nil, err
+		return accounts.Account{}, nil, err
 	}
 	key.Id = uuid.NewRandom()
-	a := Account{Address: key.Address, File: keyStore.JoinPath(keyFileName(key.Address))}
-	err = keyStore.StoreKey(a.File, key, password)
+	a := accounts.Account{Address: key.Address, URL: accounts.URL{Scheme: KeyStoreScheme, Path: keyStore.JoinPath(keyFileName(key.Address))}}
+	err = keyStore.StoreKey(a.URL.Path, key, password)
 	return a, key, err
 }
 
diff --git a/accounts/testdata/dupes/1 b/accounts/keystore/testdata/dupes/1
index a3868ec6d..a3868ec6d 100644
--- a/accounts/testdata/dupes/1
+++ b/accounts/keystore/testdata/dupes/1
diff --git a/accounts/testdata/dupes/2 b/accounts/keystore/testdata/dupes/2
index a3868ec6d..a3868ec6d 100644
--- a/accounts/testdata/dupes/2
+++ b/accounts/keystore/testdata/dupes/2
diff --git a/accounts/testdata/dupes/foo b/accounts/keystore/testdata/dupes/foo
index c57060aea..c57060aea 100644
--- a/accounts/testdata/dupes/foo
+++ b/accounts/keystore/testdata/dupes/foo
diff --git a/accounts/testdata/keystore/.hiddenfile b/accounts/keystore/testdata/keystore/.hiddenfile
index d91faccde..d91faccde 100644
--- a/accounts/testdata/keystore/.hiddenfile
+++ b/accounts/keystore/testdata/keystore/.hiddenfile
diff --git a/accounts/testdata/keystore/README b/accounts/keystore/testdata/keystore/README
index a5a86f964..a5a86f964 100644
--- a/accounts/testdata/keystore/README
+++ b/accounts/keystore/testdata/keystore/README
diff --git a/accounts/testdata/keystore/UTC--2016-03-22T12-57-55.920751759Z--7ef5a6135f1fd6a02593eedc869c6d41d934aef8 b/accounts/keystore/testdata/keystore/UTC--2016-03-22T12-57-55.920751759Z--7ef5a6135f1fd6a02593eedc869c6d41d934aef8
index c57060aea..c57060aea 100644
--- a/accounts/testdata/keystore/UTC--2016-03-22T12-57-55.920751759Z--7ef5a6135f1fd6a02593eedc869c6d41d934aef8
+++ b/accounts/keystore/testdata/keystore/UTC--2016-03-22T12-57-55.920751759Z--7ef5a6135f1fd6a02593eedc869c6d41d934aef8
diff --git a/accounts/testdata/keystore/aaa b/accounts/keystore/testdata/keystore/aaa
index a3868ec6d..a3868ec6d 100644
--- a/accounts/testdata/keystore/aaa
+++ b/accounts/keystore/testdata/keystore/aaa
diff --git a/accounts/testdata/keystore/empty b/accounts/keystore/testdata/keystore/empty
index e69de29bb..e69de29bb 100644
--- a/accounts/testdata/keystore/empty
+++ b/accounts/keystore/testdata/keystore/empty
diff --git a/accounts/testdata/keystore/foo/fd9bd350f08ee3c0c19b85a8e16114a11a60aa4e b/accounts/keystore/testdata/keystore/foo/fd9bd350f08ee3c0c19b85a8e16114a11a60aa4e
index 309841e52..309841e52 100644
--- a/accounts/testdata/keystore/foo/fd9bd350f08ee3c0c19b85a8e16114a11a60aa4e
+++ b/accounts/keystore/testdata/keystore/foo/fd9bd350f08ee3c0c19b85a8e16114a11a60aa4e
diff --git a/accounts/testdata/keystore/garbage b/accounts/keystore/testdata/keystore/garbage
index ff45091e7..ff45091e7 100644
--- a/accounts/testdata/keystore/garbage
+++ b/accounts/keystore/testdata/keystore/garbage
diff --git a/accounts/testdata/keystore/no-address b/accounts/keystore/testdata/keystore/no-address
index ad51269ea..ad51269ea 100644
--- a/accounts/testdata/keystore/no-address
+++ b/accounts/keystore/testdata/keystore/no-address
diff --git a/accounts/testdata/keystore/zero b/accounts/keystore/testdata/keystore/zero
index b52617f8a..b52617f8a 100644
--- a/accounts/testdata/keystore/zero
+++ b/accounts/keystore/testdata/keystore/zero
diff --git a/accounts/testdata/keystore/zzz b/accounts/keystore/testdata/keystore/zzz
index cfd8a4701..cfd8a4701 100644
--- a/accounts/testdata/keystore/zzz
+++ b/accounts/keystore/testdata/keystore/zzz
diff --git a/accounts/testdata/v1/cb61d5a9c4896fb9658090b597ef0e7be6f7b67e/cb61d5a9c4896fb9658090b597ef0e7be6f7b67e b/accounts/keystore/testdata/v1/cb61d5a9c4896fb9658090b597ef0e7be6f7b67e/cb61d5a9c4896fb9658090b597ef0e7be6f7b67e
index 498d8131e..498d8131e 100644
--- a/accounts/testdata/v1/cb61d5a9c4896fb9658090b597ef0e7be6f7b67e/cb61d5a9c4896fb9658090b597ef0e7be6f7b67e
+++ b/accounts/keystore/testdata/v1/cb61d5a9c4896fb9658090b597ef0e7be6f7b67e/cb61d5a9c4896fb9658090b597ef0e7be6f7b67e
diff --git a/accounts/testdata/v1_test_vector.json b/accounts/keystore/testdata/v1_test_vector.json
index 3d09b55b5..3d09b55b5 100644
--- a/accounts/testdata/v1_test_vector.json
+++ b/accounts/keystore/testdata/v1_test_vector.json
diff --git a/accounts/testdata/v3_test_vector.json b/accounts/keystore/testdata/v3_test_vector.json
index 1e7f790c0..1e7f790c0 100644
--- a/accounts/testdata/v3_test_vector.json
+++ b/accounts/keystore/testdata/v3_test_vector.json
diff --git a/accounts/testdata/very-light-scrypt.json b/accounts/keystore/testdata/very-light-scrypt.json
index d23b9b2b9..d23b9b2b9 100644
--- a/accounts/testdata/very-light-scrypt.json
+++ b/accounts/keystore/testdata/very-light-scrypt.json
diff --git a/accounts/watch.go b/accounts/keystore/watch.go
index 472be2df7..0b4401255 100644
--- a/accounts/watch.go
+++ b/accounts/keystore/watch.go
@@ -16,7 +16,7 @@
 
 // +build darwin,!ios freebsd linux,!arm64 netbsd solaris
 
-package accounts
+package keystore
 
 import (
 	"time"
@@ -27,14 +27,14 @@ import (
 )
 
 type watcher struct {
-	ac       *addrCache
+	ac       *accountCache
 	starting bool
 	running  bool
 	ev       chan notify.EventInfo
 	quit     chan struct{}
 }
 
-func newWatcher(ac *addrCache) *watcher {
+func newWatcher(ac *accountCache) *watcher {
 	return &watcher{
 		ac:   ac,
 		ev:   make(chan notify.EventInfo, 10),
diff --git a/accounts/watch_fallback.go b/accounts/keystore/watch_fallback.go
index bf971cb1b..7c5e9cb2e 100644
--- a/accounts/watch_fallback.go
+++ b/accounts/keystore/watch_fallback.go
@@ -19,10 +19,10 @@
 // This is the fallback implementation of directory watching.
 // It is used on unsupported platforms.
 
-package accounts
+package keystore
 
 type watcher struct{ running bool }
 
-func newWatcher(*addrCache) *watcher { return new(watcher) }
-func (*watcher) start()              {}
-func (*watcher) close()              {}
+func newWatcher(*accountCache) *watcher { return new(watcher) }
+func (*watcher) start()                 {}
+func (*watcher) close()                 {}
diff --git a/accounts/manager.go b/accounts/manager.go
new file mode 100644
index 000000000..12a5bfcd9
--- /dev/null
+++ b/accounts/manager.go
@@ -0,0 +1,198 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package accounts
+
+import (
+	"reflect"
+	"sort"
+	"sync"
+
+	"github.com/ethereum/go-ethereum/event"
+)
+
+// Manager is an overarching account manager that can communicate with various
+// backends for signing transactions.
+type Manager struct {
+	backends map[reflect.Type][]Backend // Index of backends currently registered
+	updaters []event.Subscription       // Wallet update subscriptions for all backends
+	updates  chan WalletEvent           // Subscription sink for backend wallet changes
+	wallets  []Wallet                   // Cache of all wallets from all registered backends
+
+	feed event.Feed // Wallet feed notifying of arrivals/departures
+
+	quit chan chan error
+	lock sync.RWMutex
+}
+
+// NewManager creates a generic account manager to sign transaction via various
+// supported backends.
+func NewManager(backends ...Backend) *Manager {
+	// Subscribe to wallet notifications from all backends
+	updates := make(chan WalletEvent, 4*len(backends))
+
+	subs := make([]event.Subscription, len(backends))
+	for i, backend := range backends {
+		subs[i] = backend.Subscribe(updates)
+	}
+	// Retrieve the initial list of wallets from the backends and sort by URL
+	var wallets []Wallet
+	for _, backend := range backends {
+		wallets = merge(wallets, backend.Wallets()...)
+	}
+	// Assemble the account manager and return
+	am := &Manager{
+		backends: make(map[reflect.Type][]Backend),
+		updaters: subs,
+		updates:  updates,
+		wallets:  wallets,
+		quit:     make(chan chan error),
+	}
+	for _, backend := range backends {
+		kind := reflect.TypeOf(backend)
+		am.backends[kind] = append(am.backends[kind], backend)
+	}
+	go am.update()
+
+	return am
+}
+
+// Close terminates the account manager's internal notification processes.
+func (am *Manager) Close() error {
+	errc := make(chan error)
+	am.quit <- errc
+	return <-errc
+}
+
+// update is the wallet event loop listening for notifications from the backends
+// and updating the cache of wallets.
+func (am *Manager) update() {
+	// Close all subscriptions when the manager terminates
+	defer func() {
+		am.lock.Lock()
+		for _, sub := range am.updaters {
+			sub.Unsubscribe()
+		}
+		am.updaters = nil
+		am.lock.Unlock()
+	}()
+
+	// Loop until termination
+	for {
+		select {
+		case event := <-am.updates:
+			// Wallet event arrived, update local cache
+			am.lock.Lock()
+			if event.Arrive {
+				am.wallets = merge(am.wallets, event.Wallet)
+			} else {
+				am.wallets = drop(am.wallets, event.Wallet)
+			}
+			am.lock.Unlock()
+
+			// Notify any listeners of the event
+			am.feed.Send(event)
+
+		case errc := <-am.quit:
+			// Manager terminating, return
+			errc <- nil
+			return
+		}
+	}
+}
+
+// Backends retrieves the backend(s) with the given type from the account manager.
+func (am *Manager) Backends(kind reflect.Type) []Backend {
+	return am.backends[kind]
+}
+
+// Wallets returns all signer accounts registered under this account manager.
+func (am *Manager) Wallets() []Wallet {
+	am.lock.RLock()
+	defer am.lock.RUnlock()
+
+	cpy := make([]Wallet, len(am.wallets))
+	copy(cpy, am.wallets)
+	return cpy
+}
+
+// Wallet retrieves the wallet associated with a particular URL.
+func (am *Manager) Wallet(url string) (Wallet, error) {
+	am.lock.RLock()
+	defer am.lock.RUnlock()
+
+	parsed, err := parseURL(url)
+	if err != nil {
+		return nil, err
+	}
+	for _, wallet := range am.Wallets() {
+		if wallet.URL() == parsed {
+			return wallet, nil
+		}
+	}
+	return nil, ErrUnknownWallet
+}
+
+// Find attempts to locate the wallet corresponding to a specific account. Since
+// accounts can be dynamically added to and removed from wallets, this method has
+// a linear runtime in the number of wallets.
+func (am *Manager) Find(account Account) (Wallet, error) {
+	am.lock.RLock()
+	defer am.lock.RUnlock()
+
+	for _, wallet := range am.wallets {
+		if wallet.Contains(account) {
+			return wallet, nil
+		}
+	}
+	return nil, ErrUnknownAccount
+}
+
+// Subscribe creates an async subscription to receive notifications when the
+// manager detects the arrival or departure of a wallet from any of its backends.
+func (am *Manager) Subscribe(sink chan<- WalletEvent) event.Subscription {
+	return am.feed.Subscribe(sink)
+}
+
+// merge is a sorted analogue of append for wallets, where the ordering of the
+// origin list is preserved by inserting new wallets at the correct position.
+//
+// The original slice is assumed to be already sorted by URL.
+func merge(slice []Wallet, wallets ...Wallet) []Wallet {
+	for _, wallet := range wallets {
+		n := sort.Search(len(slice), func(i int) bool { return slice[i].URL().Cmp(wallet.URL()) >= 0 })
+		if n == len(slice) {
+			slice = append(slice, wallet)
+			continue
+		}
+		slice = append(slice[:n], append([]Wallet{wallet}, slice[n:]...)...)
+	}
+	return slice
+}
+
+// drop is the couterpart of merge, which looks up wallets from within the sorted
+// cache and removes the ones specified.
+func drop(slice []Wallet, wallets ...Wallet) []Wallet {
+	for _, wallet := range wallets {
+		n := sort.Search(len(slice), func(i int) bool { return slice[i].URL().Cmp(wallet.URL()) >= 0 })
+		if n == len(slice) {
+			// Wallet not found, may happen during startup
+			continue
+		}
+		slice = append(slice[:n], slice[n+1:]...)
+	}
+	return slice
+}
diff --git a/accounts/url.go b/accounts/url.go
new file mode 100644
index 000000000..a2d00c1c6
--- /dev/null
+++ b/accounts/url.go
@@ -0,0 +1,79 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package accounts
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"strings"
+)
+
+// URL represents the canonical identification URL of a wallet or account.
+//
+// It is a simplified version of url.URL, with the important limitations (which
+// are considered features here) that it contains value-copyable components only,
+// as well as that it doesn't do any URL encoding/decoding of special characters.
+//
+// The former is important to allow an account to be copied without leaving live
+// references to the original version, whereas the latter is important to ensure
+// one single canonical form opposed to many allowed ones by the RFC 3986 spec.
+//
+// As such, these URLs should not be used outside of the scope of an Ethereum
+// wallet or account.
+type URL struct {
+	Scheme string // Protocol scheme to identify a capable account backend
+	Path   string // Path for the backend to identify a unique entity
+}
+
+// parseURL converts a user supplied URL into the accounts specific structure.
+func parseURL(url string) (URL, error) {
+	parts := strings.Split(url, "://")
+	if len(parts) != 2 || parts[0] == "" {
+		return URL{}, errors.New("protocol scheme missing")
+	}
+	return URL{
+		Scheme: parts[0],
+		Path:   parts[1],
+	}, nil
+}
+
+// String implements the stringer interface.
+func (u URL) String() string {
+	if u.Scheme != "" {
+		return fmt.Sprintf("%s://%s", u.Scheme, u.Path)
+	}
+	return u.Path
+}
+
+// MarshalJSON implements the json.Marshaller interface.
+func (u URL) MarshalJSON() ([]byte, error) {
+	return json.Marshal(u.String())
+}
+
+// Cmp compares x and y and returns:
+//
+//   -1 if x <  y
+//    0 if x == y
+//   +1 if x >  y
+//
+func (u URL) Cmp(url URL) int {
+	if u.Scheme == url.Scheme {
+		return strings.Compare(u.Path, url.Path)
+	}
+	return strings.Compare(u.Scheme, url.Scheme)
+}
diff --git a/accounts/usbwallet/ledger_hub.go b/accounts/usbwallet/ledger_hub.go
new file mode 100644
index 000000000..ad5940cd4
--- /dev/null
+++ b/accounts/usbwallet/ledger_hub.go
@@ -0,0 +1,209 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+// This file contains the implementation for interacting with the Ledger hardware
+// wallets. The wire protocol spec can be found in the Ledger Blue GitHub repo:
+// https://raw.githubusercontent.com/LedgerHQ/blue-app-eth/master/doc/ethapp.asc
+
+// +build !ios
+
+package usbwallet
+
+import (
+	"fmt"
+	"sync"
+	"time"
+
+	"github.com/ethereum/go-ethereum/accounts"
+	"github.com/ethereum/go-ethereum/event"
+	"github.com/karalabe/gousb/usb"
+)
+
+// LedgerScheme is the protocol scheme prefixing account and wallet URLs.
+var LedgerScheme = "ledger"
+
+// ledgerDeviceIDs are the known device IDs that Ledger wallets use.
+var ledgerDeviceIDs = []deviceID{
+	{Vendor: 0x2c97, Product: 0x0000}, // Ledger Blue
+	{Vendor: 0x2c97, Product: 0x0001}, // Ledger Nano S
+}
+
+// Maximum time between wallet refreshes (if USB hotplug notifications don't work).
+const ledgerRefreshCycle = time.Second
+
+// Minimum time between wallet refreshes to avoid USB trashing.
+const ledgerRefreshThrottling = 500 * time.Millisecond
+
+// LedgerHub is a accounts.Backend that can find and handle Ledger hardware wallets.
+type LedgerHub struct {
+	ctx *usb.Context // Context interfacing with a libusb instance
+
+	refreshed   time.Time               // Time instance when the list of wallets was last refreshed
+	wallets     []accounts.Wallet       // List of Ledger devices currently tracking
+	updateFeed  event.Feed              // Event feed to notify wallet additions/removals
+	updateScope event.SubscriptionScope // Subscription scope tracking current live listeners
+	updating    bool                    // Whether the event notification loop is running
+
+	quit chan chan error
+	lock sync.RWMutex
+}
+
+// NewLedgerHub creates a new hardware wallet manager for Ledger devices.
+func NewLedgerHub() (*LedgerHub, error) {
+	// Initialize the USB library to access Ledgers through
+	ctx, err := usb.NewContext()
+	if err != nil {
+		return nil, err
+	}
+	// Create the USB hub, start and return it
+	hub := &LedgerHub{
+		ctx:  ctx,
+		quit: make(chan chan error),
+	}
+	hub.refreshWallets()
+
+	return hub, nil
+}
+
+// Wallets implements accounts.Backend, returning all the currently tracked USB
+// devices that appear to be Ledger hardware wallets.
+func (hub *LedgerHub) Wallets() []accounts.Wallet {
+	// Make sure the list of wallets is up to date
+	hub.refreshWallets()
+
+	hub.lock.RLock()
+	defer hub.lock.RUnlock()
+
+	cpy := make([]accounts.Wallet, len(hub.wallets))
+	copy(cpy, hub.wallets)
+	return cpy
+}
+
+// refreshWallets scans the USB devices attached to the machine and updates the
+// list of wallets based on the found devices.
+func (hub *LedgerHub) refreshWallets() {
+	// Don't scan the USB like crazy it the user fetches wallets in a loop
+	hub.lock.RLock()
+	elapsed := time.Since(hub.refreshed)
+	hub.lock.RUnlock()
+
+	if elapsed < ledgerRefreshThrottling {
+		return
+	}
+	// Retrieve the current list of Ledger devices
+	var devIDs []deviceID
+	var busIDs []uint16
+
+	hub.ctx.ListDevices(func(desc *usb.Descriptor) bool {
+		// Gather Ledger devices, don't connect any just yet
+		for _, id := range ledgerDeviceIDs {
+			if desc.Vendor == id.Vendor && desc.Product == id.Product {
+				devIDs = append(devIDs, deviceID{Vendor: desc.Vendor, Product: desc.Product})
+				busIDs = append(busIDs, uint16(desc.Bus)<<8+uint16(desc.Address))
+				return false
+			}
+		}
+		// Not ledger, ignore and don't connect either
+		return false
+	})
+	// Transform the current list of wallets into the new one
+	hub.lock.Lock()
+
+	wallets := make([]accounts.Wallet, 0, len(devIDs))
+	events := []accounts.WalletEvent{}
+
+	for i := 0; i < len(devIDs); i++ {
+		devID, busID := devIDs[i], busIDs[i]
+
+		url := accounts.URL{Scheme: LedgerScheme, Path: fmt.Sprintf("%03d:%03d", busID>>8, busID&0xff)}
+
+		// Drop wallets in front of the next device or those that failed for some reason
+		for len(hub.wallets) > 0 && (hub.wallets[0].URL().Cmp(url) < 0 || hub.wallets[0].(*ledgerWallet).failed()) {
+			events = append(events, accounts.WalletEvent{Wallet: hub.wallets[0], Arrive: false})
+			hub.wallets = hub.wallets[1:]
+		}
+		// If there are no more wallets or the device is before the next, wrap new wallet
+		if len(hub.wallets) == 0 || hub.wallets[0].URL().Cmp(url) > 0 {
+			wallet := &ledgerWallet{context: hub.ctx, hardwareID: devID, locationID: busID, url: &url}
+
+			events = append(events, accounts.WalletEvent{Wallet: wallet, Arrive: true})
+			wallets = append(wallets, wallet)
+			continue
+		}
+		// If the device is the same as the first wallet, keep it
+		if hub.wallets[0].URL().Cmp(url) == 0 {
+			wallets = append(wallets, hub.wallets[0])
+			hub.wallets = hub.wallets[1:]
+			continue
+		}
+	}
+	// Drop any leftover wallets and set the new batch
+	for _, wallet := range hub.wallets {
+		events = append(events, accounts.WalletEvent{Wallet: wallet, Arrive: false})
+	}
+	hub.refreshed = time.Now()
+	hub.wallets = wallets
+	hub.lock.Unlock()
+
+	// Fire all wallet events and return
+	for _, event := range events {
+		hub.updateFeed.Send(event)
+	}
+}
+
+// Subscribe implements accounts.Backend, creating an async subscription to
+// receive notifications on the addition or removal of Ledger wallets.
+func (hub *LedgerHub) Subscribe(sink chan<- accounts.WalletEvent) event.Subscription {
+	// We need the mutex to reliably start/stop the update loop
+	hub.lock.Lock()
+	defer hub.lock.Unlock()
+
+	// Subscribe the caller and track the subscriber count
+	sub := hub.updateScope.Track(hub.updateFeed.Subscribe(sink))
+
+	// Subscribers require an active notification loop, start it
+	if !hub.updating {
+		hub.updating = true
+		go hub.updater()
+	}
+	return sub
+}
+
+// updater is responsible for maintaining an up-to-date list of wallets stored in
+// the keystore, and for firing wallet addition/removal events. It listens for
+// account change events from the underlying account cache, and also periodically
+// forces a manual refresh (only triggers for systems where the filesystem notifier
+// is not running).
+func (hub *LedgerHub) updater() {
+	for {
+		// Wait for a USB hotplug event (not supported yet) or a refresh timeout
+		select {
+		//case <-hub.changes: // reenable on hutplug implementation
+		case <-time.After(ledgerRefreshCycle):
+		}
+		// Run the wallet refresher
+		hub.refreshWallets()
+
+		// If all our subscribers left, stop the updater
+		hub.lock.Lock()
+		if hub.updateScope.Count() == 0 {
+			hub.updating = false
+			hub.lock.Unlock()
+			return
+		}
+		hub.lock.Unlock()
+	}
+}
diff --git a/accounts/usbwallet/ledger_wallet.go b/accounts/usbwallet/ledger_wallet.go
new file mode 100644
index 000000000..a667f580a
--- /dev/null
+++ b/accounts/usbwallet/ledger_wallet.go
@@ -0,0 +1,945 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+// This file contains the implementation for interacting with the Ledger hardware
+// wallets. The wire protocol spec can be found in the Ledger Blue GitHub repo:
+// https://raw.githubusercontent.com/LedgerHQ/blue-app-eth/master/doc/ethapp.asc
+
+// +build !ios
+
+package usbwallet
+
+import (
+	"encoding/binary"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"io"
+	"math/big"
+	"sync"
+	"time"
+
+	ethereum "github.com/ethereum/go-ethereum"
+	"github.com/ethereum/go-ethereum/accounts"
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/logger"
+	"github.com/ethereum/go-ethereum/logger/glog"
+	"github.com/ethereum/go-ethereum/rlp"
+	"github.com/karalabe/gousb/usb"
+	"golang.org/x/net/context"
+)
+
+// Maximum time between wallet health checks to detect USB unplugs.
+const ledgerHeartbeatCycle = time.Second
+
+// Minimum time to wait between self derivation attempts, even it the user is
+// requesting accounts like crazy.
+const ledgerSelfDeriveThrottling = time.Second
+
+// ledgerOpcode is an enumeration encoding the supported Ledger opcodes.
+type ledgerOpcode byte
+
+// ledgerParam1 is an enumeration encoding the supported Ledger parameters for
+// specific opcodes. The same parameter values may be reused between opcodes.
+type ledgerParam1 byte
+
+// ledgerParam2 is an enumeration encoding the supported Ledger parameters for
+// specific opcodes. The same parameter values may be reused between opcodes.
+type ledgerParam2 byte
+
+const (
+	ledgerOpRetrieveAddress  ledgerOpcode = 0x02 // Returns the public key and Ethereum address for a given BIP 32 path
+	ledgerOpSignTransaction  ledgerOpcode = 0x04 // Signs an Ethereum transaction after having the user validate the parameters
+	ledgerOpGetConfiguration ledgerOpcode = 0x06 // Returns specific wallet application configuration
+
+	ledgerP1DirectlyFetchAddress    ledgerParam1 = 0x00 // Return address directly from the wallet
+	ledgerP1ConfirmFetchAddress     ledgerParam1 = 0x01 // Require a user confirmation before returning the address
+	ledgerP1InitTransactionData     ledgerParam1 = 0x00 // First transaction data block for signing
+	ledgerP1ContTransactionData     ledgerParam1 = 0x80 // Subsequent transaction data block for signing
+	ledgerP2DiscardAddressChainCode ledgerParam2 = 0x00 // Do not return the chain code along with the address
+	ledgerP2ReturnAddressChainCode  ledgerParam2 = 0x01 // Require a user confirmation before returning the address
+)
+
+// errReplyInvalidHeader is the error message returned by a Ledfer data exchange
+// if the device replies with a mismatching header. This usually means the device
+// is in browser mode.
+var errReplyInvalidHeader = errors.New("invalid reply header")
+
+// ledgerWallet represents a live USB Ledger hardware wallet.
+type ledgerWallet struct {
+	context    *usb.Context  // USB context to interface libusb through
+	hardwareID deviceID      // USB identifiers to identify this device type
+	locationID uint16        // USB bus and address to identify this device instance
+	url        *accounts.URL // Textual URL uniquely identifying this wallet
+
+	device  *usb.Device  // USB device advertising itself as a Ledger wallet
+	input   usb.Endpoint // Input endpoint to send data to this device
+	output  usb.Endpoint // Output endpoint to receive data from this device
+	failure error        // Any failure that would make the device unusable
+
+	version  [3]byte                                    // Current version of the Ledger Ethereum app (zero if app is offline)
+	browser  bool                                       // Flag whether the Ledger is in browser mode (reply channel mismatch)
+	accounts []accounts.Account                         // List of derive accounts pinned on the Ledger
+	paths    map[common.Address]accounts.DerivationPath // Known derivation paths for signing operations
+
+	deriveNextPath accounts.DerivationPath   // Next derivation path for account auto-discovery
+	deriveNextAddr common.Address            // Next derived account address for auto-discovery
+	deriveChain    ethereum.ChainStateReader // Blockchain state reader to discover used account with
+	deriveReq      chan chan struct{}        // Channel to request a self-derivation on
+	deriveQuit     chan chan error           // Channel to terminate the self-deriver with
+
+	healthQuit chan chan error
+
+	// Locking a hardware wallet is a bit special. Since hardware devices are lower
+	// performing, any communication with them might take a non negligible amount of
+	// time. Worse still, waiting for user confirmation can take arbitrarily long,
+	// but exclusive communication must be upheld during. Locking the entire wallet
+	// in the mean time however would stall any parts of the system that don't want
+	// to communicate, just read some state (e.g. list the accounts).
+	//
+	// As such, a hardware wallet needs two locks to function correctly. A state
+	// lock can be used to protect the wallet's software-side internal state, which
+	// must not be held exlusively during hardware communication. A communication
+	// lock can be used to achieve exclusive access to the device itself, this one
+	// however should allow "skipping" waiting for operations that might want to
+	// use the device, but can live without too (e.g. account self-derivation).
+	//
+	// Since we have two locks, it's important to know how to properly use them:
+	//   - Communication requires the `device` to not change, so obtaining the
+	//     commsLock should be done after having a stateLock.
+	//   - Communication must not disable read access to the wallet state, so it
+	//     must only ever hold a *read* lock to stateLock.
+	commsLock chan struct{} // Mutex (buf=1) for the USB comms without keeping the state locked
+	stateLock sync.RWMutex  // Protects read and write access to the wallet struct fields
+}
+
+// URL implements accounts.Wallet, returning the URL of the Ledger device.
+func (w *ledgerWallet) URL() accounts.URL {
+	return *w.url // Immutable, no need for a lock
+}
+
+// Status implements accounts.Wallet, always whether the Ledger is opened, closed
+// or whether the Ethereum app was not started on it.
+func (w *ledgerWallet) Status() string {
+	w.stateLock.RLock() // No device communication, state lock is enough
+	defer w.stateLock.RUnlock()
+
+	if w.failure != nil {
+		return fmt.Sprintf("Failed: %v", w.failure)
+	}
+	if w.device == nil {
+		return "Closed"
+	}
+	if w.browser {
+		return "Ethereum app in browser mode"
+	}
+	if w.offline() {
+		return "Ethereum app offline"
+	}
+	return fmt.Sprintf("Ethereum app v%d.%d.%d online", w.version[0], w.version[1], w.version[2])
+}
+
+// offline returns whether the wallet and the Ethereum app is offline or not.
+//
+// The method assumes that the state lock is held!
+func (w *ledgerWallet) offline() bool {
+	return w.version == [3]byte{0, 0, 0}
+}
+
+// failed returns if the USB device wrapped by the wallet failed for some reason.
+// This is used by the device scanner to report failed wallets as departed.
+//
+// The method assumes that the state lock is *not* held!
+func (w *ledgerWallet) failed() bool {
+	w.stateLock.RLock() // No device communication, state lock is enough
+	defer w.stateLock.RUnlock()
+
+	return w.failure != nil
+}
+
+// Open implements accounts.Wallet, attempting to open a USB connection to the
+// Ledger hardware wallet. The Ledger does not require a user passphrase, so that
+// parameter is silently discarded.
+func (w *ledgerWallet) Open(passphrase string) error {
+	w.stateLock.Lock() // State lock is enough since there's no connection yet at this point
+	defer w.stateLock.Unlock()
+
+	// If the wallet was already opened, don't try to open again
+	if w.device != nil {
+		return accounts.ErrWalletAlreadyOpen
+	}
+	// Otherwise iterate over all USB devices and find this again (no way to directly do this)
+	// Iterate over all attached devices and fetch those seemingly Ledger
+	devices, err := w.context.ListDevices(func(desc *usb.Descriptor) bool {
+		// Only open this single specific device
+		return desc.Vendor == w.hardwareID.Vendor && desc.Product == w.hardwareID.Product &&
+			uint16(desc.Bus)<<8+uint16(desc.Address) == w.locationID
+	})
+	if err != nil {
+		return err
+	}
+	if len(devices) == 0 {
+		return accounts.ErrUnknownWallet
+	}
+	// Device opened, attach to the input and output endpoints
+	device := devices[0]
+
+	var invalid string
+	switch {
+	case len(device.Descriptor.Configs) == 0:
+		invalid = "no endpoint config available"
+	case len(device.Descriptor.Configs[0].Interfaces) == 0:
+		invalid = "no endpoint interface available"
+	case len(device.Descriptor.Configs[0].Interfaces[0].Setups) == 0:
+		invalid = "no endpoint setup available"
+	case len(device.Descriptor.Configs[0].Interfaces[0].Setups[0].Endpoints) < 2:
+		invalid = "not enough IO endpoints available"
+	}
+	if invalid != "" {
+		device.Close()
+		return fmt.Errorf("ledger wallet [%s] invalid: %s", w.url, invalid)
+	}
+	// Open the input and output endpoints to the device
+	input, err := device.OpenEndpoint(
+		device.Descriptor.Configs[0].Config,
+		device.Descriptor.Configs[0].Interfaces[0].Number,
+		device.Descriptor.Configs[0].Interfaces[0].Setups[0].Number,
+		device.Descriptor.Configs[0].Interfaces[0].Setups[0].Endpoints[1].Address,
+	)
+	if err != nil {
+		device.Close()
+		return fmt.Errorf("ledger wallet [%s] input open failed: %v", w.url, err)
+	}
+	output, err := device.OpenEndpoint(
+		device.Descriptor.Configs[0].Config,
+		device.Descriptor.Configs[0].Interfaces[0].Number,
+		device.Descriptor.Configs[0].Interfaces[0].Setups[0].Number,
+		device.Descriptor.Configs[0].Interfaces[0].Setups[0].Endpoints[0].Address,
+	)
+	if err != nil {
+		device.Close()
+		return fmt.Errorf("ledger wallet [%s] output open failed: %v", w.url, err)
+	}
+	// Wallet seems to be successfully opened, guess if the Ethereum app is running
+	w.device, w.input, w.output = device, input, output
+	w.commsLock = make(chan struct{}, 1)
+	w.commsLock <- struct{}{} // Enable lock
+
+	w.paths = make(map[common.Address]accounts.DerivationPath)
+
+	w.deriveReq = make(chan chan struct{})
+	w.deriveQuit = make(chan chan error)
+	w.healthQuit = make(chan chan error)
+
+	defer func() {
+		go w.heartbeat()
+		go w.selfDerive()
+	}()
+
+	if _, err = w.ledgerDerive(accounts.DefaultBaseDerivationPath); err != nil {
+		// Ethereum app is not running or in browser mode, nothing more to do, return
+		if err == errReplyInvalidHeader {
+			w.browser = true
+		}
+		return nil
+	}
+	// Try to resolve the Ethereum app's version, will fail prior to v1.0.2
+	if w.version, err = w.ledgerVersion(); err != nil {
+		w.version = [3]byte{1, 0, 0} // Assume worst case, can't verify if v1.0.0 or v1.0.1
+	}
+	return nil
+}
+
+// heartbeat is a health check loop for the Ledger wallets to periodically verify
+// whether they are still present or if they malfunctioned. It is needed because:
+//  - libusb on Windows doesn't support hotplug, so we can't detect USB unplugs
+//  - communication timeout on the Ledger requires a device power cycle to fix
+func (w *ledgerWallet) heartbeat() {
+	glog.V(logger.Debug).Infof("%s health-check started", w.url.String())
+	defer glog.V(logger.Debug).Infof("%s health-check stopped", w.url.String())
+
+	// Execute heartbeat checks until termination or error
+	var (
+		errc chan error
+		err  error
+	)
+	for errc == nil && err == nil {
+		// Wait until termination is requested or the heartbeat cycle arrives
+		select {
+		case errc = <-w.healthQuit:
+			// Termination requested
+			continue
+		case <-time.After(ledgerHeartbeatCycle):
+			// Heartbeat time
+		}
+		// Execute a tiny data exchange to see responsiveness
+		w.stateLock.RLock()
+		if w.device == nil {
+			// Terminated while waiting for the lock
+			w.stateLock.RUnlock()
+			continue
+		}
+		<-w.commsLock // Don't lock state while resolving version
+		_, err = w.ledgerVersion()
+		w.commsLock <- struct{}{}
+		w.stateLock.RUnlock()
+
+		if err == usb.ERROR_IO || err == usb.ERROR_NO_DEVICE {
+			w.stateLock.Lock() // Lock state to tear the wallet down
+			w.failure = err
+			w.close()
+			w.stateLock.Unlock()
+		}
+		// Ignore uninteresting errors
+		err = nil
+	}
+	// In case of error, wait for termination
+	if err != nil {
+		glog.V(logger.Debug).Infof("%s health-check failed: %v", w.url.String(), err)
+		errc = <-w.healthQuit
+	}
+	errc <- err
+}
+
+// Close implements accounts.Wallet, closing the USB connection to the Ledger.
+func (w *ledgerWallet) Close() error {
+	// Ensure the wallet was opened
+	w.stateLock.RLock()
+	hQuit, dQuit := w.healthQuit, w.deriveQuit
+	w.stateLock.RUnlock()
+
+	// Terminate the health checks
+	var herr error
+	if hQuit != nil {
+		errc := make(chan error)
+		hQuit <- errc
+		herr = <-errc // Save for later, we *must* close the USB
+	}
+	// Terminate the self-derivations
+	var derr error
+	if dQuit != nil {
+		errc := make(chan error)
+		dQuit <- errc
+		derr = <-errc // Save for later, we *must* close the USB
+	}
+	// Terminate the device connection
+	w.stateLock.Lock()
+	defer w.stateLock.Unlock()
+
+	w.healthQuit = nil
+	w.deriveQuit = nil
+	w.deriveReq = nil
+
+	if err := w.close(); err != nil {
+		return err
+	}
+	if herr != nil {
+		return herr
+	}
+	return derr
+}
+
+// close is the internal wallet closer that terminates the USB connection and
+// resets all the fields to their defaults.
+//
+// Note, close assumes the state lock is held!
+func (w *ledgerWallet) close() error {
+	// Allow duplicate closes, especially for health-check failures
+	if w.device == nil {
+		return nil
+	}
+	// Close the device, clear everything, then return
+	err := w.device.Close()
+
+	w.device, w.input, w.output = nil, nil, nil
+	w.browser, w.version = false, [3]byte{}
+	w.accounts, w.paths = nil, nil
+
+	return err
+}
+
+// Accounts implements accounts.Wallet, returning the list of accounts pinned to
+// the Ledger hardware wallet. If self-derivation was enabled, the account list
+// is periodically expanded based on current chain state.
+func (w *ledgerWallet) Accounts() []accounts.Account {
+	// Attempt self-derivation if it's running
+	reqc := make(chan struct{}, 1)
+	select {
+	case w.deriveReq <- reqc:
+		// Self-derivation request accepted, wait for it
+		<-reqc
+	default:
+		// Self-derivation offline, throttled or busy, skip
+	}
+	// Return whatever account list we ended up with
+	w.stateLock.RLock()
+	defer w.stateLock.RUnlock()
+
+	cpy := make([]accounts.Account, len(w.accounts))
+	copy(cpy, w.accounts)
+	return cpy
+}
+
+// selfDerive is an account derivation loop that upon request attempts to find
+// new non-zero accounts.
+func (w *ledgerWallet) selfDerive() {
+	glog.V(logger.Debug).Infof("%s self-derivation started", w.url.String())
+	defer glog.V(logger.Debug).Infof("%s self-derivation stopped", w.url.String())
+
+	// Execute self-derivations until termination or error
+	var (
+		reqc chan struct{}
+		errc chan error
+		err  error
+	)
+	for errc == nil && err == nil {
+		// Wait until either derivation or termination is requested
+		select {
+		case errc = <-w.deriveQuit:
+			// Termination requested
+			continue
+		case reqc = <-w.deriveReq:
+			// Account discovery requested
+		}
+		// Derivation needs a chain and device access, skip if either unavailable
+		w.stateLock.RLock()
+		if w.device == nil || w.deriveChain == nil || w.offline() {
+			w.stateLock.RUnlock()
+			reqc <- struct{}{}
+			continue
+		}
+		select {
+		case <-w.commsLock:
+		default:
+			w.stateLock.RUnlock()
+			reqc <- struct{}{}
+			continue
+		}
+		// Device lock obtained, derive the next batch of accounts
+		var (
+			accs  []accounts.Account
+			paths []accounts.DerivationPath
+
+			nextAddr = w.deriveNextAddr
+			nextPath = w.deriveNextPath
+
+			context = context.Background()
+		)
+		for empty := false; !empty; {
+			// Retrieve the next derived Ethereum account
+			if nextAddr == (common.Address{}) {
+				if nextAddr, err = w.ledgerDerive(nextPath); err != nil {
+					glog.V(logger.Warn).Infof("%s self-derivation failed: %v", w.url.String(), err)
+					break
+				}
+			}
+			// Check the account's status against the current chain state
+			var (
+				balance *big.Int
+				nonce   uint64
+			)
+			balance, err = w.deriveChain.BalanceAt(context, nextAddr, nil)
+			if err != nil {
+				glog.V(logger.Warn).Infof("%s self-derivation balance retrieval failed: %v", w.url.String(), err)
+				break
+			}
+			nonce, err = w.deriveChain.NonceAt(context, nextAddr, nil)
+			if err != nil {
+				glog.V(logger.Warn).Infof("%s self-derivation nonce retrieval failed: %v", w.url.String(), err)
+				break
+			}
+			// If the next account is empty, stop self-derivation, but add it nonetheless
+			if balance.BitLen() == 0 && nonce == 0 {
+				empty = true
+			}
+			// We've just self-derived a new account, start tracking it locally
+			path := make(accounts.DerivationPath, len(nextPath))
+			copy(path[:], nextPath[:])
+			paths = append(paths, path)
+
+			account := accounts.Account{
+				Address: nextAddr,
+				URL:     accounts.URL{Scheme: w.url.Scheme, Path: fmt.Sprintf("%s/%s", w.url.Path, path)},
+			}
+			accs = append(accs, account)
+
+			// Display a log message to the user for new (or previously empty accounts)
+			if _, known := w.paths[nextAddr]; !known || (!empty && nextAddr == w.deriveNextAddr) {
+				glog.V(logger.Info).Infof("%s discovered %s (balance %22v, nonce %4d) at %s", w.url.String(), nextAddr.Hex(), balance, nonce, path)
+			}
+			// Fetch the next potential account
+			if !empty {
+				nextAddr = common.Address{}
+				nextPath[len(nextPath)-1]++
+			}
+		}
+		// Self derivation complete, release device lock
+		w.commsLock <- struct{}{}
+		w.stateLock.RUnlock()
+
+		// Insert any accounts successfully derived
+		w.stateLock.Lock()
+		for i := 0; i < len(accs); i++ {
+			if _, ok := w.paths[accs[i].Address]; !ok {
+				w.accounts = append(w.accounts, accs[i])
+				w.paths[accs[i].Address] = paths[i]
+			}
+		}
+		// Shift the self-derivation forward
+		// TODO(karalabe): don't overwrite changes from wallet.SelfDerive
+		w.deriveNextAddr = nextAddr
+		w.deriveNextPath = nextPath
+		w.stateLock.Unlock()
+
+		// Notify the user of termination and loop after a bit of time (to avoid trashing)
+		reqc <- struct{}{}
+		if err == nil {
+			select {
+			case errc = <-w.deriveQuit:
+				// Termination requested, abort
+			case <-time.After(ledgerSelfDeriveThrottling):
+				// Waited enough, willing to self-derive again
+			}
+		}
+	}
+	// In case of error, wait for termination
+	if err != nil {
+		glog.V(logger.Debug).Infof("%s self-derivation failed: %s", w.url.String(), err)
+		errc = <-w.deriveQuit
+	}
+	errc <- err
+}
+
+// Contains implements accounts.Wallet, returning whether a particular account is
+// or is not pinned into this Ledger instance. Although we could attempt to resolve
+// unpinned accounts, that would be an non-negligible hardware operation.
+func (w *ledgerWallet) Contains(account accounts.Account) bool {
+	w.stateLock.RLock()
+	defer w.stateLock.RUnlock()
+
+	_, exists := w.paths[account.Address]
+	return exists
+}
+
+// Derive implements accounts.Wallet, deriving a new account at the specific
+// derivation path. If pin is set to true, the account will be added to the list
+// of tracked accounts.
+func (w *ledgerWallet) Derive(path accounts.DerivationPath, pin bool) (accounts.Account, error) {
+	// Try to derive the actual account and update its URL if successful
+	w.stateLock.RLock() // Avoid device disappearing during derivation
+
+	if w.device == nil || w.offline() {
+		w.stateLock.RUnlock()
+		return accounts.Account{}, accounts.ErrWalletClosed
+	}
+	<-w.commsLock // Avoid concurrent hardware access
+	address, err := w.ledgerDerive(path)
+	w.commsLock <- struct{}{}
+
+	w.stateLock.RUnlock()
+
+	// If an error occurred or no pinning was requested, return
+	if err != nil {
+		return accounts.Account{}, err
+	}
+	account := accounts.Account{
+		Address: address,
+		URL:     accounts.URL{Scheme: w.url.Scheme, Path: fmt.Sprintf("%s/%s", w.url.Path, path)},
+	}
+	if !pin {
+		return account, nil
+	}
+	// Pinning needs to modify the state
+	w.stateLock.Lock()
+	defer w.stateLock.Unlock()
+
+	if _, ok := w.paths[address]; !ok {
+		w.accounts = append(w.accounts, account)
+		w.paths[address] = path
+	}
+	return account, nil
+}
+
+// SelfDerive implements accounts.Wallet, trying to discover accounts that the
+// user used previously (based on the chain state), but ones that he/she did not
+// explicitly pin to the wallet manually. To avoid chain head monitoring, self
+// derivation only runs during account listing (and even then throttled).
+func (w *ledgerWallet) SelfDerive(base accounts.DerivationPath, chain ethereum.ChainStateReader) {
+	w.stateLock.Lock()
+	defer w.stateLock.Unlock()
+
+	w.deriveNextPath = make(accounts.DerivationPath, len(base))
+	copy(w.deriveNextPath[:], base[:])
+
+	w.deriveNextAddr = common.Address{}
+	w.deriveChain = chain
+}
+
+// SignHash implements accounts.Wallet, however signing arbitrary data is not
+// supported for Ledger wallets, so this method will always return an error.
+func (w *ledgerWallet) SignHash(acc accounts.Account, hash []byte) ([]byte, error) {
+	return nil, accounts.ErrNotSupported
+}
+
+// SignTx implements accounts.Wallet. It sends the transaction over to the Ledger
+// wallet to request a confirmation from the user. It returns either the signed
+// transaction or a failure if the user denied the transaction.
+//
+// Note, if the version of the Ethereum application running on the Ledger wallet is
+// too old to sign EIP-155 transactions, but such is requested nonetheless, an error
+// will be returned opposed to silently signing in Homestead mode.
+func (w *ledgerWallet) SignTx(account accounts.Account, tx *types.Transaction, chainID *big.Int) (*types.Transaction, error) {
+	w.stateLock.RLock() // Comms have own mutex, this is for the state fields
+	defer w.stateLock.RUnlock()
+
+	// If the wallet is closed, or the Ethereum app doesn't run, abort
+	if w.device == nil || w.offline() {
+		return nil, accounts.ErrWalletClosed
+	}
+	// Make sure the requested account is contained within
+	path, ok := w.paths[account.Address]
+	if !ok {
+		return nil, accounts.ErrUnknownAccount
+	}
+	// Ensure the wallet is capable of signing the given transaction
+	if chainID != nil && w.version[0] <= 1 && w.version[1] <= 0 && w.version[2] <= 2 {
+		return nil, fmt.Errorf("Ledger v%d.%d.%d doesn't support signing this transaction, please update to v1.0.3 at least", w.version[0], w.version[1], w.version[2])
+	}
+	// All infos gathered and metadata checks out, request signing
+	<-w.commsLock
+	defer func() { w.commsLock <- struct{}{} }()
+
+	return w.ledgerSign(path, account.Address, tx, chainID)
+}
+
+// SignHashWithPassphrase implements accounts.Wallet, however signing arbitrary
+// data is not supported for Ledger wallets, so this method will always return
+// an error.
+func (w *ledgerWallet) SignHashWithPassphrase(account accounts.Account, passphrase string, hash []byte) ([]byte, error) {
+	return nil, accounts.ErrNotSupported
+}
+
+// SignTxWithPassphrase implements accounts.Wallet, attempting to sign the given
+// transaction with the given account using passphrase as extra authentication.
+// Since the Ledger does not support extra passphrases, it is silently ignored.
+func (w *ledgerWallet) SignTxWithPassphrase(account accounts.Account, passphrase string, tx *types.Transaction, chainID *big.Int) (*types.Transaction, error) {
+	return w.SignTx(account, tx, chainID)
+}
+
+// ledgerVersion retrieves the current version of the Ethereum wallet app running
+// on the Ledger wallet.
+//
+// The version retrieval protocol is defined as follows:
+//
+//   CLA | INS | P1 | P2 | Lc | Le
+//   ----+-----+----+----+----+---
+//    E0 | 06  | 00 | 00 | 00 | 04
+//
+// With no input data, and the output data being:
+//
+//   Description                                        | Length
+//   ---------------------------------------------------+--------
+//   Flags 01: arbitrary data signature enabled by user | 1 byte
+//   Application major version                          | 1 byte
+//   Application minor version                          | 1 byte
+//   Application patch version                          | 1 byte
+func (w *ledgerWallet) ledgerVersion() ([3]byte, error) {
+	// Send the request and wait for the response
+	reply, err := w.ledgerExchange(ledgerOpGetConfiguration, 0, 0, nil)
+	if err != nil {
+		return [3]byte{}, err
+	}
+	if len(reply) != 4 {
+		return [3]byte{}, errors.New("reply not of correct size")
+	}
+	// Cache the version for future reference
+	var version [3]byte
+	copy(version[:], reply[1:])
+	return version, nil
+}
+
+// ledgerDerive retrieves the currently active Ethereum address from a Ledger
+// wallet at the specified derivation path.
+//
+// The address derivation protocol is defined as follows:
+//
+//   CLA | INS | P1 | P2 | Lc  | Le
+//   ----+-----+----+----+-----+---
+//    E0 | 02  | 00 return address
+//               01 display address and confirm before returning
+//                  | 00: do not return the chain code
+//                  | 01: return the chain code
+//                       | var | 00
+//
+// Where the input data is:
+//
+//   Description                                      | Length
+//   -------------------------------------------------+--------
+//   Number of BIP 32 derivations to perform (max 10) | 1 byte
+//   First derivation index (big endian)              | 4 bytes
+//   ...                                              | 4 bytes
+//   Last derivation index (big endian)               | 4 bytes
+//
+// And the output data is:
+//
+//   Description             | Length
+//   ------------------------+-------------------
+//   Public Key length       | 1 byte
+//   Uncompressed Public Key | arbitrary
+//   Ethereum address length | 1 byte
+//   Ethereum address        | 40 bytes hex ascii
+//   Chain code if requested | 32 bytes
+func (w *ledgerWallet) ledgerDerive(derivationPath []uint32) (common.Address, error) {
+	// Flatten the derivation path into the Ledger request
+	path := make([]byte, 1+4*len(derivationPath))
+	path[0] = byte(len(derivationPath))
+	for i, component := range derivationPath {
+		binary.BigEndian.PutUint32(path[1+4*i:], component)
+	}
+	// Send the request and wait for the response
+	reply, err := w.ledgerExchange(ledgerOpRetrieveAddress, ledgerP1DirectlyFetchAddress, ledgerP2DiscardAddressChainCode, path)
+	if err != nil {
+		return common.Address{}, err
+	}
+	// Discard the public key, we don't need that for now
+	if len(reply) < 1 || len(reply) < 1+int(reply[0]) {
+		return common.Address{}, errors.New("reply lacks public key entry")
+	}
+	reply = reply[1+int(reply[0]):]
+
+	// Extract the Ethereum hex address string
+	if len(reply) < 1 || len(reply) < 1+int(reply[0]) {
+		return common.Address{}, errors.New("reply lacks address entry")
+	}
+	hexstr := reply[1 : 1+int(reply[0])]
+
+	// Decode the hex sting into an Ethereum address and return
+	var address common.Address
+	hex.Decode(address[:], hexstr)
+	return address, nil
+}
+
+// ledgerSign sends the transaction to the Ledger wallet, and waits for the user
+// to confirm or deny the transaction.
+//
+// The transaction signing protocol is defined as follows:
+//
+//   CLA | INS | P1 | P2 | Lc  | Le
+//   ----+-----+----+----+-----+---
+//    E0 | 04  | 00: first transaction data block
+//               80: subsequent transaction data block
+//                  | 00 | variable | variable
+//
+// Where the input for the first transaction block (first 255 bytes) is:
+//
+//   Description                                      | Length
+//   -------------------------------------------------+----------
+//   Number of BIP 32 derivations to perform (max 10) | 1 byte
+//   First derivation index (big endian)              | 4 bytes
+//   ...                                              | 4 bytes
+//   Last derivation index (big endian)               | 4 bytes
+//   RLP transaction chunk                            | arbitrary
+//
+// And the input for subsequent transaction blocks (first 255 bytes) are:
+//
+//   Description           | Length
+//   ----------------------+----------
+//   RLP transaction chunk | arbitrary
+//
+// And the output data is:
+//
+//   Description | Length
+//   ------------+---------
+//   signature V | 1 byte
+//   signature R | 32 bytes
+//   signature S | 32 bytes
+func (w *ledgerWallet) ledgerSign(derivationPath []uint32, address common.Address, tx *types.Transaction, chainID *big.Int) (*types.Transaction, error) {
+	// We need to modify the timeouts to account for user feedback
+	defer func(old time.Duration) { w.device.ReadTimeout = old }(w.device.ReadTimeout)
+	w.device.ReadTimeout = time.Hour * 24 * 30 // Timeout requires a Ledger power cycle, only if you must
+
+	// Flatten the derivation path into the Ledger request
+	path := make([]byte, 1+4*len(derivationPath))
+	path[0] = byte(len(derivationPath))
+	for i, component := range derivationPath {
+		binary.BigEndian.PutUint32(path[1+4*i:], component)
+	}
+	// Create the transaction RLP based on whether legacy or EIP155 signing was requeste
+	var (
+		txrlp []byte
+		err   error
+	)
+	if chainID == nil {
+		if txrlp, err = rlp.EncodeToBytes([]interface{}{tx.Nonce(), tx.GasPrice(), tx.Gas(), tx.To(), tx.Value(), tx.Data()}); err != nil {
+			return nil, err
+		}
+	} else {
+		if txrlp, err = rlp.EncodeToBytes([]interface{}{tx.Nonce(), tx.GasPrice(), tx.Gas(), tx.To(), tx.Value(), tx.Data(), chainID, big.NewInt(0), big.NewInt(0)}); err != nil {
+			return nil, err
+		}
+	}
+	payload := append(path, txrlp...)
+
+	// Send the request and wait for the response
+	var (
+		op    = ledgerP1InitTransactionData
+		reply []byte
+	)
+	for len(payload) > 0 {
+		// Calculate the size of the next data chunk
+		chunk := 255
+		if chunk > len(payload) {
+			chunk = len(payload)
+		}
+		// Send the chunk over, ensuring it's processed correctly
+		reply, err = w.ledgerExchange(ledgerOpSignTransaction, op, 0, payload[:chunk])
+		if err != nil {
+			return nil, err
+		}
+		// Shift the payload and ensure subsequent chunks are marked as such
+		payload = payload[chunk:]
+		op = ledgerP1ContTransactionData
+	}
+	// Extract the Ethereum signature and do a sanity validation
+	if len(reply) != 65 {
+		return nil, errors.New("reply lacks signature")
+	}
+	signature := append(reply[1:], reply[0])
+
+	// Create the correct signer and signature transform based on the chain ID
+	var signer types.Signer
+	if chainID == nil {
+		signer = new(types.HomesteadSigner)
+	} else {
+		signer = types.NewEIP155Signer(chainID)
+		signature[64] = signature[64] - byte(chainID.Uint64()*2+35)
+	}
+	// Inject the final signature into the transaction and sanity check the sender
+	signed, err := tx.WithSignature(signer, signature)
+	if err != nil {
+		return nil, err
+	}
+	sender, err := types.Sender(signer, signed)
+	if err != nil {
+		return nil, err
+	}
+	if sender != address {
+		return nil, fmt.Errorf("signer mismatch: expected %s, got %s", address.Hex(), sender.Hex())
+	}
+	return signed, nil
+}
+
+// ledgerExchange performs a data exchange with the Ledger wallet, sending it a
+// message and retrieving the response.
+//
+// The common transport header is defined as follows:
+//
+//  Description                           | Length
+//  --------------------------------------+----------
+//  Communication channel ID (big endian) | 2 bytes
+//  Command tag                           | 1 byte
+//  Packet sequence index (big endian)    | 2 bytes
+//  Payload                               | arbitrary
+//
+// The Communication channel ID allows commands multiplexing over the same
+// physical link. It is not used for the time being, and should be set to 0101
+// to avoid compatibility issues with implementations ignoring a leading 00 byte.
+//
+// The Command tag describes the message content. Use TAG_APDU (0x05) for standard
+// APDU payloads, or TAG_PING (0x02) for a simple link test.
+//
+// The Packet sequence index describes the current sequence for fragmented payloads.
+// The first fragment index is 0x00.
+//
+// APDU Command payloads are encoded as follows:
+//
+//  Description              | Length
+//  -----------------------------------
+//  APDU length (big endian) | 2 bytes
+//  APDU CLA                 | 1 byte
+//  APDU INS                 | 1 byte
+//  APDU P1                  | 1 byte
+//  APDU P2                  | 1 byte
+//  APDU length              | 1 byte
+//  Optional APDU data       | arbitrary
+func (w *ledgerWallet) ledgerExchange(opcode ledgerOpcode, p1 ledgerParam1, p2 ledgerParam2, data []byte) ([]byte, error) {
+	// Construct the message payload, possibly split into multiple chunks
+	apdu := make([]byte, 2, 7+len(data))
+
+	binary.BigEndian.PutUint16(apdu, uint16(5+len(data)))
+	apdu = append(apdu, []byte{0xe0, byte(opcode), byte(p1), byte(p2), byte(len(data))}...)
+	apdu = append(apdu, data...)
+
+	// Stream all the chunks to the device
+	header := []byte{0x01, 0x01, 0x05, 0x00, 0x00} // Channel ID and command tag appended
+	chunk := make([]byte, 64)
+	space := len(chunk) - len(header)
+
+	for i := 0; len(apdu) > 0; i++ {
+		// Construct the new message to stream
+		chunk = append(chunk[:0], header...)
+		binary.BigEndian.PutUint16(chunk[3:], uint16(i))
+
+		if len(apdu) > space {
+			chunk = append(chunk, apdu[:space]...)
+			apdu = apdu[space:]
+		} else {
+			chunk = append(chunk, apdu...)
+			apdu = nil
+		}
+		// Send over to the device
+		if glog.V(logger.Detail) {
+			glog.Infof("-> %03d.%03d: %x", w.device.Bus, w.device.Address, chunk)
+		}
+		if _, err := w.input.Write(chunk); err != nil {
+			return nil, err
+		}
+	}
+	// Stream the reply back from the wallet in 64 byte chunks
+	var reply []byte
+	chunk = chunk[:64] // Yeah, we surely have enough space
+	for {
+		// Read the next chunk from the Ledger wallet
+		if _, err := io.ReadFull(w.output, chunk); err != nil {
+			return nil, err
+		}
+		if glog.V(logger.Detail) {
+			glog.Infof("<- %03d.%03d: %x", w.device.Bus, w.device.Address, chunk)
+		}
+		// Make sure the transport header matches
+		if chunk[0] != 0x01 || chunk[1] != 0x01 || chunk[2] != 0x05 {
+			return nil, errReplyInvalidHeader
+		}
+		// If it's the first chunk, retrieve the total message length
+		var payload []byte
+
+		if chunk[3] == 0x00 && chunk[4] == 0x00 {
+			reply = make([]byte, 0, int(binary.BigEndian.Uint16(chunk[5:7])))
+			payload = chunk[7:]
+		} else {
+			payload = chunk[5:]
+		}
+		// Append to the reply and stop when filled up
+		if left := cap(reply) - len(reply); left > len(payload) {
+			reply = append(reply, payload...)
+		} else {
+			reply = append(reply, payload[:left]...)
+			break
+		}
+	}
+	return reply[:len(reply)-2], nil
+}
diff --git a/accounts/usbwallet/usbwallet.go b/accounts/usbwallet/usbwallet.go
new file mode 100644
index 000000000..3989f3d02
--- /dev/null
+++ b/accounts/usbwallet/usbwallet.go
@@ -0,0 +1,29 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+// +build !ios
+
+// Package usbwallet implements support for USB hardware wallets.
+package usbwallet
+
+import "github.com/karalabe/gousb/usb"
+
+// deviceID is a combined vendor/product identifier to uniquely identify a USB
+// hardware device.
+type deviceID struct {
+	Vendor  usb.ID // The Vendor identifer
+	Product usb.ID // The Product identifier
+}
diff --git a/accounts/usbwallet/usbwallet_ios.go b/accounts/usbwallet/usbwallet_ios.go
new file mode 100644
index 000000000..17d342903
--- /dev/null
+++ b/accounts/usbwallet/usbwallet_ios.go
@@ -0,0 +1,38 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+// This file contains the implementation for interacting with the Ledger hardware
+// wallets. The wire protocol spec can be found in the Ledger Blue GitHub repo:
+// https://raw.githubusercontent.com/LedgerHQ/blue-app-eth/master/doc/ethapp.asc
+
+// +build ios
+
+package usbwallet
+
+import (
+	"errors"
+
+	"github.com/ethereum/go-ethereum/accounts"
+)
+
+// Here be dragons! There is no USB support on iOS.
+
+// ErrIOSNotSupported is returned for all USB hardware backends on iOS.
+var ErrIOSNotSupported = errors.New("no USB support on iOS")
+
+func NewLedgerHub() (accounts.Backend, error) {
+	return nil, ErrIOSNotSupported
+}
diff --git a/build/ci.go b/build/ci.go
index 51540f9b6..d8c76567c 100644
--- a/build/ci.go
+++ b/build/ci.go
@@ -236,6 +236,14 @@ func goToolArch(arch string, subcmd string, args ...string) *exec.Cmd {
 	gocmd := filepath.Join(runtime.GOROOT(), "bin", "go")
 	cmd := exec.Command(gocmd, subcmd)
 	cmd.Args = append(cmd.Args, args...)
+
+	if subcmd == "build" || subcmd == "install" || subcmd == "test" {
+		// Go CGO has a Windows linker error prior to 1.8 (https://github.com/golang/go/issues/8756).
+		// Work around issue by allowing multiple definitions for <1.8 builds.
+		if runtime.GOOS == "windows" && runtime.Version() < "go1.8" {
+			cmd.Args = append(cmd.Args, []string{"-ldflags", "-extldflags -Wl,--allow-multiple-definition"}...)
+		}
+	}
 	cmd.Env = []string{
 		"GO15VENDOREXPERIMENT=1",
 		"GOPATH=" + build.GOPATH(),
diff --git a/cmd/geth/accountcmd.go b/cmd/geth/accountcmd.go
index 237af99eb..cd398eadb 100644
--- a/cmd/geth/accountcmd.go
+++ b/cmd/geth/accountcmd.go
@@ -21,6 +21,7 @@ import (
 	"io/ioutil"
 
 	"github.com/ethereum/go-ethereum/accounts"
+	"github.com/ethereum/go-ethereum/accounts/keystore"
 	"github.com/ethereum/go-ethereum/cmd/utils"
 	"github.com/ethereum/go-ethereum/console"
 	"github.com/ethereum/go-ethereum/crypto"
@@ -180,31 +181,36 @@ nodes.
 
 func accountList(ctx *cli.Context) error {
 	stack := utils.MakeNode(ctx, clientIdentifier, gitCommit)
-	for i, acct := range stack.AccountManager().Accounts() {
-		fmt.Printf("Account #%d: {%x} %s\n", i, acct.Address, acct.File)
+
+	var index int
+	for _, wallet := range stack.AccountManager().Wallets() {
+		for _, account := range wallet.Accounts() {
+			fmt.Printf("Account #%d: {%x} %s\n", index, account.Address, &account.URL)
+			index++
+		}
 	}
 	return nil
 }
 
 // tries unlocking the specified account a few times.
-func unlockAccount(ctx *cli.Context, accman *accounts.Manager, address string, i int, passwords []string) (accounts.Account, string) {
-	account, err := utils.MakeAddress(accman, address)
+func unlockAccount(ctx *cli.Context, ks *keystore.KeyStore, address string, i int, passwords []string) (accounts.Account, string) {
+	account, err := utils.MakeAddress(ks, address)
 	if err != nil {
 		utils.Fatalf("Could not list accounts: %v", err)
 	}
 	for trials := 0; trials < 3; trials++ {
 		prompt := fmt.Sprintf("Unlocking account %s | Attempt %d/%d", address, trials+1, 3)
 		password := getPassPhrase(prompt, false, i, passwords)
-		err = accman.Unlock(account, password)
+		err = ks.Unlock(account, password)
 		if err == nil {
 			glog.V(logger.Info).Infof("Unlocked account %x", account.Address)
 			return account, password
 		}
-		if err, ok := err.(*accounts.AmbiguousAddrError); ok {
+		if err, ok := err.(*keystore.AmbiguousAddrError); ok {
 			glog.V(logger.Info).Infof("Unlocked account %x", account.Address)
-			return ambiguousAddrRecovery(accman, err, password), password
+			return ambiguousAddrRecovery(ks, err, password), password
 		}
-		if err != accounts.ErrDecrypt {
+		if err != keystore.ErrDecrypt {
 			// No need to prompt again if the error is not decryption-related.
 			break
 		}
@@ -244,15 +250,15 @@ func getPassPhrase(prompt string, confirmation bool, i int, passwords []string)
 	return password
 }
 
-func ambiguousAddrRecovery(am *accounts.Manager, err *accounts.AmbiguousAddrError, auth string) accounts.Account {
+func ambiguousAddrRecovery(ks *keystore.KeyStore, err *keystore.AmbiguousAddrError, auth string) accounts.Account {
 	fmt.Printf("Multiple key files exist for address %x:\n", err.Addr)
 	for _, a := range err.Matches {
-		fmt.Println("  ", a.File)
+		fmt.Println("  ", a.URL)
 	}
 	fmt.Println("Testing your passphrase against all of them...")
 	var match *accounts.Account
 	for _, a := range err.Matches {
-		if err := am.Unlock(a, auth); err == nil {
+		if err := ks.Unlock(a, auth); err == nil {
 			match = &a
 			break
 		}
@@ -260,11 +266,11 @@ func ambiguousAddrRecovery(am *accounts.Manager, err *accounts.AmbiguousAddrErro
 	if match == nil {
 		utils.Fatalf("None of the listed files could be unlocked.")
 	}
-	fmt.Printf("Your passphrase unlocked %s\n", match.File)
+	fmt.Printf("Your passphrase unlocked %s\n", match.URL)
 	fmt.Println("In order to avoid this warning, you need to remove the following duplicate key files:")
 	for _, a := range err.Matches {
 		if a != *match {
-			fmt.Println("  ", a.File)
+			fmt.Println("  ", a.URL)
 		}
 	}
 	return *match
@@ -275,7 +281,8 @@ func accountCreate(ctx *cli.Context) error {
 	stack := utils.MakeNode(ctx, clientIdentifier, gitCommit)
 	password := getPassPhrase("Your new account is locked with a password. Please give a password. Do not forget this password.", true, 0, utils.MakePasswordList(ctx))
 
-	account, err := stack.AccountManager().NewAccount(password)
+	ks := stack.AccountManager().Backends(keystore.KeyStoreType)[0].(*keystore.KeyStore)
+	account, err := ks.NewAccount(password)
 	if err != nil {
 		utils.Fatalf("Failed to create account: %v", err)
 	}
@@ -290,9 +297,11 @@ func accountUpdate(ctx *cli.Context) error {
 		utils.Fatalf("No accounts specified to update")
 	}
 	stack := utils.MakeNode(ctx, clientIdentifier, gitCommit)
-	account, oldPassword := unlockAccount(ctx, stack.AccountManager(), ctx.Args().First(), 0, nil)
+	ks := stack.AccountManager().Backends(keystore.KeyStoreType)[0].(*keystore.KeyStore)
+
+	account, oldPassword := unlockAccount(ctx, ks, ctx.Args().First(), 0, nil)
 	newPassword := getPassPhrase("Please give a new password. Do not forget this password.", true, 0, nil)
-	if err := stack.AccountManager().Update(account, oldPassword, newPassword); err != nil {
+	if err := ks.Update(account, oldPassword, newPassword); err != nil {
 		utils.Fatalf("Could not update the account: %v", err)
 	}
 	return nil
@@ -310,7 +319,9 @@ func importWallet(ctx *cli.Context) error {
 
 	stack := utils.MakeNode(ctx, clientIdentifier, gitCommit)
 	passphrase := getPassPhrase("", false, 0, utils.MakePasswordList(ctx))
-	acct, err := stack.AccountManager().ImportPreSaleKey(keyJson, passphrase)
+
+	ks := stack.AccountManager().Backends(keystore.KeyStoreType)[0].(*keystore.KeyStore)
+	acct, err := ks.ImportPreSaleKey(keyJson, passphrase)
 	if err != nil {
 		utils.Fatalf("%v", err)
 	}
@@ -329,7 +340,9 @@ func accountImport(ctx *cli.Context) error {
 	}
 	stack := utils.MakeNode(ctx, clientIdentifier, gitCommit)
 	passphrase := getPassPhrase("Your new account is locked with a password. Please give a password. Do not forget this password.", true, 0, utils.MakePasswordList(ctx))
-	acct, err := stack.AccountManager().ImportECDSA(key, passphrase)
+
+	ks := stack.AccountManager().Backends(keystore.KeyStoreType)[0].(*keystore.KeyStore)
+	acct, err := ks.ImportECDSA(key, passphrase)
 	if err != nil {
 		utils.Fatalf("Could not create the account: %v", err)
 	}
diff --git a/cmd/geth/accountcmd_test.go b/cmd/geth/accountcmd_test.go
index 113df983e..679a7ec30 100644
--- a/cmd/geth/accountcmd_test.go
+++ b/cmd/geth/accountcmd_test.go
@@ -35,7 +35,7 @@ import (
 func tmpDatadirWithKeystore(t *testing.T) string {
 	datadir := tmpdir(t)
 	keystore := filepath.Join(datadir, "keystore")
-	source := filepath.Join("..", "..", "accounts", "testdata", "keystore")
+	source := filepath.Join("..", "..", "accounts", "keystore", "testdata", "keystore")
 	if err := cp.CopyAll(keystore, source); err != nil {
 		t.Fatal(err)
 	}
@@ -53,15 +53,15 @@ func TestAccountList(t *testing.T) {
 	defer geth.expectExit()
 	if runtime.GOOS == "windows" {
 		geth.expect(`
-Account #0: {7ef5a6135f1fd6a02593eedc869c6d41d934aef8} {{.Datadir}}\keystore\UTC--2016-03-22T12-57-55.920751759Z--7ef5a6135f1fd6a02593eedc869c6d41d934aef8
-Account #1: {f466859ead1932d743d622cb74fc058882e8648a} {{.Datadir}}\keystore\aaa
-Account #2: {289d485d9771714cce91d3393d764e1311907acc} {{.Datadir}}\keystore\zzz
+Account #0: {7ef5a6135f1fd6a02593eedc869c6d41d934aef8} keystore://{{.Datadir}}\keystore\UTC--2016-03-22T12-57-55.920751759Z--7ef5a6135f1fd6a02593eedc869c6d41d934aef8
+Account #1: {f466859ead1932d743d622cb74fc058882e8648a} keystore://{{.Datadir}}\keystore\aaa
+Account #2: {289d485d9771714cce91d3393d764e1311907acc} keystore://{{.Datadir}}\keystore\zzz
 `)
 	} else {
 		geth.expect(`
-Account #0: {7ef5a6135f1fd6a02593eedc869c6d41d934aef8} {{.Datadir}}/keystore/UTC--2016-03-22T12-57-55.920751759Z--7ef5a6135f1fd6a02593eedc869c6d41d934aef8
-Account #1: {f466859ead1932d743d622cb74fc058882e8648a} {{.Datadir}}/keystore/aaa
-Account #2: {289d485d9771714cce91d3393d764e1311907acc} {{.Datadir}}/keystore/zzz
+Account #0: {7ef5a6135f1fd6a02593eedc869c6d41d934aef8} keystore://{{.Datadir}}/keystore/UTC--2016-03-22T12-57-55.920751759Z--7ef5a6135f1fd6a02593eedc869c6d41d934aef8
+Account #1: {f466859ead1932d743d622cb74fc058882e8648a} keystore://{{.Datadir}}/keystore/aaa
+Account #2: {289d485d9771714cce91d3393d764e1311907acc} keystore://{{.Datadir}}/keystore/zzz
 `)
 	}
 }
@@ -230,7 +230,7 @@ Fatal: Failed to unlock account 0 (could not decrypt key with given passphrase)
 }
 
 func TestUnlockFlagAmbiguous(t *testing.T) {
-	store := filepath.Join("..", "..", "accounts", "testdata", "dupes")
+	store := filepath.Join("..", "..", "accounts", "keystore", "testdata", "dupes")
 	geth := runGeth(t,
 		"--keystore", store, "--nat", "none", "--nodiscover", "--dev",
 		"--unlock", "f466859ead1932d743d622cb74fc058882e8648a",
@@ -247,12 +247,12 @@ Unlocking account f466859ead1932d743d622cb74fc058882e8648a | Attempt 1/3
 !! Unsupported terminal, password will be echoed.
 Passphrase: {{.InputLine "foobar"}}
 Multiple key files exist for address f466859ead1932d743d622cb74fc058882e8648a:
-   {{keypath "1"}}
-   {{keypath "2"}}
+   keystore://{{keypath "1"}}
+   keystore://{{keypath "2"}}
 Testing your passphrase against all of them...
-Your passphrase unlocked {{keypath "1"}}
+Your passphrase unlocked keystore://{{keypath "1"}}
 In order to avoid this warning, you need to remove the following duplicate key files:
-   {{keypath "2"}}
+   keystore://{{keypath "2"}}
 `)
 	geth.expectExit()
 
@@ -267,7 +267,7 @@ In order to avoid this warning, you need to remove the following duplicate key f
 }
 
 func TestUnlockFlagAmbiguousWrongPassword(t *testing.T) {
-	store := filepath.Join("..", "..", "accounts", "testdata", "dupes")
+	store := filepath.Join("..", "..", "accounts", "keystore", "testdata", "dupes")
 	geth := runGeth(t,
 		"--keystore", store, "--nat", "none", "--nodiscover", "--dev",
 		"--unlock", "f466859ead1932d743d622cb74fc058882e8648a")
@@ -283,8 +283,8 @@ Unlocking account f466859ead1932d743d622cb74fc058882e8648a | Attempt 1/3
 !! Unsupported terminal, password will be echoed.
 Passphrase: {{.InputLine "wrong"}}
 Multiple key files exist for address f466859ead1932d743d622cb74fc058882e8648a:
-   {{keypath "1"}}
-   {{keypath "2"}}
+   keystore://{{keypath "1"}}
+   keystore://{{keypath "2"}}
 Testing your passphrase against all of them...
 Fatal: None of the listed files could be unlocked.
 `)
diff --git a/cmd/geth/main.go b/cmd/geth/main.go
index d7e4cc7b5..c19770bfa 100644
--- a/cmd/geth/main.go
+++ b/cmd/geth/main.go
@@ -25,11 +25,14 @@ import (
 	"strings"
 	"time"
 
+	"github.com/ethereum/go-ethereum/accounts"
+	"github.com/ethereum/go-ethereum/accounts/keystore"
 	"github.com/ethereum/go-ethereum/cmd/utils"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/console"
 	"github.com/ethereum/go-ethereum/contracts/release"
 	"github.com/ethereum/go-ethereum/eth"
+	"github.com/ethereum/go-ethereum/ethclient"
 	"github.com/ethereum/go-ethereum/internal/debug"
 	"github.com/ethereum/go-ethereum/logger"
 	"github.com/ethereum/go-ethereum/logger/glog"
@@ -245,14 +248,50 @@ func startNode(ctx *cli.Context, stack *node.Node) {
 	utils.StartNode(stack)
 
 	// Unlock any account specifically requested
-	accman := stack.AccountManager()
+	ks := stack.AccountManager().Backends(keystore.KeyStoreType)[0].(*keystore.KeyStore)
+
 	passwords := utils.MakePasswordList(ctx)
-	accounts := strings.Split(ctx.GlobalString(utils.UnlockedAccountFlag.Name), ",")
-	for i, account := range accounts {
+	unlocks := strings.Split(ctx.GlobalString(utils.UnlockedAccountFlag.Name), ",")
+	for i, account := range unlocks {
 		if trimmed := strings.TrimSpace(account); trimmed != "" {
-			unlockAccount(ctx, accman, trimmed, i, passwords)
+			unlockAccount(ctx, ks, trimmed, i, passwords)
 		}
 	}
+	// Register wallet event handlers to open and auto-derive wallets
+	events := make(chan accounts.WalletEvent, 16)
+	stack.AccountManager().Subscribe(events)
+
+	go func() {
+		// Create an chain state reader for self-derivation
+		rpcClient, err := stack.Attach()
+		if err != nil {
+			utils.Fatalf("Failed to attach to self: %v", err)
+		}
+		stateReader := ethclient.NewClient(rpcClient)
+
+		// Open and self derive any wallets already attached
+		for _, wallet := range stack.AccountManager().Wallets() {
+			if err := wallet.Open(""); err != nil {
+				glog.V(logger.Warn).Infof("Failed to open wallet %s: %v", wallet.URL(), err)
+			} else {
+				wallet.SelfDerive(accounts.DefaultBaseDerivationPath, stateReader)
+			}
+		}
+		// Listen for wallet event till termination
+		for event := range events {
+			if event.Arrive {
+				if err := event.Wallet.Open(""); err != nil {
+					glog.V(logger.Info).Infof("New wallet appeared: %s, failed to open: %s", event.Wallet.URL(), err)
+				} else {
+					glog.V(logger.Info).Infof("New wallet appeared: %s, %s", event.Wallet.URL(), event.Wallet.Status())
+					event.Wallet.SelfDerive(accounts.DefaultBaseDerivationPath, stateReader)
+				}
+			} else {
+				glog.V(logger.Info).Infof("Old wallet dropped:  %s", event.Wallet.URL())
+				event.Wallet.Close()
+			}
+		}
+	}()
 	// Start auxiliary services if enabled
 	if ctx.GlobalBool(utils.MiningEnabledFlag.Name) {
 		var ethereum *eth.Ethereum
diff --git a/cmd/gethrpctest/main.go b/cmd/gethrpctest/main.go
index 850bf8eb2..9e80ad05d 100644
--- a/cmd/gethrpctest/main.go
+++ b/cmd/gethrpctest/main.go
@@ -23,6 +23,7 @@ import (
 	"os"
 	"os/signal"
 
+	"github.com/ethereum/go-ethereum/accounts/keystore"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/eth"
 	"github.com/ethereum/go-ethereum/ethdb"
@@ -99,17 +100,18 @@ func MakeSystemNode(privkey string, test *tests.BlockTest) (*node.Node, error) {
 		return nil, err
 	}
 	// Create the keystore and inject an unlocked account if requested
-	accman := stack.AccountManager()
+	ks := stack.AccountManager().Backends(keystore.KeyStoreType)[0].(*keystore.KeyStore)
+
 	if len(privkey) > 0 {
 		key, err := crypto.HexToECDSA(privkey)
 		if err != nil {
 			return nil, err
 		}
-		a, err := accman.ImportECDSA(key, "")
+		a, err := ks.ImportECDSA(key, "")
 		if err != nil {
 			return nil, err
 		}
-		if err := accman.Unlock(a, ""); err != nil {
+		if err := ks.Unlock(a, ""); err != nil {
 			return nil, err
 		}
 	}
diff --git a/cmd/swarm/main.go b/cmd/swarm/main.go
index 7d76d55c1..14adc3b10 100644
--- a/cmd/swarm/main.go
+++ b/cmd/swarm/main.go
@@ -26,6 +26,7 @@ import (
 	"strings"
 
 	"github.com/ethereum/go-ethereum/accounts"
+	"github.com/ethereum/go-ethereum/accounts/keystore"
 	"github.com/ethereum/go-ethereum/cmd/utils"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/console"
@@ -336,29 +337,36 @@ func getAccount(ctx *cli.Context, stack *node.Node) *ecdsa.PrivateKey {
 		return key
 	}
 	// Otherwise try getting it from the keystore.
-	return decryptStoreAccount(stack.AccountManager(), keyid)
+	am := stack.AccountManager()
+	ks := am.Backends(keystore.KeyStoreType)[0].(*keystore.KeyStore)
+
+	return decryptStoreAccount(ks, keyid)
 }
 
-func decryptStoreAccount(accman *accounts.Manager, account string) *ecdsa.PrivateKey {
+func decryptStoreAccount(ks *keystore.KeyStore, account string) *ecdsa.PrivateKey {
 	var a accounts.Account
 	var err error
 	if common.IsHexAddress(account) {
-		a, err = accman.Find(accounts.Account{Address: common.HexToAddress(account)})
-	} else if ix, ixerr := strconv.Atoi(account); ixerr == nil {
-		a, err = accman.AccountByIndex(ix)
+		a, err = ks.Find(accounts.Account{Address: common.HexToAddress(account)})
+	} else if ix, ixerr := strconv.Atoi(account); ixerr == nil && ix > 0 {
+		if accounts := ks.Accounts(); len(accounts) > ix {
+			a = accounts[ix]
+		} else {
+			err = fmt.Errorf("index %d higher than number of accounts %d", ix, len(accounts))
+		}
 	} else {
 		utils.Fatalf("Can't find swarm account key %s", account)
 	}
 	if err != nil {
 		utils.Fatalf("Can't find swarm account key: %v", err)
 	}
-	keyjson, err := ioutil.ReadFile(a.File)
+	keyjson, err := ioutil.ReadFile(a.URL.Path)
 	if err != nil {
 		utils.Fatalf("Can't load swarm account key: %v", err)
 	}
 	for i := 1; i <= 3; i++ {
 		passphrase := promptPassphrase(fmt.Sprintf("Unlocking swarm account %s [%d/3]", a.Address.Hex(), i))
-		key, err := accounts.DecryptKey(keyjson, passphrase)
+		key, err := keystore.DecryptKey(keyjson, passphrase)
 		if err == nil {
 			return key.PrivateKey
 		}
diff --git a/cmd/utils/flags.go b/cmd/utils/flags.go
index 9ba33df80..92eb05e32 100644
--- a/cmd/utils/flags.go
+++ b/cmd/utils/flags.go
@@ -30,6 +30,7 @@ import (
 
 	"github.com/ethereum/ethash"
 	"github.com/ethereum/go-ethereum/accounts"
+	"github.com/ethereum/go-ethereum/accounts/keystore"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/state"
@@ -587,23 +588,27 @@ func MakeDatabaseHandles() int {
 
 // MakeAddress converts an account specified directly as a hex encoded string or
 // a key index in the key store to an internal account representation.
-func MakeAddress(accman *accounts.Manager, account string) (accounts.Account, error) {
+func MakeAddress(ks *keystore.KeyStore, account string) (accounts.Account, error) {
 	// If the specified account is a valid address, return it
 	if common.IsHexAddress(account) {
 		return accounts.Account{Address: common.HexToAddress(account)}, nil
 	}
 	// Otherwise try to interpret the account as a keystore index
 	index, err := strconv.Atoi(account)
-	if err != nil {
+	if err != nil || index < 0 {
 		return accounts.Account{}, fmt.Errorf("invalid account address or index %q", account)
 	}
-	return accman.AccountByIndex(index)
+	accs := ks.Accounts()
+	if len(accs) <= index {
+		return accounts.Account{}, fmt.Errorf("index %d higher than number of accounts %d", index, len(accs))
+	}
+	return accs[index], nil
 }
 
 // MakeEtherbase retrieves the etherbase either from the directly specified
 // command line flags or from the keystore if CLI indexed.
-func MakeEtherbase(accman *accounts.Manager, ctx *cli.Context) common.Address {
-	accounts := accman.Accounts()
+func MakeEtherbase(ks *keystore.KeyStore, ctx *cli.Context) common.Address {
+	accounts := ks.Accounts()
 	if !ctx.GlobalIsSet(EtherbaseFlag.Name) && len(accounts) == 0 {
 		glog.V(logger.Error).Infoln("WARNING: No etherbase set and no accounts found as default")
 		return common.Address{}
@@ -613,7 +618,7 @@ func MakeEtherbase(accman *accounts.Manager, ctx *cli.Context) common.Address {
 		return common.Address{}
 	}
 	// If the specified etherbase is a valid address, return it
-	account, err := MakeAddress(accman, etherbase)
+	account, err := MakeAddress(ks, etherbase)
 	if err != nil {
 		Fatalf("Option %q: %v", EtherbaseFlag.Name, err)
 	}
@@ -721,9 +726,10 @@ func RegisterEthService(ctx *cli.Context, stack *node.Node, extra []byte) {
 	if networks > 1 {
 		Fatalf("The %v flags are mutually exclusive", netFlags)
 	}
+	ks := stack.AccountManager().Backends(keystore.KeyStoreType)[0].(*keystore.KeyStore)
 
 	ethConf := &eth.Config{
-		Etherbase:               MakeEtherbase(stack.AccountManager(), ctx),
+		Etherbase:               MakeEtherbase(ks, ctx),
 		ChainConfig:             MakeChainConfig(ctx, stack),
 		FastSync:                ctx.GlobalBool(FastSyncFlag.Name),
 		LightMode:               ctx.GlobalBool(LightModeFlag.Name),
diff --git a/eth/backend.go b/eth/backend.go
index af120cbad..ef3ac93c8 100644
--- a/eth/backend.go
+++ b/eth/backend.go
@@ -361,15 +361,15 @@ func (s *Ethereum) ResetWithGenesisBlock(gb *types.Block) {
 }
 
 func (s *Ethereum) Etherbase() (eb common.Address, err error) {
-	eb = s.etherbase
-	if (eb == common.Address{}) {
-		firstAccount, err := s.AccountManager().AccountByIndex(0)
-		eb = firstAccount.Address
-		if err != nil {
-			return eb, fmt.Errorf("etherbase address must be explicitly specified")
+	if s.etherbase != (common.Address{}) {
+		return s.etherbase, nil
+	}
+	if wallets := s.AccountManager().Wallets(); len(wallets) > 0 {
+		if accounts := wallets[0].Accounts(); len(accounts) > 0 {
+			return accounts[0].Address, nil
 		}
 	}
-	return eb, nil
+	return common.Address{}, fmt.Errorf("etherbase address must be explicitly specified")
 }
 
 // set in js console via admin interface or wrapper from cli flags
diff --git a/internal/ethapi/api.go b/internal/ethapi/api.go
index 4c8e784c5..f49434e17 100644
--- a/internal/ethapi/api.go
+++ b/internal/ethapi/api.go
@@ -28,6 +28,7 @@ import (
 
 	"github.com/ethereum/ethash"
 	"github.com/ethereum/go-ethereum/accounts"
+	"github.com/ethereum/go-ethereum/accounts/keystore"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/ethereum/go-ethereum/core"
@@ -187,8 +188,14 @@ func NewPublicAccountAPI(am *accounts.Manager) *PublicAccountAPI {
 }
 
 // Accounts returns the collection of accounts this node manages
-func (s *PublicAccountAPI) Accounts() []accounts.Account {
-	return s.am.Accounts()
+func (s *PublicAccountAPI) Accounts() []common.Address {
+	var addresses []common.Address
+	for _, wallet := range s.am.Wallets() {
+		for _, account := range wallet.Accounts() {
+			addresses = append(addresses, account.Address)
+		}
+	}
+	return addresses
 }
 
 // PrivateAccountAPI provides an API to access accounts managed by this node.
@@ -209,23 +216,67 @@ func NewPrivateAccountAPI(b Backend) *PrivateAccountAPI {
 
 // ListAccounts will return a list of addresses for accounts this node manages.
 func (s *PrivateAccountAPI) ListAccounts() []common.Address {
-	accounts := s.am.Accounts()
-	addresses := make([]common.Address, len(accounts))
-	for i, acc := range accounts {
-		addresses[i] = acc.Address
+	var addresses []common.Address
+	for _, wallet := range s.am.Wallets() {
+		for _, account := range wallet.Accounts() {
+			addresses = append(addresses, account.Address)
+		}
 	}
 	return addresses
 }
 
+// rawWallet is a JSON representation of an accounts.Wallet interface, with its
+// data contents extracted into plain fields.
+type rawWallet struct {
+	URL      string             `json:"url"`
+	Status   string             `json:"status"`
+	Accounts []accounts.Account `json:"accounts"`
+}
+
+// ListWallets will return a list of wallets this node manages.
+func (s *PrivateAccountAPI) ListWallets() []rawWallet {
+	var wallets []rawWallet
+	for _, wallet := range s.am.Wallets() {
+		wallets = append(wallets, rawWallet{
+			URL:      wallet.URL().String(),
+			Status:   wallet.Status(),
+			Accounts: wallet.Accounts(),
+		})
+	}
+	return wallets
+}
+
+// DeriveAccount requests a HD wallet to derive a new account, optionally pinning
+// it for later reuse.
+func (s *PrivateAccountAPI) DeriveAccount(url string, path string, pin *bool) (accounts.Account, error) {
+	wallet, err := s.am.Wallet(url)
+	if err != nil {
+		return accounts.Account{}, err
+	}
+	derivPath, err := accounts.ParseDerivationPath(path)
+	if err != nil {
+		return accounts.Account{}, err
+	}
+	if pin == nil {
+		pin = new(bool)
+	}
+	return wallet.Derive(derivPath, *pin)
+}
+
 // NewAccount will create a new account and returns the address for the new account.
 func (s *PrivateAccountAPI) NewAccount(password string) (common.Address, error) {
-	acc, err := s.am.NewAccount(password)
+	acc, err := fetchKeystore(s.am).NewAccount(password)
 	if err == nil {
 		return acc.Address, nil
 	}
 	return common.Address{}, err
 }
 
+// fetchKeystore retrives the encrypted keystore from the account manager.
+func fetchKeystore(am *accounts.Manager) *keystore.KeyStore {
+	return am.Backends(keystore.KeyStoreType)[0].(*keystore.KeyStore)
+}
+
 // ImportRawKey stores the given hex encoded ECDSA key into the key directory,
 // encrypting it with the passphrase.
 func (s *PrivateAccountAPI) ImportRawKey(privkey string, password string) (common.Address, error) {
@@ -234,7 +285,7 @@ func (s *PrivateAccountAPI) ImportRawKey(privkey string, password string) (commo
 		return common.Address{}, err
 	}
 
-	acc, err := s.am.ImportECDSA(crypto.ToECDSA(hexkey), password)
+	acc, err := fetchKeystore(s.am).ImportECDSA(crypto.ToECDSA(hexkey), password)
 	return acc.Address, err
 }
 
@@ -251,30 +302,42 @@ func (s *PrivateAccountAPI) UnlockAccount(addr common.Address, password string,
 	} else {
 		d = time.Duration(*duration) * time.Second
 	}
-	err := s.am.TimedUnlock(accounts.Account{Address: addr}, password, d)
+	err := fetchKeystore(s.am).TimedUnlock(accounts.Account{Address: addr}, password, d)
 	return err == nil, err
 }
 
 // LockAccount will lock the account associated with the given address when it's unlocked.
 func (s *PrivateAccountAPI) LockAccount(addr common.Address) bool {
-	return s.am.Lock(addr) == nil
+	return fetchKeystore(s.am).Lock(addr) == nil
 }
 
 // SendTransaction will create a transaction from the given arguments and
 // tries to sign it with the key associated with args.To. If the given passwd isn't
 // able to decrypt the key it fails.
 func (s *PrivateAccountAPI) SendTransaction(ctx context.Context, args SendTxArgs, passwd string) (common.Hash, error) {
+	// Set some sanity defaults and terminate on failure
 	if err := args.setDefaults(ctx, s.b); err != nil {
 		return common.Hash{}, err
 	}
-	tx := args.toTransaction()
-	signer := types.MakeSigner(s.b.ChainConfig(), s.b.CurrentBlock().Number())
-	signature, err := s.am.SignWithPassphrase(accounts.Account{Address: args.From}, passwd, signer.Hash(tx).Bytes())
+	// Look up the wallet containing the requested signer
+	account := accounts.Account{Address: args.From}
+
+	wallet, err := s.am.Find(account)
 	if err != nil {
 		return common.Hash{}, err
 	}
+	// Assemble the transaction and sign with the wallet
+	tx := args.toTransaction()
 
-	return submitTransaction(ctx, s.b, tx, signature)
+	var chainID *big.Int
+	if config := s.b.ChainConfig(); config.IsEIP155(s.b.CurrentBlock().Number()) {
+		chainID = config.ChainId
+	}
+	signed, err := wallet.SignTxWithPassphrase(account, passwd, tx, chainID)
+	if err != nil {
+		return common.Hash{}, err
+	}
+	return submitTransaction(ctx, s.b, signed)
 }
 
 // signHash is a helper function that calculates a hash for the given message that can be
@@ -299,7 +362,15 @@ func signHash(data []byte) []byte {
 //
 // https://github.com/ethereum/go-ethereum/wiki/Management-APIs#personal_sign
 func (s *PrivateAccountAPI) Sign(ctx context.Context, data hexutil.Bytes, addr common.Address, passwd string) (hexutil.Bytes, error) {
-	signature, err := s.b.AccountManager().SignWithPassphrase(accounts.Account{Address: addr}, passwd, signHash(data))
+	// Look up the wallet containing the requested signer
+	account := accounts.Account{Address: addr}
+
+	wallet, err := s.b.AccountManager().Find(account)
+	if err != nil {
+		return nil, err
+	}
+	// Assemble sign the data with the wallet
+	signature, err := wallet.SignHashWithPassphrase(account, passwd, signHash(data))
 	if err != nil {
 		return nil, err
 	}
@@ -512,16 +583,15 @@ func (s *PublicBlockChainAPI) doCall(ctx context.Context, args CallArgs, blockNr
 	if state == nil || err != nil {
 		return nil, common.Big0, err
 	}
-
 	// Set sender address or use a default if none specified
 	addr := args.From
 	if addr == (common.Address{}) {
-		accounts := s.b.AccountManager().Accounts()
-		if len(accounts) > 0 {
-			addr = accounts[0].Address
+		if wallets := s.b.AccountManager().Wallets(); len(wallets) > 0 {
+			if accounts := wallets[0].Accounts(); len(accounts) > 0 {
+				addr = accounts[0].Address
+			}
 		}
 	}
-
 	// Set default gas & gas price if none were set
 	gas, gasPrice := args.Gas.ToInt(), args.GasPrice.ToInt()
 	if gas.BitLen() == 0 {
@@ -530,7 +600,6 @@ func (s *PublicBlockChainAPI) doCall(ctx context.Context, args CallArgs, blockNr
 	if gasPrice.BitLen() == 0 {
 		gasPrice = new(big.Int).Mul(big.NewInt(50), common.Shannon)
 	}
-
 	// Create new call message
 	msg := types.NewMessage(addr, args.To, 0, args.Value.ToInt(), gas, gasPrice, args.Data, false)
 
@@ -1023,13 +1092,19 @@ func (s *PublicTransactionPoolAPI) GetTransactionReceipt(txHash common.Hash) (ma
 
 // sign is a helper function that signs a transaction with the private key of the given address.
 func (s *PublicTransactionPoolAPI) sign(addr common.Address, tx *types.Transaction) (*types.Transaction, error) {
-	signer := types.MakeSigner(s.b.ChainConfig(), s.b.CurrentBlock().Number())
+	// Look up the wallet containing the requested signer
+	account := accounts.Account{Address: addr}
 
-	signature, err := s.b.AccountManager().Sign(addr, signer.Hash(tx).Bytes())
+	wallet, err := s.b.AccountManager().Find(account)
 	if err != nil {
 		return nil, err
 	}
-	return tx.WithSignature(signer, signature)
+	// Request the wallet to sign the transaction
+	var chainID *big.Int
+	if config := s.b.ChainConfig(); config.IsEIP155(s.b.CurrentBlock().Number()) {
+		chainID = config.ChainId
+	}
+	return wallet.SignTx(account, tx, chainID)
 }
 
 // SendTxArgs represents the arguments to sumbit a new transaction into the transaction pool.
@@ -1076,42 +1151,47 @@ func (args *SendTxArgs) toTransaction() *types.Transaction {
 }
 
 // submitTransaction is a helper function that submits tx to txPool and logs a message.
-func submitTransaction(ctx context.Context, b Backend, tx *types.Transaction, signature []byte) (common.Hash, error) {
-	signer := types.MakeSigner(b.ChainConfig(), b.CurrentBlock().Number())
-
-	signedTx, err := tx.WithSignature(signer, signature)
-	if err != nil {
+func submitTransaction(ctx context.Context, b Backend, tx *types.Transaction) (common.Hash, error) {
+	if err := b.SendTx(ctx, tx); err != nil {
 		return common.Hash{}, err
 	}
-
-	if err := b.SendTx(ctx, signedTx); err != nil {
-		return common.Hash{}, err
-	}
-
-	if signedTx.To() == nil {
-		from, _ := types.Sender(signer, signedTx)
-		addr := crypto.CreateAddress(from, signedTx.Nonce())
-		glog.V(logger.Info).Infof("Tx(%s) created: %s\n", signedTx.Hash().Hex(), addr.Hex())
+	if tx.To() == nil {
+		signer := types.MakeSigner(b.ChainConfig(), b.CurrentBlock().Number())
+		from, _ := types.Sender(signer, tx)
+		addr := crypto.CreateAddress(from, tx.Nonce())
+		glog.V(logger.Info).Infof("Tx(%s) created: %s\n", tx.Hash().Hex(), addr.Hex())
 	} else {
-		glog.V(logger.Info).Infof("Tx(%s) to: %s\n", signedTx.Hash().Hex(), tx.To().Hex())
+		glog.V(logger.Info).Infof("Tx(%s) to: %s\n", tx.Hash().Hex(), tx.To().Hex())
 	}
-
-	return signedTx.Hash(), nil
+	return tx.Hash(), nil
 }
 
 // SendTransaction creates a transaction for the given argument, sign it and submit it to the
 // transaction pool.
 func (s *PublicTransactionPoolAPI) SendTransaction(ctx context.Context, args SendTxArgs) (common.Hash, error) {
+	// Set some sanity defaults and terminate on failure
 	if err := args.setDefaults(ctx, s.b); err != nil {
 		return common.Hash{}, err
 	}
+	// Look up the wallet containing the requested signer
+	account := accounts.Account{Address: args.From}
+
+	wallet, err := s.b.AccountManager().Find(account)
+	if err != nil {
+		return common.Hash{}, err
+	}
+	// Assemble the transaction and sign with the wallet
 	tx := args.toTransaction()
-	signer := types.MakeSigner(s.b.ChainConfig(), s.b.CurrentBlock().Number())
-	signature, err := s.b.AccountManager().Sign(args.From, signer.Hash(tx).Bytes())
+
+	var chainID *big.Int
+	if config := s.b.ChainConfig(); config.IsEIP155(s.b.CurrentBlock().Number()) {
+		chainID = config.ChainId
+	}
+	signed, err := wallet.SignTx(account, tx, chainID)
 	if err != nil {
 		return common.Hash{}, err
 	}
-	return submitTransaction(ctx, s.b, tx, signature)
+	return submitTransaction(ctx, s.b, signed)
 }
 
 // SendRawTransaction will add the signed transaction to the transaction pool.
@@ -1151,7 +1231,15 @@ func (s *PublicTransactionPoolAPI) SendRawTransaction(ctx context.Context, encod
 //
 // https://github.com/ethereum/wiki/wiki/JSON-RPC#eth_sign
 func (s *PublicTransactionPoolAPI) Sign(addr common.Address, data hexutil.Bytes) (hexutil.Bytes, error) {
-	signature, err := s.b.AccountManager().Sign(addr, signHash(data))
+	// Look up the wallet containing the requested signer
+	account := accounts.Account{Address: addr}
+
+	wallet, err := s.b.AccountManager().Find(account)
+	if err != nil {
+		return nil, err
+	}
+	// Sign the requested hash with the wallet
+	signature, err := wallet.SignHash(account, signHash(data))
 	if err == nil {
 		signature[64] += 27 // Transform V from 0/1 to 27/28 according to the yellow paper
 	}
@@ -1197,7 +1285,7 @@ func (s *PublicTransactionPoolAPI) PendingTransactions() ([]*RPCTransaction, err
 			signer = types.NewEIP155Signer(tx.ChainId())
 		}
 		from, _ := types.Sender(signer, tx)
-		if s.b.AccountManager().HasAddress(from) {
+		if _, err := s.b.AccountManager().Find(accounts.Account{Address: from}); err == nil {
 			transactions = append(transactions, newRPCPendingTransaction(tx))
 		}
 	}
diff --git a/internal/guide/guide_test.go b/internal/guide/guide_test.go
index 8f89037bd..9c7ad16d1 100644
--- a/internal/guide/guide_test.go
+++ b/internal/guide/guide_test.go
@@ -24,13 +24,14 @@ package guide
 
 import (
 	"io/ioutil"
+	"math/big"
 	"os"
 	"path/filepath"
 	"testing"
 	"time"
 
-	"github.com/ethereum/go-ethereum/accounts"
-	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/accounts/keystore"
+	"github.com/ethereum/go-ethereum/core/types"
 )
 
 // Tests that the account management snippets work correctly.
@@ -42,59 +43,59 @@ func TestAccountManagement(t *testing.T) {
 	}
 	defer os.RemoveAll(workdir)
 
-	// Create an encrypted keystore manager with standard crypto parameters
-	am := accounts.NewManager(filepath.Join(workdir, "keystore"), accounts.StandardScryptN, accounts.StandardScryptP)
+	// Create an encrypted keystore with standard crypto parameters
+	ks := keystore.NewKeyStore(filepath.Join(workdir, "keystore"), keystore.StandardScryptN, keystore.StandardScryptP)
 
 	// Create a new account with the specified encryption passphrase
-	newAcc, err := am.NewAccount("Creation password")
+	newAcc, err := ks.NewAccount("Creation password")
 	if err != nil {
 		t.Fatalf("Failed to create new account: %v", err)
 	}
 	// Export the newly created account with a different passphrase. The returned
 	// data from this method invocation is a JSON encoded, encrypted key-file
-	jsonAcc, err := am.Export(newAcc, "Creation password", "Export password")
+	jsonAcc, err := ks.Export(newAcc, "Creation password", "Export password")
 	if err != nil {
 		t.Fatalf("Failed to export account: %v", err)
 	}
 	// Update the passphrase on the account created above inside the local keystore
-	if err := am.Update(newAcc, "Creation password", "Update password"); err != nil {
+	if err := ks.Update(newAcc, "Creation password", "Update password"); err != nil {
 		t.Fatalf("Failed to update account: %v", err)
 	}
 	// Delete the account updated above from the local keystore
-	if err := am.Delete(newAcc, "Update password"); err != nil {
+	if err := ks.Delete(newAcc, "Update password"); err != nil {
 		t.Fatalf("Failed to delete account: %v", err)
 	}
 	// Import back the account we've exported (and then deleted) above with yet
 	// again a fresh passphrase
-	if _, err := am.Import(jsonAcc, "Export password", "Import password"); err != nil {
+	if _, err := ks.Import(jsonAcc, "Export password", "Import password"); err != nil {
 		t.Fatalf("Failed to import account: %v", err)
 	}
 	// Create a new account to sign transactions with
-	signer, err := am.NewAccount("Signer password")
+	signer, err := ks.NewAccount("Signer password")
 	if err != nil {
 		t.Fatalf("Failed to create signer account: %v", err)
 	}
-	txHash := common.HexToHash("0x0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef")
+	tx, chain := new(types.Transaction), big.NewInt(1)
 
 	// Sign a transaction with a single authorization
-	if _, err := am.SignWithPassphrase(signer, "Signer password", txHash.Bytes()); err != nil {
+	if _, err := ks.SignTxWithPassphrase(signer, "Signer password", tx, chain); err != nil {
 		t.Fatalf("Failed to sign with passphrase: %v", err)
 	}
 	// Sign a transaction with multiple manually cancelled authorizations
-	if err := am.Unlock(signer, "Signer password"); err != nil {
+	if err := ks.Unlock(signer, "Signer password"); err != nil {
 		t.Fatalf("Failed to unlock account: %v", err)
 	}
-	if _, err := am.Sign(signer.Address, txHash.Bytes()); err != nil {
+	if _, err := ks.SignTx(signer, tx, chain); err != nil {
 		t.Fatalf("Failed to sign with unlocked account: %v", err)
 	}
-	if err := am.Lock(signer.Address); err != nil {
+	if err := ks.Lock(signer.Address); err != nil {
 		t.Fatalf("Failed to lock account: %v", err)
 	}
 	// Sign a transaction with multiple automatically cancelled authorizations
-	if err := am.TimedUnlock(signer, "Signer password", time.Second); err != nil {
+	if err := ks.TimedUnlock(signer, "Signer password", time.Second); err != nil {
 		t.Fatalf("Failed to time unlock account: %v", err)
 	}
-	if _, err := am.Sign(signer.Address, txHash.Bytes()); err != nil {
+	if _, err := ks.SignTx(signer, tx, chain); err != nil {
 		t.Fatalf("Failed to sign with time unlocked account: %v", err)
 	}
 }
diff --git a/internal/web3ext/web3ext.go b/internal/web3ext/web3ext.go
index edbe45fa3..2012c2517 100644
--- a/internal/web3ext/web3ext.go
+++ b/internal/web3ext/web3ext.go
@@ -448,6 +448,18 @@ web3._extend({
 			name: 'ecRecover',
 			call: 'personal_ecRecover',
 			params: 2
+		}),
+		new web3._extend.Method({
+			name: 'deriveAccount',
+			call: 'personal_deriveAccount',
+			params: 3
+		})
+	],
+	properties:
+	[
+		new web3._extend.Property({
+			name: 'listWallets',
+			getter: 'personal_listWallets'
 		})
 	]
 })
diff --git a/miner/worker.go b/miner/worker.go
index 49ac60253..ef64c8fc9 100644
--- a/miner/worker.go
+++ b/miner/worker.go
@@ -386,8 +386,11 @@ func (self *worker) makeCurrent(parent *types.Block, header *types.Header) error
 		work.family.Add(ancestor.Hash())
 		work.ancestors.Add(ancestor.Hash())
 	}
-	accounts := self.eth.AccountManager().Accounts()
-
+	wallets := self.eth.AccountManager().Wallets()
+	accounts := make([]accounts.Account, 0, len(wallets))
+	for _, wallet := range wallets {
+		accounts = append(accounts, wallet.Accounts()...)
+	}
 	// Keep track of transactions which return errors so they can be removed
 	work.tcount = 0
 	work.ownedAccounts = accountAddressesSet(accounts)
diff --git a/mobile/accounts.go b/mobile/accounts.go
index 621be4d7a..fbaa3bf40 100644
--- a/mobile/accounts.go
+++ b/mobile/accounts.go
@@ -24,24 +24,25 @@ import (
 	"time"
 
 	"github.com/ethereum/go-ethereum/accounts"
+	"github.com/ethereum/go-ethereum/accounts/keystore"
 )
 
 const (
 	// StandardScryptN is the N parameter of Scrypt encryption algorithm, using 256MB
 	// memory and taking approximately 1s CPU time on a modern processor.
-	StandardScryptN = int(accounts.StandardScryptN)
+	StandardScryptN = int(keystore.StandardScryptN)
 
 	// StandardScryptP is the P parameter of Scrypt encryption algorithm, using 256MB
 	// memory and taking approximately 1s CPU time on a modern processor.
-	StandardScryptP = int(accounts.StandardScryptP)
+	StandardScryptP = int(keystore.StandardScryptP)
 
 	// LightScryptN is the N parameter of Scrypt encryption algorithm, using 4MB
 	// memory and taking approximately 100ms CPU time on a modern processor.
-	LightScryptN = int(accounts.LightScryptN)
+	LightScryptN = int(keystore.LightScryptN)
 
 	// LightScryptP is the P parameter of Scrypt encryption algorithm, using 4MB
 	// memory and taking approximately 100ms CPU time on a modern processor.
-	LightScryptP = int(accounts.LightScryptP)
+	LightScryptP = int(keystore.LightScryptP)
 )
 
 // Account represents a stored key.
@@ -77,59 +78,75 @@ func (a *Account) GetAddress() *Address {
 	return &Address{a.account.Address}
 }
 
-// GetFile retrieves the path of the file containing the account key.
-func (a *Account) GetFile() string {
-	return a.account.File
+// GetURL retrieves the canonical URL of the account.
+func (a *Account) GetURL() string {
+	return a.account.URL.String()
 }
 
-// AccountManager manages a key storage directory on disk.
-type AccountManager struct{ manager *accounts.Manager }
+// KeyStore manages a key storage directory on disk.
+type KeyStore struct{ keystore *keystore.KeyStore }
 
-// NewAccountManager creates a manager for the given directory.
-func NewAccountManager(keydir string, scryptN, scryptP int) *AccountManager {
-	return &AccountManager{manager: accounts.NewManager(keydir, scryptN, scryptP)}
+// NewKeyStore creates a keystore for the given directory.
+func NewKeyStore(keydir string, scryptN, scryptP int) *KeyStore {
+	return &KeyStore{keystore: keystore.NewKeyStore(keydir, scryptN, scryptP)}
 }
 
 // HasAddress reports whether a key with the given address is present.
-func (am *AccountManager) HasAddress(address *Address) bool {
-	return am.manager.HasAddress(address.address)
+func (ks *KeyStore) HasAddress(address *Address) bool {
+	return ks.keystore.HasAddress(address.address)
 }
 
 // GetAccounts returns all key files present in the directory.
-func (am *AccountManager) GetAccounts() *Accounts {
-	return &Accounts{am.manager.Accounts()}
+func (ks *KeyStore) GetAccounts() *Accounts {
+	return &Accounts{ks.keystore.Accounts()}
 }
 
 // DeleteAccount deletes the key matched by account if the passphrase is correct.
 // If a contains no filename, the address must match a unique key.
-func (am *AccountManager) DeleteAccount(account *Account, passphrase string) error {
-	return am.manager.Delete(accounts.Account{
-		Address: account.account.Address,
-		File:    account.account.File,
-	}, passphrase)
+func (ks *KeyStore) DeleteAccount(account *Account, passphrase string) error {
+	return ks.keystore.Delete(account.account, passphrase)
 }
 
-// Sign calculates a ECDSA signature for the given hash. The produced signature
+// SignHash calculates a ECDSA signature for the given hash. The produced signature
 // is in the [R || S || V] format where V is 0 or 1.
-func (am *AccountManager) Sign(address *Address, hash []byte) (signature []byte, _ error) {
-	return am.manager.Sign(address.address, hash)
+func (ks *KeyStore) SignHash(address *Address, hash []byte) (signature []byte, _ error) {
+	return ks.keystore.SignHash(accounts.Account{Address: address.address}, hash)
 }
 
-// SignPassphrase signs hash if the private key matching the given address can
+// SignTx signs the given transaction with the requested account.
+func (ks *KeyStore) SignTx(account *Account, tx *Transaction, chainID *BigInt) (*Transaction, error) {
+	signed, err := ks.keystore.SignTx(account.account, tx.tx, chainID.bigint)
+	if err != nil {
+		return nil, err
+	}
+	return &Transaction{signed}, nil
+}
+
+// SignHashPassphrase signs hash if the private key matching the given address can
 // be decrypted with the given passphrase. The produced signature is in the
 // [R || S || V] format where V is 0 or 1.
-func (am *AccountManager) SignPassphrase(account *Account, passphrase string, hash []byte) (signature []byte, _ error) {
-	return am.manager.SignWithPassphrase(account.account, passphrase, hash)
+func (ks *KeyStore) SignHashPassphrase(account *Account, passphrase string, hash []byte) (signature []byte, _ error) {
+	return ks.keystore.SignHashWithPassphrase(account.account, passphrase, hash)
+}
+
+// SignTxPassphrase signs the transaction if the private key matching the
+// given address can be decrypted with the given passphrase.
+func (ks *KeyStore) SignTxPassphrase(account *Account, passphrase string, tx *Transaction, chainID *BigInt) (*Transaction, error) {
+	signed, err := ks.keystore.SignTxWithPassphrase(account.account, passphrase, tx.tx, chainID.bigint)
+	if err != nil {
+		return nil, err
+	}
+	return &Transaction{signed}, nil
 }
 
 // Unlock unlocks the given account indefinitely.
-func (am *AccountManager) Unlock(account *Account, passphrase string) error {
-	return am.manager.TimedUnlock(account.account, passphrase, 0)
+func (ks *KeyStore) Unlock(account *Account, passphrase string) error {
+	return ks.keystore.TimedUnlock(account.account, passphrase, 0)
 }
 
 // Lock removes the private key with the given address from memory.
-func (am *AccountManager) Lock(address *Address) error {
-	return am.manager.Lock(address.address)
+func (ks *KeyStore) Lock(address *Address) error {
+	return ks.keystore.Lock(address.address)
 }
 
 // TimedUnlock unlocks the given account with the passphrase. The account stays
@@ -139,14 +156,14 @@ func (am *AccountManager) Lock(address *Address) error {
 // If the account address is already unlocked for a duration, TimedUnlock extends or
 // shortens the active unlock timeout. If the address was previously unlocked
 // indefinitely the timeout is not altered.
-func (am *AccountManager) TimedUnlock(account *Account, passphrase string, timeout int64) error {
-	return am.manager.TimedUnlock(account.account, passphrase, time.Duration(timeout))
+func (ks *KeyStore) TimedUnlock(account *Account, passphrase string, timeout int64) error {
+	return ks.keystore.TimedUnlock(account.account, passphrase, time.Duration(timeout))
 }
 
 // NewAccount generates a new key and stores it into the key directory,
 // encrypting it with the passphrase.
-func (am *AccountManager) NewAccount(passphrase string) (*Account, error) {
-	account, err := am.manager.NewAccount(passphrase)
+func (ks *KeyStore) NewAccount(passphrase string) (*Account, error) {
+	account, err := ks.keystore.NewAccount(passphrase)
 	if err != nil {
 		return nil, err
 	}
@@ -154,13 +171,13 @@ func (am *AccountManager) NewAccount(passphrase string) (*Account, error) {
 }
 
 // ExportKey exports as a JSON key, encrypted with newPassphrase.
-func (am *AccountManager) ExportKey(account *Account, passphrase, newPassphrase string) (key []byte, _ error) {
-	return am.manager.Export(account.account, passphrase, newPassphrase)
+func (ks *KeyStore) ExportKey(account *Account, passphrase, newPassphrase string) (key []byte, _ error) {
+	return ks.keystore.Export(account.account, passphrase, newPassphrase)
 }
 
 // ImportKey stores the given encrypted JSON key into the key directory.
-func (am *AccountManager) ImportKey(keyJSON []byte, passphrase, newPassphrase string) (account *Account, _ error) {
-	acc, err := am.manager.Import(keyJSON, passphrase, newPassphrase)
+func (ks *KeyStore) ImportKey(keyJSON []byte, passphrase, newPassphrase string) (account *Account, _ error) {
+	acc, err := ks.keystore.Import(keyJSON, passphrase, newPassphrase)
 	if err != nil {
 		return nil, err
 	}
@@ -168,14 +185,14 @@ func (am *AccountManager) ImportKey(keyJSON []byte, passphrase, newPassphrase st
 }
 
 // UpdateAccount changes the passphrase of an existing account.
-func (am *AccountManager) UpdateAccount(account *Account, passphrase, newPassphrase string) error {
-	return am.manager.Update(account.account, passphrase, newPassphrase)
+func (ks *KeyStore) UpdateAccount(account *Account, passphrase, newPassphrase string) error {
+	return ks.keystore.Update(account.account, passphrase, newPassphrase)
 }
 
 // ImportPreSaleKey decrypts the given Ethereum presale wallet and stores
 // a key file in the key directory. The key file is encrypted with the same passphrase.
-func (am *AccountManager) ImportPreSaleKey(keyJSON []byte, passphrase string) (ccount *Account, _ error) {
-	account, err := am.manager.ImportPreSaleKey(keyJSON, passphrase)
+func (ks *KeyStore) ImportPreSaleKey(keyJSON []byte, passphrase string) (ccount *Account, _ error) {
+	account, err := ks.keystore.ImportPreSaleKey(keyJSON, passphrase)
 	if err != nil {
 		return nil, err
 	}
diff --git a/mobile/android_test.go b/mobile/android_test.go
index 3776f8291..6f5076d64 100644
--- a/mobile/android_test.go
+++ b/mobile/android_test.go
@@ -43,42 +43,46 @@ public class AndroidTest extends InstrumentationTestCase {
 	public AndroidTest() {}
 
 	public void testAccountManagement() {
-		// Create an encrypted keystore manager with light crypto parameters.
-		AccountManager am = new AccountManager(getInstrumentation().getContext().getFilesDir() + "/keystore", Geth.LightScryptN, Geth.LightScryptP);
+		// Create an encrypted keystore with light crypto parameters.
+		KeyStore ks = new KeyStore(getInstrumentation().getContext().getFilesDir() + "/keystore", Geth.LightScryptN, Geth.LightScryptP);
 
 		try {
 			// Create a new account with the specified encryption passphrase.
-			Account newAcc = am.newAccount("Creation password");
+			Account newAcc = ks.newAccount("Creation password");
 
 			// Export the newly created account with a different passphrase. The returned
 			// data from this method invocation is a JSON encoded, encrypted key-file.
-			byte[] jsonAcc = am.exportKey(newAcc, "Creation password", "Export password");
+			byte[] jsonAcc = ks.exportKey(newAcc, "Creation password", "Export password");
 
 			// Update the passphrase on the account created above inside the local keystore.
-			am.updateAccount(newAcc, "Creation password", "Update password");
+			ks.updateAccount(newAcc, "Creation password", "Update password");
 
 			// Delete the account updated above from the local keystore.
-			am.deleteAccount(newAcc, "Update password");
+			ks.deleteAccount(newAcc, "Update password");
 
 			// Import back the account we've exported (and then deleted) above with yet
 			// again a fresh passphrase.
-			Account impAcc = am.importKey(jsonAcc, "Export password", "Import password");
+			Account impAcc = ks.importKey(jsonAcc, "Export password", "Import password");
 
 			// Create a new account to sign transactions with
-			Account signer = am.newAccount("Signer password");
-			Hash txHash = new Hash("0x0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef");
+			Account signer = ks.newAccount("Signer password");
+
+			Transaction tx = new Transaction(
+				1, new Address("0x0000000000000000000000000000000000000000"),
+				new BigInt(0), new BigInt(0), new BigInt(1), null); // Random empty transaction
+			BigInt chain = new BigInt(1); // Chain identifier of the main net
 
 			// Sign a transaction with a single authorization
-			byte[] signature = am.signPassphrase(signer, "Signer password", txHash.getBytes());
+			Transaction signed = ks.signTxPassphrase(signer, "Signer password", tx, chain);
 
 			// Sign a transaction with multiple manually cancelled authorizations
-			am.unlock(signer, "Signer password");
-			signature = am.sign(signer.getAddress(), txHash.getBytes());
-			am.lock(signer.getAddress());
+			ks.unlock(signer, "Signer password");
+			signed = ks.signTx(signer, tx, chain);
+			ks.lock(signer.getAddress());
 
 			// Sign a transaction with multiple automatically cancelled authorizations
-			am.timedUnlock(signer, "Signer password", 1000000000);
-			signature = am.sign(signer.getAddress(), txHash.getBytes());
+			ks.timedUnlock(signer, "Signer password", 1000000000);
+			signed = ks.signTx(signer, tx, chain);
 		} catch (Exception e) {
 			fail(e.toString());
 		}
diff --git a/mobile/types.go b/mobile/types.go
index 9ea70ea9b..a9c8cf68c 100644
--- a/mobile/types.go
+++ b/mobile/types.go
@@ -132,6 +132,11 @@ type Transaction struct {
 	tx *types.Transaction
 }
 
+// NewTransaction creates a new transaction with the given properties.
+func NewTransaction(nonce int64, to *Address, amount, gasLimit, gasPrice *BigInt, data []byte) *Transaction {
+	return &Transaction{types.NewTransaction(uint64(nonce), to.address, amount.bigint, gasLimit.bigint, gasPrice.bigint, data)}
+}
+
 func (tx *Transaction) GetData() []byte      { return tx.tx.Data() }
 func (tx *Transaction) GetGas() int64        { return tx.tx.Gas().Int64() }
 func (tx *Transaction) GetGasPrice() *BigInt { return &BigInt{tx.tx.GasPrice()} }
diff --git a/node/config.go b/node/config.go
index 8d75e441b..c09f51747 100644
--- a/node/config.go
+++ b/node/config.go
@@ -27,6 +27,8 @@ import (
 	"strings"
 
 	"github.com/ethereum/go-ethereum/accounts"
+	"github.com/ethereum/go-ethereum/accounts/keystore"
+	"github.com/ethereum/go-ethereum/accounts/usbwallet"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/logger"
@@ -400,15 +402,19 @@ func (c *Config) parsePersistentNodes(path string) []*discover.Node {
 	return nodes
 }
 
-func makeAccountManager(conf *Config) (am *accounts.Manager, ephemeralKeystore string, err error) {
-	scryptN := accounts.StandardScryptN
-	scryptP := accounts.StandardScryptP
+func makeAccountManager(conf *Config) (*accounts.Manager, string, error) {
+	scryptN := keystore.StandardScryptN
+	scryptP := keystore.StandardScryptP
 	if conf.UseLightweightKDF {
-		scryptN = accounts.LightScryptN
-		scryptP = accounts.LightScryptP
+		scryptN = keystore.LightScryptN
+		scryptP = keystore.LightScryptP
 	}
 
-	var keydir string
+	var (
+		keydir    string
+		ephemeral string
+		err       error
+	)
 	switch {
 	case filepath.IsAbs(conf.KeyStoreDir):
 		keydir = conf.KeyStoreDir
@@ -423,7 +429,7 @@ func makeAccountManager(conf *Config) (am *accounts.Manager, ephemeralKeystore s
 	default:
 		// There is no datadir.
 		keydir, err = ioutil.TempDir("", "go-ethereum-keystore")
-		ephemeralKeystore = keydir
+		ephemeral = keydir
 	}
 	if err != nil {
 		return nil, "", err
@@ -431,6 +437,14 @@ func makeAccountManager(conf *Config) (am *accounts.Manager, ephemeralKeystore s
 	if err := os.MkdirAll(keydir, 0700); err != nil {
 		return nil, "", err
 	}
-
-	return accounts.NewManager(keydir, scryptN, scryptP), ephemeralKeystore, nil
+	// Assemble the account manager and supported backends
+	backends := []accounts.Backend{
+		keystore.NewKeyStore(keydir, scryptN, scryptP),
+	}
+	if ledgerhub, err := usbwallet.NewLedgerHub(); err != nil {
+		glog.V(logger.Warn).Infof("Failed to start Ledger hub, disabling: %v", err)
+	} else {
+		backends = append(backends, ledgerhub)
+	}
+	return accounts.NewManager(backends...), ephemeral, nil
 }
diff --git a/vendor.conf b/vendor.conf
index 1428a1b59..92092a2ac 100644
--- a/vendor.conf
+++ b/vendor.conf
@@ -13,6 +13,7 @@ github.com/golang/snappy	d9eb7a3
 github.com/hashicorp/golang-lru	0a025b7
 github.com/huin/goupnp	679507a
 github.com/jackpal/go-nat-pmp	v1.0.1-4-g1fa385a
+github.com/karalabe/gousb	ffa821b
 github.com/maruel/panicparse	ad66119
 github.com/mattn/go-colorable	v0.0.6-9-gd228849
 github.com/mattn/go-isatty	30a891c
diff --git a/vendor/github.com/karalabe/gousb/.gitignore b/vendor/github.com/karalabe/gousb/.gitignore
new file mode 100644
index 000000000..dbec55fb6
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/.gitignore
@@ -0,0 +1 @@
+*.sw[op]
diff --git a/vendor/github.com/karalabe/gousb/.travis.yml b/vendor/github.com/karalabe/gousb/.travis.yml
new file mode 100644
index 000000000..2029cc478
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/.travis.yml
@@ -0,0 +1,12 @@
+language: go
+
+matrix:
+  include:
+    - os: linux
+      dist: trusty
+      go: 1.7.4
+    - os: osx
+      go: 1.7.4
+
+script:
+  - go test -v -test.run='BCD|Parse' ./...
diff --git a/vendor/github.com/karalabe/gousb/LICENSE b/vendor/github.com/karalabe/gousb/LICENSE
new file mode 100644
index 000000000..d64569567
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/LICENSE
@@ -0,0 +1,202 @@
+
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diff --git a/vendor/github.com/karalabe/gousb/README.md b/vendor/github.com/karalabe/gousb/README.md
new file mode 100644
index 000000000..05f333003
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/README.md
@@ -0,0 +1,47 @@
+Introduction
+============
+
+[![Travis Build Status][travisimg]][travis]
+[![AppVeyor Build Status][appveyorimg]][appveyor]
+[![GoDoc][docimg]][doc]
+
+The gousb package is an attempt at wrapping the `libusb` library into a Go-like binding in a fully self-contained, go-gettable package. Supported platforms include Linux, macOS and Windows as well as the mobile platforms Android and iOS.
+
+This package is a fork of [`github.com/kylelemons/gousb`](https://github.com/kylelemons/gousb), which at the moment seems to be unmaintained. The current fork is different from the upstream package as it contains code to embed `libusb` directly into the Go package (thus becoming fully self-cotnained and go-gettable), as well as it features a few contributions and bugfixes that never really got addressed in the upstream package, but which address important issues nonetheless.
+
+*Note, if @kylelemons decides to pick development of the upstream project up again, consider all commits made by me to this repo as ready contributions. I cannot vouch for other commits as the upstream repo needs a signed CLA for Google.*
+
+[travisimg]:   https://travis-ci.org/karalabe/gousb.svg?branch=master
+[travis]:      https://travis-ci.org/karalabe/gousb
+[appveyorimg]: https://ci.appveyor.com/api/projects/status/84k9xse10rl72gn2/branch/master?svg=true
+[appveyor]:    https://ci.appveyor.com/project/karalabe/gousb
+[docimg]:      https://godoc.org/github.com/karalabe/gousb?status.svg
+[doc]:         https://godoc.org/github.com/karalabe/gousb
+
+Installation
+============
+
+Example: lsusb
+--------------
+The gousb project provides a simple but useful example: lsusb.  This binary will list the USB devices connected to your system and various interesting tidbits about them, their configurations, endpoints, etc.  To install it, run the following command:
+
+    go get -v github.com/karalabe/gousb/lsusb
+
+gousb
+-----
+If you installed the lsusb example, both libraries below are already installed.
+
+Installing the primary gousb package is really easy:
+
+    go get -v github.com/karalabe/gousb/usb
+
+There is also a `usbid` package that will not be installed by default by this command, but which provides useful information including the human-readable vendor and product codes for detected hardware.  It's not installed by default and not linked into the `usb` package by default because it adds ~400kb to the resulting binary.  If you want both, they can be installed thus:
+
+    go get -v github.com/karalabe/gousb/usb{,id}
+
+Documentation
+=============
+The documentation can be viewed via local godoc or via the excellent [godoc.org](http://godoc.org/):
+
+- [usb](http://godoc.org/github.com/karalabe/gousb/usb)
+- [usbid](http://godoc.org/pkg/github.com/karalabe/gousb/usbid)
diff --git a/vendor/github.com/karalabe/gousb/appveyor.yml b/vendor/github.com/karalabe/gousb/appveyor.yml
new file mode 100644
index 000000000..b24986202
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/appveyor.yml
@@ -0,0 +1,34 @@
+os: Visual Studio 2015
+
+# Clone directly into GOPATH.
+clone_folder: C:\gopath\src\github.com\karalabe\gousb
+clone_depth: 5
+version: "{branch}.{build}"
+environment:
+  global:
+    GOPATH: C:\gopath
+    CC: gcc.exe
+  matrix:
+    - GOARCH: amd64
+      MSYS2_ARCH: x86_64
+      MSYS2_BITS: 64
+      MSYSTEM: MINGW64
+      PATH: C:\msys64\mingw64\bin\;%PATH%
+    - GOARCH: 386
+      MSYS2_ARCH: i686
+      MSYS2_BITS: 32
+      MSYSTEM: MINGW32
+      PATH: C:\msys64\mingw32\bin\;%PATH%
+
+install:
+  - rmdir C:\go /s /q
+  - appveyor DownloadFile https://storage.googleapis.com/golang/go1.7.4.windows-%GOARCH%.zip
+  - 7z x go1.7.4.windows-%GOARCH%.zip -y -oC:\ > NUL
+  - go version
+  - gcc --version
+
+build_script:
+  - go install ./...
+
+test_script:
+  - go test -v -test.run="BCD|Parse" ./...
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/AUTHORS b/vendor/github.com/karalabe/gousb/internal/libusb/AUTHORS
new file mode 100644
index 000000000..70d407bd1
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/AUTHORS
@@ -0,0 +1,89 @@
+Copyright © 2001 Johannes Erdfelt <johannes@erdfelt.com>
+Copyright © 2007-2009 Daniel Drake <dsd@gentoo.org>
+Copyright © 2010-2012 Peter Stuge <peter@stuge.se>
+Copyright © 2008-2016 Nathan Hjelm <hjelmn@users.sourceforge.net>
+Copyright © 2009-2013 Pete Batard <pete@akeo.ie>
+Copyright © 2009-2013 Ludovic Rousseau <ludovic.rousseau@gmail.com>
+Copyright © 2010-2012 Michael Plante <michael.plante@gmail.com>
+Copyright © 2011-2013 Hans de Goede <hdegoede@redhat.com>
+Copyright © 2012-2013 Martin Pieuchot <mpi@openbsd.org>
+Copyright © 2012-2013 Toby Gray <toby.gray@realvnc.com>
+Copyright © 2013-2015 Chris Dickens <christopher.a.dickens@gmail.com>
+
+Other contributors:
+Akshay Jaggi
+Alan Ott
+Alan Stern
+Alex Vatchenko
+Andrew Fernandes
+Anthony Clay
+Antonio Ospite
+Artem Egorkine
+Aurelien Jarno
+Bastien Nocera
+Bei Zhang
+Benjamin Dobell
+Carl Karsten
+Colin Walters
+Dave Camarillo
+David Engraf
+David Moore
+Davidlohr Bueso
+Federico Manzan
+Felipe Balbi
+Florian Albrechtskirchinger
+Francesco Montorsi
+Francisco Facioni
+Gaurav Gupta
+Graeme Gill
+Gustavo Zacarias
+Hans Ulrich Niedermann
+Hector Martin
+Hoi-Ho Chan
+Ilya Konstantinov
+James Hanko
+John Sheu
+Joshua Blake
+Justin Bischoff
+Karsten Koenig
+Konrad Rzepecki
+Kuangye Guo
+Lars Kanis
+Lars Wirzenius
+Luca Longinotti
+Marcus Meissner
+Markus Heidelberg
+Martin Ettl
+Martin Koegler
+Matthias Bolte
+Mike Frysinger
+Mikhail Gusarov
+Moritz Fischer
+Ларионов Даниил
+Nicholas Corgan
+Omri Iluz
+Orin Eman
+Paul Fertser
+Pekka Nikander
+Rob Walker
+Sean McBride
+Sebastian Pipping
+Simon Haggett
+Simon Newton
+Thomas Röfer
+Tim Hutt
+Tim Roberts
+Tobias Klauser
+Toby Peterson
+Tormod Volden
+Trygve Laugstøl
+Uri Lublin
+Vasily Khoruzhick
+Vegard Storheil Eriksen
+Venkatesh Shukla
+Vitali Lovich
+Xiaofan Chen
+Zoltán Kovács
+Роман Донченко
+parafin
+xantares
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/COPYING b/vendor/github.com/karalabe/gousb/internal/libusb/COPYING
new file mode 100644
index 000000000..5ab7695ab
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/COPYING
@@ -0,0 +1,504 @@
+		  GNU LESSER GENERAL PUBLIC LICENSE
+		       Version 2.1, February 1999
+
+ Copyright (C) 1991, 1999 Free Software Foundation, Inc.
+ 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+[This is the first released version of the Lesser GPL.  It also counts
+ as the successor of the GNU Library Public License, version 2, hence
+ the version number 2.1.]
+
+			    Preamble
+
+  The licenses for most software are designed to take away your
+freedom to share and change it.  By contrast, the GNU General Public
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+
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+
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diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/config.h b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/config.h
new file mode 100644
index 000000000..e004f03cd
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/config.h
@@ -0,0 +1,3 @@
+#ifndef CONFIG_H
+#define CONFIG_H
+#endif
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/core.c b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/core.c
new file mode 100644
index 000000000..d45bfe177
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/core.c
@@ -0,0 +1,2523 @@
+/* -*- Mode: C; indent-tabs-mode:t ; c-basic-offset:8 -*- */
+/*
+ * Core functions for libusb
+ * Copyright © 2012-2013 Nathan Hjelm <hjelmn@cs.unm.edu>
+ * Copyright © 2007-2008 Daniel Drake <dsd@gentoo.org>
+ * Copyright © 2001 Johannes Erdfelt <johannes@erdfelt.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "config.h"
+
+#include <errno.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#ifdef HAVE_SYS_TYPES_H
+#include <sys/types.h>
+#endif
+#ifdef HAVE_SYS_TIME_H
+#include <sys/time.h>
+#endif
+#ifdef HAVE_SYSLOG_H
+#include <syslog.h>
+#endif
+
+#ifdef __ANDROID__
+#include <android/log.h>
+#endif
+
+#include "libusbi.h"
+#include "hotplug.h"
+
+#if defined(OS_LINUX)
+const struct usbi_os_backend * const usbi_backend = &linux_usbfs_backend;
+#elif defined(OS_DARWIN)
+const struct usbi_os_backend * const usbi_backend = &darwin_backend;
+#elif defined(OS_OPENBSD)
+const struct usbi_os_backend * const usbi_backend = &openbsd_backend;
+#elif defined(OS_NETBSD)
+const struct usbi_os_backend * const usbi_backend = &netbsd_backend;
+#elif defined(OS_WINDOWS)
+
+#if defined(USE_USBDK)
+const struct usbi_os_backend * const usbi_backend = &usbdk_backend;
+#else
+const struct usbi_os_backend * const usbi_backend = &windows_backend;
+#endif
+
+#elif defined(OS_WINCE)
+const struct usbi_os_backend * const usbi_backend = &wince_backend;
+#elif defined(OS_HAIKU)
+const struct usbi_os_backend * const usbi_backend = &haiku_usb_raw_backend;
+#elif defined (OS_SUNOS)
+const struct usbi_os_backend * const usbi_backend = &sunos_backend;
+#else
+#error "Unsupported OS"
+#endif
+
+struct libusb_context *usbi_default_context = NULL;
+static const struct libusb_version libusb_version_internal =
+	{ LIBUSB_MAJOR, LIBUSB_MINOR, LIBUSB_MICRO, LIBUSB_NANO,
+	  LIBUSB_RC, "http://libusb.info" };
+static int default_context_refcnt = 0;
+static usbi_mutex_static_t default_context_lock = USBI_MUTEX_INITIALIZER;
+static struct timespec timestamp_origin = { 0, 0 };
+
+usbi_mutex_static_t active_contexts_lock = USBI_MUTEX_INITIALIZER;
+struct list_head active_contexts_list;
+
+/**
+ * \mainpage libusb-1.0 API Reference
+ *
+ * \section intro Introduction
+ *
+ * libusb is an open source library that allows you to communicate with USB
+ * devices from userspace. For more info, see the
+ * <a href="http://libusb.info">libusb homepage</a>.
+ *
+ * This documentation is aimed at application developers wishing to
+ * communicate with USB peripherals from their own software. After reviewing
+ * this documentation, feedback and questions can be sent to the
+ * <a href="http://mailing-list.libusb.info">libusb-devel mailing list</a>.
+ *
+ * This documentation assumes knowledge of how to operate USB devices from
+ * a software standpoint (descriptors, configurations, interfaces, endpoints,
+ * control/bulk/interrupt/isochronous transfers, etc). Full information
+ * can be found in the <a href="http://www.usb.org/developers/docs/">USB 3.0
+ * Specification</a> which is available for free download. You can probably
+ * find less verbose introductions by searching the web.
+ *
+ * \section API Application Programming Interface (API)
+ *
+ * See the \ref libusb_api page for a complete list of the libusb functions.
+ *
+ * \section features Library features
+ *
+ * - All transfer types supported (control/bulk/interrupt/isochronous)
+ * - 2 transfer interfaces:
+ *    -# Synchronous (simple)
+ *    -# Asynchronous (more complicated, but more powerful)
+ * - Thread safe (although the asynchronous interface means that you
+ *   usually won't need to thread)
+ * - Lightweight with lean API
+ * - Compatible with libusb-0.1 through the libusb-compat-0.1 translation layer
+ * - Hotplug support (on some platforms). See \ref libusb_hotplug.
+ *
+ * \section gettingstarted Getting Started
+ *
+ * To begin reading the API documentation, start with the Modules page which
+ * links to the different categories of libusb's functionality.
+ *
+ * One decision you will have to make is whether to use the synchronous
+ * or the asynchronous data transfer interface. The \ref libusb_io documentation
+ * provides some insight into this topic.
+ *
+ * Some example programs can be found in the libusb source distribution under
+ * the "examples" subdirectory. The libusb homepage includes a list of
+ * real-life project examples which use libusb.
+ *
+ * \section errorhandling Error handling
+ *
+ * libusb functions typically return 0 on success or a negative error code
+ * on failure. These negative error codes relate to LIBUSB_ERROR constants
+ * which are listed on the \ref libusb_misc "miscellaneous" documentation page.
+ *
+ * \section msglog Debug message logging
+ *
+ * libusb uses stderr for all logging. By default, logging is set to NONE,
+ * which means that no output will be produced. However, unless the library
+ * has been compiled with logging disabled, then any application calls to
+ * libusb_set_debug(), or the setting of the environmental variable
+ * LIBUSB_DEBUG outside of the application, can result in logging being
+ * produced. Your application should therefore not close stderr, but instead
+ * direct it to the null device if its output is undesirable.
+ *
+ * The libusb_set_debug() function can be used to enable logging of certain
+ * messages. Under standard configuration, libusb doesn't really log much
+ * so you are advised to use this function to enable all error/warning/
+ * informational messages. It will help debug problems with your software.
+ *
+ * The logged messages are unstructured. There is no one-to-one correspondence
+ * between messages being logged and success or failure return codes from
+ * libusb functions. There is no format to the messages, so you should not
+ * try to capture or parse them. They are not and will not be localized.
+ * These messages are not intended to being passed to your application user;
+ * instead, you should interpret the error codes returned from libusb functions
+ * and provide appropriate notification to the user. The messages are simply
+ * there to aid you as a programmer, and if you're confused because you're
+ * getting a strange error code from a libusb function, enabling message
+ * logging may give you a suitable explanation.
+ *
+ * The LIBUSB_DEBUG environment variable can be used to enable message logging
+ * at run-time. This environment variable should be set to a log level number,
+ * which is interpreted the same as the libusb_set_debug() parameter. When this
+ * environment variable is set, the message logging verbosity level is fixed
+ * and libusb_set_debug() effectively does nothing.
+ *
+ * libusb can be compiled without any logging functions, useful for embedded
+ * systems. In this case, libusb_set_debug() and the LIBUSB_DEBUG environment
+ * variable have no effects.
+ *
+ * libusb can also be compiled with verbose debugging messages always. When
+ * the library is compiled in this way, all messages of all verbosities are
+ * always logged. libusb_set_debug() and the LIBUSB_DEBUG environment variable
+ * have no effects.
+ *
+ * \section remarks Other remarks
+ *
+ * libusb does have imperfections. The \ref libusb_caveats "caveats" page attempts
+ * to document these.
+ */
+
+/**
+ * \page libusb_caveats Caveats
+ *
+ * \section devresets Device resets
+ *
+ * The libusb_reset_device() function allows you to reset a device. If your
+ * program has to call such a function, it should obviously be aware that
+ * the reset will cause device state to change (e.g. register values may be
+ * reset).
+ *
+ * The problem is that any other program could reset the device your program
+ * is working with, at any time. libusb does not offer a mechanism to inform
+ * you when this has happened, so if someone else resets your device it will
+ * not be clear to your own program why the device state has changed.
+ *
+ * Ultimately, this is a limitation of writing drivers in userspace.
+ * Separation from the USB stack in the underlying kernel makes it difficult
+ * for the operating system to deliver such notifications to your program.
+ * The Linux kernel USB stack allows such reset notifications to be delivered
+ * to in-kernel USB drivers, but it is not clear how such notifications could
+ * be delivered to second-class drivers that live in userspace.
+ *
+ * \section blockonly Blocking-only functionality
+ *
+ * The functionality listed below is only available through synchronous,
+ * blocking functions. There are no asynchronous/non-blocking alternatives,
+ * and no clear ways of implementing these.
+ *
+ * - Configuration activation (libusb_set_configuration())
+ * - Interface/alternate setting activation (libusb_set_interface_alt_setting())
+ * - Releasing of interfaces (libusb_release_interface())
+ * - Clearing of halt/stall condition (libusb_clear_halt())
+ * - Device resets (libusb_reset_device())
+ *
+ * \section configsel Configuration selection and handling
+ *
+ * When libusb presents a device handle to an application, there is a chance
+ * that the corresponding device may be in unconfigured state. For devices
+ * with multiple configurations, there is also a chance that the configuration
+ * currently selected is not the one that the application wants to use.
+ *
+ * The obvious solution is to add a call to libusb_set_configuration() early
+ * on during your device initialization routines, but there are caveats to
+ * be aware of:
+ * -# If the device is already in the desired configuration, calling
+ *    libusb_set_configuration() using the same configuration value will cause
+ *    a lightweight device reset. This may not be desirable behaviour.
+ * -# In the case where the desired configuration is already active, libusb
+ *    may not even be able to perform a lightweight device reset. For example,
+ *    take my USB keyboard with fingerprint reader: I'm interested in driving
+ *    the fingerprint reader interface through libusb, but the kernel's
+ *    USB-HID driver will almost always have claimed the keyboard interface.
+ *    Because the kernel has claimed an interface, it is not even possible to
+ *    perform the lightweight device reset, so libusb_set_configuration() will
+ *    fail. (Luckily the device in question only has a single configuration.)
+ * -# libusb will be unable to set a configuration if other programs or
+ *    drivers have claimed interfaces. In particular, this means that kernel
+ *    drivers must be detached from all the interfaces before
+ *    libusb_set_configuration() may succeed.
+ *
+ * One solution to some of the above problems is to consider the currently
+ * active configuration. If the configuration we want is already active, then
+ * we don't have to select any configuration:
+\code
+cfg = -1;
+libusb_get_configuration(dev, &cfg);
+if (cfg != desired)
+	libusb_set_configuration(dev, desired);
+\endcode
+ *
+ * This is probably suitable for most scenarios, but is inherently racy:
+ * another application or driver may change the selected configuration
+ * <em>after</em> the libusb_get_configuration() call.
+ *
+ * Even in cases where libusb_set_configuration() succeeds, consider that other
+ * applications or drivers may change configuration after your application
+ * calls libusb_set_configuration().
+ *
+ * One possible way to lock your device into a specific configuration is as
+ * follows:
+ * -# Set the desired configuration (or use the logic above to realise that
+ *    it is already in the desired configuration)
+ * -# Claim the interface that you wish to use
+ * -# Check that the currently active configuration is the one that you want
+ *    to use.
+ *
+ * The above method works because once an interface is claimed, no application
+ * or driver is able to select another configuration.
+ *
+ * \section earlycomp Early transfer completion
+ *
+ * NOTE: This section is currently Linux-centric. I am not sure if any of these
+ * considerations apply to Darwin or other platforms.
+ *
+ * When a transfer completes early (i.e. when less data is received/sent in
+ * any one packet than the transfer buffer allows for) then libusb is designed
+ * to terminate the transfer immediately, not transferring or receiving any
+ * more data unless other transfers have been queued by the user.
+ *
+ * On legacy platforms, libusb is unable to do this in all situations. After
+ * the incomplete packet occurs, "surplus" data may be transferred. For recent
+ * versions of libusb, this information is kept (the data length of the
+ * transfer is updated) and, for device-to-host transfers, any surplus data was
+ * added to the buffer. Still, this is not a nice solution because it loses the
+ * information about the end of the short packet, and the user probably wanted
+ * that surplus data to arrive in the next logical transfer.
+ *
+ *
+ * \section zlp Zero length packets
+ *
+ * - libusb is able to send a packet of zero length to an endpoint simply by
+ * submitting a transfer of zero length.
+ * - The \ref libusb_transfer_flags::LIBUSB_TRANSFER_ADD_ZERO_PACKET
+ * "LIBUSB_TRANSFER_ADD_ZERO_PACKET" flag is currently only supported on Linux.
+ */
+
+/**
+ * \page libusb_contexts Contexts
+ *
+ * It is possible that libusb may be used simultaneously from two independent
+ * libraries linked into the same executable. For example, if your application
+ * has a plugin-like system which allows the user to dynamically load a range
+ * of modules into your program, it is feasible that two independently
+ * developed modules may both use libusb.
+ *
+ * libusb is written to allow for these multiple user scenarios. The two
+ * "instances" of libusb will not interfere: libusb_set_debug() calls
+ * from one user will not affect the same settings for other users, other
+ * users can continue using libusb after one of them calls libusb_exit(), etc.
+ *
+ * This is made possible through libusb's <em>context</em> concept. When you
+ * call libusb_init(), you are (optionally) given a context. You can then pass
+ * this context pointer back into future libusb functions.
+ *
+ * In order to keep things simple for more simplistic applications, it is
+ * legal to pass NULL to all functions requiring a context pointer (as long as
+ * you're sure no other code will attempt to use libusb from the same process).
+ * When you pass NULL, the default context will be used. The default context
+ * is created the first time a process calls libusb_init() when no other
+ * context is alive. Contexts are destroyed during libusb_exit().
+ *
+ * The default context is reference-counted and can be shared. That means that
+ * if libusb_init(NULL) is called twice within the same process, the two
+ * users end up sharing the same context. The deinitialization and freeing of
+ * the default context will only happen when the last user calls libusb_exit().
+ * In other words, the default context is created and initialized when its
+ * reference count goes from 0 to 1, and is deinitialized and destroyed when
+ * its reference count goes from 1 to 0.
+ *
+ * You may be wondering why only a subset of libusb functions require a
+ * context pointer in their function definition. Internally, libusb stores
+ * context pointers in other objects (e.g. libusb_device instances) and hence
+ * can infer the context from those objects.
+ */
+
+ /**
+  * \page libusb_api Application Programming Interface
+  *
+  * This is the complete list of libusb functions, structures and
+  * enumerations in alphabetical order.
+  *
+  * \section Functions
+  * - libusb_alloc_streams()
+  * - libusb_alloc_transfer()
+  * - libusb_attach_kernel_driver()
+  * - libusb_bulk_transfer()
+  * - libusb_cancel_transfer()
+  * - libusb_claim_interface()
+  * - libusb_clear_halt()
+  * - libusb_close()
+  * - libusb_control_transfer()
+  * - libusb_control_transfer_get_data()
+  * - libusb_control_transfer_get_setup()
+  * - libusb_cpu_to_le16()
+  * - libusb_detach_kernel_driver()
+  * - libusb_dev_mem_alloc()
+  * - libusb_dev_mem_free()
+  * - libusb_error_name()
+  * - libusb_event_handler_active()
+  * - libusb_event_handling_ok()
+  * - libusb_exit()
+  * - libusb_fill_bulk_stream_transfer()
+  * - libusb_fill_bulk_transfer()
+  * - libusb_fill_control_setup()
+  * - libusb_fill_control_transfer()
+  * - libusb_fill_interrupt_transfer()
+  * - libusb_fill_iso_transfer()
+  * - libusb_free_bos_descriptor()
+  * - libusb_free_config_descriptor()
+  * - libusb_free_container_id_descriptor()
+  * - libusb_free_device_list()
+  * - libusb_free_pollfds()
+  * - libusb_free_ss_endpoint_companion_descriptor()
+  * - libusb_free_ss_usb_device_capability_descriptor()
+  * - libusb_free_streams()
+  * - libusb_free_transfer()
+  * - libusb_free_usb_2_0_extension_descriptor()
+  * - libusb_get_active_config_descriptor()
+  * - libusb_get_bos_descriptor()
+  * - libusb_get_bus_number()
+  * - libusb_get_config_descriptor()
+  * - libusb_get_config_descriptor_by_value()
+  * - libusb_get_configuration()
+  * - libusb_get_container_id_descriptor()
+  * - libusb_get_descriptor()
+  * - libusb_get_device()
+  * - libusb_get_device_address()
+  * - libusb_get_device_descriptor()
+  * - libusb_get_device_list()
+  * - libusb_get_device_speed()
+  * - libusb_get_iso_packet_buffer()
+  * - libusb_get_iso_packet_buffer_simple()
+  * - libusb_get_max_iso_packet_size()
+  * - libusb_get_max_packet_size()
+  * - libusb_get_next_timeout()
+  * - libusb_get_parent()
+  * - libusb_get_pollfds()
+  * - libusb_get_port_number()
+  * - libusb_get_port_numbers()
+  * - libusb_get_port_path()
+  * - libusb_get_ss_endpoint_companion_descriptor()
+  * - libusb_get_ss_usb_device_capability_descriptor()
+  * - libusb_get_string_descriptor()
+  * - libusb_get_string_descriptor_ascii()
+  * - libusb_get_usb_2_0_extension_descriptor()
+  * - libusb_get_version()
+  * - libusb_handle_events()
+  * - libusb_handle_events_completed()
+  * - libusb_handle_events_locked()
+  * - libusb_handle_events_timeout()
+  * - libusb_handle_events_timeout_completed()
+  * - libusb_has_capability()
+  * - libusb_hotplug_deregister_callback()
+  * - libusb_hotplug_register_callback()
+  * - libusb_init()
+  * - libusb_interrupt_event_handler()
+  * - libusb_interrupt_transfer()
+  * - libusb_kernel_driver_active()
+  * - libusb_lock_events()
+  * - libusb_lock_event_waiters()
+  * - libusb_open()
+  * - libusb_open_device_with_vid_pid()
+  * - libusb_pollfds_handle_timeouts()
+  * - libusb_ref_device()
+  * - libusb_release_interface()
+  * - libusb_reset_device()
+  * - libusb_set_auto_detach_kernel_driver()
+  * - libusb_set_configuration()
+  * - libusb_set_debug()
+  * - libusb_set_interface_alt_setting()
+  * - libusb_set_iso_packet_lengths()
+  * - libusb_setlocale()
+  * - libusb_set_pollfd_notifiers()
+  * - libusb_strerror()
+  * - libusb_submit_transfer()
+  * - libusb_transfer_get_stream_id()
+  * - libusb_transfer_set_stream_id()
+  * - libusb_try_lock_events()
+  * - libusb_unlock_events()
+  * - libusb_unlock_event_waiters()
+  * - libusb_unref_device()
+  * - libusb_wait_for_event()
+  *
+  * \section Structures
+  * - libusb_bos_descriptor
+  * - libusb_bos_dev_capability_descriptor
+  * - libusb_config_descriptor
+  * - libusb_container_id_descriptor
+  * - \ref libusb_context
+  * - libusb_control_setup
+  * - \ref libusb_device
+  * - libusb_device_descriptor
+  * - \ref libusb_device_handle
+  * - libusb_endpoint_descriptor
+  * - libusb_interface
+  * - libusb_interface_descriptor
+  * - libusb_iso_packet_descriptor
+  * - libusb_pollfd
+  * - libusb_ss_endpoint_companion_descriptor
+  * - libusb_ss_usb_device_capability_descriptor
+  * - libusb_transfer
+  * - libusb_usb_2_0_extension_descriptor
+  * - libusb_version
+  *
+  * \section Enums
+  * - \ref libusb_bos_type
+  * - \ref libusb_capability
+  * - \ref libusb_class_code
+  * - \ref libusb_descriptor_type
+  * - \ref libusb_endpoint_direction
+  * - \ref libusb_error
+  * - \ref libusb_iso_sync_type
+  * - \ref libusb_iso_usage_type
+  * - \ref libusb_log_level
+  * - \ref libusb_request_recipient
+  * - \ref libusb_request_type
+  * - \ref libusb_speed
+  * - \ref libusb_ss_usb_device_capability_attributes
+  * - \ref libusb_standard_request
+  * - \ref libusb_supported_speed
+  * - \ref libusb_transfer_flags
+  * - \ref libusb_transfer_status
+  * - \ref libusb_transfer_type
+  * - \ref libusb_usb_2_0_extension_attributes
+  */
+
+/**
+ * @defgroup libusb_lib Library initialization/deinitialization
+ * This page details how to initialize and deinitialize libusb. Initialization
+ * must be performed before using any libusb functionality, and similarly you
+ * must not call any libusb functions after deinitialization.
+ */
+
+/**
+ * @defgroup libusb_dev Device handling and enumeration
+ * The functionality documented below is designed to help with the following
+ * operations:
+ * - Enumerating the USB devices currently attached to the system
+ * - Choosing a device to operate from your software
+ * - Opening and closing the chosen device
+ *
+ * \section nutshell In a nutshell...
+ *
+ * The description below really makes things sound more complicated than they
+ * actually are. The following sequence of function calls will be suitable
+ * for almost all scenarios and does not require you to have such a deep
+ * understanding of the resource management issues:
+ * \code
+// discover devices
+libusb_device **list;
+libusb_device *found = NULL;
+ssize_t cnt = libusb_get_device_list(NULL, &list);
+ssize_t i = 0;
+int err = 0;
+if (cnt < 0)
+	error();
+
+for (i = 0; i < cnt; i++) {
+	libusb_device *device = list[i];
+	if (is_interesting(device)) {
+		found = device;
+		break;
+	}
+}
+
+if (found) {
+	libusb_device_handle *handle;
+
+	err = libusb_open(found, &handle);
+	if (err)
+		error();
+	// etc
+}
+
+libusb_free_device_list(list, 1);
+\endcode
+ *
+ * The two important points:
+ * - You asked libusb_free_device_list() to unreference the devices (2nd
+ *   parameter)
+ * - You opened the device before freeing the list and unreferencing the
+ *   devices
+ *
+ * If you ended up with a handle, you can now proceed to perform I/O on the
+ * device.
+ *
+ * \section devshandles Devices and device handles
+ * libusb has a concept of a USB device, represented by the
+ * \ref libusb_device opaque type. A device represents a USB device that
+ * is currently or was previously connected to the system. Using a reference
+ * to a device, you can determine certain information about the device (e.g.
+ * you can read the descriptor data).
+ *
+ * The libusb_get_device_list() function can be used to obtain a list of
+ * devices currently connected to the system. This is known as device
+ * discovery.
+ *
+ * Just because you have a reference to a device does not mean it is
+ * necessarily usable. The device may have been unplugged, you may not have
+ * permission to operate such device, or another program or driver may be
+ * using the device.
+ *
+ * When you've found a device that you'd like to operate, you must ask
+ * libusb to open the device using the libusb_open() function. Assuming
+ * success, libusb then returns you a <em>device handle</em>
+ * (a \ref libusb_device_handle pointer). All "real" I/O operations then
+ * operate on the handle rather than the original device pointer.
+ *
+ * \section devref Device discovery and reference counting
+ *
+ * Device discovery (i.e. calling libusb_get_device_list()) returns a
+ * freshly-allocated list of devices. The list itself must be freed when
+ * you are done with it. libusb also needs to know when it is OK to free
+ * the contents of the list - the devices themselves.
+ *
+ * To handle these issues, libusb provides you with two separate items:
+ * - A function to free the list itself
+ * - A reference counting system for the devices inside
+ *
+ * New devices presented by the libusb_get_device_list() function all have a
+ * reference count of 1. You can increase and decrease reference count using
+ * libusb_ref_device() and libusb_unref_device(). A device is destroyed when
+ * its reference count reaches 0.
+ *
+ * With the above information in mind, the process of opening a device can
+ * be viewed as follows:
+ * -# Discover devices using libusb_get_device_list().
+ * -# Choose the device that you want to operate, and call libusb_open().
+ * -# Unref all devices in the discovered device list.
+ * -# Free the discovered device list.
+ *
+ * The order is important - you must not unreference the device before
+ * attempting to open it, because unreferencing it may destroy the device.
+ *
+ * For convenience, the libusb_free_device_list() function includes a
+ * parameter to optionally unreference all the devices in the list before
+ * freeing the list itself. This combines steps 3 and 4 above.
+ *
+ * As an implementation detail, libusb_open() actually adds a reference to
+ * the device in question. This is because the device remains available
+ * through the handle via libusb_get_device(). The reference is deleted during
+ * libusb_close().
+ */
+
+/** @defgroup libusb_misc Miscellaneous */
+
+/* we traverse usbfs without knowing how many devices we are going to find.
+ * so we create this discovered_devs model which is similar to a linked-list
+ * which grows when required. it can be freed once discovery has completed,
+ * eliminating the need for a list node in the libusb_device structure
+ * itself. */
+#define DISCOVERED_DEVICES_SIZE_STEP 8
+
+static struct discovered_devs *discovered_devs_alloc(void)
+{
+	struct discovered_devs *ret =
+		malloc(sizeof(*ret) + (sizeof(void *) * DISCOVERED_DEVICES_SIZE_STEP));
+
+	if (ret) {
+		ret->len = 0;
+		ret->capacity = DISCOVERED_DEVICES_SIZE_STEP;
+	}
+	return ret;
+}
+
+static void discovered_devs_free(struct discovered_devs *discdevs)
+{
+	size_t i;
+
+	for (i = 0; i < discdevs->len; i++)
+		libusb_unref_device(discdevs->devices[i]);
+
+	free(discdevs);
+}
+
+/* append a device to the discovered devices collection. may realloc itself,
+ * returning new discdevs. returns NULL on realloc failure. */
+struct discovered_devs *discovered_devs_append(
+	struct discovered_devs *discdevs, struct libusb_device *dev)
+{
+	size_t len = discdevs->len;
+	size_t capacity;
+	struct discovered_devs *new_discdevs;
+
+	/* if there is space, just append the device */
+	if (len < discdevs->capacity) {
+		discdevs->devices[len] = libusb_ref_device(dev);
+		discdevs->len++;
+		return discdevs;
+	}
+
+	/* exceeded capacity, need to grow */
+	usbi_dbg("need to increase capacity");
+	capacity = discdevs->capacity + DISCOVERED_DEVICES_SIZE_STEP;
+	/* can't use usbi_reallocf here because in failure cases it would
+	 * free the existing discdevs without unreferencing its devices. */
+	new_discdevs = realloc(discdevs,
+		sizeof(*discdevs) + (sizeof(void *) * capacity));
+	if (!new_discdevs) {
+		discovered_devs_free(discdevs);
+		return NULL;
+	}
+
+	discdevs = new_discdevs;
+	discdevs->capacity = capacity;
+	discdevs->devices[len] = libusb_ref_device(dev);
+	discdevs->len++;
+
+	return discdevs;
+}
+
+/* Allocate a new device with a specific session ID. The returned device has
+ * a reference count of 1. */
+struct libusb_device *usbi_alloc_device(struct libusb_context *ctx,
+	unsigned long session_id)
+{
+	size_t priv_size = usbi_backend->device_priv_size;
+	struct libusb_device *dev = calloc(1, sizeof(*dev) + priv_size);
+	int r;
+
+	if (!dev)
+		return NULL;
+
+	r = usbi_mutex_init(&dev->lock);
+	if (r) {
+		free(dev);
+		return NULL;
+	}
+
+	dev->ctx = ctx;
+	dev->refcnt = 1;
+	dev->session_data = session_id;
+	dev->speed = LIBUSB_SPEED_UNKNOWN;
+
+	if (!libusb_has_capability(LIBUSB_CAP_HAS_HOTPLUG)) {
+		usbi_connect_device (dev);
+	}
+
+	return dev;
+}
+
+void usbi_connect_device(struct libusb_device *dev)
+{
+	struct libusb_context *ctx = DEVICE_CTX(dev);
+
+	dev->attached = 1;
+
+	usbi_mutex_lock(&dev->ctx->usb_devs_lock);
+	list_add(&dev->list, &dev->ctx->usb_devs);
+	usbi_mutex_unlock(&dev->ctx->usb_devs_lock);
+
+	/* Signal that an event has occurred for this device if we support hotplug AND
+	 * the hotplug message list is ready. This prevents an event from getting raised
+	 * during initial enumeration. */
+	if (libusb_has_capability(LIBUSB_CAP_HAS_HOTPLUG) && dev->ctx->hotplug_msgs.next) {
+		usbi_hotplug_notification(ctx, dev, LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED);
+	}
+}
+
+void usbi_disconnect_device(struct libusb_device *dev)
+{
+	struct libusb_context *ctx = DEVICE_CTX(dev);
+
+	usbi_mutex_lock(&dev->lock);
+	dev->attached = 0;
+	usbi_mutex_unlock(&dev->lock);
+
+	usbi_mutex_lock(&ctx->usb_devs_lock);
+	list_del(&dev->list);
+	usbi_mutex_unlock(&ctx->usb_devs_lock);
+
+	/* Signal that an event has occurred for this device if we support hotplug AND
+	 * the hotplug message list is ready. This prevents an event from getting raised
+	 * during initial enumeration. libusb_handle_events will take care of dereferencing
+	 * the device. */
+	if (libusb_has_capability(LIBUSB_CAP_HAS_HOTPLUG) && dev->ctx->hotplug_msgs.next) {
+		usbi_hotplug_notification(ctx, dev, LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT);
+	}
+}
+
+/* Perform some final sanity checks on a newly discovered device. If this
+ * function fails (negative return code), the device should not be added
+ * to the discovered device list. */
+int usbi_sanitize_device(struct libusb_device *dev)
+{
+	int r;
+	uint8_t num_configurations;
+
+	r = usbi_device_cache_descriptor(dev);
+	if (r < 0)
+		return r;
+
+	num_configurations = dev->device_descriptor.bNumConfigurations;
+	if (num_configurations > USB_MAXCONFIG) {
+		usbi_err(DEVICE_CTX(dev), "too many configurations");
+		return LIBUSB_ERROR_IO;
+	} else if (0 == num_configurations)
+		usbi_dbg("zero configurations, maybe an unauthorized device");
+
+	dev->num_configurations = num_configurations;
+	return 0;
+}
+
+/* Examine libusb's internal list of known devices, looking for one with
+ * a specific session ID. Returns the matching device if it was found, and
+ * NULL otherwise. */
+struct libusb_device *usbi_get_device_by_session_id(struct libusb_context *ctx,
+	unsigned long session_id)
+{
+	struct libusb_device *dev;
+	struct libusb_device *ret = NULL;
+
+	usbi_mutex_lock(&ctx->usb_devs_lock);
+	list_for_each_entry(dev, &ctx->usb_devs, list, struct libusb_device)
+		if (dev->session_data == session_id) {
+			ret = libusb_ref_device(dev);
+			break;
+		}
+	usbi_mutex_unlock(&ctx->usb_devs_lock);
+
+	return ret;
+}
+
+/** @ingroup libusb_dev
+ * Returns a list of USB devices currently attached to the system. This is
+ * your entry point into finding a USB device to operate.
+ *
+ * You are expected to unreference all the devices when you are done with
+ * them, and then free the list with libusb_free_device_list(). Note that
+ * libusb_free_device_list() can unref all the devices for you. Be careful
+ * not to unreference a device you are about to open until after you have
+ * opened it.
+ *
+ * This return value of this function indicates the number of devices in
+ * the resultant list. The list is actually one element larger, as it is
+ * NULL-terminated.
+ *
+ * \param ctx the context to operate on, or NULL for the default context
+ * \param list output location for a list of devices. Must be later freed with
+ * libusb_free_device_list().
+ * \returns the number of devices in the outputted list, or any
+ * \ref libusb_error according to errors encountered by the backend.
+ */
+ssize_t API_EXPORTED libusb_get_device_list(libusb_context *ctx,
+	libusb_device ***list)
+{
+	struct discovered_devs *discdevs = discovered_devs_alloc();
+	struct libusb_device **ret;
+	int r = 0;
+	ssize_t i, len;
+	USBI_GET_CONTEXT(ctx);
+	usbi_dbg("");
+
+	if (!discdevs)
+		return LIBUSB_ERROR_NO_MEM;
+
+	if (libusb_has_capability(LIBUSB_CAP_HAS_HOTPLUG)) {
+		/* backend provides hotplug support */
+		struct libusb_device *dev;
+
+		if (usbi_backend->hotplug_poll)
+			usbi_backend->hotplug_poll();
+
+		usbi_mutex_lock(&ctx->usb_devs_lock);
+		list_for_each_entry(dev, &ctx->usb_devs, list, struct libusb_device) {
+			discdevs = discovered_devs_append(discdevs, dev);
+
+			if (!discdevs) {
+				r = LIBUSB_ERROR_NO_MEM;
+				break;
+			}
+		}
+		usbi_mutex_unlock(&ctx->usb_devs_lock);
+	} else {
+		/* backend does not provide hotplug support */
+		r = usbi_backend->get_device_list(ctx, &discdevs);
+	}
+
+	if (r < 0) {
+		len = r;
+		goto out;
+	}
+
+	/* convert discovered_devs into a list */
+	len = discdevs->len;
+	ret = calloc(len + 1, sizeof(struct libusb_device *));
+	if (!ret) {
+		len = LIBUSB_ERROR_NO_MEM;
+		goto out;
+	}
+
+	ret[len] = NULL;
+	for (i = 0; i < len; i++) {
+		struct libusb_device *dev = discdevs->devices[i];
+		ret[i] = libusb_ref_device(dev);
+	}
+	*list = ret;
+
+out:
+	if (discdevs)
+		discovered_devs_free(discdevs);
+	return len;
+}
+
+/** \ingroup libusb_dev
+ * Frees a list of devices previously discovered using
+ * libusb_get_device_list(). If the unref_devices parameter is set, the
+ * reference count of each device in the list is decremented by 1.
+ * \param list the list to free
+ * \param unref_devices whether to unref the devices in the list
+ */
+void API_EXPORTED libusb_free_device_list(libusb_device **list,
+	int unref_devices)
+{
+	if (!list)
+		return;
+
+	if (unref_devices) {
+		int i = 0;
+		struct libusb_device *dev;
+
+		while ((dev = list[i++]) != NULL)
+			libusb_unref_device(dev);
+	}
+	free(list);
+}
+
+/** \ingroup libusb_dev
+ * Get the number of the bus that a device is connected to.
+ * \param dev a device
+ * \returns the bus number
+ */
+uint8_t API_EXPORTED libusb_get_bus_number(libusb_device *dev)
+{
+	return dev->bus_number;
+}
+
+/** \ingroup libusb_dev
+ * Get the number of the port that a device is connected to.
+ * Unless the OS does something funky, or you are hot-plugging USB extension cards,
+ * the port number returned by this call is usually guaranteed to be uniquely tied
+ * to a physical port, meaning that different devices plugged on the same physical
+ * port should return the same port number.
+ *
+ * But outside of this, there is no guarantee that the port number returned by this
+ * call will remain the same, or even match the order in which ports have been
+ * numbered by the HUB/HCD manufacturer.
+ *
+ * \param dev a device
+ * \returns the port number (0 if not available)
+ */
+uint8_t API_EXPORTED libusb_get_port_number(libusb_device *dev)
+{
+	return dev->port_number;
+}
+
+/** \ingroup libusb_dev
+ * Get the list of all port numbers from root for the specified device
+ *
+ * Since version 1.0.16, \ref LIBUSB_API_VERSION >= 0x01000102
+ * \param dev a device
+ * \param port_numbers the array that should contain the port numbers
+ * \param port_numbers_len the maximum length of the array. As per the USB 3.0
+ * specs, the current maximum limit for the depth is 7.
+ * \returns the number of elements filled
+ * \returns LIBUSB_ERROR_OVERFLOW if the array is too small
+ */
+int API_EXPORTED libusb_get_port_numbers(libusb_device *dev,
+	uint8_t* port_numbers, int port_numbers_len)
+{
+	int i = port_numbers_len;
+	struct libusb_context *ctx = DEVICE_CTX(dev);
+
+	if (port_numbers_len <= 0)
+		return LIBUSB_ERROR_INVALID_PARAM;
+
+	// HCDs can be listed as devices with port #0
+	while((dev) && (dev->port_number != 0)) {
+		if (--i < 0) {
+			usbi_warn(ctx, "port numbers array is too small");
+			return LIBUSB_ERROR_OVERFLOW;
+		}
+		port_numbers[i] = dev->port_number;
+		dev = dev->parent_dev;
+	}
+	if (i < port_numbers_len)
+		memmove(port_numbers, &port_numbers[i], port_numbers_len - i);
+	return port_numbers_len - i;
+}
+
+/** \ingroup libusb_dev
+ * Deprecated please use libusb_get_port_numbers instead.
+ */
+int API_EXPORTED libusb_get_port_path(libusb_context *ctx, libusb_device *dev,
+	uint8_t* port_numbers, uint8_t port_numbers_len)
+{
+	UNUSED(ctx);
+
+	return libusb_get_port_numbers(dev, port_numbers, port_numbers_len);
+}
+
+/** \ingroup libusb_dev
+ * Get the the parent from the specified device.
+ * \param dev a device
+ * \returns the device parent or NULL if not available
+ * You should issue a \ref libusb_get_device_list() before calling this
+ * function and make sure that you only access the parent before issuing
+ * \ref libusb_free_device_list(). The reason is that libusb currently does
+ * not maintain a permanent list of device instances, and therefore can
+ * only guarantee that parents are fully instantiated within a 
+ * libusb_get_device_list() - libusb_free_device_list() block.
+ */
+DEFAULT_VISIBILITY
+libusb_device * LIBUSB_CALL libusb_get_parent(libusb_device *dev)
+{
+	return dev->parent_dev;
+}
+
+/** \ingroup libusb_dev
+ * Get the address of the device on the bus it is connected to.
+ * \param dev a device
+ * \returns the device address
+ */
+uint8_t API_EXPORTED libusb_get_device_address(libusb_device *dev)
+{
+	return dev->device_address;
+}
+
+/** \ingroup libusb_dev
+ * Get the negotiated connection speed for a device.
+ * \param dev a device
+ * \returns a \ref libusb_speed code, where LIBUSB_SPEED_UNKNOWN means that
+ * the OS doesn't know or doesn't support returning the negotiated speed.
+ */
+int API_EXPORTED libusb_get_device_speed(libusb_device *dev)
+{
+	return dev->speed;
+}
+
+static const struct libusb_endpoint_descriptor *find_endpoint(
+	struct libusb_config_descriptor *config, unsigned char endpoint)
+{
+	int iface_idx;
+	for (iface_idx = 0; iface_idx < config->bNumInterfaces; iface_idx++) {
+		const struct libusb_interface *iface = &config->interface[iface_idx];
+		int altsetting_idx;
+
+		for (altsetting_idx = 0; altsetting_idx < iface->num_altsetting;
+				altsetting_idx++) {
+			const struct libusb_interface_descriptor *altsetting
+				= &iface->altsetting[altsetting_idx];
+			int ep_idx;
+
+			for (ep_idx = 0; ep_idx < altsetting->bNumEndpoints; ep_idx++) {
+				const struct libusb_endpoint_descriptor *ep =
+					&altsetting->endpoint[ep_idx];
+				if (ep->bEndpointAddress == endpoint)
+					return ep;
+			}
+		}
+	}
+	return NULL;
+}
+
+/** \ingroup libusb_dev
+ * Convenience function to retrieve the wMaxPacketSize value for a particular
+ * endpoint in the active device configuration.
+ *
+ * This function was originally intended to be of assistance when setting up
+ * isochronous transfers, but a design mistake resulted in this function
+ * instead. It simply returns the wMaxPacketSize value without considering
+ * its contents. If you're dealing with isochronous transfers, you probably
+ * want libusb_get_max_iso_packet_size() instead.
+ *
+ * \param dev a device
+ * \param endpoint address of the endpoint in question
+ * \returns the wMaxPacketSize value
+ * \returns LIBUSB_ERROR_NOT_FOUND if the endpoint does not exist
+ * \returns LIBUSB_ERROR_OTHER on other failure
+ */
+int API_EXPORTED libusb_get_max_packet_size(libusb_device *dev,
+	unsigned char endpoint)
+{
+	struct libusb_config_descriptor *config;
+	const struct libusb_endpoint_descriptor *ep;
+	int r;
+
+	r = libusb_get_active_config_descriptor(dev, &config);
+	if (r < 0) {
+		usbi_err(DEVICE_CTX(dev),
+			"could not retrieve active config descriptor");
+		return LIBUSB_ERROR_OTHER;
+	}
+
+	ep = find_endpoint(config, endpoint);
+	if (!ep) {
+		r = LIBUSB_ERROR_NOT_FOUND;
+		goto out;
+	}
+
+	r = ep->wMaxPacketSize;
+
+out:
+	libusb_free_config_descriptor(config);
+	return r;
+}
+
+/** \ingroup libusb_dev
+ * Calculate the maximum packet size which a specific endpoint is capable is
+ * sending or receiving in the duration of 1 microframe
+ *
+ * Only the active configuration is examined. The calculation is based on the
+ * wMaxPacketSize field in the endpoint descriptor as described in section
+ * 9.6.6 in the USB 2.0 specifications.
+ *
+ * If acting on an isochronous or interrupt endpoint, this function will
+ * multiply the value found in bits 0:10 by the number of transactions per
+ * microframe (determined by bits 11:12). Otherwise, this function just
+ * returns the numeric value found in bits 0:10.
+ *
+ * This function is useful for setting up isochronous transfers, for example
+ * you might pass the return value from this function to
+ * libusb_set_iso_packet_lengths() in order to set the length field of every
+ * isochronous packet in a transfer.
+ *
+ * Since v1.0.3.
+ *
+ * \param dev a device
+ * \param endpoint address of the endpoint in question
+ * \returns the maximum packet size which can be sent/received on this endpoint
+ * \returns LIBUSB_ERROR_NOT_FOUND if the endpoint does not exist
+ * \returns LIBUSB_ERROR_OTHER on other failure
+ */
+int API_EXPORTED libusb_get_max_iso_packet_size(libusb_device *dev,
+	unsigned char endpoint)
+{
+	struct libusb_config_descriptor *config;
+	const struct libusb_endpoint_descriptor *ep;
+	enum libusb_transfer_type ep_type;
+	uint16_t val;
+	int r;
+
+	r = libusb_get_active_config_descriptor(dev, &config);
+	if (r < 0) {
+		usbi_err(DEVICE_CTX(dev),
+			"could not retrieve active config descriptor");
+		return LIBUSB_ERROR_OTHER;
+	}
+
+	ep = find_endpoint(config, endpoint);
+	if (!ep) {
+		r = LIBUSB_ERROR_NOT_FOUND;
+		goto out;
+	}
+
+	val = ep->wMaxPacketSize;
+	ep_type = (enum libusb_transfer_type) (ep->bmAttributes & 0x3);
+
+	r = val & 0x07ff;
+	if (ep_type == LIBUSB_TRANSFER_TYPE_ISOCHRONOUS
+			|| ep_type == LIBUSB_TRANSFER_TYPE_INTERRUPT)
+		r *= (1 + ((val >> 11) & 3));
+
+out:
+	libusb_free_config_descriptor(config);
+	return r;
+}
+
+/** \ingroup libusb_dev
+ * Increment the reference count of a device.
+ * \param dev the device to reference
+ * \returns the same device
+ */
+DEFAULT_VISIBILITY
+libusb_device * LIBUSB_CALL libusb_ref_device(libusb_device *dev)
+{
+	usbi_mutex_lock(&dev->lock);
+	dev->refcnt++;
+	usbi_mutex_unlock(&dev->lock);
+	return dev;
+}
+
+/** \ingroup libusb_dev
+ * Decrement the reference count of a device. If the decrement operation
+ * causes the reference count to reach zero, the device shall be destroyed.
+ * \param dev the device to unreference
+ */
+void API_EXPORTED libusb_unref_device(libusb_device *dev)
+{
+	int refcnt;
+
+	if (!dev)
+		return;
+
+	usbi_mutex_lock(&dev->lock);
+	refcnt = --dev->refcnt;
+	usbi_mutex_unlock(&dev->lock);
+
+	if (refcnt == 0) {
+		usbi_dbg("destroy device %d.%d", dev->bus_number, dev->device_address);
+
+		libusb_unref_device(dev->parent_dev);
+
+		if (usbi_backend->destroy_device)
+			usbi_backend->destroy_device(dev);
+
+		if (!libusb_has_capability(LIBUSB_CAP_HAS_HOTPLUG)) {
+			/* backend does not support hotplug */
+			usbi_disconnect_device(dev);
+		}
+
+		usbi_mutex_destroy(&dev->lock);
+		free(dev);
+	}
+}
+
+/*
+ * Signal the event pipe so that the event handling thread will be
+ * interrupted to process an internal event.
+ */
+int usbi_signal_event(struct libusb_context *ctx)
+{
+	unsigned char dummy = 1;
+	ssize_t r;
+
+	/* write some data on event pipe to interrupt event handlers */
+	r = usbi_write(ctx->event_pipe[1], &dummy, sizeof(dummy));
+	if (r != sizeof(dummy)) {
+		usbi_warn(ctx, "internal signalling write failed");
+		return LIBUSB_ERROR_IO;
+	}
+
+	return 0;
+}
+
+/*
+ * Clear the event pipe so that the event handling will no longer be
+ * interrupted.
+ */
+int usbi_clear_event(struct libusb_context *ctx)
+{
+	unsigned char dummy;
+	ssize_t r;
+
+	/* read some data on event pipe to clear it */
+	r = usbi_read(ctx->event_pipe[0], &dummy, sizeof(dummy));
+	if (r != sizeof(dummy)) {
+		usbi_warn(ctx, "internal signalling read failed");
+		return LIBUSB_ERROR_IO;
+	}
+
+	return 0;
+}
+
+/** \ingroup libusb_dev
+ * Open a device and obtain a device handle. A handle allows you to perform
+ * I/O on the device in question.
+ *
+ * Internally, this function adds a reference to the device and makes it
+ * available to you through libusb_get_device(). This reference is removed
+ * during libusb_close().
+ *
+ * This is a non-blocking function; no requests are sent over the bus.
+ *
+ * \param dev the device to open
+ * \param dev_handle output location for the returned device handle pointer. Only
+ * populated when the return code is 0.
+ * \returns 0 on success
+ * \returns LIBUSB_ERROR_NO_MEM on memory allocation failure
+ * \returns LIBUSB_ERROR_ACCESS if the user has insufficient permissions
+ * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
+ * \returns another LIBUSB_ERROR code on other failure
+ */
+int API_EXPORTED libusb_open(libusb_device *dev,
+	libusb_device_handle **dev_handle)
+{
+	struct libusb_context *ctx = DEVICE_CTX(dev);
+	struct libusb_device_handle *_dev_handle;
+	size_t priv_size = usbi_backend->device_handle_priv_size;
+	int r;
+	usbi_dbg("open %d.%d", dev->bus_number, dev->device_address);
+
+	if (!dev->attached) {
+		return LIBUSB_ERROR_NO_DEVICE;
+	}
+
+	_dev_handle = malloc(sizeof(*_dev_handle) + priv_size);
+	if (!_dev_handle)
+		return LIBUSB_ERROR_NO_MEM;
+
+	r = usbi_mutex_init(&_dev_handle->lock);
+	if (r) {
+		free(_dev_handle);
+		return LIBUSB_ERROR_OTHER;
+	}
+
+	_dev_handle->dev = libusb_ref_device(dev);
+	_dev_handle->auto_detach_kernel_driver = 0;
+	_dev_handle->claimed_interfaces = 0;
+	memset(&_dev_handle->os_priv, 0, priv_size);
+
+	r = usbi_backend->open(_dev_handle);
+	if (r < 0) {
+		usbi_dbg("open %d.%d returns %d", dev->bus_number, dev->device_address, r);
+		libusb_unref_device(dev);
+		usbi_mutex_destroy(&_dev_handle->lock);
+		free(_dev_handle);
+		return r;
+	}
+
+	usbi_mutex_lock(&ctx->open_devs_lock);
+	list_add(&_dev_handle->list, &ctx->open_devs);
+	usbi_mutex_unlock(&ctx->open_devs_lock);
+	*dev_handle = _dev_handle;
+
+	return 0;
+}
+
+/** \ingroup libusb_dev
+ * Convenience function for finding a device with a particular
+ * <tt>idVendor</tt>/<tt>idProduct</tt> combination. This function is intended
+ * for those scenarios where you are using libusb to knock up a quick test
+ * application - it allows you to avoid calling libusb_get_device_list() and
+ * worrying about traversing/freeing the list.
+ *
+ * This function has limitations and is hence not intended for use in real
+ * applications: if multiple devices have the same IDs it will only
+ * give you the first one, etc.
+ *
+ * \param ctx the context to operate on, or NULL for the default context
+ * \param vendor_id the idVendor value to search for
+ * \param product_id the idProduct value to search for
+ * \returns a device handle for the first found device, or NULL on error
+ * or if the device could not be found. */
+DEFAULT_VISIBILITY
+libusb_device_handle * LIBUSB_CALL libusb_open_device_with_vid_pid(
+	libusb_context *ctx, uint16_t vendor_id, uint16_t product_id)
+{
+	struct libusb_device **devs;
+	struct libusb_device *found = NULL;
+	struct libusb_device *dev;
+	struct libusb_device_handle *dev_handle = NULL;
+	size_t i = 0;
+	int r;
+
+	if (libusb_get_device_list(ctx, &devs) < 0)
+		return NULL;
+
+	while ((dev = devs[i++]) != NULL) {
+		struct libusb_device_descriptor desc;
+		r = libusb_get_device_descriptor(dev, &desc);
+		if (r < 0)
+			goto out;
+		if (desc.idVendor == vendor_id && desc.idProduct == product_id) {
+			found = dev;
+			break;
+		}
+	}
+
+	if (found) {
+		r = libusb_open(found, &dev_handle);
+		if (r < 0)
+			dev_handle = NULL;
+	}
+
+out:
+	libusb_free_device_list(devs, 1);
+	return dev_handle;
+}
+
+static void do_close(struct libusb_context *ctx,
+	struct libusb_device_handle *dev_handle)
+{
+	struct usbi_transfer *itransfer;
+	struct usbi_transfer *tmp;
+
+	/* remove any transfers in flight that are for this device */
+	usbi_mutex_lock(&ctx->flying_transfers_lock);
+
+	/* safe iteration because transfers may be being deleted */
+	list_for_each_entry_safe(itransfer, tmp, &ctx->flying_transfers, list, struct usbi_transfer) {
+		struct libusb_transfer *transfer =
+			USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+
+		if (transfer->dev_handle != dev_handle)
+			continue;
+
+		usbi_mutex_lock(&itransfer->lock);
+		if (!(itransfer->state_flags & USBI_TRANSFER_DEVICE_DISAPPEARED)) {
+			usbi_err(ctx, "Device handle closed while transfer was still being processed, but the device is still connected as far as we know");
+
+			if (itransfer->state_flags & USBI_TRANSFER_CANCELLING)
+				usbi_warn(ctx, "A cancellation for an in-flight transfer hasn't completed but closing the device handle");
+			else
+				usbi_err(ctx, "A cancellation hasn't even been scheduled on the transfer for which the device is closing");
+		}
+		usbi_mutex_unlock(&itransfer->lock);
+
+		/* remove from the list of in-flight transfers and make sure
+		 * we don't accidentally use the device handle in the future
+		 * (or that such accesses will be easily caught and identified as a crash)
+		 */
+		list_del(&itransfer->list);
+		transfer->dev_handle = NULL;
+
+		/* it is up to the user to free up the actual transfer struct.  this is
+		 * just making sure that we don't attempt to process the transfer after
+		 * the device handle is invalid
+		 */
+		usbi_dbg("Removed transfer %p from the in-flight list because device handle %p closed",
+			 transfer, dev_handle);
+	}
+	usbi_mutex_unlock(&ctx->flying_transfers_lock);
+
+	usbi_mutex_lock(&ctx->open_devs_lock);
+	list_del(&dev_handle->list);
+	usbi_mutex_unlock(&ctx->open_devs_lock);
+
+	usbi_backend->close(dev_handle);
+	libusb_unref_device(dev_handle->dev);
+	usbi_mutex_destroy(&dev_handle->lock);
+	free(dev_handle);
+}
+
+/** \ingroup libusb_dev
+ * Close a device handle. Should be called on all open handles before your
+ * application exits.
+ *
+ * Internally, this function destroys the reference that was added by
+ * libusb_open() on the given device.
+ *
+ * This is a non-blocking function; no requests are sent over the bus.
+ *
+ * \param dev_handle the device handle to close
+ */
+void API_EXPORTED libusb_close(libusb_device_handle *dev_handle)
+{
+	struct libusb_context *ctx;
+	int handling_events;
+	int pending_events;
+
+	if (!dev_handle)
+		return;
+	usbi_dbg("");
+
+	ctx = HANDLE_CTX(dev_handle);
+	handling_events = usbi_handling_events(ctx);
+
+	/* Similarly to libusb_open(), we want to interrupt all event handlers
+	 * at this point. More importantly, we want to perform the actual close of
+	 * the device while holding the event handling lock (preventing any other
+	 * thread from doing event handling) because we will be removing a file
+	 * descriptor from the polling loop. If this is being called by the current
+	 * event handler, we can bypass the interruption code because we already
+	 * hold the event handling lock. */
+
+	if (!handling_events) {
+		/* Record that we are closing a device.
+		 * Only signal an event if there are no prior pending events. */
+		usbi_mutex_lock(&ctx->event_data_lock);
+		pending_events = usbi_pending_events(ctx);
+		ctx->device_close++;
+		if (!pending_events)
+			usbi_signal_event(ctx);
+		usbi_mutex_unlock(&ctx->event_data_lock);
+
+		/* take event handling lock */
+		libusb_lock_events(ctx);
+	}
+
+	/* Close the device */
+	do_close(ctx, dev_handle);
+
+	if (!handling_events) {
+		/* We're done with closing this device.
+		 * Clear the event pipe if there are no further pending events. */
+		usbi_mutex_lock(&ctx->event_data_lock);
+		ctx->device_close--;
+		pending_events = usbi_pending_events(ctx);
+		if (!pending_events)
+			usbi_clear_event(ctx);
+		usbi_mutex_unlock(&ctx->event_data_lock);
+
+		/* Release event handling lock and wake up event waiters */
+		libusb_unlock_events(ctx);
+	}
+}
+
+/** \ingroup libusb_dev
+ * Get the underlying device for a device handle. This function does not modify
+ * the reference count of the returned device, so do not feel compelled to
+ * unreference it when you are done.
+ * \param dev_handle a device handle
+ * \returns the underlying device
+ */
+DEFAULT_VISIBILITY
+libusb_device * LIBUSB_CALL libusb_get_device(libusb_device_handle *dev_handle)
+{
+	return dev_handle->dev;
+}
+
+/** \ingroup libusb_dev
+ * Determine the bConfigurationValue of the currently active configuration.
+ *
+ * You could formulate your own control request to obtain this information,
+ * but this function has the advantage that it may be able to retrieve the
+ * information from operating system caches (no I/O involved).
+ *
+ * If the OS does not cache this information, then this function will block
+ * while a control transfer is submitted to retrieve the information.
+ *
+ * This function will return a value of 0 in the <tt>config</tt> output
+ * parameter if the device is in unconfigured state.
+ *
+ * \param dev_handle a device handle
+ * \param config output location for the bConfigurationValue of the active
+ * configuration (only valid for return code 0)
+ * \returns 0 on success
+ * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
+ * \returns another LIBUSB_ERROR code on other failure
+ */
+int API_EXPORTED libusb_get_configuration(libusb_device_handle *dev_handle,
+	int *config)
+{
+	int r = LIBUSB_ERROR_NOT_SUPPORTED;
+
+	usbi_dbg("");
+	if (usbi_backend->get_configuration)
+		r = usbi_backend->get_configuration(dev_handle, config);
+
+	if (r == LIBUSB_ERROR_NOT_SUPPORTED) {
+		uint8_t tmp = 0;
+		usbi_dbg("falling back to control message");
+		r = libusb_control_transfer(dev_handle, LIBUSB_ENDPOINT_IN,
+			LIBUSB_REQUEST_GET_CONFIGURATION, 0, 0, &tmp, 1, 1000);
+		if (r == 0) {
+			usbi_err(HANDLE_CTX(dev_handle), "zero bytes returned in ctrl transfer?");
+			r = LIBUSB_ERROR_IO;
+		} else if (r == 1) {
+			r = 0;
+			*config = tmp;
+		} else {
+			usbi_dbg("control failed, error %d", r);
+		}
+	}
+
+	if (r == 0)
+		usbi_dbg("active config %d", *config);
+
+	return r;
+}
+
+/** \ingroup libusb_dev
+ * Set the active configuration for a device.
+ *
+ * The operating system may or may not have already set an active
+ * configuration on the device. It is up to your application to ensure the
+ * correct configuration is selected before you attempt to claim interfaces
+ * and perform other operations.
+ *
+ * If you call this function on a device already configured with the selected
+ * configuration, then this function will act as a lightweight device reset:
+ * it will issue a SET_CONFIGURATION request using the current configuration,
+ * causing most USB-related device state to be reset (altsetting reset to zero,
+ * endpoint halts cleared, toggles reset).
+ *
+ * You cannot change/reset configuration if your application has claimed
+ * interfaces. It is advised to set the desired configuration before claiming
+ * interfaces.
+ *
+ * Alternatively you can call libusb_release_interface() first. Note if you
+ * do things this way you must ensure that auto_detach_kernel_driver for
+ * <tt>dev</tt> is 0, otherwise the kernel driver will be re-attached when you
+ * release the interface(s).
+ *
+ * You cannot change/reset configuration if other applications or drivers have
+ * claimed interfaces.
+ *
+ * A configuration value of -1 will put the device in unconfigured state.
+ * The USB specifications state that a configuration value of 0 does this,
+ * however buggy devices exist which actually have a configuration 0.
+ *
+ * You should always use this function rather than formulating your own
+ * SET_CONFIGURATION control request. This is because the underlying operating
+ * system needs to know when such changes happen.
+ *
+ * This is a blocking function.
+ *
+ * \param dev_handle a device handle
+ * \param configuration the bConfigurationValue of the configuration you
+ * wish to activate, or -1 if you wish to put the device in an unconfigured
+ * state
+ * \returns 0 on success
+ * \returns LIBUSB_ERROR_NOT_FOUND if the requested configuration does not exist
+ * \returns LIBUSB_ERROR_BUSY if interfaces are currently claimed
+ * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
+ * \returns another LIBUSB_ERROR code on other failure
+ * \see libusb_set_auto_detach_kernel_driver()
+ */
+int API_EXPORTED libusb_set_configuration(libusb_device_handle *dev_handle,
+	int configuration)
+{
+	usbi_dbg("configuration %d", configuration);
+	return usbi_backend->set_configuration(dev_handle, configuration);
+}
+
+/** \ingroup libusb_dev
+ * Claim an interface on a given device handle. You must claim the interface
+ * you wish to use before you can perform I/O on any of its endpoints.
+ *
+ * It is legal to attempt to claim an already-claimed interface, in which
+ * case libusb just returns 0 without doing anything.
+ *
+ * If auto_detach_kernel_driver is set to 1 for <tt>dev</tt>, the kernel driver
+ * will be detached if necessary, on failure the detach error is returned.
+ *
+ * Claiming of interfaces is a purely logical operation; it does not cause
+ * any requests to be sent over the bus. Interface claiming is used to
+ * instruct the underlying operating system that your application wishes
+ * to take ownership of the interface.
+ *
+ * This is a non-blocking function.
+ *
+ * \param dev_handle a device handle
+ * \param interface_number the <tt>bInterfaceNumber</tt> of the interface you
+ * wish to claim
+ * \returns 0 on success
+ * \returns LIBUSB_ERROR_NOT_FOUND if the requested interface does not exist
+ * \returns LIBUSB_ERROR_BUSY if another program or driver has claimed the
+ * interface
+ * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
+ * \returns a LIBUSB_ERROR code on other failure
+ * \see libusb_set_auto_detach_kernel_driver()
+ */
+int API_EXPORTED libusb_claim_interface(libusb_device_handle *dev_handle,
+	int interface_number)
+{
+	int r = 0;
+
+	usbi_dbg("interface %d", interface_number);
+	if (interface_number >= USB_MAXINTERFACES)
+		return LIBUSB_ERROR_INVALID_PARAM;
+
+	if (!dev_handle->dev->attached)
+		return LIBUSB_ERROR_NO_DEVICE;
+
+	usbi_mutex_lock(&dev_handle->lock);
+	if (dev_handle->claimed_interfaces & (1 << interface_number))
+		goto out;
+
+	r = usbi_backend->claim_interface(dev_handle, interface_number);
+	if (r == 0)
+		dev_handle->claimed_interfaces |= 1 << interface_number;
+
+out:
+	usbi_mutex_unlock(&dev_handle->lock);
+	return r;
+}
+
+/** \ingroup libusb_dev
+ * Release an interface previously claimed with libusb_claim_interface(). You
+ * should release all claimed interfaces before closing a device handle.
+ *
+ * This is a blocking function. A SET_INTERFACE control request will be sent
+ * to the device, resetting interface state to the first alternate setting.
+ *
+ * If auto_detach_kernel_driver is set to 1 for <tt>dev</tt>, the kernel
+ * driver will be re-attached after releasing the interface.
+ *
+ * \param dev_handle a device handle
+ * \param interface_number the <tt>bInterfaceNumber</tt> of the
+ * previously-claimed interface
+ * \returns 0 on success
+ * \returns LIBUSB_ERROR_NOT_FOUND if the interface was not claimed
+ * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
+ * \returns another LIBUSB_ERROR code on other failure
+ * \see libusb_set_auto_detach_kernel_driver()
+ */
+int API_EXPORTED libusb_release_interface(libusb_device_handle *dev_handle,
+	int interface_number)
+{
+	int r;
+
+	usbi_dbg("interface %d", interface_number);
+	if (interface_number >= USB_MAXINTERFACES)
+		return LIBUSB_ERROR_INVALID_PARAM;
+
+	usbi_mutex_lock(&dev_handle->lock);
+	if (!(dev_handle->claimed_interfaces & (1 << interface_number))) {
+		r = LIBUSB_ERROR_NOT_FOUND;
+		goto out;
+	}
+
+	r = usbi_backend->release_interface(dev_handle, interface_number);
+	if (r == 0)
+		dev_handle->claimed_interfaces &= ~(1 << interface_number);
+
+out:
+	usbi_mutex_unlock(&dev_handle->lock);
+	return r;
+}
+
+/** \ingroup libusb_dev
+ * Activate an alternate setting for an interface. The interface must have
+ * been previously claimed with libusb_claim_interface().
+ *
+ * You should always use this function rather than formulating your own
+ * SET_INTERFACE control request. This is because the underlying operating
+ * system needs to know when such changes happen.
+ *
+ * This is a blocking function.
+ *
+ * \param dev_handle a device handle
+ * \param interface_number the <tt>bInterfaceNumber</tt> of the
+ * previously-claimed interface
+ * \param alternate_setting the <tt>bAlternateSetting</tt> of the alternate
+ * setting to activate
+ * \returns 0 on success
+ * \returns LIBUSB_ERROR_NOT_FOUND if the interface was not claimed, or the
+ * requested alternate setting does not exist
+ * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
+ * \returns another LIBUSB_ERROR code on other failure
+ */
+int API_EXPORTED libusb_set_interface_alt_setting(libusb_device_handle *dev_handle,
+	int interface_number, int alternate_setting)
+{
+	usbi_dbg("interface %d altsetting %d",
+		interface_number, alternate_setting);
+	if (interface_number >= USB_MAXINTERFACES)
+		return LIBUSB_ERROR_INVALID_PARAM;
+
+	usbi_mutex_lock(&dev_handle->lock);
+	if (!dev_handle->dev->attached) {
+		usbi_mutex_unlock(&dev_handle->lock);
+		return LIBUSB_ERROR_NO_DEVICE;
+	}
+
+	if (!(dev_handle->claimed_interfaces & (1 << interface_number))) {
+		usbi_mutex_unlock(&dev_handle->lock);
+		return LIBUSB_ERROR_NOT_FOUND;
+	}
+	usbi_mutex_unlock(&dev_handle->lock);
+
+	return usbi_backend->set_interface_altsetting(dev_handle, interface_number,
+		alternate_setting);
+}
+
+/** \ingroup libusb_dev
+ * Clear the halt/stall condition for an endpoint. Endpoints with halt status
+ * are unable to receive or transmit data until the halt condition is stalled.
+ *
+ * You should cancel all pending transfers before attempting to clear the halt
+ * condition.
+ *
+ * This is a blocking function.
+ *
+ * \param dev_handle a device handle
+ * \param endpoint the endpoint to clear halt status
+ * \returns 0 on success
+ * \returns LIBUSB_ERROR_NOT_FOUND if the endpoint does not exist
+ * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
+ * \returns another LIBUSB_ERROR code on other failure
+ */
+int API_EXPORTED libusb_clear_halt(libusb_device_handle *dev_handle,
+	unsigned char endpoint)
+{
+	usbi_dbg("endpoint %x", endpoint);
+	if (!dev_handle->dev->attached)
+		return LIBUSB_ERROR_NO_DEVICE;
+
+	return usbi_backend->clear_halt(dev_handle, endpoint);
+}
+
+/** \ingroup libusb_dev
+ * Perform a USB port reset to reinitialize a device. The system will attempt
+ * to restore the previous configuration and alternate settings after the
+ * reset has completed.
+ *
+ * If the reset fails, the descriptors change, or the previous state cannot be
+ * restored, the device will appear to be disconnected and reconnected. This
+ * means that the device handle is no longer valid (you should close it) and
+ * rediscover the device. A return code of LIBUSB_ERROR_NOT_FOUND indicates
+ * when this is the case.
+ *
+ * This is a blocking function which usually incurs a noticeable delay.
+ *
+ * \param dev_handle a handle of the device to reset
+ * \returns 0 on success
+ * \returns LIBUSB_ERROR_NOT_FOUND if re-enumeration is required, or if the
+ * device has been disconnected
+ * \returns another LIBUSB_ERROR code on other failure
+ */
+int API_EXPORTED libusb_reset_device(libusb_device_handle *dev_handle)
+{
+	usbi_dbg("");
+	if (!dev_handle->dev->attached)
+		return LIBUSB_ERROR_NO_DEVICE;
+
+	return usbi_backend->reset_device(dev_handle);
+}
+
+/** \ingroup libusb_asyncio
+ * Allocate up to num_streams usb bulk streams on the specified endpoints. This
+ * function takes an array of endpoints rather then a single endpoint because
+ * some protocols require that endpoints are setup with similar stream ids.
+ * All endpoints passed in must belong to the same interface.
+ *
+ * Note this function may return less streams then requested. Also note that the
+ * same number of streams are allocated for each endpoint in the endpoint array.
+ *
+ * Stream id 0 is reserved, and should not be used to communicate with devices.
+ * If libusb_alloc_streams() returns with a value of N, you may use stream ids
+ * 1 to N.
+ *
+ * Since version 1.0.19, \ref LIBUSB_API_VERSION >= 0x01000103
+ *
+ * \param dev_handle a device handle
+ * \param num_streams number of streams to try to allocate
+ * \param endpoints array of endpoints to allocate streams on
+ * \param num_endpoints length of the endpoints array
+ * \returns number of streams allocated, or a LIBUSB_ERROR code on failure
+ */
+int API_EXPORTED libusb_alloc_streams(libusb_device_handle *dev_handle,
+	uint32_t num_streams, unsigned char *endpoints, int num_endpoints)
+{
+	usbi_dbg("streams %u eps %d", (unsigned) num_streams, num_endpoints);
+
+	if (!dev_handle->dev->attached)
+		return LIBUSB_ERROR_NO_DEVICE;
+
+	if (usbi_backend->alloc_streams)
+		return usbi_backend->alloc_streams(dev_handle, num_streams, endpoints,
+						   num_endpoints);
+	else
+		return LIBUSB_ERROR_NOT_SUPPORTED;
+}
+
+/** \ingroup libusb_asyncio
+ * Free usb bulk streams allocated with libusb_alloc_streams().
+ *
+ * Note streams are automatically free-ed when releasing an interface.
+ *
+ * Since version 1.0.19, \ref LIBUSB_API_VERSION >= 0x01000103
+ *
+ * \param dev_handle a device handle
+ * \param endpoints array of endpoints to free streams on
+ * \param num_endpoints length of the endpoints array
+ * \returns LIBUSB_SUCCESS, or a LIBUSB_ERROR code on failure
+ */
+int API_EXPORTED libusb_free_streams(libusb_device_handle *dev_handle,
+	unsigned char *endpoints, int num_endpoints)
+{
+	usbi_dbg("eps %d", num_endpoints);
+
+	if (!dev_handle->dev->attached)
+		return LIBUSB_ERROR_NO_DEVICE;
+
+	if (usbi_backend->free_streams)
+		return usbi_backend->free_streams(dev_handle, endpoints,
+						  num_endpoints);
+	else
+		return LIBUSB_ERROR_NOT_SUPPORTED;
+}
+
+/** \ingroup libusb_asyncio
+ * Attempts to allocate a block of persistent DMA memory suitable for transfers
+ * against the given device. If successful, will return a block of memory
+ * that is suitable for use as "buffer" in \ref libusb_transfer against this
+ * device. Using this memory instead of regular memory means that the host
+ * controller can use DMA directly into the buffer to increase performance, and
+ * also that transfers can no longer fail due to kernel memory fragmentation.
+ *
+ * Note that this means you should not modify this memory (or even data on
+ * the same cache lines) when a transfer is in progress, although it is legal
+ * to have several transfers going on within the same memory block.
+ *
+ * Will return NULL on failure. Many systems do not support such zerocopy
+ * and will always return NULL. Memory allocated with this function must be
+ * freed with \ref libusb_dev_mem_free. Specifically, this means that the
+ * flag \ref LIBUSB_TRANSFER_FREE_BUFFER cannot be used to free memory allocated
+ * with this function.
+ *
+ * Since version 1.0.21, \ref LIBUSB_API_VERSION >= 0x01000105
+ *
+ * \param dev_handle a device handle
+ * \param length size of desired data buffer
+ * \returns a pointer to the newly allocated memory, or NULL on failure
+ */
+DEFAULT_VISIBILITY
+unsigned char * LIBUSB_CALL libusb_dev_mem_alloc(libusb_device_handle *dev_handle,
+        size_t length)
+{
+	if (!dev_handle->dev->attached)
+		return NULL;
+
+	if (usbi_backend->dev_mem_alloc)
+		return usbi_backend->dev_mem_alloc(dev_handle, length);
+	else
+		return NULL;
+}
+
+/** \ingroup libusb_asyncio
+ * Free device memory allocated with libusb_dev_mem_alloc().
+ *
+ * \param dev_handle a device handle
+ * \param buffer pointer to the previously allocated memory
+ * \param length size of previously allocated memory
+ * \returns LIBUSB_SUCCESS, or a LIBUSB_ERROR code on failure
+ */
+int API_EXPORTED libusb_dev_mem_free(libusb_device_handle *dev_handle,
+	unsigned char *buffer, size_t length)
+{
+	if (usbi_backend->dev_mem_free)
+		return usbi_backend->dev_mem_free(dev_handle, buffer, length);
+	else
+		return LIBUSB_ERROR_NOT_SUPPORTED;
+}
+
+/** \ingroup libusb_dev
+ * Determine if a kernel driver is active on an interface. If a kernel driver
+ * is active, you cannot claim the interface, and libusb will be unable to
+ * perform I/O.
+ *
+ * This functionality is not available on Windows.
+ *
+ * \param dev_handle a device handle
+ * \param interface_number the interface to check
+ * \returns 0 if no kernel driver is active
+ * \returns 1 if a kernel driver is active
+ * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
+ * \returns LIBUSB_ERROR_NOT_SUPPORTED on platforms where the functionality
+ * is not available
+ * \returns another LIBUSB_ERROR code on other failure
+ * \see libusb_detach_kernel_driver()
+ */
+int API_EXPORTED libusb_kernel_driver_active(libusb_device_handle *dev_handle,
+	int interface_number)
+{
+	usbi_dbg("interface %d", interface_number);
+
+	if (!dev_handle->dev->attached)
+		return LIBUSB_ERROR_NO_DEVICE;
+
+	if (usbi_backend->kernel_driver_active)
+		return usbi_backend->kernel_driver_active(dev_handle, interface_number);
+	else
+		return LIBUSB_ERROR_NOT_SUPPORTED;
+}
+
+/** \ingroup libusb_dev
+ * Detach a kernel driver from an interface. If successful, you will then be
+ * able to claim the interface and perform I/O.
+ *
+ * This functionality is not available on Darwin or Windows.
+ *
+ * Note that libusb itself also talks to the device through a special kernel
+ * driver, if this driver is already attached to the device, this call will
+ * not detach it and return LIBUSB_ERROR_NOT_FOUND.
+ *
+ * \param dev_handle a device handle
+ * \param interface_number the interface to detach the driver from
+ * \returns 0 on success
+ * \returns LIBUSB_ERROR_NOT_FOUND if no kernel driver was active
+ * \returns LIBUSB_ERROR_INVALID_PARAM if the interface does not exist
+ * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
+ * \returns LIBUSB_ERROR_NOT_SUPPORTED on platforms where the functionality
+ * is not available
+ * \returns another LIBUSB_ERROR code on other failure
+ * \see libusb_kernel_driver_active()
+ */
+int API_EXPORTED libusb_detach_kernel_driver(libusb_device_handle *dev_handle,
+	int interface_number)
+{
+	usbi_dbg("interface %d", interface_number);
+
+	if (!dev_handle->dev->attached)
+		return LIBUSB_ERROR_NO_DEVICE;
+
+	if (usbi_backend->detach_kernel_driver)
+		return usbi_backend->detach_kernel_driver(dev_handle, interface_number);
+	else
+		return LIBUSB_ERROR_NOT_SUPPORTED;
+}
+
+/** \ingroup libusb_dev
+ * Re-attach an interface's kernel driver, which was previously detached
+ * using libusb_detach_kernel_driver(). This call is only effective on
+ * Linux and returns LIBUSB_ERROR_NOT_SUPPORTED on all other platforms.
+ *
+ * This functionality is not available on Darwin or Windows.
+ *
+ * \param dev_handle a device handle
+ * \param interface_number the interface to attach the driver from
+ * \returns 0 on success
+ * \returns LIBUSB_ERROR_NOT_FOUND if no kernel driver was active
+ * \returns LIBUSB_ERROR_INVALID_PARAM if the interface does not exist
+ * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
+ * \returns LIBUSB_ERROR_NOT_SUPPORTED on platforms where the functionality
+ * is not available
+ * \returns LIBUSB_ERROR_BUSY if the driver cannot be attached because the
+ * interface is claimed by a program or driver
+ * \returns another LIBUSB_ERROR code on other failure
+ * \see libusb_kernel_driver_active()
+ */
+int API_EXPORTED libusb_attach_kernel_driver(libusb_device_handle *dev_handle,
+	int interface_number)
+{
+	usbi_dbg("interface %d", interface_number);
+
+	if (!dev_handle->dev->attached)
+		return LIBUSB_ERROR_NO_DEVICE;
+
+	if (usbi_backend->attach_kernel_driver)
+		return usbi_backend->attach_kernel_driver(dev_handle, interface_number);
+	else
+		return LIBUSB_ERROR_NOT_SUPPORTED;
+}
+
+/** \ingroup libusb_dev
+ * Enable/disable libusb's automatic kernel driver detachment. When this is
+ * enabled libusb will automatically detach the kernel driver on an interface
+ * when claiming the interface, and attach it when releasing the interface.
+ *
+ * Automatic kernel driver detachment is disabled on newly opened device
+ * handles by default.
+ *
+ * On platforms which do not have LIBUSB_CAP_SUPPORTS_DETACH_KERNEL_DRIVER
+ * this function will return LIBUSB_ERROR_NOT_SUPPORTED, and libusb will
+ * continue as if this function was never called.
+ *
+ * \param dev_handle a device handle
+ * \param enable whether to enable or disable auto kernel driver detachment
+ *
+ * \returns LIBUSB_SUCCESS on success
+ * \returns LIBUSB_ERROR_NOT_SUPPORTED on platforms where the functionality
+ * is not available
+ * \see libusb_claim_interface()
+ * \see libusb_release_interface()
+ * \see libusb_set_configuration()
+ */
+int API_EXPORTED libusb_set_auto_detach_kernel_driver(
+	libusb_device_handle *dev_handle, int enable)
+{
+	if (!(usbi_backend->caps & USBI_CAP_SUPPORTS_DETACH_KERNEL_DRIVER))
+		return LIBUSB_ERROR_NOT_SUPPORTED;
+
+	dev_handle->auto_detach_kernel_driver = enable;
+	return LIBUSB_SUCCESS;
+}
+
+/** \ingroup libusb_lib
+ * Set log message verbosity.
+ *
+ * The default level is LIBUSB_LOG_LEVEL_NONE, which means no messages are ever
+ * printed. If you choose to increase the message verbosity level, ensure
+ * that your application does not close the stdout/stderr file descriptors.
+ *
+ * You are advised to use level LIBUSB_LOG_LEVEL_WARNING. libusb is conservative
+ * with its message logging and most of the time, will only log messages that
+ * explain error conditions and other oddities. This will help you debug
+ * your software.
+ *
+ * If the LIBUSB_DEBUG environment variable was set when libusb was
+ * initialized, this function does nothing: the message verbosity is fixed
+ * to the value in the environment variable.
+ *
+ * If libusb was compiled without any message logging, this function does
+ * nothing: you'll never get any messages.
+ *
+ * If libusb was compiled with verbose debug message logging, this function
+ * does nothing: you'll always get messages from all levels.
+ *
+ * \param ctx the context to operate on, or NULL for the default context
+ * \param level debug level to set
+ */
+void API_EXPORTED libusb_set_debug(libusb_context *ctx, int level)
+{
+	USBI_GET_CONTEXT(ctx);
+	if (!ctx->debug_fixed)
+		ctx->debug = level;
+}
+
+/** \ingroup libusb_lib
+ * Initialize libusb. This function must be called before calling any other
+ * libusb function.
+ *
+ * If you do not provide an output location for a context pointer, a default
+ * context will be created. If there was already a default context, it will
+ * be reused (and nothing will be initialized/reinitialized).
+ *
+ * \param context Optional output location for context pointer.
+ * Only valid on return code 0.
+ * \returns 0 on success, or a LIBUSB_ERROR code on failure
+ * \see libusb_contexts
+ */
+int API_EXPORTED libusb_init(libusb_context **context)
+{
+	struct libusb_device *dev, *next;
+	char *dbg = getenv("LIBUSB_DEBUG");
+	struct libusb_context *ctx;
+	static int first_init = 1;
+	int r = 0;
+
+	usbi_mutex_static_lock(&default_context_lock);
+
+	if (!timestamp_origin.tv_sec) {
+		usbi_backend->clock_gettime(USBI_CLOCK_REALTIME, &timestamp_origin);
+	}
+
+	if (!context && usbi_default_context) {
+		usbi_dbg("reusing default context");
+		default_context_refcnt++;
+		usbi_mutex_static_unlock(&default_context_lock);
+		return 0;
+	}
+
+	ctx = calloc(1, sizeof(*ctx));
+	if (!ctx) {
+		r = LIBUSB_ERROR_NO_MEM;
+		goto err_unlock;
+	}
+
+#ifdef ENABLE_DEBUG_LOGGING
+	ctx->debug = LIBUSB_LOG_LEVEL_DEBUG;
+#endif
+
+	if (dbg) {
+		ctx->debug = atoi(dbg);
+		if (ctx->debug)
+			ctx->debug_fixed = 1;
+	}
+
+	/* default context should be initialized before calling usbi_dbg */
+	if (!usbi_default_context) {
+		usbi_default_context = ctx;
+		default_context_refcnt++;
+		usbi_dbg("created default context");
+	}
+
+	usbi_dbg("libusb v%u.%u.%u.%u%s", libusb_version_internal.major, libusb_version_internal.minor,
+		libusb_version_internal.micro, libusb_version_internal.nano, libusb_version_internal.rc);
+
+	usbi_mutex_init(&ctx->usb_devs_lock);
+	usbi_mutex_init(&ctx->open_devs_lock);
+	usbi_mutex_init(&ctx->hotplug_cbs_lock);
+	list_init(&ctx->usb_devs);
+	list_init(&ctx->open_devs);
+	list_init(&ctx->hotplug_cbs);
+
+	usbi_mutex_static_lock(&active_contexts_lock);
+	if (first_init) {
+		first_init = 0;
+		list_init (&active_contexts_list);
+	}
+	list_add (&ctx->list, &active_contexts_list);
+	usbi_mutex_static_unlock(&active_contexts_lock);
+
+	if (usbi_backend->init) {
+		r = usbi_backend->init(ctx);
+		if (r)
+			goto err_free_ctx;
+	}
+
+	r = usbi_io_init(ctx);
+	if (r < 0)
+		goto err_backend_exit;
+
+	usbi_mutex_static_unlock(&default_context_lock);
+
+	if (context)
+		*context = ctx;
+
+	return 0;
+
+err_backend_exit:
+	if (usbi_backend->exit)
+		usbi_backend->exit();
+err_free_ctx:
+	if (ctx == usbi_default_context) {
+		usbi_default_context = NULL;
+		default_context_refcnt--;
+	}
+
+	usbi_mutex_static_lock(&active_contexts_lock);
+	list_del (&ctx->list);
+	usbi_mutex_static_unlock(&active_contexts_lock);
+
+	usbi_mutex_lock(&ctx->usb_devs_lock);
+	list_for_each_entry_safe(dev, next, &ctx->usb_devs, list, struct libusb_device) {
+		list_del(&dev->list);
+		libusb_unref_device(dev);
+	}
+	usbi_mutex_unlock(&ctx->usb_devs_lock);
+
+	usbi_mutex_destroy(&ctx->open_devs_lock);
+	usbi_mutex_destroy(&ctx->usb_devs_lock);
+	usbi_mutex_destroy(&ctx->hotplug_cbs_lock);
+
+	free(ctx);
+err_unlock:
+	usbi_mutex_static_unlock(&default_context_lock);
+	return r;
+}
+
+/** \ingroup libusb_lib
+ * Deinitialize libusb. Should be called after closing all open devices and
+ * before your application terminates.
+ * \param ctx the context to deinitialize, or NULL for the default context
+ */
+void API_EXPORTED libusb_exit(struct libusb_context *ctx)
+{
+	struct libusb_device *dev, *next;
+	struct timeval tv = { 0, 0 };
+
+	usbi_dbg("");
+	USBI_GET_CONTEXT(ctx);
+
+	/* if working with default context, only actually do the deinitialization
+	 * if we're the last user */
+	usbi_mutex_static_lock(&default_context_lock);
+	if (ctx == usbi_default_context) {
+		if (--default_context_refcnt > 0) {
+			usbi_dbg("not destroying default context");
+			usbi_mutex_static_unlock(&default_context_lock);
+			return;
+		}
+		usbi_dbg("destroying default context");
+		usbi_default_context = NULL;
+	}
+	usbi_mutex_static_unlock(&default_context_lock);
+
+	usbi_mutex_static_lock(&active_contexts_lock);
+	list_del (&ctx->list);
+	usbi_mutex_static_unlock(&active_contexts_lock);
+
+	if (libusb_has_capability(LIBUSB_CAP_HAS_HOTPLUG)) {
+		usbi_hotplug_deregister_all(ctx);
+
+		/*
+		 * Ensure any pending unplug events are read from the hotplug
+		 * pipe. The usb_device-s hold in the events are no longer part
+		 * of usb_devs, but the events still hold a reference!
+		 *
+		 * Note we don't do this if the application has left devices
+		 * open (which implies a buggy app) to avoid packet completion
+		 * handlers running when the app does not expect them to run.
+		 */
+		if (list_empty(&ctx->open_devs))
+			libusb_handle_events_timeout(ctx, &tv);
+
+		usbi_mutex_lock(&ctx->usb_devs_lock);
+		list_for_each_entry_safe(dev, next, &ctx->usb_devs, list, struct libusb_device) {
+			list_del(&dev->list);
+			libusb_unref_device(dev);
+		}
+		usbi_mutex_unlock(&ctx->usb_devs_lock);
+	}
+
+	/* a few sanity checks. don't bother with locking because unless
+	 * there is an application bug, nobody will be accessing these. */
+	if (!list_empty(&ctx->usb_devs))
+		usbi_warn(ctx, "some libusb_devices were leaked");
+	if (!list_empty(&ctx->open_devs))
+		usbi_warn(ctx, "application left some devices open");
+
+	usbi_io_exit(ctx);
+	if (usbi_backend->exit)
+		usbi_backend->exit();
+
+	usbi_mutex_destroy(&ctx->open_devs_lock);
+	usbi_mutex_destroy(&ctx->usb_devs_lock);
+	usbi_mutex_destroy(&ctx->hotplug_cbs_lock);
+	free(ctx);
+}
+
+/** \ingroup libusb_misc
+ * Check at runtime if the loaded library has a given capability.
+ * This call should be performed after \ref libusb_init(), to ensure the
+ * backend has updated its capability set.
+ *
+ * \param capability the \ref libusb_capability to check for
+ * \returns nonzero if the running library has the capability, 0 otherwise
+ */
+int API_EXPORTED libusb_has_capability(uint32_t capability)
+{
+	switch (capability) {
+	case LIBUSB_CAP_HAS_CAPABILITY:
+		return 1;
+	case LIBUSB_CAP_HAS_HOTPLUG:
+		return !(usbi_backend->get_device_list);
+	case LIBUSB_CAP_HAS_HID_ACCESS:
+		return (usbi_backend->caps & USBI_CAP_HAS_HID_ACCESS);
+	case LIBUSB_CAP_SUPPORTS_DETACH_KERNEL_DRIVER:
+		return (usbi_backend->caps & USBI_CAP_SUPPORTS_DETACH_KERNEL_DRIVER);
+	}
+	return 0;
+}
+
+/* this is defined in libusbi.h if needed */
+#ifdef LIBUSB_PRINTF_WIN32
+/*
+ * Prior to VS2015, Microsoft did not provide the snprintf() function and
+ * provided a vsnprintf() that did not guarantee NULL-terminated output.
+ * Microsoft did provide a _snprintf() function, but again it did not
+ * guarantee NULL-terminated output.
+ *
+ * The below implementations guarantee NULL-terminated output and are
+ * C99 compliant.
+ */
+
+int usbi_snprintf(char *str, size_t size, const char *format, ...)
+{
+	va_list ap;
+	int ret;
+
+	va_start(ap, format);
+	ret = usbi_vsnprintf(str, size, format, ap);
+	va_end(ap);
+
+	return ret;
+}
+
+int usbi_vsnprintf(char *str, size_t size, const char *format, va_list ap)
+{
+	int ret;
+
+	ret = _vsnprintf(str, size, format, ap);
+	if (ret < 0 || ret == (int)size) {
+		/* Output is truncated, ensure buffer is NULL-terminated and
+		 * determine how many characters would have been written. */
+		str[size - 1] = '\0';
+		if (ret < 0)
+			ret = _vsnprintf(NULL, 0, format, ap);
+	}
+
+	return ret;
+}
+#endif
+
+static void usbi_log_str(struct libusb_context *ctx,
+	enum libusb_log_level level, const char * str)
+{
+#if defined(USE_SYSTEM_LOGGING_FACILITY)
+#if defined(OS_WINDOWS)
+	OutputDebugString(str);
+#elif defined(OS_WINCE)
+	/* Windows CE only supports the Unicode version of OutputDebugString. */
+	WCHAR wbuf[USBI_MAX_LOG_LEN];
+	MultiByteToWideChar(CP_UTF8, 0, str, -1, wbuf, sizeof(wbuf));
+	OutputDebugStringW(wbuf);
+#elif defined(__ANDROID__)
+	int priority = ANDROID_LOG_UNKNOWN;
+	switch (level) {
+	case LIBUSB_LOG_LEVEL_INFO: priority = ANDROID_LOG_INFO; break;
+	case LIBUSB_LOG_LEVEL_WARNING: priority = ANDROID_LOG_WARN; break;
+	case LIBUSB_LOG_LEVEL_ERROR: priority = ANDROID_LOG_ERROR; break;
+	case LIBUSB_LOG_LEVEL_DEBUG: priority = ANDROID_LOG_DEBUG; break;
+	}
+	__android_log_write(priority, "libusb", str);
+#elif defined(HAVE_SYSLOG_FUNC)
+	int syslog_level = LOG_INFO;
+	switch (level) {
+	case LIBUSB_LOG_LEVEL_INFO: syslog_level = LOG_INFO; break;
+	case LIBUSB_LOG_LEVEL_WARNING: syslog_level = LOG_WARNING; break;
+	case LIBUSB_LOG_LEVEL_ERROR: syslog_level = LOG_ERR; break;
+	case LIBUSB_LOG_LEVEL_DEBUG: syslog_level = LOG_DEBUG; break;
+	}
+	syslog(syslog_level, "%s", str);
+#else /* All of gcc, Clang, XCode seem to use #warning */
+#warning System logging is not supported on this platform. Logging to stderr will be used instead.
+	fputs(str, stderr);
+#endif
+#else
+	fputs(str, stderr);
+#endif /* USE_SYSTEM_LOGGING_FACILITY */
+	UNUSED(ctx);
+	UNUSED(level);
+}
+
+void usbi_log_v(struct libusb_context *ctx, enum libusb_log_level level,
+	const char *function, const char *format, va_list args)
+{
+	const char *prefix = "";
+	char buf[USBI_MAX_LOG_LEN];
+	struct timespec now;
+	int global_debug, header_len, text_len;
+	static int has_debug_header_been_displayed = 0;
+
+#ifdef ENABLE_DEBUG_LOGGING
+	global_debug = 1;
+	UNUSED(ctx);
+#else
+	int ctx_level = 0;
+
+	USBI_GET_CONTEXT(ctx);
+	if (ctx) {
+		ctx_level = ctx->debug;
+	} else {
+		char *dbg = getenv("LIBUSB_DEBUG");
+		if (dbg)
+			ctx_level = atoi(dbg);
+	}
+	global_debug = (ctx_level == LIBUSB_LOG_LEVEL_DEBUG);
+	if (!ctx_level)
+		return;
+	if (level == LIBUSB_LOG_LEVEL_WARNING && ctx_level < LIBUSB_LOG_LEVEL_WARNING)
+		return;
+	if (level == LIBUSB_LOG_LEVEL_INFO && ctx_level < LIBUSB_LOG_LEVEL_INFO)
+		return;
+	if (level == LIBUSB_LOG_LEVEL_DEBUG && ctx_level < LIBUSB_LOG_LEVEL_DEBUG)
+		return;
+#endif
+
+	usbi_backend->clock_gettime(USBI_CLOCK_REALTIME, &now);
+	if ((global_debug) && (!has_debug_header_been_displayed)) {
+		has_debug_header_been_displayed = 1;
+		usbi_log_str(ctx, LIBUSB_LOG_LEVEL_DEBUG, "[timestamp] [threadID] facility level [function call] <message>" USBI_LOG_LINE_END);
+		usbi_log_str(ctx, LIBUSB_LOG_LEVEL_DEBUG, "--------------------------------------------------------------------------------" USBI_LOG_LINE_END);
+	}
+	if (now.tv_nsec < timestamp_origin.tv_nsec) {
+		now.tv_sec--;
+		now.tv_nsec += 1000000000L;
+	}
+	now.tv_sec -= timestamp_origin.tv_sec;
+	now.tv_nsec -= timestamp_origin.tv_nsec;
+
+	switch (level) {
+	case LIBUSB_LOG_LEVEL_INFO:
+		prefix = "info";
+		break;
+	case LIBUSB_LOG_LEVEL_WARNING:
+		prefix = "warning";
+		break;
+	case LIBUSB_LOG_LEVEL_ERROR:
+		prefix = "error";
+		break;
+	case LIBUSB_LOG_LEVEL_DEBUG:
+		prefix = "debug";
+		break;
+	case LIBUSB_LOG_LEVEL_NONE:
+		return;
+	default:
+		prefix = "unknown";
+		break;
+	}
+
+	if (global_debug) {
+		header_len = snprintf(buf, sizeof(buf),
+			"[%2d.%06d] [%08x] libusb: %s [%s] ",
+			(int)now.tv_sec, (int)(now.tv_nsec / 1000L), usbi_get_tid(), prefix, function);
+	} else {
+		header_len = snprintf(buf, sizeof(buf),
+			"libusb: %s [%s] ", prefix, function);
+	}
+
+	if (header_len < 0 || header_len >= (int)sizeof(buf)) {
+		/* Somehow snprintf failed to write to the buffer,
+		 * remove the header so something useful is output. */
+		header_len = 0;
+	}
+	/* Make sure buffer is NUL terminated */
+	buf[header_len] = '\0';
+	text_len = vsnprintf(buf + header_len, sizeof(buf) - header_len,
+		format, args);
+	if (text_len < 0 || text_len + header_len >= (int)sizeof(buf)) {
+		/* Truncated log output. On some platforms a -1 return value means
+		 * that the output was truncated. */
+		text_len = sizeof(buf) - header_len;
+	}
+	if (header_len + text_len + sizeof(USBI_LOG_LINE_END) >= sizeof(buf)) {
+		/* Need to truncate the text slightly to fit on the terminator. */
+		text_len -= (header_len + text_len + sizeof(USBI_LOG_LINE_END)) - sizeof(buf);
+	}
+	strcpy(buf + header_len + text_len, USBI_LOG_LINE_END);
+
+	usbi_log_str(ctx, level, buf);
+}
+
+void usbi_log(struct libusb_context *ctx, enum libusb_log_level level,
+	const char *function, const char *format, ...)
+{
+	va_list args;
+
+	va_start (args, format);
+	usbi_log_v(ctx, level, function, format, args);
+	va_end (args);
+}
+
+/** \ingroup libusb_misc
+ * Returns a constant NULL-terminated string with the ASCII name of a libusb
+ * error or transfer status code. The caller must not free() the returned
+ * string.
+ *
+ * \param error_code The \ref libusb_error or libusb_transfer_status code to
+ * return the name of.
+ * \returns The error name, or the string **UNKNOWN** if the value of
+ * error_code is not a known error / status code.
+ */
+DEFAULT_VISIBILITY const char * LIBUSB_CALL libusb_error_name(int error_code)
+{
+	switch (error_code) {
+	case LIBUSB_ERROR_IO:
+		return "LIBUSB_ERROR_IO";
+	case LIBUSB_ERROR_INVALID_PARAM:
+		return "LIBUSB_ERROR_INVALID_PARAM";
+	case LIBUSB_ERROR_ACCESS:
+		return "LIBUSB_ERROR_ACCESS";
+	case LIBUSB_ERROR_NO_DEVICE:
+		return "LIBUSB_ERROR_NO_DEVICE";
+	case LIBUSB_ERROR_NOT_FOUND:
+		return "LIBUSB_ERROR_NOT_FOUND";
+	case LIBUSB_ERROR_BUSY:
+		return "LIBUSB_ERROR_BUSY";
+	case LIBUSB_ERROR_TIMEOUT:
+		return "LIBUSB_ERROR_TIMEOUT";
+	case LIBUSB_ERROR_OVERFLOW:
+		return "LIBUSB_ERROR_OVERFLOW";
+	case LIBUSB_ERROR_PIPE:
+		return "LIBUSB_ERROR_PIPE";
+	case LIBUSB_ERROR_INTERRUPTED:
+		return "LIBUSB_ERROR_INTERRUPTED";
+	case LIBUSB_ERROR_NO_MEM:
+		return "LIBUSB_ERROR_NO_MEM";
+	case LIBUSB_ERROR_NOT_SUPPORTED:
+		return "LIBUSB_ERROR_NOT_SUPPORTED";
+	case LIBUSB_ERROR_OTHER:
+		return "LIBUSB_ERROR_OTHER";
+
+	case LIBUSB_TRANSFER_ERROR:
+		return "LIBUSB_TRANSFER_ERROR";
+	case LIBUSB_TRANSFER_TIMED_OUT:
+		return "LIBUSB_TRANSFER_TIMED_OUT";
+	case LIBUSB_TRANSFER_CANCELLED:
+		return "LIBUSB_TRANSFER_CANCELLED";
+	case LIBUSB_TRANSFER_STALL:
+		return "LIBUSB_TRANSFER_STALL";
+	case LIBUSB_TRANSFER_NO_DEVICE:
+		return "LIBUSB_TRANSFER_NO_DEVICE";
+	case LIBUSB_TRANSFER_OVERFLOW:
+		return "LIBUSB_TRANSFER_OVERFLOW";
+
+	case 0:
+		return "LIBUSB_SUCCESS / LIBUSB_TRANSFER_COMPLETED";
+	default:
+		return "**UNKNOWN**";
+	}
+}
+
+/** \ingroup libusb_misc
+ * Returns a pointer to const struct libusb_version with the version
+ * (major, minor, micro, nano and rc) of the running library.
+ */
+DEFAULT_VISIBILITY
+const struct libusb_version * LIBUSB_CALL libusb_get_version(void)
+{
+	return &libusb_version_internal;
+}
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/descriptor.c b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/descriptor.c
new file mode 100644
index 000000000..4c9435fff
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/descriptor.c
@@ -0,0 +1,1191 @@
+/* -*- Mode: C; indent-tabs-mode:t ; c-basic-offset:8 -*- */
+/*
+ * USB descriptor handling functions for libusb
+ * Copyright © 2007 Daniel Drake <dsd@gentoo.org>
+ * Copyright © 2001 Johannes Erdfelt <johannes@erdfelt.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <config.h>
+
+#include <errno.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "libusbi.h"
+
+#define DESC_HEADER_LENGTH		2
+#define DEVICE_DESC_LENGTH		18
+#define CONFIG_DESC_LENGTH		9
+#define INTERFACE_DESC_LENGTH		9
+#define ENDPOINT_DESC_LENGTH		7
+#define ENDPOINT_AUDIO_DESC_LENGTH	9
+
+/** @defgroup libusb_desc USB descriptors
+ * This page details how to examine the various standard USB descriptors
+ * for detected devices
+ */
+
+/* set host_endian if the w values are already in host endian format,
+ * as opposed to bus endian. */
+int usbi_parse_descriptor(const unsigned char *source, const char *descriptor,
+	void *dest, int host_endian)
+{
+	const unsigned char *sp = source;
+	unsigned char *dp = dest;
+	uint16_t w;
+	const char *cp;
+	uint32_t d;
+
+	for (cp = descriptor; *cp; cp++) {
+		switch (*cp) {
+			case 'b':	/* 8-bit byte */
+				*dp++ = *sp++;
+				break;
+			case 'w':	/* 16-bit word, convert from little endian to CPU */
+				dp += ((uintptr_t)dp & 1);	/* Align to word boundary */
+
+				if (host_endian) {
+					memcpy(dp, sp, 2);
+				} else {
+					w = (sp[1] << 8) | sp[0];
+					*((uint16_t *)dp) = w;
+				}
+				sp += 2;
+				dp += 2;
+				break;
+			case 'd':	/* 32-bit word, convert from little endian to CPU */
+				dp += ((uintptr_t)dp & 1);	/* Align to word boundary */
+
+				if (host_endian) {
+					memcpy(dp, sp, 4);
+				} else {
+					d = (sp[3] << 24) | (sp[2] << 16) |
+						(sp[1] << 8) | sp[0];
+					*((uint32_t *)dp) = d;
+				}
+				sp += 4;
+				dp += 4;
+				break;
+			case 'u':	/* 16 byte UUID */
+				memcpy(dp, sp, 16);
+				sp += 16;
+				dp += 16;
+				break;
+		}
+	}
+
+	return (int) (sp - source);
+}
+
+static void clear_endpoint(struct libusb_endpoint_descriptor *endpoint)
+{
+	free((void *) endpoint->extra);
+}
+
+static int parse_endpoint(struct libusb_context *ctx,
+	struct libusb_endpoint_descriptor *endpoint, unsigned char *buffer,
+	int size, int host_endian)
+{
+	struct usb_descriptor_header header;
+	unsigned char *extra;
+	unsigned char *begin;
+	int parsed = 0;
+	int len;
+
+	if (size < DESC_HEADER_LENGTH) {
+		usbi_err(ctx, "short endpoint descriptor read %d/%d",
+			 size, DESC_HEADER_LENGTH);
+		return LIBUSB_ERROR_IO;
+	}
+
+	usbi_parse_descriptor(buffer, "bb", &header, 0);
+	if (header.bDescriptorType != LIBUSB_DT_ENDPOINT) {
+		usbi_err(ctx, "unexpected descriptor %x (expected %x)",
+			header.bDescriptorType, LIBUSB_DT_ENDPOINT);
+		return parsed;
+	}
+	if (header.bLength > size) {
+		usbi_warn(ctx, "short endpoint descriptor read %d/%d",
+			  size, header.bLength);
+		return parsed;
+	}
+	if (header.bLength >= ENDPOINT_AUDIO_DESC_LENGTH)
+		usbi_parse_descriptor(buffer, "bbbbwbbb", endpoint, host_endian);
+	else if (header.bLength >= ENDPOINT_DESC_LENGTH)
+		usbi_parse_descriptor(buffer, "bbbbwb", endpoint, host_endian);
+	else {
+		usbi_err(ctx, "invalid endpoint bLength (%d)", header.bLength);
+		return LIBUSB_ERROR_IO;
+	}
+
+	buffer += header.bLength;
+	size -= header.bLength;
+	parsed += header.bLength;
+
+	/* Skip over the rest of the Class Specific or Vendor Specific */
+	/*  descriptors */
+	begin = buffer;
+	while (size >= DESC_HEADER_LENGTH) {
+		usbi_parse_descriptor(buffer, "bb", &header, 0);
+		if (header.bLength < DESC_HEADER_LENGTH) {
+			usbi_err(ctx, "invalid extra ep desc len (%d)",
+				 header.bLength);
+			return LIBUSB_ERROR_IO;
+		} else if (header.bLength > size) {
+			usbi_warn(ctx, "short extra ep desc read %d/%d",
+				  size, header.bLength);
+			return parsed;
+		}
+
+		/* If we find another "proper" descriptor then we're done  */
+		if ((header.bDescriptorType == LIBUSB_DT_ENDPOINT) ||
+				(header.bDescriptorType == LIBUSB_DT_INTERFACE) ||
+				(header.bDescriptorType == LIBUSB_DT_CONFIG) ||
+				(header.bDescriptorType == LIBUSB_DT_DEVICE))
+			break;
+
+		usbi_dbg("skipping descriptor %x", header.bDescriptorType);
+		buffer += header.bLength;
+		size -= header.bLength;
+		parsed += header.bLength;
+	}
+
+	/* Copy any unknown descriptors into a storage area for drivers */
+	/*  to later parse */
+	len = (int)(buffer - begin);
+	if (!len) {
+		endpoint->extra = NULL;
+		endpoint->extra_length = 0;
+		return parsed;
+	}
+
+	extra = malloc(len);
+	endpoint->extra = extra;
+	if (!extra) {
+		endpoint->extra_length = 0;
+		return LIBUSB_ERROR_NO_MEM;
+	}
+
+	memcpy(extra, begin, len);
+	endpoint->extra_length = len;
+
+	return parsed;
+}
+
+static void clear_interface(struct libusb_interface *usb_interface)
+{
+	int i;
+	int j;
+
+	if (usb_interface->altsetting) {
+		for (i = 0; i < usb_interface->num_altsetting; i++) {
+			struct libusb_interface_descriptor *ifp =
+				(struct libusb_interface_descriptor *)
+				usb_interface->altsetting + i;
+			free((void *) ifp->extra);
+			if (ifp->endpoint) {
+				for (j = 0; j < ifp->bNumEndpoints; j++)
+					clear_endpoint((struct libusb_endpoint_descriptor *)
+						       ifp->endpoint + j);
+			}
+			free((void *) ifp->endpoint);
+		}
+	}
+	free((void *) usb_interface->altsetting);
+	usb_interface->altsetting = NULL;
+}
+
+static int parse_interface(libusb_context *ctx,
+	struct libusb_interface *usb_interface, unsigned char *buffer, int size,
+	int host_endian)
+{
+	int i;
+	int len;
+	int r;
+	int parsed = 0;
+	int interface_number = -1;
+	struct usb_descriptor_header header;
+	struct libusb_interface_descriptor *ifp;
+	unsigned char *begin;
+
+	usb_interface->num_altsetting = 0;
+
+	while (size >= INTERFACE_DESC_LENGTH) {
+		struct libusb_interface_descriptor *altsetting =
+			(struct libusb_interface_descriptor *) usb_interface->altsetting;
+		altsetting = usbi_reallocf(altsetting,
+			sizeof(struct libusb_interface_descriptor) *
+			(usb_interface->num_altsetting + 1));
+		if (!altsetting) {
+			r = LIBUSB_ERROR_NO_MEM;
+			goto err;
+		}
+		usb_interface->altsetting = altsetting;
+
+		ifp = altsetting + usb_interface->num_altsetting;
+		usbi_parse_descriptor(buffer, "bbbbbbbbb", ifp, 0);
+		if (ifp->bDescriptorType != LIBUSB_DT_INTERFACE) {
+			usbi_err(ctx, "unexpected descriptor %x (expected %x)",
+				 ifp->bDescriptorType, LIBUSB_DT_INTERFACE);
+			return parsed;
+		}
+		if (ifp->bLength < INTERFACE_DESC_LENGTH) {
+			usbi_err(ctx, "invalid interface bLength (%d)",
+				 ifp->bLength);
+			r = LIBUSB_ERROR_IO;
+			goto err;
+		}
+		if (ifp->bLength > size) {
+			usbi_warn(ctx, "short intf descriptor read %d/%d",
+				 size, ifp->bLength);
+			return parsed;
+		}
+		if (ifp->bNumEndpoints > USB_MAXENDPOINTS) {
+			usbi_err(ctx, "too many endpoints (%d)", ifp->bNumEndpoints);
+			r = LIBUSB_ERROR_IO;
+			goto err;
+		}
+
+		usb_interface->num_altsetting++;
+		ifp->extra = NULL;
+		ifp->extra_length = 0;
+		ifp->endpoint = NULL;
+
+		if (interface_number == -1)
+			interface_number = ifp->bInterfaceNumber;
+
+		/* Skip over the interface */
+		buffer += ifp->bLength;
+		parsed += ifp->bLength;
+		size -= ifp->bLength;
+
+		begin = buffer;
+
+		/* Skip over any interface, class or vendor descriptors */
+		while (size >= DESC_HEADER_LENGTH) {
+			usbi_parse_descriptor(buffer, "bb", &header, 0);
+			if (header.bLength < DESC_HEADER_LENGTH) {
+				usbi_err(ctx,
+					 "invalid extra intf desc len (%d)",
+					 header.bLength);
+				r = LIBUSB_ERROR_IO;
+				goto err;
+			} else if (header.bLength > size) {
+				usbi_warn(ctx,
+					  "short extra intf desc read %d/%d",
+					  size, header.bLength);
+				return parsed;
+			}
+
+			/* If we find another "proper" descriptor then we're done */
+			if ((header.bDescriptorType == LIBUSB_DT_INTERFACE) ||
+					(header.bDescriptorType == LIBUSB_DT_ENDPOINT) ||
+					(header.bDescriptorType == LIBUSB_DT_CONFIG) ||
+					(header.bDescriptorType == LIBUSB_DT_DEVICE))
+				break;
+
+			buffer += header.bLength;
+			parsed += header.bLength;
+			size -= header.bLength;
+		}
+
+		/* Copy any unknown descriptors into a storage area for */
+		/*  drivers to later parse */
+		len = (int)(buffer - begin);
+		if (len) {
+			ifp->extra = malloc(len);
+			if (!ifp->extra) {
+				r = LIBUSB_ERROR_NO_MEM;
+				goto err;
+			}
+			memcpy((unsigned char *) ifp->extra, begin, len);
+			ifp->extra_length = len;
+		}
+
+		if (ifp->bNumEndpoints > 0) {
+			struct libusb_endpoint_descriptor *endpoint;
+			endpoint = calloc(ifp->bNumEndpoints, sizeof(struct libusb_endpoint_descriptor));
+			ifp->endpoint = endpoint;
+			if (!endpoint) {
+				r = LIBUSB_ERROR_NO_MEM;
+				goto err;
+			}
+
+			for (i = 0; i < ifp->bNumEndpoints; i++) {
+				r = parse_endpoint(ctx, endpoint + i, buffer, size,
+					host_endian);
+				if (r < 0)
+					goto err;
+				if (r == 0) {
+					ifp->bNumEndpoints = (uint8_t)i;
+					break;;
+				}
+
+				buffer += r;
+				parsed += r;
+				size -= r;
+			}
+		}
+
+		/* We check to see if it's an alternate to this one */
+		ifp = (struct libusb_interface_descriptor *) buffer;
+		if (size < LIBUSB_DT_INTERFACE_SIZE ||
+				ifp->bDescriptorType != LIBUSB_DT_INTERFACE ||
+				ifp->bInterfaceNumber != interface_number)
+			return parsed;
+	}
+
+	return parsed;
+err:
+	clear_interface(usb_interface);
+	return r;
+}
+
+static void clear_configuration(struct libusb_config_descriptor *config)
+{
+	int i;
+	if (config->interface) {
+		for (i = 0; i < config->bNumInterfaces; i++)
+			clear_interface((struct libusb_interface *)
+					config->interface + i);
+	}
+	free((void *) config->interface);
+	free((void *) config->extra);
+}
+
+static int parse_configuration(struct libusb_context *ctx,
+	struct libusb_config_descriptor *config, unsigned char *buffer,
+	int size, int host_endian)
+{
+	int i;
+	int r;
+	struct usb_descriptor_header header;
+	struct libusb_interface *usb_interface;
+
+	if (size < LIBUSB_DT_CONFIG_SIZE) {
+		usbi_err(ctx, "short config descriptor read %d/%d",
+			 size, LIBUSB_DT_CONFIG_SIZE);
+		return LIBUSB_ERROR_IO;
+	}
+
+	usbi_parse_descriptor(buffer, "bbwbbbbb", config, host_endian);
+	if (config->bDescriptorType != LIBUSB_DT_CONFIG) {
+		usbi_err(ctx, "unexpected descriptor %x (expected %x)",
+			 config->bDescriptorType, LIBUSB_DT_CONFIG);
+		return LIBUSB_ERROR_IO;
+	}
+	if (config->bLength < LIBUSB_DT_CONFIG_SIZE) {
+		usbi_err(ctx, "invalid config bLength (%d)", config->bLength);
+		return LIBUSB_ERROR_IO;
+	}
+	if (config->bLength > size) {
+		usbi_err(ctx, "short config descriptor read %d/%d",
+			 size, config->bLength);
+		return LIBUSB_ERROR_IO;
+	}
+	if (config->bNumInterfaces > USB_MAXINTERFACES) {
+		usbi_err(ctx, "too many interfaces (%d)", config->bNumInterfaces);
+		return LIBUSB_ERROR_IO;
+	}
+
+	usb_interface = calloc(config->bNumInterfaces, sizeof(struct libusb_interface));
+	config->interface = usb_interface;
+	if (!usb_interface)
+		return LIBUSB_ERROR_NO_MEM;
+
+	buffer += config->bLength;
+	size -= config->bLength;
+
+	config->extra = NULL;
+	config->extra_length = 0;
+
+	for (i = 0; i < config->bNumInterfaces; i++) {
+		int len;
+		unsigned char *begin;
+
+		/* Skip over the rest of the Class Specific or Vendor */
+		/*  Specific descriptors */
+		begin = buffer;
+		while (size >= DESC_HEADER_LENGTH) {
+			usbi_parse_descriptor(buffer, "bb", &header, 0);
+
+			if (header.bLength < DESC_HEADER_LENGTH) {
+				usbi_err(ctx,
+					 "invalid extra config desc len (%d)",
+					 header.bLength);
+				r = LIBUSB_ERROR_IO;
+				goto err;
+			} else if (header.bLength > size) {
+				usbi_warn(ctx,
+					  "short extra config desc read %d/%d",
+					  size, header.bLength);
+				config->bNumInterfaces = (uint8_t)i;
+				return size;
+			}
+
+			/* If we find another "proper" descriptor then we're done */
+			if ((header.bDescriptorType == LIBUSB_DT_ENDPOINT) ||
+					(header.bDescriptorType == LIBUSB_DT_INTERFACE) ||
+					(header.bDescriptorType == LIBUSB_DT_CONFIG) ||
+					(header.bDescriptorType == LIBUSB_DT_DEVICE))
+				break;
+
+			usbi_dbg("skipping descriptor 0x%x", header.bDescriptorType);
+			buffer += header.bLength;
+			size -= header.bLength;
+		}
+
+		/* Copy any unknown descriptors into a storage area for */
+		/*  drivers to later parse */
+		len = (int)(buffer - begin);
+		if (len) {
+			/* FIXME: We should realloc and append here */
+			if (!config->extra_length) {
+				config->extra = malloc(len);
+				if (!config->extra) {
+					r = LIBUSB_ERROR_NO_MEM;
+					goto err;
+				}
+
+				memcpy((unsigned char *) config->extra, begin, len);
+				config->extra_length = len;
+			}
+		}
+
+		r = parse_interface(ctx, usb_interface + i, buffer, size, host_endian);
+		if (r < 0)
+			goto err;
+		if (r == 0) {
+			config->bNumInterfaces = (uint8_t)i;
+			break;
+		}
+
+		buffer += r;
+		size -= r;
+	}
+
+	return size;
+
+err:
+	clear_configuration(config);
+	return r;
+}
+
+static int raw_desc_to_config(struct libusb_context *ctx,
+	unsigned char *buf, int size, int host_endian,
+	struct libusb_config_descriptor **config)
+{
+	struct libusb_config_descriptor *_config = malloc(sizeof(*_config));
+	int r;
+	
+	if (!_config)
+		return LIBUSB_ERROR_NO_MEM;
+
+	r = parse_configuration(ctx, _config, buf, size, host_endian);
+	if (r < 0) {
+		usbi_err(ctx, "parse_configuration failed with error %d", r);
+		free(_config);
+		return r;
+	} else if (r > 0) {
+		usbi_warn(ctx, "still %d bytes of descriptor data left", r);
+	}
+	
+	*config = _config;
+	return LIBUSB_SUCCESS;
+}
+
+int usbi_device_cache_descriptor(libusb_device *dev)
+{
+	int r, host_endian = 0;
+
+	r = usbi_backend->get_device_descriptor(dev, (unsigned char *) &dev->device_descriptor,
+						&host_endian);
+	if (r < 0)
+		return r;
+
+	if (!host_endian) {
+		dev->device_descriptor.bcdUSB = libusb_le16_to_cpu(dev->device_descriptor.bcdUSB);
+		dev->device_descriptor.idVendor = libusb_le16_to_cpu(dev->device_descriptor.idVendor);
+		dev->device_descriptor.idProduct = libusb_le16_to_cpu(dev->device_descriptor.idProduct);
+		dev->device_descriptor.bcdDevice = libusb_le16_to_cpu(dev->device_descriptor.bcdDevice);
+	}
+
+	return LIBUSB_SUCCESS;
+}
+
+/** \ingroup libusb_desc
+ * Get the USB device descriptor for a given device.
+ *
+ * This is a non-blocking function; the device descriptor is cached in memory.
+ *
+ * Note since libusb-1.0.16, \ref LIBUSB_API_VERSION >= 0x01000102, this
+ * function always succeeds.
+ *
+ * \param dev the device
+ * \param desc output location for the descriptor data
+ * \returns 0 on success or a LIBUSB_ERROR code on failure
+ */
+int API_EXPORTED libusb_get_device_descriptor(libusb_device *dev,
+	struct libusb_device_descriptor *desc)
+{
+	usbi_dbg("");
+	memcpy((unsigned char *) desc, (unsigned char *) &dev->device_descriptor,
+	       sizeof (dev->device_descriptor));
+	return 0;
+}
+
+/** \ingroup libusb_desc
+ * Get the USB configuration descriptor for the currently active configuration.
+ * This is a non-blocking function which does not involve any requests being
+ * sent to the device.
+ *
+ * \param dev a device
+ * \param config output location for the USB configuration descriptor. Only
+ * valid if 0 was returned. Must be freed with libusb_free_config_descriptor()
+ * after use.
+ * \returns 0 on success
+ * \returns LIBUSB_ERROR_NOT_FOUND if the device is in unconfigured state
+ * \returns another LIBUSB_ERROR code on error
+ * \see libusb_get_config_descriptor
+ */
+int API_EXPORTED libusb_get_active_config_descriptor(libusb_device *dev,
+	struct libusb_config_descriptor **config)
+{
+	struct libusb_config_descriptor _config;
+	unsigned char tmp[LIBUSB_DT_CONFIG_SIZE];
+	unsigned char *buf = NULL;
+	int host_endian = 0;
+	int r;
+
+	r = usbi_backend->get_active_config_descriptor(dev, tmp,
+		LIBUSB_DT_CONFIG_SIZE, &host_endian);
+	if (r < 0)
+		return r;
+	if (r < LIBUSB_DT_CONFIG_SIZE) {
+		usbi_err(dev->ctx, "short config descriptor read %d/%d",
+			 r, LIBUSB_DT_CONFIG_SIZE);
+		return LIBUSB_ERROR_IO;
+	}
+
+	usbi_parse_descriptor(tmp, "bbw", &_config, host_endian);
+	buf = malloc(_config.wTotalLength);
+	if (!buf)
+		return LIBUSB_ERROR_NO_MEM;
+
+	r = usbi_backend->get_active_config_descriptor(dev, buf,
+		_config.wTotalLength, &host_endian);
+	if (r >= 0)
+		r = raw_desc_to_config(dev->ctx, buf, r, host_endian, config);
+
+	free(buf);
+	return r;
+}
+
+/** \ingroup libusb_desc
+ * Get a USB configuration descriptor based on its index.
+ * This is a non-blocking function which does not involve any requests being
+ * sent to the device.
+ *
+ * \param dev a device
+ * \param config_index the index of the configuration you wish to retrieve
+ * \param config output location for the USB configuration descriptor. Only
+ * valid if 0 was returned. Must be freed with libusb_free_config_descriptor()
+ * after use.
+ * \returns 0 on success
+ * \returns LIBUSB_ERROR_NOT_FOUND if the configuration does not exist
+ * \returns another LIBUSB_ERROR code on error
+ * \see libusb_get_active_config_descriptor()
+ * \see libusb_get_config_descriptor_by_value()
+ */
+int API_EXPORTED libusb_get_config_descriptor(libusb_device *dev,
+	uint8_t config_index, struct libusb_config_descriptor **config)
+{
+	struct libusb_config_descriptor _config;
+	unsigned char tmp[LIBUSB_DT_CONFIG_SIZE];
+	unsigned char *buf = NULL;
+	int host_endian = 0;
+	int r;
+
+	usbi_dbg("index %d", config_index);
+	if (config_index >= dev->num_configurations)
+		return LIBUSB_ERROR_NOT_FOUND;
+
+	r = usbi_backend->get_config_descriptor(dev, config_index, tmp,
+		LIBUSB_DT_CONFIG_SIZE, &host_endian);
+	if (r < 0)
+		return r;
+	if (r < LIBUSB_DT_CONFIG_SIZE) {
+		usbi_err(dev->ctx, "short config descriptor read %d/%d",
+			 r, LIBUSB_DT_CONFIG_SIZE);
+		return LIBUSB_ERROR_IO;
+	}
+
+	usbi_parse_descriptor(tmp, "bbw", &_config, host_endian);
+	buf = malloc(_config.wTotalLength);
+	if (!buf)
+		return LIBUSB_ERROR_NO_MEM;
+
+	r = usbi_backend->get_config_descriptor(dev, config_index, buf,
+		_config.wTotalLength, &host_endian);
+	if (r >= 0)
+		r = raw_desc_to_config(dev->ctx, buf, r, host_endian, config);
+
+	free(buf);
+	return r;
+}
+
+/* iterate through all configurations, returning the index of the configuration
+ * matching a specific bConfigurationValue in the idx output parameter, or -1
+ * if the config was not found.
+ * returns 0 on success or a LIBUSB_ERROR code
+ */
+int usbi_get_config_index_by_value(struct libusb_device *dev,
+	uint8_t bConfigurationValue, int *idx)
+{
+	uint8_t i;
+
+	usbi_dbg("value %d", bConfigurationValue);
+	for (i = 0; i < dev->num_configurations; i++) {
+		unsigned char tmp[6];
+		int host_endian;
+		int r = usbi_backend->get_config_descriptor(dev, i, tmp, sizeof(tmp),
+			&host_endian);
+		if (r < 0) {
+			*idx = -1;
+			return r;
+		}
+		if (tmp[5] == bConfigurationValue) {
+			*idx = i;
+			return 0;
+		}
+	}
+
+	*idx = -1;
+	return 0;
+}
+
+/** \ingroup libusb_desc
+ * Get a USB configuration descriptor with a specific bConfigurationValue.
+ * This is a non-blocking function which does not involve any requests being
+ * sent to the device.
+ *
+ * \param dev a device
+ * \param bConfigurationValue the bConfigurationValue of the configuration you
+ * wish to retrieve
+ * \param config output location for the USB configuration descriptor. Only
+ * valid if 0 was returned. Must be freed with libusb_free_config_descriptor()
+ * after use.
+ * \returns 0 on success
+ * \returns LIBUSB_ERROR_NOT_FOUND if the configuration does not exist
+ * \returns another LIBUSB_ERROR code on error
+ * \see libusb_get_active_config_descriptor()
+ * \see libusb_get_config_descriptor()
+ */
+int API_EXPORTED libusb_get_config_descriptor_by_value(libusb_device *dev,
+	uint8_t bConfigurationValue, struct libusb_config_descriptor **config)
+{
+	int r, idx, host_endian;
+	unsigned char *buf = NULL;
+
+	if (usbi_backend->get_config_descriptor_by_value) {
+		r = usbi_backend->get_config_descriptor_by_value(dev,
+			bConfigurationValue, &buf, &host_endian);
+		if (r < 0)
+			return r;
+		return raw_desc_to_config(dev->ctx, buf, r, host_endian, config);
+	}
+
+	r = usbi_get_config_index_by_value(dev, bConfigurationValue, &idx);
+	if (r < 0)
+		return r;
+	else if (idx == -1)
+		return LIBUSB_ERROR_NOT_FOUND;
+	else
+		return libusb_get_config_descriptor(dev, (uint8_t) idx, config);
+}
+
+/** \ingroup libusb_desc
+ * Free a configuration descriptor obtained from
+ * libusb_get_active_config_descriptor() or libusb_get_config_descriptor().
+ * It is safe to call this function with a NULL config parameter, in which
+ * case the function simply returns.
+ *
+ * \param config the configuration descriptor to free
+ */
+void API_EXPORTED libusb_free_config_descriptor(
+	struct libusb_config_descriptor *config)
+{
+	if (!config)
+		return;
+
+	clear_configuration(config);
+	free(config);
+}
+
+/** \ingroup libusb_desc
+ * Get an endpoints superspeed endpoint companion descriptor (if any)
+ *
+ * \param ctx the context to operate on, or NULL for the default context
+ * \param endpoint endpoint descriptor from which to get the superspeed
+ * endpoint companion descriptor
+ * \param ep_comp output location for the superspeed endpoint companion
+ * descriptor. Only valid if 0 was returned. Must be freed with
+ * libusb_free_ss_endpoint_companion_descriptor() after use.
+ * \returns 0 on success
+ * \returns LIBUSB_ERROR_NOT_FOUND if the configuration does not exist
+ * \returns another LIBUSB_ERROR code on error
+ */
+int API_EXPORTED libusb_get_ss_endpoint_companion_descriptor(
+	struct libusb_context *ctx,
+	const struct libusb_endpoint_descriptor *endpoint,
+	struct libusb_ss_endpoint_companion_descriptor **ep_comp)
+{
+	struct usb_descriptor_header header;
+	int size = endpoint->extra_length;
+	const unsigned char *buffer = endpoint->extra;
+
+	*ep_comp = NULL;
+
+	while (size >= DESC_HEADER_LENGTH) {
+		usbi_parse_descriptor(buffer, "bb", &header, 0);
+		if (header.bLength < 2 || header.bLength > size) {
+			usbi_err(ctx, "invalid descriptor length %d",
+				 header.bLength);
+			return LIBUSB_ERROR_IO;
+		}
+		if (header.bDescriptorType != LIBUSB_DT_SS_ENDPOINT_COMPANION) {
+			buffer += header.bLength;
+			size -= header.bLength;
+			continue;
+		}
+		if (header.bLength < LIBUSB_DT_SS_ENDPOINT_COMPANION_SIZE) {
+			usbi_err(ctx, "invalid ss-ep-comp-desc length %d",
+				 header.bLength);
+			return LIBUSB_ERROR_IO;
+		}
+		*ep_comp = malloc(sizeof(**ep_comp));
+		if (*ep_comp == NULL)
+			return LIBUSB_ERROR_NO_MEM;
+		usbi_parse_descriptor(buffer, "bbbbw", *ep_comp, 0);
+		return LIBUSB_SUCCESS;
+	}
+	return LIBUSB_ERROR_NOT_FOUND;
+}
+
+/** \ingroup libusb_desc
+ * Free a superspeed endpoint companion descriptor obtained from
+ * libusb_get_ss_endpoint_companion_descriptor().
+ * It is safe to call this function with a NULL ep_comp parameter, in which
+ * case the function simply returns.
+ *
+ * \param ep_comp the superspeed endpoint companion descriptor to free
+ */
+void API_EXPORTED libusb_free_ss_endpoint_companion_descriptor(
+	struct libusb_ss_endpoint_companion_descriptor *ep_comp)
+{
+	free(ep_comp);
+}
+
+static int parse_bos(struct libusb_context *ctx,
+	struct libusb_bos_descriptor **bos,
+	unsigned char *buffer, int size, int host_endian)
+{
+	struct libusb_bos_descriptor bos_header, *_bos;
+	struct libusb_bos_dev_capability_descriptor dev_cap;
+	int i;
+
+	if (size < LIBUSB_DT_BOS_SIZE) {
+		usbi_err(ctx, "short bos descriptor read %d/%d",
+			 size, LIBUSB_DT_BOS_SIZE);
+		return LIBUSB_ERROR_IO;
+	}
+
+	usbi_parse_descriptor(buffer, "bbwb", &bos_header, host_endian);
+	if (bos_header.bDescriptorType != LIBUSB_DT_BOS) {
+		usbi_err(ctx, "unexpected descriptor %x (expected %x)",
+			 bos_header.bDescriptorType, LIBUSB_DT_BOS);
+		return LIBUSB_ERROR_IO;
+	}
+	if (bos_header.bLength < LIBUSB_DT_BOS_SIZE) {
+		usbi_err(ctx, "invalid bos bLength (%d)", bos_header.bLength);
+		return LIBUSB_ERROR_IO;
+	}
+	if (bos_header.bLength > size) {
+		usbi_err(ctx, "short bos descriptor read %d/%d",
+			 size, bos_header.bLength);
+		return LIBUSB_ERROR_IO;
+	}
+
+	_bos = calloc (1,
+		sizeof(*_bos) + bos_header.bNumDeviceCaps * sizeof(void *));
+	if (!_bos)
+		return LIBUSB_ERROR_NO_MEM;
+
+	usbi_parse_descriptor(buffer, "bbwb", _bos, host_endian);
+	buffer += bos_header.bLength;
+	size -= bos_header.bLength;
+
+	/* Get the device capability descriptors */
+	for (i = 0; i < bos_header.bNumDeviceCaps; i++) {
+		if (size < LIBUSB_DT_DEVICE_CAPABILITY_SIZE) {
+			usbi_warn(ctx, "short dev-cap descriptor read %d/%d",
+				  size, LIBUSB_DT_DEVICE_CAPABILITY_SIZE);
+			break;
+		}
+		usbi_parse_descriptor(buffer, "bbb", &dev_cap, host_endian);
+		if (dev_cap.bDescriptorType != LIBUSB_DT_DEVICE_CAPABILITY) {
+			usbi_warn(ctx, "unexpected descriptor %x (expected %x)",
+				  dev_cap.bDescriptorType, LIBUSB_DT_DEVICE_CAPABILITY);
+			break;
+		}
+		if (dev_cap.bLength < LIBUSB_DT_DEVICE_CAPABILITY_SIZE) {
+			usbi_err(ctx, "invalid dev-cap bLength (%d)",
+				 dev_cap.bLength);
+			libusb_free_bos_descriptor(_bos);
+			return LIBUSB_ERROR_IO;
+		}
+		if (dev_cap.bLength > size) {
+			usbi_warn(ctx, "short dev-cap descriptor read %d/%d",
+				  size, dev_cap.bLength);
+			break;
+		}
+
+		_bos->dev_capability[i] = malloc(dev_cap.bLength);
+		if (!_bos->dev_capability[i]) {
+			libusb_free_bos_descriptor(_bos);
+			return LIBUSB_ERROR_NO_MEM;
+		}
+		memcpy(_bos->dev_capability[i], buffer, dev_cap.bLength);
+		buffer += dev_cap.bLength;
+		size -= dev_cap.bLength;
+	}
+	_bos->bNumDeviceCaps = (uint8_t)i;
+	*bos = _bos;
+
+	return LIBUSB_SUCCESS;
+}
+
+/** \ingroup libusb_desc
+ * Get a Binary Object Store (BOS) descriptor
+ * This is a BLOCKING function, which will send requests to the device.
+ *
+ * \param dev_handle the handle of an open libusb device
+ * \param bos output location for the BOS descriptor. Only valid if 0 was returned.
+ * Must be freed with \ref libusb_free_bos_descriptor() after use.
+ * \returns 0 on success
+ * \returns LIBUSB_ERROR_NOT_FOUND if the device doesn't have a BOS descriptor
+ * \returns another LIBUSB_ERROR code on error
+ */
+int API_EXPORTED libusb_get_bos_descriptor(libusb_device_handle *dev_handle,
+	struct libusb_bos_descriptor **bos)
+{
+	struct libusb_bos_descriptor _bos;
+	uint8_t bos_header[LIBUSB_DT_BOS_SIZE] = {0};
+	unsigned char *bos_data = NULL;
+	const int host_endian = 0;
+	int r;
+
+	/* Read the BOS. This generates 2 requests on the bus,
+	 * one for the header, and one for the full BOS */
+	r = libusb_get_descriptor(dev_handle, LIBUSB_DT_BOS, 0, bos_header,
+				  LIBUSB_DT_BOS_SIZE);
+	if (r < 0) {
+		if (r != LIBUSB_ERROR_PIPE)
+			usbi_err(HANDLE_CTX(dev_handle), "failed to read BOS (%d)", r);
+		return r;
+	}
+	if (r < LIBUSB_DT_BOS_SIZE) {
+		usbi_err(HANDLE_CTX(dev_handle), "short BOS read %d/%d",
+			 r, LIBUSB_DT_BOS_SIZE);
+		return LIBUSB_ERROR_IO;
+	}
+
+	usbi_parse_descriptor(bos_header, "bbwb", &_bos, host_endian);
+	usbi_dbg("found BOS descriptor: size %d bytes, %d capabilities",
+		 _bos.wTotalLength, _bos.bNumDeviceCaps);
+	bos_data = calloc(_bos.wTotalLength, 1);
+	if (bos_data == NULL)
+		return LIBUSB_ERROR_NO_MEM;
+
+	r = libusb_get_descriptor(dev_handle, LIBUSB_DT_BOS, 0, bos_data,
+				  _bos.wTotalLength);
+	if (r >= 0)
+		r = parse_bos(HANDLE_CTX(dev_handle), bos, bos_data, r, host_endian);
+	else
+		usbi_err(HANDLE_CTX(dev_handle), "failed to read BOS (%d)", r);
+
+	free(bos_data);
+	return r;
+}
+
+/** \ingroup libusb_desc
+ * Free a BOS descriptor obtained from libusb_get_bos_descriptor().
+ * It is safe to call this function with a NULL bos parameter, in which
+ * case the function simply returns.
+ *
+ * \param bos the BOS descriptor to free
+ */
+void API_EXPORTED libusb_free_bos_descriptor(struct libusb_bos_descriptor *bos)
+{
+	int i;
+
+	if (!bos)
+		return;
+
+	for (i = 0; i < bos->bNumDeviceCaps; i++)
+		free(bos->dev_capability[i]);
+	free(bos);
+}
+
+/** \ingroup libusb_desc
+ * Get an USB 2.0 Extension descriptor
+ *
+ * \param ctx the context to operate on, or NULL for the default context
+ * \param dev_cap Device Capability descriptor with a bDevCapabilityType of
+ * \ref libusb_capability_type::LIBUSB_BT_USB_2_0_EXTENSION
+ * LIBUSB_BT_USB_2_0_EXTENSION
+ * \param usb_2_0_extension output location for the USB 2.0 Extension
+ * descriptor. Only valid if 0 was returned. Must be freed with
+ * libusb_free_usb_2_0_extension_descriptor() after use.
+ * \returns 0 on success
+ * \returns a LIBUSB_ERROR code on error
+ */
+int API_EXPORTED libusb_get_usb_2_0_extension_descriptor(
+	struct libusb_context *ctx,
+	struct libusb_bos_dev_capability_descriptor *dev_cap,
+	struct libusb_usb_2_0_extension_descriptor **usb_2_0_extension)
+{
+	struct libusb_usb_2_0_extension_descriptor *_usb_2_0_extension;
+	const int host_endian = 0;
+
+	if (dev_cap->bDevCapabilityType != LIBUSB_BT_USB_2_0_EXTENSION) {
+		usbi_err(ctx, "unexpected bDevCapabilityType %x (expected %x)",
+			 dev_cap->bDevCapabilityType,
+			 LIBUSB_BT_USB_2_0_EXTENSION);
+		return LIBUSB_ERROR_INVALID_PARAM;
+	}
+	if (dev_cap->bLength < LIBUSB_BT_USB_2_0_EXTENSION_SIZE) {
+		usbi_err(ctx, "short dev-cap descriptor read %d/%d",
+			 dev_cap->bLength, LIBUSB_BT_USB_2_0_EXTENSION_SIZE);
+		return LIBUSB_ERROR_IO;
+	}
+
+	_usb_2_0_extension = malloc(sizeof(*_usb_2_0_extension));
+	if (!_usb_2_0_extension)
+		return LIBUSB_ERROR_NO_MEM;
+
+	usbi_parse_descriptor((unsigned char *)dev_cap, "bbbd",
+			      _usb_2_0_extension, host_endian);
+
+	*usb_2_0_extension = _usb_2_0_extension;
+	return LIBUSB_SUCCESS;
+}
+
+/** \ingroup libusb_desc
+ * Free a USB 2.0 Extension descriptor obtained from
+ * libusb_get_usb_2_0_extension_descriptor().
+ * It is safe to call this function with a NULL usb_2_0_extension parameter,
+ * in which case the function simply returns.
+ *
+ * \param usb_2_0_extension the USB 2.0 Extension descriptor to free
+ */
+void API_EXPORTED libusb_free_usb_2_0_extension_descriptor(
+	struct libusb_usb_2_0_extension_descriptor *usb_2_0_extension)
+{
+	free(usb_2_0_extension);
+}
+
+/** \ingroup libusb_desc
+ * Get a SuperSpeed USB Device Capability descriptor
+ *
+ * \param ctx the context to operate on, or NULL for the default context
+ * \param dev_cap Device Capability descriptor with a bDevCapabilityType of
+ * \ref libusb_capability_type::LIBUSB_BT_SS_USB_DEVICE_CAPABILITY
+ * LIBUSB_BT_SS_USB_DEVICE_CAPABILITY
+ * \param ss_usb_device_cap output location for the SuperSpeed USB Device
+ * Capability descriptor. Only valid if 0 was returned. Must be freed with
+ * libusb_free_ss_usb_device_capability_descriptor() after use.
+ * \returns 0 on success
+ * \returns a LIBUSB_ERROR code on error
+ */
+int API_EXPORTED libusb_get_ss_usb_device_capability_descriptor(
+	struct libusb_context *ctx,
+	struct libusb_bos_dev_capability_descriptor *dev_cap,
+	struct libusb_ss_usb_device_capability_descriptor **ss_usb_device_cap)
+{
+	struct libusb_ss_usb_device_capability_descriptor *_ss_usb_device_cap;
+	const int host_endian = 0;
+
+	if (dev_cap->bDevCapabilityType != LIBUSB_BT_SS_USB_DEVICE_CAPABILITY) {
+		usbi_err(ctx, "unexpected bDevCapabilityType %x (expected %x)",
+			 dev_cap->bDevCapabilityType,
+			 LIBUSB_BT_SS_USB_DEVICE_CAPABILITY);
+		return LIBUSB_ERROR_INVALID_PARAM;
+	}
+	if (dev_cap->bLength < LIBUSB_BT_SS_USB_DEVICE_CAPABILITY_SIZE) {
+		usbi_err(ctx, "short dev-cap descriptor read %d/%d",
+			 dev_cap->bLength, LIBUSB_BT_SS_USB_DEVICE_CAPABILITY_SIZE);
+		return LIBUSB_ERROR_IO;
+	}
+
+	_ss_usb_device_cap = malloc(sizeof(*_ss_usb_device_cap));
+	if (!_ss_usb_device_cap)
+		return LIBUSB_ERROR_NO_MEM;
+
+	usbi_parse_descriptor((unsigned char *)dev_cap, "bbbbwbbw",
+			      _ss_usb_device_cap, host_endian);
+
+	*ss_usb_device_cap = _ss_usb_device_cap;
+	return LIBUSB_SUCCESS;
+}
+
+/** \ingroup libusb_desc
+ * Free a SuperSpeed USB Device Capability descriptor obtained from
+ * libusb_get_ss_usb_device_capability_descriptor().
+ * It is safe to call this function with a NULL ss_usb_device_cap
+ * parameter, in which case the function simply returns.
+ *
+ * \param ss_usb_device_cap the USB 2.0 Extension descriptor to free
+ */
+void API_EXPORTED libusb_free_ss_usb_device_capability_descriptor(
+	struct libusb_ss_usb_device_capability_descriptor *ss_usb_device_cap)
+{
+	free(ss_usb_device_cap);
+}
+
+/** \ingroup libusb_desc
+ * Get a Container ID descriptor
+ *
+ * \param ctx the context to operate on, or NULL for the default context
+ * \param dev_cap Device Capability descriptor with a bDevCapabilityType of
+ * \ref libusb_capability_type::LIBUSB_BT_CONTAINER_ID
+ * LIBUSB_BT_CONTAINER_ID
+ * \param container_id output location for the Container ID descriptor.
+ * Only valid if 0 was returned. Must be freed with
+ * libusb_free_container_id_descriptor() after use.
+ * \returns 0 on success
+ * \returns a LIBUSB_ERROR code on error
+ */
+int API_EXPORTED libusb_get_container_id_descriptor(struct libusb_context *ctx,
+	struct libusb_bos_dev_capability_descriptor *dev_cap,
+	struct libusb_container_id_descriptor **container_id)
+{
+	struct libusb_container_id_descriptor *_container_id;
+	const int host_endian = 0;
+
+	if (dev_cap->bDevCapabilityType != LIBUSB_BT_CONTAINER_ID) {
+		usbi_err(ctx, "unexpected bDevCapabilityType %x (expected %x)",
+			 dev_cap->bDevCapabilityType,
+			 LIBUSB_BT_CONTAINER_ID);
+		return LIBUSB_ERROR_INVALID_PARAM;
+	}
+	if (dev_cap->bLength < LIBUSB_BT_CONTAINER_ID_SIZE) {
+		usbi_err(ctx, "short dev-cap descriptor read %d/%d",
+			 dev_cap->bLength, LIBUSB_BT_CONTAINER_ID_SIZE);
+		return LIBUSB_ERROR_IO;
+	}
+
+	_container_id = malloc(sizeof(*_container_id));
+	if (!_container_id)
+		return LIBUSB_ERROR_NO_MEM;
+
+	usbi_parse_descriptor((unsigned char *)dev_cap, "bbbbu",
+			      _container_id, host_endian);
+
+	*container_id = _container_id;
+	return LIBUSB_SUCCESS;
+}
+
+/** \ingroup libusb_desc
+ * Free a Container ID descriptor obtained from
+ * libusb_get_container_id_descriptor().
+ * It is safe to call this function with a NULL container_id parameter,
+ * in which case the function simply returns.
+ *
+ * \param container_id the USB 2.0 Extension descriptor to free
+ */
+void API_EXPORTED libusb_free_container_id_descriptor(
+	struct libusb_container_id_descriptor *container_id)
+{
+	free(container_id);
+}
+
+/** \ingroup libusb_desc
+ * Retrieve a string descriptor in C style ASCII.
+ *
+ * Wrapper around libusb_get_string_descriptor(). Uses the first language
+ * supported by the device.
+ *
+ * \param dev_handle a device handle
+ * \param desc_index the index of the descriptor to retrieve
+ * \param data output buffer for ASCII string descriptor
+ * \param length size of data buffer
+ * \returns number of bytes returned in data, or LIBUSB_ERROR code on failure
+ */
+int API_EXPORTED libusb_get_string_descriptor_ascii(libusb_device_handle *dev_handle,
+	uint8_t desc_index, unsigned char *data, int length)
+{
+	unsigned char tbuf[255]; /* Some devices choke on size > 255 */
+	int r, si, di;
+	uint16_t langid;
+
+	/* Asking for the zero'th index is special - it returns a string
+	 * descriptor that contains all the language IDs supported by the
+	 * device. Typically there aren't many - often only one. Language
+	 * IDs are 16 bit numbers, and they start at the third byte in the
+	 * descriptor. There's also no point in trying to read descriptor 0
+	 * with this function. See USB 2.0 specification section 9.6.7 for
+	 * more information.
+	 */
+
+	if (desc_index == 0)
+		return LIBUSB_ERROR_INVALID_PARAM;
+
+	r = libusb_get_string_descriptor(dev_handle, 0, 0, tbuf, sizeof(tbuf));
+	if (r < 0)
+		return r;
+
+	if (r < 4)
+		return LIBUSB_ERROR_IO;
+
+	langid = tbuf[2] | (tbuf[3] << 8);
+
+	r = libusb_get_string_descriptor(dev_handle, desc_index, langid, tbuf,
+		sizeof(tbuf));
+	if (r < 0)
+		return r;
+
+	if (tbuf[1] != LIBUSB_DT_STRING)
+		return LIBUSB_ERROR_IO;
+
+	if (tbuf[0] > r)
+		return LIBUSB_ERROR_IO;
+
+	for (di = 0, si = 2; si < tbuf[0]; si += 2) {
+		if (di >= (length - 1))
+			break;
+
+		if ((tbuf[si] & 0x80) || (tbuf[si + 1])) /* non-ASCII */
+			data[di++] = '?';
+		else
+			data[di++] = tbuf[si];
+	}
+
+	data[di] = 0;
+	return di;
+}
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/hotplug.c b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/hotplug.c
new file mode 100644
index 000000000..bbfd6e79a
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/hotplug.c
@@ -0,0 +1,350 @@
+/* -*- Mode: C; indent-tabs-mode:t ; c-basic-offset:8 -*- */
+/*
+ * Hotplug functions for libusb
+ * Copyright © 2012-2013 Nathan Hjelm <hjelmn@mac.com>
+ * Copyright © 2012-2013 Peter Stuge <peter@stuge.se>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <config.h>
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#ifdef HAVE_SYS_TYPES_H
+#include <sys/types.h>
+#endif
+#include <assert.h>
+
+#include "libusbi.h"
+#include "hotplug.h"
+
+/**
+ * @defgroup libusb_hotplug Device hotplug event notification
+ * This page details how to use the libusb hotplug interface, where available.
+ *
+ * Be mindful that not all platforms currently implement hotplug notification and
+ * that you should first call on \ref libusb_has_capability() with parameter
+ * \ref LIBUSB_CAP_HAS_HOTPLUG to confirm that hotplug support is available.
+ *
+ * \page libusb_hotplug Device hotplug event notification
+ *
+ * \section hotplug_intro Introduction
+ *
+ * Version 1.0.16, \ref LIBUSB_API_VERSION >= 0x01000102, has added support
+ * for hotplug events on <b>some</b> platforms (you should test if your platform
+ * supports hotplug notification by calling \ref libusb_has_capability() with
+ * parameter \ref LIBUSB_CAP_HAS_HOTPLUG). 
+ *
+ * This interface allows you to request notification for the arrival and departure
+ * of matching USB devices.
+ *
+ * To receive hotplug notification you register a callback by calling
+ * \ref libusb_hotplug_register_callback(). This function will optionally return
+ * a callback handle that can be passed to \ref libusb_hotplug_deregister_callback().
+ *
+ * A callback function must return an int (0 or 1) indicating whether the callback is
+ * expecting additional events. Returning 0 will rearm the callback and 1 will cause
+ * the callback to be deregistered. Note that when callbacks are called from
+ * libusb_hotplug_register_callback() because of the \ref LIBUSB_HOTPLUG_ENUMERATE
+ * flag, the callback return value is ignored, iow you cannot cause a callback
+ * to be deregistered by returning 1 when it is called from
+ * libusb_hotplug_register_callback().
+ *
+ * Callbacks for a particular context are automatically deregistered by libusb_exit().
+ *
+ * As of 1.0.16 there are two supported hotplug events:
+ *  - LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED: A device has arrived and is ready to use
+ *  - LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT: A device has left and is no longer available
+ *
+ * A hotplug event can listen for either or both of these events.
+ *
+ * Note: If you receive notification that a device has left and you have any
+ * a libusb_device_handles for the device it is up to you to call libusb_close()
+ * on each device handle to free up any remaining resources associated with the device.
+ * Once a device has left any libusb_device_handle associated with the device
+ * are invalid and will remain so even if the device comes back.
+ *
+ * When handling a LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED event it is considered
+ * safe to call any libusb function that takes a libusb_device. It also safe to
+ * open a device and submit asynchronous transfers. However, most other functions
+ * that take a libusb_device_handle are <b>not</b> safe to call. Examples of such
+ * functions are any of the \ref libusb_syncio "synchronous API" functions or the blocking
+ * functions that retrieve various \ref libusb_desc "USB descriptors". These functions must
+ * be used outside of the context of the hotplug callback.
+ *
+ * When handling a LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT event the only safe function
+ * is libusb_get_device_descriptor().
+ *
+ * The following code provides an example of the usage of the hotplug interface:
+\code
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include <libusb.h>
+
+static int count = 0;
+
+int hotplug_callback(struct libusb_context *ctx, struct libusb_device *dev,
+                     libusb_hotplug_event event, void *user_data) {
+  static libusb_device_handle *dev_handle = NULL;
+  struct libusb_device_descriptor desc;
+  int rc;
+
+  (void)libusb_get_device_descriptor(dev, &desc);
+
+  if (LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED == event) {
+    rc = libusb_open(dev, &dev_handle);
+    if (LIBUSB_SUCCESS != rc) {
+      printf("Could not open USB device\n");
+    }
+  } else if (LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT == event) {
+    if (dev_handle) {
+      libusb_close(dev_handle);
+      dev_handle = NULL;
+    }
+  } else {
+    printf("Unhandled event %d\n", event);
+  }
+  count++;
+
+  return 0;
+}
+
+int main (void) {
+  libusb_hotplug_callback_handle callback_handle;
+  int rc;
+
+  libusb_init(NULL);
+
+  rc = libusb_hotplug_register_callback(NULL, LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED |
+                                        LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT, 0, 0x045a, 0x5005,
+                                        LIBUSB_HOTPLUG_MATCH_ANY, hotplug_callback, NULL,
+                                        &callback_handle);
+  if (LIBUSB_SUCCESS != rc) {
+    printf("Error creating a hotplug callback\n");
+    libusb_exit(NULL);
+    return EXIT_FAILURE;
+  }
+
+  while (count < 2) {
+    libusb_handle_events_completed(NULL, NULL);
+    nanosleep(&(struct timespec){0, 10000000UL}, NULL);
+  }
+
+  libusb_hotplug_deregister_callback(NULL, callback_handle);
+  libusb_exit(NULL);
+
+  return 0;
+}
+\endcode
+ */
+
+static int usbi_hotplug_match_cb (struct libusb_context *ctx,
+	struct libusb_device *dev, libusb_hotplug_event event,
+	struct libusb_hotplug_callback *hotplug_cb)
+{
+	/* Handle lazy deregistration of callback */
+	if (hotplug_cb->needs_free) {
+		/* Free callback */
+		return 1;
+	}
+
+	if (!(hotplug_cb->events & event)) {
+		return 0;
+	}
+
+	if (LIBUSB_HOTPLUG_MATCH_ANY != hotplug_cb->vendor_id &&
+	    hotplug_cb->vendor_id != dev->device_descriptor.idVendor) {
+		return 0;
+	}
+
+	if (LIBUSB_HOTPLUG_MATCH_ANY != hotplug_cb->product_id &&
+	    hotplug_cb->product_id != dev->device_descriptor.idProduct) {
+		return 0;
+	}
+
+	if (LIBUSB_HOTPLUG_MATCH_ANY != hotplug_cb->dev_class &&
+	    hotplug_cb->dev_class != dev->device_descriptor.bDeviceClass) {
+		return 0;
+	}
+
+	return hotplug_cb->cb (ctx, dev, event, hotplug_cb->user_data);
+}
+
+void usbi_hotplug_match(struct libusb_context *ctx, struct libusb_device *dev,
+	libusb_hotplug_event event)
+{
+	struct libusb_hotplug_callback *hotplug_cb, *next;
+	int ret;
+
+	usbi_mutex_lock(&ctx->hotplug_cbs_lock);
+
+	list_for_each_entry_safe(hotplug_cb, next, &ctx->hotplug_cbs, list, struct libusb_hotplug_callback) {
+		usbi_mutex_unlock(&ctx->hotplug_cbs_lock);
+		ret = usbi_hotplug_match_cb (ctx, dev, event, hotplug_cb);
+		usbi_mutex_lock(&ctx->hotplug_cbs_lock);
+
+		if (ret) {
+			list_del(&hotplug_cb->list);
+			free(hotplug_cb);
+		}
+	}
+
+	usbi_mutex_unlock(&ctx->hotplug_cbs_lock);
+
+	/* the backend is expected to call the callback for each active transfer */
+}
+
+void usbi_hotplug_notification(struct libusb_context *ctx, struct libusb_device *dev,
+	libusb_hotplug_event event)
+{
+	int pending_events;
+	libusb_hotplug_message *message = calloc(1, sizeof(*message));
+
+	if (!message) {
+		usbi_err(ctx, "error allocating hotplug message");
+		return;
+	}
+
+	message->event = event;
+	message->device = dev;
+
+	/* Take the event data lock and add this message to the list.
+	 * Only signal an event if there are no prior pending events. */
+	usbi_mutex_lock(&ctx->event_data_lock);
+	pending_events = usbi_pending_events(ctx);
+	list_add_tail(&message->list, &ctx->hotplug_msgs);
+	if (!pending_events)
+		usbi_signal_event(ctx);
+	usbi_mutex_unlock(&ctx->event_data_lock);
+}
+
+int API_EXPORTED libusb_hotplug_register_callback(libusb_context *ctx,
+	libusb_hotplug_event events, libusb_hotplug_flag flags,
+	int vendor_id, int product_id, int dev_class,
+	libusb_hotplug_callback_fn cb_fn, void *user_data,
+	libusb_hotplug_callback_handle *callback_handle)
+{
+	libusb_hotplug_callback *new_callback;
+	static int handle_id = 1;
+
+	/* check for hotplug support */
+	if (!libusb_has_capability(LIBUSB_CAP_HAS_HOTPLUG)) {
+		return LIBUSB_ERROR_NOT_SUPPORTED;
+	}
+
+	/* check for sane values */
+	if ((LIBUSB_HOTPLUG_MATCH_ANY != vendor_id && (~0xffff & vendor_id)) ||
+	    (LIBUSB_HOTPLUG_MATCH_ANY != product_id && (~0xffff & product_id)) ||
+	    (LIBUSB_HOTPLUG_MATCH_ANY != dev_class && (~0xff & dev_class)) ||
+	    !cb_fn) {
+		return LIBUSB_ERROR_INVALID_PARAM;
+	}
+
+	USBI_GET_CONTEXT(ctx);
+
+	new_callback = (libusb_hotplug_callback *)calloc(1, sizeof (*new_callback));
+	if (!new_callback) {
+		return LIBUSB_ERROR_NO_MEM;
+	}
+
+	new_callback->ctx = ctx;
+	new_callback->vendor_id = vendor_id;
+	new_callback->product_id = product_id;
+	new_callback->dev_class = dev_class;
+	new_callback->flags = flags;
+	new_callback->events = events;
+	new_callback->cb = cb_fn;
+	new_callback->user_data = user_data;
+	new_callback->needs_free = 0;
+
+	usbi_mutex_lock(&ctx->hotplug_cbs_lock);
+
+	/* protect the handle by the context hotplug lock. it doesn't matter if the same handle
+	 * is used for different contexts only that the handle is unique for this context */
+	new_callback->handle = handle_id++;
+
+	list_add(&new_callback->list, &ctx->hotplug_cbs);
+
+	usbi_mutex_unlock(&ctx->hotplug_cbs_lock);
+
+
+	if (flags & LIBUSB_HOTPLUG_ENUMERATE) {
+		int i, len;
+		struct libusb_device **devs;
+
+		len = (int) libusb_get_device_list(ctx, &devs);
+		if (len < 0) {
+			libusb_hotplug_deregister_callback(ctx,
+							new_callback->handle);
+			return len;
+		}
+
+		for (i = 0; i < len; i++) {
+			usbi_hotplug_match_cb(ctx, devs[i],
+					LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED,
+					new_callback);
+		}
+
+		libusb_free_device_list(devs, 1);
+	}
+
+
+	if (callback_handle)
+		*callback_handle = new_callback->handle;
+
+	return LIBUSB_SUCCESS;
+}
+
+void API_EXPORTED libusb_hotplug_deregister_callback (struct libusb_context *ctx,
+	libusb_hotplug_callback_handle callback_handle)
+{
+	struct libusb_hotplug_callback *hotplug_cb;
+
+	/* check for hotplug support */
+	if (!libusb_has_capability(LIBUSB_CAP_HAS_HOTPLUG)) {
+		return;
+	}
+
+	USBI_GET_CONTEXT(ctx);
+
+	usbi_mutex_lock(&ctx->hotplug_cbs_lock);
+	list_for_each_entry(hotplug_cb, &ctx->hotplug_cbs, list,
+			    struct libusb_hotplug_callback) {
+		if (callback_handle == hotplug_cb->handle) {
+			/* Mark this callback for deregistration */
+			hotplug_cb->needs_free = 1;
+		}
+	}
+	usbi_mutex_unlock(&ctx->hotplug_cbs_lock);
+
+	usbi_hotplug_notification(ctx, NULL, 0);
+}
+
+void usbi_hotplug_deregister_all(struct libusb_context *ctx) {
+	struct libusb_hotplug_callback *hotplug_cb, *next;
+
+	usbi_mutex_lock(&ctx->hotplug_cbs_lock);
+	list_for_each_entry_safe(hotplug_cb, next, &ctx->hotplug_cbs, list,
+				 struct libusb_hotplug_callback) {
+		list_del(&hotplug_cb->list);
+		free(hotplug_cb);
+	}
+
+	usbi_mutex_unlock(&ctx->hotplug_cbs_lock);
+}
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/hotplug.h b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/hotplug.h
new file mode 100644
index 000000000..2bec81b06
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/hotplug.h
@@ -0,0 +1,90 @@
+/* -*- Mode: C; indent-tabs-mode:t ; c-basic-offset:8 -*- */
+/*
+ * Hotplug support for libusb
+ * Copyright © 2012-2013 Nathan Hjelm <hjelmn@mac.com>
+ * Copyright © 2012-2013 Peter Stuge <peter@stuge.se>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#if !defined(USBI_HOTPLUG_H)
+#define USBI_HOTPLUG_H
+
+#ifndef LIBUSBI_H
+#include "libusbi.h"
+#endif
+
+/** \ingroup hotplug
+ * The hotplug callback structure. The user populates this structure with
+ * libusb_hotplug_prepare_callback() and then calls libusb_hotplug_register_callback()
+ * to receive notification of hotplug events.
+ */
+struct libusb_hotplug_callback {
+	/** Context this callback is associated with */
+	struct libusb_context *ctx;
+
+	/** Vendor ID to match or LIBUSB_HOTPLUG_MATCH_ANY */
+	int vendor_id;
+
+	/** Product ID to match or LIBUSB_HOTPLUG_MATCH_ANY */
+	int product_id;
+
+	/** Device class to match or LIBUSB_HOTPLUG_MATCH_ANY */
+	int dev_class;
+
+	/** Hotplug callback flags */
+	libusb_hotplug_flag flags;
+
+	/** Event(s) that will trigger this callback */
+	libusb_hotplug_event events;
+
+	/** Callback function to invoke for matching event/device */
+	libusb_hotplug_callback_fn cb;
+
+	/** Handle for this callback (used to match on deregister) */
+	libusb_hotplug_callback_handle handle;
+
+	/** User data that will be passed to the callback function */
+	void *user_data;
+
+	/** Callback is marked for deletion */
+	int needs_free;
+
+	/** List this callback is registered in (ctx->hotplug_cbs) */
+	struct list_head list;
+};
+
+typedef struct libusb_hotplug_callback libusb_hotplug_callback;
+
+struct libusb_hotplug_message {
+	/** The hotplug event that occurred */
+	libusb_hotplug_event event;
+
+	/** The device for which this hotplug event occurred */
+	struct libusb_device *device;
+
+	/** List this message is contained in (ctx->hotplug_msgs) */
+	struct list_head list;
+};
+
+typedef struct libusb_hotplug_message libusb_hotplug_message;
+
+void usbi_hotplug_deregister_all(struct libusb_context *ctx);
+void usbi_hotplug_match(struct libusb_context *ctx, struct libusb_device *dev,
+			libusb_hotplug_event event);
+void usbi_hotplug_notification(struct libusb_context *ctx, struct libusb_device *dev,
+			libusb_hotplug_event event);
+
+#endif
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/io.c b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/io.c
new file mode 100644
index 000000000..eb1eabf1c
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/io.c
@@ -0,0 +1,2819 @@
+/* -*- Mode: C; indent-tabs-mode:t ; c-basic-offset:8 -*- */
+/*
+ * I/O functions for libusb
+ * Copyright © 2007-2009 Daniel Drake <dsd@gentoo.org>
+ * Copyright © 2001 Johannes Erdfelt <johannes@erdfelt.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <config.h>
+
+#include <assert.h>
+#include <errno.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#ifdef HAVE_SYS_TIME_H
+#include <sys/time.h>
+#endif
+#ifdef USBI_TIMERFD_AVAILABLE
+#include <sys/timerfd.h>
+#endif
+
+#include "libusbi.h"
+#include "hotplug.h"
+
+/**
+ * \page libusb_io Synchronous and asynchronous device I/O
+ *
+ * \section io_intro Introduction
+ *
+ * If you're using libusb in your application, you're probably wanting to
+ * perform I/O with devices - you want to perform USB data transfers.
+ *
+ * libusb offers two separate interfaces for device I/O. This page aims to
+ * introduce the two in order to help you decide which one is more suitable
+ * for your application. You can also choose to use both interfaces in your
+ * application by considering each transfer on a case-by-case basis.
+ *
+ * Once you have read through the following discussion, you should consult the
+ * detailed API documentation pages for the details:
+ * - \ref libusb_syncio
+ * - \ref libusb_asyncio
+ *
+ * \section theory Transfers at a logical level
+ *
+ * At a logical level, USB transfers typically happen in two parts. For
+ * example, when reading data from a endpoint:
+ * -# A request for data is sent to the device
+ * -# Some time later, the incoming data is received by the host
+ *
+ * or when writing data to an endpoint:
+ *
+ * -# The data is sent to the device
+ * -# Some time later, the host receives acknowledgement from the device that
+ *    the data has been transferred.
+ *
+ * There may be an indefinite delay between the two steps. Consider a
+ * fictional USB input device with a button that the user can press. In order
+ * to determine when the button is pressed, you would likely submit a request
+ * to read data on a bulk or interrupt endpoint and wait for data to arrive.
+ * Data will arrive when the button is pressed by the user, which is
+ * potentially hours later.
+ *
+ * libusb offers both a synchronous and an asynchronous interface to performing
+ * USB transfers. The main difference is that the synchronous interface
+ * combines both steps indicated above into a single function call, whereas
+ * the asynchronous interface separates them.
+ *
+ * \section sync The synchronous interface
+ *
+ * The synchronous I/O interface allows you to perform a USB transfer with
+ * a single function call. When the function call returns, the transfer has
+ * completed and you can parse the results.
+ *
+ * If you have used the libusb-0.1 before, this I/O style will seem familar to
+ * you. libusb-0.1 only offered a synchronous interface.
+ *
+ * In our input device example, to read button presses you might write code
+ * in the following style:
+\code
+unsigned char data[4];
+int actual_length;
+int r = libusb_bulk_transfer(dev_handle, LIBUSB_ENDPOINT_IN, data, sizeof(data), &actual_length, 0);
+if (r == 0 && actual_length == sizeof(data)) {
+	// results of the transaction can now be found in the data buffer
+	// parse them here and report button press
+} else {
+	error();
+}
+\endcode
+ *
+ * The main advantage of this model is simplicity: you did everything with
+ * a single simple function call.
+ *
+ * However, this interface has its limitations. Your application will sleep
+ * inside libusb_bulk_transfer() until the transaction has completed. If it
+ * takes the user 3 hours to press the button, your application will be
+ * sleeping for that long. Execution will be tied up inside the library -
+ * the entire thread will be useless for that duration.
+ *
+ * Another issue is that by tieing up the thread with that single transaction
+ * there is no possibility of performing I/O with multiple endpoints and/or
+ * multiple devices simultaneously, unless you resort to creating one thread
+ * per transaction.
+ *
+ * Additionally, there is no opportunity to cancel the transfer after the
+ * request has been submitted.
+ *
+ * For details on how to use the synchronous API, see the
+ * \ref libusb_syncio "synchronous I/O API documentation" pages.
+ *
+ * \section async The asynchronous interface
+ *
+ * Asynchronous I/O is the most significant new feature in libusb-1.0.
+ * Although it is a more complex interface, it solves all the issues detailed
+ * above.
+ *
+ * Instead of providing which functions that block until the I/O has complete,
+ * libusb's asynchronous interface presents non-blocking functions which
+ * begin a transfer and then return immediately. Your application passes a
+ * callback function pointer to this non-blocking function, which libusb will
+ * call with the results of the transaction when it has completed.
+ *
+ * Transfers which have been submitted through the non-blocking functions
+ * can be cancelled with a separate function call.
+ *
+ * The non-blocking nature of this interface allows you to be simultaneously
+ * performing I/O to multiple endpoints on multiple devices, without having
+ * to use threads.
+ *
+ * This added flexibility does come with some complications though:
+ * - In the interest of being a lightweight library, libusb does not create
+ * threads and can only operate when your application is calling into it. Your
+ * application must call into libusb from it's main loop when events are ready
+ * to be handled, or you must use some other scheme to allow libusb to
+ * undertake whatever work needs to be done.
+ * - libusb also needs to be called into at certain fixed points in time in
+ * order to accurately handle transfer timeouts.
+ * - Memory handling becomes more complex. You cannot use stack memory unless
+ * the function with that stack is guaranteed not to return until the transfer
+ * callback has finished executing.
+ * - You generally lose some linearity from your code flow because submitting
+ * the transfer request is done in a separate function from where the transfer
+ * results are handled. This becomes particularly obvious when you want to
+ * submit a second transfer based on the results of an earlier transfer.
+ *
+ * Internally, libusb's synchronous interface is expressed in terms of function
+ * calls to the asynchronous interface.
+ *
+ * For details on how to use the asynchronous API, see the
+ * \ref libusb_asyncio "asynchronous I/O API" documentation pages.
+ */
+
+
+/**
+ * \page libusb_packetoverflow Packets and overflows
+ *
+ * \section packets Packet abstraction
+ *
+ * The USB specifications describe how data is transmitted in packets, with
+ * constraints on packet size defined by endpoint descriptors. The host must
+ * not send data payloads larger than the endpoint's maximum packet size.
+ *
+ * libusb and the underlying OS abstract out the packet concept, allowing you
+ * to request transfers of any size. Internally, the request will be divided
+ * up into correctly-sized packets. You do not have to be concerned with
+ * packet sizes, but there is one exception when considering overflows.
+ *
+ * \section overflow Bulk/interrupt transfer overflows
+ *
+ * When requesting data on a bulk endpoint, libusb requires you to supply a
+ * buffer and the maximum number of bytes of data that libusb can put in that
+ * buffer. However, the size of the buffer is not communicated to the device -
+ * the device is just asked to send any amount of data.
+ *
+ * There is no problem if the device sends an amount of data that is less than
+ * or equal to the buffer size. libusb reports this condition to you through
+ * the \ref libusb_transfer::actual_length "libusb_transfer.actual_length"
+ * field.
+ *
+ * Problems may occur if the device attempts to send more data than can fit in
+ * the buffer. libusb reports LIBUSB_TRANSFER_OVERFLOW for this condition but
+ * other behaviour is largely undefined: actual_length may or may not be
+ * accurate, the chunk of data that can fit in the buffer (before overflow)
+ * may or may not have been transferred.
+ *
+ * Overflows are nasty, but can be avoided. Even though you were told to
+ * ignore packets above, think about the lower level details: each transfer is
+ * split into packets (typically small, with a maximum size of 512 bytes).
+ * Overflows can only happen if the final packet in an incoming data transfer
+ * is smaller than the actual packet that the device wants to transfer.
+ * Therefore, you will never see an overflow if your transfer buffer size is a
+ * multiple of the endpoint's packet size: the final packet will either
+ * fill up completely or will be only partially filled.
+ */
+
+/**
+ * @defgroup libusb_asyncio Asynchronous device I/O
+ *
+ * This page details libusb's asynchronous (non-blocking) API for USB device
+ * I/O. This interface is very powerful but is also quite complex - you will
+ * need to read this page carefully to understand the necessary considerations
+ * and issues surrounding use of this interface. Simplistic applications
+ * may wish to consider the \ref libusb_syncio "synchronous I/O API" instead.
+ *
+ * The asynchronous interface is built around the idea of separating transfer
+ * submission and handling of transfer completion (the synchronous model
+ * combines both of these into one). There may be a long delay between
+ * submission and completion, however the asynchronous submission function
+ * is non-blocking so will return control to your application during that
+ * potentially long delay.
+ *
+ * \section asyncabstraction Transfer abstraction
+ *
+ * For the asynchronous I/O, libusb implements the concept of a generic
+ * transfer entity for all types of I/O (control, bulk, interrupt,
+ * isochronous). The generic transfer object must be treated slightly
+ * differently depending on which type of I/O you are performing with it.
+ *
+ * This is represented by the public libusb_transfer structure type.
+ *
+ * \section asynctrf Asynchronous transfers
+ *
+ * We can view asynchronous I/O as a 5 step process:
+ * -# <b>Allocation</b>: allocate a libusb_transfer
+ * -# <b>Filling</b>: populate the libusb_transfer instance with information
+ *    about the transfer you wish to perform
+ * -# <b>Submission</b>: ask libusb to submit the transfer
+ * -# <b>Completion handling</b>: examine transfer results in the
+ *    libusb_transfer structure
+ * -# <b>Deallocation</b>: clean up resources
+ *
+ *
+ * \subsection asyncalloc Allocation
+ *
+ * This step involves allocating memory for a USB transfer. This is the
+ * generic transfer object mentioned above. At this stage, the transfer
+ * is "blank" with no details about what type of I/O it will be used for.
+ *
+ * Allocation is done with the libusb_alloc_transfer() function. You must use
+ * this function rather than allocating your own transfers.
+ *
+ * \subsection asyncfill Filling
+ *
+ * This step is where you take a previously allocated transfer and fill it
+ * with information to determine the message type and direction, data buffer,
+ * callback function, etc.
+ *
+ * You can either fill the required fields yourself or you can use the
+ * helper functions: libusb_fill_control_transfer(), libusb_fill_bulk_transfer()
+ * and libusb_fill_interrupt_transfer().
+ *
+ * \subsection asyncsubmit Submission
+ *
+ * When you have allocated a transfer and filled it, you can submit it using
+ * libusb_submit_transfer(). This function returns immediately but can be
+ * regarded as firing off the I/O request in the background.
+ *
+ * \subsection asynccomplete Completion handling
+ *
+ * After a transfer has been submitted, one of four things can happen to it:
+ *
+ * - The transfer completes (i.e. some data was transferred)
+ * - The transfer has a timeout and the timeout expires before all data is
+ * transferred
+ * - The transfer fails due to an error
+ * - The transfer is cancelled
+ *
+ * Each of these will cause the user-specified transfer callback function to
+ * be invoked. It is up to the callback function to determine which of the
+ * above actually happened and to act accordingly.
+ *
+ * The user-specified callback is passed a pointer to the libusb_transfer
+ * structure which was used to setup and submit the transfer. At completion
+ * time, libusb has populated this structure with results of the transfer:
+ * success or failure reason, number of bytes of data transferred, etc. See
+ * the libusb_transfer structure documentation for more information.
+ *
+ * <b>Important Note</b>: The user-specified callback is called from an event
+ * handling context. It is therefore important that no calls are made into
+ * libusb that will attempt to perform any event handling. Examples of such
+ * functions are any listed in the \ref libusb_syncio "synchronous API" and any of
+ * the blocking functions that retrieve \ref libusb_desc "USB descriptors".
+ *
+ * \subsection Deallocation
+ *
+ * When a transfer has completed (i.e. the callback function has been invoked),
+ * you are advised to free the transfer (unless you wish to resubmit it, see
+ * below). Transfers are deallocated with libusb_free_transfer().
+ *
+ * It is undefined behaviour to free a transfer which has not completed.
+ *
+ * \section asyncresubmit Resubmission
+ *
+ * You may be wondering why allocation, filling, and submission are all
+ * separated above where they could reasonably be combined into a single
+ * operation.
+ *
+ * The reason for separation is to allow you to resubmit transfers without
+ * having to allocate new ones every time. This is especially useful for
+ * common situations dealing with interrupt endpoints - you allocate one
+ * transfer, fill and submit it, and when it returns with results you just
+ * resubmit it for the next interrupt.
+ *
+ * \section asynccancel Cancellation
+ *
+ * Another advantage of using the asynchronous interface is that you have
+ * the ability to cancel transfers which have not yet completed. This is
+ * done by calling the libusb_cancel_transfer() function.
+ *
+ * libusb_cancel_transfer() is asynchronous/non-blocking in itself. When the
+ * cancellation actually completes, the transfer's callback function will
+ * be invoked, and the callback function should check the transfer status to
+ * determine that it was cancelled.
+ *
+ * Freeing the transfer after it has been cancelled but before cancellation
+ * has completed will result in undefined behaviour.
+ *
+ * When a transfer is cancelled, some of the data may have been transferred.
+ * libusb will communicate this to you in the transfer callback. Do not assume
+ * that no data was transferred.
+ *
+ * \section bulk_overflows Overflows on device-to-host bulk/interrupt endpoints
+ *
+ * If your device does not have predictable transfer sizes (or it misbehaves),
+ * your application may submit a request for data on an IN endpoint which is
+ * smaller than the data that the device wishes to send. In some circumstances
+ * this will cause an overflow, which is a nasty condition to deal with. See
+ * the \ref libusb_packetoverflow page for discussion.
+ *
+ * \section asyncctrl Considerations for control transfers
+ *
+ * The <tt>libusb_transfer</tt> structure is generic and hence does not
+ * include specific fields for the control-specific setup packet structure.
+ *
+ * In order to perform a control transfer, you must place the 8-byte setup
+ * packet at the start of the data buffer. To simplify this, you could
+ * cast the buffer pointer to type struct libusb_control_setup, or you can
+ * use the helper function libusb_fill_control_setup().
+ *
+ * The wLength field placed in the setup packet must be the length you would
+ * expect to be sent in the setup packet: the length of the payload that
+ * follows (or the expected maximum number of bytes to receive). However,
+ * the length field of the libusb_transfer object must be the length of
+ * the data buffer - i.e. it should be wLength <em>plus</em> the size of
+ * the setup packet (LIBUSB_CONTROL_SETUP_SIZE).
+ *
+ * If you use the helper functions, this is simplified for you:
+ * -# Allocate a buffer of size LIBUSB_CONTROL_SETUP_SIZE plus the size of the
+ * data you are sending/requesting.
+ * -# Call libusb_fill_control_setup() on the data buffer, using the transfer
+ * request size as the wLength value (i.e. do not include the extra space you
+ * allocated for the control setup).
+ * -# If this is a host-to-device transfer, place the data to be transferred
+ * in the data buffer, starting at offset LIBUSB_CONTROL_SETUP_SIZE.
+ * -# Call libusb_fill_control_transfer() to associate the data buffer with
+ * the transfer (and to set the remaining details such as callback and timeout).
+ *   - Note that there is no parameter to set the length field of the transfer.
+ *     The length is automatically inferred from the wLength field of the setup
+ *     packet.
+ * -# Submit the transfer.
+ *
+ * The multi-byte control setup fields (wValue, wIndex and wLength) must
+ * be given in little-endian byte order (the endianness of the USB bus).
+ * Endianness conversion is transparently handled by
+ * libusb_fill_control_setup() which is documented to accept host-endian
+ * values.
+ *
+ * Further considerations are needed when handling transfer completion in
+ * your callback function:
+ * - As you might expect, the setup packet will still be sitting at the start
+ * of the data buffer.
+ * - If this was a device-to-host transfer, the received data will be sitting
+ * at offset LIBUSB_CONTROL_SETUP_SIZE into the buffer.
+ * - The actual_length field of the transfer structure is relative to the
+ * wLength of the setup packet, rather than the size of the data buffer. So,
+ * if your wLength was 4, your transfer's <tt>length</tt> was 12, then you
+ * should expect an <tt>actual_length</tt> of 4 to indicate that the data was
+ * transferred in entirity.
+ *
+ * To simplify parsing of setup packets and obtaining the data from the
+ * correct offset, you may wish to use the libusb_control_transfer_get_data()
+ * and libusb_control_transfer_get_setup() functions within your transfer
+ * callback.
+ *
+ * Even though control endpoints do not halt, a completed control transfer
+ * may have a LIBUSB_TRANSFER_STALL status code. This indicates the control
+ * request was not supported.
+ *
+ * \section asyncintr Considerations for interrupt transfers
+ *
+ * All interrupt transfers are performed using the polling interval presented
+ * by the bInterval value of the endpoint descriptor.
+ *
+ * \section asynciso Considerations for isochronous transfers
+ *
+ * Isochronous transfers are more complicated than transfers to
+ * non-isochronous endpoints.
+ *
+ * To perform I/O to an isochronous endpoint, allocate the transfer by calling
+ * libusb_alloc_transfer() with an appropriate number of isochronous packets.
+ *
+ * During filling, set \ref libusb_transfer::type "type" to
+ * \ref libusb_transfer_type::LIBUSB_TRANSFER_TYPE_ISOCHRONOUS
+ * "LIBUSB_TRANSFER_TYPE_ISOCHRONOUS", and set
+ * \ref libusb_transfer::num_iso_packets "num_iso_packets" to a value less than
+ * or equal to the number of packets you requested during allocation.
+ * libusb_alloc_transfer() does not set either of these fields for you, given
+ * that you might not even use the transfer on an isochronous endpoint.
+ *
+ * Next, populate the length field for the first num_iso_packets entries in
+ * the \ref libusb_transfer::iso_packet_desc "iso_packet_desc" array. Section
+ * 5.6.3 of the USB2 specifications describe how the maximum isochronous
+ * packet length is determined by the wMaxPacketSize field in the endpoint
+ * descriptor.
+ * Two functions can help you here:
+ *
+ * - libusb_get_max_iso_packet_size() is an easy way to determine the max
+ *   packet size for an isochronous endpoint. Note that the maximum packet
+ *   size is actually the maximum number of bytes that can be transmitted in
+ *   a single microframe, therefore this function multiplies the maximum number
+ *   of bytes per transaction by the number of transaction opportunities per
+ *   microframe.
+ * - libusb_set_iso_packet_lengths() assigns the same length to all packets
+ *   within a transfer, which is usually what you want.
+ *
+ * For outgoing transfers, you'll obviously fill the buffer and populate the
+ * packet descriptors in hope that all the data gets transferred. For incoming
+ * transfers, you must ensure the buffer has sufficient capacity for
+ * the situation where all packets transfer the full amount of requested data.
+ *
+ * Completion handling requires some extra consideration. The
+ * \ref libusb_transfer::actual_length "actual_length" field of the transfer
+ * is meaningless and should not be examined; instead you must refer to the
+ * \ref libusb_iso_packet_descriptor::actual_length "actual_length" field of
+ * each individual packet.
+ *
+ * The \ref libusb_transfer::status "status" field of the transfer is also a
+ * little misleading:
+ *  - If the packets were submitted and the isochronous data microframes
+ *    completed normally, status will have value
+ *    \ref libusb_transfer_status::LIBUSB_TRANSFER_COMPLETED
+ *    "LIBUSB_TRANSFER_COMPLETED". Note that bus errors and software-incurred
+ *    delays are not counted as transfer errors; the transfer.status field may
+ *    indicate COMPLETED even if some or all of the packets failed. Refer to
+ *    the \ref libusb_iso_packet_descriptor::status "status" field of each
+ *    individual packet to determine packet failures.
+ *  - The status field will have value
+ *    \ref libusb_transfer_status::LIBUSB_TRANSFER_ERROR
+ *    "LIBUSB_TRANSFER_ERROR" only when serious errors were encountered.
+ *  - Other transfer status codes occur with normal behaviour.
+ *
+ * The data for each packet will be found at an offset into the buffer that
+ * can be calculated as if each prior packet completed in full. The
+ * libusb_get_iso_packet_buffer() and libusb_get_iso_packet_buffer_simple()
+ * functions may help you here.
+ *
+ * <b>Note</b>: Some operating systems (e.g. Linux) may impose limits on the
+ * length of individual isochronous packets and/or the total length of the
+ * isochronous transfer. Such limits can be difficult for libusb to detect,
+ * so the library will simply try and submit the transfer as set up by you.
+ * If the transfer fails to submit because it is too large,
+ * libusb_submit_transfer() will return
+ * \ref libusb_error::LIBUSB_ERROR_INVALID_PARAM "LIBUSB_ERROR_INVALID_PARAM".
+ *
+ * \section asyncmem Memory caveats
+ *
+ * In most circumstances, it is not safe to use stack memory for transfer
+ * buffers. This is because the function that fired off the asynchronous
+ * transfer may return before libusb has finished using the buffer, and when
+ * the function returns it's stack gets destroyed. This is true for both
+ * host-to-device and device-to-host transfers.
+ *
+ * The only case in which it is safe to use stack memory is where you can
+ * guarantee that the function owning the stack space for the buffer does not
+ * return until after the transfer's callback function has completed. In every
+ * other case, you need to use heap memory instead.
+ *
+ * \section asyncflags Fine control
+ *
+ * Through using this asynchronous interface, you may find yourself repeating
+ * a few simple operations many times. You can apply a bitwise OR of certain
+ * flags to a transfer to simplify certain things:
+ * - \ref libusb_transfer_flags::LIBUSB_TRANSFER_SHORT_NOT_OK
+ *   "LIBUSB_TRANSFER_SHORT_NOT_OK" results in transfers which transferred
+ *   less than the requested amount of data being marked with status
+ *   \ref libusb_transfer_status::LIBUSB_TRANSFER_ERROR "LIBUSB_TRANSFER_ERROR"
+ *   (they would normally be regarded as COMPLETED)
+ * - \ref libusb_transfer_flags::LIBUSB_TRANSFER_FREE_BUFFER
+ *   "LIBUSB_TRANSFER_FREE_BUFFER" allows you to ask libusb to free the transfer
+ *   buffer when freeing the transfer.
+ * - \ref libusb_transfer_flags::LIBUSB_TRANSFER_FREE_TRANSFER
+ *   "LIBUSB_TRANSFER_FREE_TRANSFER" causes libusb to automatically free the
+ *   transfer after the transfer callback returns.
+ *
+ * \section asyncevent Event handling
+ *
+ * An asynchronous model requires that libusb perform work at various
+ * points in time - namely processing the results of previously-submitted
+ * transfers and invoking the user-supplied callback function.
+ *
+ * This gives rise to the libusb_handle_events() function which your
+ * application must call into when libusb has work do to. This gives libusb
+ * the opportunity to reap pending transfers, invoke callbacks, etc.
+ *
+ * There are 2 different approaches to dealing with libusb_handle_events:
+ *
+ * -# Repeatedly call libusb_handle_events() in blocking mode from a dedicated
+ *    thread.
+ * -# Integrate libusb with your application's main event loop. libusb
+ *    exposes a set of file descriptors which allow you to do this.
+ *
+ * The first approach has the big advantage that it will also work on Windows
+ * were libusb' poll API for select / poll integration is not available. So
+ * if you want to support Windows and use the async API, you must use this
+ * approach, see the \ref eventthread "Using an event handling thread" section
+ * below for details.
+ *
+ * If you prefer a single threaded approach with a single central event loop,
+ * see the \ref libusb_poll "polling and timing" section for how to integrate libusb
+ * into your application's main event loop.
+ *
+ * \section eventthread Using an event handling thread
+ *
+ * Lets begin with stating the obvious: If you're going to use a separate
+ * thread for libusb event handling, your callback functions MUST be
+ * threadsafe.
+ *
+ * Other then that doing event handling from a separate thread, is mostly
+ * simple. You can use an event thread function as follows:
+\code
+void *event_thread_func(void *ctx)
+{
+    while (event_thread_run)
+        libusb_handle_events(ctx);
+
+    return NULL;
+}
+\endcode
+ *
+ * There is one caveat though, stopping this thread requires setting the
+ * event_thread_run variable to 0, and after that libusb_handle_events() needs
+ * to return control to event_thread_func. But unless some event happens,
+ * libusb_handle_events() will not return.
+ *
+ * There are 2 different ways of dealing with this, depending on if your
+ * application uses libusb' \ref libusb_hotplug "hotplug" support or not.
+ *
+ * Applications which do not use hotplug support, should not start the event
+ * thread until after their first call to libusb_open(), and should stop the
+ * thread when closing the last open device as follows:
+\code
+void my_close_handle(libusb_device_handle *dev_handle)
+{
+    if (open_devs == 1)
+        event_thread_run = 0;
+
+    libusb_close(dev_handle); // This wakes up libusb_handle_events()
+
+    if (open_devs == 1)
+        pthread_join(event_thread);
+
+    open_devs--;
+}
+\endcode
+ *
+ * Applications using hotplug support should start the thread at program init,
+ * after having successfully called libusb_hotplug_register_callback(), and
+ * should stop the thread at program exit as follows:
+\code
+void my_libusb_exit(void)
+{
+    event_thread_run = 0;
+    libusb_hotplug_deregister_callback(ctx, hotplug_cb_handle); // This wakes up libusb_handle_events()
+    pthread_join(event_thread);
+    libusb_exit(ctx);
+}
+\endcode
+ */
+
+/**
+ * @defgroup libusb_poll Polling and timing
+ *
+ * This page documents libusb's functions for polling events and timing.
+ * These functions are only necessary for users of the
+ * \ref libusb_asyncio "asynchronous API". If you are only using the simpler
+ * \ref libusb_syncio "synchronous API" then you do not need to ever call these
+ * functions.
+ *
+ * The justification for the functionality described here has already been
+ * discussed in the \ref asyncevent "event handling" section of the
+ * asynchronous API documentation. In summary, libusb does not create internal
+ * threads for event processing and hence relies on your application calling
+ * into libusb at certain points in time so that pending events can be handled.
+ *
+ * Your main loop is probably already calling poll() or select() or a
+ * variant on a set of file descriptors for other event sources (e.g. keyboard
+ * button presses, mouse movements, network sockets, etc). You then add
+ * libusb's file descriptors to your poll()/select() calls, and when activity
+ * is detected on such descriptors you know it is time to call
+ * libusb_handle_events().
+ *
+ * There is one final event handling complication. libusb supports
+ * asynchronous transfers which time out after a specified time period.
+ *
+ * On some platforms a timerfd is used, so the timeout handling is just another
+ * fd, on other platforms this requires that libusb is called into at or after
+ * the timeout to handle it. So, in addition to considering libusb's file
+ * descriptors in your main event loop, you must also consider that libusb
+ * sometimes needs to be called into at fixed points in time even when there
+ * is no file descriptor activity, see \ref polltime details.
+ *
+ * In order to know precisely when libusb needs to be called into, libusb
+ * offers you a set of pollable file descriptors and information about when
+ * the next timeout expires.
+ *
+ * If you are using the asynchronous I/O API, you must take one of the two
+ * following options, otherwise your I/O will not complete.
+ *
+ * \section pollsimple The simple option
+ *
+ * If your application revolves solely around libusb and does not need to
+ * handle other event sources, you can have a program structure as follows:
+\code
+// initialize libusb
+// find and open device
+// maybe fire off some initial async I/O
+
+while (user_has_not_requested_exit)
+	libusb_handle_events(ctx);
+
+// clean up and exit
+\endcode
+ *
+ * With such a simple main loop, you do not have to worry about managing
+ * sets of file descriptors or handling timeouts. libusb_handle_events() will
+ * handle those details internally.
+ *
+ * \section libusb_pollmain The more advanced option
+ *
+ * \note This functionality is currently only available on Unix-like platforms.
+ * On Windows, libusb_get_pollfds() simply returns NULL. Applications which
+ * want to support Windows are advised to use an \ref eventthread
+ * "event handling thread" instead.
+ *
+ * In more advanced applications, you will already have a main loop which
+ * is monitoring other event sources: network sockets, X11 events, mouse
+ * movements, etc. Through exposing a set of file descriptors, libusb is
+ * designed to cleanly integrate into such main loops.
+ *
+ * In addition to polling file descriptors for the other event sources, you
+ * take a set of file descriptors from libusb and monitor those too. When you
+ * detect activity on libusb's file descriptors, you call
+ * libusb_handle_events_timeout() in non-blocking mode.
+ *
+ * What's more, libusb may also need to handle events at specific moments in
+ * time. No file descriptor activity is generated at these times, so your
+ * own application needs to be continually aware of when the next one of these
+ * moments occurs (through calling libusb_get_next_timeout()), and then it
+ * needs to call libusb_handle_events_timeout() in non-blocking mode when
+ * these moments occur. This means that you need to adjust your
+ * poll()/select() timeout accordingly.
+ *
+ * libusb provides you with a set of file descriptors to poll and expects you
+ * to poll all of them, treating them as a single entity. The meaning of each
+ * file descriptor in the set is an internal implementation detail,
+ * platform-dependent and may vary from release to release. Don't try and
+ * interpret the meaning of the file descriptors, just do as libusb indicates,
+ * polling all of them at once.
+ *
+ * In pseudo-code, you want something that looks like:
+\code
+// initialise libusb
+
+libusb_get_pollfds(ctx)
+while (user has not requested application exit) {
+	libusb_get_next_timeout(ctx);
+	poll(on libusb file descriptors plus any other event sources of interest,
+		using a timeout no larger than the value libusb just suggested)
+	if (poll() indicated activity on libusb file descriptors)
+		libusb_handle_events_timeout(ctx, &zero_tv);
+	if (time has elapsed to or beyond the libusb timeout)
+		libusb_handle_events_timeout(ctx, &zero_tv);
+	// handle events from other sources here
+}
+
+// clean up and exit
+\endcode
+ *
+ * \subsection polltime Notes on time-based events
+ *
+ * The above complication with having to track time and call into libusb at
+ * specific moments is a bit of a headache. For maximum compatibility, you do
+ * need to write your main loop as above, but you may decide that you can
+ * restrict the supported platforms of your application and get away with
+ * a more simplistic scheme.
+ *
+ * These time-based event complications are \b not required on the following
+ * platforms:
+ *  - Darwin
+ *  - Linux, provided that the following version requirements are satisfied:
+ *   - Linux v2.6.27 or newer, compiled with timerfd support
+ *   - glibc v2.9 or newer
+ *   - libusb v1.0.5 or newer
+ *
+ * Under these configurations, libusb_get_next_timeout() will \em always return
+ * 0, so your main loop can be simplified to:
+\code
+// initialise libusb
+
+libusb_get_pollfds(ctx)
+while (user has not requested application exit) {
+	poll(on libusb file descriptors plus any other event sources of interest,
+		using any timeout that you like)
+	if (poll() indicated activity on libusb file descriptors)
+		libusb_handle_events_timeout(ctx, &zero_tv);
+	// handle events from other sources here
+}
+
+// clean up and exit
+\endcode
+ *
+ * Do remember that if you simplify your main loop to the above, you will
+ * lose compatibility with some platforms (including legacy Linux platforms,
+ * and <em>any future platforms supported by libusb which may have time-based
+ * event requirements</em>). The resultant problems will likely appear as
+ * strange bugs in your application.
+ *
+ * You can use the libusb_pollfds_handle_timeouts() function to do a runtime
+ * check to see if it is safe to ignore the time-based event complications.
+ * If your application has taken the shortcut of ignoring libusb's next timeout
+ * in your main loop, then you are advised to check the return value of
+ * libusb_pollfds_handle_timeouts() during application startup, and to abort
+ * if the platform does suffer from these timing complications.
+ *
+ * \subsection fdsetchange Changes in the file descriptor set
+ *
+ * The set of file descriptors that libusb uses as event sources may change
+ * during the life of your application. Rather than having to repeatedly
+ * call libusb_get_pollfds(), you can set up notification functions for when
+ * the file descriptor set changes using libusb_set_pollfd_notifiers().
+ *
+ * \subsection mtissues Multi-threaded considerations
+ *
+ * Unfortunately, the situation is complicated further when multiple threads
+ * come into play. If two threads are monitoring the same file descriptors,
+ * the fact that only one thread will be woken up when an event occurs causes
+ * some headaches.
+ *
+ * The events lock, event waiters lock, and libusb_handle_events_locked()
+ * entities are added to solve these problems. You do not need to be concerned
+ * with these entities otherwise.
+ *
+ * See the extra documentation: \ref libusb_mtasync
+ */
+
+/** \page libusb_mtasync Multi-threaded applications and asynchronous I/O
+ *
+ * libusb is a thread-safe library, but extra considerations must be applied
+ * to applications which interact with libusb from multiple threads.
+ *
+ * The underlying issue that must be addressed is that all libusb I/O
+ * revolves around monitoring file descriptors through the poll()/select()
+ * system calls. This is directly exposed at the
+ * \ref libusb_asyncio "asynchronous interface" but it is important to note that the
+ * \ref libusb_syncio "synchronous interface" is implemented on top of the
+ * asynchonrous interface, therefore the same considerations apply.
+ *
+ * The issue is that if two or more threads are concurrently calling poll()
+ * or select() on libusb's file descriptors then only one of those threads
+ * will be woken up when an event arrives. The others will be completely
+ * oblivious that anything has happened.
+ *
+ * Consider the following pseudo-code, which submits an asynchronous transfer
+ * then waits for its completion. This style is one way you could implement a
+ * synchronous interface on top of the asynchronous interface (and libusb
+ * does something similar, albeit more advanced due to the complications
+ * explained on this page).
+ *
+\code
+void cb(struct libusb_transfer *transfer)
+{
+	int *completed = transfer->user_data;
+	*completed = 1;
+}
+
+void myfunc() {
+	struct libusb_transfer *transfer;
+	unsigned char buffer[LIBUSB_CONTROL_SETUP_SIZE] __attribute__ ((aligned (2)));
+	int completed = 0;
+
+	transfer = libusb_alloc_transfer(0);
+	libusb_fill_control_setup(buffer,
+		LIBUSB_REQUEST_TYPE_VENDOR | LIBUSB_ENDPOINT_OUT, 0x04, 0x01, 0, 0);
+	libusb_fill_control_transfer(transfer, dev, buffer, cb, &completed, 1000);
+	libusb_submit_transfer(transfer);
+
+	while (!completed) {
+		poll(libusb file descriptors, 120*1000);
+		if (poll indicates activity)
+			libusb_handle_events_timeout(ctx, &zero_tv);
+	}
+	printf("completed!");
+	// other code here
+}
+\endcode
+ *
+ * Here we are <em>serializing</em> completion of an asynchronous event
+ * against a condition - the condition being completion of a specific transfer.
+ * The poll() loop has a long timeout to minimize CPU usage during situations
+ * when nothing is happening (it could reasonably be unlimited).
+ *
+ * If this is the only thread that is polling libusb's file descriptors, there
+ * is no problem: there is no danger that another thread will swallow up the
+ * event that we are interested in. On the other hand, if there is another
+ * thread polling the same descriptors, there is a chance that it will receive
+ * the event that we were interested in. In this situation, <tt>myfunc()</tt>
+ * will only realise that the transfer has completed on the next iteration of
+ * the loop, <em>up to 120 seconds later.</em> Clearly a two-minute delay is
+ * undesirable, and don't even think about using short timeouts to circumvent
+ * this issue!
+ *
+ * The solution here is to ensure that no two threads are ever polling the
+ * file descriptors at the same time. A naive implementation of this would
+ * impact the capabilities of the library, so libusb offers the scheme
+ * documented below to ensure no loss of functionality.
+ *
+ * Before we go any further, it is worth mentioning that all libusb-wrapped
+ * event handling procedures fully adhere to the scheme documented below.
+ * This includes libusb_handle_events() and its variants, and all the
+ * synchronous I/O functions - libusb hides this headache from you.
+ *
+ * \section Using libusb_handle_events() from multiple threads
+ *
+ * Even when only using libusb_handle_events() and synchronous I/O functions,
+ * you can still have a race condition. You might be tempted to solve the
+ * above with libusb_handle_events() like so:
+ *
+\code
+	libusb_submit_transfer(transfer);
+
+	while (!completed) {
+		libusb_handle_events(ctx);
+	}
+	printf("completed!");
+\endcode
+ *
+ * This however has a race between the checking of completed and
+ * libusb_handle_events() acquiring the events lock, so another thread
+ * could have completed the transfer, resulting in this thread hanging
+ * until either a timeout or another event occurs. See also commit
+ * 6696512aade99bb15d6792af90ae329af270eba6 which fixes this in the
+ * synchronous API implementation of libusb.
+ *
+ * Fixing this race requires checking the variable completed only after
+ * taking the event lock, which defeats the concept of just calling
+ * libusb_handle_events() without worrying about locking. This is why
+ * libusb-1.0.9 introduces the new libusb_handle_events_timeout_completed()
+ * and libusb_handle_events_completed() functions, which handles doing the
+ * completion check for you after they have acquired the lock:
+ *
+\code
+	libusb_submit_transfer(transfer);
+
+	while (!completed) {
+		libusb_handle_events_completed(ctx, &completed);
+	}
+	printf("completed!");
+\endcode
+ *
+ * This nicely fixes the race in our example. Note that if all you want to
+ * do is submit a single transfer and wait for its completion, then using
+ * one of the synchronous I/O functions is much easier.
+ *
+ * \section eventlock The events lock
+ *
+ * The problem is when we consider the fact that libusb exposes file
+ * descriptors to allow for you to integrate asynchronous USB I/O into
+ * existing main loops, effectively allowing you to do some work behind
+ * libusb's back. If you do take libusb's file descriptors and pass them to
+ * poll()/select() yourself, you need to be aware of the associated issues.
+ *
+ * The first concept to be introduced is the events lock. The events lock
+ * is used to serialize threads that want to handle events, such that only
+ * one thread is handling events at any one time.
+ *
+ * You must take the events lock before polling libusb file descriptors,
+ * using libusb_lock_events(). You must release the lock as soon as you have
+ * aborted your poll()/select() loop, using libusb_unlock_events().
+ *
+ * \section threadwait Letting other threads do the work for you
+ *
+ * Although the events lock is a critical part of the solution, it is not
+ * enough on it's own. You might wonder if the following is sufficient...
+\code
+	libusb_lock_events(ctx);
+	while (!completed) {
+		poll(libusb file descriptors, 120*1000);
+		if (poll indicates activity)
+			libusb_handle_events_timeout(ctx, &zero_tv);
+	}
+	libusb_unlock_events(ctx);
+\endcode
+ * ...and the answer is that it is not. This is because the transfer in the
+ * code shown above may take a long time (say 30 seconds) to complete, and
+ * the lock is not released until the transfer is completed.
+ *
+ * Another thread with similar code that wants to do event handling may be
+ * working with a transfer that completes after a few milliseconds. Despite
+ * having such a quick completion time, the other thread cannot check that
+ * status of its transfer until the code above has finished (30 seconds later)
+ * due to contention on the lock.
+ *
+ * To solve this, libusb offers you a mechanism to determine when another
+ * thread is handling events. It also offers a mechanism to block your thread
+ * until the event handling thread has completed an event (and this mechanism
+ * does not involve polling of file descriptors).
+ *
+ * After determining that another thread is currently handling events, you
+ * obtain the <em>event waiters</em> lock using libusb_lock_event_waiters().
+ * You then re-check that some other thread is still handling events, and if
+ * so, you call libusb_wait_for_event().
+ *
+ * libusb_wait_for_event() puts your application to sleep until an event
+ * occurs, or until a thread releases the events lock. When either of these
+ * things happen, your thread is woken up, and should re-check the condition
+ * it was waiting on. It should also re-check that another thread is handling
+ * events, and if not, it should start handling events itself.
+ *
+ * This looks like the following, as pseudo-code:
+\code
+retry:
+if (libusb_try_lock_events(ctx) == 0) {
+	// we obtained the event lock: do our own event handling
+	while (!completed) {
+		if (!libusb_event_handling_ok(ctx)) {
+			libusb_unlock_events(ctx);
+			goto retry;
+		}
+		poll(libusb file descriptors, 120*1000);
+		if (poll indicates activity)
+			libusb_handle_events_locked(ctx, 0);
+	}
+	libusb_unlock_events(ctx);
+} else {
+	// another thread is doing event handling. wait for it to signal us that
+	// an event has completed
+	libusb_lock_event_waiters(ctx);
+
+	while (!completed) {
+		// now that we have the event waiters lock, double check that another
+		// thread is still handling events for us. (it may have ceased handling
+		// events in the time it took us to reach this point)
+		if (!libusb_event_handler_active(ctx)) {
+			// whoever was handling events is no longer doing so, try again
+			libusb_unlock_event_waiters(ctx);
+			goto retry;
+		}
+
+		libusb_wait_for_event(ctx, NULL);
+	}
+	libusb_unlock_event_waiters(ctx);
+}
+printf("completed!\n");
+\endcode
+ *
+ * A naive look at the above code may suggest that this can only support
+ * one event waiter (hence a total of 2 competing threads, the other doing
+ * event handling), because the event waiter seems to have taken the event
+ * waiters lock while waiting for an event. However, the system does support
+ * multiple event waiters, because libusb_wait_for_event() actually drops
+ * the lock while waiting, and reaquires it before continuing.
+ *
+ * We have now implemented code which can dynamically handle situations where
+ * nobody is handling events (so we should do it ourselves), and it can also
+ * handle situations where another thread is doing event handling (so we can
+ * piggyback onto them). It is also equipped to handle a combination of
+ * the two, for example, another thread is doing event handling, but for
+ * whatever reason it stops doing so before our condition is met, so we take
+ * over the event handling.
+ *
+ * Four functions were introduced in the above pseudo-code. Their importance
+ * should be apparent from the code shown above.
+ * -# libusb_try_lock_events() is a non-blocking function which attempts
+ *    to acquire the events lock but returns a failure code if it is contended.
+ * -# libusb_event_handling_ok() checks that libusb is still happy for your
+ *    thread to be performing event handling. Sometimes, libusb needs to
+ *    interrupt the event handler, and this is how you can check if you have
+ *    been interrupted. If this function returns 0, the correct behaviour is
+ *    for you to give up the event handling lock, and then to repeat the cycle.
+ *    The following libusb_try_lock_events() will fail, so you will become an
+ *    events waiter. For more information on this, read \ref fullstory below.
+ * -# libusb_handle_events_locked() is a variant of
+ *    libusb_handle_events_timeout() that you can call while holding the
+ *    events lock. libusb_handle_events_timeout() itself implements similar
+ *    logic to the above, so be sure not to call it when you are
+ *    "working behind libusb's back", as is the case here.
+ * -# libusb_event_handler_active() determines if someone is currently
+ *    holding the events lock
+ *
+ * You might be wondering why there is no function to wake up all threads
+ * blocked on libusb_wait_for_event(). This is because libusb can do this
+ * internally: it will wake up all such threads when someone calls
+ * libusb_unlock_events() or when a transfer completes (at the point after its
+ * callback has returned).
+ *
+ * \subsection fullstory The full story
+ *
+ * The above explanation should be enough to get you going, but if you're
+ * really thinking through the issues then you may be left with some more
+ * questions regarding libusb's internals. If you're curious, read on, and if
+ * not, skip to the next section to avoid confusing yourself!
+ *
+ * The immediate question that may spring to mind is: what if one thread
+ * modifies the set of file descriptors that need to be polled while another
+ * thread is doing event handling?
+ *
+ * There are 2 situations in which this may happen.
+ * -# libusb_open() will add another file descriptor to the poll set,
+ *    therefore it is desirable to interrupt the event handler so that it
+ *    restarts, picking up the new descriptor.
+ * -# libusb_close() will remove a file descriptor from the poll set. There
+ *    are all kinds of race conditions that could arise here, so it is
+ *    important that nobody is doing event handling at this time.
+ *
+ * libusb handles these issues internally, so application developers do not
+ * have to stop their event handlers while opening/closing devices. Here's how
+ * it works, focusing on the libusb_close() situation first:
+ *
+ * -# During initialization, libusb opens an internal pipe, and it adds the read
+ *    end of this pipe to the set of file descriptors to be polled.
+ * -# During libusb_close(), libusb writes some dummy data on this event pipe.
+ *    This immediately interrupts the event handler. libusb also records
+ *    internally that it is trying to interrupt event handlers for this
+ *    high-priority event.
+ * -# At this point, some of the functions described above start behaving
+ *    differently:
+ *   - libusb_event_handling_ok() starts returning 1, indicating that it is NOT
+ *     OK for event handling to continue.
+ *   - libusb_try_lock_events() starts returning 1, indicating that another
+ *     thread holds the event handling lock, even if the lock is uncontended.
+ *   - libusb_event_handler_active() starts returning 1, indicating that
+ *     another thread is doing event handling, even if that is not true.
+ * -# The above changes in behaviour result in the event handler stopping and
+ *    giving up the events lock very quickly, giving the high-priority
+ *    libusb_close() operation a "free ride" to acquire the events lock. All
+ *    threads that are competing to do event handling become event waiters.
+ * -# With the events lock held inside libusb_close(), libusb can safely remove
+ *    a file descriptor from the poll set, in the safety of knowledge that
+ *    nobody is polling those descriptors or trying to access the poll set.
+ * -# After obtaining the events lock, the close operation completes very
+ *    quickly (usually a matter of milliseconds) and then immediately releases
+ *    the events lock.
+ * -# At the same time, the behaviour of libusb_event_handling_ok() and friends
+ *    reverts to the original, documented behaviour.
+ * -# The release of the events lock causes the threads that are waiting for
+ *    events to be woken up and to start competing to become event handlers
+ *    again. One of them will succeed; it will then re-obtain the list of poll
+ *    descriptors, and USB I/O will then continue as normal.
+ *
+ * libusb_open() is similar, and is actually a more simplistic case. Upon a
+ * call to libusb_open():
+ *
+ * -# The device is opened and a file descriptor is added to the poll set.
+ * -# libusb sends some dummy data on the event pipe, and records that it
+ *    is trying to modify the poll descriptor set.
+ * -# The event handler is interrupted, and the same behaviour change as for
+ *    libusb_close() takes effect, causing all event handling threads to become
+ *    event waiters.
+ * -# The libusb_open() implementation takes its free ride to the events lock.
+ * -# Happy that it has successfully paused the events handler, libusb_open()
+ *    releases the events lock.
+ * -# The event waiter threads are all woken up and compete to become event
+ *    handlers again. The one that succeeds will obtain the list of poll
+ *    descriptors again, which will include the addition of the new device.
+ *
+ * \subsection concl Closing remarks
+ *
+ * The above may seem a little complicated, but hopefully I have made it clear
+ * why such complications are necessary. Also, do not forget that this only
+ * applies to applications that take libusb's file descriptors and integrate
+ * them into their own polling loops.
+ *
+ * You may decide that it is OK for your multi-threaded application to ignore
+ * some of the rules and locks detailed above, because you don't think that
+ * two threads can ever be polling the descriptors at the same time. If that
+ * is the case, then that's good news for you because you don't have to worry.
+ * But be careful here; remember that the synchronous I/O functions do event
+ * handling internally. If you have one thread doing event handling in a loop
+ * (without implementing the rules and locking semantics documented above)
+ * and another trying to send a synchronous USB transfer, you will end up with
+ * two threads monitoring the same descriptors, and the above-described
+ * undesirable behaviour occurring. The solution is for your polling thread to
+ * play by the rules; the synchronous I/O functions do so, and this will result
+ * in them getting along in perfect harmony.
+ *
+ * If you do have a dedicated thread doing event handling, it is perfectly
+ * legal for it to take the event handling lock for long periods of time. Any
+ * synchronous I/O functions you call from other threads will transparently
+ * fall back to the "event waiters" mechanism detailed above. The only
+ * consideration that your event handling thread must apply is the one related
+ * to libusb_event_handling_ok(): you must call this before every poll(), and
+ * give up the events lock if instructed.
+ */
+
+int usbi_io_init(struct libusb_context *ctx)
+{
+	int r;
+
+	usbi_mutex_init(&ctx->flying_transfers_lock);
+	usbi_mutex_init(&ctx->events_lock);
+	usbi_mutex_init(&ctx->event_waiters_lock);
+	usbi_cond_init(&ctx->event_waiters_cond);
+	usbi_mutex_init(&ctx->event_data_lock);
+	usbi_tls_key_create(&ctx->event_handling_key);
+	list_init(&ctx->flying_transfers);
+	list_init(&ctx->ipollfds);
+	list_init(&ctx->hotplug_msgs);
+	list_init(&ctx->completed_transfers);
+
+	/* FIXME should use an eventfd on kernels that support it */
+	r = usbi_pipe(ctx->event_pipe);
+	if (r < 0) {
+		r = LIBUSB_ERROR_OTHER;
+		goto err;
+	}
+
+	r = usbi_add_pollfd(ctx, ctx->event_pipe[0], POLLIN);
+	if (r < 0)
+		goto err_close_pipe;
+
+#ifdef USBI_TIMERFD_AVAILABLE
+	ctx->timerfd = timerfd_create(usbi_backend->get_timerfd_clockid(),
+		TFD_NONBLOCK);
+	if (ctx->timerfd >= 0) {
+		usbi_dbg("using timerfd for timeouts");
+		r = usbi_add_pollfd(ctx, ctx->timerfd, POLLIN);
+		if (r < 0)
+			goto err_close_timerfd;
+	} else {
+		usbi_dbg("timerfd not available (code %d error %d)", ctx->timerfd, errno);
+		ctx->timerfd = -1;
+	}
+#endif
+
+	return 0;
+
+#ifdef USBI_TIMERFD_AVAILABLE
+err_close_timerfd:
+	close(ctx->timerfd);
+	usbi_remove_pollfd(ctx, ctx->event_pipe[0]);
+#endif
+err_close_pipe:
+	usbi_close(ctx->event_pipe[0]);
+	usbi_close(ctx->event_pipe[1]);
+err:
+	usbi_mutex_destroy(&ctx->flying_transfers_lock);
+	usbi_mutex_destroy(&ctx->events_lock);
+	usbi_mutex_destroy(&ctx->event_waiters_lock);
+	usbi_cond_destroy(&ctx->event_waiters_cond);
+	usbi_mutex_destroy(&ctx->event_data_lock);
+	usbi_tls_key_delete(ctx->event_handling_key);
+	return r;
+}
+
+void usbi_io_exit(struct libusb_context *ctx)
+{
+	usbi_remove_pollfd(ctx, ctx->event_pipe[0]);
+	usbi_close(ctx->event_pipe[0]);
+	usbi_close(ctx->event_pipe[1]);
+#ifdef USBI_TIMERFD_AVAILABLE
+	if (usbi_using_timerfd(ctx)) {
+		usbi_remove_pollfd(ctx, ctx->timerfd);
+		close(ctx->timerfd);
+	}
+#endif
+	usbi_mutex_destroy(&ctx->flying_transfers_lock);
+	usbi_mutex_destroy(&ctx->events_lock);
+	usbi_mutex_destroy(&ctx->event_waiters_lock);
+	usbi_cond_destroy(&ctx->event_waiters_cond);
+	usbi_mutex_destroy(&ctx->event_data_lock);
+	usbi_tls_key_delete(ctx->event_handling_key);
+	if (ctx->pollfds)
+		free(ctx->pollfds);
+}
+
+static int calculate_timeout(struct usbi_transfer *transfer)
+{
+	int r;
+	struct timespec current_time;
+	unsigned int timeout =
+		USBI_TRANSFER_TO_LIBUSB_TRANSFER(transfer)->timeout;
+
+	if (!timeout)
+		return 0;
+
+	r = usbi_backend->clock_gettime(USBI_CLOCK_MONOTONIC, &current_time);
+	if (r < 0) {
+		usbi_err(ITRANSFER_CTX(transfer),
+			"failed to read monotonic clock, errno=%d", errno);
+		return r;
+	}
+
+	current_time.tv_sec += timeout / 1000;
+	current_time.tv_nsec += (timeout % 1000) * 1000000;
+
+	while (current_time.tv_nsec >= 1000000000) {
+		current_time.tv_nsec -= 1000000000;
+		current_time.tv_sec++;
+	}
+
+	TIMESPEC_TO_TIMEVAL(&transfer->timeout, &current_time);
+	return 0;
+}
+
+/** \ingroup libusb_asyncio
+ * Allocate a libusb transfer with a specified number of isochronous packet
+ * descriptors. The returned transfer is pre-initialized for you. When the new
+ * transfer is no longer needed, it should be freed with
+ * libusb_free_transfer().
+ *
+ * Transfers intended for non-isochronous endpoints (e.g. control, bulk,
+ * interrupt) should specify an iso_packets count of zero.
+ *
+ * For transfers intended for isochronous endpoints, specify an appropriate
+ * number of packet descriptors to be allocated as part of the transfer.
+ * The returned transfer is not specially initialized for isochronous I/O;
+ * you are still required to set the
+ * \ref libusb_transfer::num_iso_packets "num_iso_packets" and
+ * \ref libusb_transfer::type "type" fields accordingly.
+ *
+ * It is safe to allocate a transfer with some isochronous packets and then
+ * use it on a non-isochronous endpoint. If you do this, ensure that at time
+ * of submission, num_iso_packets is 0 and that type is set appropriately.
+ *
+ * \param iso_packets number of isochronous packet descriptors to allocate
+ * \returns a newly allocated transfer, or NULL on error
+ */
+DEFAULT_VISIBILITY
+struct libusb_transfer * LIBUSB_CALL libusb_alloc_transfer(
+	int iso_packets)
+{
+	struct libusb_transfer *transfer;
+	size_t os_alloc_size = usbi_backend->transfer_priv_size;
+	size_t alloc_size = sizeof(struct usbi_transfer)
+		+ sizeof(struct libusb_transfer)
+		+ (sizeof(struct libusb_iso_packet_descriptor) * iso_packets)
+		+ os_alloc_size;
+	struct usbi_transfer *itransfer = calloc(1, alloc_size);
+	if (!itransfer)
+		return NULL;
+
+	itransfer->num_iso_packets = iso_packets;
+	usbi_mutex_init(&itransfer->lock);
+	transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	usbi_dbg("transfer %p", transfer);
+	return transfer;
+}
+
+/** \ingroup libusb_asyncio
+ * Free a transfer structure. This should be called for all transfers
+ * allocated with libusb_alloc_transfer().
+ *
+ * If the \ref libusb_transfer_flags::LIBUSB_TRANSFER_FREE_BUFFER
+ * "LIBUSB_TRANSFER_FREE_BUFFER" flag is set and the transfer buffer is
+ * non-NULL, this function will also free the transfer buffer using the
+ * standard system memory allocator (e.g. free()).
+ *
+ * It is legal to call this function with a NULL transfer. In this case,
+ * the function will simply return safely.
+ *
+ * It is not legal to free an active transfer (one which has been submitted
+ * and has not yet completed).
+ *
+ * \param transfer the transfer to free
+ */
+void API_EXPORTED libusb_free_transfer(struct libusb_transfer *transfer)
+{
+	struct usbi_transfer *itransfer;
+	if (!transfer)
+		return;
+
+	usbi_dbg("transfer %p", transfer);
+	if (transfer->flags & LIBUSB_TRANSFER_FREE_BUFFER && transfer->buffer)
+		free(transfer->buffer);
+
+	itransfer = LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer);
+	usbi_mutex_destroy(&itransfer->lock);
+	free(itransfer);
+}
+
+#ifdef USBI_TIMERFD_AVAILABLE
+static int disarm_timerfd(struct libusb_context *ctx)
+{
+	const struct itimerspec disarm_timer = { { 0, 0 }, { 0, 0 } };
+	int r;
+
+	usbi_dbg("");
+	r = timerfd_settime(ctx->timerfd, 0, &disarm_timer, NULL);
+	if (r < 0)
+		return LIBUSB_ERROR_OTHER;
+	else
+		return 0;
+}
+
+/* iterates through the flying transfers, and rearms the timerfd based on the
+ * next upcoming timeout.
+ * must be called with flying_list locked.
+ * returns 0 on success or a LIBUSB_ERROR code on failure.
+ */
+static int arm_timerfd_for_next_timeout(struct libusb_context *ctx)
+{
+	struct usbi_transfer *transfer;
+
+	list_for_each_entry(transfer, &ctx->flying_transfers, list, struct usbi_transfer) {
+		struct timeval *cur_tv = &transfer->timeout;
+
+		/* if we've reached transfers of infinite timeout, then we have no
+		 * arming to do */
+		if (!timerisset(cur_tv))
+			goto disarm;
+
+		/* act on first transfer that has not already been handled */
+		if (!(transfer->timeout_flags & (USBI_TRANSFER_TIMEOUT_HANDLED | USBI_TRANSFER_OS_HANDLES_TIMEOUT))) {
+			int r;
+			const struct itimerspec it = { {0, 0},
+				{ cur_tv->tv_sec, cur_tv->tv_usec * 1000 } };
+			usbi_dbg("next timeout originally %dms", USBI_TRANSFER_TO_LIBUSB_TRANSFER(transfer)->timeout);
+			r = timerfd_settime(ctx->timerfd, TFD_TIMER_ABSTIME, &it, NULL);
+			if (r < 0)
+				return LIBUSB_ERROR_OTHER;
+			return 0;
+		}
+	}
+
+disarm:
+	return disarm_timerfd(ctx);
+}
+#else
+static int arm_timerfd_for_next_timeout(struct libusb_context *ctx)
+{
+	UNUSED(ctx);
+	return 0;
+}
+#endif
+
+/* add a transfer to the (timeout-sorted) active transfers list.
+ * This function will return non 0 if fails to update the timer,
+ * in which case the transfer is *not* on the flying_transfers list. */
+static int add_to_flying_list(struct usbi_transfer *transfer)
+{
+	struct usbi_transfer *cur;
+	struct timeval *timeout = &transfer->timeout;
+	struct libusb_context *ctx = ITRANSFER_CTX(transfer);
+	int r;
+	int first = 1;
+
+	r = calculate_timeout(transfer);
+	if (r)
+		return r;
+
+	/* if we have no other flying transfers, start the list with this one */
+	if (list_empty(&ctx->flying_transfers)) {
+		list_add(&transfer->list, &ctx->flying_transfers);
+		goto out;
+	}
+
+	/* if we have infinite timeout, append to end of list */
+	if (!timerisset(timeout)) {
+		list_add_tail(&transfer->list, &ctx->flying_transfers);
+		/* first is irrelevant in this case */
+		goto out;
+	}
+
+	/* otherwise, find appropriate place in list */
+	list_for_each_entry(cur, &ctx->flying_transfers, list, struct usbi_transfer) {
+		/* find first timeout that occurs after the transfer in question */
+		struct timeval *cur_tv = &cur->timeout;
+
+		if (!timerisset(cur_tv) || (cur_tv->tv_sec > timeout->tv_sec) ||
+				(cur_tv->tv_sec == timeout->tv_sec &&
+					cur_tv->tv_usec > timeout->tv_usec)) {
+			list_add_tail(&transfer->list, &cur->list);
+			goto out;
+		}
+		first = 0;
+	}
+	/* first is 0 at this stage (list not empty) */
+
+	/* otherwise we need to be inserted at the end */
+	list_add_tail(&transfer->list, &ctx->flying_transfers);
+out:
+#ifdef USBI_TIMERFD_AVAILABLE
+	if (first && usbi_using_timerfd(ctx) && timerisset(timeout)) {
+		/* if this transfer has the lowest timeout of all active transfers,
+		 * rearm the timerfd with this transfer's timeout */
+		const struct itimerspec it = { {0, 0},
+			{ timeout->tv_sec, timeout->tv_usec * 1000 } };
+		usbi_dbg("arm timerfd for timeout in %dms (first in line)",
+			USBI_TRANSFER_TO_LIBUSB_TRANSFER(transfer)->timeout);
+		r = timerfd_settime(ctx->timerfd, TFD_TIMER_ABSTIME, &it, NULL);
+		if (r < 0) {
+			usbi_warn(ctx, "failed to arm first timerfd (errno %d)", errno);
+			r = LIBUSB_ERROR_OTHER;
+		}
+	}
+#else
+	UNUSED(first);
+#endif
+
+	if (r)
+		list_del(&transfer->list);
+
+	return r;
+}
+
+/* remove a transfer from the active transfers list.
+ * This function will *always* remove the transfer from the
+ * flying_transfers list. It will return a LIBUSB_ERROR code
+ * if it fails to update the timer for the next timeout. */
+static int remove_from_flying_list(struct usbi_transfer *transfer)
+{
+	struct libusb_context *ctx = ITRANSFER_CTX(transfer);
+	int rearm_timerfd;
+	int r = 0;
+
+	usbi_mutex_lock(&ctx->flying_transfers_lock);
+	rearm_timerfd = (timerisset(&transfer->timeout) &&
+		list_first_entry(&ctx->flying_transfers, struct usbi_transfer, list) == transfer);
+	list_del(&transfer->list);
+	if (usbi_using_timerfd(ctx) && rearm_timerfd)
+		r = arm_timerfd_for_next_timeout(ctx);
+	usbi_mutex_unlock(&ctx->flying_transfers_lock);
+
+	return r;
+}
+
+/** \ingroup libusb_asyncio
+ * Submit a transfer. This function will fire off the USB transfer and then
+ * return immediately.
+ *
+ * \param transfer the transfer to submit
+ * \returns 0 on success
+ * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
+ * \returns LIBUSB_ERROR_BUSY if the transfer has already been submitted.
+ * \returns LIBUSB_ERROR_NOT_SUPPORTED if the transfer flags are not supported
+ * by the operating system.
+ * \returns LIBUSB_ERROR_INVALID_PARAM if the transfer size is larger than
+ * the operating system and/or hardware can support
+ * \returns another LIBUSB_ERROR code on other failure
+ */
+int API_EXPORTED libusb_submit_transfer(struct libusb_transfer *transfer)
+{
+	struct usbi_transfer *itransfer =
+		LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer);
+	struct libusb_context *ctx = TRANSFER_CTX(transfer);
+	int r;
+
+	usbi_dbg("transfer %p", transfer);
+
+	/*
+	 * Important note on locking, this function takes / releases locks
+	 * in the following order:
+	 *  take flying_transfers_lock
+	 *  take itransfer->lock
+	 *  clear transfer
+	 *  add to flying_transfers list
+	 *  release flying_transfers_lock
+	 *  submit transfer
+	 *  release itransfer->lock
+	 *  if submit failed:
+	 *   take flying_transfers_lock
+	 *   remove from flying_transfers list
+	 *   release flying_transfers_lock
+	 *
+	 * Note that it takes locks in the order a-b and then releases them
+	 * in the same order a-b. This is somewhat unusual but not wrong,
+	 * release order is not important as long as *all* locks are released
+	 * before re-acquiring any locks.
+	 *
+	 * This means that the ordering of first releasing itransfer->lock
+	 * and then re-acquiring the flying_transfers_list on error is
+	 * important and must not be changed!
+	 *
+	 * This is done this way because when we take both locks we must always
+	 * take flying_transfers_lock first to avoid ab-ba style deadlocks with
+	 * the timeout handling and usbi_handle_disconnect paths.
+	 *
+	 * And we cannot release itransfer->lock before the submission is
+	 * complete otherwise timeout handling for transfers with short
+	 * timeouts may run before submission.
+	 */
+	usbi_mutex_lock(&ctx->flying_transfers_lock);
+	usbi_mutex_lock(&itransfer->lock);
+	if (itransfer->state_flags & USBI_TRANSFER_IN_FLIGHT) {
+		usbi_mutex_unlock(&ctx->flying_transfers_lock);
+		usbi_mutex_unlock(&itransfer->lock);
+		return LIBUSB_ERROR_BUSY;
+	}
+	itransfer->transferred = 0;
+	itransfer->state_flags = 0;
+	itransfer->timeout_flags = 0;
+	r = add_to_flying_list(itransfer);
+	if (r) {
+		usbi_mutex_unlock(&ctx->flying_transfers_lock);
+		usbi_mutex_unlock(&itransfer->lock);
+		return r;
+	}
+	/*
+	 * We must release the flying transfers lock here, because with
+	 * some backends the submit_transfer method is synchroneous.
+	 */
+	usbi_mutex_unlock(&ctx->flying_transfers_lock);
+
+	r = usbi_backend->submit_transfer(itransfer);
+	if (r == LIBUSB_SUCCESS) {
+		itransfer->state_flags |= USBI_TRANSFER_IN_FLIGHT;
+		/* keep a reference to this device */
+		libusb_ref_device(transfer->dev_handle->dev);
+	}
+	usbi_mutex_unlock(&itransfer->lock);
+
+	if (r != LIBUSB_SUCCESS)
+		remove_from_flying_list(itransfer);
+
+	return r;
+}
+
+/** \ingroup libusb_asyncio
+ * Asynchronously cancel a previously submitted transfer.
+ * This function returns immediately, but this does not indicate cancellation
+ * is complete. Your callback function will be invoked at some later time
+ * with a transfer status of
+ * \ref libusb_transfer_status::LIBUSB_TRANSFER_CANCELLED
+ * "LIBUSB_TRANSFER_CANCELLED."
+ *
+ * \param transfer the transfer to cancel
+ * \returns 0 on success
+ * \returns LIBUSB_ERROR_NOT_FOUND if the transfer is not in progress,
+ * already complete, or already cancelled.
+ * \returns a LIBUSB_ERROR code on failure
+ */
+int API_EXPORTED libusb_cancel_transfer(struct libusb_transfer *transfer)
+{
+	struct usbi_transfer *itransfer =
+		LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer);
+	int r;
+
+	usbi_dbg("transfer %p", transfer );
+	usbi_mutex_lock(&itransfer->lock);
+	if (!(itransfer->state_flags & USBI_TRANSFER_IN_FLIGHT)
+			|| (itransfer->state_flags & USBI_TRANSFER_CANCELLING)) {
+		r = LIBUSB_ERROR_NOT_FOUND;
+		goto out;
+	}
+	r = usbi_backend->cancel_transfer(itransfer);
+	if (r < 0) {
+		if (r != LIBUSB_ERROR_NOT_FOUND &&
+		    r != LIBUSB_ERROR_NO_DEVICE)
+			usbi_err(TRANSFER_CTX(transfer),
+				"cancel transfer failed error %d", r);
+		else
+			usbi_dbg("cancel transfer failed error %d", r);
+
+		if (r == LIBUSB_ERROR_NO_DEVICE)
+			itransfer->state_flags |= USBI_TRANSFER_DEVICE_DISAPPEARED;
+	}
+
+	itransfer->state_flags |= USBI_TRANSFER_CANCELLING;
+
+out:
+	usbi_mutex_unlock(&itransfer->lock);
+	return r;
+}
+
+/** \ingroup libusb_asyncio
+ * Set a transfers bulk stream id. Note users are advised to use
+ * libusb_fill_bulk_stream_transfer() instead of calling this function
+ * directly.
+ *
+ * Since version 1.0.19, \ref LIBUSB_API_VERSION >= 0x01000103
+ *
+ * \param transfer the transfer to set the stream id for
+ * \param stream_id the stream id to set
+ * \see libusb_alloc_streams()
+ */
+void API_EXPORTED libusb_transfer_set_stream_id(
+	struct libusb_transfer *transfer, uint32_t stream_id)
+{
+	struct usbi_transfer *itransfer =
+		LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer);
+
+	itransfer->stream_id = stream_id;
+}
+
+/** \ingroup libusb_asyncio
+ * Get a transfers bulk stream id.
+ *
+ * Since version 1.0.19, \ref LIBUSB_API_VERSION >= 0x01000103
+ *
+ * \param transfer the transfer to get the stream id for
+ * \returns the stream id for the transfer
+ */
+uint32_t API_EXPORTED libusb_transfer_get_stream_id(
+	struct libusb_transfer *transfer)
+{
+	struct usbi_transfer *itransfer =
+		LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer);
+
+	return itransfer->stream_id;
+}
+
+/* Handle completion of a transfer (completion might be an error condition).
+ * This will invoke the user-supplied callback function, which may end up
+ * freeing the transfer. Therefore you cannot use the transfer structure
+ * after calling this function, and you should free all backend-specific
+ * data before calling it.
+ * Do not call this function with the usbi_transfer lock held. User-specified
+ * callback functions may attempt to directly resubmit the transfer, which
+ * will attempt to take the lock. */
+int usbi_handle_transfer_completion(struct usbi_transfer *itransfer,
+	enum libusb_transfer_status status)
+{
+	struct libusb_transfer *transfer =
+		USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	struct libusb_device_handle *dev_handle = transfer->dev_handle;
+	uint8_t flags;
+	int r;
+
+	r = remove_from_flying_list(itransfer);
+	if (r < 0)
+		usbi_err(ITRANSFER_CTX(itransfer), "failed to set timer for next timeout, errno=%d", errno);
+
+	usbi_mutex_lock(&itransfer->lock);
+	itransfer->state_flags &= ~USBI_TRANSFER_IN_FLIGHT;
+	usbi_mutex_unlock(&itransfer->lock);
+
+	if (status == LIBUSB_TRANSFER_COMPLETED
+			&& transfer->flags & LIBUSB_TRANSFER_SHORT_NOT_OK) {
+		int rqlen = transfer->length;
+		if (transfer->type == LIBUSB_TRANSFER_TYPE_CONTROL)
+			rqlen -= LIBUSB_CONTROL_SETUP_SIZE;
+		if (rqlen != itransfer->transferred) {
+			usbi_dbg("interpreting short transfer as error");
+			status = LIBUSB_TRANSFER_ERROR;
+		}
+	}
+
+	flags = transfer->flags;
+	transfer->status = status;
+	transfer->actual_length = itransfer->transferred;
+	usbi_dbg("transfer %p has callback %p", transfer, transfer->callback);
+	if (transfer->callback)
+		transfer->callback(transfer);
+	/* transfer might have been freed by the above call, do not use from
+	 * this point. */
+	if (flags & LIBUSB_TRANSFER_FREE_TRANSFER)
+		libusb_free_transfer(transfer);
+	libusb_unref_device(dev_handle->dev);
+	return r;
+}
+
+/* Similar to usbi_handle_transfer_completion() but exclusively for transfers
+ * that were asynchronously cancelled. The same concerns w.r.t. freeing of
+ * transfers exist here.
+ * Do not call this function with the usbi_transfer lock held. User-specified
+ * callback functions may attempt to directly resubmit the transfer, which
+ * will attempt to take the lock. */
+int usbi_handle_transfer_cancellation(struct usbi_transfer *transfer)
+{
+	struct libusb_context *ctx = ITRANSFER_CTX(transfer);
+	uint8_t timed_out;
+
+	usbi_mutex_lock(&ctx->flying_transfers_lock);
+	timed_out = transfer->timeout_flags & USBI_TRANSFER_TIMED_OUT;
+	usbi_mutex_unlock(&ctx->flying_transfers_lock);
+
+	/* if the URB was cancelled due to timeout, report timeout to the user */
+	if (timed_out) {
+		usbi_dbg("detected timeout cancellation");
+		return usbi_handle_transfer_completion(transfer, LIBUSB_TRANSFER_TIMED_OUT);
+	}
+
+	/* otherwise its a normal async cancel */
+	return usbi_handle_transfer_completion(transfer, LIBUSB_TRANSFER_CANCELLED);
+}
+
+/* Add a completed transfer to the completed_transfers list of the
+ * context and signal the event. The backend's handle_transfer_completion()
+ * function will be called the next time an event handler runs. */
+void usbi_signal_transfer_completion(struct usbi_transfer *transfer)
+{
+	struct libusb_context *ctx = ITRANSFER_CTX(transfer);
+	int pending_events;
+
+	usbi_mutex_lock(&ctx->event_data_lock);
+	pending_events = usbi_pending_events(ctx);
+	list_add_tail(&transfer->completed_list, &ctx->completed_transfers);
+	if (!pending_events)
+		usbi_signal_event(ctx);
+	usbi_mutex_unlock(&ctx->event_data_lock);
+}
+
+/** \ingroup libusb_poll
+ * Attempt to acquire the event handling lock. This lock is used to ensure that
+ * only one thread is monitoring libusb event sources at any one time.
+ *
+ * You only need to use this lock if you are developing an application
+ * which calls poll() or select() on libusb's file descriptors directly.
+ * If you stick to libusb's event handling loop functions (e.g.
+ * libusb_handle_events()) then you do not need to be concerned with this
+ * locking.
+ *
+ * While holding this lock, you are trusted to actually be handling events.
+ * If you are no longer handling events, you must call libusb_unlock_events()
+ * as soon as possible.
+ *
+ * \param ctx the context to operate on, or NULL for the default context
+ * \returns 0 if the lock was obtained successfully
+ * \returns 1 if the lock was not obtained (i.e. another thread holds the lock)
+ * \ref libusb_mtasync
+ */
+int API_EXPORTED libusb_try_lock_events(libusb_context *ctx)
+{
+	int r;
+	unsigned int ru;
+	USBI_GET_CONTEXT(ctx);
+
+	/* is someone else waiting to close a device? if so, don't let this thread
+	 * start event handling */
+	usbi_mutex_lock(&ctx->event_data_lock);
+	ru = ctx->device_close;
+	usbi_mutex_unlock(&ctx->event_data_lock);
+	if (ru) {
+		usbi_dbg("someone else is closing a device");
+		return 1;
+	}
+
+	r = usbi_mutex_trylock(&ctx->events_lock);
+	if (r)
+		return 1;
+
+	ctx->event_handler_active = 1;
+	return 0;
+}
+
+/** \ingroup libusb_poll
+ * Acquire the event handling lock, blocking until successful acquisition if
+ * it is contended. This lock is used to ensure that only one thread is
+ * monitoring libusb event sources at any one time.
+ *
+ * You only need to use this lock if you are developing an application
+ * which calls poll() or select() on libusb's file descriptors directly.
+ * If you stick to libusb's event handling loop functions (e.g.
+ * libusb_handle_events()) then you do not need to be concerned with this
+ * locking.
+ *
+ * While holding this lock, you are trusted to actually be handling events.
+ * If you are no longer handling events, you must call libusb_unlock_events()
+ * as soon as possible.
+ *
+ * \param ctx the context to operate on, or NULL for the default context
+ * \ref libusb_mtasync
+ */
+void API_EXPORTED libusb_lock_events(libusb_context *ctx)
+{
+	USBI_GET_CONTEXT(ctx);
+	usbi_mutex_lock(&ctx->events_lock);
+	ctx->event_handler_active = 1;
+}
+
+/** \ingroup libusb_poll
+ * Release the lock previously acquired with libusb_try_lock_events() or
+ * libusb_lock_events(). Releasing this lock will wake up any threads blocked
+ * on libusb_wait_for_event().
+ *
+ * \param ctx the context to operate on, or NULL for the default context
+ * \ref libusb_mtasync
+ */
+void API_EXPORTED libusb_unlock_events(libusb_context *ctx)
+{
+	USBI_GET_CONTEXT(ctx);
+	ctx->event_handler_active = 0;
+	usbi_mutex_unlock(&ctx->events_lock);
+
+	/* FIXME: perhaps we should be a bit more efficient by not broadcasting
+	 * the availability of the events lock when we are modifying pollfds
+	 * (check ctx->device_close)? */
+	usbi_mutex_lock(&ctx->event_waiters_lock);
+	usbi_cond_broadcast(&ctx->event_waiters_cond);
+	usbi_mutex_unlock(&ctx->event_waiters_lock);
+}
+
+/** \ingroup libusb_poll
+ * Determine if it is still OK for this thread to be doing event handling.
+ *
+ * Sometimes, libusb needs to temporarily pause all event handlers, and this
+ * is the function you should use before polling file descriptors to see if
+ * this is the case.
+ *
+ * If this function instructs your thread to give up the events lock, you
+ * should just continue the usual logic that is documented in \ref libusb_mtasync.
+ * On the next iteration, your thread will fail to obtain the events lock,
+ * and will hence become an event waiter.
+ *
+ * This function should be called while the events lock is held: you don't
+ * need to worry about the results of this function if your thread is not
+ * the current event handler.
+ *
+ * \param ctx the context to operate on, or NULL for the default context
+ * \returns 1 if event handling can start or continue
+ * \returns 0 if this thread must give up the events lock
+ * \ref fullstory "Multi-threaded I/O: the full story"
+ */
+int API_EXPORTED libusb_event_handling_ok(libusb_context *ctx)
+{
+	unsigned int r;
+	USBI_GET_CONTEXT(ctx);
+
+	/* is someone else waiting to close a device? if so, don't let this thread
+	 * continue event handling */
+	usbi_mutex_lock(&ctx->event_data_lock);
+	r = ctx->device_close;
+	usbi_mutex_unlock(&ctx->event_data_lock);
+	if (r) {
+		usbi_dbg("someone else is closing a device");
+		return 0;
+	}
+
+	return 1;
+}
+
+
+/** \ingroup libusb_poll
+ * Determine if an active thread is handling events (i.e. if anyone is holding
+ * the event handling lock).
+ *
+ * \param ctx the context to operate on, or NULL for the default context
+ * \returns 1 if a thread is handling events
+ * \returns 0 if there are no threads currently handling events
+ * \ref libusb_mtasync
+ */
+int API_EXPORTED libusb_event_handler_active(libusb_context *ctx)
+{
+	unsigned int r;
+	USBI_GET_CONTEXT(ctx);
+
+	/* is someone else waiting to close a device? if so, don't let this thread
+	 * start event handling -- indicate that event handling is happening */
+	usbi_mutex_lock(&ctx->event_data_lock);
+	r = ctx->device_close;
+	usbi_mutex_unlock(&ctx->event_data_lock);
+	if (r) {
+		usbi_dbg("someone else is closing a device");
+		return 1;
+	}
+
+	return ctx->event_handler_active;
+}
+
+/** \ingroup libusb_poll
+ * Interrupt any active thread that is handling events. This is mainly useful
+ * for interrupting a dedicated event handling thread when an application
+ * wishes to call libusb_exit().
+ *
+ * Since version 1.0.21, \ref LIBUSB_API_VERSION >= 0x01000105
+ *
+ * \param ctx the context to operate on, or NULL for the default context
+ * \ref libusb_mtasync
+ */
+void API_EXPORTED libusb_interrupt_event_handler(libusb_context *ctx)
+{
+	int pending_events;
+	USBI_GET_CONTEXT(ctx);
+
+	usbi_dbg("");
+	usbi_mutex_lock(&ctx->event_data_lock);
+
+	pending_events = usbi_pending_events(ctx);
+	ctx->event_flags |= USBI_EVENT_USER_INTERRUPT;
+	if (!pending_events)
+		usbi_signal_event(ctx);
+
+	usbi_mutex_unlock(&ctx->event_data_lock);
+}
+
+/** \ingroup libusb_poll
+ * Acquire the event waiters lock. This lock is designed to be obtained under
+ * the situation where you want to be aware when events are completed, but
+ * some other thread is event handling so calling libusb_handle_events() is not
+ * allowed.
+ *
+ * You then obtain this lock, re-check that another thread is still handling
+ * events, then call libusb_wait_for_event().
+ *
+ * You only need to use this lock if you are developing an application
+ * which calls poll() or select() on libusb's file descriptors directly,
+ * <b>and</b> may potentially be handling events from 2 threads simultaenously.
+ * If you stick to libusb's event handling loop functions (e.g.
+ * libusb_handle_events()) then you do not need to be concerned with this
+ * locking.
+ *
+ * \param ctx the context to operate on, or NULL for the default context
+ * \ref libusb_mtasync
+ */
+void API_EXPORTED libusb_lock_event_waiters(libusb_context *ctx)
+{
+	USBI_GET_CONTEXT(ctx);
+	usbi_mutex_lock(&ctx->event_waiters_lock);
+}
+
+/** \ingroup libusb_poll
+ * Release the event waiters lock.
+ * \param ctx the context to operate on, or NULL for the default context
+ * \ref libusb_mtasync
+ */
+void API_EXPORTED libusb_unlock_event_waiters(libusb_context *ctx)
+{
+	USBI_GET_CONTEXT(ctx);
+	usbi_mutex_unlock(&ctx->event_waiters_lock);
+}
+
+/** \ingroup libusb_poll
+ * Wait for another thread to signal completion of an event. Must be called
+ * with the event waiters lock held, see libusb_lock_event_waiters().
+ *
+ * This function will block until any of the following conditions are met:
+ * -# The timeout expires
+ * -# A transfer completes
+ * -# A thread releases the event handling lock through libusb_unlock_events()
+ *
+ * Condition 1 is obvious. Condition 2 unblocks your thread <em>after</em>
+ * the callback for the transfer has completed. Condition 3 is important
+ * because it means that the thread that was previously handling events is no
+ * longer doing so, so if any events are to complete, another thread needs to
+ * step up and start event handling.
+ *
+ * This function releases the event waiters lock before putting your thread
+ * to sleep, and reacquires the lock as it is being woken up.
+ *
+ * \param ctx the context to operate on, or NULL for the default context
+ * \param tv maximum timeout for this blocking function. A NULL value
+ * indicates unlimited timeout.
+ * \returns 0 after a transfer completes or another thread stops event handling
+ * \returns 1 if the timeout expired
+ * \ref libusb_mtasync
+ */
+int API_EXPORTED libusb_wait_for_event(libusb_context *ctx, struct timeval *tv)
+{
+	int r;
+
+	USBI_GET_CONTEXT(ctx);
+	if (tv == NULL) {
+		usbi_cond_wait(&ctx->event_waiters_cond, &ctx->event_waiters_lock);
+		return 0;
+	}
+
+	r = usbi_cond_timedwait(&ctx->event_waiters_cond,
+		&ctx->event_waiters_lock, tv);
+
+	if (r < 0)
+		return r;
+	else
+		return (r == ETIMEDOUT);
+}
+
+static void handle_timeout(struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer =
+		USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	int r;
+
+	itransfer->timeout_flags |= USBI_TRANSFER_TIMEOUT_HANDLED;
+	r = libusb_cancel_transfer(transfer);
+	if (r == LIBUSB_SUCCESS)
+		itransfer->timeout_flags |= USBI_TRANSFER_TIMED_OUT;
+	else
+		usbi_warn(TRANSFER_CTX(transfer),
+			"async cancel failed %d errno=%d", r, errno);
+}
+
+static int handle_timeouts_locked(struct libusb_context *ctx)
+{
+	int r;
+	struct timespec systime_ts;
+	struct timeval systime;
+	struct usbi_transfer *transfer;
+
+	if (list_empty(&ctx->flying_transfers))
+		return 0;
+
+	/* get current time */
+	r = usbi_backend->clock_gettime(USBI_CLOCK_MONOTONIC, &systime_ts);
+	if (r < 0)
+		return r;
+
+	TIMESPEC_TO_TIMEVAL(&systime, &systime_ts);
+
+	/* iterate through flying transfers list, finding all transfers that
+	 * have expired timeouts */
+	list_for_each_entry(transfer, &ctx->flying_transfers, list, struct usbi_transfer) {
+		struct timeval *cur_tv = &transfer->timeout;
+
+		/* if we've reached transfers of infinite timeout, we're all done */
+		if (!timerisset(cur_tv))
+			return 0;
+
+		/* ignore timeouts we've already handled */
+		if (transfer->timeout_flags & (USBI_TRANSFER_TIMEOUT_HANDLED | USBI_TRANSFER_OS_HANDLES_TIMEOUT))
+			continue;
+
+		/* if transfer has non-expired timeout, nothing more to do */
+		if ((cur_tv->tv_sec > systime.tv_sec) ||
+				(cur_tv->tv_sec == systime.tv_sec &&
+					cur_tv->tv_usec > systime.tv_usec))
+			return 0;
+
+		/* otherwise, we've got an expired timeout to handle */
+		handle_timeout(transfer);
+	}
+	return 0;
+}
+
+static int handle_timeouts(struct libusb_context *ctx)
+{
+	int r;
+	USBI_GET_CONTEXT(ctx);
+	usbi_mutex_lock(&ctx->flying_transfers_lock);
+	r = handle_timeouts_locked(ctx);
+	usbi_mutex_unlock(&ctx->flying_transfers_lock);
+	return r;
+}
+
+#ifdef USBI_TIMERFD_AVAILABLE
+static int handle_timerfd_trigger(struct libusb_context *ctx)
+{
+	int r;
+
+	usbi_mutex_lock(&ctx->flying_transfers_lock);
+
+	/* process the timeout that just happened */
+	r = handle_timeouts_locked(ctx);
+	if (r < 0)
+		goto out;
+
+	/* arm for next timeout*/
+	r = arm_timerfd_for_next_timeout(ctx);
+
+out:
+	usbi_mutex_unlock(&ctx->flying_transfers_lock);
+	return r;
+}
+#endif
+
+/* do the actual event handling. assumes that no other thread is concurrently
+ * doing the same thing. */
+static int handle_events(struct libusb_context *ctx, struct timeval *tv)
+{
+	int r;
+	struct usbi_pollfd *ipollfd;
+	POLL_NFDS_TYPE nfds = 0;
+	POLL_NFDS_TYPE internal_nfds;
+	struct pollfd *fds = NULL;
+	int i = -1;
+	int timeout_ms;
+	int special_event;
+
+	/* prevent attempts to recursively handle events (e.g. calling into
+	 * libusb_handle_events() from within a hotplug or transfer callback) */
+	if (usbi_handling_events(ctx))
+		return LIBUSB_ERROR_BUSY;
+	usbi_start_event_handling(ctx);
+
+	/* there are certain fds that libusb uses internally, currently:
+	 *
+	 *   1) event pipe
+	 *   2) timerfd
+	 *
+	 * the backend will never need to attempt to handle events on these fds, so
+	 * we determine how many fds are in use internally for this context and when
+	 * handle_events() is called in the backend, the pollfd list and count will
+	 * be adjusted to skip over these internal fds */
+	if (usbi_using_timerfd(ctx))
+		internal_nfds = 2;
+	else
+		internal_nfds = 1;
+
+	/* only reallocate the poll fds when the list of poll fds has been modified
+	 * since the last poll, otherwise reuse them to save the additional overhead */
+	usbi_mutex_lock(&ctx->event_data_lock);
+	if (ctx->event_flags & USBI_EVENT_POLLFDS_MODIFIED) {
+		usbi_dbg("poll fds modified, reallocating");
+
+		if (ctx->pollfds) {
+			free(ctx->pollfds);
+			ctx->pollfds = NULL;
+		}
+
+		/* sanity check - it is invalid for a context to have fewer than the
+		 * required internal fds (memory corruption?) */
+		assert(ctx->pollfds_cnt >= internal_nfds);
+
+		ctx->pollfds = calloc(ctx->pollfds_cnt, sizeof(*ctx->pollfds));
+		if (!ctx->pollfds) {
+			usbi_mutex_unlock(&ctx->event_data_lock);
+			r = LIBUSB_ERROR_NO_MEM;
+			goto done;
+		}
+
+		list_for_each_entry(ipollfd, &ctx->ipollfds, list, struct usbi_pollfd) {
+			struct libusb_pollfd *pollfd = &ipollfd->pollfd;
+			i++;
+			ctx->pollfds[i].fd = pollfd->fd;
+			ctx->pollfds[i].events = pollfd->events;
+		}
+
+		/* reset the flag now that we have the updated list */
+		ctx->event_flags &= ~USBI_EVENT_POLLFDS_MODIFIED;
+
+		/* if no further pending events, clear the event pipe so that we do
+		 * not immediately return from poll */
+		if (!usbi_pending_events(ctx))
+			usbi_clear_event(ctx);
+	}
+	fds = ctx->pollfds;
+	nfds = ctx->pollfds_cnt;
+	usbi_mutex_unlock(&ctx->event_data_lock);
+
+	timeout_ms = (int)(tv->tv_sec * 1000) + (tv->tv_usec / 1000);
+
+	/* round up to next millisecond */
+	if (tv->tv_usec % 1000)
+		timeout_ms++;
+
+redo_poll:
+	usbi_dbg("poll() %d fds with timeout in %dms", nfds, timeout_ms);
+	r = usbi_poll(fds, nfds, timeout_ms);
+	usbi_dbg("poll() returned %d", r);
+	if (r == 0) {
+		r = handle_timeouts(ctx);
+		goto done;
+	}
+	else if (r == -1 && errno == EINTR) {
+		r = LIBUSB_ERROR_INTERRUPTED;
+		goto done;
+	}
+	else if (r < 0) {
+		usbi_err(ctx, "poll failed %d err=%d", r, errno);
+		r = LIBUSB_ERROR_IO;
+		goto done;
+	}
+
+	special_event = 0;
+
+	/* fds[0] is always the event pipe */
+	if (fds[0].revents) {
+		libusb_hotplug_message *message = NULL;
+		struct usbi_transfer *itransfer;
+		int ret = 0;
+
+		usbi_dbg("caught a fish on the event pipe");
+
+		/* take the the event data lock while processing events */
+		usbi_mutex_lock(&ctx->event_data_lock);
+
+		/* check if someone added a new poll fd */
+		if (ctx->event_flags & USBI_EVENT_POLLFDS_MODIFIED)
+			usbi_dbg("someone updated the poll fds");
+
+		if (ctx->event_flags & USBI_EVENT_USER_INTERRUPT) {
+			usbi_dbg("someone purposely interrupted");
+			ctx->event_flags &= ~USBI_EVENT_USER_INTERRUPT;
+		}
+
+		/* check if someone is closing a device */
+		if (ctx->device_close)
+			usbi_dbg("someone is closing a device");
+
+		/* check for any pending hotplug messages */
+		if (!list_empty(&ctx->hotplug_msgs)) {
+			usbi_dbg("hotplug message received");
+			special_event = 1;
+			message = list_first_entry(&ctx->hotplug_msgs, libusb_hotplug_message, list);
+			list_del(&message->list);
+		}
+
+		/* complete any pending transfers */
+		while (ret == 0 && !list_empty(&ctx->completed_transfers)) {
+			itransfer = list_first_entry(&ctx->completed_transfers, struct usbi_transfer, completed_list);
+			list_del(&itransfer->completed_list);
+			usbi_mutex_unlock(&ctx->event_data_lock);
+			ret = usbi_backend->handle_transfer_completion(itransfer);
+			if (ret)
+				usbi_err(ctx, "backend handle_transfer_completion failed with error %d", ret);
+			usbi_mutex_lock(&ctx->event_data_lock);
+		}
+
+		/* if no further pending events, clear the event pipe */
+		if (!usbi_pending_events(ctx))
+			usbi_clear_event(ctx);
+
+		usbi_mutex_unlock(&ctx->event_data_lock);
+
+		/* process the hotplug message, if any */
+		if (message) {
+			usbi_hotplug_match(ctx, message->device, message->event);
+
+			/* the device left, dereference the device */
+			if (LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT == message->event)
+				libusb_unref_device(message->device);
+
+			free(message);
+		}
+
+		if (ret) {
+			/* return error code */
+			r = ret;
+			goto done;
+		}
+
+		if (0 == --r)
+			goto handled;
+	}
+
+#ifdef USBI_TIMERFD_AVAILABLE
+	/* on timerfd configurations, fds[1] is the timerfd */
+	if (usbi_using_timerfd(ctx) && fds[1].revents) {
+		/* timerfd indicates that a timeout has expired */
+		int ret;
+		usbi_dbg("timerfd triggered");
+		special_event = 1;
+
+		ret = handle_timerfd_trigger(ctx);
+		if (ret < 0) {
+			/* return error code */
+			r = ret;
+			goto done;
+		}
+
+		if (0 == --r)
+			goto handled;
+	}
+#endif
+
+	r = usbi_backend->handle_events(ctx, fds + internal_nfds, nfds - internal_nfds, r);
+	if (r)
+		usbi_err(ctx, "backend handle_events failed with error %d", r);
+
+handled:
+	if (r == 0 && special_event) {
+		timeout_ms = 0;
+		goto redo_poll;
+	}
+
+done:
+	usbi_end_event_handling(ctx);
+	return r;
+}
+
+/* returns the smallest of:
+ *  1. timeout of next URB
+ *  2. user-supplied timeout
+ * returns 1 if there is an already-expired timeout, otherwise returns 0
+ * and populates out
+ */
+static int get_next_timeout(libusb_context *ctx, struct timeval *tv,
+	struct timeval *out)
+{
+	struct timeval timeout;
+	int r = libusb_get_next_timeout(ctx, &timeout);
+	if (r) {
+		/* timeout already expired? */
+		if (!timerisset(&timeout))
+			return 1;
+
+		/* choose the smallest of next URB timeout or user specified timeout */
+		if (timercmp(&timeout, tv, <))
+			*out = timeout;
+		else
+			*out = *tv;
+	} else {
+		*out = *tv;
+	}
+	return 0;
+}
+
+/** \ingroup libusb_poll
+ * Handle any pending events.
+ *
+ * libusb determines "pending events" by checking if any timeouts have expired
+ * and by checking the set of file descriptors for activity.
+ *
+ * If a zero timeval is passed, this function will handle any already-pending
+ * events and then immediately return in non-blocking style.
+ *
+ * If a non-zero timeval is passed and no events are currently pending, this
+ * function will block waiting for events to handle up until the specified
+ * timeout. If an event arrives or a signal is raised, this function will
+ * return early.
+ *
+ * If the parameter completed is not NULL then <em>after obtaining the event
+ * handling lock</em> this function will return immediately if the integer
+ * pointed to is not 0. This allows for race free waiting for the completion
+ * of a specific transfer.
+ *
+ * \param ctx the context to operate on, or NULL for the default context
+ * \param tv the maximum time to block waiting for events, or an all zero
+ * timeval struct for non-blocking mode
+ * \param completed pointer to completion integer to check, or NULL
+ * \returns 0 on success, or a LIBUSB_ERROR code on failure
+ * \ref libusb_mtasync
+ */
+int API_EXPORTED libusb_handle_events_timeout_completed(libusb_context *ctx,
+	struct timeval *tv, int *completed)
+{
+	int r;
+	struct timeval poll_timeout;
+
+	USBI_GET_CONTEXT(ctx);
+	r = get_next_timeout(ctx, tv, &poll_timeout);
+	if (r) {
+		/* timeout already expired */
+		return handle_timeouts(ctx);
+	}
+
+retry:
+	if (libusb_try_lock_events(ctx) == 0) {
+		if (completed == NULL || !*completed) {
+			/* we obtained the event lock: do our own event handling */
+			usbi_dbg("doing our own event handling");
+			r = handle_events(ctx, &poll_timeout);
+		}
+		libusb_unlock_events(ctx);
+		return r;
+	}
+
+	/* another thread is doing event handling. wait for thread events that
+	 * notify event completion. */
+	libusb_lock_event_waiters(ctx);
+
+	if (completed && *completed)
+		goto already_done;
+
+	if (!libusb_event_handler_active(ctx)) {
+		/* we hit a race: whoever was event handling earlier finished in the
+		 * time it took us to reach this point. try the cycle again. */
+		libusb_unlock_event_waiters(ctx);
+		usbi_dbg("event handler was active but went away, retrying");
+		goto retry;
+	}
+
+	usbi_dbg("another thread is doing event handling");
+	r = libusb_wait_for_event(ctx, &poll_timeout);
+
+already_done:
+	libusb_unlock_event_waiters(ctx);
+
+	if (r < 0)
+		return r;
+	else if (r == 1)
+		return handle_timeouts(ctx);
+	else
+		return 0;
+}
+
+/** \ingroup libusb_poll
+ * Handle any pending events
+ *
+ * Like libusb_handle_events_timeout_completed(), but without the completed
+ * parameter, calling this function is equivalent to calling
+ * libusb_handle_events_timeout_completed() with a NULL completed parameter.
+ *
+ * This function is kept primarily for backwards compatibility.
+ * All new code should call libusb_handle_events_completed() or
+ * libusb_handle_events_timeout_completed() to avoid race conditions.
+ *
+ * \param ctx the context to operate on, or NULL for the default context
+ * \param tv the maximum time to block waiting for events, or an all zero
+ * timeval struct for non-blocking mode
+ * \returns 0 on success, or a LIBUSB_ERROR code on failure
+ */
+int API_EXPORTED libusb_handle_events_timeout(libusb_context *ctx,
+	struct timeval *tv)
+{
+	return libusb_handle_events_timeout_completed(ctx, tv, NULL);
+}
+
+/** \ingroup libusb_poll
+ * Handle any pending events in blocking mode. There is currently a timeout
+ * hardcoded at 60 seconds but we plan to make it unlimited in future. For
+ * finer control over whether this function is blocking or non-blocking, or
+ * for control over the timeout, use libusb_handle_events_timeout_completed()
+ * instead.
+ *
+ * This function is kept primarily for backwards compatibility.
+ * All new code should call libusb_handle_events_completed() or
+ * libusb_handle_events_timeout_completed() to avoid race conditions.
+ *
+ * \param ctx the context to operate on, or NULL for the default context
+ * \returns 0 on success, or a LIBUSB_ERROR code on failure
+ */
+int API_EXPORTED libusb_handle_events(libusb_context *ctx)
+{
+	struct timeval tv;
+	tv.tv_sec = 60;
+	tv.tv_usec = 0;
+	return libusb_handle_events_timeout_completed(ctx, &tv, NULL);
+}
+
+/** \ingroup libusb_poll
+ * Handle any pending events in blocking mode.
+ *
+ * Like libusb_handle_events(), with the addition of a completed parameter
+ * to allow for race free waiting for the completion of a specific transfer.
+ *
+ * See libusb_handle_events_timeout_completed() for details on the completed
+ * parameter.
+ *
+ * \param ctx the context to operate on, or NULL for the default context
+ * \param completed pointer to completion integer to check, or NULL
+ * \returns 0 on success, or a LIBUSB_ERROR code on failure
+ * \ref libusb_mtasync
+ */
+int API_EXPORTED libusb_handle_events_completed(libusb_context *ctx,
+	int *completed)
+{
+	struct timeval tv;
+	tv.tv_sec = 60;
+	tv.tv_usec = 0;
+	return libusb_handle_events_timeout_completed(ctx, &tv, completed);
+}
+
+/** \ingroup libusb_poll
+ * Handle any pending events by polling file descriptors, without checking if
+ * any other threads are already doing so. Must be called with the event lock
+ * held, see libusb_lock_events().
+ *
+ * This function is designed to be called under the situation where you have
+ * taken the event lock and are calling poll()/select() directly on libusb's
+ * file descriptors (as opposed to using libusb_handle_events() or similar).
+ * You detect events on libusb's descriptors, so you then call this function
+ * with a zero timeout value (while still holding the event lock).
+ *
+ * \param ctx the context to operate on, or NULL for the default context
+ * \param tv the maximum time to block waiting for events, or zero for
+ * non-blocking mode
+ * \returns 0 on success, or a LIBUSB_ERROR code on failure
+ * \ref libusb_mtasync
+ */
+int API_EXPORTED libusb_handle_events_locked(libusb_context *ctx,
+	struct timeval *tv)
+{
+	int r;
+	struct timeval poll_timeout;
+
+	USBI_GET_CONTEXT(ctx);
+	r = get_next_timeout(ctx, tv, &poll_timeout);
+	if (r) {
+		/* timeout already expired */
+		return handle_timeouts(ctx);
+	}
+
+	return handle_events(ctx, &poll_timeout);
+}
+
+/** \ingroup libusb_poll
+ * Determines whether your application must apply special timing considerations
+ * when monitoring libusb's file descriptors.
+ *
+ * This function is only useful for applications which retrieve and poll
+ * libusb's file descriptors in their own main loop (\ref libusb_pollmain).
+ *
+ * Ordinarily, libusb's event handler needs to be called into at specific
+ * moments in time (in addition to times when there is activity on the file
+ * descriptor set). The usual approach is to use libusb_get_next_timeout()
+ * to learn about when the next timeout occurs, and to adjust your
+ * poll()/select() timeout accordingly so that you can make a call into the
+ * library at that time.
+ *
+ * Some platforms supported by libusb do not come with this baggage - any
+ * events relevant to timing will be represented by activity on the file
+ * descriptor set, and libusb_get_next_timeout() will always return 0.
+ * This function allows you to detect whether you are running on such a
+ * platform.
+ *
+ * Since v1.0.5.
+ *
+ * \param ctx the context to operate on, or NULL for the default context
+ * \returns 0 if you must call into libusb at times determined by
+ * libusb_get_next_timeout(), or 1 if all timeout events are handled internally
+ * or through regular activity on the file descriptors.
+ * \ref libusb_pollmain "Polling libusb file descriptors for event handling"
+ */
+int API_EXPORTED libusb_pollfds_handle_timeouts(libusb_context *ctx)
+{
+#if defined(USBI_TIMERFD_AVAILABLE)
+	USBI_GET_CONTEXT(ctx);
+	return usbi_using_timerfd(ctx);
+#else
+	UNUSED(ctx);
+	return 0;
+#endif
+}
+
+/** \ingroup libusb_poll
+ * Determine the next internal timeout that libusb needs to handle. You only
+ * need to use this function if you are calling poll() or select() or similar
+ * on libusb's file descriptors yourself - you do not need to use it if you
+ * are calling libusb_handle_events() or a variant directly.
+ *
+ * You should call this function in your main loop in order to determine how
+ * long to wait for select() or poll() to return results. libusb needs to be
+ * called into at this timeout, so you should use it as an upper bound on
+ * your select() or poll() call.
+ *
+ * When the timeout has expired, call into libusb_handle_events_timeout()
+ * (perhaps in non-blocking mode) so that libusb can handle the timeout.
+ *
+ * This function may return 1 (success) and an all-zero timeval. If this is
+ * the case, it indicates that libusb has a timeout that has already expired
+ * so you should call libusb_handle_events_timeout() or similar immediately.
+ * A return code of 0 indicates that there are no pending timeouts.
+ *
+ * On some platforms, this function will always returns 0 (no pending
+ * timeouts). See \ref polltime.
+ *
+ * \param ctx the context to operate on, or NULL for the default context
+ * \param tv output location for a relative time against the current
+ * clock in which libusb must be called into in order to process timeout events
+ * \returns 0 if there are no pending timeouts, 1 if a timeout was returned,
+ * or LIBUSB_ERROR_OTHER on failure
+ */
+int API_EXPORTED libusb_get_next_timeout(libusb_context *ctx,
+	struct timeval *tv)
+{
+	struct usbi_transfer *transfer;
+	struct timespec cur_ts;
+	struct timeval cur_tv;
+	struct timeval next_timeout = { 0, 0 };
+	int r;
+
+	USBI_GET_CONTEXT(ctx);
+	if (usbi_using_timerfd(ctx))
+		return 0;
+
+	usbi_mutex_lock(&ctx->flying_transfers_lock);
+	if (list_empty(&ctx->flying_transfers)) {
+		usbi_mutex_unlock(&ctx->flying_transfers_lock);
+		usbi_dbg("no URBs, no timeout!");
+		return 0;
+	}
+
+	/* find next transfer which hasn't already been processed as timed out */
+	list_for_each_entry(transfer, &ctx->flying_transfers, list, struct usbi_transfer) {
+		if (transfer->timeout_flags & (USBI_TRANSFER_TIMEOUT_HANDLED | USBI_TRANSFER_OS_HANDLES_TIMEOUT))
+			continue;
+
+		/* if we've reached transfers of infinte timeout, we're done looking */
+		if (!timerisset(&transfer->timeout))
+			break;
+
+		next_timeout = transfer->timeout;
+		break;
+	}
+	usbi_mutex_unlock(&ctx->flying_transfers_lock);
+
+	if (!timerisset(&next_timeout)) {
+		usbi_dbg("no URB with timeout or all handled by OS; no timeout!");
+		return 0;
+	}
+
+	r = usbi_backend->clock_gettime(USBI_CLOCK_MONOTONIC, &cur_ts);
+	if (r < 0) {
+		usbi_err(ctx, "failed to read monotonic clock, errno=%d", errno);
+		return 0;
+	}
+	TIMESPEC_TO_TIMEVAL(&cur_tv, &cur_ts);
+
+	if (!timercmp(&cur_tv, &next_timeout, <)) {
+		usbi_dbg("first timeout already expired");
+		timerclear(tv);
+	} else {
+		timersub(&next_timeout, &cur_tv, tv);
+		usbi_dbg("next timeout in %d.%06ds", tv->tv_sec, tv->tv_usec);
+	}
+
+	return 1;
+}
+
+/** \ingroup libusb_poll
+ * Register notification functions for file descriptor additions/removals.
+ * These functions will be invoked for every new or removed file descriptor
+ * that libusb uses as an event source.
+ *
+ * To remove notifiers, pass NULL values for the function pointers.
+ *
+ * Note that file descriptors may have been added even before you register
+ * these notifiers (e.g. at libusb_init() time).
+ *
+ * Additionally, note that the removal notifier may be called during
+ * libusb_exit() (e.g. when it is closing file descriptors that were opened
+ * and added to the poll set at libusb_init() time). If you don't want this,
+ * remove the notifiers immediately before calling libusb_exit().
+ *
+ * \param ctx the context to operate on, or NULL for the default context
+ * \param added_cb pointer to function for addition notifications
+ * \param removed_cb pointer to function for removal notifications
+ * \param user_data User data to be passed back to callbacks (useful for
+ * passing context information)
+ */
+void API_EXPORTED libusb_set_pollfd_notifiers(libusb_context *ctx,
+	libusb_pollfd_added_cb added_cb, libusb_pollfd_removed_cb removed_cb,
+	void *user_data)
+{
+	USBI_GET_CONTEXT(ctx);
+	ctx->fd_added_cb = added_cb;
+	ctx->fd_removed_cb = removed_cb;
+	ctx->fd_cb_user_data = user_data;
+}
+
+/*
+ * Interrupt the iteration of the event handling thread, so that it picks
+ * up the fd change. Callers of this function must hold the event_data_lock.
+ */
+static void usbi_fd_notification(struct libusb_context *ctx)
+{
+	int pending_events;
+
+	/* Record that there is a new poll fd.
+	 * Only signal an event if there are no prior pending events. */
+	pending_events = usbi_pending_events(ctx);
+	ctx->event_flags |= USBI_EVENT_POLLFDS_MODIFIED;
+	if (!pending_events)
+		usbi_signal_event(ctx);
+}
+
+/* Add a file descriptor to the list of file descriptors to be monitored.
+ * events should be specified as a bitmask of events passed to poll(), e.g.
+ * POLLIN and/or POLLOUT. */
+int usbi_add_pollfd(struct libusb_context *ctx, int fd, short events)
+{
+	struct usbi_pollfd *ipollfd = malloc(sizeof(*ipollfd));
+	if (!ipollfd)
+		return LIBUSB_ERROR_NO_MEM;
+
+	usbi_dbg("add fd %d events %d", fd, events);
+	ipollfd->pollfd.fd = fd;
+	ipollfd->pollfd.events = events;
+	usbi_mutex_lock(&ctx->event_data_lock);
+	list_add_tail(&ipollfd->list, &ctx->ipollfds);
+	ctx->pollfds_cnt++;
+	usbi_fd_notification(ctx);
+	usbi_mutex_unlock(&ctx->event_data_lock);
+
+	if (ctx->fd_added_cb)
+		ctx->fd_added_cb(fd, events, ctx->fd_cb_user_data);
+	return 0;
+}
+
+/* Remove a file descriptor from the list of file descriptors to be polled. */
+void usbi_remove_pollfd(struct libusb_context *ctx, int fd)
+{
+	struct usbi_pollfd *ipollfd;
+	int found = 0;
+
+	usbi_dbg("remove fd %d", fd);
+	usbi_mutex_lock(&ctx->event_data_lock);
+	list_for_each_entry(ipollfd, &ctx->ipollfds, list, struct usbi_pollfd)
+		if (ipollfd->pollfd.fd == fd) {
+			found = 1;
+			break;
+		}
+
+	if (!found) {
+		usbi_dbg("couldn't find fd %d to remove", fd);
+		usbi_mutex_unlock(&ctx->event_data_lock);
+		return;
+	}
+
+	list_del(&ipollfd->list);
+	ctx->pollfds_cnt--;
+	usbi_fd_notification(ctx);
+	usbi_mutex_unlock(&ctx->event_data_lock);
+	free(ipollfd);
+	if (ctx->fd_removed_cb)
+		ctx->fd_removed_cb(fd, ctx->fd_cb_user_data);
+}
+
+/** \ingroup libusb_poll
+ * Retrieve a list of file descriptors that should be polled by your main loop
+ * as libusb event sources.
+ *
+ * The returned list is NULL-terminated and should be freed with libusb_free_pollfds()
+ * when done. The actual list contents must not be touched.
+ *
+ * As file descriptors are a Unix-specific concept, this function is not
+ * available on Windows and will always return NULL.
+ *
+ * \param ctx the context to operate on, or NULL for the default context
+ * \returns a NULL-terminated list of libusb_pollfd structures
+ * \returns NULL on error
+ * \returns NULL on platforms where the functionality is not available
+ */
+DEFAULT_VISIBILITY
+const struct libusb_pollfd ** LIBUSB_CALL libusb_get_pollfds(
+	libusb_context *ctx)
+{
+#ifndef OS_WINDOWS
+	struct libusb_pollfd **ret = NULL;
+	struct usbi_pollfd *ipollfd;
+	size_t i = 0;
+	USBI_GET_CONTEXT(ctx);
+
+	usbi_mutex_lock(&ctx->event_data_lock);
+
+	ret = calloc(ctx->pollfds_cnt + 1, sizeof(struct libusb_pollfd *));
+	if (!ret)
+		goto out;
+
+	list_for_each_entry(ipollfd, &ctx->ipollfds, list, struct usbi_pollfd)
+		ret[i++] = (struct libusb_pollfd *) ipollfd;
+	ret[ctx->pollfds_cnt] = NULL;
+
+out:
+	usbi_mutex_unlock(&ctx->event_data_lock);
+	return (const struct libusb_pollfd **) ret;
+#else
+	usbi_err(ctx, "external polling of libusb's internal descriptors "\
+		"is not yet supported on Windows platforms");
+	return NULL;
+#endif
+}
+
+/** \ingroup libusb_poll
+ * Free a list of libusb_pollfd structures. This should be called for all
+ * pollfd lists allocated with libusb_get_pollfds().
+ *
+ * Since version 1.0.20, \ref LIBUSB_API_VERSION >= 0x01000104
+ *
+ * It is legal to call this function with a NULL pollfd list. In this case,
+ * the function will simply return safely.
+ *
+ * \param pollfds the list of libusb_pollfd structures to free
+ */
+void API_EXPORTED libusb_free_pollfds(const struct libusb_pollfd **pollfds)
+{
+	if (!pollfds)
+		return;
+
+	free((void *)pollfds);
+}
+
+/* Backends may call this from handle_events to report disconnection of a
+ * device. This function ensures transfers get cancelled appropriately.
+ * Callers of this function must hold the events_lock.
+ */
+void usbi_handle_disconnect(struct libusb_device_handle *dev_handle)
+{
+	struct usbi_transfer *cur;
+	struct usbi_transfer *to_cancel;
+
+	usbi_dbg("device %d.%d",
+		dev_handle->dev->bus_number, dev_handle->dev->device_address);
+
+	/* terminate all pending transfers with the LIBUSB_TRANSFER_NO_DEVICE
+	 * status code.
+	 *
+	 * when we find a transfer for this device on the list, there are two
+	 * possible scenarios:
+	 * 1. the transfer is currently in-flight, in which case we terminate the
+	 *    transfer here
+	 * 2. the transfer has been added to the flying transfer list by
+	 *    libusb_submit_transfer, has failed to submit and
+	 *    libusb_submit_transfer is waiting for us to release the
+	 *    flying_transfers_lock to remove it, so we ignore it
+	 */
+
+	while (1) {
+		to_cancel = NULL;
+		usbi_mutex_lock(&HANDLE_CTX(dev_handle)->flying_transfers_lock);
+		list_for_each_entry(cur, &HANDLE_CTX(dev_handle)->flying_transfers, list, struct usbi_transfer)
+			if (USBI_TRANSFER_TO_LIBUSB_TRANSFER(cur)->dev_handle == dev_handle) {
+				usbi_mutex_lock(&cur->lock);
+				if (cur->state_flags & USBI_TRANSFER_IN_FLIGHT)
+					to_cancel = cur;
+				usbi_mutex_unlock(&cur->lock);
+
+				if (to_cancel)
+					break;
+			}
+		usbi_mutex_unlock(&HANDLE_CTX(dev_handle)->flying_transfers_lock);
+
+		if (!to_cancel)
+			break;
+
+		usbi_dbg("cancelling transfer %p from disconnect",
+			 USBI_TRANSFER_TO_LIBUSB_TRANSFER(to_cancel));
+
+		usbi_mutex_lock(&to_cancel->lock);
+		usbi_backend->clear_transfer_priv(to_cancel);
+		usbi_mutex_unlock(&to_cancel->lock);
+		usbi_handle_transfer_completion(to_cancel, LIBUSB_TRANSFER_NO_DEVICE);
+	}
+
+}
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/libusb.h b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/libusb.h
new file mode 100644
index 000000000..c562690f9
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/libusb.h
@@ -0,0 +1,2008 @@
+/*
+ * Public libusb header file
+ * Copyright © 2001 Johannes Erdfelt <johannes@erdfelt.com>
+ * Copyright © 2007-2008 Daniel Drake <dsd@gentoo.org>
+ * Copyright © 2012 Pete Batard <pete@akeo.ie>
+ * Copyright © 2012 Nathan Hjelm <hjelmn@cs.unm.edu>
+ * For more information, please visit: http://libusb.info
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef LIBUSB_H
+#define LIBUSB_H
+
+#ifdef _MSC_VER
+/* on MS environments, the inline keyword is available in C++ only */
+#if !defined(__cplusplus)
+#define inline __inline
+#endif
+/* ssize_t is also not available (copy/paste from MinGW) */
+#ifndef _SSIZE_T_DEFINED
+#define _SSIZE_T_DEFINED
+#undef ssize_t
+#ifdef _WIN64
+  typedef __int64 ssize_t;
+#else
+  typedef int ssize_t;
+#endif /* _WIN64 */
+#endif /* _SSIZE_T_DEFINED */
+#endif /* _MSC_VER */
+
+/* stdint.h is not available on older MSVC */
+#if defined(_MSC_VER) && (_MSC_VER < 1600) && (!defined(_STDINT)) && (!defined(_STDINT_H))
+typedef unsigned __int8   uint8_t;
+typedef unsigned __int16  uint16_t;
+typedef unsigned __int32  uint32_t;
+#else
+#include <stdint.h>
+#endif
+
+#if !defined(_WIN32_WCE)
+#include <sys/types.h>
+#endif
+
+#if defined(__linux) || defined(__APPLE__) || defined(__CYGWIN__) || defined(__HAIKU__)
+#include <sys/time.h>
+#endif
+
+#include <time.h>
+#include <limits.h>
+
+/* 'interface' might be defined as a macro on Windows, so we need to
+ * undefine it so as not to break the current libusb API, because
+ * libusb_config_descriptor has an 'interface' member
+ * As this can be problematic if you include windows.h after libusb.h
+ * in your sources, we force windows.h to be included first. */
+#if defined(_WIN32) || defined(__CYGWIN__) || defined(_WIN32_WCE)
+#include <windows.h>
+#if defined(interface)
+#undef interface
+#endif
+#if !defined(__CYGWIN__)
+#include <winsock.h>
+#endif
+#endif
+
+#if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 5)
+#define LIBUSB_DEPRECATED_FOR(f) \
+  __attribute__((deprecated("Use " #f " instead")))
+#else
+#define LIBUSB_DEPRECATED_FOR(f)
+#endif /* __GNUC__ */
+
+/** \def LIBUSB_CALL
+ * \ingroup libusb_misc
+ * libusb's Windows calling convention.
+ *
+ * Under Windows, the selection of available compilers and configurations
+ * means that, unlike other platforms, there is not <em>one true calling
+ * convention</em> (calling convention: the manner in which parameters are
+ * passed to functions in the generated assembly code).
+ *
+ * Matching the Windows API itself, libusb uses the WINAPI convention (which
+ * translates to the <tt>stdcall</tt> convention) and guarantees that the
+ * library is compiled in this way. The public header file also includes
+ * appropriate annotations so that your own software will use the right
+ * convention, even if another convention is being used by default within
+ * your codebase.
+ *
+ * The one consideration that you must apply in your software is to mark
+ * all functions which you use as libusb callbacks with this LIBUSB_CALL
+ * annotation, so that they too get compiled for the correct calling
+ * convention.
+ *
+ * On non-Windows operating systems, this macro is defined as nothing. This
+ * means that you can apply it to your code without worrying about
+ * cross-platform compatibility.
+ */
+/* LIBUSB_CALL must be defined on both definition and declaration of libusb
+ * functions. You'd think that declaration would be enough, but cygwin will
+ * complain about conflicting types unless both are marked this way.
+ * The placement of this macro is important too; it must appear after the
+ * return type, before the function name. See internal documentation for
+ * API_EXPORTED.
+ */
+#if defined(_WIN32) || defined(__CYGWIN__) || defined(_WIN32_WCE)
+#define LIBUSB_CALL WINAPI
+#else
+#define LIBUSB_CALL
+#endif
+
+/** \def LIBUSB_API_VERSION
+ * \ingroup libusb_misc
+ * libusb's API version.
+ *
+ * Since version 1.0.13, to help with feature detection, libusb defines
+ * a LIBUSB_API_VERSION macro that gets increased every time there is a
+ * significant change to the API, such as the introduction of a new call,
+ * the definition of a new macro/enum member, or any other element that
+ * libusb applications may want to detect at compilation time.
+ *
+ * The macro is typically used in an application as follows:
+ * \code
+ * #if defined(LIBUSB_API_VERSION) && (LIBUSB_API_VERSION >= 0x01001234)
+ * // Use one of the newer features from the libusb API
+ * #endif
+ * \endcode
+ *
+ * Internally, LIBUSB_API_VERSION is defined as follows:
+ * (libusb major << 24) | (libusb minor << 16) | (16 bit incremental)
+ */
+#define LIBUSB_API_VERSION 0x01000105
+
+/* The following is kept for compatibility, but will be deprecated in the future */
+#define LIBUSBX_API_VERSION LIBUSB_API_VERSION
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * \ingroup libusb_misc
+ * Convert a 16-bit value from host-endian to little-endian format. On
+ * little endian systems, this function does nothing. On big endian systems,
+ * the bytes are swapped.
+ * \param x the host-endian value to convert
+ * \returns the value in little-endian byte order
+ */
+static inline uint16_t libusb_cpu_to_le16(const uint16_t x)
+{
+	union {
+		uint8_t  b8[2];
+		uint16_t b16;
+	} _tmp;
+	_tmp.b8[1] = (uint8_t) (x >> 8);
+	_tmp.b8[0] = (uint8_t) (x & 0xff);
+	return _tmp.b16;
+}
+
+/** \def libusb_le16_to_cpu
+ * \ingroup libusb_misc
+ * Convert a 16-bit value from little-endian to host-endian format. On
+ * little endian systems, this function does nothing. On big endian systems,
+ * the bytes are swapped.
+ * \param x the little-endian value to convert
+ * \returns the value in host-endian byte order
+ */
+#define libusb_le16_to_cpu libusb_cpu_to_le16
+
+/* standard USB stuff */
+
+/** \ingroup libusb_desc
+ * Device and/or Interface Class codes */
+enum libusb_class_code {
+	/** In the context of a \ref libusb_device_descriptor "device descriptor",
+	 * this bDeviceClass value indicates that each interface specifies its
+	 * own class information and all interfaces operate independently.
+	 */
+	LIBUSB_CLASS_PER_INTERFACE = 0,
+
+	/** Audio class */
+	LIBUSB_CLASS_AUDIO = 1,
+
+	/** Communications class */
+	LIBUSB_CLASS_COMM = 2,
+
+	/** Human Interface Device class */
+	LIBUSB_CLASS_HID = 3,
+
+	/** Physical */
+	LIBUSB_CLASS_PHYSICAL = 5,
+
+	/** Printer class */
+	LIBUSB_CLASS_PRINTER = 7,
+
+	/** Image class */
+	LIBUSB_CLASS_PTP = 6, /* legacy name from libusb-0.1 usb.h */
+	LIBUSB_CLASS_IMAGE = 6,
+
+	/** Mass storage class */
+	LIBUSB_CLASS_MASS_STORAGE = 8,
+
+	/** Hub class */
+	LIBUSB_CLASS_HUB = 9,
+
+	/** Data class */
+	LIBUSB_CLASS_DATA = 10,
+
+	/** Smart Card */
+	LIBUSB_CLASS_SMART_CARD = 0x0b,
+
+	/** Content Security */
+	LIBUSB_CLASS_CONTENT_SECURITY = 0x0d,
+
+	/** Video */
+	LIBUSB_CLASS_VIDEO = 0x0e,
+
+	/** Personal Healthcare */
+	LIBUSB_CLASS_PERSONAL_HEALTHCARE = 0x0f,
+
+	/** Diagnostic Device */
+	LIBUSB_CLASS_DIAGNOSTIC_DEVICE = 0xdc,
+
+	/** Wireless class */
+	LIBUSB_CLASS_WIRELESS = 0xe0,
+
+	/** Application class */
+	LIBUSB_CLASS_APPLICATION = 0xfe,
+
+	/** Class is vendor-specific */
+	LIBUSB_CLASS_VENDOR_SPEC = 0xff
+};
+
+/** \ingroup libusb_desc
+ * Descriptor types as defined by the USB specification. */
+enum libusb_descriptor_type {
+	/** Device descriptor. See libusb_device_descriptor. */
+	LIBUSB_DT_DEVICE = 0x01,
+
+	/** Configuration descriptor. See libusb_config_descriptor. */
+	LIBUSB_DT_CONFIG = 0x02,
+
+	/** String descriptor */
+	LIBUSB_DT_STRING = 0x03,
+
+	/** Interface descriptor. See libusb_interface_descriptor. */
+	LIBUSB_DT_INTERFACE = 0x04,
+
+	/** Endpoint descriptor. See libusb_endpoint_descriptor. */
+	LIBUSB_DT_ENDPOINT = 0x05,
+
+	/** BOS descriptor */
+	LIBUSB_DT_BOS = 0x0f,
+
+	/** Device Capability descriptor */
+	LIBUSB_DT_DEVICE_CAPABILITY = 0x10,
+
+	/** HID descriptor */
+	LIBUSB_DT_HID = 0x21,
+
+	/** HID report descriptor */
+	LIBUSB_DT_REPORT = 0x22,
+
+	/** Physical descriptor */
+	LIBUSB_DT_PHYSICAL = 0x23,
+
+	/** Hub descriptor */
+	LIBUSB_DT_HUB = 0x29,
+
+	/** SuperSpeed Hub descriptor */
+	LIBUSB_DT_SUPERSPEED_HUB = 0x2a,
+
+	/** SuperSpeed Endpoint Companion descriptor */
+	LIBUSB_DT_SS_ENDPOINT_COMPANION = 0x30
+};
+
+/* Descriptor sizes per descriptor type */
+#define LIBUSB_DT_DEVICE_SIZE			18
+#define LIBUSB_DT_CONFIG_SIZE			9
+#define LIBUSB_DT_INTERFACE_SIZE		9
+#define LIBUSB_DT_ENDPOINT_SIZE			7
+#define LIBUSB_DT_ENDPOINT_AUDIO_SIZE		9	/* Audio extension */
+#define LIBUSB_DT_HUB_NONVAR_SIZE		7
+#define LIBUSB_DT_SS_ENDPOINT_COMPANION_SIZE	6
+#define LIBUSB_DT_BOS_SIZE			5
+#define LIBUSB_DT_DEVICE_CAPABILITY_SIZE	3
+
+/* BOS descriptor sizes */
+#define LIBUSB_BT_USB_2_0_EXTENSION_SIZE	7
+#define LIBUSB_BT_SS_USB_DEVICE_CAPABILITY_SIZE	10
+#define LIBUSB_BT_CONTAINER_ID_SIZE		20
+
+/* We unwrap the BOS => define its max size */
+#define LIBUSB_DT_BOS_MAX_SIZE		((LIBUSB_DT_BOS_SIZE)     +\
+					(LIBUSB_BT_USB_2_0_EXTENSION_SIZE)       +\
+					(LIBUSB_BT_SS_USB_DEVICE_CAPABILITY_SIZE) +\
+					(LIBUSB_BT_CONTAINER_ID_SIZE))
+
+#define LIBUSB_ENDPOINT_ADDRESS_MASK	0x0f    /* in bEndpointAddress */
+#define LIBUSB_ENDPOINT_DIR_MASK		0x80
+
+/** \ingroup libusb_desc
+ * Endpoint direction. Values for bit 7 of the
+ * \ref libusb_endpoint_descriptor::bEndpointAddress "endpoint address" scheme.
+ */
+enum libusb_endpoint_direction {
+	/** In: device-to-host */
+	LIBUSB_ENDPOINT_IN = 0x80,
+
+	/** Out: host-to-device */
+	LIBUSB_ENDPOINT_OUT = 0x00
+};
+
+#define LIBUSB_TRANSFER_TYPE_MASK			0x03    /* in bmAttributes */
+
+/** \ingroup libusb_desc
+ * Endpoint transfer type. Values for bits 0:1 of the
+ * \ref libusb_endpoint_descriptor::bmAttributes "endpoint attributes" field.
+ */
+enum libusb_transfer_type {
+	/** Control endpoint */
+	LIBUSB_TRANSFER_TYPE_CONTROL = 0,
+
+	/** Isochronous endpoint */
+	LIBUSB_TRANSFER_TYPE_ISOCHRONOUS = 1,
+
+	/** Bulk endpoint */
+	LIBUSB_TRANSFER_TYPE_BULK = 2,
+
+	/** Interrupt endpoint */
+	LIBUSB_TRANSFER_TYPE_INTERRUPT = 3,
+
+	/** Stream endpoint */
+	LIBUSB_TRANSFER_TYPE_BULK_STREAM = 4,
+};
+
+/** \ingroup libusb_misc
+ * Standard requests, as defined in table 9-5 of the USB 3.0 specifications */
+enum libusb_standard_request {
+	/** Request status of the specific recipient */
+	LIBUSB_REQUEST_GET_STATUS = 0x00,
+
+	/** Clear or disable a specific feature */
+	LIBUSB_REQUEST_CLEAR_FEATURE = 0x01,
+
+	/* 0x02 is reserved */
+
+	/** Set or enable a specific feature */
+	LIBUSB_REQUEST_SET_FEATURE = 0x03,
+
+	/* 0x04 is reserved */
+
+	/** Set device address for all future accesses */
+	LIBUSB_REQUEST_SET_ADDRESS = 0x05,
+
+	/** Get the specified descriptor */
+	LIBUSB_REQUEST_GET_DESCRIPTOR = 0x06,
+
+	/** Used to update existing descriptors or add new descriptors */
+	LIBUSB_REQUEST_SET_DESCRIPTOR = 0x07,
+
+	/** Get the current device configuration value */
+	LIBUSB_REQUEST_GET_CONFIGURATION = 0x08,
+
+	/** Set device configuration */
+	LIBUSB_REQUEST_SET_CONFIGURATION = 0x09,
+
+	/** Return the selected alternate setting for the specified interface */
+	LIBUSB_REQUEST_GET_INTERFACE = 0x0A,
+
+	/** Select an alternate interface for the specified interface */
+	LIBUSB_REQUEST_SET_INTERFACE = 0x0B,
+
+	/** Set then report an endpoint's synchronization frame */
+	LIBUSB_REQUEST_SYNCH_FRAME = 0x0C,
+
+	/** Sets both the U1 and U2 Exit Latency */
+	LIBUSB_REQUEST_SET_SEL = 0x30,
+
+	/** Delay from the time a host transmits a packet to the time it is
+	  * received by the device. */
+	LIBUSB_SET_ISOCH_DELAY = 0x31,
+};
+
+/** \ingroup libusb_misc
+ * Request type bits of the
+ * \ref libusb_control_setup::bmRequestType "bmRequestType" field in control
+ * transfers. */
+enum libusb_request_type {
+	/** Standard */
+	LIBUSB_REQUEST_TYPE_STANDARD = (0x00 << 5),
+
+	/** Class */
+	LIBUSB_REQUEST_TYPE_CLASS = (0x01 << 5),
+
+	/** Vendor */
+	LIBUSB_REQUEST_TYPE_VENDOR = (0x02 << 5),
+
+	/** Reserved */
+	LIBUSB_REQUEST_TYPE_RESERVED = (0x03 << 5)
+};
+
+/** \ingroup libusb_misc
+ * Recipient bits of the
+ * \ref libusb_control_setup::bmRequestType "bmRequestType" field in control
+ * transfers. Values 4 through 31 are reserved. */
+enum libusb_request_recipient {
+	/** Device */
+	LIBUSB_RECIPIENT_DEVICE = 0x00,
+
+	/** Interface */
+	LIBUSB_RECIPIENT_INTERFACE = 0x01,
+
+	/** Endpoint */
+	LIBUSB_RECIPIENT_ENDPOINT = 0x02,
+
+	/** Other */
+	LIBUSB_RECIPIENT_OTHER = 0x03,
+};
+
+#define LIBUSB_ISO_SYNC_TYPE_MASK		0x0C
+
+/** \ingroup libusb_desc
+ * Synchronization type for isochronous endpoints. Values for bits 2:3 of the
+ * \ref libusb_endpoint_descriptor::bmAttributes "bmAttributes" field in
+ * libusb_endpoint_descriptor.
+ */
+enum libusb_iso_sync_type {
+	/** No synchronization */
+	LIBUSB_ISO_SYNC_TYPE_NONE = 0,
+
+	/** Asynchronous */
+	LIBUSB_ISO_SYNC_TYPE_ASYNC = 1,
+
+	/** Adaptive */
+	LIBUSB_ISO_SYNC_TYPE_ADAPTIVE = 2,
+
+	/** Synchronous */
+	LIBUSB_ISO_SYNC_TYPE_SYNC = 3
+};
+
+#define LIBUSB_ISO_USAGE_TYPE_MASK 0x30
+
+/** \ingroup libusb_desc
+ * Usage type for isochronous endpoints. Values for bits 4:5 of the
+ * \ref libusb_endpoint_descriptor::bmAttributes "bmAttributes" field in
+ * libusb_endpoint_descriptor.
+ */
+enum libusb_iso_usage_type {
+	/** Data endpoint */
+	LIBUSB_ISO_USAGE_TYPE_DATA = 0,
+
+	/** Feedback endpoint */
+	LIBUSB_ISO_USAGE_TYPE_FEEDBACK = 1,
+
+	/** Implicit feedback Data endpoint */
+	LIBUSB_ISO_USAGE_TYPE_IMPLICIT = 2,
+};
+
+/** \ingroup libusb_desc
+ * A structure representing the standard USB device descriptor. This
+ * descriptor is documented in section 9.6.1 of the USB 3.0 specification.
+ * All multiple-byte fields are represented in host-endian format.
+ */
+struct libusb_device_descriptor {
+	/** Size of this descriptor (in bytes) */
+	uint8_t  bLength;
+
+	/** Descriptor type. Will have value
+	 * \ref libusb_descriptor_type::LIBUSB_DT_DEVICE LIBUSB_DT_DEVICE in this
+	 * context. */
+	uint8_t  bDescriptorType;
+
+	/** USB specification release number in binary-coded decimal. A value of
+	 * 0x0200 indicates USB 2.0, 0x0110 indicates USB 1.1, etc. */
+	uint16_t bcdUSB;
+
+	/** USB-IF class code for the device. See \ref libusb_class_code. */
+	uint8_t  bDeviceClass;
+
+	/** USB-IF subclass code for the device, qualified by the bDeviceClass
+	 * value */
+	uint8_t  bDeviceSubClass;
+
+	/** USB-IF protocol code for the device, qualified by the bDeviceClass and
+	 * bDeviceSubClass values */
+	uint8_t  bDeviceProtocol;
+
+	/** Maximum packet size for endpoint 0 */
+	uint8_t  bMaxPacketSize0;
+
+	/** USB-IF vendor ID */
+	uint16_t idVendor;
+
+	/** USB-IF product ID */
+	uint16_t idProduct;
+
+	/** Device release number in binary-coded decimal */
+	uint16_t bcdDevice;
+
+	/** Index of string descriptor describing manufacturer */
+	uint8_t  iManufacturer;
+
+	/** Index of string descriptor describing product */
+	uint8_t  iProduct;
+
+	/** Index of string descriptor containing device serial number */
+	uint8_t  iSerialNumber;
+
+	/** Number of possible configurations */
+	uint8_t  bNumConfigurations;
+};
+
+/** \ingroup libusb_desc
+ * A structure representing the standard USB endpoint descriptor. This
+ * descriptor is documented in section 9.6.6 of the USB 3.0 specification.
+ * All multiple-byte fields are represented in host-endian format.
+ */
+struct libusb_endpoint_descriptor {
+	/** Size of this descriptor (in bytes) */
+	uint8_t  bLength;
+
+	/** Descriptor type. Will have value
+	 * \ref libusb_descriptor_type::LIBUSB_DT_ENDPOINT LIBUSB_DT_ENDPOINT in
+	 * this context. */
+	uint8_t  bDescriptorType;
+
+	/** The address of the endpoint described by this descriptor. Bits 0:3 are
+	 * the endpoint number. Bits 4:6 are reserved. Bit 7 indicates direction,
+	 * see \ref libusb_endpoint_direction.
+	 */
+	uint8_t  bEndpointAddress;
+
+	/** Attributes which apply to the endpoint when it is configured using
+	 * the bConfigurationValue. Bits 0:1 determine the transfer type and
+	 * correspond to \ref libusb_transfer_type. Bits 2:3 are only used for
+	 * isochronous endpoints and correspond to \ref libusb_iso_sync_type.
+	 * Bits 4:5 are also only used for isochronous endpoints and correspond to
+	 * \ref libusb_iso_usage_type. Bits 6:7 are reserved.
+	 */
+	uint8_t  bmAttributes;
+
+	/** Maximum packet size this endpoint is capable of sending/receiving. */
+	uint16_t wMaxPacketSize;
+
+	/** Interval for polling endpoint for data transfers. */
+	uint8_t  bInterval;
+
+	/** For audio devices only: the rate at which synchronization feedback
+	 * is provided. */
+	uint8_t  bRefresh;
+
+	/** For audio devices only: the address if the synch endpoint */
+	uint8_t  bSynchAddress;
+
+	/** Extra descriptors. If libusb encounters unknown endpoint descriptors,
+	 * it will store them here, should you wish to parse them. */
+	const unsigned char *extra;
+
+	/** Length of the extra descriptors, in bytes. */
+	int extra_length;
+};
+
+/** \ingroup libusb_desc
+ * A structure representing the standard USB interface descriptor. This
+ * descriptor is documented in section 9.6.5 of the USB 3.0 specification.
+ * All multiple-byte fields are represented in host-endian format.
+ */
+struct libusb_interface_descriptor {
+	/** Size of this descriptor (in bytes) */
+	uint8_t  bLength;
+
+	/** Descriptor type. Will have value
+	 * \ref libusb_descriptor_type::LIBUSB_DT_INTERFACE LIBUSB_DT_INTERFACE
+	 * in this context. */
+	uint8_t  bDescriptorType;
+
+	/** Number of this interface */
+	uint8_t  bInterfaceNumber;
+
+	/** Value used to select this alternate setting for this interface */
+	uint8_t  bAlternateSetting;
+
+	/** Number of endpoints used by this interface (excluding the control
+	 * endpoint). */
+	uint8_t  bNumEndpoints;
+
+	/** USB-IF class code for this interface. See \ref libusb_class_code. */
+	uint8_t  bInterfaceClass;
+
+	/** USB-IF subclass code for this interface, qualified by the
+	 * bInterfaceClass value */
+	uint8_t  bInterfaceSubClass;
+
+	/** USB-IF protocol code for this interface, qualified by the
+	 * bInterfaceClass and bInterfaceSubClass values */
+	uint8_t  bInterfaceProtocol;
+
+	/** Index of string descriptor describing this interface */
+	uint8_t  iInterface;
+
+	/** Array of endpoint descriptors. This length of this array is determined
+	 * by the bNumEndpoints field. */
+	const struct libusb_endpoint_descriptor *endpoint;
+
+	/** Extra descriptors. If libusb encounters unknown interface descriptors,
+	 * it will store them here, should you wish to parse them. */
+	const unsigned char *extra;
+
+	/** Length of the extra descriptors, in bytes. */
+	int extra_length;
+};
+
+/** \ingroup libusb_desc
+ * A collection of alternate settings for a particular USB interface.
+ */
+struct libusb_interface {
+	/** Array of interface descriptors. The length of this array is determined
+	 * by the num_altsetting field. */
+	const struct libusb_interface_descriptor *altsetting;
+
+	/** The number of alternate settings that belong to this interface */
+	int num_altsetting;
+};
+
+/** \ingroup libusb_desc
+ * A structure representing the standard USB configuration descriptor. This
+ * descriptor is documented in section 9.6.3 of the USB 3.0 specification.
+ * All multiple-byte fields are represented in host-endian format.
+ */
+struct libusb_config_descriptor {
+	/** Size of this descriptor (in bytes) */
+	uint8_t  bLength;
+
+	/** Descriptor type. Will have value
+	 * \ref libusb_descriptor_type::LIBUSB_DT_CONFIG LIBUSB_DT_CONFIG
+	 * in this context. */
+	uint8_t  bDescriptorType;
+
+	/** Total length of data returned for this configuration */
+	uint16_t wTotalLength;
+
+	/** Number of interfaces supported by this configuration */
+	uint8_t  bNumInterfaces;
+
+	/** Identifier value for this configuration */
+	uint8_t  bConfigurationValue;
+
+	/** Index of string descriptor describing this configuration */
+	uint8_t  iConfiguration;
+
+	/** Configuration characteristics */
+	uint8_t  bmAttributes;
+
+	/** Maximum power consumption of the USB device from this bus in this
+	 * configuration when the device is fully operation. Expressed in units
+	 * of 2 mA when the device is operating in high-speed mode and in units
+	 * of 8 mA when the device is operating in super-speed mode. */
+	uint8_t  MaxPower;
+
+	/** Array of interfaces supported by this configuration. The length of
+	 * this array is determined by the bNumInterfaces field. */
+	const struct libusb_interface *interface;
+
+	/** Extra descriptors. If libusb encounters unknown configuration
+	 * descriptors, it will store them here, should you wish to parse them. */
+	const unsigned char *extra;
+
+	/** Length of the extra descriptors, in bytes. */
+	int extra_length;
+};
+
+/** \ingroup libusb_desc
+ * A structure representing the superspeed endpoint companion
+ * descriptor. This descriptor is documented in section 9.6.7 of
+ * the USB 3.0 specification. All multiple-byte fields are represented in
+ * host-endian format.
+ */
+struct libusb_ss_endpoint_companion_descriptor {
+
+	/** Size of this descriptor (in bytes) */
+	uint8_t  bLength;
+
+	/** Descriptor type. Will have value
+	 * \ref libusb_descriptor_type::LIBUSB_DT_SS_ENDPOINT_COMPANION in
+	 * this context. */
+	uint8_t  bDescriptorType;
+
+
+	/** The maximum number of packets the endpoint can send or
+	 *  receive as part of a burst. */
+	uint8_t  bMaxBurst;
+
+	/** In bulk EP:	bits 4:0 represents the	maximum	number of
+	 *  streams the	EP supports. In	isochronous EP:	bits 1:0
+	 *  represents the Mult	- a zero based value that determines
+	 *  the	maximum	number of packets within a service interval  */
+	uint8_t  bmAttributes;
+
+	/** The	total number of bytes this EP will transfer every
+	 *  service interval. valid only for periodic EPs. */
+	uint16_t wBytesPerInterval;
+};
+
+/** \ingroup libusb_desc
+ * A generic representation of a BOS Device Capability descriptor. It is
+ * advised to check bDevCapabilityType and call the matching
+ * libusb_get_*_descriptor function to get a structure fully matching the type.
+ */
+struct libusb_bos_dev_capability_descriptor {
+	/** Size of this descriptor (in bytes) */
+	uint8_t bLength;
+	/** Descriptor type. Will have value
+	 * \ref libusb_descriptor_type::LIBUSB_DT_DEVICE_CAPABILITY
+	 * LIBUSB_DT_DEVICE_CAPABILITY in this context. */
+	uint8_t bDescriptorType;
+	/** Device Capability type */
+	uint8_t bDevCapabilityType;
+	/** Device Capability data (bLength - 3 bytes) */
+	uint8_t dev_capability_data
+#if defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L)
+	[] /* valid C99 code */
+#else
+	[0] /* non-standard, but usually working code */
+#endif
+	;
+};
+
+/** \ingroup libusb_desc
+ * A structure representing the Binary Device Object Store (BOS) descriptor.
+ * This descriptor is documented in section 9.6.2 of the USB 3.0 specification.
+ * All multiple-byte fields are represented in host-endian format.
+ */
+struct libusb_bos_descriptor {
+	/** Size of this descriptor (in bytes) */
+	uint8_t  bLength;
+
+	/** Descriptor type. Will have value
+	 * \ref libusb_descriptor_type::LIBUSB_DT_BOS LIBUSB_DT_BOS
+	 * in this context. */
+	uint8_t  bDescriptorType;
+
+	/** Length of this descriptor and all of its sub descriptors */
+	uint16_t wTotalLength;
+
+	/** The number of separate device capability descriptors in
+	 * the BOS */
+	uint8_t  bNumDeviceCaps;
+
+	/** bNumDeviceCap Device Capability Descriptors */
+	struct libusb_bos_dev_capability_descriptor *dev_capability
+#if defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L)
+	[] /* valid C99 code */
+#else
+	[0] /* non-standard, but usually working code */
+#endif
+	;
+};
+
+/** \ingroup libusb_desc
+ * A structure representing the USB 2.0 Extension descriptor
+ * This descriptor is documented in section 9.6.2.1 of the USB 3.0 specification.
+ * All multiple-byte fields are represented in host-endian format.
+ */
+struct libusb_usb_2_0_extension_descriptor {
+	/** Size of this descriptor (in bytes) */
+	uint8_t  bLength;
+
+	/** Descriptor type. Will have value
+	 * \ref libusb_descriptor_type::LIBUSB_DT_DEVICE_CAPABILITY
+	 * LIBUSB_DT_DEVICE_CAPABILITY in this context. */
+	uint8_t  bDescriptorType;
+
+	/** Capability type. Will have value
+	 * \ref libusb_capability_type::LIBUSB_BT_USB_2_0_EXTENSION
+	 * LIBUSB_BT_USB_2_0_EXTENSION in this context. */
+	uint8_t  bDevCapabilityType;
+
+	/** Bitmap encoding of supported device level features.
+	 * A value of one in a bit location indicates a feature is
+	 * supported; a value of zero indicates it is not supported.
+	 * See \ref libusb_usb_2_0_extension_attributes. */
+	uint32_t  bmAttributes;
+};
+
+/** \ingroup libusb_desc
+ * A structure representing the SuperSpeed USB Device Capability descriptor
+ * This descriptor is documented in section 9.6.2.2 of the USB 3.0 specification.
+ * All multiple-byte fields are represented in host-endian format.
+ */
+struct libusb_ss_usb_device_capability_descriptor {
+	/** Size of this descriptor (in bytes) */
+	uint8_t  bLength;
+
+	/** Descriptor type. Will have value
+	 * \ref libusb_descriptor_type::LIBUSB_DT_DEVICE_CAPABILITY
+	 * LIBUSB_DT_DEVICE_CAPABILITY in this context. */
+	uint8_t  bDescriptorType;
+
+	/** Capability type. Will have value
+	 * \ref libusb_capability_type::LIBUSB_BT_SS_USB_DEVICE_CAPABILITY
+	 * LIBUSB_BT_SS_USB_DEVICE_CAPABILITY in this context. */
+	uint8_t  bDevCapabilityType;
+
+	/** Bitmap encoding of supported device level features.
+	 * A value of one in a bit location indicates a feature is
+	 * supported; a value of zero indicates it is not supported.
+	 * See \ref libusb_ss_usb_device_capability_attributes. */
+	uint8_t  bmAttributes;
+
+	/** Bitmap encoding of the speed supported by this device when
+	 * operating in SuperSpeed mode. See \ref libusb_supported_speed. */
+	uint16_t wSpeedSupported;
+
+	/** The lowest speed at which all the functionality supported
+	 * by the device is available to the user. For example if the
+	 * device supports all its functionality when connected at
+	 * full speed and above then it sets this value to 1. */
+	uint8_t  bFunctionalitySupport;
+
+	/** U1 Device Exit Latency. */
+	uint8_t  bU1DevExitLat;
+
+	/** U2 Device Exit Latency. */
+	uint16_t bU2DevExitLat;
+};
+
+/** \ingroup libusb_desc
+ * A structure representing the Container ID descriptor.
+ * This descriptor is documented in section 9.6.2.3 of the USB 3.0 specification.
+ * All multiple-byte fields, except UUIDs, are represented in host-endian format.
+ */
+struct libusb_container_id_descriptor {
+	/** Size of this descriptor (in bytes) */
+	uint8_t  bLength;
+
+	/** Descriptor type. Will have value
+	 * \ref libusb_descriptor_type::LIBUSB_DT_DEVICE_CAPABILITY
+	 * LIBUSB_DT_DEVICE_CAPABILITY in this context. */
+	uint8_t  bDescriptorType;
+
+	/** Capability type. Will have value
+	 * \ref libusb_capability_type::LIBUSB_BT_CONTAINER_ID
+	 * LIBUSB_BT_CONTAINER_ID in this context. */
+	uint8_t  bDevCapabilityType;
+
+	/** Reserved field */
+	uint8_t bReserved;
+
+	/** 128 bit UUID */
+	uint8_t  ContainerID[16];
+};
+
+/** \ingroup libusb_asyncio
+ * Setup packet for control transfers. */
+struct libusb_control_setup {
+	/** Request type. Bits 0:4 determine recipient, see
+	 * \ref libusb_request_recipient. Bits 5:6 determine type, see
+	 * \ref libusb_request_type. Bit 7 determines data transfer direction, see
+	 * \ref libusb_endpoint_direction.
+	 */
+	uint8_t  bmRequestType;
+
+	/** Request. If the type bits of bmRequestType are equal to
+	 * \ref libusb_request_type::LIBUSB_REQUEST_TYPE_STANDARD
+	 * "LIBUSB_REQUEST_TYPE_STANDARD" then this field refers to
+	 * \ref libusb_standard_request. For other cases, use of this field is
+	 * application-specific. */
+	uint8_t  bRequest;
+
+	/** Value. Varies according to request */
+	uint16_t wValue;
+
+	/** Index. Varies according to request, typically used to pass an index
+	 * or offset */
+	uint16_t wIndex;
+
+	/** Number of bytes to transfer */
+	uint16_t wLength;
+};
+
+#define LIBUSB_CONTROL_SETUP_SIZE (sizeof(struct libusb_control_setup))
+
+/* libusb */
+
+struct libusb_context;
+struct libusb_device;
+struct libusb_device_handle;
+
+/** \ingroup libusb_lib
+ * Structure providing the version of the libusb runtime
+ */
+struct libusb_version {
+	/** Library major version. */
+	const uint16_t major;
+
+	/** Library minor version. */
+	const uint16_t minor;
+
+	/** Library micro version. */
+	const uint16_t micro;
+
+	/** Library nano version. */
+	const uint16_t nano;
+
+	/** Library release candidate suffix string, e.g. "-rc4". */
+	const char *rc;
+
+	/** For ABI compatibility only. */
+	const char* describe;
+};
+
+/** \ingroup libusb_lib
+ * Structure representing a libusb session. The concept of individual libusb
+ * sessions allows for your program to use two libraries (or dynamically
+ * load two modules) which both independently use libusb. This will prevent
+ * interference between the individual libusb users - for example
+ * libusb_set_debug() will not affect the other user of the library, and
+ * libusb_exit() will not destroy resources that the other user is still
+ * using.
+ *
+ * Sessions are created by libusb_init() and destroyed through libusb_exit().
+ * If your application is guaranteed to only ever include a single libusb
+ * user (i.e. you), you do not have to worry about contexts: pass NULL in
+ * every function call where a context is required. The default context
+ * will be used.
+ *
+ * For more information, see \ref libusb_contexts.
+ */
+typedef struct libusb_context libusb_context;
+
+/** \ingroup libusb_dev
+ * Structure representing a USB device detected on the system. This is an
+ * opaque type for which you are only ever provided with a pointer, usually
+ * originating from libusb_get_device_list().
+ *
+ * Certain operations can be performed on a device, but in order to do any
+ * I/O you will have to first obtain a device handle using libusb_open().
+ *
+ * Devices are reference counted with libusb_ref_device() and
+ * libusb_unref_device(), and are freed when the reference count reaches 0.
+ * New devices presented by libusb_get_device_list() have a reference count of
+ * 1, and libusb_free_device_list() can optionally decrease the reference count
+ * on all devices in the list. libusb_open() adds another reference which is
+ * later destroyed by libusb_close().
+ */
+typedef struct libusb_device libusb_device;
+
+
+/** \ingroup libusb_dev
+ * Structure representing a handle on a USB device. This is an opaque type for
+ * which you are only ever provided with a pointer, usually originating from
+ * libusb_open().
+ *
+ * A device handle is used to perform I/O and other operations. When finished
+ * with a device handle, you should call libusb_close().
+ */
+typedef struct libusb_device_handle libusb_device_handle;
+
+/** \ingroup libusb_dev
+ * Speed codes. Indicates the speed at which the device is operating.
+ */
+enum libusb_speed {
+	/** The OS doesn't report or know the device speed. */
+	LIBUSB_SPEED_UNKNOWN = 0,
+
+	/** The device is operating at low speed (1.5MBit/s). */
+	LIBUSB_SPEED_LOW = 1,
+
+	/** The device is operating at full speed (12MBit/s). */
+	LIBUSB_SPEED_FULL = 2,
+
+	/** The device is operating at high speed (480MBit/s). */
+	LIBUSB_SPEED_HIGH = 3,
+
+	/** The device is operating at super speed (5000MBit/s). */
+	LIBUSB_SPEED_SUPER = 4,
+};
+
+/** \ingroup libusb_dev
+ * Supported speeds (wSpeedSupported) bitfield. Indicates what
+ * speeds the device supports.
+ */
+enum libusb_supported_speed {
+	/** Low speed operation supported (1.5MBit/s). */
+	LIBUSB_LOW_SPEED_OPERATION   = 1,
+
+	/** Full speed operation supported (12MBit/s). */
+	LIBUSB_FULL_SPEED_OPERATION  = 2,
+
+	/** High speed operation supported (480MBit/s). */
+	LIBUSB_HIGH_SPEED_OPERATION  = 4,
+
+	/** Superspeed operation supported (5000MBit/s). */
+	LIBUSB_SUPER_SPEED_OPERATION = 8,
+};
+
+/** \ingroup libusb_dev
+ * Masks for the bits of the
+ * \ref libusb_usb_2_0_extension_descriptor::bmAttributes "bmAttributes" field
+ * of the USB 2.0 Extension descriptor.
+ */
+enum libusb_usb_2_0_extension_attributes {
+	/** Supports Link Power Management (LPM) */
+	LIBUSB_BM_LPM_SUPPORT = 2,
+};
+
+/** \ingroup libusb_dev
+ * Masks for the bits of the
+ * \ref libusb_ss_usb_device_capability_descriptor::bmAttributes "bmAttributes" field
+ * field of the SuperSpeed USB Device Capability descriptor.
+ */
+enum libusb_ss_usb_device_capability_attributes {
+	/** Supports Latency Tolerance Messages (LTM) */
+	LIBUSB_BM_LTM_SUPPORT = 2,
+};
+
+/** \ingroup libusb_dev
+ * USB capability types
+ */
+enum libusb_bos_type {
+	/** Wireless USB device capability */
+	LIBUSB_BT_WIRELESS_USB_DEVICE_CAPABILITY	= 1,
+
+	/** USB 2.0 extensions */
+	LIBUSB_BT_USB_2_0_EXTENSION			= 2,
+
+	/** SuperSpeed USB device capability */
+	LIBUSB_BT_SS_USB_DEVICE_CAPABILITY		= 3,
+
+	/** Container ID type */
+	LIBUSB_BT_CONTAINER_ID				= 4,
+};
+
+/** \ingroup libusb_misc
+ * Error codes. Most libusb functions return 0 on success or one of these
+ * codes on failure.
+ * You can call libusb_error_name() to retrieve a string representation of an
+ * error code or libusb_strerror() to get an end-user suitable description of
+ * an error code.
+ */
+enum libusb_error {
+	/** Success (no error) */
+	LIBUSB_SUCCESS = 0,
+
+	/** Input/output error */
+	LIBUSB_ERROR_IO = -1,
+
+	/** Invalid parameter */
+	LIBUSB_ERROR_INVALID_PARAM = -2,
+
+	/** Access denied (insufficient permissions) */
+	LIBUSB_ERROR_ACCESS = -3,
+
+	/** No such device (it may have been disconnected) */
+	LIBUSB_ERROR_NO_DEVICE = -4,
+
+	/** Entity not found */
+	LIBUSB_ERROR_NOT_FOUND = -5,
+
+	/** Resource busy */
+	LIBUSB_ERROR_BUSY = -6,
+
+	/** Operation timed out */
+	LIBUSB_ERROR_TIMEOUT = -7,
+
+	/** Overflow */
+	LIBUSB_ERROR_OVERFLOW = -8,
+
+	/** Pipe error */
+	LIBUSB_ERROR_PIPE = -9,
+
+	/** System call interrupted (perhaps due to signal) */
+	LIBUSB_ERROR_INTERRUPTED = -10,
+
+	/** Insufficient memory */
+	LIBUSB_ERROR_NO_MEM = -11,
+
+	/** Operation not supported or unimplemented on this platform */
+	LIBUSB_ERROR_NOT_SUPPORTED = -12,
+
+	/* NB: Remember to update LIBUSB_ERROR_COUNT below as well as the
+	   message strings in strerror.c when adding new error codes here. */
+
+	/** Other error */
+	LIBUSB_ERROR_OTHER = -99,
+};
+
+/* Total number of error codes in enum libusb_error */
+#define LIBUSB_ERROR_COUNT 14
+
+/** \ingroup libusb_asyncio
+ * Transfer status codes */
+enum libusb_transfer_status {
+	/** Transfer completed without error. Note that this does not indicate
+	 * that the entire amount of requested data was transferred. */
+	LIBUSB_TRANSFER_COMPLETED,
+
+	/** Transfer failed */
+	LIBUSB_TRANSFER_ERROR,
+
+	/** Transfer timed out */
+	LIBUSB_TRANSFER_TIMED_OUT,
+
+	/** Transfer was cancelled */
+	LIBUSB_TRANSFER_CANCELLED,
+
+	/** For bulk/interrupt endpoints: halt condition detected (endpoint
+	 * stalled). For control endpoints: control request not supported. */
+	LIBUSB_TRANSFER_STALL,
+
+	/** Device was disconnected */
+	LIBUSB_TRANSFER_NO_DEVICE,
+
+	/** Device sent more data than requested */
+	LIBUSB_TRANSFER_OVERFLOW,
+
+	/* NB! Remember to update libusb_error_name()
+	   when adding new status codes here. */
+};
+
+/** \ingroup libusb_asyncio
+ * libusb_transfer.flags values */
+enum libusb_transfer_flags {
+	/** Report short frames as errors */
+	LIBUSB_TRANSFER_SHORT_NOT_OK = 1<<0,
+
+	/** Automatically free() transfer buffer during libusb_free_transfer().
+	 * Note that buffers allocated with libusb_dev_mem_alloc() should not
+	 * be attempted freed in this way, since free() is not an appropriate
+	 * way to release such memory. */
+	LIBUSB_TRANSFER_FREE_BUFFER = 1<<1,
+
+	/** Automatically call libusb_free_transfer() after callback returns.
+	 * If this flag is set, it is illegal to call libusb_free_transfer()
+	 * from your transfer callback, as this will result in a double-free
+	 * when this flag is acted upon. */
+	LIBUSB_TRANSFER_FREE_TRANSFER = 1<<2,
+
+	/** Terminate transfers that are a multiple of the endpoint's
+	 * wMaxPacketSize with an extra zero length packet. This is useful
+	 * when a device protocol mandates that each logical request is
+	 * terminated by an incomplete packet (i.e. the logical requests are
+	 * not separated by other means).
+	 *
+	 * This flag only affects host-to-device transfers to bulk and interrupt
+	 * endpoints. In other situations, it is ignored.
+	 *
+	 * This flag only affects transfers with a length that is a multiple of
+	 * the endpoint's wMaxPacketSize. On transfers of other lengths, this
+	 * flag has no effect. Therefore, if you are working with a device that
+	 * needs a ZLP whenever the end of the logical request falls on a packet
+	 * boundary, then it is sensible to set this flag on <em>every</em>
+	 * transfer (you do not have to worry about only setting it on transfers
+	 * that end on the boundary).
+	 *
+	 * This flag is currently only supported on Linux.
+	 * On other systems, libusb_submit_transfer() will return
+	 * LIBUSB_ERROR_NOT_SUPPORTED for every transfer where this flag is set.
+	 *
+	 * Available since libusb-1.0.9.
+	 */
+	LIBUSB_TRANSFER_ADD_ZERO_PACKET = 1 << 3,
+};
+
+/** \ingroup libusb_asyncio
+ * Isochronous packet descriptor. */
+struct libusb_iso_packet_descriptor {
+	/** Length of data to request in this packet */
+	unsigned int length;
+
+	/** Amount of data that was actually transferred */
+	unsigned int actual_length;
+
+	/** Status code for this packet */
+	enum libusb_transfer_status status;
+};
+
+struct libusb_transfer;
+
+/** \ingroup libusb_asyncio
+ * Asynchronous transfer callback function type. When submitting asynchronous
+ * transfers, you pass a pointer to a callback function of this type via the
+ * \ref libusb_transfer::callback "callback" member of the libusb_transfer
+ * structure. libusb will call this function later, when the transfer has
+ * completed or failed. See \ref libusb_asyncio for more information.
+ * \param transfer The libusb_transfer struct the callback function is being
+ * notified about.
+ */
+typedef void (LIBUSB_CALL *libusb_transfer_cb_fn)(struct libusb_transfer *transfer);
+
+/** \ingroup libusb_asyncio
+ * The generic USB transfer structure. The user populates this structure and
+ * then submits it in order to request a transfer. After the transfer has
+ * completed, the library populates the transfer with the results and passes
+ * it back to the user.
+ */
+struct libusb_transfer {
+	/** Handle of the device that this transfer will be submitted to */
+	libusb_device_handle *dev_handle;
+
+	/** A bitwise OR combination of \ref libusb_transfer_flags. */
+	uint8_t flags;
+
+	/** Address of the endpoint where this transfer will be sent. */
+	unsigned char endpoint;
+
+	/** Type of the endpoint from \ref libusb_transfer_type */
+	unsigned char type;
+
+	/** Timeout for this transfer in milliseconds. A value of 0 indicates no
+	 * timeout. */
+	unsigned int timeout;
+
+	/** The status of the transfer. Read-only, and only for use within
+	 * transfer callback function.
+	 *
+	 * If this is an isochronous transfer, this field may read COMPLETED even
+	 * if there were errors in the frames. Use the
+	 * \ref libusb_iso_packet_descriptor::status "status" field in each packet
+	 * to determine if errors occurred. */
+	enum libusb_transfer_status status;
+
+	/** Length of the data buffer */
+	int length;
+
+	/** Actual length of data that was transferred. Read-only, and only for
+	 * use within transfer callback function. Not valid for isochronous
+	 * endpoint transfers. */
+	int actual_length;
+
+	/** Callback function. This will be invoked when the transfer completes,
+	 * fails, or is cancelled. */
+	libusb_transfer_cb_fn callback;
+
+	/** User context data to pass to the callback function. */
+	void *user_data;
+
+	/** Data buffer */
+	unsigned char *buffer;
+
+	/** Number of isochronous packets. Only used for I/O with isochronous
+	 * endpoints. */
+	int num_iso_packets;
+
+	/** Isochronous packet descriptors, for isochronous transfers only. */
+	struct libusb_iso_packet_descriptor iso_packet_desc
+#if defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L)
+	[] /* valid C99 code */
+#else
+	[0] /* non-standard, but usually working code */
+#endif
+	;
+};
+
+/** \ingroup libusb_misc
+ * Capabilities supported by an instance of libusb on the current running
+ * platform. Test if the loaded library supports a given capability by calling
+ * \ref libusb_has_capability().
+ */
+enum libusb_capability {
+	/** The libusb_has_capability() API is available. */
+	LIBUSB_CAP_HAS_CAPABILITY = 0x0000,
+	/** Hotplug support is available on this platform. */
+	LIBUSB_CAP_HAS_HOTPLUG = 0x0001,
+	/** The library can access HID devices without requiring user intervention.
+	 * Note that before being able to actually access an HID device, you may
+	 * still have to call additional libusb functions such as
+	 * \ref libusb_detach_kernel_driver(). */
+	LIBUSB_CAP_HAS_HID_ACCESS = 0x0100,
+	/** The library supports detaching of the default USB driver, using 
+	 * \ref libusb_detach_kernel_driver(), if one is set by the OS kernel */
+	LIBUSB_CAP_SUPPORTS_DETACH_KERNEL_DRIVER = 0x0101
+};
+
+/** \ingroup libusb_lib
+ *  Log message levels.
+ *  - LIBUSB_LOG_LEVEL_NONE (0)    : no messages ever printed by the library (default)
+ *  - LIBUSB_LOG_LEVEL_ERROR (1)   : error messages are printed to stderr
+ *  - LIBUSB_LOG_LEVEL_WARNING (2) : warning and error messages are printed to stderr
+ *  - LIBUSB_LOG_LEVEL_INFO (3)    : informational messages are printed to stdout, warning
+ *    and error messages are printed to stderr
+ *  - LIBUSB_LOG_LEVEL_DEBUG (4)   : debug and informational messages are printed to stdout,
+ *    warnings and errors to stderr
+ */
+enum libusb_log_level {
+	LIBUSB_LOG_LEVEL_NONE = 0,
+	LIBUSB_LOG_LEVEL_ERROR,
+	LIBUSB_LOG_LEVEL_WARNING,
+	LIBUSB_LOG_LEVEL_INFO,
+	LIBUSB_LOG_LEVEL_DEBUG,
+};
+
+int LIBUSB_CALL libusb_init(libusb_context **ctx);
+void LIBUSB_CALL libusb_exit(libusb_context *ctx);
+void LIBUSB_CALL libusb_set_debug(libusb_context *ctx, int level);
+const struct libusb_version * LIBUSB_CALL libusb_get_version(void);
+int LIBUSB_CALL libusb_has_capability(uint32_t capability);
+const char * LIBUSB_CALL libusb_error_name(int errcode);
+int LIBUSB_CALL libusb_setlocale(const char *locale);
+const char * LIBUSB_CALL libusb_strerror(enum libusb_error errcode);
+
+ssize_t LIBUSB_CALL libusb_get_device_list(libusb_context *ctx,
+	libusb_device ***list);
+void LIBUSB_CALL libusb_free_device_list(libusb_device **list,
+	int unref_devices);
+libusb_device * LIBUSB_CALL libusb_ref_device(libusb_device *dev);
+void LIBUSB_CALL libusb_unref_device(libusb_device *dev);
+
+int LIBUSB_CALL libusb_get_configuration(libusb_device_handle *dev,
+	int *config);
+int LIBUSB_CALL libusb_get_device_descriptor(libusb_device *dev,
+	struct libusb_device_descriptor *desc);
+int LIBUSB_CALL libusb_get_active_config_descriptor(libusb_device *dev,
+	struct libusb_config_descriptor **config);
+int LIBUSB_CALL libusb_get_config_descriptor(libusb_device *dev,
+	uint8_t config_index, struct libusb_config_descriptor **config);
+int LIBUSB_CALL libusb_get_config_descriptor_by_value(libusb_device *dev,
+	uint8_t bConfigurationValue, struct libusb_config_descriptor **config);
+void LIBUSB_CALL libusb_free_config_descriptor(
+	struct libusb_config_descriptor *config);
+int LIBUSB_CALL libusb_get_ss_endpoint_companion_descriptor(
+	struct libusb_context *ctx,
+	const struct libusb_endpoint_descriptor *endpoint,
+	struct libusb_ss_endpoint_companion_descriptor **ep_comp);
+void LIBUSB_CALL libusb_free_ss_endpoint_companion_descriptor(
+	struct libusb_ss_endpoint_companion_descriptor *ep_comp);
+int LIBUSB_CALL libusb_get_bos_descriptor(libusb_device_handle *dev_handle,
+	struct libusb_bos_descriptor **bos);
+void LIBUSB_CALL libusb_free_bos_descriptor(struct libusb_bos_descriptor *bos);
+int LIBUSB_CALL libusb_get_usb_2_0_extension_descriptor(
+	struct libusb_context *ctx,
+	struct libusb_bos_dev_capability_descriptor *dev_cap,
+	struct libusb_usb_2_0_extension_descriptor **usb_2_0_extension);
+void LIBUSB_CALL libusb_free_usb_2_0_extension_descriptor(
+	struct libusb_usb_2_0_extension_descriptor *usb_2_0_extension);
+int LIBUSB_CALL libusb_get_ss_usb_device_capability_descriptor(
+	struct libusb_context *ctx,
+	struct libusb_bos_dev_capability_descriptor *dev_cap,
+	struct libusb_ss_usb_device_capability_descriptor **ss_usb_device_cap);
+void LIBUSB_CALL libusb_free_ss_usb_device_capability_descriptor(
+	struct libusb_ss_usb_device_capability_descriptor *ss_usb_device_cap);
+int LIBUSB_CALL libusb_get_container_id_descriptor(struct libusb_context *ctx,
+	struct libusb_bos_dev_capability_descriptor *dev_cap,
+	struct libusb_container_id_descriptor **container_id);
+void LIBUSB_CALL libusb_free_container_id_descriptor(
+	struct libusb_container_id_descriptor *container_id);
+uint8_t LIBUSB_CALL libusb_get_bus_number(libusb_device *dev);
+uint8_t LIBUSB_CALL libusb_get_port_number(libusb_device *dev);
+int LIBUSB_CALL libusb_get_port_numbers(libusb_device *dev, uint8_t* port_numbers, int port_numbers_len);
+LIBUSB_DEPRECATED_FOR(libusb_get_port_numbers)
+int LIBUSB_CALL libusb_get_port_path(libusb_context *ctx, libusb_device *dev, uint8_t* path, uint8_t path_length);
+libusb_device * LIBUSB_CALL libusb_get_parent(libusb_device *dev);
+uint8_t LIBUSB_CALL libusb_get_device_address(libusb_device *dev);
+int LIBUSB_CALL libusb_get_device_speed(libusb_device *dev);
+int LIBUSB_CALL libusb_get_max_packet_size(libusb_device *dev,
+	unsigned char endpoint);
+int LIBUSB_CALL libusb_get_max_iso_packet_size(libusb_device *dev,
+	unsigned char endpoint);
+
+int LIBUSB_CALL libusb_open(libusb_device *dev, libusb_device_handle **dev_handle);
+void LIBUSB_CALL libusb_close(libusb_device_handle *dev_handle);
+libusb_device * LIBUSB_CALL libusb_get_device(libusb_device_handle *dev_handle);
+
+int LIBUSB_CALL libusb_set_configuration(libusb_device_handle *dev_handle,
+	int configuration);
+int LIBUSB_CALL libusb_claim_interface(libusb_device_handle *dev_handle,
+	int interface_number);
+int LIBUSB_CALL libusb_release_interface(libusb_device_handle *dev_handle,
+	int interface_number);
+
+libusb_device_handle * LIBUSB_CALL libusb_open_device_with_vid_pid(
+	libusb_context *ctx, uint16_t vendor_id, uint16_t product_id);
+
+int LIBUSB_CALL libusb_set_interface_alt_setting(libusb_device_handle *dev_handle,
+	int interface_number, int alternate_setting);
+int LIBUSB_CALL libusb_clear_halt(libusb_device_handle *dev_handle,
+	unsigned char endpoint);
+int LIBUSB_CALL libusb_reset_device(libusb_device_handle *dev_handle);
+
+int LIBUSB_CALL libusb_alloc_streams(libusb_device_handle *dev_handle,
+	uint32_t num_streams, unsigned char *endpoints, int num_endpoints);
+int LIBUSB_CALL libusb_free_streams(libusb_device_handle *dev_handle,
+	unsigned char *endpoints, int num_endpoints);
+
+unsigned char * LIBUSB_CALL libusb_dev_mem_alloc(libusb_device_handle *dev_handle,
+	size_t length);
+int LIBUSB_CALL libusb_dev_mem_free(libusb_device_handle *dev_handle,
+	unsigned char *buffer, size_t length);
+
+int LIBUSB_CALL libusb_kernel_driver_active(libusb_device_handle *dev_handle,
+	int interface_number);
+int LIBUSB_CALL libusb_detach_kernel_driver(libusb_device_handle *dev_handle,
+	int interface_number);
+int LIBUSB_CALL libusb_attach_kernel_driver(libusb_device_handle *dev_handle,
+	int interface_number);
+int LIBUSB_CALL libusb_set_auto_detach_kernel_driver(
+	libusb_device_handle *dev_handle, int enable);
+
+/* async I/O */
+
+/** \ingroup libusb_asyncio
+ * Get the data section of a control transfer. This convenience function is here
+ * to remind you that the data does not start until 8 bytes into the actual
+ * buffer, as the setup packet comes first.
+ *
+ * Calling this function only makes sense from a transfer callback function,
+ * or situations where you have already allocated a suitably sized buffer at
+ * transfer->buffer.
+ *
+ * \param transfer a transfer
+ * \returns pointer to the first byte of the data section
+ */
+static inline unsigned char *libusb_control_transfer_get_data(
+	struct libusb_transfer *transfer)
+{
+	return transfer->buffer + LIBUSB_CONTROL_SETUP_SIZE;
+}
+
+/** \ingroup libusb_asyncio
+ * Get the control setup packet of a control transfer. This convenience
+ * function is here to remind you that the control setup occupies the first
+ * 8 bytes of the transfer data buffer.
+ *
+ * Calling this function only makes sense from a transfer callback function,
+ * or situations where you have already allocated a suitably sized buffer at
+ * transfer->buffer.
+ *
+ * \param transfer a transfer
+ * \returns a casted pointer to the start of the transfer data buffer
+ */
+static inline struct libusb_control_setup *libusb_control_transfer_get_setup(
+	struct libusb_transfer *transfer)
+{
+	return (struct libusb_control_setup *)(void *) transfer->buffer;
+}
+
+/** \ingroup libusb_asyncio
+ * Helper function to populate the setup packet (first 8 bytes of the data
+ * buffer) for a control transfer. The wIndex, wValue and wLength values should
+ * be given in host-endian byte order.
+ *
+ * \param buffer buffer to output the setup packet into
+ * This pointer must be aligned to at least 2 bytes boundary.
+ * \param bmRequestType see the
+ * \ref libusb_control_setup::bmRequestType "bmRequestType" field of
+ * \ref libusb_control_setup
+ * \param bRequest see the
+ * \ref libusb_control_setup::bRequest "bRequest" field of
+ * \ref libusb_control_setup
+ * \param wValue see the
+ * \ref libusb_control_setup::wValue "wValue" field of
+ * \ref libusb_control_setup
+ * \param wIndex see the
+ * \ref libusb_control_setup::wIndex "wIndex" field of
+ * \ref libusb_control_setup
+ * \param wLength see the
+ * \ref libusb_control_setup::wLength "wLength" field of
+ * \ref libusb_control_setup
+ */
+static inline void libusb_fill_control_setup(unsigned char *buffer,
+	uint8_t bmRequestType, uint8_t bRequest, uint16_t wValue, uint16_t wIndex,
+	uint16_t wLength)
+{
+	struct libusb_control_setup *setup = (struct libusb_control_setup *)(void *) buffer;
+	setup->bmRequestType = bmRequestType;
+	setup->bRequest = bRequest;
+	setup->wValue = libusb_cpu_to_le16(wValue);
+	setup->wIndex = libusb_cpu_to_le16(wIndex);
+	setup->wLength = libusb_cpu_to_le16(wLength);
+}
+
+struct libusb_transfer * LIBUSB_CALL libusb_alloc_transfer(int iso_packets);
+int LIBUSB_CALL libusb_submit_transfer(struct libusb_transfer *transfer);
+int LIBUSB_CALL libusb_cancel_transfer(struct libusb_transfer *transfer);
+void LIBUSB_CALL libusb_free_transfer(struct libusb_transfer *transfer);
+void LIBUSB_CALL libusb_transfer_set_stream_id(
+	struct libusb_transfer *transfer, uint32_t stream_id);
+uint32_t LIBUSB_CALL libusb_transfer_get_stream_id(
+	struct libusb_transfer *transfer);
+
+/** \ingroup libusb_asyncio
+ * Helper function to populate the required \ref libusb_transfer fields
+ * for a control transfer.
+ *
+ * If you pass a transfer buffer to this function, the first 8 bytes will
+ * be interpreted as a control setup packet, and the wLength field will be
+ * used to automatically populate the \ref libusb_transfer::length "length"
+ * field of the transfer. Therefore the recommended approach is:
+ * -# Allocate a suitably sized data buffer (including space for control setup)
+ * -# Call libusb_fill_control_setup()
+ * -# If this is a host-to-device transfer with a data stage, put the data
+ *    in place after the setup packet
+ * -# Call this function
+ * -# Call libusb_submit_transfer()
+ *
+ * It is also legal to pass a NULL buffer to this function, in which case this
+ * function will not attempt to populate the length field. Remember that you
+ * must then populate the buffer and length fields later.
+ *
+ * \param transfer the transfer to populate
+ * \param dev_handle handle of the device that will handle the transfer
+ * \param buffer data buffer. If provided, this function will interpret the
+ * first 8 bytes as a setup packet and infer the transfer length from that.
+ * This pointer must be aligned to at least 2 bytes boundary.
+ * \param callback callback function to be invoked on transfer completion
+ * \param user_data user data to pass to callback function
+ * \param timeout timeout for the transfer in milliseconds
+ */
+static inline void libusb_fill_control_transfer(
+	struct libusb_transfer *transfer, libusb_device_handle *dev_handle,
+	unsigned char *buffer, libusb_transfer_cb_fn callback, void *user_data,
+	unsigned int timeout)
+{
+	struct libusb_control_setup *setup = (struct libusb_control_setup *)(void *) buffer;
+	transfer->dev_handle = dev_handle;
+	transfer->endpoint = 0;
+	transfer->type = LIBUSB_TRANSFER_TYPE_CONTROL;
+	transfer->timeout = timeout;
+	transfer->buffer = buffer;
+	if (setup)
+		transfer->length = (int) (LIBUSB_CONTROL_SETUP_SIZE
+			+ libusb_le16_to_cpu(setup->wLength));
+	transfer->user_data = user_data;
+	transfer->callback = callback;
+}
+
+/** \ingroup libusb_asyncio
+ * Helper function to populate the required \ref libusb_transfer fields
+ * for a bulk transfer.
+ *
+ * \param transfer the transfer to populate
+ * \param dev_handle handle of the device that will handle the transfer
+ * \param endpoint address of the endpoint where this transfer will be sent
+ * \param buffer data buffer
+ * \param length length of data buffer
+ * \param callback callback function to be invoked on transfer completion
+ * \param user_data user data to pass to callback function
+ * \param timeout timeout for the transfer in milliseconds
+ */
+static inline void libusb_fill_bulk_transfer(struct libusb_transfer *transfer,
+	libusb_device_handle *dev_handle, unsigned char endpoint,
+	unsigned char *buffer, int length, libusb_transfer_cb_fn callback,
+	void *user_data, unsigned int timeout)
+{
+	transfer->dev_handle = dev_handle;
+	transfer->endpoint = endpoint;
+	transfer->type = LIBUSB_TRANSFER_TYPE_BULK;
+	transfer->timeout = timeout;
+	transfer->buffer = buffer;
+	transfer->length = length;
+	transfer->user_data = user_data;
+	transfer->callback = callback;
+}
+
+/** \ingroup libusb_asyncio
+ * Helper function to populate the required \ref libusb_transfer fields
+ * for a bulk transfer using bulk streams.
+ *
+ * Since version 1.0.19, \ref LIBUSB_API_VERSION >= 0x01000103
+ *
+ * \param transfer the transfer to populate
+ * \param dev_handle handle of the device that will handle the transfer
+ * \param endpoint address of the endpoint where this transfer will be sent
+ * \param stream_id bulk stream id for this transfer
+ * \param buffer data buffer
+ * \param length length of data buffer
+ * \param callback callback function to be invoked on transfer completion
+ * \param user_data user data to pass to callback function
+ * \param timeout timeout for the transfer in milliseconds
+ */
+static inline void libusb_fill_bulk_stream_transfer(
+	struct libusb_transfer *transfer, libusb_device_handle *dev_handle,
+	unsigned char endpoint, uint32_t stream_id,
+	unsigned char *buffer, int length, libusb_transfer_cb_fn callback,
+	void *user_data, unsigned int timeout)
+{
+	libusb_fill_bulk_transfer(transfer, dev_handle, endpoint, buffer,
+				  length, callback, user_data, timeout);
+	transfer->type = LIBUSB_TRANSFER_TYPE_BULK_STREAM;
+	libusb_transfer_set_stream_id(transfer, stream_id);
+}
+
+/** \ingroup libusb_asyncio
+ * Helper function to populate the required \ref libusb_transfer fields
+ * for an interrupt transfer.
+ *
+ * \param transfer the transfer to populate
+ * \param dev_handle handle of the device that will handle the transfer
+ * \param endpoint address of the endpoint where this transfer will be sent
+ * \param buffer data buffer
+ * \param length length of data buffer
+ * \param callback callback function to be invoked on transfer completion
+ * \param user_data user data to pass to callback function
+ * \param timeout timeout for the transfer in milliseconds
+ */
+static inline void libusb_fill_interrupt_transfer(
+	struct libusb_transfer *transfer, libusb_device_handle *dev_handle,
+	unsigned char endpoint, unsigned char *buffer, int length,
+	libusb_transfer_cb_fn callback, void *user_data, unsigned int timeout)
+{
+	transfer->dev_handle = dev_handle;
+	transfer->endpoint = endpoint;
+	transfer->type = LIBUSB_TRANSFER_TYPE_INTERRUPT;
+	transfer->timeout = timeout;
+	transfer->buffer = buffer;
+	transfer->length = length;
+	transfer->user_data = user_data;
+	transfer->callback = callback;
+}
+
+/** \ingroup libusb_asyncio
+ * Helper function to populate the required \ref libusb_transfer fields
+ * for an isochronous transfer.
+ *
+ * \param transfer the transfer to populate
+ * \param dev_handle handle of the device that will handle the transfer
+ * \param endpoint address of the endpoint where this transfer will be sent
+ * \param buffer data buffer
+ * \param length length of data buffer
+ * \param num_iso_packets the number of isochronous packets
+ * \param callback callback function to be invoked on transfer completion
+ * \param user_data user data to pass to callback function
+ * \param timeout timeout for the transfer in milliseconds
+ */
+static inline void libusb_fill_iso_transfer(struct libusb_transfer *transfer,
+	libusb_device_handle *dev_handle, unsigned char endpoint,
+	unsigned char *buffer, int length, int num_iso_packets,
+	libusb_transfer_cb_fn callback, void *user_data, unsigned int timeout)
+{
+	transfer->dev_handle = dev_handle;
+	transfer->endpoint = endpoint;
+	transfer->type = LIBUSB_TRANSFER_TYPE_ISOCHRONOUS;
+	transfer->timeout = timeout;
+	transfer->buffer = buffer;
+	transfer->length = length;
+	transfer->num_iso_packets = num_iso_packets;
+	transfer->user_data = user_data;
+	transfer->callback = callback;
+}
+
+/** \ingroup libusb_asyncio
+ * Convenience function to set the length of all packets in an isochronous
+ * transfer, based on the num_iso_packets field in the transfer structure.
+ *
+ * \param transfer a transfer
+ * \param length the length to set in each isochronous packet descriptor
+ * \see libusb_get_max_packet_size()
+ */
+static inline void libusb_set_iso_packet_lengths(
+	struct libusb_transfer *transfer, unsigned int length)
+{
+	int i;
+	for (i = 0; i < transfer->num_iso_packets; i++)
+		transfer->iso_packet_desc[i].length = length;
+}
+
+/** \ingroup libusb_asyncio
+ * Convenience function to locate the position of an isochronous packet
+ * within the buffer of an isochronous transfer.
+ *
+ * This is a thorough function which loops through all preceding packets,
+ * accumulating their lengths to find the position of the specified packet.
+ * Typically you will assign equal lengths to each packet in the transfer,
+ * and hence the above method is sub-optimal. You may wish to use
+ * libusb_get_iso_packet_buffer_simple() instead.
+ *
+ * \param transfer a transfer
+ * \param packet the packet to return the address of
+ * \returns the base address of the packet buffer inside the transfer buffer,
+ * or NULL if the packet does not exist.
+ * \see libusb_get_iso_packet_buffer_simple()
+ */
+static inline unsigned char *libusb_get_iso_packet_buffer(
+	struct libusb_transfer *transfer, unsigned int packet)
+{
+	int i;
+	size_t offset = 0;
+	int _packet;
+
+	/* oops..slight bug in the API. packet is an unsigned int, but we use
+	 * signed integers almost everywhere else. range-check and convert to
+	 * signed to avoid compiler warnings. FIXME for libusb-2. */
+	if (packet > INT_MAX)
+		return NULL;
+	_packet = (int) packet;
+
+	if (_packet >= transfer->num_iso_packets)
+		return NULL;
+
+	for (i = 0; i < _packet; i++)
+		offset += transfer->iso_packet_desc[i].length;
+
+	return transfer->buffer + offset;
+}
+
+/** \ingroup libusb_asyncio
+ * Convenience function to locate the position of an isochronous packet
+ * within the buffer of an isochronous transfer, for transfers where each
+ * packet is of identical size.
+ *
+ * This function relies on the assumption that every packet within the transfer
+ * is of identical size to the first packet. Calculating the location of
+ * the packet buffer is then just a simple calculation:
+ * <tt>buffer + (packet_size * packet)</tt>
+ *
+ * Do not use this function on transfers other than those that have identical
+ * packet lengths for each packet.
+ *
+ * \param transfer a transfer
+ * \param packet the packet to return the address of
+ * \returns the base address of the packet buffer inside the transfer buffer,
+ * or NULL if the packet does not exist.
+ * \see libusb_get_iso_packet_buffer()
+ */
+static inline unsigned char *libusb_get_iso_packet_buffer_simple(
+	struct libusb_transfer *transfer, unsigned int packet)
+{
+	int _packet;
+
+	/* oops..slight bug in the API. packet is an unsigned int, but we use
+	 * signed integers almost everywhere else. range-check and convert to
+	 * signed to avoid compiler warnings. FIXME for libusb-2. */
+	if (packet > INT_MAX)
+		return NULL;
+	_packet = (int) packet;
+
+	if (_packet >= transfer->num_iso_packets)
+		return NULL;
+
+	return transfer->buffer + ((int) transfer->iso_packet_desc[0].length * _packet);
+}
+
+/* sync I/O */
+
+int LIBUSB_CALL libusb_control_transfer(libusb_device_handle *dev_handle,
+	uint8_t request_type, uint8_t bRequest, uint16_t wValue, uint16_t wIndex,
+	unsigned char *data, uint16_t wLength, unsigned int timeout);
+
+int LIBUSB_CALL libusb_bulk_transfer(libusb_device_handle *dev_handle,
+	unsigned char endpoint, unsigned char *data, int length,
+	int *actual_length, unsigned int timeout);
+
+int LIBUSB_CALL libusb_interrupt_transfer(libusb_device_handle *dev_handle,
+	unsigned char endpoint, unsigned char *data, int length,
+	int *actual_length, unsigned int timeout);
+
+/** \ingroup libusb_desc
+ * Retrieve a descriptor from the default control pipe.
+ * This is a convenience function which formulates the appropriate control
+ * message to retrieve the descriptor.
+ *
+ * \param dev_handle a device handle
+ * \param desc_type the descriptor type, see \ref libusb_descriptor_type
+ * \param desc_index the index of the descriptor to retrieve
+ * \param data output buffer for descriptor
+ * \param length size of data buffer
+ * \returns number of bytes returned in data, or LIBUSB_ERROR code on failure
+ */
+static inline int libusb_get_descriptor(libusb_device_handle *dev_handle,
+	uint8_t desc_type, uint8_t desc_index, unsigned char *data, int length)
+{
+	return libusb_control_transfer(dev_handle, LIBUSB_ENDPOINT_IN,
+		LIBUSB_REQUEST_GET_DESCRIPTOR, (uint16_t) ((desc_type << 8) | desc_index),
+		0, data, (uint16_t) length, 1000);
+}
+
+/** \ingroup libusb_desc
+ * Retrieve a descriptor from a device.
+ * This is a convenience function which formulates the appropriate control
+ * message to retrieve the descriptor. The string returned is Unicode, as
+ * detailed in the USB specifications.
+ *
+ * \param dev_handle a device handle
+ * \param desc_index the index of the descriptor to retrieve
+ * \param langid the language ID for the string descriptor
+ * \param data output buffer for descriptor
+ * \param length size of data buffer
+ * \returns number of bytes returned in data, or LIBUSB_ERROR code on failure
+ * \see libusb_get_string_descriptor_ascii()
+ */
+static inline int libusb_get_string_descriptor(libusb_device_handle *dev_handle,
+	uint8_t desc_index, uint16_t langid, unsigned char *data, int length)
+{
+	return libusb_control_transfer(dev_handle, LIBUSB_ENDPOINT_IN,
+		LIBUSB_REQUEST_GET_DESCRIPTOR, (uint16_t)((LIBUSB_DT_STRING << 8) | desc_index),
+		langid, data, (uint16_t) length, 1000);
+}
+
+int LIBUSB_CALL libusb_get_string_descriptor_ascii(libusb_device_handle *dev_handle,
+	uint8_t desc_index, unsigned char *data, int length);
+
+/* polling and timeouts */
+
+int LIBUSB_CALL libusb_try_lock_events(libusb_context *ctx);
+void LIBUSB_CALL libusb_lock_events(libusb_context *ctx);
+void LIBUSB_CALL libusb_unlock_events(libusb_context *ctx);
+int LIBUSB_CALL libusb_event_handling_ok(libusb_context *ctx);
+int LIBUSB_CALL libusb_event_handler_active(libusb_context *ctx);
+void LIBUSB_CALL libusb_interrupt_event_handler(libusb_context *ctx);
+void LIBUSB_CALL libusb_lock_event_waiters(libusb_context *ctx);
+void LIBUSB_CALL libusb_unlock_event_waiters(libusb_context *ctx);
+int LIBUSB_CALL libusb_wait_for_event(libusb_context *ctx, struct timeval *tv);
+
+int LIBUSB_CALL libusb_handle_events_timeout(libusb_context *ctx,
+	struct timeval *tv);
+int LIBUSB_CALL libusb_handle_events_timeout_completed(libusb_context *ctx,
+	struct timeval *tv, int *completed);
+int LIBUSB_CALL libusb_handle_events(libusb_context *ctx);
+int LIBUSB_CALL libusb_handle_events_completed(libusb_context *ctx, int *completed);
+int LIBUSB_CALL libusb_handle_events_locked(libusb_context *ctx,
+	struct timeval *tv);
+int LIBUSB_CALL libusb_pollfds_handle_timeouts(libusb_context *ctx);
+int LIBUSB_CALL libusb_get_next_timeout(libusb_context *ctx,
+	struct timeval *tv);
+
+/** \ingroup libusb_poll
+ * File descriptor for polling
+ */
+struct libusb_pollfd {
+	/** Numeric file descriptor */
+	int fd;
+
+	/** Event flags to poll for from <poll.h>. POLLIN indicates that you
+	 * should monitor this file descriptor for becoming ready to read from,
+	 * and POLLOUT indicates that you should monitor this file descriptor for
+	 * nonblocking write readiness. */
+	short events;
+};
+
+/** \ingroup libusb_poll
+ * Callback function, invoked when a new file descriptor should be added
+ * to the set of file descriptors monitored for events.
+ * \param fd the new file descriptor
+ * \param events events to monitor for, see \ref libusb_pollfd for a
+ * description
+ * \param user_data User data pointer specified in
+ * libusb_set_pollfd_notifiers() call
+ * \see libusb_set_pollfd_notifiers()
+ */
+typedef void (LIBUSB_CALL *libusb_pollfd_added_cb)(int fd, short events,
+	void *user_data);
+
+/** \ingroup libusb_poll
+ * Callback function, invoked when a file descriptor should be removed from
+ * the set of file descriptors being monitored for events. After returning
+ * from this callback, do not use that file descriptor again.
+ * \param fd the file descriptor to stop monitoring
+ * \param user_data User data pointer specified in
+ * libusb_set_pollfd_notifiers() call
+ * \see libusb_set_pollfd_notifiers()
+ */
+typedef void (LIBUSB_CALL *libusb_pollfd_removed_cb)(int fd, void *user_data);
+
+const struct libusb_pollfd ** LIBUSB_CALL libusb_get_pollfds(
+	libusb_context *ctx);
+void LIBUSB_CALL libusb_free_pollfds(const struct libusb_pollfd **pollfds);
+void LIBUSB_CALL libusb_set_pollfd_notifiers(libusb_context *ctx,
+	libusb_pollfd_added_cb added_cb, libusb_pollfd_removed_cb removed_cb,
+	void *user_data);
+
+/** \ingroup libusb_hotplug
+ * Callback handle.
+ *
+ * Callbacks handles are generated by libusb_hotplug_register_callback()
+ * and can be used to deregister callbacks. Callback handles are unique
+ * per libusb_context and it is safe to call libusb_hotplug_deregister_callback()
+ * on an already deregisted callback.
+ *
+ * Since version 1.0.16, \ref LIBUSB_API_VERSION >= 0x01000102
+ *
+ * For more information, see \ref libusb_hotplug.
+ */
+typedef int libusb_hotplug_callback_handle;
+
+/** \ingroup libusb_hotplug
+ *
+ * Since version 1.0.16, \ref LIBUSB_API_VERSION >= 0x01000102
+ *
+ * Flags for hotplug events */
+typedef enum {
+	/** Default value when not using any flags. */
+	LIBUSB_HOTPLUG_NO_FLAGS = 0,
+
+	/** Arm the callback and fire it for all matching currently attached devices. */
+	LIBUSB_HOTPLUG_ENUMERATE = 1<<0,
+} libusb_hotplug_flag;
+
+/** \ingroup libusb_hotplug
+ *
+ * Since version 1.0.16, \ref LIBUSB_API_VERSION >= 0x01000102
+ *
+ * Hotplug events */
+typedef enum {
+	/** A device has been plugged in and is ready to use */
+	LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED = 0x01,
+
+	/** A device has left and is no longer available.
+	 * It is the user's responsibility to call libusb_close on any handle associated with a disconnected device.
+	 * It is safe to call libusb_get_device_descriptor on a device that has left */
+	LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT    = 0x02,
+} libusb_hotplug_event;
+
+/** \ingroup libusb_hotplug
+ * Wildcard matching for hotplug events */
+#define LIBUSB_HOTPLUG_MATCH_ANY -1
+
+/** \ingroup libusb_hotplug
+ * Hotplug callback function type. When requesting hotplug event notifications,
+ * you pass a pointer to a callback function of this type.
+ *
+ * This callback may be called by an internal event thread and as such it is
+ * recommended the callback do minimal processing before returning.
+ *
+ * libusb will call this function later, when a matching event had happened on
+ * a matching device. See \ref libusb_hotplug for more information.
+ *
+ * It is safe to call either libusb_hotplug_register_callback() or
+ * libusb_hotplug_deregister_callback() from within a callback function.
+ *
+ * Since version 1.0.16, \ref LIBUSB_API_VERSION >= 0x01000102
+ *
+ * \param ctx            context of this notification
+ * \param device         libusb_device this event occurred on
+ * \param event          event that occurred
+ * \param user_data      user data provided when this callback was registered
+ * \returns bool whether this callback is finished processing events.
+ *                       returning 1 will cause this callback to be deregistered
+ */
+typedef int (LIBUSB_CALL *libusb_hotplug_callback_fn)(libusb_context *ctx,
+						libusb_device *device,
+						libusb_hotplug_event event,
+						void *user_data);
+
+/** \ingroup libusb_hotplug
+ * Register a hotplug callback function
+ *
+ * Register a callback with the libusb_context. The callback will fire
+ * when a matching event occurs on a matching device. The callback is
+ * armed until either it is deregistered with libusb_hotplug_deregister_callback()
+ * or the supplied callback returns 1 to indicate it is finished processing events.
+ *
+ * If the \ref LIBUSB_HOTPLUG_ENUMERATE is passed the callback will be
+ * called with a \ref LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED for all devices
+ * already plugged into the machine. Note that libusb modifies its internal
+ * device list from a separate thread, while calling hotplug callbacks from
+ * libusb_handle_events(), so it is possible for a device to already be present
+ * on, or removed from, its internal device list, while the hotplug callbacks
+ * still need to be dispatched. This means that when using \ref
+ * LIBUSB_HOTPLUG_ENUMERATE, your callback may be called twice for the arrival
+ * of the same device, once from libusb_hotplug_register_callback() and once
+ * from libusb_handle_events(); and/or your callback may be called for the
+ * removal of a device for which an arrived call was never made.
+ *
+ * Since version 1.0.16, \ref LIBUSB_API_VERSION >= 0x01000102
+ *
+ * \param[in] ctx context to register this callback with
+ * \param[in] events bitwise or of events that will trigger this callback. See \ref
+ *            libusb_hotplug_event
+ * \param[in] flags hotplug callback flags. See \ref libusb_hotplug_flag
+ * \param[in] vendor_id the vendor id to match or \ref LIBUSB_HOTPLUG_MATCH_ANY
+ * \param[in] product_id the product id to match or \ref LIBUSB_HOTPLUG_MATCH_ANY
+ * \param[in] dev_class the device class to match or \ref LIBUSB_HOTPLUG_MATCH_ANY
+ * \param[in] cb_fn the function to be invoked on a matching event/device
+ * \param[in] user_data user data to pass to the callback function
+ * \param[out] callback_handle pointer to store the handle of the allocated callback (can be NULL)
+ * \returns LIBUSB_SUCCESS on success LIBUSB_ERROR code on failure
+ */
+int LIBUSB_CALL libusb_hotplug_register_callback(libusb_context *ctx,
+						libusb_hotplug_event events,
+						libusb_hotplug_flag flags,
+						int vendor_id, int product_id,
+						int dev_class,
+						libusb_hotplug_callback_fn cb_fn,
+						void *user_data,
+						libusb_hotplug_callback_handle *callback_handle);
+
+/** \ingroup libusb_hotplug
+ * Deregisters a hotplug callback.
+ *
+ * Deregister a callback from a libusb_context. This function is safe to call from within
+ * a hotplug callback.
+ *
+ * Since version 1.0.16, \ref LIBUSB_API_VERSION >= 0x01000102
+ *
+ * \param[in] ctx context this callback is registered with
+ * \param[in] callback_handle the handle of the callback to deregister
+ */
+void LIBUSB_CALL libusb_hotplug_deregister_callback(libusb_context *ctx,
+						libusb_hotplug_callback_handle callback_handle);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/libusbi.h b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/libusbi.h
new file mode 100644
index 000000000..752e39887
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/libusbi.h
@@ -0,0 +1,1149 @@
+/*
+ * Internal header for libusb
+ * Copyright © 2007-2009 Daniel Drake <dsd@gentoo.org>
+ * Copyright © 2001 Johannes Erdfelt <johannes@erdfelt.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef LIBUSBI_H
+#define LIBUSBI_H
+
+#include <config.h>
+
+#include <stdlib.h>
+
+#include <stddef.h>
+#include <stdint.h>
+#include <time.h>
+#include <stdarg.h>
+#ifdef HAVE_POLL_H
+#include <poll.h>
+#endif
+#ifdef HAVE_MISSING_H
+#include <missing.h>
+#endif
+
+#include "libusb.h"
+#include "version.h"
+
+/* Inside the libusb code, mark all public functions as follows:
+ *   return_type API_EXPORTED function_name(params) { ... }
+ * But if the function returns a pointer, mark it as follows:
+ *   DEFAULT_VISIBILITY return_type * LIBUSB_CALL function_name(params) { ... }
+ * In the libusb public header, mark all declarations as:
+ *   return_type LIBUSB_CALL function_name(params);
+ */
+#define API_EXPORTED LIBUSB_CALL DEFAULT_VISIBILITY
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define DEVICE_DESC_LENGTH	18
+
+#define USB_MAXENDPOINTS	32
+#define USB_MAXINTERFACES	32
+#define USB_MAXCONFIG		8
+
+/* Backend specific capabilities */
+#define USBI_CAP_HAS_HID_ACCESS			0x00010000
+#define USBI_CAP_SUPPORTS_DETACH_KERNEL_DRIVER	0x00020000
+
+/* Maximum number of bytes in a log line */
+#define USBI_MAX_LOG_LEN	1024
+/* Terminator for log lines */
+#define USBI_LOG_LINE_END	"\n"
+
+/* The following is used to silence warnings for unused variables */
+#define UNUSED(var)		do { (void)(var); } while(0)
+
+#if !defined(ARRAYSIZE)
+#define ARRAYSIZE(array) (sizeof(array) / sizeof(array[0]))
+#endif
+
+struct list_head {
+	struct list_head *prev, *next;
+};
+
+/* Get an entry from the list
+ *  ptr - the address of this list_head element in "type"
+ *  type - the data type that contains "member"
+ *  member - the list_head element in "type"
+ */
+#define list_entry(ptr, type, member) \
+	((type *)((uintptr_t)(ptr) - (uintptr_t)offsetof(type, member)))
+
+#define list_first_entry(ptr, type, member) \
+	list_entry((ptr)->next, type, member)
+
+/* Get each entry from a list
+ *  pos - A structure pointer has a "member" element
+ *  head - list head
+ *  member - the list_head element in "pos"
+ *  type - the type of the first parameter
+ */
+#define list_for_each_entry(pos, head, member, type)			\
+	for (pos = list_entry((head)->next, type, member);		\
+		 &pos->member != (head);				\
+		 pos = list_entry(pos->member.next, type, member))
+
+#define list_for_each_entry_safe(pos, n, head, member, type)		\
+	for (pos = list_entry((head)->next, type, member),		\
+		 n = list_entry(pos->member.next, type, member);	\
+		 &pos->member != (head);				\
+		 pos = n, n = list_entry(n->member.next, type, member))
+
+#define list_empty(entry) ((entry)->next == (entry))
+
+static inline void list_init(struct list_head *entry)
+{
+	entry->prev = entry->next = entry;
+}
+
+static inline void list_add(struct list_head *entry, struct list_head *head)
+{
+	entry->next = head->next;
+	entry->prev = head;
+
+	head->next->prev = entry;
+	head->next = entry;
+}
+
+static inline void list_add_tail(struct list_head *entry,
+	struct list_head *head)
+{
+	entry->next = head;
+	entry->prev = head->prev;
+
+	head->prev->next = entry;
+	head->prev = entry;
+}
+
+static inline void list_del(struct list_head *entry)
+{
+	entry->next->prev = entry->prev;
+	entry->prev->next = entry->next;
+	entry->next = entry->prev = NULL;
+}
+
+static inline void *usbi_reallocf(void *ptr, size_t size)
+{
+	void *ret = realloc(ptr, size);
+	if (!ret)
+		free(ptr);
+	return ret;
+}
+
+#define container_of(ptr, type, member) ({			\
+	const typeof( ((type *)0)->member ) *mptr = (ptr);	\
+	(type *)( (char *)mptr - offsetof(type,member) );})
+
+#ifndef MIN
+#define MIN(a, b)	((a) < (b) ? (a) : (b))
+#endif
+#ifndef MAX
+#define MAX(a, b)	((a) > (b) ? (a) : (b))
+#endif
+
+#define TIMESPEC_IS_SET(ts) ((ts)->tv_sec != 0 || (ts)->tv_nsec != 0)
+
+#if defined(_WIN32) || defined(__CYGWIN__) || defined(_WIN32_WCE)
+#define TIMEVAL_TV_SEC_TYPE	long
+#else
+#define TIMEVAL_TV_SEC_TYPE	time_t
+#endif
+
+/* Some platforms don't have this define */
+#ifndef TIMESPEC_TO_TIMEVAL
+#define TIMESPEC_TO_TIMEVAL(tv, ts)					\
+	do {								\
+		(tv)->tv_sec = (TIMEVAL_TV_SEC_TYPE) (ts)->tv_sec;	\
+		(tv)->tv_usec = (ts)->tv_nsec / 1000;			\
+	} while (0)
+#endif
+
+void usbi_log(struct libusb_context *ctx, enum libusb_log_level level,
+	const char *function, const char *format, ...);
+
+void usbi_log_v(struct libusb_context *ctx, enum libusb_log_level level,
+	const char *function, const char *format, va_list args);
+
+#if !defined(_MSC_VER) || _MSC_VER >= 1400
+
+#ifdef ENABLE_LOGGING
+#define _usbi_log(ctx, level, ...) usbi_log(ctx, level, __FUNCTION__, __VA_ARGS__)
+#define usbi_dbg(...) _usbi_log(NULL, LIBUSB_LOG_LEVEL_DEBUG, __VA_ARGS__)
+#else
+#define _usbi_log(ctx, level, ...) do { (void)(ctx); } while(0)
+#define usbi_dbg(...) do {} while(0)
+#endif
+
+#define usbi_info(ctx, ...) _usbi_log(ctx, LIBUSB_LOG_LEVEL_INFO, __VA_ARGS__)
+#define usbi_warn(ctx, ...) _usbi_log(ctx, LIBUSB_LOG_LEVEL_WARNING, __VA_ARGS__)
+#define usbi_err(ctx, ...) _usbi_log(ctx, LIBUSB_LOG_LEVEL_ERROR, __VA_ARGS__)
+
+#else /* !defined(_MSC_VER) || _MSC_VER >= 1400 */
+
+#ifdef ENABLE_LOGGING
+#define LOG_BODY(ctxt, level)				\
+{							\
+	va_list args;					\
+	va_start(args, format);				\
+	usbi_log_v(ctxt, level, "", format, args);	\
+	va_end(args);					\
+}
+#else
+#define LOG_BODY(ctxt, level)				\
+{							\
+	(void)(ctxt);					\
+}
+#endif
+
+static inline void usbi_info(struct libusb_context *ctx, const char *format, ...)
+	LOG_BODY(ctx, LIBUSB_LOG_LEVEL_INFO)
+static inline void usbi_warn(struct libusb_context *ctx, const char *format, ...)
+	LOG_BODY(ctx, LIBUSB_LOG_LEVEL_WARNING)
+static inline void usbi_err(struct libusb_context *ctx, const char *format, ...)
+	LOG_BODY(ctx, LIBUSB_LOG_LEVEL_ERROR)
+
+static inline void usbi_dbg(const char *format, ...)
+	LOG_BODY(NULL, LIBUSB_LOG_LEVEL_DEBUG)
+
+#endif /* !defined(_MSC_VER) || _MSC_VER >= 1400 */
+
+#define USBI_GET_CONTEXT(ctx)				\
+	do {						\
+		if (!(ctx))				\
+			(ctx) = usbi_default_context;	\
+	} while(0)
+
+#define DEVICE_CTX(dev)		((dev)->ctx)
+#define HANDLE_CTX(handle)	(DEVICE_CTX((handle)->dev))
+#define TRANSFER_CTX(transfer)	(HANDLE_CTX((transfer)->dev_handle))
+#define ITRANSFER_CTX(transfer) \
+	(TRANSFER_CTX(USBI_TRANSFER_TO_LIBUSB_TRANSFER(transfer)))
+
+#define IS_EPIN(ep)		(0 != ((ep) & LIBUSB_ENDPOINT_IN))
+#define IS_EPOUT(ep)		(!IS_EPIN(ep))
+#define IS_XFERIN(xfer)		(0 != ((xfer)->endpoint & LIBUSB_ENDPOINT_IN))
+#define IS_XFEROUT(xfer)	(!IS_XFERIN(xfer))
+
+/* Internal abstraction for thread synchronization */
+#if defined(THREADS_POSIX)
+#include "os/threads_posix.h"
+#elif defined(OS_WINDOWS) || defined(OS_WINCE)
+#include "os/threads_windows.h"
+#endif
+
+extern struct libusb_context *usbi_default_context;
+
+/* Forward declaration for use in context (fully defined inside poll abstraction) */
+struct pollfd;
+
+struct libusb_context {
+	int debug;
+	int debug_fixed;
+
+	/* internal event pipe, used for signalling occurrence of an internal event. */
+	int event_pipe[2];
+
+	struct list_head usb_devs;
+	usbi_mutex_t usb_devs_lock;
+
+	/* A list of open handles. Backends are free to traverse this if required.
+	 */
+	struct list_head open_devs;
+	usbi_mutex_t open_devs_lock;
+
+	/* A list of registered hotplug callbacks */
+	struct list_head hotplug_cbs;
+	usbi_mutex_t hotplug_cbs_lock;
+
+	/* this is a list of in-flight transfer handles, sorted by timeout
+	 * expiration. URBs to timeout the soonest are placed at the beginning of
+	 * the list, URBs that will time out later are placed after, and urbs with
+	 * infinite timeout are always placed at the very end. */
+	struct list_head flying_transfers;
+	/* Note paths taking both this and usbi_transfer->lock must always
+	 * take this lock first */
+	usbi_mutex_t flying_transfers_lock;
+
+	/* user callbacks for pollfd changes */
+	libusb_pollfd_added_cb fd_added_cb;
+	libusb_pollfd_removed_cb fd_removed_cb;
+	void *fd_cb_user_data;
+
+	/* ensures that only one thread is handling events at any one time */
+	usbi_mutex_t events_lock;
+
+	/* used to see if there is an active thread doing event handling */
+	int event_handler_active;
+
+	/* A thread-local storage key to track which thread is performing event
+	 * handling */
+	usbi_tls_key_t event_handling_key;
+
+	/* used to wait for event completion in threads other than the one that is
+	 * event handling */
+	usbi_mutex_t event_waiters_lock;
+	usbi_cond_t event_waiters_cond;
+
+	/* A lock to protect internal context event data. */
+	usbi_mutex_t event_data_lock;
+
+	/* A bitmask of flags that are set to indicate specific events that need to
+	 * be handled. Protected by event_data_lock. */
+	unsigned int event_flags;
+
+	/* A counter that is set when we want to interrupt and prevent event handling,
+	 * in order to safely close a device. Protected by event_data_lock. */
+	unsigned int device_close;
+
+	/* list and count of poll fds and an array of poll fd structures that is
+	 * (re)allocated as necessary prior to polling. Protected by event_data_lock. */
+	struct list_head ipollfds;
+	struct pollfd *pollfds;
+	POLL_NFDS_TYPE pollfds_cnt;
+
+	/* A list of pending hotplug messages. Protected by event_data_lock. */
+	struct list_head hotplug_msgs;
+
+	/* A list of pending completed transfers. Protected by event_data_lock. */
+	struct list_head completed_transfers;
+
+#ifdef USBI_TIMERFD_AVAILABLE
+	/* used for timeout handling, if supported by OS.
+	 * this timerfd is maintained to trigger on the next pending timeout */
+	int timerfd;
+#endif
+
+	struct list_head list;
+};
+
+enum usbi_event_flags {
+	/* The list of pollfds has been modified */
+	USBI_EVENT_POLLFDS_MODIFIED = 1 << 0,
+
+	/* The user has interrupted the event handler */
+	USBI_EVENT_USER_INTERRUPT = 1 << 1,
+};
+
+/* Macros for managing event handling state */
+#define usbi_handling_events(ctx) \
+	(usbi_tls_key_get((ctx)->event_handling_key) != NULL)
+
+#define usbi_start_event_handling(ctx) \
+	usbi_tls_key_set((ctx)->event_handling_key, ctx)
+
+#define usbi_end_event_handling(ctx) \
+	usbi_tls_key_set((ctx)->event_handling_key, NULL)
+
+/* Update the following macro if new event sources are added */
+#define usbi_pending_events(ctx) \
+	((ctx)->event_flags || (ctx)->device_close \
+	 || !list_empty(&(ctx)->hotplug_msgs) || !list_empty(&(ctx)->completed_transfers))
+
+#ifdef USBI_TIMERFD_AVAILABLE
+#define usbi_using_timerfd(ctx) ((ctx)->timerfd >= 0)
+#else
+#define usbi_using_timerfd(ctx) (0)
+#endif
+
+struct libusb_device {
+	/* lock protects refcnt, everything else is finalized at initialization
+	 * time */
+	usbi_mutex_t lock;
+	int refcnt;
+
+	struct libusb_context *ctx;
+
+	uint8_t bus_number;
+	uint8_t port_number;
+	struct libusb_device* parent_dev;
+	uint8_t device_address;
+	uint8_t num_configurations;
+	enum libusb_speed speed;
+
+	struct list_head list;
+	unsigned long session_data;
+
+	struct libusb_device_descriptor device_descriptor;
+	int attached;
+
+	unsigned char os_priv
+#if defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L)
+	[] /* valid C99 code */
+#else
+	[0] /* non-standard, but usually working code */
+#endif
+#if defined(OS_SUNOS)
+	__attribute__ ((aligned (8)));
+#else
+	;
+#endif
+};
+
+struct libusb_device_handle {
+	/* lock protects claimed_interfaces */
+	usbi_mutex_t lock;
+	unsigned long claimed_interfaces;
+
+	struct list_head list;
+	struct libusb_device *dev;
+	int auto_detach_kernel_driver;
+	unsigned char os_priv
+#if defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L)
+	[] /* valid C99 code */
+#else
+	[0] /* non-standard, but usually working code */
+#endif
+#if defined(OS_SUNOS)
+	__attribute__ ((aligned (8)));
+#else
+	;
+#endif
+};
+
+enum {
+	USBI_CLOCK_MONOTONIC,
+	USBI_CLOCK_REALTIME
+};
+
+/* in-memory transfer layout:
+ *
+ * 1. struct usbi_transfer
+ * 2. struct libusb_transfer (which includes iso packets) [variable size]
+ * 3. os private data [variable size]
+ *
+ * from a libusb_transfer, you can get the usbi_transfer by rewinding the
+ * appropriate number of bytes.
+ * the usbi_transfer includes the number of allocated packets, so you can
+ * determine the size of the transfer and hence the start and length of the
+ * OS-private data.
+ */
+
+struct usbi_transfer {
+	int num_iso_packets;
+	struct list_head list;
+	struct list_head completed_list;
+	struct timeval timeout;
+	int transferred;
+	uint32_t stream_id;
+	uint8_t state_flags;   /* Protected by usbi_transfer->lock */
+	uint8_t timeout_flags; /* Protected by the flying_stransfers_lock */
+
+	/* this lock is held during libusb_submit_transfer() and
+	 * libusb_cancel_transfer() (allowing the OS backend to prevent duplicate
+	 * cancellation, submission-during-cancellation, etc). the OS backend
+	 * should also take this lock in the handle_events path, to prevent the user
+	 * cancelling the transfer from another thread while you are processing
+	 * its completion (presumably there would be races within your OS backend
+	 * if this were possible).
+	 * Note paths taking both this and the flying_transfers_lock must
+	 * always take the flying_transfers_lock first */
+	usbi_mutex_t lock;
+};
+
+enum usbi_transfer_state_flags {
+	/* Transfer successfully submitted by backend */
+	USBI_TRANSFER_IN_FLIGHT = 1 << 0,
+
+	/* Cancellation was requested via libusb_cancel_transfer() */
+	USBI_TRANSFER_CANCELLING = 1 << 1,
+
+	/* Operation on the transfer failed because the device disappeared */
+	USBI_TRANSFER_DEVICE_DISAPPEARED = 1 << 2,
+};
+
+enum usbi_transfer_timeout_flags {
+	/* Set by backend submit_transfer() if the OS handles timeout */
+	USBI_TRANSFER_OS_HANDLES_TIMEOUT = 1 << 0,
+
+	/* The transfer timeout has been handled */
+	USBI_TRANSFER_TIMEOUT_HANDLED = 1 << 1,
+
+	/* The transfer timeout was successfully processed */
+	USBI_TRANSFER_TIMED_OUT = 1 << 2,
+};
+
+#define USBI_TRANSFER_TO_LIBUSB_TRANSFER(transfer)			\
+	((struct libusb_transfer *)(((unsigned char *)(transfer))	\
+		+ sizeof(struct usbi_transfer)))
+#define LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer)			\
+	((struct usbi_transfer *)(((unsigned char *)(transfer))		\
+		- sizeof(struct usbi_transfer)))
+
+static inline void *usbi_transfer_get_os_priv(struct usbi_transfer *transfer)
+{
+	return ((unsigned char *)transfer) + sizeof(struct usbi_transfer)
+		+ sizeof(struct libusb_transfer)
+		+ (transfer->num_iso_packets
+			* sizeof(struct libusb_iso_packet_descriptor));
+}
+
+/* bus structures */
+
+/* All standard descriptors have these 2 fields in common */
+struct usb_descriptor_header {
+	uint8_t bLength;
+	uint8_t bDescriptorType;
+};
+
+/* shared data and functions */
+
+int usbi_io_init(struct libusb_context *ctx);
+void usbi_io_exit(struct libusb_context *ctx);
+
+struct libusb_device *usbi_alloc_device(struct libusb_context *ctx,
+	unsigned long session_id);
+struct libusb_device *usbi_get_device_by_session_id(struct libusb_context *ctx,
+	unsigned long session_id);
+int usbi_sanitize_device(struct libusb_device *dev);
+void usbi_handle_disconnect(struct libusb_device_handle *dev_handle);
+
+int usbi_handle_transfer_completion(struct usbi_transfer *itransfer,
+	enum libusb_transfer_status status);
+int usbi_handle_transfer_cancellation(struct usbi_transfer *transfer);
+void usbi_signal_transfer_completion(struct usbi_transfer *transfer);
+
+int usbi_parse_descriptor(const unsigned char *source, const char *descriptor,
+	void *dest, int host_endian);
+int usbi_device_cache_descriptor(libusb_device *dev);
+int usbi_get_config_index_by_value(struct libusb_device *dev,
+	uint8_t bConfigurationValue, int *idx);
+
+void usbi_connect_device (struct libusb_device *dev);
+void usbi_disconnect_device (struct libusb_device *dev);
+
+int usbi_signal_event(struct libusb_context *ctx);
+int usbi_clear_event(struct libusb_context *ctx);
+
+/* Internal abstraction for poll (needs struct usbi_transfer on Windows) */
+#if defined(OS_LINUX) || defined(OS_DARWIN) || defined(OS_OPENBSD) || defined(OS_NETBSD) ||\
+	defined(OS_HAIKU) || defined(OS_SUNOS)
+#include <unistd.h>
+#include "os/poll_posix.h"
+#elif defined(OS_WINDOWS) || defined(OS_WINCE)
+#include "os/poll_windows.h"
+#endif
+
+#if defined(_MSC_VER) && (_MSC_VER < 1900)
+#define snprintf usbi_snprintf
+#define vsnprintf usbi_vsnprintf
+int usbi_snprintf(char *dst, size_t size, const char *format, ...);
+int usbi_vsnprintf(char *dst, size_t size, const char *format, va_list ap);
+#define LIBUSB_PRINTF_WIN32
+#endif
+
+struct usbi_pollfd {
+	/* must come first */
+	struct libusb_pollfd pollfd;
+
+	struct list_head list;
+};
+
+int usbi_add_pollfd(struct libusb_context *ctx, int fd, short events);
+void usbi_remove_pollfd(struct libusb_context *ctx, int fd);
+
+/* device discovery */
+
+/* we traverse usbfs without knowing how many devices we are going to find.
+ * so we create this discovered_devs model which is similar to a linked-list
+ * which grows when required. it can be freed once discovery has completed,
+ * eliminating the need for a list node in the libusb_device structure
+ * itself. */
+struct discovered_devs {
+	size_t len;
+	size_t capacity;
+	struct libusb_device *devices
+#if defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L)
+	[] /* valid C99 code */
+#else
+	[0] /* non-standard, but usually working code */
+#endif
+	;
+};
+
+struct discovered_devs *discovered_devs_append(
+	struct discovered_devs *discdevs, struct libusb_device *dev);
+
+/* OS abstraction */
+
+/* This is the interface that OS backends need to implement.
+ * All fields are mandatory, except ones explicitly noted as optional. */
+struct usbi_os_backend {
+	/* A human-readable name for your backend, e.g. "Linux usbfs" */
+	const char *name;
+
+	/* Binary mask for backend specific capabilities */
+	uint32_t caps;
+
+	/* Perform initialization of your backend. You might use this function
+	 * to determine specific capabilities of the system, allocate required
+	 * data structures for later, etc.
+	 *
+	 * This function is called when a libusb user initializes the library
+	 * prior to use.
+	 *
+	 * Return 0 on success, or a LIBUSB_ERROR code on failure.
+	 */
+	int (*init)(struct libusb_context *ctx);
+
+	/* Deinitialization. Optional. This function should destroy anything
+	 * that was set up by init.
+	 *
+	 * This function is called when the user deinitializes the library.
+	 */
+	void (*exit)(void);
+
+	/* Enumerate all the USB devices on the system, returning them in a list
+	 * of discovered devices.
+	 *
+	 * Your implementation should enumerate all devices on the system,
+	 * regardless of whether they have been seen before or not.
+	 *
+	 * When you have found a device, compute a session ID for it. The session
+	 * ID should uniquely represent that particular device for that particular
+	 * connection session since boot (i.e. if you disconnect and reconnect a
+	 * device immediately after, it should be assigned a different session ID).
+	 * If your OS cannot provide a unique session ID as described above,
+	 * presenting a session ID of (bus_number << 8 | device_address) should
+	 * be sufficient. Bus numbers and device addresses wrap and get reused,
+	 * but that is an unlikely case.
+	 *
+	 * After computing a session ID for a device, call
+	 * usbi_get_device_by_session_id(). This function checks if libusb already
+	 * knows about the device, and if so, it provides you with a reference
+	 * to a libusb_device structure for it.
+	 *
+	 * If usbi_get_device_by_session_id() returns NULL, it is time to allocate
+	 * a new device structure for the device. Call usbi_alloc_device() to
+	 * obtain a new libusb_device structure with reference count 1. Populate
+	 * the bus_number and device_address attributes of the new device, and
+	 * perform any other internal backend initialization you need to do. At
+	 * this point, you should be ready to provide device descriptors and so
+	 * on through the get_*_descriptor functions. Finally, call
+	 * usbi_sanitize_device() to perform some final sanity checks on the
+	 * device. Assuming all of the above succeeded, we can now continue.
+	 * If any of the above failed, remember to unreference the device that
+	 * was returned by usbi_alloc_device().
+	 *
+	 * At this stage we have a populated libusb_device structure (either one
+	 * that was found earlier, or one that we have just allocated and
+	 * populated). This can now be added to the discovered devices list
+	 * using discovered_devs_append(). Note that discovered_devs_append()
+	 * may reallocate the list, returning a new location for it, and also
+	 * note that reallocation can fail. Your backend should handle these
+	 * error conditions appropriately.
+	 *
+	 * This function should not generate any bus I/O and should not block.
+	 * If I/O is required (e.g. reading the active configuration value), it is
+	 * OK to ignore these suggestions :)
+	 *
+	 * This function is executed when the user wishes to retrieve a list
+	 * of USB devices connected to the system.
+	 *
+	 * If the backend has hotplug support, this function is not used!
+	 *
+	 * Return 0 on success, or a LIBUSB_ERROR code on failure.
+	 */
+	int (*get_device_list)(struct libusb_context *ctx,
+		struct discovered_devs **discdevs);
+
+	/* Apps which were written before hotplug support, may listen for
+	 * hotplug events on their own and call libusb_get_device_list on
+	 * device addition. In this case libusb_get_device_list will likely
+	 * return a list without the new device in there, as the hotplug
+	 * event thread will still be busy enumerating the device, which may
+	 * take a while, or may not even have seen the event yet.
+	 *
+	 * To avoid this libusb_get_device_list will call this optional
+	 * function for backends with hotplug support before copying
+	 * ctx->usb_devs to the user. In this function the backend should
+	 * ensure any pending hotplug events are fully processed before
+	 * returning.
+	 *
+	 * Optional, should be implemented by backends with hotplug support.
+	 */
+	void (*hotplug_poll)(void);
+
+	/* Open a device for I/O and other USB operations. The device handle
+	 * is preallocated for you, you can retrieve the device in question
+	 * through handle->dev.
+	 *
+	 * Your backend should allocate any internal resources required for I/O
+	 * and other operations so that those operations can happen (hopefully)
+	 * without hiccup. This is also a good place to inform libusb that it
+	 * should monitor certain file descriptors related to this device -
+	 * see the usbi_add_pollfd() function.
+	 *
+	 * This function should not generate any bus I/O and should not block.
+	 *
+	 * This function is called when the user attempts to obtain a device
+	 * handle for a device.
+	 *
+	 * Return:
+	 * - 0 on success
+	 * - LIBUSB_ERROR_ACCESS if the user has insufficient permissions
+	 * - LIBUSB_ERROR_NO_DEVICE if the device has been disconnected since
+	 *   discovery
+	 * - another LIBUSB_ERROR code on other failure
+	 *
+	 * Do not worry about freeing the handle on failed open, the upper layers
+	 * do this for you.
+	 */
+	int (*open)(struct libusb_device_handle *dev_handle);
+
+	/* Close a device such that the handle cannot be used again. Your backend
+	 * should destroy any resources that were allocated in the open path.
+	 * This may also be a good place to call usbi_remove_pollfd() to inform
+	 * libusb of any file descriptors associated with this device that should
+	 * no longer be monitored.
+	 *
+	 * This function is called when the user closes a device handle.
+	 */
+	void (*close)(struct libusb_device_handle *dev_handle);
+
+	/* Retrieve the device descriptor from a device.
+	 *
+	 * The descriptor should be retrieved from memory, NOT via bus I/O to the
+	 * device. This means that you may have to cache it in a private structure
+	 * during get_device_list enumeration. Alternatively, you may be able
+	 * to retrieve it from a kernel interface (some Linux setups can do this)
+	 * still without generating bus I/O.
+	 *
+	 * This function is expected to write DEVICE_DESC_LENGTH (18) bytes into
+	 * buffer, which is guaranteed to be big enough.
+	 *
+	 * This function is called when sanity-checking a device before adding
+	 * it to the list of discovered devices, and also when the user requests
+	 * to read the device descriptor.
+	 *
+	 * This function is expected to return the descriptor in bus-endian format
+	 * (LE). If it returns the multi-byte values in host-endian format,
+	 * set the host_endian output parameter to "1".
+	 *
+	 * Return 0 on success or a LIBUSB_ERROR code on failure.
+	 */
+	int (*get_device_descriptor)(struct libusb_device *device,
+		unsigned char *buffer, int *host_endian);
+
+	/* Get the ACTIVE configuration descriptor for a device.
+	 *
+	 * The descriptor should be retrieved from memory, NOT via bus I/O to the
+	 * device. This means that you may have to cache it in a private structure
+	 * during get_device_list enumeration. You may also have to keep track
+	 * of which configuration is active when the user changes it.
+	 *
+	 * This function is expected to write len bytes of data into buffer, which
+	 * is guaranteed to be big enough. If you can only do a partial write,
+	 * return an error code.
+	 *
+	 * This function is expected to return the descriptor in bus-endian format
+	 * (LE). If it returns the multi-byte values in host-endian format,
+	 * set the host_endian output parameter to "1".
+	 *
+	 * Return:
+	 * - 0 on success
+	 * - LIBUSB_ERROR_NOT_FOUND if the device is in unconfigured state
+	 * - another LIBUSB_ERROR code on other failure
+	 */
+	int (*get_active_config_descriptor)(struct libusb_device *device,
+		unsigned char *buffer, size_t len, int *host_endian);
+
+	/* Get a specific configuration descriptor for a device.
+	 *
+	 * The descriptor should be retrieved from memory, NOT via bus I/O to the
+	 * device. This means that you may have to cache it in a private structure
+	 * during get_device_list enumeration.
+	 *
+	 * The requested descriptor is expressed as a zero-based index (i.e. 0
+	 * indicates that we are requesting the first descriptor). The index does
+	 * not (necessarily) equal the bConfigurationValue of the configuration
+	 * being requested.
+	 *
+	 * This function is expected to write len bytes of data into buffer, which
+	 * is guaranteed to be big enough. If you can only do a partial write,
+	 * return an error code.
+	 *
+	 * This function is expected to return the descriptor in bus-endian format
+	 * (LE). If it returns the multi-byte values in host-endian format,
+	 * set the host_endian output parameter to "1".
+	 *
+	 * Return the length read on success or a LIBUSB_ERROR code on failure.
+	 */
+	int (*get_config_descriptor)(struct libusb_device *device,
+		uint8_t config_index, unsigned char *buffer, size_t len,
+		int *host_endian);
+
+	/* Like get_config_descriptor but then by bConfigurationValue instead
+	 * of by index.
+	 *
+	 * Optional, if not present the core will call get_config_descriptor
+	 * for all configs until it finds the desired bConfigurationValue.
+	 *
+	 * Returns a pointer to the raw-descriptor in *buffer, this memory
+	 * is valid as long as device is valid.
+	 *
+	 * Returns the length of the returned raw-descriptor on success,
+	 * or a LIBUSB_ERROR code on failure.
+	 */
+	int (*get_config_descriptor_by_value)(struct libusb_device *device,
+		uint8_t bConfigurationValue, unsigned char **buffer,
+		int *host_endian);
+
+	/* Get the bConfigurationValue for the active configuration for a device.
+	 * Optional. This should only be implemented if you can retrieve it from
+	 * cache (don't generate I/O).
+	 *
+	 * If you cannot retrieve this from cache, either do not implement this
+	 * function, or return LIBUSB_ERROR_NOT_SUPPORTED. This will cause
+	 * libusb to retrieve the information through a standard control transfer.
+	 *
+	 * This function must be non-blocking.
+	 * Return:
+	 * - 0 on success
+	 * - LIBUSB_ERROR_NO_DEVICE if the device has been disconnected since it
+	 *   was opened
+	 * - LIBUSB_ERROR_NOT_SUPPORTED if the value cannot be retrieved without
+	 *   blocking
+	 * - another LIBUSB_ERROR code on other failure.
+	 */
+	int (*get_configuration)(struct libusb_device_handle *dev_handle, int *config);
+
+	/* Set the active configuration for a device.
+	 *
+	 * A configuration value of -1 should put the device in unconfigured state.
+	 *
+	 * This function can block.
+	 *
+	 * Return:
+	 * - 0 on success
+	 * - LIBUSB_ERROR_NOT_FOUND if the configuration does not exist
+	 * - LIBUSB_ERROR_BUSY if interfaces are currently claimed (and hence
+	 *   configuration cannot be changed)
+	 * - LIBUSB_ERROR_NO_DEVICE if the device has been disconnected since it
+	 *   was opened
+	 * - another LIBUSB_ERROR code on other failure.
+	 */
+	int (*set_configuration)(struct libusb_device_handle *dev_handle, int config);
+
+	/* Claim an interface. When claimed, the application can then perform
+	 * I/O to an interface's endpoints.
+	 *
+	 * This function should not generate any bus I/O and should not block.
+	 * Interface claiming is a logical operation that simply ensures that
+	 * no other drivers/applications are using the interface, and after
+	 * claiming, no other drivers/applications can use the interface because
+	 * we now "own" it.
+	 *
+	 * Return:
+	 * - 0 on success
+	 * - LIBUSB_ERROR_NOT_FOUND if the interface does not exist
+	 * - LIBUSB_ERROR_BUSY if the interface is in use by another driver/app
+	 * - LIBUSB_ERROR_NO_DEVICE if the device has been disconnected since it
+	 *   was opened
+	 * - another LIBUSB_ERROR code on other failure
+	 */
+	int (*claim_interface)(struct libusb_device_handle *dev_handle, int interface_number);
+
+	/* Release a previously claimed interface.
+	 *
+	 * This function should also generate a SET_INTERFACE control request,
+	 * resetting the alternate setting of that interface to 0. It's OK for
+	 * this function to block as a result.
+	 *
+	 * You will only ever be asked to release an interface which was
+	 * successfully claimed earlier.
+	 *
+	 * Return:
+	 * - 0 on success
+	 * - LIBUSB_ERROR_NO_DEVICE if the device has been disconnected since it
+	 *   was opened
+	 * - another LIBUSB_ERROR code on other failure
+	 */
+	int (*release_interface)(struct libusb_device_handle *dev_handle, int interface_number);
+
+	/* Set the alternate setting for an interface.
+	 *
+	 * You will only ever be asked to set the alternate setting for an
+	 * interface which was successfully claimed earlier.
+	 *
+	 * It's OK for this function to block.
+	 *
+	 * Return:
+	 * - 0 on success
+	 * - LIBUSB_ERROR_NOT_FOUND if the alternate setting does not exist
+	 * - LIBUSB_ERROR_NO_DEVICE if the device has been disconnected since it
+	 *   was opened
+	 * - another LIBUSB_ERROR code on other failure
+	 */
+	int (*set_interface_altsetting)(struct libusb_device_handle *dev_handle,
+		int interface_number, int altsetting);
+
+	/* Clear a halt/stall condition on an endpoint.
+	 *
+	 * It's OK for this function to block.
+	 *
+	 * Return:
+	 * - 0 on success
+	 * - LIBUSB_ERROR_NOT_FOUND if the endpoint does not exist
+	 * - LIBUSB_ERROR_NO_DEVICE if the device has been disconnected since it
+	 *   was opened
+	 * - another LIBUSB_ERROR code on other failure
+	 */
+	int (*clear_halt)(struct libusb_device_handle *dev_handle,
+		unsigned char endpoint);
+
+	/* Perform a USB port reset to reinitialize a device.
+	 *
+	 * If possible, the device handle should still be usable after the reset
+	 * completes, assuming that the device descriptors did not change during
+	 * reset and all previous interface state can be restored.
+	 *
+	 * If something changes, or you cannot easily locate/verify the resetted
+	 * device, return LIBUSB_ERROR_NOT_FOUND. This prompts the application
+	 * to close the old handle and re-enumerate the device.
+	 *
+	 * Return:
+	 * - 0 on success
+	 * - LIBUSB_ERROR_NOT_FOUND if re-enumeration is required, or if the device
+	 *   has been disconnected since it was opened
+	 * - another LIBUSB_ERROR code on other failure
+	 */
+	int (*reset_device)(struct libusb_device_handle *dev_handle);
+
+	/* Alloc num_streams usb3 bulk streams on the passed in endpoints */
+	int (*alloc_streams)(struct libusb_device_handle *dev_handle,
+		uint32_t num_streams, unsigned char *endpoints, int num_endpoints);
+
+	/* Free usb3 bulk streams allocated with alloc_streams */
+	int (*free_streams)(struct libusb_device_handle *dev_handle,
+		unsigned char *endpoints, int num_endpoints);
+
+	/* Allocate persistent DMA memory for the given device, suitable for
+	 * zerocopy. May return NULL on failure. Optional to implement.
+	 */
+	unsigned char *(*dev_mem_alloc)(struct libusb_device_handle *handle,
+		size_t len);
+
+	/* Free memory allocated by dev_mem_alloc. */
+	int (*dev_mem_free)(struct libusb_device_handle *handle,
+		unsigned char *buffer, size_t len);
+
+	/* Determine if a kernel driver is active on an interface. Optional.
+	 *
+	 * The presence of a kernel driver on an interface indicates that any
+	 * calls to claim_interface would fail with the LIBUSB_ERROR_BUSY code.
+	 *
+	 * Return:
+	 * - 0 if no driver is active
+	 * - 1 if a driver is active
+	 * - LIBUSB_ERROR_NO_DEVICE if the device has been disconnected since it
+	 *   was opened
+	 * - another LIBUSB_ERROR code on other failure
+	 */
+	int (*kernel_driver_active)(struct libusb_device_handle *dev_handle,
+		int interface_number);
+
+	/* Detach a kernel driver from an interface. Optional.
+	 *
+	 * After detaching a kernel driver, the interface should be available
+	 * for claim.
+	 *
+	 * Return:
+	 * - 0 on success
+	 * - LIBUSB_ERROR_NOT_FOUND if no kernel driver was active
+	 * - LIBUSB_ERROR_INVALID_PARAM if the interface does not exist
+	 * - LIBUSB_ERROR_NO_DEVICE if the device has been disconnected since it
+	 *   was opened
+	 * - another LIBUSB_ERROR code on other failure
+	 */
+	int (*detach_kernel_driver)(struct libusb_device_handle *dev_handle,
+		int interface_number);
+
+	/* Attach a kernel driver to an interface. Optional.
+	 *
+	 * Reattach a kernel driver to the device.
+	 *
+	 * Return:
+	 * - 0 on success
+	 * - LIBUSB_ERROR_NOT_FOUND if no kernel driver was active
+	 * - LIBUSB_ERROR_INVALID_PARAM if the interface does not exist
+	 * - LIBUSB_ERROR_NO_DEVICE if the device has been disconnected since it
+	 *   was opened
+	 * - LIBUSB_ERROR_BUSY if a program or driver has claimed the interface,
+	 *   preventing reattachment
+	 * - another LIBUSB_ERROR code on other failure
+	 */
+	int (*attach_kernel_driver)(struct libusb_device_handle *dev_handle,
+		int interface_number);
+
+	/* Destroy a device. Optional.
+	 *
+	 * This function is called when the last reference to a device is
+	 * destroyed. It should free any resources allocated in the get_device_list
+	 * path.
+	 */
+	void (*destroy_device)(struct libusb_device *dev);
+
+	/* Submit a transfer. Your implementation should take the transfer,
+	 * morph it into whatever form your platform requires, and submit it
+	 * asynchronously.
+	 *
+	 * This function must not block.
+	 *
+	 * This function gets called with the flying_transfers_lock locked!
+	 *
+	 * Return:
+	 * - 0 on success
+	 * - LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
+	 * - another LIBUSB_ERROR code on other failure
+	 */
+	int (*submit_transfer)(struct usbi_transfer *itransfer);
+
+	/* Cancel a previously submitted transfer.
+	 *
+	 * This function must not block. The transfer cancellation must complete
+	 * later, resulting in a call to usbi_handle_transfer_cancellation()
+	 * from the context of handle_events.
+	 */
+	int (*cancel_transfer)(struct usbi_transfer *itransfer);
+
+	/* Clear a transfer as if it has completed or cancelled, but do not
+	 * report any completion/cancellation to the library. You should free
+	 * all private data from the transfer as if you were just about to report
+	 * completion or cancellation.
+	 *
+	 * This function might seem a bit out of place. It is used when libusb
+	 * detects a disconnected device - it calls this function for all pending
+	 * transfers before reporting completion (with the disconnect code) to
+	 * the user. Maybe we can improve upon this internal interface in future.
+	 */
+	void (*clear_transfer_priv)(struct usbi_transfer *itransfer);
+
+	/* Handle any pending events on file descriptors. Optional.
+	 *
+	 * Provide this function when file descriptors directly indicate device
+	 * or transfer activity. If your backend does not have such file descriptors,
+	 * implement the handle_transfer_completion function below.
+	 *
+	 * This involves monitoring any active transfers and processing their
+	 * completion or cancellation.
+	 *
+	 * The function is passed an array of pollfd structures (size nfds)
+	 * as a result of the poll() system call. The num_ready parameter
+	 * indicates the number of file descriptors that have reported events
+	 * (i.e. the poll() return value). This should be enough information
+	 * for you to determine which actions need to be taken on the currently
+	 * active transfers.
+	 *
+	 * For any cancelled transfers, call usbi_handle_transfer_cancellation().
+	 * For completed transfers, call usbi_handle_transfer_completion().
+	 * For control/bulk/interrupt transfers, populate the "transferred"
+	 * element of the appropriate usbi_transfer structure before calling the
+	 * above functions. For isochronous transfers, populate the status and
+	 * transferred fields of the iso packet descriptors of the transfer.
+	 *
+	 * This function should also be able to detect disconnection of the
+	 * device, reporting that situation with usbi_handle_disconnect().
+	 *
+	 * When processing an event related to a transfer, you probably want to
+	 * take usbi_transfer.lock to prevent races. See the documentation for
+	 * the usbi_transfer structure.
+	 *
+	 * Return 0 on success, or a LIBUSB_ERROR code on failure.
+	 */
+	int (*handle_events)(struct libusb_context *ctx,
+		struct pollfd *fds, POLL_NFDS_TYPE nfds, int num_ready);
+
+	/* Handle transfer completion. Optional.
+	 *
+	 * Provide this function when there are no file descriptors available
+	 * that directly indicate device or transfer activity. If your backend does
+	 * have such file descriptors, implement the handle_events function above.
+	 *
+	 * Your backend must tell the library when a transfer has completed by
+	 * calling usbi_signal_transfer_completion(). You should store any private
+	 * information about the transfer and its completion status in the transfer's
+	 * private backend data.
+	 *
+	 * During event handling, this function will be called on each transfer for
+	 * which usbi_signal_transfer_completion() was called.
+	 *
+	 * For any cancelled transfers, call usbi_handle_transfer_cancellation().
+	 * For completed transfers, call usbi_handle_transfer_completion().
+	 * For control/bulk/interrupt transfers, populate the "transferred"
+	 * element of the appropriate usbi_transfer structure before calling the
+	 * above functions. For isochronous transfers, populate the status and
+	 * transferred fields of the iso packet descriptors of the transfer.
+	 *
+	 * Return 0 on success, or a LIBUSB_ERROR code on failure.
+	 */
+	int (*handle_transfer_completion)(struct usbi_transfer *itransfer);
+
+	/* Get time from specified clock. At least two clocks must be implemented
+	   by the backend: USBI_CLOCK_REALTIME, and USBI_CLOCK_MONOTONIC.
+
+	   Description of clocks:
+	     USBI_CLOCK_REALTIME : clock returns time since system epoch.
+	     USBI_CLOCK_MONOTONIC: clock returns time since unspecified start
+	                             time (usually boot).
+	 */
+	int (*clock_gettime)(int clkid, struct timespec *tp);
+
+#ifdef USBI_TIMERFD_AVAILABLE
+	/* clock ID of the clock that should be used for timerfd */
+	clockid_t (*get_timerfd_clockid)(void);
+#endif
+
+	/* Number of bytes to reserve for per-device private backend data.
+	 * This private data area is accessible through the "os_priv" field of
+	 * struct libusb_device. */
+	size_t device_priv_size;
+
+	/* Number of bytes to reserve for per-handle private backend data.
+	 * This private data area is accessible through the "os_priv" field of
+	 * struct libusb_device. */
+	size_t device_handle_priv_size;
+
+	/* Number of bytes to reserve for per-transfer private backend data.
+	 * This private data area is accessible by calling
+	 * usbi_transfer_get_os_priv() on the appropriate usbi_transfer instance.
+	 */
+	size_t transfer_priv_size;
+};
+
+extern const struct usbi_os_backend * const usbi_backend;
+
+extern const struct usbi_os_backend linux_usbfs_backend;
+extern const struct usbi_os_backend darwin_backend;
+extern const struct usbi_os_backend openbsd_backend;
+extern const struct usbi_os_backend netbsd_backend;
+extern const struct usbi_os_backend windows_backend;
+extern const struct usbi_os_backend usbdk_backend;
+extern const struct usbi_os_backend wince_backend;
+extern const struct usbi_os_backend haiku_usb_raw_backend;
+extern const struct usbi_os_backend sunos_backend;
+
+extern struct list_head active_contexts_list;
+extern usbi_mutex_static_t active_contexts_lock;
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/darwin_usb.c b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/darwin_usb.c
new file mode 100644
index 000000000..b0219d1b0
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/darwin_usb.c
@@ -0,0 +1,2094 @@
+/* -*- Mode: C; indent-tabs-mode:nil -*- */
+/*
+ * darwin backend for libusb 1.0
+ * Copyright © 2008-2016 Nathan Hjelm <hjelmn@users.sourceforge.net>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "config.h"
+#include <time.h>
+#include <ctype.h>
+#include <errno.h>
+#include <pthread.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/sysctl.h>
+
+#include <mach/clock.h>
+#include <mach/clock_types.h>
+#include <mach/mach_host.h>
+#include <mach/mach_port.h>
+
+#include <AvailabilityMacros.h>
+#if MAC_OS_X_VERSION_MIN_REQUIRED >= 1060 && MAC_OS_X_VERSION_MIN_REQUIRED < 101200
+  #include <objc/objc-auto.h>
+#endif
+
+#if MAC_OS_X_VERSION_MIN_REQUIRED >= 101200
+/* Apple deprecated the darwin atomics in 10.12 in favor of C11 atomics */
+#include <stdatomic.h>
+#define libusb_darwin_atomic_fetch_add(x, y) atomic_fetch_add(x, y)
+
+_Atomic int32_t initCount = ATOMIC_VAR_INIT(0);
+#else
+/* use darwin atomics if the target is older than 10.12 */
+#include <libkern/OSAtomic.h>
+
+/* OSAtomicAdd32Barrier returns the new value */
+#define libusb_darwin_atomic_fetch_add(x, y) (OSAtomicAdd32Barrier(y, x) - y)
+
+static volatile int32_t initCount = 0;
+#endif
+
+#include "darwin_usb.h"
+
+/* async event thread */
+static pthread_mutex_t libusb_darwin_at_mutex = PTHREAD_MUTEX_INITIALIZER;
+static pthread_cond_t  libusb_darwin_at_cond = PTHREAD_COND_INITIALIZER;
+
+static pthread_once_t darwin_init_once = PTHREAD_ONCE_INIT;
+
+static clock_serv_t clock_realtime;
+static clock_serv_t clock_monotonic;
+
+static CFRunLoopRef libusb_darwin_acfl = NULL; /* event cf loop */
+static CFRunLoopSourceRef libusb_darwin_acfls = NULL; /* shutdown signal for event cf loop */
+
+static usbi_mutex_t darwin_cached_devices_lock = PTHREAD_MUTEX_INITIALIZER;
+static struct list_head darwin_cached_devices = {&darwin_cached_devices, &darwin_cached_devices};
+static char *darwin_device_class = kIOUSBDeviceClassName;
+
+#define DARWIN_CACHED_DEVICE(a) ((struct darwin_cached_device *) (((struct darwin_device_priv *)((a)->os_priv))->dev))
+
+/* async event thread */
+static pthread_t libusb_darwin_at;
+
+static int darwin_get_config_descriptor(struct libusb_device *dev, uint8_t config_index, unsigned char *buffer, size_t len, int *host_endian);
+static int darwin_claim_interface(struct libusb_device_handle *dev_handle, int iface);
+static int darwin_release_interface(struct libusb_device_handle *dev_handle, int iface);
+static int darwin_reset_device(struct libusb_device_handle *dev_handle);
+static void darwin_async_io_callback (void *refcon, IOReturn result, void *arg0);
+
+static int darwin_scan_devices(struct libusb_context *ctx);
+static int process_new_device (struct libusb_context *ctx, io_service_t service);
+
+#if defined(ENABLE_LOGGING)
+static const char *darwin_error_str (int result) {
+  static char string_buffer[50];
+  switch (result) {
+  case kIOReturnSuccess:
+    return "no error";
+  case kIOReturnNotOpen:
+    return "device not opened for exclusive access";
+  case kIOReturnNoDevice:
+    return "no connection to an IOService";
+  case kIOUSBNoAsyncPortErr:
+    return "no async port has been opened for interface";
+  case kIOReturnExclusiveAccess:
+    return "another process has device opened for exclusive access";
+  case kIOUSBPipeStalled:
+    return "pipe is stalled";
+  case kIOReturnError:
+    return "could not establish a connection to the Darwin kernel";
+  case kIOUSBTransactionTimeout:
+    return "transaction timed out";
+  case kIOReturnBadArgument:
+    return "invalid argument";
+  case kIOReturnAborted:
+    return "transaction aborted";
+  case kIOReturnNotResponding:
+    return "device not responding";
+  case kIOReturnOverrun:
+    return "data overrun";
+  case kIOReturnCannotWire:
+    return "physical memory can not be wired down";
+  case kIOReturnNoResources:
+    return "out of resources";
+  case kIOUSBHighSpeedSplitError:
+    return "high speed split error";
+  default:
+    snprintf(string_buffer, sizeof(string_buffer), "unknown error (0x%x)", result);
+    return string_buffer;
+  }
+}
+#endif
+
+static int darwin_to_libusb (int result) {
+  switch (result) {
+  case kIOReturnUnderrun:
+  case kIOReturnSuccess:
+    return LIBUSB_SUCCESS;
+  case kIOReturnNotOpen:
+  case kIOReturnNoDevice:
+    return LIBUSB_ERROR_NO_DEVICE;
+  case kIOReturnExclusiveAccess:
+    return LIBUSB_ERROR_ACCESS;
+  case kIOUSBPipeStalled:
+    return LIBUSB_ERROR_PIPE;
+  case kIOReturnBadArgument:
+    return LIBUSB_ERROR_INVALID_PARAM;
+  case kIOUSBTransactionTimeout:
+    return LIBUSB_ERROR_TIMEOUT;
+  case kIOReturnNotResponding:
+  case kIOReturnAborted:
+  case kIOReturnError:
+  case kIOUSBNoAsyncPortErr:
+  default:
+    return LIBUSB_ERROR_OTHER;
+  }
+}
+
+/* this function must be called with the darwin_cached_devices_lock held */
+static void darwin_deref_cached_device(struct darwin_cached_device *cached_dev) {
+  cached_dev->refcount--;
+  /* free the device and remove it from the cache */
+  if (0 == cached_dev->refcount) {
+    list_del(&cached_dev->list);
+
+    (*(cached_dev->device))->Release(cached_dev->device);
+    free (cached_dev);
+  }
+}
+
+static void darwin_ref_cached_device(struct darwin_cached_device *cached_dev) {
+  cached_dev->refcount++;
+}
+
+static int ep_to_pipeRef(struct libusb_device_handle *dev_handle, uint8_t ep, uint8_t *pipep, uint8_t *ifcp, struct darwin_interface **interface_out) {
+  struct darwin_device_handle_priv *priv = (struct darwin_device_handle_priv *)dev_handle->os_priv;
+
+  /* current interface */
+  struct darwin_interface *cInterface;
+
+  int8_t i, iface;
+
+  usbi_dbg ("converting ep address 0x%02x to pipeRef and interface", ep);
+
+  for (iface = 0 ; iface < USB_MAXINTERFACES ; iface++) {
+    cInterface = &priv->interfaces[iface];
+
+    if (dev_handle->claimed_interfaces & (1 << iface)) {
+      for (i = 0 ; i < cInterface->num_endpoints ; i++) {
+        if (cInterface->endpoint_addrs[i] == ep) {
+          *pipep = i + 1;
+
+          if (ifcp)
+            *ifcp = iface;
+
+          if (interface_out)
+            *interface_out = cInterface;
+
+          usbi_dbg ("pipe %d on interface %d matches", *pipep, iface);
+          return 0;
+        }
+      }
+    }
+  }
+
+  /* No pipe found with the correct endpoint address */
+  usbi_warn (HANDLE_CTX(dev_handle), "no pipeRef found with endpoint address 0x%02x.", ep);
+
+  return LIBUSB_ERROR_NOT_FOUND;
+}
+
+static int usb_setup_device_iterator (io_iterator_t *deviceIterator, UInt32 location) {
+  CFMutableDictionaryRef matchingDict = IOServiceMatching(darwin_device_class);
+
+  if (!matchingDict)
+    return kIOReturnError;
+
+  if (location) {
+    CFMutableDictionaryRef propertyMatchDict = CFDictionaryCreateMutable(kCFAllocatorDefault, 0,
+                                                                         &kCFTypeDictionaryKeyCallBacks,
+                                                                         &kCFTypeDictionaryValueCallBacks);
+
+    if (propertyMatchDict) {
+      /* there are no unsigned CFNumber types so treat the value as signed. the os seems to do this
+         internally (CFNumberType of locationID is 3) */
+      CFTypeRef locationCF = CFNumberCreate (NULL, kCFNumberSInt32Type, &location);
+
+      CFDictionarySetValue (propertyMatchDict, CFSTR(kUSBDevicePropertyLocationID), locationCF);
+      /* release our reference to the CFNumber (CFDictionarySetValue retains it) */
+      CFRelease (locationCF);
+
+      CFDictionarySetValue (matchingDict, CFSTR(kIOPropertyMatchKey), propertyMatchDict);
+      /* release out reference to the CFMutableDictionaryRef (CFDictionarySetValue retains it) */
+      CFRelease (propertyMatchDict);
+    }
+    /* else we can still proceed as long as the caller accounts for the possibility of other devices in the iterator */
+  }
+
+  return IOServiceGetMatchingServices(kIOMasterPortDefault, matchingDict, deviceIterator);
+}
+
+/* Returns 1 on success, 0 on failure. */
+static int get_ioregistry_value_number (io_service_t service, CFStringRef property, CFNumberType type, void *p) {
+  CFTypeRef cfNumber = IORegistryEntryCreateCFProperty (service, property, kCFAllocatorDefault, 0);
+  int ret = 0;
+
+  if (cfNumber) {
+    if (CFGetTypeID(cfNumber) == CFNumberGetTypeID()) {
+      ret = CFNumberGetValue(cfNumber, type, p);
+    }
+
+    CFRelease (cfNumber);
+  }
+
+  return ret;
+}
+
+static int get_ioregistry_value_data (io_service_t service, CFStringRef property, ssize_t size, void *p) {
+  CFTypeRef cfData = IORegistryEntryCreateCFProperty (service, property, kCFAllocatorDefault, 0);
+  int ret = 0;
+
+  if (cfData) {
+    if (CFGetTypeID (cfData) == CFDataGetTypeID ()) {
+      CFIndex length = CFDataGetLength (cfData);
+      if (length < size) {
+        size = length;
+      }
+
+      CFDataGetBytes (cfData, CFRangeMake(0, size), p);
+      ret = 1;
+    }
+
+    CFRelease (cfData);
+  }
+
+  return ret;
+}
+
+static usb_device_t **darwin_device_from_service (io_service_t service)
+{
+  io_cf_plugin_ref_t *plugInInterface = NULL;
+  usb_device_t **device;
+  kern_return_t result;
+  SInt32 score;
+
+  result = IOCreatePlugInInterfaceForService(service, kIOUSBDeviceUserClientTypeID,
+                                             kIOCFPlugInInterfaceID, &plugInInterface,
+                                             &score);
+
+  if (kIOReturnSuccess != result || !plugInInterface) {
+    usbi_dbg ("could not set up plugin for service: %s", darwin_error_str (result));
+    return NULL;
+  }
+
+  (void)(*plugInInterface)->QueryInterface(plugInInterface, CFUUIDGetUUIDBytes(DeviceInterfaceID),
+                                           (LPVOID)&device);
+  /* Use release instead of IODestroyPlugInInterface to avoid stopping IOServices associated with this device */
+  (*plugInInterface)->Release (plugInInterface);
+
+  return device;
+}
+
+static void darwin_devices_attached (void *ptr, io_iterator_t add_devices) {
+  struct libusb_context *ctx;
+  io_service_t service;
+
+  usbi_mutex_lock(&active_contexts_lock);
+
+  while ((service = IOIteratorNext(add_devices))) {
+    /* add this device to each active context's device list */
+    list_for_each_entry(ctx, &active_contexts_list, list, struct libusb_context) {
+      process_new_device (ctx, service);;
+    }
+
+    IOObjectRelease(service);
+  }
+
+  usbi_mutex_unlock(&active_contexts_lock);
+}
+
+static void darwin_devices_detached (void *ptr, io_iterator_t rem_devices) {
+  struct libusb_device *dev = NULL;
+  struct libusb_context *ctx;
+  struct darwin_cached_device *old_device;
+
+  io_service_t device;
+  UInt64 session;
+  int ret;
+
+  usbi_mutex_lock(&active_contexts_lock);
+
+  while ((device = IOIteratorNext (rem_devices)) != 0) {
+    /* get the location from the i/o registry */
+    ret = get_ioregistry_value_number (device, CFSTR("sessionID"), kCFNumberSInt64Type, &session);
+    IOObjectRelease (device);
+    if (!ret)
+      continue;
+
+    /* we need to match darwin_ref_cached_device call made in darwin_get_cached_device function
+       otherwise no cached device will ever get freed */
+    usbi_mutex_lock(&darwin_cached_devices_lock);
+    list_for_each_entry(old_device, &darwin_cached_devices, list, struct darwin_cached_device) {
+      if (old_device->session == session) {
+        darwin_deref_cached_device (old_device);
+        break;
+      }
+    }
+    usbi_mutex_unlock(&darwin_cached_devices_lock);
+
+    list_for_each_entry(ctx, &active_contexts_list, list, struct libusb_context) {
+      usbi_dbg ("notifying context %p of device disconnect", ctx);
+
+      dev = usbi_get_device_by_session_id(ctx, (unsigned long) session);
+      if (dev) {
+        /* signal the core that this device has been disconnected. the core will tear down this device
+           when the reference count reaches 0 */
+        usbi_disconnect_device(dev);
+        libusb_unref_device(dev);
+      }
+    }
+  }
+
+  usbi_mutex_unlock(&active_contexts_lock);
+}
+
+static void darwin_hotplug_poll (void)
+{
+  /* not sure if 5 seconds will be too long/short but it should work ok */
+  mach_timespec_t timeout = {.tv_sec = 5, .tv_nsec = 0};
+
+  /* since a kernel thread may nodify the IOInterators used for
+   * hotplug notidication we can't just clear the iterators.
+   * instead just wait until all IOService providers are quiet */
+  (void) IOKitWaitQuiet (kIOMasterPortDefault, &timeout);
+}
+
+static void darwin_clear_iterator (io_iterator_t iter) {
+  io_service_t device;
+
+  while ((device = IOIteratorNext (iter)) != 0)
+    IOObjectRelease (device);
+}
+
+static void *darwin_event_thread_main (void *arg0) {
+  IOReturn kresult;
+  struct libusb_context *ctx = (struct libusb_context *)arg0;
+  CFRunLoopRef runloop;
+
+#if MAC_OS_X_VERSION_MIN_REQUIRED >= 1060
+  /* Set this thread's name, so it can be seen in the debugger
+     and crash reports. */
+  pthread_setname_np ("org.libusb.device-hotplug");
+#endif
+
+#if MAC_OS_X_VERSION_MIN_REQUIRED >= 1060 && MAC_OS_X_VERSION_MIN_REQUIRED < 101200
+  /* Tell the Objective-C garbage collector about this thread.
+     This is required because, unlike NSThreads, pthreads are
+     not automatically registered. Although we don't use
+     Objective-C, we use CoreFoundation, which does.
+     Garbage collection support was entirely removed in 10.12,
+     so don't bother there. */
+  objc_registerThreadWithCollector();
+#endif
+
+  /* hotplug (device arrival/removal) sources */
+  CFRunLoopSourceContext libusb_shutdown_cfsourcectx;
+  CFRunLoopSourceRef     libusb_notification_cfsource;
+  io_notification_port_t libusb_notification_port;
+  io_iterator_t          libusb_rem_device_iterator;
+  io_iterator_t          libusb_add_device_iterator;
+
+  usbi_dbg ("creating hotplug event source");
+
+  runloop = CFRunLoopGetCurrent ();
+  CFRetain (runloop);
+
+  /* add the shutdown cfsource to the run loop */
+  memset(&libusb_shutdown_cfsourcectx, 0, sizeof(libusb_shutdown_cfsourcectx));
+  libusb_shutdown_cfsourcectx.info = runloop;
+  libusb_shutdown_cfsourcectx.perform = (void (*)(void *))CFRunLoopStop;
+  libusb_darwin_acfls = CFRunLoopSourceCreate(NULL, 0, &libusb_shutdown_cfsourcectx);
+  CFRunLoopAddSource(runloop, libusb_darwin_acfls, kCFRunLoopDefaultMode);
+
+  /* add the notification port to the run loop */
+  libusb_notification_port     = IONotificationPortCreate (kIOMasterPortDefault);
+  libusb_notification_cfsource = IONotificationPortGetRunLoopSource (libusb_notification_port);
+  CFRunLoopAddSource(runloop, libusb_notification_cfsource, kCFRunLoopDefaultMode);
+
+  /* create notifications for removed devices */
+  kresult = IOServiceAddMatchingNotification (libusb_notification_port, kIOTerminatedNotification,
+                                              IOServiceMatching(darwin_device_class),
+                                              darwin_devices_detached,
+                                              ctx, &libusb_rem_device_iterator);
+
+  if (kresult != kIOReturnSuccess) {
+    usbi_err (ctx, "could not add hotplug event source: %s", darwin_error_str (kresult));
+
+    pthread_exit (NULL);
+  }
+
+  /* create notifications for attached devices */
+  kresult = IOServiceAddMatchingNotification(libusb_notification_port, kIOFirstMatchNotification,
+                                              IOServiceMatching(darwin_device_class),
+                                              darwin_devices_attached,
+                                              ctx, &libusb_add_device_iterator);
+
+  if (kresult != kIOReturnSuccess) {
+    usbi_err (ctx, "could not add hotplug event source: %s", darwin_error_str (kresult));
+
+    pthread_exit (NULL);
+  }
+
+  /* arm notifiers */
+  darwin_clear_iterator (libusb_rem_device_iterator);
+  darwin_clear_iterator (libusb_add_device_iterator);
+
+  usbi_dbg ("darwin event thread ready to receive events");
+
+  /* signal the main thread that the hotplug runloop has been created. */
+  pthread_mutex_lock (&libusb_darwin_at_mutex);
+  libusb_darwin_acfl = runloop;
+  pthread_cond_signal (&libusb_darwin_at_cond);
+  pthread_mutex_unlock (&libusb_darwin_at_mutex);
+
+  /* run the runloop */
+  CFRunLoopRun();
+
+  usbi_dbg ("darwin event thread exiting");
+
+  /* remove the notification cfsource */
+  CFRunLoopRemoveSource(runloop, libusb_notification_cfsource, kCFRunLoopDefaultMode);
+
+  /* remove the shutdown cfsource */
+  CFRunLoopRemoveSource(runloop, libusb_darwin_acfls, kCFRunLoopDefaultMode);
+
+  /* delete notification port */
+  IONotificationPortDestroy (libusb_notification_port);
+
+  /* delete iterators */
+  IOObjectRelease (libusb_rem_device_iterator);
+  IOObjectRelease (libusb_add_device_iterator);
+
+  CFRelease (libusb_darwin_acfls);
+  CFRelease (runloop);
+
+  libusb_darwin_acfls = NULL;
+  libusb_darwin_acfl = NULL;
+
+  pthread_exit (NULL);
+}
+
+/* cleanup function to destroy cached devices */
+static void __attribute__((destructor)) _darwin_finalize(void) {
+  struct darwin_cached_device *dev, *next;
+
+  usbi_mutex_lock(&darwin_cached_devices_lock);
+  list_for_each_entry_safe(dev, next, &darwin_cached_devices, list, struct darwin_cached_device) {
+    darwin_deref_cached_device(dev);
+  }
+  usbi_mutex_unlock(&darwin_cached_devices_lock);
+}
+
+static void darwin_check_version (void) {
+  /* adjust for changes in the USB stack in xnu 15 */
+  int sysctl_args[] = {CTL_KERN, KERN_OSRELEASE};
+  long version;
+  char version_string[256] = {'\0',};
+  size_t length = 256;
+
+  sysctl(sysctl_args, 2, version_string, &length, NULL, 0);
+
+  errno = 0;
+  version = strtol (version_string, NULL, 10);
+  if (0 == errno && version >= 15) {
+    darwin_device_class = "IOUSBHostDevice";
+  }
+}
+
+static int darwin_init(struct libusb_context *ctx) {
+  host_name_port_t host_self;
+  int rc;
+
+  rc = pthread_once (&darwin_init_once, darwin_check_version);
+  if (rc) {
+    return LIBUSB_ERROR_OTHER;
+  }
+
+  rc = darwin_scan_devices (ctx);
+  if (LIBUSB_SUCCESS != rc) {
+    return rc;
+  }
+
+  if (libusb_darwin_atomic_fetch_add (&initCount, 1) == 0) {
+    /* create the clocks that will be used */
+
+    host_self = mach_host_self();
+    host_get_clock_service(host_self, CALENDAR_CLOCK, &clock_realtime);
+    host_get_clock_service(host_self, SYSTEM_CLOCK, &clock_monotonic);
+    mach_port_deallocate(mach_task_self(), host_self);
+
+    pthread_create (&libusb_darwin_at, NULL, darwin_event_thread_main, ctx);
+
+    pthread_mutex_lock (&libusb_darwin_at_mutex);
+    while (!libusb_darwin_acfl)
+      pthread_cond_wait (&libusb_darwin_at_cond, &libusb_darwin_at_mutex);
+    pthread_mutex_unlock (&libusb_darwin_at_mutex);
+  }
+
+  return rc;
+}
+
+static void darwin_exit (void) {
+  if (libusb_darwin_atomic_fetch_add (&initCount, -1) == 1) {
+    mach_port_deallocate(mach_task_self(), clock_realtime);
+    mach_port_deallocate(mach_task_self(), clock_monotonic);
+
+    /* stop the event runloop and wait for the thread to terminate. */
+    CFRunLoopSourceSignal(libusb_darwin_acfls);
+    CFRunLoopWakeUp (libusb_darwin_acfl);
+    pthread_join (libusb_darwin_at, NULL);
+  }
+}
+
+static int darwin_get_device_descriptor(struct libusb_device *dev, unsigned char *buffer, int *host_endian) {
+  struct darwin_cached_device *priv = DARWIN_CACHED_DEVICE(dev);
+
+  /* return cached copy */
+  memmove (buffer, &(priv->dev_descriptor), DEVICE_DESC_LENGTH);
+
+  *host_endian = 0;
+
+  return 0;
+}
+
+static int get_configuration_index (struct libusb_device *dev, int config_value) {
+  struct darwin_cached_device *priv = DARWIN_CACHED_DEVICE(dev);
+  UInt8 i, numConfig;
+  IOUSBConfigurationDescriptorPtr desc;
+  IOReturn kresult;
+
+  /* is there a simpler way to determine the index? */
+  kresult = (*(priv->device))->GetNumberOfConfigurations (priv->device, &numConfig);
+  if (kresult != kIOReturnSuccess)
+    return darwin_to_libusb (kresult);
+
+  for (i = 0 ; i < numConfig ; i++) {
+    (*(priv->device))->GetConfigurationDescriptorPtr (priv->device, i, &desc);
+
+    if (desc->bConfigurationValue == config_value)
+      return i;
+  }
+
+  /* configuration not found */
+  return LIBUSB_ERROR_NOT_FOUND;
+}
+
+static int darwin_get_active_config_descriptor(struct libusb_device *dev, unsigned char *buffer, size_t len, int *host_endian) {
+  struct darwin_cached_device *priv = DARWIN_CACHED_DEVICE(dev);
+  int config_index;
+
+  if (0 == priv->active_config)
+    return LIBUSB_ERROR_NOT_FOUND;
+
+  config_index = get_configuration_index (dev, priv->active_config);
+  if (config_index < 0)
+    return config_index;
+
+  return darwin_get_config_descriptor (dev, config_index, buffer, len, host_endian);
+}
+
+static int darwin_get_config_descriptor(struct libusb_device *dev, uint8_t config_index, unsigned char *buffer, size_t len, int *host_endian) {
+  struct darwin_cached_device *priv = DARWIN_CACHED_DEVICE(dev);
+  IOUSBConfigurationDescriptorPtr desc;
+  IOReturn kresult;
+  int ret;
+
+  if (!priv || !priv->device)
+    return LIBUSB_ERROR_OTHER;
+
+  kresult = (*priv->device)->GetConfigurationDescriptorPtr (priv->device, config_index, &desc);
+  if (kresult == kIOReturnSuccess) {
+    /* copy descriptor */
+    if (libusb_le16_to_cpu(desc->wTotalLength) < len)
+      len = libusb_le16_to_cpu(desc->wTotalLength);
+
+    memmove (buffer, desc, len);
+
+    /* GetConfigurationDescriptorPtr returns the descriptor in USB bus order */
+    *host_endian = 0;
+  }
+
+  ret = darwin_to_libusb (kresult);
+  if (ret != LIBUSB_SUCCESS)
+    return ret;
+
+  return (int) len;
+}
+
+/* check whether the os has configured the device */
+static int darwin_check_configuration (struct libusb_context *ctx, struct darwin_cached_device *dev) {
+  usb_device_t **darwin_device = dev->device;
+
+  IOUSBConfigurationDescriptorPtr configDesc;
+  IOUSBFindInterfaceRequest request;
+  kern_return_t             kresult;
+  io_iterator_t             interface_iterator;
+  io_service_t              firstInterface;
+
+  if (dev->dev_descriptor.bNumConfigurations < 1) {
+    usbi_err (ctx, "device has no configurations");
+    return LIBUSB_ERROR_OTHER; /* no configurations at this speed so we can't use it */
+  }
+
+  /* checking the configuration of a root hub simulation takes ~1 s in 10.11. the device is
+     not usable anyway */
+  if (0x05ac == dev->dev_descriptor.idVendor && 0x8005 == dev->dev_descriptor.idProduct) {
+    usbi_dbg ("ignoring configuration on root hub simulation");
+    dev->active_config = 0;
+    return 0;
+  }
+
+  /* find the first configuration */
+  kresult = (*darwin_device)->GetConfigurationDescriptorPtr (darwin_device, 0, &configDesc);
+  dev->first_config = (kIOReturnSuccess == kresult) ? configDesc->bConfigurationValue : 1;
+
+  /* check if the device is already configured. there is probably a better way than iterating over the
+     to accomplish this (the trick is we need to avoid a call to GetConfigurations since buggy devices
+     might lock up on the device request) */
+
+  /* Setup the Interface Request */
+  request.bInterfaceClass    = kIOUSBFindInterfaceDontCare;
+  request.bInterfaceSubClass = kIOUSBFindInterfaceDontCare;
+  request.bInterfaceProtocol = kIOUSBFindInterfaceDontCare;
+  request.bAlternateSetting  = kIOUSBFindInterfaceDontCare;
+
+  kresult = (*(darwin_device))->CreateInterfaceIterator(darwin_device, &request, &interface_iterator);
+  if (kresult)
+    return darwin_to_libusb (kresult);
+
+  /* iterate once */
+  firstInterface = IOIteratorNext(interface_iterator);
+
+  /* done with the interface iterator */
+  IOObjectRelease(interface_iterator);
+
+  if (firstInterface) {
+    IOObjectRelease (firstInterface);
+
+    /* device is configured */
+    if (dev->dev_descriptor.bNumConfigurations == 1)
+      /* to avoid problems with some devices get the configurations value from the configuration descriptor */
+      dev->active_config = dev->first_config;
+    else
+      /* devices with more than one configuration should work with GetConfiguration */
+      (*darwin_device)->GetConfiguration (darwin_device, &dev->active_config);
+  } else
+    /* not configured */
+    dev->active_config = 0;
+  
+  usbi_dbg ("active config: %u, first config: %u", dev->active_config, dev->first_config);
+
+  return 0;
+}
+
+static int darwin_request_descriptor (usb_device_t **device, UInt8 desc, UInt8 desc_index, void *buffer, size_t buffer_size) {
+  IOUSBDevRequestTO req;
+
+  memset (buffer, 0, buffer_size);
+
+  /* Set up request for descriptor/ */
+  req.bmRequestType = USBmakebmRequestType(kUSBIn, kUSBStandard, kUSBDevice);
+  req.bRequest      = kUSBRqGetDescriptor;
+  req.wValue        = desc << 8;
+  req.wIndex        = desc_index;
+  req.wLength       = buffer_size;
+  req.pData         = buffer;
+  req.noDataTimeout = 20;
+  req.completionTimeout = 100;
+
+  return (*device)->DeviceRequestTO (device, &req);
+}
+
+static int darwin_cache_device_descriptor (struct libusb_context *ctx, struct darwin_cached_device *dev) {
+  usb_device_t **device = dev->device;
+  int retries = 1, delay = 30000;
+  int unsuspended = 0, try_unsuspend = 1, try_reconfigure = 1;
+  int is_open = 0;
+  int ret = 0, ret2;
+  UInt8 bDeviceClass;
+  UInt16 idProduct, idVendor;
+
+  dev->can_enumerate = 0;
+
+  (*device)->GetDeviceClass (device, &bDeviceClass);
+  (*device)->GetDeviceProduct (device, &idProduct);
+  (*device)->GetDeviceVendor (device, &idVendor);
+
+  /* According to Apple's documentation the device must be open for DeviceRequest but we may not be able to open some
+   * devices and Apple's USB Prober doesn't bother to open the device before issuing a descriptor request.  Still,
+   * to follow the spec as closely as possible, try opening the device */
+  is_open = ((*device)->USBDeviceOpenSeize(device) == kIOReturnSuccess);
+
+  do {
+    /**** retrieve device descriptor ****/
+    ret = darwin_request_descriptor (device, kUSBDeviceDesc, 0, &dev->dev_descriptor, sizeof(dev->dev_descriptor));
+
+    if (kIOReturnOverrun == ret && kUSBDeviceDesc == dev->dev_descriptor.bDescriptorType)
+      /* received an overrun error but we still received a device descriptor */
+      ret = kIOReturnSuccess;
+
+    if (kIOUSBVendorIDAppleComputer == idVendor) {
+      /* NTH: don't bother retrying or unsuspending Apple devices */
+      break;
+    }
+
+    if (kIOReturnSuccess == ret && (0 == dev->dev_descriptor.bNumConfigurations ||
+                                    0 == dev->dev_descriptor.bcdUSB)) {
+      /* work around for incorrectly configured devices */
+      if (try_reconfigure && is_open) {
+        usbi_dbg("descriptor appears to be invalid. resetting configuration before trying again...");
+
+        /* set the first configuration */
+        (*device)->SetConfiguration(device, 1);
+
+        /* don't try to reconfigure again */
+        try_reconfigure = 0;
+      }
+
+      ret = kIOUSBPipeStalled;
+    }
+
+    if (kIOReturnSuccess != ret && is_open && try_unsuspend) {
+      /* device may be suspended. unsuspend it and try again */
+#if DeviceVersion >= 320
+      UInt32 info = 0;
+
+      /* IOUSBFamily 320+ provides a way to detect device suspension but earlier versions do not */
+      (void)(*device)->GetUSBDeviceInformation (device, &info);
+
+      /* note that the device was suspended */
+      if (info & (1 << kUSBInformationDeviceIsSuspendedBit) || 0 == info)
+        try_unsuspend = 1;
+#endif
+
+      if (try_unsuspend) {
+        /* try to unsuspend the device */
+        ret2 = (*device)->USBDeviceSuspend (device, 0);
+        if (kIOReturnSuccess != ret2) {
+          /* prevent log spew from poorly behaving devices.  this indicates the
+             os actually had trouble communicating with the device */
+          usbi_dbg("could not retrieve device descriptor. failed to unsuspend: %s",darwin_error_str(ret2));
+        } else
+          unsuspended = 1;
+
+        try_unsuspend = 0;
+      }
+    }
+
+    if (kIOReturnSuccess != ret) {
+      usbi_dbg("kernel responded with code: 0x%08x. sleeping for %d ms before trying again", ret, delay/1000);
+      /* sleep for a little while before trying again */
+      nanosleep(&(struct timespec){delay / 1000000, (delay * 1000) % 1000000000UL}, NULL);
+    }
+  } while (kIOReturnSuccess != ret && retries--);
+
+  if (unsuspended)
+    /* resuspend the device */
+    (void)(*device)->USBDeviceSuspend (device, 1);
+
+  if (is_open)
+    (void) (*device)->USBDeviceClose (device);
+
+  if (ret != kIOReturnSuccess) {
+    /* a debug message was already printed out for this error */
+    if (LIBUSB_CLASS_HUB == bDeviceClass)
+      usbi_dbg ("could not retrieve device descriptor %.4x:%.4x: %s (%x). skipping device",
+                idVendor, idProduct, darwin_error_str (ret), ret);
+    else
+      usbi_warn (ctx, "could not retrieve device descriptor %.4x:%.4x: %s (%x). skipping device",
+                 idVendor, idProduct, darwin_error_str (ret), ret);
+    return darwin_to_libusb (ret);
+  }
+
+  /* catch buggy hubs (which appear to be virtual). Apple's own USB prober has problems with these devices. */
+  if (libusb_le16_to_cpu (dev->dev_descriptor.idProduct) != idProduct) {
+    /* not a valid device */
+    usbi_warn (ctx, "idProduct from iokit (%04x) does not match idProduct in descriptor (%04x). skipping device",
+               idProduct, libusb_le16_to_cpu (dev->dev_descriptor.idProduct));
+    return LIBUSB_ERROR_NO_DEVICE;
+  }
+
+  usbi_dbg ("cached device descriptor:");
+  usbi_dbg ("  bDescriptorType:    0x%02x", dev->dev_descriptor.bDescriptorType);
+  usbi_dbg ("  bcdUSB:             0x%04x", dev->dev_descriptor.bcdUSB);
+  usbi_dbg ("  bDeviceClass:       0x%02x", dev->dev_descriptor.bDeviceClass);
+  usbi_dbg ("  bDeviceSubClass:    0x%02x", dev->dev_descriptor.bDeviceSubClass);
+  usbi_dbg ("  bDeviceProtocol:    0x%02x", dev->dev_descriptor.bDeviceProtocol);
+  usbi_dbg ("  bMaxPacketSize0:    0x%02x", dev->dev_descriptor.bMaxPacketSize0);
+  usbi_dbg ("  idVendor:           0x%04x", dev->dev_descriptor.idVendor);
+  usbi_dbg ("  idProduct:          0x%04x", dev->dev_descriptor.idProduct);
+  usbi_dbg ("  bcdDevice:          0x%04x", dev->dev_descriptor.bcdDevice);
+  usbi_dbg ("  iManufacturer:      0x%02x", dev->dev_descriptor.iManufacturer);
+  usbi_dbg ("  iProduct:           0x%02x", dev->dev_descriptor.iProduct);
+  usbi_dbg ("  iSerialNumber:      0x%02x", dev->dev_descriptor.iSerialNumber);
+  usbi_dbg ("  bNumConfigurations: 0x%02x", dev->dev_descriptor.bNumConfigurations);
+
+  dev->can_enumerate = 1;
+
+  return LIBUSB_SUCCESS;
+}
+
+static int get_device_port (io_service_t service, UInt8 *port) {
+  kern_return_t result;
+  io_service_t parent;
+  int ret = 0;
+
+  if (get_ioregistry_value_number (service, CFSTR("PortNum"), kCFNumberSInt8Type, port)) {
+    return 1;
+  }
+
+  result = IORegistryEntryGetParentEntry (service, kIOServicePlane, &parent);
+  if (kIOReturnSuccess == result) {
+    ret = get_ioregistry_value_data (parent, CFSTR("port"), 1, port);
+    IOObjectRelease (parent);
+  }
+
+  return ret;
+}
+
+static int darwin_get_cached_device(struct libusb_context *ctx, io_service_t service,
+                                    struct darwin_cached_device **cached_out) {
+  struct darwin_cached_device *new_device;
+  UInt64 sessionID = 0, parent_sessionID = 0;
+  int ret = LIBUSB_SUCCESS;
+  usb_device_t **device;
+  io_service_t parent;
+  kern_return_t result;
+  UInt8 port = 0;
+
+  /* get some info from the io registry */
+  (void) get_ioregistry_value_number (service, CFSTR("sessionID"), kCFNumberSInt64Type, &sessionID);
+  if (!get_device_port (service, &port)) {
+    usbi_dbg("could not get connected port number");
+  }
+
+  usbi_dbg("finding cached device for sessionID 0x%" PRIx64, sessionID);
+
+  result = IORegistryEntryGetParentEntry (service, kIOUSBPlane, &parent);
+
+  if (kIOReturnSuccess == result) {
+    (void) get_ioregistry_value_number (parent, CFSTR("sessionID"), kCFNumberSInt64Type, &parent_sessionID);
+    IOObjectRelease(parent);
+  }
+
+  usbi_mutex_lock(&darwin_cached_devices_lock);
+  do {
+    *cached_out = NULL;
+
+    list_for_each_entry(new_device, &darwin_cached_devices, list, struct darwin_cached_device) {
+      usbi_dbg("matching sessionID 0x%" PRIx64 " against cached device with sessionID 0x%" PRIx64, sessionID, new_device->session);
+      if (new_device->session == sessionID) {
+        usbi_dbg("using cached device for device");
+        *cached_out = new_device;
+        break;
+      }
+    }
+
+    if (*cached_out)
+      break;
+
+    usbi_dbg("caching new device with sessionID 0x%" PRIx64, sessionID);
+
+    device = darwin_device_from_service (service);
+    if (!device) {
+      ret = LIBUSB_ERROR_NO_DEVICE;
+      break;
+    }
+
+    new_device = calloc (1, sizeof (*new_device));
+    if (!new_device) {
+      ret = LIBUSB_ERROR_NO_MEM;
+      break;
+    }
+
+    /* add this device to the cached device list */
+    list_add(&new_device->list, &darwin_cached_devices);
+
+    (*device)->GetDeviceAddress (device, (USBDeviceAddress *)&new_device->address);
+
+    /* keep a reference to this device */
+    darwin_ref_cached_device(new_device);
+
+    new_device->device = device;
+    new_device->session = sessionID;
+    (*device)->GetLocationID (device, &new_device->location);
+    new_device->port = port;
+    new_device->parent_session = parent_sessionID;
+
+    /* cache the device descriptor */
+    ret = darwin_cache_device_descriptor(ctx, new_device);
+    if (ret)
+      break;
+
+    if (new_device->can_enumerate) {
+      snprintf(new_device->sys_path, 20, "%03i-%04x-%04x-%02x-%02x", new_device->address,
+               new_device->dev_descriptor.idVendor, new_device->dev_descriptor.idProduct,
+               new_device->dev_descriptor.bDeviceClass, new_device->dev_descriptor.bDeviceSubClass);
+    }
+  } while (0);
+
+  usbi_mutex_unlock(&darwin_cached_devices_lock);
+
+  /* keep track of devices regardless of if we successfully enumerate them to
+     prevent them from being enumerated multiple times */
+
+  *cached_out = new_device;
+
+  return ret;
+}
+
+static int process_new_device (struct libusb_context *ctx, io_service_t service) {
+  struct darwin_device_priv *priv;
+  struct libusb_device *dev = NULL;
+  struct darwin_cached_device *cached_device;
+  UInt8 devSpeed;
+  int ret = 0;
+
+  do {
+    ret = darwin_get_cached_device (ctx, service, &cached_device);
+
+    if (ret < 0 || !cached_device->can_enumerate) {
+      return ret;
+    }
+
+    /* check current active configuration (and cache the first configuration value--
+       which may be used by claim_interface) */
+    ret = darwin_check_configuration (ctx, cached_device);
+    if (ret)
+      break;
+
+    usbi_dbg ("allocating new device in context %p for with session 0x%" PRIx64,
+              ctx, cached_device->session);
+
+    dev = usbi_alloc_device(ctx, (unsigned long) cached_device->session);
+    if (!dev) {
+      return LIBUSB_ERROR_NO_MEM;
+    }
+
+    priv = (struct darwin_device_priv *)dev->os_priv;
+
+    priv->dev = cached_device;
+    darwin_ref_cached_device (priv->dev);
+
+    if (cached_device->parent_session > 0) {
+      dev->parent_dev = usbi_get_device_by_session_id (ctx, (unsigned long) cached_device->parent_session);
+    } else {
+      dev->parent_dev = NULL;
+    }
+    dev->port_number    = cached_device->port;
+    dev->bus_number     = cached_device->location >> 24;
+    dev->device_address = cached_device->address;
+
+    (*(priv->dev->device))->GetDeviceSpeed (priv->dev->device, &devSpeed);
+
+    switch (devSpeed) {
+    case kUSBDeviceSpeedLow: dev->speed = LIBUSB_SPEED_LOW; break;
+    case kUSBDeviceSpeedFull: dev->speed = LIBUSB_SPEED_FULL; break;
+    case kUSBDeviceSpeedHigh: dev->speed = LIBUSB_SPEED_HIGH; break;
+#if DeviceVersion >= 500
+    case kUSBDeviceSpeedSuper: dev->speed = LIBUSB_SPEED_SUPER; break;
+#endif
+    default:
+      usbi_warn (ctx, "Got unknown device speed %d", devSpeed);
+    }
+
+    ret = usbi_sanitize_device (dev);
+    if (ret < 0)
+      break;
+
+    usbi_dbg ("found device with address %d port = %d parent = %p at %p", dev->device_address,
+              dev->port_number, (void *) dev->parent_dev, priv->dev->sys_path);
+  } while (0);
+
+  if (0 == ret) {
+    usbi_connect_device (dev);
+  } else {
+    libusb_unref_device (dev);
+  }
+
+  return ret;
+}
+
+static int darwin_scan_devices(struct libusb_context *ctx) {
+  io_iterator_t deviceIterator;
+  io_service_t service;
+  kern_return_t kresult;
+
+  kresult = usb_setup_device_iterator (&deviceIterator, 0);
+  if (kresult != kIOReturnSuccess)
+    return darwin_to_libusb (kresult);
+
+  while ((service = IOIteratorNext (deviceIterator))) {
+    (void) process_new_device (ctx, service);
+
+    IOObjectRelease(service);
+  }
+
+  IOObjectRelease(deviceIterator);
+
+  return 0;
+}
+
+static int darwin_open (struct libusb_device_handle *dev_handle) {
+  struct darwin_device_handle_priv *priv = (struct darwin_device_handle_priv *)dev_handle->os_priv;
+  struct darwin_cached_device *dpriv = DARWIN_CACHED_DEVICE(dev_handle->dev);
+  IOReturn kresult;
+
+  if (0 == dpriv->open_count) {
+    /* try to open the device */
+    kresult = (*(dpriv->device))->USBDeviceOpenSeize (dpriv->device);
+    if (kresult != kIOReturnSuccess) {
+      usbi_warn (HANDLE_CTX (dev_handle), "USBDeviceOpen: %s", darwin_error_str(kresult));
+
+      if (kIOReturnExclusiveAccess != kresult) {
+        return darwin_to_libusb (kresult);
+      }
+
+      /* it is possible to perform some actions on a device that is not open so do not return an error */
+      priv->is_open = 0;
+    } else {
+      priv->is_open = 1;
+    }
+
+    /* create async event source */
+    kresult = (*(dpriv->device))->CreateDeviceAsyncEventSource (dpriv->device, &priv->cfSource);
+    if (kresult != kIOReturnSuccess) {
+      usbi_err (HANDLE_CTX (dev_handle), "CreateDeviceAsyncEventSource: %s", darwin_error_str(kresult));
+
+      if (priv->is_open) {
+        (*(dpriv->device))->USBDeviceClose (dpriv->device);
+      }
+
+      priv->is_open = 0;
+
+      return darwin_to_libusb (kresult);
+    }
+
+    CFRetain (libusb_darwin_acfl);
+
+    /* add the cfSource to the aync run loop */
+    CFRunLoopAddSource(libusb_darwin_acfl, priv->cfSource, kCFRunLoopCommonModes);
+  }
+
+  /* device opened successfully */
+  dpriv->open_count++;
+
+  usbi_dbg ("device open for access");
+
+  return 0;
+}
+
+static void darwin_close (struct libusb_device_handle *dev_handle) {
+  struct darwin_device_handle_priv *priv = (struct darwin_device_handle_priv *)dev_handle->os_priv;
+  struct darwin_cached_device *dpriv = DARWIN_CACHED_DEVICE(dev_handle->dev);
+  IOReturn kresult;
+  int i;
+
+  if (dpriv->open_count == 0) {
+    /* something is probably very wrong if this is the case */
+    usbi_err (HANDLE_CTX (dev_handle), "Close called on a device that was not open!");
+    return;
+  }
+
+  dpriv->open_count--;
+
+  /* make sure all interfaces are released */
+  for (i = 0 ; i < USB_MAXINTERFACES ; i++)
+    if (dev_handle->claimed_interfaces & (1 << i))
+      libusb_release_interface (dev_handle, i);
+
+  if (0 == dpriv->open_count) {
+    /* delete the device's async event source */
+    if (priv->cfSource) {
+      CFRunLoopRemoveSource (libusb_darwin_acfl, priv->cfSource, kCFRunLoopDefaultMode);
+      CFRelease (priv->cfSource);
+      priv->cfSource = NULL;
+      CFRelease (libusb_darwin_acfl);
+    }
+
+    if (priv->is_open) {
+      /* close the device */
+      kresult = (*(dpriv->device))->USBDeviceClose(dpriv->device);
+      if (kresult) {
+        /* Log the fact that we had a problem closing the file, however failing a
+         * close isn't really an error, so return success anyway */
+        usbi_warn (HANDLE_CTX (dev_handle), "USBDeviceClose: %s", darwin_error_str(kresult));
+      }
+    }
+  }
+}
+
+static int darwin_get_configuration(struct libusb_device_handle *dev_handle, int *config) {
+  struct darwin_cached_device *dpriv = DARWIN_CACHED_DEVICE(dev_handle->dev);
+
+  *config = (int) dpriv->active_config;
+
+  return 0;
+}
+
+static int darwin_set_configuration(struct libusb_device_handle *dev_handle, int config) {
+  struct darwin_cached_device *dpriv = DARWIN_CACHED_DEVICE(dev_handle->dev);
+  IOReturn kresult;
+  int i;
+
+  /* Setting configuration will invalidate the interface, so we need
+     to reclaim it. First, dispose of existing interfaces, if any. */
+  for (i = 0 ; i < USB_MAXINTERFACES ; i++)
+    if (dev_handle->claimed_interfaces & (1 << i))
+      darwin_release_interface (dev_handle, i);
+
+  kresult = (*(dpriv->device))->SetConfiguration (dpriv->device, config);
+  if (kresult != kIOReturnSuccess)
+    return darwin_to_libusb (kresult);
+
+  /* Reclaim any interfaces. */
+  for (i = 0 ; i < USB_MAXINTERFACES ; i++)
+    if (dev_handle->claimed_interfaces & (1 << i))
+      darwin_claim_interface (dev_handle, i);
+
+  dpriv->active_config = config;
+
+  return 0;
+}
+
+static int darwin_get_interface (usb_device_t **darwin_device, uint8_t ifc, io_service_t *usbInterfacep) {
+  IOUSBFindInterfaceRequest request;
+  kern_return_t             kresult;
+  io_iterator_t             interface_iterator;
+  UInt8                     bInterfaceNumber;
+  int                       ret;
+
+  *usbInterfacep = IO_OBJECT_NULL;
+
+  /* Setup the Interface Request */
+  request.bInterfaceClass    = kIOUSBFindInterfaceDontCare;
+  request.bInterfaceSubClass = kIOUSBFindInterfaceDontCare;
+  request.bInterfaceProtocol = kIOUSBFindInterfaceDontCare;
+  request.bAlternateSetting  = kIOUSBFindInterfaceDontCare;
+
+  kresult = (*(darwin_device))->CreateInterfaceIterator(darwin_device, &request, &interface_iterator);
+  if (kresult)
+    return kresult;
+
+  while ((*usbInterfacep = IOIteratorNext(interface_iterator))) {
+    /* find the interface number */
+    ret = get_ioregistry_value_number (*usbInterfacep, CFSTR("bInterfaceNumber"), kCFNumberSInt8Type,
+                                       &bInterfaceNumber);
+
+    if (ret && bInterfaceNumber == ifc) {
+      break;
+    }
+
+    (void) IOObjectRelease (*usbInterfacep);
+  }
+
+  /* done with the interface iterator */
+  IOObjectRelease(interface_iterator);
+
+  return 0;
+}
+
+static int get_endpoints (struct libusb_device_handle *dev_handle, int iface) {
+  struct darwin_device_handle_priv *priv = (struct darwin_device_handle_priv *)dev_handle->os_priv;
+
+  /* current interface */
+  struct darwin_interface *cInterface = &priv->interfaces[iface];
+
+  kern_return_t kresult;
+
+  u_int8_t numep, direction, number;
+  u_int8_t dont_care1, dont_care3;
+  u_int16_t dont_care2;
+  int rc;
+
+  usbi_dbg ("building table of endpoints.");
+
+  /* retrieve the total number of endpoints on this interface */
+  kresult = (*(cInterface->interface))->GetNumEndpoints(cInterface->interface, &numep);
+  if (kresult) {
+    usbi_err (HANDLE_CTX (dev_handle), "can't get number of endpoints for interface: %s", darwin_error_str(kresult));
+    return darwin_to_libusb (kresult);
+  }
+
+  /* iterate through pipe references */
+  for (int i = 1 ; i <= numep ; i++) {
+    kresult = (*(cInterface->interface))->GetPipeProperties(cInterface->interface, i, &direction, &number, &dont_care1,
+                                                            &dont_care2, &dont_care3);
+
+    if (kresult != kIOReturnSuccess) {
+      /* probably a buggy device. try to get the endpoint address from the descriptors */
+      struct libusb_config_descriptor *config;
+      const struct libusb_endpoint_descriptor *endpoint_desc;
+      UInt8 alt_setting;
+
+      kresult = (*(cInterface->interface))->GetAlternateSetting (cInterface->interface, &alt_setting);
+      if (kresult) {
+        usbi_err (HANDLE_CTX (dev_handle), "can't get alternate setting for interface");
+        return darwin_to_libusb (kresult);
+      }
+
+      rc = libusb_get_active_config_descriptor (dev_handle->dev, &config);
+      if (LIBUSB_SUCCESS != rc) {
+        return rc;
+      }
+
+      endpoint_desc = config->interface[iface].altsetting[alt_setting].endpoint + i - 1;
+
+      cInterface->endpoint_addrs[i - 1] = endpoint_desc->bEndpointAddress;
+    } else {
+      cInterface->endpoint_addrs[i - 1] = (((kUSBIn == direction) << kUSBRqDirnShift) | (number & LIBUSB_ENDPOINT_ADDRESS_MASK));
+    }
+
+    usbi_dbg ("interface: %i pipe %i: dir: %i number: %i", iface, i, cInterface->endpoint_addrs[i - 1] >> kUSBRqDirnShift,
+              cInterface->endpoint_addrs[i - 1] & LIBUSB_ENDPOINT_ADDRESS_MASK);
+  }
+
+  cInterface->num_endpoints = numep;
+
+  return 0;
+}
+
+static int darwin_claim_interface(struct libusb_device_handle *dev_handle, int iface) {
+  struct darwin_cached_device *dpriv = DARWIN_CACHED_DEVICE(dev_handle->dev);
+  struct darwin_device_handle_priv *priv = (struct darwin_device_handle_priv *)dev_handle->os_priv;
+  io_service_t          usbInterface = IO_OBJECT_NULL;
+  IOReturn kresult;
+  IOCFPlugInInterface **plugInInterface = NULL;
+  SInt32                score;
+
+  /* current interface */
+  struct darwin_interface *cInterface = &priv->interfaces[iface];
+
+  kresult = darwin_get_interface (dpriv->device, iface, &usbInterface);
+  if (kresult != kIOReturnSuccess)
+    return darwin_to_libusb (kresult);
+
+  /* make sure we have an interface */
+  if (!usbInterface && dpriv->first_config != 0) {
+    usbi_info (HANDLE_CTX (dev_handle), "no interface found; setting configuration: %d", dpriv->first_config);
+
+    /* set the configuration */
+    kresult = darwin_set_configuration (dev_handle, dpriv->first_config);
+    if (kresult != LIBUSB_SUCCESS) {
+      usbi_err (HANDLE_CTX (dev_handle), "could not set configuration");
+      return kresult;
+    }
+
+    kresult = darwin_get_interface (dpriv->device, iface, &usbInterface);
+    if (kresult) {
+      usbi_err (HANDLE_CTX (dev_handle), "darwin_get_interface: %s", darwin_error_str(kresult));
+      return darwin_to_libusb (kresult);
+    }
+  }
+
+  if (!usbInterface) {
+    usbi_err (HANDLE_CTX (dev_handle), "interface not found");
+    return LIBUSB_ERROR_NOT_FOUND;
+  }
+
+  /* get an interface to the device's interface */
+  kresult = IOCreatePlugInInterfaceForService (usbInterface, kIOUSBInterfaceUserClientTypeID,
+                                               kIOCFPlugInInterfaceID, &plugInInterface, &score);
+
+  /* ignore release error */
+  (void)IOObjectRelease (usbInterface);
+
+  if (kresult) {
+    usbi_err (HANDLE_CTX (dev_handle), "IOCreatePlugInInterfaceForService: %s", darwin_error_str(kresult));
+    return darwin_to_libusb (kresult);
+  }
+
+  if (!plugInInterface) {
+    usbi_err (HANDLE_CTX (dev_handle), "plugin interface not found");
+    return LIBUSB_ERROR_NOT_FOUND;
+  }
+
+  /* Do the actual claim */
+  kresult = (*plugInInterface)->QueryInterface(plugInInterface,
+                                               CFUUIDGetUUIDBytes(kIOUSBInterfaceInterfaceID),
+                                               (LPVOID)&cInterface->interface);
+  /* We no longer need the intermediate plug-in */
+  /* Use release instead of IODestroyPlugInInterface to avoid stopping IOServices associated with this device */
+  (*plugInInterface)->Release (plugInInterface);
+  if (kresult || !cInterface->interface) {
+    usbi_err (HANDLE_CTX (dev_handle), "QueryInterface: %s", darwin_error_str(kresult));
+    return darwin_to_libusb (kresult);
+  }
+
+  /* claim the interface */
+  kresult = (*(cInterface->interface))->USBInterfaceOpen(cInterface->interface);
+  if (kresult) {
+    usbi_err (HANDLE_CTX (dev_handle), "USBInterfaceOpen: %s", darwin_error_str(kresult));
+    return darwin_to_libusb (kresult);
+  }
+
+  /* update list of endpoints */
+  kresult = get_endpoints (dev_handle, iface);
+  if (kresult) {
+    /* this should not happen */
+    darwin_release_interface (dev_handle, iface);
+    usbi_err (HANDLE_CTX (dev_handle), "could not build endpoint table");
+    return kresult;
+  }
+
+  cInterface->cfSource = NULL;
+
+  /* create async event source */
+  kresult = (*(cInterface->interface))->CreateInterfaceAsyncEventSource (cInterface->interface, &cInterface->cfSource);
+  if (kresult != kIOReturnSuccess) {
+    usbi_err (HANDLE_CTX (dev_handle), "could not create async event source");
+
+    /* can't continue without an async event source */
+    (void)darwin_release_interface (dev_handle, iface);
+
+    return darwin_to_libusb (kresult);
+  }
+
+  /* add the cfSource to the async thread's run loop */
+  CFRunLoopAddSource(libusb_darwin_acfl, cInterface->cfSource, kCFRunLoopDefaultMode);
+
+  usbi_dbg ("interface opened");
+
+  return 0;
+}
+
+static int darwin_release_interface(struct libusb_device_handle *dev_handle, int iface) {
+  struct darwin_device_handle_priv *priv = (struct darwin_device_handle_priv *)dev_handle->os_priv;
+  IOReturn kresult;
+
+  /* current interface */
+  struct darwin_interface *cInterface = &priv->interfaces[iface];
+
+  /* Check to see if an interface is open */
+  if (!cInterface->interface)
+    return LIBUSB_SUCCESS;
+
+  /* clean up endpoint data */
+  cInterface->num_endpoints = 0;
+
+  /* delete the interface's async event source */
+  if (cInterface->cfSource) {
+    CFRunLoopRemoveSource (libusb_darwin_acfl, cInterface->cfSource, kCFRunLoopDefaultMode);
+    CFRelease (cInterface->cfSource);
+  }
+
+  kresult = (*(cInterface->interface))->USBInterfaceClose(cInterface->interface);
+  if (kresult)
+    usbi_warn (HANDLE_CTX (dev_handle), "USBInterfaceClose: %s", darwin_error_str(kresult));
+
+  kresult = (*(cInterface->interface))->Release(cInterface->interface);
+  if (kresult != kIOReturnSuccess)
+    usbi_warn (HANDLE_CTX (dev_handle), "Release: %s", darwin_error_str(kresult));
+
+  cInterface->interface = (usb_interface_t **) IO_OBJECT_NULL;
+
+  return darwin_to_libusb (kresult);
+}
+
+static int darwin_set_interface_altsetting(struct libusb_device_handle *dev_handle, int iface, int altsetting) {
+  struct darwin_device_handle_priv *priv = (struct darwin_device_handle_priv *)dev_handle->os_priv;
+  IOReturn kresult;
+
+  /* current interface */
+  struct darwin_interface *cInterface = &priv->interfaces[iface];
+
+  if (!cInterface->interface)
+    return LIBUSB_ERROR_NO_DEVICE;
+
+  kresult = (*(cInterface->interface))->SetAlternateInterface (cInterface->interface, altsetting);
+  if (kresult != kIOReturnSuccess)
+    darwin_reset_device (dev_handle);
+
+  /* update list of endpoints */
+  kresult = get_endpoints (dev_handle, iface);
+  if (kresult) {
+    /* this should not happen */
+    darwin_release_interface (dev_handle, iface);
+    usbi_err (HANDLE_CTX (dev_handle), "could not build endpoint table");
+    return kresult;
+  }
+
+  return darwin_to_libusb (kresult);
+}
+
+static int darwin_clear_halt(struct libusb_device_handle *dev_handle, unsigned char endpoint) {
+  /* current interface */
+  struct darwin_interface *cInterface;
+  IOReturn kresult;
+  uint8_t pipeRef;
+
+  /* determine the interface/endpoint to use */
+  if (ep_to_pipeRef (dev_handle, endpoint, &pipeRef, NULL, &cInterface) != 0) {
+    usbi_err (HANDLE_CTX (dev_handle), "endpoint not found on any open interface");
+
+    return LIBUSB_ERROR_NOT_FOUND;
+  }
+
+  /* newer versions of darwin support clearing additional bits on the device's endpoint */
+  kresult = (*(cInterface->interface))->ClearPipeStallBothEnds(cInterface->interface, pipeRef);
+  if (kresult)
+    usbi_warn (HANDLE_CTX (dev_handle), "ClearPipeStall: %s", darwin_error_str (kresult));
+
+  return darwin_to_libusb (kresult);
+}
+
+static int darwin_reset_device(struct libusb_device_handle *dev_handle) {
+  struct darwin_cached_device *dpriv = DARWIN_CACHED_DEVICE(dev_handle->dev);
+  IOUSBDeviceDescriptor descriptor;
+  IOUSBConfigurationDescriptorPtr cached_configuration;
+  IOUSBConfigurationDescriptor configuration;
+  bool reenumerate = false;
+  IOReturn kresult;
+  int i;
+
+  kresult = (*(dpriv->device))->ResetDevice (dpriv->device);
+  if (kresult) {
+    usbi_err (HANDLE_CTX (dev_handle), "ResetDevice: %s", darwin_error_str (kresult));
+    return darwin_to_libusb (kresult);
+  }
+
+  do {
+    usbi_dbg ("darwin/reset_device: checking if device descriptor changed");
+
+    /* ignore return code. if we can't get a descriptor it might be worthwhile re-enumerating anway */
+    (void) darwin_request_descriptor (dpriv->device, kUSBDeviceDesc, 0, &descriptor, sizeof (descriptor));
+
+    /* check if the device descriptor has changed */
+    if (0 != memcmp (&dpriv->dev_descriptor, &descriptor, sizeof (descriptor))) {
+      reenumerate = true;
+      break;
+    }
+
+    /* check if any configuration descriptor has changed */
+    for (i = 0 ; i < descriptor.bNumConfigurations ; ++i) {
+      usbi_dbg ("darwin/reset_device: checking if configuration descriptor %d changed", i);
+
+      (void) darwin_request_descriptor (dpriv->device, kUSBConfDesc, i, &configuration, sizeof (configuration));
+      (*(dpriv->device))->GetConfigurationDescriptorPtr (dpriv->device, i, &cached_configuration);
+
+      if (!cached_configuration || 0 != memcmp (cached_configuration, &configuration, sizeof (configuration))) {
+        reenumerate = true;
+        break;
+      }
+    }
+  } while (0);
+
+  if (reenumerate) {
+    usbi_dbg ("darwin/reset_device: device requires reenumeration");
+    (void) (*(dpriv->device))->USBDeviceReEnumerate (dpriv->device, 0);
+    return LIBUSB_ERROR_NOT_FOUND;
+  }
+
+  usbi_dbg ("darwin/reset_device: device reset complete");
+
+  return LIBUSB_SUCCESS;
+}
+
+static int darwin_kernel_driver_active(struct libusb_device_handle *dev_handle, int interface) {
+  struct darwin_cached_device *dpriv = DARWIN_CACHED_DEVICE(dev_handle->dev);
+  io_service_t usbInterface;
+  CFTypeRef driver;
+  IOReturn kresult;
+
+  kresult = darwin_get_interface (dpriv->device, interface, &usbInterface);
+  if (kresult) {
+    usbi_err (HANDLE_CTX (dev_handle), "darwin_get_interface: %s", darwin_error_str(kresult));
+
+    return darwin_to_libusb (kresult);
+  }
+
+  driver = IORegistryEntryCreateCFProperty (usbInterface, kIOBundleIdentifierKey, kCFAllocatorDefault, 0);
+  IOObjectRelease (usbInterface);
+
+  if (driver) {
+    CFRelease (driver);
+
+    return 1;
+  }
+
+  /* no driver */
+  return 0;
+}
+
+/* attaching/detaching kernel drivers is not currently supported (maybe in the future?) */
+static int darwin_attach_kernel_driver (struct libusb_device_handle *dev_handle, int interface) {
+  UNUSED(dev_handle);
+  UNUSED(interface);
+  return LIBUSB_ERROR_NOT_SUPPORTED;
+}
+
+static int darwin_detach_kernel_driver (struct libusb_device_handle *dev_handle, int interface) {
+  UNUSED(dev_handle);
+  UNUSED(interface);
+  return LIBUSB_ERROR_NOT_SUPPORTED;
+}
+
+static void darwin_destroy_device(struct libusb_device *dev) {
+  struct darwin_device_priv *dpriv = (struct darwin_device_priv *) dev->os_priv;
+
+  if (dpriv->dev) {
+    /* need to hold the lock in case this is the last reference to the device */
+    usbi_mutex_lock(&darwin_cached_devices_lock);
+    darwin_deref_cached_device (dpriv->dev);
+    dpriv->dev = NULL;
+    usbi_mutex_unlock(&darwin_cached_devices_lock);
+  }
+}
+
+static int submit_bulk_transfer(struct usbi_transfer *itransfer) {
+  struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+
+  IOReturn               ret;
+  uint8_t                transferType;
+  /* None of the values below are used in libusbx for bulk transfers */
+  uint8_t                direction, number, interval, pipeRef;
+  uint16_t               maxPacketSize;
+
+  struct darwin_interface *cInterface;
+
+  if (ep_to_pipeRef (transfer->dev_handle, transfer->endpoint, &pipeRef, NULL, &cInterface) != 0) {
+    usbi_err (TRANSFER_CTX (transfer), "endpoint not found on any open interface");
+
+    return LIBUSB_ERROR_NOT_FOUND;
+  }
+
+  ret = (*(cInterface->interface))->GetPipeProperties (cInterface->interface, pipeRef, &direction, &number,
+                                                       &transferType, &maxPacketSize, &interval);
+
+  if (ret) {
+    usbi_err (TRANSFER_CTX (transfer), "bulk transfer failed (dir = %s): %s (code = 0x%08x)", IS_XFERIN(transfer) ? "In" : "Out",
+              darwin_error_str(ret), ret);
+    return darwin_to_libusb (ret);
+  }
+
+  if (0 != (transfer->length % maxPacketSize)) {
+    /* do not need a zero packet */
+    transfer->flags &= ~LIBUSB_TRANSFER_ADD_ZERO_PACKET;
+  }
+
+  /* submit the request */
+  /* timeouts are unavailable on interrupt endpoints */
+  if (transferType == kUSBInterrupt) {
+    if (IS_XFERIN(transfer))
+      ret = (*(cInterface->interface))->ReadPipeAsync(cInterface->interface, pipeRef, transfer->buffer,
+                                                      transfer->length, darwin_async_io_callback, itransfer);
+    else
+      ret = (*(cInterface->interface))->WritePipeAsync(cInterface->interface, pipeRef, transfer->buffer,
+                                                       transfer->length, darwin_async_io_callback, itransfer);
+  } else {
+    itransfer->timeout_flags |= USBI_TRANSFER_OS_HANDLES_TIMEOUT;
+
+    if (IS_XFERIN(transfer))
+      ret = (*(cInterface->interface))->ReadPipeAsyncTO(cInterface->interface, pipeRef, transfer->buffer,
+                                                        transfer->length, transfer->timeout, transfer->timeout,
+                                                        darwin_async_io_callback, (void *)itransfer);
+    else
+      ret = (*(cInterface->interface))->WritePipeAsyncTO(cInterface->interface, pipeRef, transfer->buffer,
+                                                         transfer->length, transfer->timeout, transfer->timeout,
+                                                         darwin_async_io_callback, (void *)itransfer);
+  }
+
+  if (ret)
+    usbi_err (TRANSFER_CTX (transfer), "bulk transfer failed (dir = %s): %s (code = 0x%08x)", IS_XFERIN(transfer) ? "In" : "Out",
+               darwin_error_str(ret), ret);
+
+  return darwin_to_libusb (ret);
+}
+
+#if InterfaceVersion >= 550
+static int submit_stream_transfer(struct usbi_transfer *itransfer) {
+  struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+  struct darwin_interface *cInterface;
+  uint8_t pipeRef;
+  IOReturn ret;
+
+  if (ep_to_pipeRef (transfer->dev_handle, transfer->endpoint, &pipeRef, NULL, &cInterface) != 0) {
+    usbi_err (TRANSFER_CTX (transfer), "endpoint not found on any open interface");
+
+    return LIBUSB_ERROR_NOT_FOUND;
+  }
+
+  itransfer->timeout_flags |= USBI_TRANSFER_OS_HANDLES_TIMEOUT;
+
+  if (IS_XFERIN(transfer))
+    ret = (*(cInterface->interface))->ReadStreamsPipeAsyncTO(cInterface->interface, pipeRef, itransfer->stream_id,
+                                                             transfer->buffer, transfer->length, transfer->timeout,
+                                                             transfer->timeout, darwin_async_io_callback, (void *)itransfer);
+  else
+    ret = (*(cInterface->interface))->WriteStreamsPipeAsyncTO(cInterface->interface, pipeRef, itransfer->stream_id,
+                                                              transfer->buffer, transfer->length, transfer->timeout,
+                                                              transfer->timeout, darwin_async_io_callback, (void *)itransfer);
+
+  if (ret)
+    usbi_err (TRANSFER_CTX (transfer), "bulk stream transfer failed (dir = %s): %s (code = 0x%08x)", IS_XFERIN(transfer) ? "In" : "Out",
+               darwin_error_str(ret), ret);
+
+  return darwin_to_libusb (ret);
+}
+#endif
+
+static int submit_iso_transfer(struct usbi_transfer *itransfer) {
+  struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+  struct darwin_transfer_priv *tpriv = usbi_transfer_get_os_priv(itransfer);
+
+  IOReturn kresult;
+  uint8_t direction, number, interval, pipeRef, transferType;
+  uint16_t maxPacketSize;
+  UInt64 frame;
+  AbsoluteTime atTime;
+  int i;
+
+  struct darwin_interface *cInterface;
+
+  /* construct an array of IOUSBIsocFrames, reuse the old one if possible */
+  if (tpriv->isoc_framelist && tpriv->num_iso_packets != transfer->num_iso_packets) {
+    free(tpriv->isoc_framelist);
+    tpriv->isoc_framelist = NULL;
+  }
+
+  if (!tpriv->isoc_framelist) {
+    tpriv->num_iso_packets = transfer->num_iso_packets;
+    tpriv->isoc_framelist = (IOUSBIsocFrame*) calloc (transfer->num_iso_packets, sizeof(IOUSBIsocFrame));
+    if (!tpriv->isoc_framelist)
+      return LIBUSB_ERROR_NO_MEM;
+  }
+
+  /* copy the frame list from the libusb descriptor (the structures differ only is member order) */
+  for (i = 0 ; i < transfer->num_iso_packets ; i++)
+    tpriv->isoc_framelist[i].frReqCount = transfer->iso_packet_desc[i].length;
+
+  /* determine the interface/endpoint to use */
+  if (ep_to_pipeRef (transfer->dev_handle, transfer->endpoint, &pipeRef, NULL, &cInterface) != 0) {
+    usbi_err (TRANSFER_CTX (transfer), "endpoint not found on any open interface");
+
+    return LIBUSB_ERROR_NOT_FOUND;
+  }
+
+  /* determine the properties of this endpoint and the speed of the device */
+  (*(cInterface->interface))->GetPipeProperties (cInterface->interface, pipeRef, &direction, &number,
+                                                 &transferType, &maxPacketSize, &interval);
+
+  /* Last but not least we need the bus frame number */
+  kresult = (*(cInterface->interface))->GetBusFrameNumber(cInterface->interface, &frame, &atTime);
+  if (kresult) {
+    usbi_err (TRANSFER_CTX (transfer), "failed to get bus frame number: %d", kresult);
+    free(tpriv->isoc_framelist);
+    tpriv->isoc_framelist = NULL;
+
+    return darwin_to_libusb (kresult);
+  }
+
+  (*(cInterface->interface))->GetPipeProperties (cInterface->interface, pipeRef, &direction, &number,
+                                                 &transferType, &maxPacketSize, &interval);
+
+  /* schedule for a frame a little in the future */
+  frame += 4;
+
+  if (cInterface->frames[transfer->endpoint] && frame < cInterface->frames[transfer->endpoint])
+    frame = cInterface->frames[transfer->endpoint];
+
+  /* submit the request */
+  if (IS_XFERIN(transfer))
+    kresult = (*(cInterface->interface))->ReadIsochPipeAsync(cInterface->interface, pipeRef, transfer->buffer, frame,
+                                                             transfer->num_iso_packets, tpriv->isoc_framelist, darwin_async_io_callback,
+                                                             itransfer);
+  else
+    kresult = (*(cInterface->interface))->WriteIsochPipeAsync(cInterface->interface, pipeRef, transfer->buffer, frame,
+                                                              transfer->num_iso_packets, tpriv->isoc_framelist, darwin_async_io_callback,
+                                                              itransfer);
+
+  if (LIBUSB_SPEED_FULL == transfer->dev_handle->dev->speed)
+    /* Full speed */
+    cInterface->frames[transfer->endpoint] = frame + transfer->num_iso_packets * (1 << (interval - 1));
+  else
+    /* High/super speed */
+    cInterface->frames[transfer->endpoint] = frame + transfer->num_iso_packets * (1 << (interval - 1)) / 8;
+
+  if (kresult != kIOReturnSuccess) {
+    usbi_err (TRANSFER_CTX (transfer), "isochronous transfer failed (dir: %s): %s", IS_XFERIN(transfer) ? "In" : "Out",
+               darwin_error_str(kresult));
+    free (tpriv->isoc_framelist);
+    tpriv->isoc_framelist = NULL;
+  }
+
+  return darwin_to_libusb (kresult);
+}
+
+static int submit_control_transfer(struct usbi_transfer *itransfer) {
+  struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+  struct libusb_control_setup *setup = (struct libusb_control_setup *) transfer->buffer;
+  struct darwin_cached_device *dpriv = DARWIN_CACHED_DEVICE(transfer->dev_handle->dev);
+  struct darwin_transfer_priv *tpriv = usbi_transfer_get_os_priv(itransfer);
+
+  IOReturn               kresult;
+
+  memset(&tpriv->req, 0, sizeof(tpriv->req));
+
+  /* IOUSBDeviceInterface expects the request in cpu endianness */
+  tpriv->req.bmRequestType     = setup->bmRequestType;
+  tpriv->req.bRequest          = setup->bRequest;
+  /* these values should be in bus order from libusb_fill_control_setup */
+  tpriv->req.wValue            = OSSwapLittleToHostInt16 (setup->wValue);
+  tpriv->req.wIndex            = OSSwapLittleToHostInt16 (setup->wIndex);
+  tpriv->req.wLength           = OSSwapLittleToHostInt16 (setup->wLength);
+  /* data is stored after the libusb control block */
+  tpriv->req.pData             = transfer->buffer + LIBUSB_CONTROL_SETUP_SIZE;
+  tpriv->req.completionTimeout = transfer->timeout;
+  tpriv->req.noDataTimeout     = transfer->timeout;
+
+  itransfer->timeout_flags |= USBI_TRANSFER_OS_HANDLES_TIMEOUT;
+
+  /* all transfers in libusb-1.0 are async */
+
+  if (transfer->endpoint) {
+    struct darwin_interface *cInterface;
+    uint8_t                 pipeRef;
+
+    if (ep_to_pipeRef (transfer->dev_handle, transfer->endpoint, &pipeRef, NULL, &cInterface) != 0) {
+      usbi_err (TRANSFER_CTX (transfer), "endpoint not found on any open interface");
+
+      return LIBUSB_ERROR_NOT_FOUND;
+    }
+
+    kresult = (*(cInterface->interface))->ControlRequestAsyncTO (cInterface->interface, pipeRef, &(tpriv->req), darwin_async_io_callback, itransfer);
+  } else
+    /* control request on endpoint 0 */
+    kresult = (*(dpriv->device))->DeviceRequestAsyncTO(dpriv->device, &(tpriv->req), darwin_async_io_callback, itransfer);
+
+  if (kresult != kIOReturnSuccess)
+    usbi_err (TRANSFER_CTX (transfer), "control request failed: %s", darwin_error_str(kresult));
+
+  return darwin_to_libusb (kresult);
+}
+
+static int darwin_submit_transfer(struct usbi_transfer *itransfer) {
+  struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+
+  switch (transfer->type) {
+  case LIBUSB_TRANSFER_TYPE_CONTROL:
+    return submit_control_transfer(itransfer);
+  case LIBUSB_TRANSFER_TYPE_BULK:
+  case LIBUSB_TRANSFER_TYPE_INTERRUPT:
+    return submit_bulk_transfer(itransfer);
+  case LIBUSB_TRANSFER_TYPE_ISOCHRONOUS:
+    return submit_iso_transfer(itransfer);
+  case LIBUSB_TRANSFER_TYPE_BULK_STREAM:
+#if InterfaceVersion >= 550
+    return submit_stream_transfer(itransfer);
+#else
+    usbi_err (TRANSFER_CTX(transfer), "IOUSBFamily version does not support bulk stream transfers");
+    return LIBUSB_ERROR_NOT_SUPPORTED;
+#endif
+  default:
+    usbi_err (TRANSFER_CTX(transfer), "unknown endpoint type %d", transfer->type);
+    return LIBUSB_ERROR_INVALID_PARAM;
+  }
+}
+
+static int cancel_control_transfer(struct usbi_transfer *itransfer) {
+  struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+  struct darwin_cached_device *dpriv = DARWIN_CACHED_DEVICE(transfer->dev_handle->dev);
+  IOReturn kresult;
+
+  usbi_warn (ITRANSFER_CTX (itransfer), "aborting all transactions control pipe");
+
+  if (!dpriv->device)
+    return LIBUSB_ERROR_NO_DEVICE;
+
+  kresult = (*(dpriv->device))->USBDeviceAbortPipeZero (dpriv->device);
+
+  return darwin_to_libusb (kresult);
+}
+
+static int darwin_abort_transfers (struct usbi_transfer *itransfer) {
+  struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+  struct darwin_cached_device *dpriv = DARWIN_CACHED_DEVICE(transfer->dev_handle->dev);
+  struct darwin_interface *cInterface;
+  uint8_t pipeRef, iface;
+  IOReturn kresult;
+
+  if (ep_to_pipeRef (transfer->dev_handle, transfer->endpoint, &pipeRef, &iface, &cInterface) != 0) {
+    usbi_err (TRANSFER_CTX (transfer), "endpoint not found on any open interface");
+
+    return LIBUSB_ERROR_NOT_FOUND;
+  }
+
+  if (!dpriv->device)
+    return LIBUSB_ERROR_NO_DEVICE;
+
+  usbi_warn (ITRANSFER_CTX (itransfer), "aborting all transactions on interface %d pipe %d", iface, pipeRef);
+
+  /* abort transactions */
+#if InterfaceVersion >= 550
+  if (LIBUSB_TRANSFER_TYPE_BULK_STREAM == transfer->type)
+    (*(cInterface->interface))->AbortStreamsPipe (cInterface->interface, pipeRef, itransfer->stream_id);
+  else
+#endif
+    (*(cInterface->interface))->AbortPipe (cInterface->interface, pipeRef);
+
+  usbi_dbg ("calling clear pipe stall to clear the data toggle bit");
+
+  /* newer versions of darwin support clearing additional bits on the device's endpoint */
+  kresult = (*(cInterface->interface))->ClearPipeStallBothEnds(cInterface->interface, pipeRef);
+
+  return darwin_to_libusb (kresult);
+}
+
+static int darwin_cancel_transfer(struct usbi_transfer *itransfer) {
+  struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+
+  switch (transfer->type) {
+  case LIBUSB_TRANSFER_TYPE_CONTROL:
+    return cancel_control_transfer(itransfer);
+  case LIBUSB_TRANSFER_TYPE_BULK:
+  case LIBUSB_TRANSFER_TYPE_INTERRUPT:
+  case LIBUSB_TRANSFER_TYPE_ISOCHRONOUS:
+    return darwin_abort_transfers (itransfer);
+  default:
+    usbi_err (TRANSFER_CTX(transfer), "unknown endpoint type %d", transfer->type);
+    return LIBUSB_ERROR_INVALID_PARAM;
+  }
+}
+
+static void darwin_clear_transfer_priv (struct usbi_transfer *itransfer) {
+  struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+  struct darwin_transfer_priv *tpriv = usbi_transfer_get_os_priv(itransfer);
+
+  if (transfer->type == LIBUSB_TRANSFER_TYPE_ISOCHRONOUS && tpriv->isoc_framelist) {
+    free (tpriv->isoc_framelist);
+    tpriv->isoc_framelist = NULL;
+  }
+}
+
+static void darwin_async_io_callback (void *refcon, IOReturn result, void *arg0) {
+  struct usbi_transfer *itransfer = (struct usbi_transfer *)refcon;
+  struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+  struct darwin_transfer_priv *tpriv = usbi_transfer_get_os_priv(itransfer);
+
+  usbi_dbg ("an async io operation has completed");
+
+  /* if requested write a zero packet */
+  if (kIOReturnSuccess == result && IS_XFEROUT(transfer) && transfer->flags & LIBUSB_TRANSFER_ADD_ZERO_PACKET) {
+    struct darwin_interface *cInterface;
+    uint8_t pipeRef;
+
+    (void) ep_to_pipeRef (transfer->dev_handle, transfer->endpoint, &pipeRef, NULL, &cInterface);
+
+    (*(cInterface->interface))->WritePipe (cInterface->interface, pipeRef, transfer->buffer, 0);
+  }
+
+  tpriv->result = result;
+  tpriv->size = (UInt32) (uintptr_t) arg0;
+
+  /* signal the core that this transfer is complete */
+  usbi_signal_transfer_completion(itransfer);
+}
+
+static int darwin_transfer_status (struct usbi_transfer *itransfer, kern_return_t result) {
+  if (itransfer->timeout_flags & USBI_TRANSFER_TIMED_OUT)
+    result = kIOUSBTransactionTimeout;
+
+  switch (result) {
+  case kIOReturnUnderrun:
+  case kIOReturnSuccess:
+    return LIBUSB_TRANSFER_COMPLETED;
+  case kIOReturnAborted:
+    return LIBUSB_TRANSFER_CANCELLED;
+  case kIOUSBPipeStalled:
+    usbi_dbg ("transfer error: pipe is stalled");
+    return LIBUSB_TRANSFER_STALL;
+  case kIOReturnOverrun:
+    usbi_warn (ITRANSFER_CTX (itransfer), "transfer error: data overrun");
+    return LIBUSB_TRANSFER_OVERFLOW;
+  case kIOUSBTransactionTimeout:
+    usbi_warn (ITRANSFER_CTX (itransfer), "transfer error: timed out");
+    itransfer->timeout_flags |= USBI_TRANSFER_TIMED_OUT;
+    return LIBUSB_TRANSFER_TIMED_OUT;
+  default:
+    usbi_warn (ITRANSFER_CTX (itransfer), "transfer error: %s (value = 0x%08x)", darwin_error_str (result), result);
+    return LIBUSB_TRANSFER_ERROR;
+  }
+}
+
+static int darwin_handle_transfer_completion (struct usbi_transfer *itransfer) {
+  struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+  struct darwin_transfer_priv *tpriv = usbi_transfer_get_os_priv(itransfer);
+  int isIsoc      = LIBUSB_TRANSFER_TYPE_ISOCHRONOUS == transfer->type;
+  int isBulk      = LIBUSB_TRANSFER_TYPE_BULK == transfer->type;
+  int isControl   = LIBUSB_TRANSFER_TYPE_CONTROL == transfer->type;
+  int isInterrupt = LIBUSB_TRANSFER_TYPE_INTERRUPT == transfer->type;
+  int i;
+
+  if (!isIsoc && !isBulk && !isControl && !isInterrupt) {
+    usbi_err (TRANSFER_CTX(transfer), "unknown endpoint type %d", transfer->type);
+    return LIBUSB_ERROR_INVALID_PARAM;
+  }
+
+  usbi_dbg ("handling %s completion with kernel status %d",
+             isControl ? "control" : isBulk ? "bulk" : isIsoc ? "isoc" : "interrupt", tpriv->result);
+
+  if (kIOReturnSuccess == tpriv->result || kIOReturnUnderrun == tpriv->result) {
+    if (isIsoc && tpriv->isoc_framelist) {
+      /* copy isochronous results back */
+
+      for (i = 0; i < transfer->num_iso_packets ; i++) {
+        struct libusb_iso_packet_descriptor *lib_desc = &transfer->iso_packet_desc[i];
+        lib_desc->status = darwin_to_libusb (tpriv->isoc_framelist[i].frStatus);
+        lib_desc->actual_length = tpriv->isoc_framelist[i].frActCount;
+      }
+    } else if (!isIsoc)
+      itransfer->transferred += tpriv->size;
+  }
+
+  /* it is ok to handle cancelled transfers without calling usbi_handle_transfer_cancellation (we catch timeout transfers) */
+  return usbi_handle_transfer_completion (itransfer, darwin_transfer_status (itransfer, tpriv->result));
+}
+
+static int darwin_clock_gettime(int clk_id, struct timespec *tp) {
+  mach_timespec_t sys_time;
+  clock_serv_t clock_ref;
+
+  switch (clk_id) {
+  case USBI_CLOCK_REALTIME:
+    /* CLOCK_REALTIME represents time since the epoch */
+    clock_ref = clock_realtime;
+    break;
+  case USBI_CLOCK_MONOTONIC:
+    /* use system boot time as reference for the monotonic clock */
+    clock_ref = clock_monotonic;
+    break;
+  default:
+    return LIBUSB_ERROR_INVALID_PARAM;
+  }
+
+  clock_get_time (clock_ref, &sys_time);
+
+  tp->tv_sec  = sys_time.tv_sec;
+  tp->tv_nsec = sys_time.tv_nsec;
+
+  return 0;
+}
+
+#if InterfaceVersion >= 550
+static int darwin_alloc_streams (struct libusb_device_handle *dev_handle, uint32_t num_streams, unsigned char *endpoints,
+                                 int num_endpoints) {
+  struct darwin_interface *cInterface;
+  UInt32 supportsStreams;
+  uint8_t pipeRef;
+  int rc, i;
+
+  /* find the mimimum number of supported streams on the endpoint list */
+  for (i = 0 ; i < num_endpoints ; ++i) {
+    if (0 != (rc = ep_to_pipeRef (dev_handle, endpoints[i], &pipeRef, NULL, &cInterface))) {
+      return rc;
+    }
+
+    (*(cInterface->interface))->SupportsStreams (cInterface->interface, pipeRef, &supportsStreams);
+    if (num_streams > supportsStreams)
+      num_streams = supportsStreams;
+  }
+
+  /* it is an error if any endpoint in endpoints does not support streams */
+  if (0 == num_streams)
+    return LIBUSB_ERROR_INVALID_PARAM;
+
+  /* create the streams */
+  for (i = 0 ; i < num_endpoints ; ++i) {
+    (void) ep_to_pipeRef (dev_handle, endpoints[i], &pipeRef, NULL, &cInterface);
+
+    rc = (*(cInterface->interface))->CreateStreams (cInterface->interface, pipeRef, num_streams);
+    if (kIOReturnSuccess != rc)
+      return darwin_to_libusb(rc);
+  }
+
+  return num_streams;
+}
+
+static int darwin_free_streams (struct libusb_device_handle *dev_handle, unsigned char *endpoints, int num_endpoints) {
+  struct darwin_interface *cInterface;
+  UInt32 supportsStreams;
+  uint8_t pipeRef;
+  int rc;
+
+  for (int i = 0 ; i < num_endpoints ; ++i) {
+    if (0 != (rc = ep_to_pipeRef (dev_handle, endpoints[i], &pipeRef, NULL, &cInterface)))
+      return rc;
+
+    (*(cInterface->interface))->SupportsStreams (cInterface->interface, pipeRef, &supportsStreams);
+    if (0 == supportsStreams)
+      return LIBUSB_ERROR_INVALID_PARAM;
+
+    rc = (*(cInterface->interface))->CreateStreams (cInterface->interface, pipeRef, 0);
+    if (kIOReturnSuccess != rc)
+      return darwin_to_libusb(rc);
+  }
+
+  return LIBUSB_SUCCESS;
+}
+#endif
+
+const struct usbi_os_backend darwin_backend = {
+        .name = "Darwin",
+        .caps = 0,
+        .init = darwin_init,
+        .exit = darwin_exit,
+        .get_device_list = NULL, /* not needed */
+        .get_device_descriptor = darwin_get_device_descriptor,
+        .get_active_config_descriptor = darwin_get_active_config_descriptor,
+        .get_config_descriptor = darwin_get_config_descriptor,
+        .hotplug_poll = darwin_hotplug_poll,
+
+        .open = darwin_open,
+        .close = darwin_close,
+        .get_configuration = darwin_get_configuration,
+        .set_configuration = darwin_set_configuration,
+        .claim_interface = darwin_claim_interface,
+        .release_interface = darwin_release_interface,
+
+        .set_interface_altsetting = darwin_set_interface_altsetting,
+        .clear_halt = darwin_clear_halt,
+        .reset_device = darwin_reset_device,
+
+#if InterfaceVersion >= 550
+        .alloc_streams = darwin_alloc_streams,
+        .free_streams = darwin_free_streams,
+#endif
+
+        .kernel_driver_active = darwin_kernel_driver_active,
+        .detach_kernel_driver = darwin_detach_kernel_driver,
+        .attach_kernel_driver = darwin_attach_kernel_driver,
+
+        .destroy_device = darwin_destroy_device,
+
+        .submit_transfer = darwin_submit_transfer,
+        .cancel_transfer = darwin_cancel_transfer,
+        .clear_transfer_priv = darwin_clear_transfer_priv,
+
+        .handle_transfer_completion = darwin_handle_transfer_completion,
+
+        .clock_gettime = darwin_clock_gettime,
+
+        .device_priv_size = sizeof(struct darwin_device_priv),
+        .device_handle_priv_size = sizeof(struct darwin_device_handle_priv),
+        .transfer_priv_size = sizeof(struct darwin_transfer_priv),
+};
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/darwin_usb.h b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/darwin_usb.h
new file mode 100644
index 000000000..118043421
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/darwin_usb.h
@@ -0,0 +1,164 @@
+/*
+ * darwin backend for libusb 1.0
+ * Copyright © 2008-2015 Nathan Hjelm <hjelmn@users.sourceforge.net>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#if !defined(LIBUSB_DARWIN_H)
+#define LIBUSB_DARWIN_H
+
+#include "libusbi.h"
+
+#include <IOKit/IOTypes.h>
+#include <IOKit/IOCFBundle.h>
+#include <IOKit/usb/IOUSBLib.h>
+#include <IOKit/IOCFPlugIn.h>
+
+/* IOUSBInterfaceInferface */
+#if defined (kIOUSBInterfaceInterfaceID700) && MAC_OS_X_VERSION_MIN_REQUIRED >= MAC_OS_X_VERSION_10_9
+
+#define usb_interface_t IOUSBInterfaceInterface700
+#define InterfaceInterfaceID kIOUSBInterfaceInterfaceID700
+#define InterfaceVersion 700
+
+#elif defined (kIOUSBInterfaceInterfaceID550) && MAC_OS_X_VERSION_MIN_REQUIRED >= MAC_OS_X_VERSION_10_9
+
+#define usb_interface_t IOUSBInterfaceInterface550
+#define InterfaceInterfaceID kIOUSBInterfaceInterfaceID550
+#define InterfaceVersion 550
+
+#elif defined (kIOUSBInterfaceInterfaceID500)
+
+#define usb_interface_t IOUSBInterfaceInterface500
+#define InterfaceInterfaceID kIOUSBInterfaceInterfaceID500
+#define InterfaceVersion 500
+
+#elif defined (kIOUSBInterfaceInterfaceID300)
+
+#define usb_interface_t IOUSBInterfaceInterface300
+#define InterfaceInterfaceID kIOUSBInterfaceInterfaceID300
+#define InterfaceVersion 300
+
+#elif defined (kIOUSBInterfaceInterfaceID245)
+
+#define usb_interface_t IOUSBInterfaceInterface245
+#define InterfaceInterfaceID kIOUSBInterfaceInterfaceID245
+#define InterfaceVersion 245
+
+#elif defined (kIOUSBInterfaceInterfaceID220)
+
+#define usb_interface_t IOUSBInterfaceInterface220
+#define InterfaceInterfaceID kIOUSBInterfaceInterfaceID220
+#define InterfaceVersion 220
+
+#else
+
+#error "IOUSBFamily is too old. Please upgrade your OS"
+
+#endif
+
+/* IOUSBDeviceInterface */
+#if defined (kIOUSBDeviceInterfaceID500) && MAC_OS_X_VERSION_MIN_REQUIRED >= MAC_OS_X_VERSION_10_9
+
+#define usb_device_t    IOUSBDeviceInterface500
+#define DeviceInterfaceID kIOUSBDeviceInterfaceID500
+#define DeviceVersion 500
+
+#elif defined (kIOUSBDeviceInterfaceID320)
+
+#define usb_device_t    IOUSBDeviceInterface320
+#define DeviceInterfaceID kIOUSBDeviceInterfaceID320
+#define DeviceVersion 320
+
+#elif defined (kIOUSBDeviceInterfaceID300)
+
+#define usb_device_t    IOUSBDeviceInterface300
+#define DeviceInterfaceID kIOUSBDeviceInterfaceID300
+#define DeviceVersion 300
+
+#elif defined (kIOUSBDeviceInterfaceID245)
+
+#define usb_device_t    IOUSBDeviceInterface245
+#define DeviceInterfaceID kIOUSBDeviceInterfaceID245
+#define DeviceVersion 245
+
+#elif defined (kIOUSBDeviceInterfaceID220)
+#define usb_device_t    IOUSBDeviceInterface197
+#define DeviceInterfaceID kIOUSBDeviceInterfaceID197
+#define DeviceVersion 197
+
+#else
+
+#error "IOUSBFamily is too old. Please upgrade your OS"
+
+#endif
+
+#if !defined(IO_OBJECT_NULL)
+#define IO_OBJECT_NULL ((io_object_t) 0)
+#endif
+
+typedef IOCFPlugInInterface *io_cf_plugin_ref_t;
+typedef IONotificationPortRef io_notification_port_t;
+
+/* private structures */
+struct darwin_cached_device {
+  struct list_head      list;
+  IOUSBDeviceDescriptor dev_descriptor;
+  UInt32                location;
+  UInt64                parent_session;
+  UInt64                session;
+  UInt16                address;
+  char                  sys_path[21];
+  usb_device_t        **device;
+  int                   open_count;
+  UInt8                 first_config, active_config, port;  
+  int                   can_enumerate;
+  int                   refcount;
+};
+
+struct darwin_device_priv {
+  struct darwin_cached_device *dev;
+};
+
+struct darwin_device_handle_priv {
+  int                  is_open;
+  CFRunLoopSourceRef   cfSource;
+
+  struct darwin_interface {
+    usb_interface_t    **interface;
+    uint8_t              num_endpoints;
+    CFRunLoopSourceRef   cfSource;
+    uint64_t             frames[256];
+    uint8_t              endpoint_addrs[USB_MAXENDPOINTS];
+  } interfaces[USB_MAXINTERFACES];
+};
+
+struct darwin_transfer_priv {
+  /* Isoc */
+  IOUSBIsocFrame *isoc_framelist;
+  int num_iso_packets;
+
+  /* Control */
+  IOUSBDevRequestTO req;
+
+  /* Bulk */
+
+  /* Completion status */
+  IOReturn result;
+  UInt32 size;
+};
+
+#endif
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/haiku_pollfs.cpp b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/haiku_pollfs.cpp
new file mode 100644
index 000000000..e0c771320
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/haiku_pollfs.cpp
@@ -0,0 +1,367 @@
+/*
+ * Copyright 2007-2008, Haiku Inc. All rights reserved.
+ * Distributed under the terms of the MIT License.
+ *
+ * Authors:
+ *		Michael Lotz <mmlr@mlotz.ch>
+ */
+
+#include "haiku_usb.h"
+#include <cstdio>
+#include <Directory.h>
+#include <Entry.h>
+#include <Looper.h>
+#include <Messenger.h>
+#include <Node.h>
+#include <NodeMonitor.h>
+#include <Path.h>
+#include <cstring>
+
+class WatchedEntry {
+public:
+			WatchedEntry(BMessenger *, entry_ref *);
+			~WatchedEntry();
+	bool		EntryCreated(entry_ref *ref);
+	bool		EntryRemoved(ino_t node);
+	bool		InitCheck();
+
+private:
+	BMessenger*	fMessenger;
+	node_ref	fNode;
+	bool		fIsDirectory;
+	USBDevice*	fDevice;
+	WatchedEntry*	fEntries;
+	WatchedEntry*	fLink;
+	bool		fInitCheck;
+};
+
+
+class RosterLooper : public BLooper {
+public:
+			RosterLooper(USBRoster *);
+	void		Stop();
+	virtual void	MessageReceived(BMessage *);
+	bool		InitCheck();
+
+private:
+	USBRoster*	fRoster;
+	WatchedEntry*	fRoot;
+	BMessenger*	fMessenger;
+	bool		fInitCheck;
+};
+
+
+WatchedEntry::WatchedEntry(BMessenger *messenger, entry_ref *ref)
+	:	fMessenger(messenger),
+		fIsDirectory(false),
+		fDevice(NULL),
+		fEntries(NULL),
+		fLink(NULL),
+		fInitCheck(false)
+{
+	BEntry entry(ref);
+	entry.GetNodeRef(&fNode);
+
+	BDirectory directory;
+	if (entry.IsDirectory() && directory.SetTo(ref) >= B_OK) {
+		fIsDirectory = true;
+
+		while (directory.GetNextEntry(&entry) >= B_OK) {
+			if (entry.GetRef(ref) < B_OK)
+				continue;
+
+			WatchedEntry *child = new(std::nothrow) WatchedEntry(fMessenger, ref);
+			if (child == NULL)
+				continue;
+			if (child->InitCheck() == false) {
+				delete child;
+				continue;
+			}
+
+			child->fLink = fEntries;
+			fEntries = child;
+		}
+
+		watch_node(&fNode, B_WATCH_DIRECTORY, *fMessenger);
+	}
+	else {
+		if (strncmp(ref->name, "raw", 3) == 0)
+			return;
+
+		BPath path, parent_path;
+		entry.GetPath(&path);
+		fDevice = new(std::nothrow) USBDevice(path.Path());
+		if (fDevice != NULL && fDevice->InitCheck() == true) {
+			// Add this new device to each active context's device list
+			struct libusb_context *ctx;
+			unsigned long session_id = (unsigned long)&fDevice;
+
+			usbi_mutex_lock(&active_contexts_lock);
+			list_for_each_entry(ctx, &active_contexts_list, list, struct libusb_context) {
+				struct libusb_device *dev = usbi_get_device_by_session_id(ctx, session_id);
+				if (dev) {
+					usbi_dbg("using previously allocated device with location %lu", session_id);
+					libusb_unref_device(dev);
+					continue;
+				}
+				usbi_dbg("allocating new device with location %lu", session_id);
+				dev = usbi_alloc_device(ctx, session_id);
+				if (!dev) {
+					usbi_dbg("device allocation failed");
+					continue;
+				}
+				*((USBDevice **)dev->os_priv) = fDevice;
+
+				// Calculate pseudo-device-address
+				int addr, tmp;
+				if (strcmp(path.Leaf(), "hub") == 0)
+					tmp = 100;	//Random Number
+				else
+					sscanf(path.Leaf(), "%d", &tmp);
+				addr = tmp + 1;
+				path.GetParent(&parent_path);
+				while (strcmp(parent_path.Leaf(), "usb") != 0) {
+					sscanf(parent_path.Leaf(), "%d", &tmp);
+					addr += tmp + 1;
+					parent_path.GetParent(&parent_path);
+				}
+				sscanf(path.Path(), "/dev/bus/usb/%d", &dev->bus_number);
+				dev->device_address = addr - (dev->bus_number + 1);
+
+				if (usbi_sanitize_device(dev) < 0) {
+					usbi_dbg("device sanitization failed");
+					libusb_unref_device(dev);
+					continue;
+				}
+				usbi_connect_device(dev);
+			}
+			usbi_mutex_unlock(&active_contexts_lock);
+		}
+		else if (fDevice) {
+			delete fDevice;
+			fDevice = NULL;
+			return;
+		}
+	}
+	fInitCheck = true;
+}
+
+
+WatchedEntry::~WatchedEntry()
+{
+	if (fIsDirectory) {
+		watch_node(&fNode, B_STOP_WATCHING, *fMessenger);
+
+		WatchedEntry *child = fEntries;
+		while (child) {
+			WatchedEntry *next = child->fLink;
+			delete child;
+			child = next;
+		}
+	}
+
+	if (fDevice) {
+		// Remove this device from each active context's device list
+		struct libusb_context *ctx;
+		struct libusb_device *dev;
+		unsigned long session_id = (unsigned long)&fDevice;
+
+		usbi_mutex_lock(&active_contexts_lock);
+		list_for_each_entry(ctx, &active_contexts_list, list, struct libusb_context) {
+			dev = usbi_get_device_by_session_id(ctx, session_id);
+			if (dev != NULL) {
+				usbi_disconnect_device(dev);
+				libusb_unref_device(dev);
+			} else {
+				usbi_dbg("device with location %lu not found", session_id);
+			}
+		}
+		usbi_mutex_static_unlock(&active_contexts_lock);
+		delete fDevice;
+	}
+}
+
+
+bool
+WatchedEntry::EntryCreated(entry_ref *ref)
+{
+	if (!fIsDirectory)
+		return false;
+
+	if (ref->directory != fNode.node) {
+		WatchedEntry *child = fEntries;
+		while (child) {
+			if (child->EntryCreated(ref))
+				return true;
+			child = child->fLink;
+		}
+		return false;
+	}
+
+	WatchedEntry *child = new(std::nothrow) WatchedEntry(fMessenger, ref);
+	if (child == NULL)
+		return false;
+	child->fLink = fEntries;
+	fEntries = child;
+	return true;
+}
+
+
+bool
+WatchedEntry::EntryRemoved(ino_t node)
+{
+	if (!fIsDirectory)
+		return false;
+
+	WatchedEntry *child = fEntries;
+	WatchedEntry *lastChild = NULL;
+	while (child) {
+		if (child->fNode.node == node) {
+			if (lastChild)
+				lastChild->fLink = child->fLink;
+			else
+				fEntries = child->fLink;
+			delete child;
+			return true;
+		}
+
+		if (child->EntryRemoved(node))
+			return true;
+
+		lastChild = child;
+		child = child->fLink;
+	}
+	return false;
+}
+
+
+bool
+WatchedEntry::InitCheck()
+{
+	return fInitCheck;
+}
+
+
+RosterLooper::RosterLooper(USBRoster *roster)
+	:	BLooper("LibusbRoster Looper"),
+		fRoster(roster),
+		fRoot(NULL),
+		fMessenger(NULL),
+		fInitCheck(false)
+{
+	BEntry entry("/dev/bus/usb");
+	if (!entry.Exists()) {
+		usbi_err(NULL, "usb_raw not published");
+		return;
+	}
+
+	Run();
+	fMessenger = new(std::nothrow) BMessenger(this);
+	if (fMessenger == NULL) {
+		usbi_err(NULL, "error creating BMessenger object");
+		return;
+	}
+
+	if (Lock()) {
+		entry_ref ref;
+		entry.GetRef(&ref);
+		fRoot = new(std::nothrow) WatchedEntry(fMessenger, &ref);
+		Unlock();
+		if (fRoot == NULL)
+			return;
+		if (fRoot->InitCheck() == false) {
+			delete fRoot;
+			fRoot = NULL;
+			return;
+		}
+	}
+	fInitCheck = true;
+}
+
+
+void
+RosterLooper::Stop()
+{
+	Lock();
+	delete fRoot;
+	delete fMessenger;
+	Quit();
+}
+
+
+void
+RosterLooper::MessageReceived(BMessage *message)
+{
+	int32 opcode;
+	if (message->FindInt32("opcode", &opcode) < B_OK)
+		return;
+
+	switch (opcode) {
+		case B_ENTRY_CREATED:
+		{
+			dev_t device;
+			ino_t directory;
+			const char *name;
+			if (message->FindInt32("device", &device) < B_OK ||
+				message->FindInt64("directory", &directory) < B_OK ||
+				message->FindString("name", &name) < B_OK)
+				break;
+
+			entry_ref ref(device, directory, name);
+			fRoot->EntryCreated(&ref);
+			break;
+		}
+		case B_ENTRY_REMOVED:
+		{
+			ino_t node;
+			if (message->FindInt64("node", &node) < B_OK)
+				break;
+			fRoot->EntryRemoved(node);
+			break;
+		}
+	}
+}
+
+
+bool
+RosterLooper::InitCheck()
+{
+	return fInitCheck;
+}
+
+
+USBRoster::USBRoster()
+	:	fLooper(NULL)
+{
+}
+
+
+USBRoster::~USBRoster()
+{
+	Stop();
+}
+
+
+int
+USBRoster::Start()
+{
+	if (fLooper == NULL) {
+		fLooper = new(std::nothrow) RosterLooper(this);
+		if (fLooper == NULL || ((RosterLooper *)fLooper)->InitCheck() == false) {
+			if (fLooper)
+				fLooper = NULL;
+			return LIBUSB_ERROR_OTHER;
+		}
+	}
+	return LIBUSB_SUCCESS;
+}
+
+
+void
+USBRoster::Stop()
+{
+	if (fLooper) {
+		((RosterLooper *)fLooper)->Stop();
+		fLooper = NULL;
+	}
+}
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/haiku_usb.h b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/haiku_usb.h
new file mode 100644
index 000000000..d51ae9eae
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/haiku_usb.h
@@ -0,0 +1,112 @@
+/*
+ * Haiku Backend for libusb
+ * Copyright © 2014 Akshay Jaggi <akshay1994.leo@gmail.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <List.h>
+#include <Locker.h>
+#include <Autolock.h>
+#include <USBKit.h>
+#include <map>
+#include "libusbi.h"
+#include "haiku_usb_raw.h"
+
+using namespace std;
+
+class USBDevice;
+class USBDeviceHandle;
+class USBTransfer;
+
+class USBDevice {
+public:
+						USBDevice(const char *);
+	virtual					~USBDevice();
+	const char*				Location() const;
+	uint8					CountConfigurations() const;
+	const usb_device_descriptor*		Descriptor() const;
+	const usb_configuration_descriptor*	ConfigurationDescriptor(uint32) const;
+	const usb_configuration_descriptor*	ActiveConfiguration() const;
+	uint8					EndpointToIndex(uint8) const;
+	uint8					EndpointToInterface(uint8) const;
+	int					ClaimInterface(int);
+	int					ReleaseInterface(int);
+	int					CheckInterfacesFree(int);
+	int					SetActiveConfiguration(int);
+	int					ActiveConfigurationIndex() const;
+	bool					InitCheck();
+private:
+	int					Initialise();
+	unsigned int				fClaimedInterfaces;	// Max Interfaces can be 32. Using a bitmask
+	usb_device_descriptor			fDeviceDescriptor;
+	unsigned char**				fConfigurationDescriptors;
+	int					fActiveConfiguration;
+	char*					fPath;
+	map<uint8,uint8>			fConfigToIndex;
+	map<uint8,uint8>*			fEndpointToIndex;
+	map<uint8,uint8>*			fEndpointToInterface;
+	bool					fInitCheck;
+};
+
+class USBDeviceHandle {
+public:
+				USBDeviceHandle(USBDevice *dev);
+	virtual			~USBDeviceHandle();
+	int			ClaimInterface(int);
+	int			ReleaseInterface(int);
+	int			SetConfiguration(int);
+	int			SetAltSetting(int, int);
+	status_t		SubmitTransfer(struct usbi_transfer *);
+	status_t		CancelTransfer(USBTransfer *);
+	bool			InitCheck();
+private:
+	int			fRawFD;
+	static status_t		TransfersThread(void *);
+	void			TransfersWorker();
+	USBDevice*		fUSBDevice;
+	unsigned int		fClaimedInterfaces;
+	BList			fTransfers;
+	BLocker			fTransfersLock;
+	sem_id			fTransfersSem;
+	thread_id		fTransfersThread;
+	bool			fInitCheck;
+};
+
+class USBTransfer {
+public:
+					USBTransfer(struct usbi_transfer *, USBDevice *);
+	virtual				~USBTransfer();
+	void				Do(int);
+	struct usbi_transfer*		UsbiTransfer();
+	void				SetCancelled();
+	bool				IsCancelled();
+private:
+	struct usbi_transfer*		fUsbiTransfer;
+	struct libusb_transfer*		fLibusbTransfer;
+	USBDevice*			fUSBDevice;
+	BLocker				fStatusLock;
+	bool				fCancelled;
+};
+
+class USBRoster {
+public:
+			USBRoster();
+	virtual		~USBRoster();
+	int		Start();
+	void		Stop();
+private:
+	void*		fLooper;
+};
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/haiku_usb_backend.cpp b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/haiku_usb_backend.cpp
new file mode 100644
index 000000000..d3de8cc08
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/haiku_usb_backend.cpp
@@ -0,0 +1,517 @@
+/*
+ * Haiku Backend for libusb
+ * Copyright © 2014 Akshay Jaggi <akshay1994.leo@gmail.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+
+#include <unistd.h>
+#include <string.h>
+#include <stdlib.h>
+#include <new>
+#include <vector>
+
+#include "haiku_usb.h"
+
+int _errno_to_libusb(int status)
+{
+	return status;
+}
+
+USBTransfer::USBTransfer(struct usbi_transfer *itransfer, USBDevice *device)
+{
+	fUsbiTransfer = itransfer;
+	fLibusbTransfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	fUSBDevice = device;
+	fCancelled = false;
+}
+
+USBTransfer::~USBTransfer()
+{
+}
+
+struct usbi_transfer *
+USBTransfer::UsbiTransfer()
+{
+	return fUsbiTransfer;
+}
+
+void
+USBTransfer::SetCancelled()
+{
+	fCancelled = true;
+}
+
+bool
+USBTransfer::IsCancelled()
+{
+	return fCancelled;
+}
+
+void
+USBTransfer::Do(int fRawFD)
+{
+	switch (fLibusbTransfer->type) {
+		case LIBUSB_TRANSFER_TYPE_CONTROL:
+		{
+			struct libusb_control_setup *setup = (struct libusb_control_setup *)fLibusbTransfer->buffer;
+			usb_raw_command command;
+			command.control.request_type = setup->bmRequestType;
+			command.control.request = setup->bRequest;
+			command.control.value = setup->wValue;
+			command.control.index = setup->wIndex;
+			command.control.length = setup->wLength;
+			command.control.data = fLibusbTransfer->buffer + LIBUSB_CONTROL_SETUP_SIZE;
+			if (fCancelled)
+				break;
+			if (ioctl(fRawFD, B_USB_RAW_COMMAND_CONTROL_TRANSFER, &command, sizeof(command)) ||
+					command.control.status != B_USB_RAW_STATUS_SUCCESS) {
+				fUsbiTransfer->transferred = -1;
+				usbi_err(TRANSFER_CTX(fLibusbTransfer), "failed control transfer");
+				break;
+			}
+			fUsbiTransfer->transferred = command.control.length;
+		}
+		break;
+		case LIBUSB_TRANSFER_TYPE_BULK:
+		case LIBUSB_TRANSFER_TYPE_INTERRUPT:
+		{
+			usb_raw_command command;
+			command.transfer.interface = fUSBDevice->EndpointToInterface(fLibusbTransfer->endpoint);
+			command.transfer.endpoint = fUSBDevice->EndpointToIndex(fLibusbTransfer->endpoint);
+			command.transfer.data = fLibusbTransfer->buffer;
+			command.transfer.length = fLibusbTransfer->length;
+			if (fCancelled)
+				break;
+			if (fLibusbTransfer->type == LIBUSB_TRANSFER_TYPE_BULK) {
+				if (ioctl(fRawFD, B_USB_RAW_COMMAND_BULK_TRANSFER, &command, sizeof(command)) ||
+						command.transfer.status != B_USB_RAW_STATUS_SUCCESS) {
+					fUsbiTransfer->transferred = -1;
+					usbi_err(TRANSFER_CTX(fLibusbTransfer), "failed bulk transfer");
+					break;
+				}
+			}
+			else {
+				if (ioctl(fRawFD, B_USB_RAW_COMMAND_INTERRUPT_TRANSFER, &command, sizeof(command)) ||
+						command.transfer.status != B_USB_RAW_STATUS_SUCCESS) {
+					fUsbiTransfer->transferred = -1;
+					usbi_err(TRANSFER_CTX(fLibusbTransfer), "failed interrupt transfer");
+					break;
+				}
+			}
+			fUsbiTransfer->transferred = command.transfer.length;
+		}
+		break;
+		// IsochronousTransfers not tested
+		case LIBUSB_TRANSFER_TYPE_ISOCHRONOUS:
+		{
+			usb_raw_command command;
+			command.isochronous.interface = fUSBDevice->EndpointToInterface(fLibusbTransfer->endpoint);
+			command.isochronous.endpoint = fUSBDevice->EndpointToIndex(fLibusbTransfer->endpoint);
+			command.isochronous.data = fLibusbTransfer->buffer;
+			command.isochronous.length = fLibusbTransfer->length;
+			command.isochronous.packet_count = fLibusbTransfer->num_iso_packets;
+			int i;
+			usb_iso_packet_descriptor *packetDescriptors = new usb_iso_packet_descriptor[fLibusbTransfer->num_iso_packets];
+			for (i = 0; i < fLibusbTransfer->num_iso_packets; i++) {
+				if ((int16)(fLibusbTransfer->iso_packet_desc[i]).length != (fLibusbTransfer->iso_packet_desc[i]).length) {
+					fUsbiTransfer->transferred = -1;
+					usbi_err(TRANSFER_CTX(fLibusbTransfer), "failed isochronous transfer");
+					break;
+				}
+				packetDescriptors[i].request_length = (int16)(fLibusbTransfer->iso_packet_desc[i]).length;
+			}
+			if (i < fLibusbTransfer->num_iso_packets)
+				break;	// TODO Handle this error
+			command.isochronous.packet_descriptors = packetDescriptors;
+			if (fCancelled)
+				break;
+			if (ioctl(fRawFD, B_USB_RAW_COMMAND_ISOCHRONOUS_TRANSFER, &command, sizeof(command)) ||
+					command.isochronous.status != B_USB_RAW_STATUS_SUCCESS) {
+				fUsbiTransfer->transferred = -1;
+				usbi_err(TRANSFER_CTX(fLibusbTransfer), "failed isochronous transfer");
+				break;
+			}
+			for (i = 0; i < fLibusbTransfer->num_iso_packets; i++) {
+				(fLibusbTransfer->iso_packet_desc[i]).actual_length = packetDescriptors[i].actual_length;
+				switch (packetDescriptors[i].status) {
+					case B_OK:
+						(fLibusbTransfer->iso_packet_desc[i]).status = LIBUSB_TRANSFER_COMPLETED;
+						break;
+					default:
+						(fLibusbTransfer->iso_packet_desc[i]).status = LIBUSB_TRANSFER_ERROR;
+						break;
+				}
+			}
+			delete[] packetDescriptors;
+			// Do we put the length of transfer here, for isochronous transfers?
+			fUsbiTransfer->transferred = command.transfer.length;
+		}
+		break;
+		default:
+			usbi_err(TRANSFER_CTX(fLibusbTransfer), "Unknown type of transfer");
+	}
+}
+
+bool
+USBDeviceHandle::InitCheck()
+{
+	return fInitCheck;
+}
+
+status_t
+USBDeviceHandle::TransfersThread(void *self)
+{
+	USBDeviceHandle *handle = (USBDeviceHandle *)self;
+	handle->TransfersWorker();
+	return B_OK;
+}
+
+void
+USBDeviceHandle::TransfersWorker()
+{
+	while (true) {
+		status_t status = acquire_sem(fTransfersSem);
+		if (status == B_BAD_SEM_ID)
+			break;
+		if (status == B_INTERRUPTED)
+			continue;
+		fTransfersLock.Lock();
+		USBTransfer *fPendingTransfer = (USBTransfer *) fTransfers.RemoveItem((int32)0);
+		fTransfersLock.Unlock();
+		fPendingTransfer->Do(fRawFD);
+		usbi_signal_transfer_completion(fPendingTransfer->UsbiTransfer());
+	}
+}
+
+status_t
+USBDeviceHandle::SubmitTransfer(struct usbi_transfer *itransfer)
+{
+	USBTransfer *transfer = new USBTransfer(itransfer, fUSBDevice);
+	*((USBTransfer **)usbi_transfer_get_os_priv(itransfer)) = transfer;
+	BAutolock locker(fTransfersLock);
+	fTransfers.AddItem(transfer);
+	release_sem(fTransfersSem);
+	return LIBUSB_SUCCESS;
+}
+
+status_t
+USBDeviceHandle::CancelTransfer(USBTransfer *transfer)
+{
+	transfer->SetCancelled();
+	fTransfersLock.Lock();
+	bool removed = fTransfers.RemoveItem(transfer);
+	fTransfersLock.Unlock();
+	if(removed)
+		usbi_signal_transfer_completion(transfer->UsbiTransfer());
+	return LIBUSB_SUCCESS;
+}
+
+USBDeviceHandle::USBDeviceHandle(USBDevice *dev)
+	:
+	fTransfersThread(-1),
+	fUSBDevice(dev),
+	fClaimedInterfaces(0),
+	fInitCheck(false)
+{
+	fRawFD = open(dev->Location(), O_RDWR | O_CLOEXEC);
+	if (fRawFD < 0) {
+		usbi_err(NULL,"failed to open device");
+		return;
+	}
+	fTransfersSem = create_sem(0, "Transfers Queue Sem");
+	fTransfersThread = spawn_thread(TransfersThread, "Transfer Worker", B_NORMAL_PRIORITY, this);
+	resume_thread(fTransfersThread);
+	fInitCheck = true;
+}
+
+USBDeviceHandle::~USBDeviceHandle()
+{
+	if (fRawFD > 0)
+		close(fRawFD);
+	for(int i = 0; i < 32; i++) {
+		if (fClaimedInterfaces & (1 << i))
+			ReleaseInterface(i);
+	}
+	delete_sem(fTransfersSem);
+	if (fTransfersThread > 0)
+		wait_for_thread(fTransfersThread, NULL);
+}
+
+int
+USBDeviceHandle::ClaimInterface(int inumber)
+{
+	int status = fUSBDevice->ClaimInterface(inumber);
+	if (status == LIBUSB_SUCCESS)
+		fClaimedInterfaces |= (1 << inumber);
+	return status;
+}
+
+int
+USBDeviceHandle::ReleaseInterface(int inumber)
+{
+	fUSBDevice->ReleaseInterface(inumber);
+	fClaimedInterfaces &= ~(1 << inumber);
+	return LIBUSB_SUCCESS;
+}
+
+int
+USBDeviceHandle::SetConfiguration(int config)
+{
+	int config_index = fUSBDevice->CheckInterfacesFree(config);
+	if(config_index == LIBUSB_ERROR_BUSY || config_index == LIBUSB_ERROR_NOT_FOUND)
+		return config_index;
+	usb_raw_command command;
+	command.config.config_index = config_index;
+	if (ioctl(fRawFD, B_USB_RAW_COMMAND_SET_CONFIGURATION, &command, sizeof(command)) ||
+			command.config.status != B_USB_RAW_STATUS_SUCCESS) {
+		return _errno_to_libusb(command.config.status);
+	}
+	fUSBDevice->SetActiveConfiguration(config_index);
+	return LIBUSB_SUCCESS;
+}
+
+int
+USBDeviceHandle::SetAltSetting(int inumber, int alt)
+{
+	usb_raw_command command;
+	command.alternate.config_index = fUSBDevice->ActiveConfigurationIndex();
+	command.alternate.interface_index = inumber;
+	if (ioctl(fRawFD, B_USB_RAW_COMMAND_GET_ACTIVE_ALT_INTERFACE_INDEX, &command, sizeof(command)) ||
+			command.alternate.status != B_USB_RAW_STATUS_SUCCESS) {
+		usbi_err(NULL, "Error retrieving active alternate interface");
+		return _errno_to_libusb(command.alternate.status);
+	}
+	if (command.alternate.alternate_info == alt) {
+		usbi_dbg("Setting alternate interface successful");
+		return LIBUSB_SUCCESS;
+	}
+	command.alternate.alternate_info = alt;
+	if (ioctl(fRawFD, B_USB_RAW_COMMAND_SET_ALT_INTERFACE, &command, sizeof(command)) ||
+			command.alternate.status != B_USB_RAW_STATUS_SUCCESS) { //IF IOCTL FAILS DEVICE DISONNECTED PROBABLY
+		usbi_err(NULL, "Error setting alternate interface");
+		return _errno_to_libusb(command.alternate.status);
+	}
+	usbi_dbg("Setting alternate interface successful");
+	return LIBUSB_SUCCESS;
+}
+
+
+USBDevice::USBDevice(const char *path)
+	:
+	fPath(NULL),
+	fActiveConfiguration(0),	//0?
+	fConfigurationDescriptors(NULL),
+	fClaimedInterfaces(0),
+	fEndpointToIndex(NULL),
+	fEndpointToInterface(NULL),
+	fInitCheck(false)
+{
+	fPath=strdup(path);
+	Initialise();
+}
+
+USBDevice::~USBDevice()
+{
+	free(fPath);
+	if (fConfigurationDescriptors) {
+		for(int i = 0; i < fDeviceDescriptor.num_configurations; i++) {
+			if (fConfigurationDescriptors[i])
+				delete fConfigurationDescriptors[i];
+		}
+		delete[] fConfigurationDescriptors;
+	}
+	if (fEndpointToIndex)
+		delete[] fEndpointToIndex;
+	if (fEndpointToInterface)
+		delete[] fEndpointToInterface;
+}
+
+bool
+USBDevice::InitCheck()
+{
+	return fInitCheck;
+}
+
+const char *
+USBDevice::Location() const
+{
+	return fPath;
+}
+
+uint8
+USBDevice::CountConfigurations() const
+{
+	return fDeviceDescriptor.num_configurations;
+}
+
+const usb_device_descriptor *
+USBDevice::Descriptor() const
+{
+	return &fDeviceDescriptor;
+}
+
+const usb_configuration_descriptor *
+USBDevice::ConfigurationDescriptor(uint32 index) const
+{
+	if (index > CountConfigurations())
+		return NULL;
+	return (usb_configuration_descriptor *) fConfigurationDescriptors[index];
+}
+
+const usb_configuration_descriptor *
+USBDevice::ActiveConfiguration() const
+{
+	return (usb_configuration_descriptor *) fConfigurationDescriptors[fActiveConfiguration];
+}
+
+int
+USBDevice::ActiveConfigurationIndex() const
+{
+	return fActiveConfiguration;
+}
+
+int USBDevice::ClaimInterface(int interface)
+{
+	if (interface > ActiveConfiguration()->number_interfaces)
+		return LIBUSB_ERROR_NOT_FOUND;
+	if (fClaimedInterfaces & (1 << interface))
+		return LIBUSB_ERROR_BUSY;
+	fClaimedInterfaces |= (1 << interface);
+	return LIBUSB_SUCCESS;
+}
+
+int USBDevice::ReleaseInterface(int interface)
+{
+	fClaimedInterfaces &= ~(1 << interface);
+	return LIBUSB_SUCCESS;
+}
+
+int
+USBDevice::CheckInterfacesFree(int config)
+{
+	if (fConfigToIndex.count(config) == 0)
+		return LIBUSB_ERROR_NOT_FOUND;
+	if (fClaimedInterfaces == 0)
+		return fConfigToIndex[(uint8)config];
+	return LIBUSB_ERROR_BUSY;
+}
+
+int
+USBDevice::SetActiveConfiguration(int config_index)
+{
+	fActiveConfiguration = config_index;
+	return LIBUSB_SUCCESS;
+}
+
+uint8
+USBDevice::EndpointToIndex(uint8 address) const
+{
+	return fEndpointToIndex[fActiveConfiguration][address];
+}
+
+uint8
+USBDevice::EndpointToInterface(uint8 address) const
+{
+	return fEndpointToInterface[fActiveConfiguration][address];
+}
+
+int
+USBDevice::Initialise()		//Do we need more error checking, etc? How to report?
+{
+	int fRawFD = open(fPath, O_RDWR | O_CLOEXEC);
+	if (fRawFD < 0)
+		return B_ERROR;
+	usb_raw_command command;
+	command.device.descriptor = &fDeviceDescriptor;
+	if (ioctl(fRawFD, B_USB_RAW_COMMAND_GET_DEVICE_DESCRIPTOR, &command, sizeof(command)) ||
+			command.device.status != B_USB_RAW_STATUS_SUCCESS) {
+		close(fRawFD);
+		return B_ERROR;
+	}
+
+	fConfigurationDescriptors = new(std::nothrow) unsigned char *[fDeviceDescriptor.num_configurations];
+	fEndpointToIndex = new(std::nothrow) map<uint8,uint8> [fDeviceDescriptor.num_configurations];
+	fEndpointToInterface = new(std::nothrow) map<uint8,uint8> [fDeviceDescriptor.num_configurations];
+	for (int i = 0; i < fDeviceDescriptor.num_configurations; i++) {
+		usb_configuration_descriptor tmp_config;
+		command.config.descriptor = &tmp_config;
+		command.config.config_index = i;
+		if (ioctl(fRawFD, B_USB_RAW_COMMAND_GET_CONFIGURATION_DESCRIPTOR, &command, sizeof(command)) ||
+				command.config.status != B_USB_RAW_STATUS_SUCCESS) {
+			usbi_err(NULL, "failed retrieving configuration descriptor");
+			close(fRawFD);
+			return B_ERROR;
+		}
+		fConfigToIndex[tmp_config.configuration_value] = i;
+		fConfigurationDescriptors[i] = new(std::nothrow) unsigned char[tmp_config.total_length];
+		command.control.request_type = 128;
+		command.control.request = 6;
+		command.control.value = (2 << 8) | i;
+		command.control.index = 0;
+		command.control.length = tmp_config.total_length;
+		command.control.data = fConfigurationDescriptors[i];
+		if (ioctl(fRawFD, B_USB_RAW_COMMAND_CONTROL_TRANSFER, &command, sizeof(command)) ||
+				command.control.status!=B_USB_RAW_STATUS_SUCCESS) {
+			usbi_err(NULL, "failed retrieving full configuration descriptor");
+			close(fRawFD);
+			return B_ERROR;
+		}
+		for (int j = 0; j < tmp_config.number_interfaces; j++) {
+			command.alternate.config_index = i;
+			command.alternate.interface_index = j;
+			if (ioctl(fRawFD, B_USB_RAW_COMMAND_GET_ALT_INTERFACE_COUNT, &command, sizeof(command)) ||
+					command.config.status != B_USB_RAW_STATUS_SUCCESS) {
+				usbi_err(NULL, "failed retrieving number of alternate interfaces");
+				close(fRawFD);
+				return B_ERROR;
+			}
+			int num_alternate = command.alternate.alternate_info;
+			for (int k = 0; k < num_alternate; k++) {
+				usb_interface_descriptor tmp_interface;
+				command.interface_etc.config_index = i;
+				command.interface_etc.interface_index = j;
+				command.interface_etc.alternate_index = k;
+				command.interface_etc.descriptor = &tmp_interface;
+				if (ioctl(fRawFD, B_USB_RAW_COMMAND_GET_INTERFACE_DESCRIPTOR_ETC, &command, sizeof(command)) ||
+						command.config.status != B_USB_RAW_STATUS_SUCCESS) {
+					usbi_err(NULL, "failed retrieving interface descriptor");
+					close(fRawFD);
+					return B_ERROR;
+				}
+				for (int l = 0; l < tmp_interface.num_endpoints; l++) {
+					usb_endpoint_descriptor tmp_endpoint;
+					command.endpoint_etc.config_index = i;
+					command.endpoint_etc.interface_index = j;
+					command.endpoint_etc.alternate_index = k;
+					command.endpoint_etc.endpoint_index = l;
+					command.endpoint_etc.descriptor = &tmp_endpoint;
+					if (ioctl(fRawFD, B_USB_RAW_COMMAND_GET_ENDPOINT_DESCRIPTOR_ETC, &command, sizeof(command)) ||
+							command.config.status != B_USB_RAW_STATUS_SUCCESS) {
+						usbi_err(NULL, "failed retrieving endpoint descriptor");
+						close(fRawFD);
+						return B_ERROR;
+					}
+					fEndpointToIndex[i][tmp_endpoint.endpoint_address] = l;
+					fEndpointToInterface[i][tmp_endpoint.endpoint_address] = j;
+				}
+			}
+		}
+	}
+	close(fRawFD);
+	fInitCheck = true;
+	return B_OK;
+}
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/haiku_usb_raw.cpp b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/haiku_usb_raw.cpp
new file mode 100644
index 000000000..77adbd1e6
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/haiku_usb_raw.cpp
@@ -0,0 +1,250 @@
+/*
+ * Haiku Backend for libusb
+ * Copyright © 2014 Akshay Jaggi <akshay1994.leo@gmail.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+
+#include <unistd.h>
+#include <string.h>
+#include <stdlib.h>
+#include <new>
+#include <vector>
+
+#include "haiku_usb.h"
+
+USBRoster gUsbRoster;
+int32 gInitCount = 0;
+
+static int
+haiku_init(struct libusb_context *ctx)
+{
+	if (atomic_add(&gInitCount, 1) == 0)
+		return gUsbRoster.Start();
+	return LIBUSB_SUCCESS;
+}
+
+static void
+haiku_exit(void)
+{
+	if (atomic_add(&gInitCount, -1) == 1)
+		gUsbRoster.Stop();
+}
+
+static int
+haiku_open(struct libusb_device_handle *dev_handle)
+{
+	USBDevice *dev = *((USBDevice **)dev_handle->dev->os_priv);
+	USBDeviceHandle *handle = new(std::nothrow) USBDeviceHandle(dev);
+	if (handle == NULL)
+		return LIBUSB_ERROR_NO_MEM;
+	if (handle->InitCheck() == false) {
+		delete handle;
+		return LIBUSB_ERROR_NO_DEVICE;
+	}
+	*((USBDeviceHandle **)dev_handle->os_priv) = handle;
+	return LIBUSB_SUCCESS;
+}
+
+static void
+haiku_close(struct libusb_device_handle *dev_handle)
+{
+	USBDeviceHandle *handle = *((USBDeviceHandle **)dev_handle->os_priv);
+	if (handle == NULL)
+		return;
+	delete handle;
+	*((USBDeviceHandle **)dev_handle->os_priv) = NULL;
+}
+
+static int
+haiku_get_device_descriptor(struct libusb_device *device, unsigned char *buffer, int *host_endian)
+{
+	USBDevice *dev = *((USBDevice **)device->os_priv);
+	memcpy(buffer, dev->Descriptor(), DEVICE_DESC_LENGTH);
+	*host_endian = 0;
+	return LIBUSB_SUCCESS;
+}
+
+static int
+haiku_get_active_config_descriptor(struct libusb_device *device, unsigned char *buffer, size_t len, int *host_endian)
+{
+	USBDevice *dev = *((USBDevice **)device->os_priv);
+	const usb_configuration_descriptor *act_config = dev->ActiveConfiguration();
+	if (len > act_config->total_length)
+		return LIBUSB_ERROR_OVERFLOW;
+	memcpy(buffer, act_config, len);
+	*host_endian = 0;
+	return LIBUSB_SUCCESS;
+}
+
+static int
+haiku_get_config_descriptor(struct libusb_device *device, uint8_t config_index, unsigned char *buffer, size_t len, int *host_endian)
+{
+	USBDevice *dev = *((USBDevice **)device->os_priv);
+	const usb_configuration_descriptor *config = dev->ConfigurationDescriptor(config_index);
+	if (config == NULL) {
+		usbi_err(DEVICE_CTX(device), "failed getting configuration descriptor");
+		return LIBUSB_ERROR_INVALID_PARAM;
+	}
+	if (len > config->total_length)
+		len = config->total_length;
+	memcpy(buffer, config, len);
+	*host_endian = 0;
+	return len;
+}
+
+static int
+haiku_set_configuration(struct libusb_device_handle *dev_handle, int config)
+{
+	USBDeviceHandle *handle= *((USBDeviceHandle **)dev_handle->os_priv);
+	return handle->SetConfiguration(config);
+}
+
+static int
+haiku_claim_interface(struct libusb_device_handle *dev_handle, int interface_number)
+{
+	USBDeviceHandle *handle = *((USBDeviceHandle **)dev_handle->os_priv);
+	return handle->ClaimInterface(interface_number);
+}
+
+static int
+haiku_set_altsetting(struct libusb_device_handle *dev_handle, int interface_number, int altsetting)
+{
+	USBDeviceHandle *handle = *((USBDeviceHandle **)dev_handle->os_priv);
+	return handle->SetAltSetting(interface_number, altsetting);
+}
+
+static int
+haiku_release_interface(struct libusb_device_handle *dev_handle, int interface_number)
+{
+	USBDeviceHandle *handle = *((USBDeviceHandle **)dev_handle->os_priv);
+	haiku_set_altsetting(dev_handle,interface_number, 0);
+	return handle->ReleaseInterface(interface_number);
+}
+
+static int
+haiku_submit_transfer(struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *fLibusbTransfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	USBDeviceHandle *fDeviceHandle = *((USBDeviceHandle **)fLibusbTransfer->dev_handle->os_priv);
+	return fDeviceHandle->SubmitTransfer(itransfer);
+}
+
+static int
+haiku_cancel_transfer(struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *fLibusbTransfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	USBDeviceHandle *fDeviceHandle = *((USBDeviceHandle **)fLibusbTransfer->dev_handle->os_priv);
+	return fDeviceHandle->CancelTransfer(*((USBTransfer **)usbi_transfer_get_os_priv(itransfer)));
+}
+
+static void
+haiku_clear_transfer_priv(struct usbi_transfer *itransfer)
+{
+	USBTransfer *transfer = *((USBTransfer **)usbi_transfer_get_os_priv(itransfer));
+	delete transfer;
+	*((USBTransfer **)usbi_transfer_get_os_priv(itransfer)) = NULL;
+}
+
+static int
+haiku_handle_transfer_completion(struct usbi_transfer *itransfer)
+{
+	USBTransfer *transfer = *((USBTransfer **)usbi_transfer_get_os_priv(itransfer));
+
+	usbi_mutex_lock(&itransfer->lock);
+	if (transfer->IsCancelled()) {
+		delete transfer;
+		*((USBTransfer **)usbi_transfer_get_os_priv(itransfer)) = NULL;
+		usbi_mutex_unlock(&itransfer->lock);
+		if (itransfer->transferred < 0)
+			itransfer->transferred = 0;
+		return usbi_handle_transfer_cancellation(itransfer);
+	}
+	libusb_transfer_status status = LIBUSB_TRANSFER_COMPLETED;
+	if (itransfer->transferred < 0) {
+		usbi_err(ITRANSFER_CTX(itransfer), "error in transfer");
+		status = LIBUSB_TRANSFER_ERROR;
+		itransfer->transferred = 0;
+	}
+	delete transfer;
+	*((USBTransfer **)usbi_transfer_get_os_priv(itransfer)) = NULL;
+	usbi_mutex_unlock(&itransfer->lock);
+	return usbi_handle_transfer_completion(itransfer, status);
+}
+
+static int
+haiku_clock_gettime(int clkid, struct timespec *tp)
+{
+	if (clkid == USBI_CLOCK_REALTIME)
+		return clock_gettime(CLOCK_REALTIME, tp);
+	if (clkid == USBI_CLOCK_MONOTONIC)
+		return clock_gettime(CLOCK_MONOTONIC, tp);
+	return LIBUSB_ERROR_INVALID_PARAM;
+}
+
+const struct usbi_os_backend haiku_usb_raw_backend = {
+	/*.name =*/ "Haiku usbfs",
+	/*.caps =*/ 0,
+	/*.init =*/ haiku_init,
+	/*.exit =*/ haiku_exit,
+	/*.get_device_list =*/ NULL,
+	/*.hotplug_poll =*/ NULL,
+	/*.open =*/ haiku_open,
+	/*.close =*/ haiku_close,
+	/*.get_device_descriptor =*/ haiku_get_device_descriptor,
+	/*.get_active_config_descriptor =*/ haiku_get_active_config_descriptor,
+	/*.get_config_descriptor =*/ haiku_get_config_descriptor,
+	/*.get_config_descriptor_by_value =*/ NULL,
+
+
+	/*.get_configuration =*/ NULL,
+	/*.set_configuration =*/ haiku_set_configuration,
+	/*.claim_interface =*/ haiku_claim_interface,
+	/*.release_interface =*/ haiku_release_interface,
+
+	/*.set_interface_altsetting =*/ haiku_set_altsetting,
+	/*.clear_halt =*/ NULL,
+	/*.reset_device =*/ NULL,
+
+	/*.alloc_streams =*/ NULL,
+	/*.free_streams =*/ NULL,
+
+	/*.dev_mem_alloc =*/ NULL,
+	/*.dev_mem_free =*/ NULL,
+
+	/*.kernel_driver_active =*/ NULL,
+	/*.detach_kernel_driver =*/ NULL,
+	/*.attach_kernel_driver =*/ NULL,
+
+	/*.destroy_device =*/ NULL,
+
+	/*.submit_transfer =*/ haiku_submit_transfer,
+	/*.cancel_transfer =*/ haiku_cancel_transfer,
+	/*.clear_transfer_priv =*/ haiku_clear_transfer_priv,
+
+	/*.handle_events =*/ NULL,
+	/*.handle_transfer_completion =*/ haiku_handle_transfer_completion,
+
+	/*.clock_gettime =*/ haiku_clock_gettime,
+
+#ifdef USBI_TIMERFD_AVAILABLE
+	/*.get_timerfd_clockid =*/ NULL,
+#endif
+
+	/*.device_priv_size =*/ sizeof(USBDevice *),
+	/*.device_handle_priv_size =*/ sizeof(USBDeviceHandle *),
+	/*.transfer_priv_size =*/ sizeof(USBTransfer *),
+};
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/haiku_usb_raw.h b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/haiku_usb_raw.h
new file mode 100644
index 000000000..5baf53d7c
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/haiku_usb_raw.h
@@ -0,0 +1,180 @@
+/*
+ * Copyright 2006-2008, Haiku Inc. All rights reserved.
+ * Distributed under the terms of the MIT License.
+ */
+
+#ifndef _USB_RAW_H_
+#define _USB_RAW_H_
+
+#include <USB3.h>
+
+#define B_USB_RAW_PROTOCOL_VERSION	0x0015
+#define B_USB_RAW_ACTIVE_ALTERNATE	0xffffffff
+
+typedef enum {
+	B_USB_RAW_COMMAND_GET_VERSION = 0x1000,
+
+	B_USB_RAW_COMMAND_GET_DEVICE_DESCRIPTOR = 0x2000,
+	B_USB_RAW_COMMAND_GET_CONFIGURATION_DESCRIPTOR,
+	B_USB_RAW_COMMAND_GET_INTERFACE_DESCRIPTOR,
+	B_USB_RAW_COMMAND_GET_ENDPOINT_DESCRIPTOR,
+	B_USB_RAW_COMMAND_GET_STRING_DESCRIPTOR,
+	B_USB_RAW_COMMAND_GET_GENERIC_DESCRIPTOR,
+	B_USB_RAW_COMMAND_GET_ALT_INTERFACE_COUNT,
+	B_USB_RAW_COMMAND_GET_ACTIVE_ALT_INTERFACE_INDEX,
+	B_USB_RAW_COMMAND_GET_INTERFACE_DESCRIPTOR_ETC,
+	B_USB_RAW_COMMAND_GET_ENDPOINT_DESCRIPTOR_ETC,
+	B_USB_RAW_COMMAND_GET_GENERIC_DESCRIPTOR_ETC,
+
+	B_USB_RAW_COMMAND_SET_CONFIGURATION = 0x3000,
+	B_USB_RAW_COMMAND_SET_FEATURE,
+	B_USB_RAW_COMMAND_CLEAR_FEATURE,
+	B_USB_RAW_COMMAND_GET_STATUS,
+	B_USB_RAW_COMMAND_GET_DESCRIPTOR,
+	B_USB_RAW_COMMAND_SET_ALT_INTERFACE,
+
+	B_USB_RAW_COMMAND_CONTROL_TRANSFER = 0x4000,
+	B_USB_RAW_COMMAND_INTERRUPT_TRANSFER,
+	B_USB_RAW_COMMAND_BULK_TRANSFER,
+	B_USB_RAW_COMMAND_ISOCHRONOUS_TRANSFER
+} usb_raw_command_id;
+
+
+typedef enum {
+	B_USB_RAW_STATUS_SUCCESS = 0,
+
+	B_USB_RAW_STATUS_FAILED,
+	B_USB_RAW_STATUS_ABORTED,
+	B_USB_RAW_STATUS_STALLED,
+	B_USB_RAW_STATUS_CRC_ERROR,
+	B_USB_RAW_STATUS_TIMEOUT,
+
+	B_USB_RAW_STATUS_INVALID_CONFIGURATION,
+	B_USB_RAW_STATUS_INVALID_INTERFACE,
+	B_USB_RAW_STATUS_INVALID_ENDPOINT,
+	B_USB_RAW_STATUS_INVALID_STRING,
+
+	B_USB_RAW_STATUS_NO_MEMORY
+} usb_raw_command_status;
+
+
+typedef union {
+	struct {
+		status_t status;
+	} version;
+
+	struct {
+		status_t status;
+		usb_device_descriptor *descriptor;
+	} device;
+
+	struct {
+		status_t status;
+		usb_configuration_descriptor *descriptor;
+		uint32 config_index;
+	} config;
+
+	struct {
+		status_t status;
+		uint32 alternate_info;
+		uint32 config_index;
+		uint32 interface_index;
+	} alternate;
+
+	struct {
+		status_t status;
+		usb_interface_descriptor *descriptor;
+		uint32 config_index;
+		uint32 interface_index;
+	} interface;
+
+	struct {
+		status_t status;
+		usb_interface_descriptor *descriptor;
+		uint32 config_index;
+		uint32 interface_index;
+		uint32 alternate_index;
+	} interface_etc;
+
+	struct {
+		status_t status;
+		usb_endpoint_descriptor *descriptor;
+		uint32 config_index;
+		uint32 interface_index;
+		uint32 endpoint_index;
+	} endpoint;
+
+	struct {
+		status_t status;
+		usb_endpoint_descriptor *descriptor;
+		uint32 config_index;
+		uint32 interface_index;
+		uint32 alternate_index;
+		uint32 endpoint_index;
+	} endpoint_etc;
+
+	struct {
+		status_t status;
+		usb_descriptor *descriptor;
+		uint32 config_index;
+		uint32 interface_index;
+		uint32 generic_index;
+		size_t length;
+	} generic;
+
+	struct {
+		status_t status;
+		usb_descriptor *descriptor;
+		uint32 config_index;
+		uint32 interface_index;
+		uint32 alternate_index;
+		uint32 generic_index;
+		size_t length;
+	} generic_etc;
+
+	struct {
+		status_t status;
+		usb_string_descriptor *descriptor;
+		uint32 string_index;
+		size_t length;
+	} string;
+
+	struct {
+		status_t status;
+		uint8 type;
+		uint8 index;
+		uint16 language_id;
+		void *data;
+		size_t length;
+	} descriptor;
+
+	struct {
+		status_t status;
+		uint8 request_type;
+		uint8 request;
+		uint16 value;
+		uint16 index;
+		uint16 length;
+		void *data;
+	} control;
+
+	struct {
+		status_t status;
+		uint32 interface;
+		uint32 endpoint;
+		void *data;
+		size_t length;
+	} transfer;
+
+	struct {
+		status_t status;
+		uint32 interface;
+		uint32 endpoint;
+		void *data;
+		size_t length;
+		usb_iso_packet_descriptor *packet_descriptors;
+		uint32 packet_count;
+	} isochronous;
+} usb_raw_command;
+
+#endif // _USB_RAW_H_
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/linux_netlink.c b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/linux_netlink.c
new file mode 100644
index 000000000..60cf3ad1b
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/linux_netlink.c
@@ -0,0 +1,400 @@
+/* -*- Mode: C; c-basic-offset:8 ; indent-tabs-mode:t -*- */
+/*
+ * Linux usbfs backend for libusb
+ * Copyright (C) 2007-2009 Daniel Drake <dsd@gentoo.org>
+ * Copyright (c) 2001 Johannes Erdfelt <johannes@erdfelt.com>
+ * Copyright (c) 2013 Nathan Hjelm <hjelmn@mac.com>
+ * Copyright (c) 2016 Chris Dickens <christopher.a.dickens@gmail.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <config.h>
+
+#include <assert.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <poll.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/types.h>
+
+#ifdef HAVE_ASM_TYPES_H
+#include <asm/types.h>
+#endif
+
+#include <sys/socket.h>
+#include <linux/netlink.h>
+
+#include "libusbi.h"
+#include "linux_usbfs.h"
+
+#define NL_GROUP_KERNEL 1
+
+static int linux_netlink_socket = -1;
+static int netlink_control_pipe[2] = { -1, -1 };
+static pthread_t libusb_linux_event_thread;
+
+static void *linux_netlink_event_thread_main(void *arg);
+
+static int set_fd_cloexec_nb(int fd)
+{
+	int flags;
+
+#if defined(FD_CLOEXEC)
+	flags = fcntl(fd, F_GETFD);
+	if (flags == -1) {
+		usbi_err(NULL, "failed to get netlink fd flags (%d)", errno);
+		return -1;
+	}
+
+	if (!(flags & FD_CLOEXEC)) {
+		if (fcntl(fd, F_SETFD, flags | FD_CLOEXEC) == -1) {
+			usbi_err(NULL, "failed to set netlink fd flags (%d)", errno);
+			return -1;
+		}
+	}
+#endif
+
+	flags = fcntl(fd, F_GETFL);
+	if (flags == -1) {
+		usbi_err(NULL, "failed to get netlink fd status flags (%d)", errno);
+		return -1;
+	}
+
+	if (!(flags & O_NONBLOCK)) {
+		if (fcntl(fd, F_SETFL, flags | O_NONBLOCK) == -1) {
+			usbi_err(NULL, "failed to set netlink fd status flags (%d)", errno);
+			return -1;
+		}
+	}
+
+	return 0;
+}
+
+int linux_netlink_start_event_monitor(void)
+{
+	struct sockaddr_nl sa_nl = { .nl_family = AF_NETLINK, .nl_groups = NL_GROUP_KERNEL };
+	int socktype = SOCK_RAW;
+	int opt = 1;
+	int ret;
+
+#if defined(SOCK_CLOEXEC)
+	socktype |= SOCK_CLOEXEC;
+#endif
+#if defined(SOCK_NONBLOCK)
+	socktype |= SOCK_NONBLOCK;
+#endif
+
+	linux_netlink_socket = socket(PF_NETLINK, socktype, NETLINK_KOBJECT_UEVENT);
+	if (linux_netlink_socket == -1 && errno == EINVAL) {
+		usbi_dbg("failed to create netlink socket of type %d, attempting SOCK_RAW", socktype);
+		linux_netlink_socket = socket(PF_NETLINK, SOCK_RAW, NETLINK_KOBJECT_UEVENT);
+	}
+
+	if (linux_netlink_socket == -1) {
+		usbi_err(NULL, "failed to create netlink socket (%d)", errno);
+		goto err;
+	}
+
+	ret = set_fd_cloexec_nb(linux_netlink_socket);
+	if (ret == -1)
+		goto err_close_socket;
+
+	ret = bind(linux_netlink_socket, (struct sockaddr *)&sa_nl, sizeof(sa_nl));
+	if (ret == -1) {
+		usbi_err(NULL, "failed to bind netlink socket (%d)", errno);
+		goto err_close_socket;
+	}
+
+	ret = setsockopt(linux_netlink_socket, SOL_SOCKET, SO_PASSCRED, &opt, sizeof(opt));
+	if (ret == -1) {
+		usbi_err(NULL, "failed to set netlink socket SO_PASSCRED option (%d)", errno);
+		goto err_close_socket;
+	}
+
+	ret = usbi_pipe(netlink_control_pipe);
+	if (ret) {
+		usbi_err(NULL, "failed to create netlink control pipe");
+		goto err_close_socket;
+	}
+
+	ret = pthread_create(&libusb_linux_event_thread, NULL, linux_netlink_event_thread_main, NULL);
+	if (ret != 0) {
+		usbi_err(NULL, "failed to create netlink event thread (%d)", ret);
+		goto err_close_pipe;
+	}
+
+	return LIBUSB_SUCCESS;
+
+err_close_pipe:
+	close(netlink_control_pipe[0]);
+	close(netlink_control_pipe[1]);
+	netlink_control_pipe[0] = -1;
+	netlink_control_pipe[1] = -1;
+err_close_socket:
+	close(linux_netlink_socket);
+	linux_netlink_socket = -1;
+err:
+	return LIBUSB_ERROR_OTHER;
+}
+
+int linux_netlink_stop_event_monitor(void)
+{
+	char dummy = 1;
+	ssize_t r;
+
+	assert(linux_netlink_socket != -1);
+
+	/* Write some dummy data to the control pipe and
+	 * wait for the thread to exit */
+	r = usbi_write(netlink_control_pipe[1], &dummy, sizeof(dummy));
+	if (r <= 0)
+		usbi_warn(NULL, "netlink control pipe signal failed");
+
+	pthread_join(libusb_linux_event_thread, NULL);
+
+	close(linux_netlink_socket);
+	linux_netlink_socket = -1;
+
+	/* close and reset control pipe */
+	close(netlink_control_pipe[0]);
+	close(netlink_control_pipe[1]);
+	netlink_control_pipe[0] = -1;
+	netlink_control_pipe[1] = -1;
+
+	return LIBUSB_SUCCESS;
+}
+
+static const char *netlink_message_parse(const char *buffer, size_t len, const char *key)
+{
+	const char *end = buffer + len;
+	size_t keylen = strlen(key);
+
+	while (buffer < end && *buffer) {
+		if (strncmp(buffer, key, keylen) == 0 && buffer[keylen] == '=')
+			return buffer + keylen + 1;
+		buffer += strlen(buffer) + 1;
+	}
+
+	return NULL;
+}
+
+/* parse parts of netlink message common to both libudev and the kernel */
+static int linux_netlink_parse(const char *buffer, size_t len, int *detached,
+	const char **sys_name, uint8_t *busnum, uint8_t *devaddr)
+{
+	const char *tmp, *slash;
+
+	errno = 0;
+
+	*sys_name = NULL;
+	*detached = 0;
+	*busnum   = 0;
+	*devaddr  = 0;
+
+	tmp = netlink_message_parse(buffer, len, "ACTION");
+	if (!tmp) {
+		return -1;
+	} else if (strcmp(tmp, "remove") == 0) {
+		*detached = 1;
+	} else if (strcmp(tmp, "add") != 0) {
+		usbi_dbg("unknown device action %s", tmp);
+		return -1;
+	}
+
+	/* check that this is a usb message */
+	tmp = netlink_message_parse(buffer, len, "SUBSYSTEM");
+	if (!tmp || strcmp(tmp, "usb") != 0) {
+		/* not usb. ignore */
+		return -1;
+	}
+
+	/* check that this is an actual usb device */
+	tmp = netlink_message_parse(buffer, len, "DEVTYPE");
+	if (!tmp || strcmp(tmp, "usb_device") != 0) {
+		/* not usb. ignore */
+		return -1;
+	}
+
+	tmp = netlink_message_parse(buffer, len, "BUSNUM");
+	if (tmp) {
+		*busnum = (uint8_t)(strtoul(tmp, NULL, 10) & 0xff);
+		if (errno) {
+			errno = 0;
+			return -1;
+		}
+
+		tmp = netlink_message_parse(buffer, len, "DEVNUM");
+		if (NULL == tmp)
+			return -1;
+
+		*devaddr = (uint8_t)(strtoul(tmp, NULL, 10) & 0xff);
+		if (errno) {
+			errno = 0;
+			return -1;
+		}
+	} else {
+		/* no bus number. try "DEVICE" */
+		tmp = netlink_message_parse(buffer, len, "DEVICE");
+		if (!tmp) {
+			/* not usb. ignore */
+			return -1;
+		}
+
+		/* Parse a device path such as /dev/bus/usb/003/004 */
+		slash = strrchr(tmp, '/');
+		if (!slash)
+			return -1;
+
+		*busnum = (uint8_t)(strtoul(slash - 3, NULL, 10) & 0xff);
+		if (errno) {
+			errno = 0;
+			return -1;
+		}
+
+		*devaddr = (uint8_t)(strtoul(slash + 1, NULL, 10) & 0xff);
+		if (errno) {
+			errno = 0;
+			return -1;
+		}
+
+		return 0;
+	}
+
+	tmp = netlink_message_parse(buffer, len, "DEVPATH");
+	if (!tmp)
+		return -1;
+
+	slash = strrchr(tmp, '/');
+	if (slash)
+		*sys_name = slash + 1;
+
+	/* found a usb device */
+	return 0;
+}
+
+static int linux_netlink_read_message(void)
+{
+	char cred_buffer[CMSG_SPACE(sizeof(struct ucred))];
+	char msg_buffer[2048];
+	const char *sys_name = NULL;
+	uint8_t busnum, devaddr;
+	int detached, r;
+	ssize_t len;
+	struct cmsghdr *cmsg;
+	struct ucred *cred;
+	struct sockaddr_nl sa_nl;
+	struct iovec iov = { .iov_base = msg_buffer, .iov_len = sizeof(msg_buffer) };
+	struct msghdr msg = {
+		.msg_iov = &iov, .msg_iovlen = 1,
+		.msg_control = cred_buffer, .msg_controllen = sizeof(cred_buffer),
+		.msg_name = &sa_nl, .msg_namelen = sizeof(sa_nl)
+	};
+
+	/* read netlink message */
+	len = recvmsg(linux_netlink_socket, &msg, 0);
+	if (len == -1) {
+		if (errno != EAGAIN && errno != EINTR)
+			usbi_err(NULL, "error receiving message from netlink (%d)", errno);
+		return -1;
+	}
+
+	if (len < 32 || (msg.msg_flags & MSG_TRUNC)) {
+		usbi_err(NULL, "invalid netlink message length");
+		return -1;
+	}
+
+	if (sa_nl.nl_groups != NL_GROUP_KERNEL || sa_nl.nl_pid != 0) {
+		usbi_dbg("ignoring netlink message from unknown group/PID (%u/%u)",
+			 (unsigned int)sa_nl.nl_groups, (unsigned int)sa_nl.nl_pid);
+		return -1;
+	}
+
+	cmsg = CMSG_FIRSTHDR(&msg);
+	if (!cmsg || cmsg->cmsg_type != SCM_CREDENTIALS) {
+		usbi_dbg("ignoring netlink message with no sender credentials");
+		return -1;
+	}
+
+	cred = (struct ucred *)CMSG_DATA(cmsg);
+	if (cred->uid != 0) {
+		usbi_dbg("ignoring netlink message with non-zero sender UID %u", (unsigned int)cred->uid);
+		return -1;
+	}
+
+	r = linux_netlink_parse(msg_buffer, (size_t)len, &detached, &sys_name, &busnum, &devaddr);
+	if (r)
+		return r;
+
+	usbi_dbg("netlink hotplug found device busnum: %hhu, devaddr: %hhu, sys_name: %s, removed: %s",
+		 busnum, devaddr, sys_name, detached ? "yes" : "no");
+
+	/* signal device is available (or not) to all contexts */
+	if (detached)
+		linux_device_disconnected(busnum, devaddr);
+	else
+		linux_hotplug_enumerate(busnum, devaddr, sys_name);
+
+	return 0;
+}
+
+static void *linux_netlink_event_thread_main(void *arg)
+{
+	char dummy;
+	ssize_t r;
+	struct pollfd fds[] = {
+		{ .fd = netlink_control_pipe[0],
+		  .events = POLLIN },
+		{ .fd = linux_netlink_socket,
+		  .events = POLLIN },
+	};
+
+	UNUSED(arg);
+
+	usbi_dbg("netlink event thread entering");
+
+	while (poll(fds, 2, -1) >= 0) {
+		if (fds[0].revents & POLLIN) {
+			/* activity on control pipe, read the byte and exit */
+			r = usbi_read(netlink_control_pipe[0], &dummy, sizeof(dummy));
+			if (r <= 0)
+				usbi_warn(NULL, "netlink control pipe read failed");
+			break;
+		}
+		if (fds[1].revents & POLLIN) {
+			usbi_mutex_static_lock(&linux_hotplug_lock);
+			linux_netlink_read_message();
+			usbi_mutex_static_unlock(&linux_hotplug_lock);
+		}
+	}
+
+	usbi_dbg("netlink event thread exiting");
+
+	return NULL;
+}
+
+void linux_netlink_hotplug_poll(void)
+{
+	int r;
+
+	usbi_mutex_static_lock(&linux_hotplug_lock);
+	do {
+		r = linux_netlink_read_message();
+	} while (r == 0);
+	usbi_mutex_static_unlock(&linux_hotplug_lock);
+}
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/linux_udev.c b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/linux_udev.c
new file mode 100644
index 000000000..61d953d8c
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/linux_udev.c
@@ -0,0 +1,311 @@
+/* -*- Mode: C; c-basic-offset:8 ; indent-tabs-mode:t -*- */
+/*
+ * Linux usbfs backend for libusb
+ * Copyright (C) 2007-2009 Daniel Drake <dsd@gentoo.org>
+ * Copyright (c) 2001 Johannes Erdfelt <johannes@erdfelt.com>
+ * Copyright (c) 2012-2013 Nathan Hjelm <hjelmn@mac.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <config.h>
+
+#include <assert.h>
+#include <ctype.h>
+#include <dirent.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <poll.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/utsname.h>
+#include <sys/socket.h>
+#include <unistd.h>
+#include <libudev.h>
+
+#include "libusbi.h"
+#include "linux_usbfs.h"
+
+/* udev context */
+static struct udev *udev_ctx = NULL;
+static int udev_monitor_fd = -1;
+static int udev_control_pipe[2] = {-1, -1};
+static struct udev_monitor *udev_monitor = NULL;
+static pthread_t linux_event_thread;
+
+static void udev_hotplug_event(struct udev_device* udev_dev);
+static void *linux_udev_event_thread_main(void *arg);
+
+int linux_udev_start_event_monitor(void)
+{
+	int r;
+
+	assert(udev_ctx == NULL);
+	udev_ctx = udev_new();
+	if (!udev_ctx) {
+		usbi_err(NULL, "could not create udev context");
+		goto err;
+	}
+
+	udev_monitor = udev_monitor_new_from_netlink(udev_ctx, "udev");
+	if (!udev_monitor) {
+		usbi_err(NULL, "could not initialize udev monitor");
+		goto err_free_ctx;
+	}
+
+	r = udev_monitor_filter_add_match_subsystem_devtype(udev_monitor, "usb", "usb_device");
+	if (r) {
+		usbi_err(NULL, "could not initialize udev monitor filter for \"usb\" subsystem");
+		goto err_free_monitor;
+	}
+
+	if (udev_monitor_enable_receiving(udev_monitor)) {
+		usbi_err(NULL, "failed to enable the udev monitor");
+		goto err_free_monitor;
+	}
+
+	udev_monitor_fd = udev_monitor_get_fd(udev_monitor);
+
+	/* Some older versions of udev are not non-blocking by default,
+	 * so make sure this is set */
+	r = fcntl(udev_monitor_fd, F_GETFL);
+	if (r == -1) {
+		usbi_err(NULL, "getting udev monitor fd flags (%d)", errno);
+		goto err_free_monitor;
+	}
+	r = fcntl(udev_monitor_fd, F_SETFL, r | O_NONBLOCK);
+	if (r) {
+		usbi_err(NULL, "setting udev monitor fd flags (%d)", errno);
+		goto err_free_monitor;
+	}
+
+	r = usbi_pipe(udev_control_pipe);
+	if (r) {
+		usbi_err(NULL, "could not create udev control pipe");
+		goto err_free_monitor;
+	}
+
+	r = pthread_create(&linux_event_thread, NULL, linux_udev_event_thread_main, NULL);
+	if (r) {
+		usbi_err(NULL, "creating hotplug event thread (%d)", r);
+		goto err_close_pipe;
+	}
+
+	return LIBUSB_SUCCESS;
+
+err_close_pipe:
+	close(udev_control_pipe[0]);
+	close(udev_control_pipe[1]);
+err_free_monitor:
+	udev_monitor_unref(udev_monitor);
+	udev_monitor = NULL;
+	udev_monitor_fd = -1;
+err_free_ctx:
+	udev_unref(udev_ctx);
+err:
+	udev_ctx = NULL;
+	return LIBUSB_ERROR_OTHER;
+}
+
+int linux_udev_stop_event_monitor(void)
+{
+	char dummy = 1;
+	int r;
+
+	assert(udev_ctx != NULL);
+	assert(udev_monitor != NULL);
+	assert(udev_monitor_fd != -1);
+
+	/* Write some dummy data to the control pipe and
+	 * wait for the thread to exit */
+	r = usbi_write(udev_control_pipe[1], &dummy, sizeof(dummy));
+	if (r <= 0) {
+		usbi_warn(NULL, "udev control pipe signal failed");
+	}
+	pthread_join(linux_event_thread, NULL);
+
+	/* Release the udev monitor */
+	udev_monitor_unref(udev_monitor);
+	udev_monitor = NULL;
+	udev_monitor_fd = -1;
+
+	/* Clean up the udev context */
+	udev_unref(udev_ctx);
+	udev_ctx = NULL;
+
+	/* close and reset control pipe */
+	close(udev_control_pipe[0]);
+	close(udev_control_pipe[1]);
+	udev_control_pipe[0] = -1;
+	udev_control_pipe[1] = -1;
+
+	return LIBUSB_SUCCESS;
+}
+
+static void *linux_udev_event_thread_main(void *arg)
+{
+	char dummy;
+	int r;
+	struct udev_device* udev_dev;
+	struct pollfd fds[] = {
+		{.fd = udev_control_pipe[0],
+		 .events = POLLIN},
+		{.fd = udev_monitor_fd,
+		 .events = POLLIN},
+	};
+
+	usbi_dbg("udev event thread entering.");
+
+	while ((r = poll(fds, 2, -1)) >= 0 || errno == EINTR) {
+		if (r < 0) {
+			/* temporary failure */
+			continue;
+		}
+		if (fds[0].revents & POLLIN) {
+			/* activity on control pipe, read the byte and exit */
+			r = usbi_read(udev_control_pipe[0], &dummy, sizeof(dummy));
+			if (r <= 0) {
+				usbi_warn(NULL, "udev control pipe read failed");
+			}
+			break;
+		}
+		if (fds[1].revents & POLLIN) {
+			usbi_mutex_static_lock(&linux_hotplug_lock);
+			udev_dev = udev_monitor_receive_device(udev_monitor);
+			if (udev_dev)
+				udev_hotplug_event(udev_dev);
+			usbi_mutex_static_unlock(&linux_hotplug_lock);
+		}
+	}
+
+	usbi_dbg("udev event thread exiting");
+
+	return NULL;
+}
+
+static int udev_device_info(struct libusb_context *ctx, int detached,
+			    struct udev_device *udev_dev, uint8_t *busnum,
+			    uint8_t *devaddr, const char **sys_name) {
+	const char *dev_node;
+
+	dev_node = udev_device_get_devnode(udev_dev);
+	if (!dev_node) {
+		return LIBUSB_ERROR_OTHER;
+	}
+
+	*sys_name = udev_device_get_sysname(udev_dev);
+	if (!*sys_name) {
+		return LIBUSB_ERROR_OTHER;
+	}
+
+	return linux_get_device_address(ctx, detached, busnum, devaddr,
+					dev_node, *sys_name);
+}
+
+static void udev_hotplug_event(struct udev_device* udev_dev)
+{
+	const char* udev_action;
+	const char* sys_name = NULL;
+	uint8_t busnum = 0, devaddr = 0;
+	int detached;
+	int r;
+
+	do {
+		udev_action = udev_device_get_action(udev_dev);
+		if (!udev_action) {
+			break;
+		}
+
+		detached = !strncmp(udev_action, "remove", 6);
+
+		r = udev_device_info(NULL, detached, udev_dev, &busnum, &devaddr, &sys_name);
+		if (LIBUSB_SUCCESS != r) {
+			break;
+		}
+
+		usbi_dbg("udev hotplug event. action: %s.", udev_action);
+
+		if (strncmp(udev_action, "add", 3) == 0) {
+			linux_hotplug_enumerate(busnum, devaddr, sys_name);
+		} else if (detached) {
+			linux_device_disconnected(busnum, devaddr);
+		} else {
+			usbi_err(NULL, "ignoring udev action %s", udev_action);
+		}
+	} while (0);
+
+	udev_device_unref(udev_dev);
+}
+
+int linux_udev_scan_devices(struct libusb_context *ctx)
+{
+	struct udev_enumerate *enumerator;
+	struct udev_list_entry *devices, *entry;
+	struct udev_device *udev_dev;
+	const char *sys_name;
+	int r;
+
+	assert(udev_ctx != NULL);
+
+	enumerator = udev_enumerate_new(udev_ctx);
+	if (NULL == enumerator) {
+		usbi_err(ctx, "error creating udev enumerator");
+		return LIBUSB_ERROR_OTHER;
+	}
+
+	udev_enumerate_add_match_subsystem(enumerator, "usb");
+	udev_enumerate_add_match_property(enumerator, "DEVTYPE", "usb_device");
+	udev_enumerate_scan_devices(enumerator);
+	devices = udev_enumerate_get_list_entry(enumerator);
+
+	udev_list_entry_foreach(entry, devices) {
+		const char *path = udev_list_entry_get_name(entry);
+		uint8_t busnum = 0, devaddr = 0;
+
+		udev_dev = udev_device_new_from_syspath(udev_ctx, path);
+
+		r = udev_device_info(ctx, 0, udev_dev, &busnum, &devaddr, &sys_name);
+		if (r) {
+			udev_device_unref(udev_dev);
+			continue;
+		}
+
+		linux_enumerate_device(ctx, busnum, devaddr, sys_name);
+		udev_device_unref(udev_dev);
+	}
+
+	udev_enumerate_unref(enumerator);
+
+	return LIBUSB_SUCCESS;
+}
+
+void linux_udev_hotplug_poll(void)
+{
+	struct udev_device* udev_dev;
+
+	usbi_mutex_static_lock(&linux_hotplug_lock);
+	do {
+		udev_dev = udev_monitor_receive_device(udev_monitor);
+		if (udev_dev) {
+			usbi_dbg("Handling hotplug event from hotplug_poll");
+			udev_hotplug_event(udev_dev);
+		}
+	} while (udev_dev);
+	usbi_mutex_static_unlock(&linux_hotplug_lock);
+}
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/linux_usbfs.c b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/linux_usbfs.c
new file mode 100644
index 000000000..6b89ba288
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/linux_usbfs.c
@@ -0,0 +1,2738 @@
+/* -*- Mode: C; c-basic-offset:8 ; indent-tabs-mode:t -*- */
+/*
+ * Linux usbfs backend for libusb
+ * Copyright © 2007-2009 Daniel Drake <dsd@gentoo.org>
+ * Copyright © 2001 Johannes Erdfelt <johannes@erdfelt.com>
+ * Copyright © 2013 Nathan Hjelm <hjelmn@mac.com>
+ * Copyright © 2012-2013 Hans de Goede <hdegoede@redhat.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "config.h"
+
+#include <assert.h>
+#include <ctype.h>
+#include <dirent.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <poll.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/utsname.h>
+#include <time.h>
+
+#include "libusbi.h"
+#include "linux_usbfs.h"
+
+/* sysfs vs usbfs:
+ * opening a usbfs node causes the device to be resumed, so we attempt to
+ * avoid this during enumeration.
+ *
+ * sysfs allows us to read the kernel's in-memory copies of device descriptors
+ * and so forth, avoiding the need to open the device:
+ *  - The binary "descriptors" file contains all config descriptors since
+ *    2.6.26, commit 217a9081d8e69026186067711131b77f0ce219ed
+ *  - The binary "descriptors" file was added in 2.6.23, commit
+ *    69d42a78f935d19384d1f6e4f94b65bb162b36df, but it only contains the
+ *    active config descriptors
+ *  - The "busnum" file was added in 2.6.22, commit
+ *    83f7d958eab2fbc6b159ee92bf1493924e1d0f72
+ *  - The "devnum" file has been present since pre-2.6.18
+ *  - the "bConfigurationValue" file has been present since pre-2.6.18
+ *
+ * If we have bConfigurationValue, busnum, and devnum, then we can determine
+ * the active configuration without having to open the usbfs node in RDWR mode.
+ * The busnum file is important as that is the only way we can relate sysfs
+ * devices to usbfs nodes.
+ *
+ * If we also have all descriptors, we can obtain the device descriptor and
+ * configuration without touching usbfs at all.
+ */
+
+/* endianness for multi-byte fields:
+ *
+ * Descriptors exposed by usbfs have the multi-byte fields in the device
+ * descriptor as host endian. Multi-byte fields in the other descriptors are
+ * bus-endian. The kernel documentation says otherwise, but it is wrong.
+ *
+ * In sysfs all descriptors are bus-endian.
+ */
+
+static const char *usbfs_path = NULL;
+
+/* use usbdev*.* device names in /dev instead of the usbfs bus directories */
+static int usbdev_names = 0;
+
+/* Linux 2.6.32 adds support for a bulk continuation URB flag. this basically
+ * allows us to mark URBs as being part of a specific logical transfer when
+ * we submit them to the kernel. then, on any error except a cancellation, all
+ * URBs within that transfer will be cancelled and no more URBs will be
+ * accepted for the transfer, meaning that no more data can creep in.
+ *
+ * The BULK_CONTINUATION flag must be set on all URBs within a bulk transfer
+ * (in either direction) except the first.
+ * For IN transfers, we must also set SHORT_NOT_OK on all URBs except the
+ * last; it means that the kernel should treat a short reply as an error.
+ * For OUT transfers, SHORT_NOT_OK must not be set. it isn't needed (OUT
+ * transfers can't be short unless there's already some sort of error), and
+ * setting this flag is disallowed (a kernel with USB debugging enabled will
+ * reject such URBs).
+ */
+static int supports_flag_bulk_continuation = -1;
+
+/* Linux 2.6.31 fixes support for the zero length packet URB flag. This
+ * allows us to mark URBs that should be followed by a zero length data
+ * packet, which can be required by device- or class-specific protocols.
+ */
+static int supports_flag_zero_packet = -1;
+
+/* clock ID for monotonic clock, as not all clock sources are available on all
+ * systems. appropriate choice made at initialization time. */
+static clockid_t monotonic_clkid = -1;
+
+/* Linux 2.6.22 (commit 83f7d958eab2fbc6b159ee92bf1493924e1d0f72) adds a busnum
+ * to sysfs, so we can relate devices. This also implies that we can read
+ * the active configuration through bConfigurationValue */
+static int sysfs_can_relate_devices = -1;
+
+/* Linux 2.6.26 (commit 217a9081d8e69026186067711131b77f0ce219ed) adds all
+ * config descriptors (rather then just the active config) to the sysfs
+ * descriptors file, so from then on we can use them. */
+static int sysfs_has_descriptors = -1;
+
+/* how many times have we initted (and not exited) ? */
+static int init_count = 0;
+
+/* Serialize hotplug start/stop */
+static usbi_mutex_static_t linux_hotplug_startstop_lock = USBI_MUTEX_INITIALIZER;
+/* Serialize scan-devices, event-thread, and poll */
+usbi_mutex_static_t linux_hotplug_lock = USBI_MUTEX_INITIALIZER;
+
+static int linux_start_event_monitor(void);
+static int linux_stop_event_monitor(void);
+static int linux_scan_devices(struct libusb_context *ctx);
+static int sysfs_scan_device(struct libusb_context *ctx, const char *devname);
+static int detach_kernel_driver_and_claim(struct libusb_device_handle *, int);
+
+#if !defined(USE_UDEV)
+static int linux_default_scan_devices (struct libusb_context *ctx);
+#endif
+
+struct linux_device_priv {
+	char *sysfs_dir;
+	unsigned char *descriptors;
+	int descriptors_len;
+	int active_config; /* cache val for !sysfs_can_relate_devices  */
+};
+
+struct linux_device_handle_priv {
+	int fd;
+	int fd_removed;
+	uint32_t caps;
+};
+
+enum reap_action {
+	NORMAL = 0,
+	/* submission failed after the first URB, so await cancellation/completion
+	 * of all the others */
+	SUBMIT_FAILED,
+
+	/* cancelled by user or timeout */
+	CANCELLED,
+
+	/* completed multi-URB transfer in non-final URB */
+	COMPLETED_EARLY,
+
+	/* one or more urbs encountered a low-level error */
+	ERROR,
+};
+
+struct linux_transfer_priv {
+	union {
+		struct usbfs_urb *urbs;
+		struct usbfs_urb **iso_urbs;
+	};
+
+	enum reap_action reap_action;
+	int num_urbs;
+	int num_retired;
+	enum libusb_transfer_status reap_status;
+
+	/* next iso packet in user-supplied transfer to be populated */
+	int iso_packet_offset;
+};
+
+static int _get_usbfs_fd(struct libusb_device *dev, mode_t mode, int silent)
+{
+	struct libusb_context *ctx = DEVICE_CTX(dev);
+	char path[PATH_MAX];
+	int fd;
+	int delay = 10000;
+
+	if (usbdev_names)
+		snprintf(path, PATH_MAX, "%s/usbdev%d.%d",
+			usbfs_path, dev->bus_number, dev->device_address);
+	else
+		snprintf(path, PATH_MAX, "%s/%03d/%03d",
+			usbfs_path, dev->bus_number, dev->device_address);
+
+	fd = open(path, mode);
+	if (fd != -1)
+		return fd; /* Success */
+
+	if (errno == ENOENT) {
+		if (!silent) 
+			usbi_err(ctx, "File doesn't exist, wait %d ms and try again", delay/1000);
+   
+		/* Wait 10ms for USB device path creation.*/
+		nanosleep(&(struct timespec){delay / 1000000, (delay * 1000) % 1000000000UL}, NULL);
+
+		fd = open(path, mode);
+		if (fd != -1)
+			return fd; /* Success */
+	}
+	
+	if (!silent) {
+		usbi_err(ctx, "libusb couldn't open USB device %s: %s",
+			 path, strerror(errno));
+		if (errno == EACCES && mode == O_RDWR)
+			usbi_err(ctx, "libusb requires write access to USB "
+				      "device nodes.");
+	}
+
+	if (errno == EACCES)
+		return LIBUSB_ERROR_ACCESS;
+	if (errno == ENOENT)
+		return LIBUSB_ERROR_NO_DEVICE;
+	return LIBUSB_ERROR_IO;
+}
+
+static struct linux_device_priv *_device_priv(struct libusb_device *dev)
+{
+	return (struct linux_device_priv *) dev->os_priv;
+}
+
+static struct linux_device_handle_priv *_device_handle_priv(
+	struct libusb_device_handle *handle)
+{
+	return (struct linux_device_handle_priv *) handle->os_priv;
+}
+
+/* check dirent for a /dev/usbdev%d.%d name
+ * optionally return bus/device on success */
+static int _is_usbdev_entry(struct dirent *entry, int *bus_p, int *dev_p)
+{
+	int busnum, devnum;
+
+	if (sscanf(entry->d_name, "usbdev%d.%d", &busnum, &devnum) != 2)
+		return 0;
+
+	usbi_dbg("found: %s", entry->d_name);
+	if (bus_p != NULL)
+		*bus_p = busnum;
+	if (dev_p != NULL)
+		*dev_p = devnum;
+	return 1;
+}
+
+static int check_usb_vfs(const char *dirname)
+{
+	DIR *dir;
+	struct dirent *entry;
+	int found = 0;
+
+	dir = opendir(dirname);
+	if (!dir)
+		return 0;
+
+	while ((entry = readdir(dir)) != NULL) {
+		if (entry->d_name[0] == '.')
+			continue;
+
+		/* We assume if we find any files that it must be the right place */
+		found = 1;
+		break;
+	}
+
+	closedir(dir);
+	return found;
+}
+
+static const char *find_usbfs_path(void)
+{
+	const char *path = "/dev/bus/usb";
+	const char *ret = NULL;
+
+	if (check_usb_vfs(path)) {
+		ret = path;
+	} else {
+		path = "/proc/bus/usb";
+		if (check_usb_vfs(path))
+			ret = path;
+	}
+
+	/* look for /dev/usbdev*.* if the normal places fail */
+	if (ret == NULL) {
+		struct dirent *entry;
+		DIR *dir;
+
+		path = "/dev";
+		dir = opendir(path);
+		if (dir != NULL) {
+			while ((entry = readdir(dir)) != NULL) {
+				if (_is_usbdev_entry(entry, NULL, NULL)) {
+					/* found one; that's enough */
+					ret = path;
+					usbdev_names = 1;
+					break;
+				}
+			}
+			closedir(dir);
+		}
+	}
+
+/* On udev based systems without any usb-devices /dev/bus/usb will not
+ * exist. So if we've not found anything and we're using udev for hotplug
+ * simply assume /dev/bus/usb rather then making libusb_init fail. */
+#if defined(USE_UDEV)
+	if (ret == NULL)
+		ret = "/dev/bus/usb";
+#endif
+
+	if (ret != NULL)
+		usbi_dbg("found usbfs at %s", ret);
+
+	return ret;
+}
+
+/* the monotonic clock is not usable on all systems (e.g. embedded ones often
+ * seem to lack it). fall back to REALTIME if we have to. */
+static clockid_t find_monotonic_clock(void)
+{
+#ifdef CLOCK_MONOTONIC
+	struct timespec ts;
+	int r;
+
+	/* Linux 2.6.28 adds CLOCK_MONOTONIC_RAW but we don't use it
+	 * because it's not available through timerfd */
+	r = clock_gettime(CLOCK_MONOTONIC, &ts);
+	if (r == 0)
+		return CLOCK_MONOTONIC;
+	usbi_dbg("monotonic clock doesn't work, errno %d", errno);
+#endif
+
+	return CLOCK_REALTIME;
+}
+
+static int kernel_version_ge(int major, int minor, int sublevel)
+{
+	struct utsname uts;
+	int atoms, kmajor, kminor, ksublevel;
+
+	if (uname(&uts) < 0)
+		return -1;
+	atoms = sscanf(uts.release, "%d.%d.%d", &kmajor, &kminor, &ksublevel);
+	if (atoms < 1)
+		return -1;
+
+	if (kmajor > major)
+		return 1;
+	if (kmajor < major)
+		return 0;
+
+	/* kmajor == major */
+	if (atoms < 2)
+		return 0 == minor && 0 == sublevel;
+	if (kminor > minor)
+		return 1;
+	if (kminor < minor)
+		return 0;
+
+	/* kminor == minor */
+	if (atoms < 3)
+		return 0 == sublevel;
+
+	return ksublevel >= sublevel;
+}
+
+static int op_init(struct libusb_context *ctx)
+{
+	struct stat statbuf;
+	int r;
+
+	usbfs_path = find_usbfs_path();
+	if (!usbfs_path) {
+		usbi_err(ctx, "could not find usbfs");
+		return LIBUSB_ERROR_OTHER;
+	}
+
+	if (monotonic_clkid == -1)
+		monotonic_clkid = find_monotonic_clock();
+
+	if (supports_flag_bulk_continuation == -1) {
+		/* bulk continuation URB flag available from Linux 2.6.32 */
+		supports_flag_bulk_continuation = kernel_version_ge(2,6,32);
+		if (supports_flag_bulk_continuation == -1) {
+			usbi_err(ctx, "error checking for bulk continuation support");
+			return LIBUSB_ERROR_OTHER;
+		}
+	}
+
+	if (supports_flag_bulk_continuation)
+		usbi_dbg("bulk continuation flag supported");
+
+	if (-1 == supports_flag_zero_packet) {
+		/* zero length packet URB flag fixed since Linux 2.6.31 */
+		supports_flag_zero_packet = kernel_version_ge(2,6,31);
+		if (-1 == supports_flag_zero_packet) {
+			usbi_err(ctx, "error checking for zero length packet support");
+			return LIBUSB_ERROR_OTHER;
+		}
+	}
+
+	if (supports_flag_zero_packet)
+		usbi_dbg("zero length packet flag supported");
+
+	if (-1 == sysfs_has_descriptors) {
+		/* sysfs descriptors has all descriptors since Linux 2.6.26 */
+		sysfs_has_descriptors = kernel_version_ge(2,6,26);
+		if (-1 == sysfs_has_descriptors) {
+			usbi_err(ctx, "error checking for sysfs descriptors");
+			return LIBUSB_ERROR_OTHER;
+		}
+	}
+
+	if (-1 == sysfs_can_relate_devices) {
+		/* sysfs has busnum since Linux 2.6.22 */
+		sysfs_can_relate_devices = kernel_version_ge(2,6,22);
+		if (-1 == sysfs_can_relate_devices) {
+			usbi_err(ctx, "error checking for sysfs busnum");
+			return LIBUSB_ERROR_OTHER;
+		}
+	}
+
+	if (sysfs_can_relate_devices || sysfs_has_descriptors) {
+		r = stat(SYSFS_DEVICE_PATH, &statbuf);
+		if (r != 0 || !S_ISDIR(statbuf.st_mode)) {
+			usbi_warn(ctx, "sysfs not mounted");
+			sysfs_can_relate_devices = 0;
+			sysfs_has_descriptors = 0;
+		}
+	}
+
+	if (sysfs_can_relate_devices)
+		usbi_dbg("sysfs can relate devices");
+
+	if (sysfs_has_descriptors)
+		usbi_dbg("sysfs has complete descriptors");
+
+	usbi_mutex_static_lock(&linux_hotplug_startstop_lock);
+	r = LIBUSB_SUCCESS;
+	if (init_count == 0) {
+		/* start up hotplug event handler */
+		r = linux_start_event_monitor();
+	}
+	if (r == LIBUSB_SUCCESS) {
+		r = linux_scan_devices(ctx);
+		if (r == LIBUSB_SUCCESS)
+			init_count++;
+		else if (init_count == 0)
+			linux_stop_event_monitor();
+	} else
+		usbi_err(ctx, "error starting hotplug event monitor");
+	usbi_mutex_static_unlock(&linux_hotplug_startstop_lock);
+
+	return r;
+}
+
+static void op_exit(void)
+{
+	usbi_mutex_static_lock(&linux_hotplug_startstop_lock);
+	assert(init_count != 0);
+	if (!--init_count) {
+		/* tear down event handler */
+		(void)linux_stop_event_monitor();
+	}
+	usbi_mutex_static_unlock(&linux_hotplug_startstop_lock);
+}
+
+static int linux_start_event_monitor(void)
+{
+#if defined(USE_UDEV)
+	return linux_udev_start_event_monitor();
+#else
+	return linux_netlink_start_event_monitor();
+#endif
+}
+
+static int linux_stop_event_monitor(void)
+{
+#if defined(USE_UDEV)
+	return linux_udev_stop_event_monitor();
+#else
+	return linux_netlink_stop_event_monitor();
+#endif
+}
+
+static int linux_scan_devices(struct libusb_context *ctx)
+{
+	int ret;
+
+	usbi_mutex_static_lock(&linux_hotplug_lock);
+
+#if defined(USE_UDEV)
+	ret = linux_udev_scan_devices(ctx);
+#else
+	ret = linux_default_scan_devices(ctx);
+#endif
+
+	usbi_mutex_static_unlock(&linux_hotplug_lock);
+
+	return ret;
+}
+
+static void op_hotplug_poll(void)
+{
+#if defined(USE_UDEV)
+	linux_udev_hotplug_poll();
+#else
+	linux_netlink_hotplug_poll();
+#endif
+}
+
+static int _open_sysfs_attr(struct libusb_device *dev, const char *attr)
+{
+	struct linux_device_priv *priv = _device_priv(dev);
+	char filename[PATH_MAX];
+	int fd;
+
+	snprintf(filename, PATH_MAX, "%s/%s/%s",
+		SYSFS_DEVICE_PATH, priv->sysfs_dir, attr);
+	fd = open(filename, O_RDONLY);
+	if (fd < 0) {
+		usbi_err(DEVICE_CTX(dev),
+			"open %s failed ret=%d errno=%d", filename, fd, errno);
+		return LIBUSB_ERROR_IO;
+	}
+
+	return fd;
+}
+
+/* Note only suitable for attributes which always read >= 0, < 0 is error */
+static int __read_sysfs_attr(struct libusb_context *ctx,
+	const char *devname, const char *attr)
+{
+	char filename[PATH_MAX];
+	FILE *f;
+	int r, value;
+
+	snprintf(filename, PATH_MAX, "%s/%s/%s", SYSFS_DEVICE_PATH,
+		 devname, attr);
+	f = fopen(filename, "r");
+	if (f == NULL) {
+		if (errno == ENOENT) {
+			/* File doesn't exist. Assume the device has been
+			   disconnected (see trac ticket #70). */
+			return LIBUSB_ERROR_NO_DEVICE;
+		}
+		usbi_err(ctx, "open %s failed errno=%d", filename, errno);
+		return LIBUSB_ERROR_IO;
+	}
+
+	r = fscanf(f, "%d", &value);
+	fclose(f);
+	if (r != 1) {
+		usbi_err(ctx, "fscanf %s returned %d, errno=%d", attr, r, errno);
+		return LIBUSB_ERROR_NO_DEVICE; /* For unplug race (trac #70) */
+	}
+	if (value < 0) {
+		usbi_err(ctx, "%s contains a negative value", filename);
+		return LIBUSB_ERROR_IO;
+	}
+
+	return value;
+}
+
+static int op_get_device_descriptor(struct libusb_device *dev,
+	unsigned char *buffer, int *host_endian)
+{
+	struct linux_device_priv *priv = _device_priv(dev);
+
+	*host_endian = sysfs_has_descriptors ? 0 : 1;
+	memcpy(buffer, priv->descriptors, DEVICE_DESC_LENGTH);
+
+	return 0;
+}
+
+/* read the bConfigurationValue for a device */
+static int sysfs_get_active_config(struct libusb_device *dev, int *config)
+{
+	char *endptr;
+	char tmp[5] = {0, 0, 0, 0, 0};
+	long num;
+	int fd;
+	ssize_t r;
+
+	fd = _open_sysfs_attr(dev, "bConfigurationValue");
+	if (fd < 0)
+		return fd;
+
+	r = read(fd, tmp, sizeof(tmp));
+	close(fd);
+	if (r < 0) {
+		usbi_err(DEVICE_CTX(dev),
+			"read bConfigurationValue failed ret=%d errno=%d", r, errno);
+		return LIBUSB_ERROR_IO;
+	} else if (r == 0) {
+		usbi_dbg("device unconfigured");
+		*config = -1;
+		return 0;
+	}
+
+	if (tmp[sizeof(tmp) - 1] != 0) {
+		usbi_err(DEVICE_CTX(dev), "not null-terminated?");
+		return LIBUSB_ERROR_IO;
+	} else if (tmp[0] == 0) {
+		usbi_err(DEVICE_CTX(dev), "no configuration value?");
+		return LIBUSB_ERROR_IO;
+	}
+
+	num = strtol(tmp, &endptr, 10);
+	if (endptr == tmp) {
+		usbi_err(DEVICE_CTX(dev), "error converting '%s' to integer", tmp);
+		return LIBUSB_ERROR_IO;
+	}
+
+	*config = (int) num;
+	return 0;
+}
+
+int linux_get_device_address (struct libusb_context *ctx, int detached,
+	uint8_t *busnum, uint8_t *devaddr,const char *dev_node,
+	const char *sys_name)
+{
+	int sysfs_attr;
+
+	usbi_dbg("getting address for device: %s detached: %d", sys_name, detached);
+	/* can't use sysfs to read the bus and device number if the
+	 * device has been detached */
+	if (!sysfs_can_relate_devices || detached || NULL == sys_name) {
+		if (NULL == dev_node) {
+			return LIBUSB_ERROR_OTHER;
+		}
+
+		/* will this work with all supported kernel versions? */
+		if (!strncmp(dev_node, "/dev/bus/usb", 12)) {
+			sscanf (dev_node, "/dev/bus/usb/%hhu/%hhu", busnum, devaddr);
+		} else if (!strncmp(dev_node, "/proc/bus/usb", 13)) {
+			sscanf (dev_node, "/proc/bus/usb/%hhu/%hhu", busnum, devaddr);
+		}
+
+		return LIBUSB_SUCCESS;
+	}
+
+	usbi_dbg("scan %s", sys_name);
+
+	sysfs_attr = __read_sysfs_attr(ctx, sys_name, "busnum");
+	if (0 > sysfs_attr)
+		return sysfs_attr;
+	if (sysfs_attr > 255)
+		return LIBUSB_ERROR_INVALID_PARAM;
+	*busnum = (uint8_t) sysfs_attr;
+
+	sysfs_attr = __read_sysfs_attr(ctx, sys_name, "devnum");
+	if (0 > sysfs_attr)
+		return sysfs_attr;
+	if (sysfs_attr > 255)
+		return LIBUSB_ERROR_INVALID_PARAM;
+
+	*devaddr = (uint8_t) sysfs_attr;
+
+	usbi_dbg("bus=%d dev=%d", *busnum, *devaddr);
+
+	return LIBUSB_SUCCESS;
+}
+
+/* Return offset of the next descriptor with the given type */
+static int seek_to_next_descriptor(struct libusb_context *ctx,
+	uint8_t descriptor_type, unsigned char *buffer, int size)
+{
+	struct usb_descriptor_header header;
+	int i;
+
+	for (i = 0; size >= 0; i += header.bLength, size -= header.bLength) {
+		if (size == 0)
+			return LIBUSB_ERROR_NOT_FOUND;
+
+		if (size < 2) {
+			usbi_err(ctx, "short descriptor read %d/2", size);
+			return LIBUSB_ERROR_IO;
+		}
+		usbi_parse_descriptor(buffer + i, "bb", &header, 0);
+
+		if (i && header.bDescriptorType == descriptor_type)
+			return i;
+	}
+	usbi_err(ctx, "bLength overflow by %d bytes", -size);
+	return LIBUSB_ERROR_IO;
+}
+
+/* Return offset to next config */
+static int seek_to_next_config(struct libusb_context *ctx,
+	unsigned char *buffer, int size)
+{
+	struct libusb_config_descriptor config;
+
+	if (size == 0)
+		return LIBUSB_ERROR_NOT_FOUND;
+
+	if (size < LIBUSB_DT_CONFIG_SIZE) {
+		usbi_err(ctx, "short descriptor read %d/%d",
+			 size, LIBUSB_DT_CONFIG_SIZE);
+		return LIBUSB_ERROR_IO;
+	}
+
+	usbi_parse_descriptor(buffer, "bbwbbbbb", &config, 0);
+	if (config.bDescriptorType != LIBUSB_DT_CONFIG) {
+		usbi_err(ctx, "descriptor is not a config desc (type 0x%02x)",
+			 config.bDescriptorType);
+		return LIBUSB_ERROR_IO;
+	}
+
+	/*
+	 * In usbfs the config descriptors are config.wTotalLength bytes apart,
+	 * with any short reads from the device appearing as holes in the file.
+	 *
+	 * In sysfs wTotalLength is ignored, instead the kernel returns a
+	 * config descriptor with verified bLength fields, with descriptors
+	 * with an invalid bLength removed.
+	 */
+	if (sysfs_has_descriptors) {
+		int next = seek_to_next_descriptor(ctx, LIBUSB_DT_CONFIG,
+						   buffer, size);
+		if (next == LIBUSB_ERROR_NOT_FOUND)
+			next = size;
+		if (next < 0)
+			return next;
+
+		if (next != config.wTotalLength)
+			usbi_warn(ctx, "config length mismatch wTotalLength "
+				  "%d real %d", config.wTotalLength, next);
+		return next;
+	} else {
+		if (config.wTotalLength < LIBUSB_DT_CONFIG_SIZE) {
+			usbi_err(ctx, "invalid wTotalLength %d",
+				 config.wTotalLength);
+			return LIBUSB_ERROR_IO;
+		} else if (config.wTotalLength > size) {
+			usbi_warn(ctx, "short descriptor read %d/%d",
+				  size, config.wTotalLength);
+			return size;
+		} else
+			return config.wTotalLength;
+	}
+}
+
+static int op_get_config_descriptor_by_value(struct libusb_device *dev,
+	uint8_t value, unsigned char **buffer, int *host_endian)
+{
+	struct libusb_context *ctx = DEVICE_CTX(dev);
+	struct linux_device_priv *priv = _device_priv(dev);
+	unsigned char *descriptors = priv->descriptors;
+	int size = priv->descriptors_len;
+	struct libusb_config_descriptor *config;
+
+	*buffer = NULL;
+	/* Unlike the device desc. config descs. are always in raw format */
+	*host_endian = 0;
+
+	/* Skip device header */
+	descriptors += DEVICE_DESC_LENGTH;
+	size -= DEVICE_DESC_LENGTH;
+
+	/* Seek till the config is found, or till "EOF" */
+	while (1) {
+		int next = seek_to_next_config(ctx, descriptors, size);
+		if (next < 0)
+			return next;
+		config = (struct libusb_config_descriptor *)descriptors;
+		if (config->bConfigurationValue == value) {
+			*buffer = descriptors;
+			return next;
+		}
+		size -= next;
+		descriptors += next;
+	}
+}
+
+static int op_get_active_config_descriptor(struct libusb_device *dev,
+	unsigned char *buffer, size_t len, int *host_endian)
+{
+	int r, config;
+	unsigned char *config_desc;
+
+	if (sysfs_can_relate_devices) {
+		r = sysfs_get_active_config(dev, &config);
+		if (r < 0)
+			return r;
+	} else {
+		/* Use cached bConfigurationValue */
+		struct linux_device_priv *priv = _device_priv(dev);
+		config = priv->active_config;
+	}
+	if (config == -1)
+		return LIBUSB_ERROR_NOT_FOUND;
+
+	r = op_get_config_descriptor_by_value(dev, config, &config_desc,
+					      host_endian);
+	if (r < 0)
+		return r;
+
+	len = MIN(len, r);
+	memcpy(buffer, config_desc, len);
+	return len;
+}
+
+static int op_get_config_descriptor(struct libusb_device *dev,
+	uint8_t config_index, unsigned char *buffer, size_t len, int *host_endian)
+{
+	struct linux_device_priv *priv = _device_priv(dev);
+	unsigned char *descriptors = priv->descriptors;
+	int i, r, size = priv->descriptors_len;
+
+	/* Unlike the device desc. config descs. are always in raw format */
+	*host_endian = 0;
+
+	/* Skip device header */
+	descriptors += DEVICE_DESC_LENGTH;
+	size -= DEVICE_DESC_LENGTH;
+
+	/* Seek till the config is found, or till "EOF" */
+	for (i = 0; ; i++) {
+		r = seek_to_next_config(DEVICE_CTX(dev), descriptors, size);
+		if (r < 0)
+			return r;
+		if (i == config_index)
+			break;
+		size -= r;
+		descriptors += r;
+	}
+
+	len = MIN(len, r);
+	memcpy(buffer, descriptors, len);
+	return len;
+}
+
+/* send a control message to retrieve active configuration */
+static int usbfs_get_active_config(struct libusb_device *dev, int fd)
+{
+	struct linux_device_priv *priv = _device_priv(dev);
+	unsigned char active_config = 0;
+	int r;
+
+	struct usbfs_ctrltransfer ctrl = {
+		.bmRequestType = LIBUSB_ENDPOINT_IN,
+		.bRequest = LIBUSB_REQUEST_GET_CONFIGURATION,
+		.wValue = 0,
+		.wIndex = 0,
+		.wLength = 1,
+		.timeout = 1000,
+		.data = &active_config
+	};
+
+	r = ioctl(fd, IOCTL_USBFS_CONTROL, &ctrl);
+	if (r < 0) {
+		if (errno == ENODEV)
+			return LIBUSB_ERROR_NO_DEVICE;
+
+		/* we hit this error path frequently with buggy devices :( */
+		usbi_warn(DEVICE_CTX(dev),
+			"get_configuration failed ret=%d errno=%d", r, errno);
+		priv->active_config = -1;
+	} else {
+		if (active_config > 0) {
+			priv->active_config = active_config;
+		} else {
+			/* some buggy devices have a configuration 0, but we're
+			 * reaching into the corner of a corner case here, so let's
+			 * not support buggy devices in these circumstances.
+			 * stick to the specs: a configuration value of 0 means
+			 * unconfigured. */
+			usbi_warn(DEVICE_CTX(dev),
+				"active cfg 0? assuming unconfigured device");
+			priv->active_config = -1;
+		}
+	}
+
+	return LIBUSB_SUCCESS;
+}
+
+static int initialize_device(struct libusb_device *dev, uint8_t busnum,
+	uint8_t devaddr, const char *sysfs_dir)
+{
+	struct linux_device_priv *priv = _device_priv(dev);
+	struct libusb_context *ctx = DEVICE_CTX(dev);
+	int descriptors_size = 512; /* Begin with a 1024 byte alloc */
+	int fd, speed;
+	ssize_t r;
+
+	dev->bus_number = busnum;
+	dev->device_address = devaddr;
+
+	if (sysfs_dir) {
+		priv->sysfs_dir = strdup(sysfs_dir);
+		if (!priv->sysfs_dir)
+			return LIBUSB_ERROR_NO_MEM;
+
+		/* Note speed can contain 1.5, in this case __read_sysfs_attr
+		   will stop parsing at the '.' and return 1 */
+		speed = __read_sysfs_attr(DEVICE_CTX(dev), sysfs_dir, "speed");
+		if (speed >= 0) {
+			switch (speed) {
+			case     1: dev->speed = LIBUSB_SPEED_LOW; break;
+			case    12: dev->speed = LIBUSB_SPEED_FULL; break;
+			case   480: dev->speed = LIBUSB_SPEED_HIGH; break;
+			case  5000: dev->speed = LIBUSB_SPEED_SUPER; break;
+			default:
+				usbi_warn(DEVICE_CTX(dev), "Unknown device speed: %d Mbps", speed);
+			}
+		}
+	}
+
+	/* cache descriptors in memory */
+	if (sysfs_has_descriptors)
+		fd = _open_sysfs_attr(dev, "descriptors");
+	else
+		fd = _get_usbfs_fd(dev, O_RDONLY, 0);
+	if (fd < 0)
+		return fd;
+
+	do {
+		descriptors_size *= 2;
+		priv->descriptors = usbi_reallocf(priv->descriptors,
+						  descriptors_size);
+		if (!priv->descriptors) {
+			close(fd);
+			return LIBUSB_ERROR_NO_MEM;
+		}
+		/* usbfs has holes in the file */
+		if (!sysfs_has_descriptors) {
+			memset(priv->descriptors + priv->descriptors_len,
+			       0, descriptors_size - priv->descriptors_len);
+		}
+		r = read(fd, priv->descriptors + priv->descriptors_len,
+			 descriptors_size - priv->descriptors_len);
+		if (r < 0) {
+			usbi_err(ctx, "read descriptor failed ret=%d errno=%d",
+				 fd, errno);
+			close(fd);
+			return LIBUSB_ERROR_IO;
+		}
+		priv->descriptors_len += r;
+	} while (priv->descriptors_len == descriptors_size);
+
+	close(fd);
+
+	if (priv->descriptors_len < DEVICE_DESC_LENGTH) {
+		usbi_err(ctx, "short descriptor read (%d)",
+			 priv->descriptors_len);
+		return LIBUSB_ERROR_IO;
+	}
+
+	if (sysfs_can_relate_devices)
+		return LIBUSB_SUCCESS;
+
+	/* cache active config */
+	fd = _get_usbfs_fd(dev, O_RDWR, 1);
+	if (fd < 0) {
+		/* cannot send a control message to determine the active
+		 * config. just assume the first one is active. */
+		usbi_warn(ctx, "Missing rw usbfs access; cannot determine "
+			       "active configuration descriptor");
+		if (priv->descriptors_len >=
+				(DEVICE_DESC_LENGTH + LIBUSB_DT_CONFIG_SIZE)) {
+			struct libusb_config_descriptor config;
+			usbi_parse_descriptor(
+				priv->descriptors + DEVICE_DESC_LENGTH,
+				"bbwbbbbb", &config, 0);
+			priv->active_config = config.bConfigurationValue;
+		} else
+			priv->active_config = -1; /* No config dt */
+
+		return LIBUSB_SUCCESS;
+	}
+
+	r = usbfs_get_active_config(dev, fd);
+	close(fd);
+
+	return r;
+}
+
+static int linux_get_parent_info(struct libusb_device *dev, const char *sysfs_dir)
+{
+	struct libusb_context *ctx = DEVICE_CTX(dev);
+	struct libusb_device *it;
+	char *parent_sysfs_dir, *tmp;
+	int ret, add_parent = 1;
+
+	/* XXX -- can we figure out the topology when using usbfs? */
+	if (NULL == sysfs_dir || 0 == strncmp(sysfs_dir, "usb", 3)) {
+		/* either using usbfs or finding the parent of a root hub */
+		return LIBUSB_SUCCESS;
+	}
+
+	parent_sysfs_dir = strdup(sysfs_dir);
+	if (NULL == parent_sysfs_dir) {
+		return LIBUSB_ERROR_NO_MEM;
+	}
+	if (NULL != (tmp = strrchr(parent_sysfs_dir, '.')) ||
+	    NULL != (tmp = strrchr(parent_sysfs_dir, '-'))) {
+	        dev->port_number = atoi(tmp + 1);
+		*tmp = '\0';
+	} else {
+		usbi_warn(ctx, "Can not parse sysfs_dir: %s, no parent info",
+			  parent_sysfs_dir);
+		free (parent_sysfs_dir);
+		return LIBUSB_SUCCESS;
+	}
+
+	/* is the parent a root hub? */
+	if (NULL == strchr(parent_sysfs_dir, '-')) {
+		tmp = parent_sysfs_dir;
+		ret = asprintf (&parent_sysfs_dir, "usb%s", tmp);
+		free (tmp);
+		if (0 > ret) {
+			return LIBUSB_ERROR_NO_MEM;
+		}
+	}
+
+retry:
+	/* find the parent in the context */
+	usbi_mutex_lock(&ctx->usb_devs_lock);
+	list_for_each_entry(it, &ctx->usb_devs, list, struct libusb_device) {
+		struct linux_device_priv *priv = _device_priv(it);
+		if (priv->sysfs_dir) {
+			if (0 == strcmp (priv->sysfs_dir, parent_sysfs_dir)) {
+				dev->parent_dev = libusb_ref_device(it);
+				break;
+			}
+		}
+	}
+	usbi_mutex_unlock(&ctx->usb_devs_lock);
+
+	if (!dev->parent_dev && add_parent) {
+		usbi_dbg("parent_dev %s not enumerated yet, enumerating now",
+			 parent_sysfs_dir);
+		sysfs_scan_device(ctx, parent_sysfs_dir);
+		add_parent = 0;
+		goto retry;
+	}
+
+	usbi_dbg("Dev %p (%s) has parent %p (%s) port %d", dev, sysfs_dir,
+		 dev->parent_dev, parent_sysfs_dir, dev->port_number);
+
+	free (parent_sysfs_dir);
+
+	return LIBUSB_SUCCESS;
+}
+
+int linux_enumerate_device(struct libusb_context *ctx,
+	uint8_t busnum, uint8_t devaddr, const char *sysfs_dir)
+{
+	unsigned long session_id;
+	struct libusb_device *dev;
+	int r = 0;
+
+	/* FIXME: session ID is not guaranteed unique as addresses can wrap and
+	 * will be reused. instead we should add a simple sysfs attribute with
+	 * a session ID. */
+	session_id = busnum << 8 | devaddr;
+	usbi_dbg("busnum %d devaddr %d session_id %ld", busnum, devaddr,
+		session_id);
+
+	dev = usbi_get_device_by_session_id(ctx, session_id);
+	if (dev) {
+		/* device already exists in the context */
+		usbi_dbg("session_id %ld already exists", session_id);
+		libusb_unref_device(dev);
+		return LIBUSB_SUCCESS;
+	}
+
+	usbi_dbg("allocating new device for %d/%d (session %ld)",
+		 busnum, devaddr, session_id);
+	dev = usbi_alloc_device(ctx, session_id);
+	if (!dev)
+		return LIBUSB_ERROR_NO_MEM;
+
+	r = initialize_device(dev, busnum, devaddr, sysfs_dir);
+	if (r < 0)
+		goto out;
+	r = usbi_sanitize_device(dev);
+	if (r < 0)
+		goto out;
+
+	r = linux_get_parent_info(dev, sysfs_dir);
+	if (r < 0)
+		goto out;
+out:
+	if (r < 0)
+		libusb_unref_device(dev);
+	else
+		usbi_connect_device(dev);
+
+	return r;
+}
+
+void linux_hotplug_enumerate(uint8_t busnum, uint8_t devaddr, const char *sys_name)
+{
+	struct libusb_context *ctx;
+
+	usbi_mutex_static_lock(&active_contexts_lock);
+	list_for_each_entry(ctx, &active_contexts_list, list, struct libusb_context) {
+		linux_enumerate_device(ctx, busnum, devaddr, sys_name);
+	}
+	usbi_mutex_static_unlock(&active_contexts_lock);
+}
+
+void linux_device_disconnected(uint8_t busnum, uint8_t devaddr)
+{
+	struct libusb_context *ctx;
+	struct libusb_device *dev;
+	unsigned long session_id = busnum << 8 | devaddr;
+
+	usbi_mutex_static_lock(&active_contexts_lock);
+	list_for_each_entry(ctx, &active_contexts_list, list, struct libusb_context) {
+		dev = usbi_get_device_by_session_id (ctx, session_id);
+		if (NULL != dev) {
+			usbi_disconnect_device (dev);
+			libusb_unref_device(dev);
+		} else {
+			usbi_dbg("device not found for session %x", session_id);
+		}
+	}
+	usbi_mutex_static_unlock(&active_contexts_lock);
+}
+
+#if !defined(USE_UDEV)
+/* open a bus directory and adds all discovered devices to the context */
+static int usbfs_scan_busdir(struct libusb_context *ctx, uint8_t busnum)
+{
+	DIR *dir;
+	char dirpath[PATH_MAX];
+	struct dirent *entry;
+	int r = LIBUSB_ERROR_IO;
+
+	snprintf(dirpath, PATH_MAX, "%s/%03d", usbfs_path, busnum);
+	usbi_dbg("%s", dirpath);
+	dir = opendir(dirpath);
+	if (!dir) {
+		usbi_err(ctx, "opendir '%s' failed, errno=%d", dirpath, errno);
+		/* FIXME: should handle valid race conditions like hub unplugged
+		 * during directory iteration - this is not an error */
+		return r;
+	}
+
+	while ((entry = readdir(dir))) {
+		int devaddr;
+
+		if (entry->d_name[0] == '.')
+			continue;
+
+		devaddr = atoi(entry->d_name);
+		if (devaddr == 0) {
+			usbi_dbg("unknown dir entry %s", entry->d_name);
+			continue;
+		}
+
+		if (linux_enumerate_device(ctx, busnum, (uint8_t) devaddr, NULL)) {
+			usbi_dbg("failed to enumerate dir entry %s", entry->d_name);
+			continue;
+		}
+
+		r = 0;
+	}
+
+	closedir(dir);
+	return r;
+}
+
+static int usbfs_get_device_list(struct libusb_context *ctx)
+{
+	struct dirent *entry;
+	DIR *buses = opendir(usbfs_path);
+	int r = 0;
+
+	if (!buses) {
+		usbi_err(ctx, "opendir buses failed errno=%d", errno);
+		return LIBUSB_ERROR_IO;
+	}
+
+	while ((entry = readdir(buses))) {
+		int busnum;
+
+		if (entry->d_name[0] == '.')
+			continue;
+
+		if (usbdev_names) {
+			int devaddr;
+			if (!_is_usbdev_entry(entry, &busnum, &devaddr))
+				continue;
+
+			r = linux_enumerate_device(ctx, busnum, (uint8_t) devaddr, NULL);
+			if (r < 0) {
+				usbi_dbg("failed to enumerate dir entry %s", entry->d_name);
+				continue;
+			}
+		} else {
+			busnum = atoi(entry->d_name);
+			if (busnum == 0) {
+				usbi_dbg("unknown dir entry %s", entry->d_name);
+				continue;
+			}
+
+			r = usbfs_scan_busdir(ctx, busnum);
+			if (r < 0)
+				break;
+		}
+	}
+
+	closedir(buses);
+	return r;
+
+}
+#endif
+
+static int sysfs_scan_device(struct libusb_context *ctx, const char *devname)
+{
+	uint8_t busnum, devaddr;
+	int ret;
+
+	ret = linux_get_device_address (ctx, 0, &busnum, &devaddr, NULL, devname);
+	if (LIBUSB_SUCCESS != ret) {
+		return ret;
+	}
+
+	return linux_enumerate_device(ctx, busnum & 0xff, devaddr & 0xff,
+		devname);
+}
+
+#if !defined(USE_UDEV)
+static int sysfs_get_device_list(struct libusb_context *ctx)
+{
+	DIR *devices = opendir(SYSFS_DEVICE_PATH);
+	struct dirent *entry;
+	int r = LIBUSB_ERROR_IO;
+
+	if (!devices) {
+		usbi_err(ctx, "opendir devices failed errno=%d", errno);
+		return r;
+	}
+
+	while ((entry = readdir(devices))) {
+		if ((!isdigit(entry->d_name[0]) && strncmp(entry->d_name, "usb", 3))
+				|| strchr(entry->d_name, ':'))
+			continue;
+
+		if (sysfs_scan_device(ctx, entry->d_name)) {
+			usbi_dbg("failed to enumerate dir entry %s", entry->d_name);
+			continue;
+		}
+
+		r = 0;
+	}
+
+	closedir(devices);
+	return r;
+}
+
+static int linux_default_scan_devices (struct libusb_context *ctx)
+{
+	/* we can retrieve device list and descriptors from sysfs or usbfs.
+	 * sysfs is preferable, because if we use usbfs we end up resuming
+	 * any autosuspended USB devices. however, sysfs is not available
+	 * everywhere, so we need a usbfs fallback too.
+	 *
+	 * as described in the "sysfs vs usbfs" comment at the top of this
+	 * file, sometimes we have sysfs but not enough information to
+	 * relate sysfs devices to usbfs nodes.  op_init() determines the
+	 * adequacy of sysfs and sets sysfs_can_relate_devices.
+	 */
+	if (sysfs_can_relate_devices != 0)
+		return sysfs_get_device_list(ctx);
+	else
+		return usbfs_get_device_list(ctx);
+}
+#endif
+
+static int op_open(struct libusb_device_handle *handle)
+{
+	struct linux_device_handle_priv *hpriv = _device_handle_priv(handle);
+	int r;
+
+	hpriv->fd = _get_usbfs_fd(handle->dev, O_RDWR, 0);
+	if (hpriv->fd < 0) {
+		if (hpriv->fd == LIBUSB_ERROR_NO_DEVICE) {
+			/* device will still be marked as attached if hotplug monitor thread
+			 * hasn't processed remove event yet */
+			usbi_mutex_static_lock(&linux_hotplug_lock);
+			if (handle->dev->attached) {
+				usbi_dbg("open failed with no device, but device still attached");
+				linux_device_disconnected(handle->dev->bus_number,
+						handle->dev->device_address);
+			}
+			usbi_mutex_static_unlock(&linux_hotplug_lock);
+		}
+		return hpriv->fd;
+	}
+
+	r = ioctl(hpriv->fd, IOCTL_USBFS_GET_CAPABILITIES, &hpriv->caps);
+	if (r < 0) {
+		if (errno == ENOTTY)
+			usbi_dbg("getcap not available");
+		else
+			usbi_err(HANDLE_CTX(handle), "getcap failed (%d)", errno);
+		hpriv->caps = 0;
+		if (supports_flag_zero_packet)
+			hpriv->caps |= USBFS_CAP_ZERO_PACKET;
+		if (supports_flag_bulk_continuation)
+			hpriv->caps |= USBFS_CAP_BULK_CONTINUATION;
+	}
+
+	r = usbi_add_pollfd(HANDLE_CTX(handle), hpriv->fd, POLLOUT);
+	if (r < 0)
+		close(hpriv->fd);
+
+	return r;
+}
+
+static void op_close(struct libusb_device_handle *dev_handle)
+{
+	struct linux_device_handle_priv *hpriv = _device_handle_priv(dev_handle);
+	/* fd may have already been removed by POLLERR condition in op_handle_events() */
+	if (!hpriv->fd_removed)
+		usbi_remove_pollfd(HANDLE_CTX(dev_handle), hpriv->fd);
+	close(hpriv->fd);
+}
+
+static int op_get_configuration(struct libusb_device_handle *handle,
+	int *config)
+{
+	int r;
+
+	if (sysfs_can_relate_devices) {
+		r = sysfs_get_active_config(handle->dev, config);
+	} else {
+		r = usbfs_get_active_config(handle->dev,
+					    _device_handle_priv(handle)->fd);
+		if (r == LIBUSB_SUCCESS)
+			*config = _device_priv(handle->dev)->active_config;
+	}
+	if (r < 0)
+		return r;
+
+	if (*config == -1) {
+		usbi_err(HANDLE_CTX(handle), "device unconfigured");
+		*config = 0;
+	}
+
+	return 0;
+}
+
+static int op_set_configuration(struct libusb_device_handle *handle, int config)
+{
+	struct linux_device_priv *priv = _device_priv(handle->dev);
+	int fd = _device_handle_priv(handle)->fd;
+	int r = ioctl(fd, IOCTL_USBFS_SETCONFIG, &config);
+	if (r) {
+		if (errno == EINVAL)
+			return LIBUSB_ERROR_NOT_FOUND;
+		else if (errno == EBUSY)
+			return LIBUSB_ERROR_BUSY;
+		else if (errno == ENODEV)
+			return LIBUSB_ERROR_NO_DEVICE;
+
+		usbi_err(HANDLE_CTX(handle), "failed, error %d errno %d", r, errno);
+		return LIBUSB_ERROR_OTHER;
+	}
+
+	/* update our cached active config descriptor */
+	priv->active_config = config;
+
+	return LIBUSB_SUCCESS;
+}
+
+static int claim_interface(struct libusb_device_handle *handle, int iface)
+{
+	int fd = _device_handle_priv(handle)->fd;
+	int r = ioctl(fd, IOCTL_USBFS_CLAIMINTF, &iface);
+	if (r) {
+		if (errno == ENOENT)
+			return LIBUSB_ERROR_NOT_FOUND;
+		else if (errno == EBUSY)
+			return LIBUSB_ERROR_BUSY;
+		else if (errno == ENODEV)
+			return LIBUSB_ERROR_NO_DEVICE;
+
+		usbi_err(HANDLE_CTX(handle),
+			"claim interface failed, error %d errno %d", r, errno);
+		return LIBUSB_ERROR_OTHER;
+	}
+	return 0;
+}
+
+static int release_interface(struct libusb_device_handle *handle, int iface)
+{
+	int fd = _device_handle_priv(handle)->fd;
+	int r = ioctl(fd, IOCTL_USBFS_RELEASEINTF, &iface);
+	if (r) {
+		if (errno == ENODEV)
+			return LIBUSB_ERROR_NO_DEVICE;
+
+		usbi_err(HANDLE_CTX(handle),
+			"release interface failed, error %d errno %d", r, errno);
+		return LIBUSB_ERROR_OTHER;
+	}
+	return 0;
+}
+
+static int op_set_interface(struct libusb_device_handle *handle, int iface,
+	int altsetting)
+{
+	int fd = _device_handle_priv(handle)->fd;
+	struct usbfs_setinterface setintf;
+	int r;
+
+	setintf.interface = iface;
+	setintf.altsetting = altsetting;
+	r = ioctl(fd, IOCTL_USBFS_SETINTF, &setintf);
+	if (r) {
+		if (errno == EINVAL)
+			return LIBUSB_ERROR_NOT_FOUND;
+		else if (errno == ENODEV)
+			return LIBUSB_ERROR_NO_DEVICE;
+
+		usbi_err(HANDLE_CTX(handle),
+			"setintf failed error %d errno %d", r, errno);
+		return LIBUSB_ERROR_OTHER;
+	}
+
+	return 0;
+}
+
+static int op_clear_halt(struct libusb_device_handle *handle,
+	unsigned char endpoint)
+{
+	int fd = _device_handle_priv(handle)->fd;
+	unsigned int _endpoint = endpoint;
+	int r = ioctl(fd, IOCTL_USBFS_CLEAR_HALT, &_endpoint);
+	if (r) {
+		if (errno == ENOENT)
+			return LIBUSB_ERROR_NOT_FOUND;
+		else if (errno == ENODEV)
+			return LIBUSB_ERROR_NO_DEVICE;
+
+		usbi_err(HANDLE_CTX(handle),
+			"clear_halt failed error %d errno %d", r, errno);
+		return LIBUSB_ERROR_OTHER;
+	}
+
+	return 0;
+}
+
+static int op_reset_device(struct libusb_device_handle *handle)
+{
+	int fd = _device_handle_priv(handle)->fd;
+	int i, r, ret = 0;
+
+	/* Doing a device reset will cause the usbfs driver to get unbound
+	   from any interfaces it is bound to. By voluntarily unbinding
+	   the usbfs driver ourself, we stop the kernel from rebinding
+	   the interface after reset (which would end up with the interface
+	   getting bound to the in kernel driver if any). */
+	for (i = 0; i < USB_MAXINTERFACES; i++) {
+		if (handle->claimed_interfaces & (1L << i)) {
+			release_interface(handle, i);
+		}
+	}
+
+	usbi_mutex_lock(&handle->lock);
+	r = ioctl(fd, IOCTL_USBFS_RESET, NULL);
+	if (r) {
+		if (errno == ENODEV) {
+			ret = LIBUSB_ERROR_NOT_FOUND;
+			goto out;
+		}
+
+		usbi_err(HANDLE_CTX(handle),
+			"reset failed error %d errno %d", r, errno);
+		ret = LIBUSB_ERROR_OTHER;
+		goto out;
+	}
+
+	/* And re-claim any interfaces which were claimed before the reset */
+	for (i = 0; i < USB_MAXINTERFACES; i++) {
+		if (handle->claimed_interfaces & (1L << i)) {
+			/*
+			 * A driver may have completed modprobing during
+			 * IOCTL_USBFS_RESET, and bound itself as soon as
+			 * IOCTL_USBFS_RESET released the device lock
+			 */
+			r = detach_kernel_driver_and_claim(handle, i);
+			if (r) {
+				usbi_warn(HANDLE_CTX(handle),
+					"failed to re-claim interface %d after reset: %s",
+					i, libusb_error_name(r));
+				handle->claimed_interfaces &= ~(1L << i);
+				ret = LIBUSB_ERROR_NOT_FOUND;
+			}
+		}
+	}
+out:
+	usbi_mutex_unlock(&handle->lock);
+	return ret;
+}
+
+static int do_streams_ioctl(struct libusb_device_handle *handle, long req,
+	uint32_t num_streams, unsigned char *endpoints, int num_endpoints)
+{
+	int r, fd = _device_handle_priv(handle)->fd;
+	struct usbfs_streams *streams;
+
+	if (num_endpoints > 30) /* Max 15 in + 15 out eps */
+		return LIBUSB_ERROR_INVALID_PARAM;
+
+	streams = malloc(sizeof(struct usbfs_streams) + num_endpoints);
+	if (!streams)
+		return LIBUSB_ERROR_NO_MEM;
+
+	streams->num_streams = num_streams;
+	streams->num_eps = num_endpoints;
+	memcpy(streams->eps, endpoints, num_endpoints);
+
+	r = ioctl(fd, req, streams);
+
+	free(streams);
+
+	if (r < 0) {
+		if (errno == ENOTTY)
+			return LIBUSB_ERROR_NOT_SUPPORTED;
+		else if (errno == EINVAL)
+			return LIBUSB_ERROR_INVALID_PARAM;
+		else if (errno == ENODEV)
+			return LIBUSB_ERROR_NO_DEVICE;
+
+		usbi_err(HANDLE_CTX(handle),
+			"streams-ioctl failed error %d errno %d", r, errno);
+		return LIBUSB_ERROR_OTHER;
+	}
+	return r;
+}
+
+static int op_alloc_streams(struct libusb_device_handle *handle,
+	uint32_t num_streams, unsigned char *endpoints, int num_endpoints)
+{
+	return do_streams_ioctl(handle, IOCTL_USBFS_ALLOC_STREAMS,
+				num_streams, endpoints, num_endpoints);
+}
+
+static int op_free_streams(struct libusb_device_handle *handle,
+		unsigned char *endpoints, int num_endpoints)
+{
+	return do_streams_ioctl(handle, IOCTL_USBFS_FREE_STREAMS, 0,
+				endpoints, num_endpoints);
+}
+
+static unsigned char *op_dev_mem_alloc(struct libusb_device_handle *handle,
+	size_t len)
+{
+	struct linux_device_handle_priv *hpriv = _device_handle_priv(handle);
+	unsigned char *buffer = (unsigned char *)mmap(NULL, len,
+		PROT_READ | PROT_WRITE, MAP_SHARED, hpriv->fd, 0);
+	if (buffer == MAP_FAILED) {
+		usbi_err(HANDLE_CTX(handle), "alloc dev mem failed errno %d",
+			errno);
+		return NULL;
+	}
+	return buffer;
+}
+
+static int op_dev_mem_free(struct libusb_device_handle *handle,
+	unsigned char *buffer, size_t len)
+{
+	if (munmap(buffer, len) != 0) {
+		usbi_err(HANDLE_CTX(handle), "free dev mem failed errno %d",
+			errno);
+		return LIBUSB_ERROR_OTHER;
+	} else {
+		return LIBUSB_SUCCESS;
+	}
+}
+
+static int op_kernel_driver_active(struct libusb_device_handle *handle,
+	int interface)
+{
+	int fd = _device_handle_priv(handle)->fd;
+	struct usbfs_getdriver getdrv;
+	int r;
+
+	getdrv.interface = interface;
+	r = ioctl(fd, IOCTL_USBFS_GETDRIVER, &getdrv);
+	if (r) {
+		if (errno == ENODATA)
+			return 0;
+		else if (errno == ENODEV)
+			return LIBUSB_ERROR_NO_DEVICE;
+
+		usbi_err(HANDLE_CTX(handle),
+			"get driver failed error %d errno %d", r, errno);
+		return LIBUSB_ERROR_OTHER;
+	}
+
+	return (strcmp(getdrv.driver, "usbfs") == 0) ? 0 : 1;
+}
+
+static int op_detach_kernel_driver(struct libusb_device_handle *handle,
+	int interface)
+{
+	int fd = _device_handle_priv(handle)->fd;
+	struct usbfs_ioctl command;
+	struct usbfs_getdriver getdrv;
+	int r;
+
+	command.ifno = interface;
+	command.ioctl_code = IOCTL_USBFS_DISCONNECT;
+	command.data = NULL;
+
+	getdrv.interface = interface;
+	r = ioctl(fd, IOCTL_USBFS_GETDRIVER, &getdrv);
+	if (r == 0 && strcmp(getdrv.driver, "usbfs") == 0)
+		return LIBUSB_ERROR_NOT_FOUND;
+
+	r = ioctl(fd, IOCTL_USBFS_IOCTL, &command);
+	if (r) {
+		if (errno == ENODATA)
+			return LIBUSB_ERROR_NOT_FOUND;
+		else if (errno == EINVAL)
+			return LIBUSB_ERROR_INVALID_PARAM;
+		else if (errno == ENODEV)
+			return LIBUSB_ERROR_NO_DEVICE;
+
+		usbi_err(HANDLE_CTX(handle),
+			"detach failed error %d errno %d", r, errno);
+		return LIBUSB_ERROR_OTHER;
+	}
+
+	return 0;
+}
+
+static int op_attach_kernel_driver(struct libusb_device_handle *handle,
+	int interface)
+{
+	int fd = _device_handle_priv(handle)->fd;
+	struct usbfs_ioctl command;
+	int r;
+
+	command.ifno = interface;
+	command.ioctl_code = IOCTL_USBFS_CONNECT;
+	command.data = NULL;
+
+	r = ioctl(fd, IOCTL_USBFS_IOCTL, &command);
+	if (r < 0) {
+		if (errno == ENODATA)
+			return LIBUSB_ERROR_NOT_FOUND;
+		else if (errno == EINVAL)
+			return LIBUSB_ERROR_INVALID_PARAM;
+		else if (errno == ENODEV)
+			return LIBUSB_ERROR_NO_DEVICE;
+		else if (errno == EBUSY)
+			return LIBUSB_ERROR_BUSY;
+
+		usbi_err(HANDLE_CTX(handle),
+			"attach failed error %d errno %d", r, errno);
+		return LIBUSB_ERROR_OTHER;
+	} else if (r == 0) {
+		return LIBUSB_ERROR_NOT_FOUND;
+	}
+
+	return 0;
+}
+
+static int detach_kernel_driver_and_claim(struct libusb_device_handle *handle,
+	int interface)
+{
+	struct usbfs_disconnect_claim dc;
+	int r, fd = _device_handle_priv(handle)->fd;
+
+	dc.interface = interface;
+	strcpy(dc.driver, "usbfs");
+	dc.flags = USBFS_DISCONNECT_CLAIM_EXCEPT_DRIVER;
+	r = ioctl(fd, IOCTL_USBFS_DISCONNECT_CLAIM, &dc);
+	if (r == 0 || (r != 0 && errno != ENOTTY)) {
+		if (r == 0)
+			return 0;
+
+		switch (errno) {
+		case EBUSY:
+			return LIBUSB_ERROR_BUSY;
+		case EINVAL:
+			return LIBUSB_ERROR_INVALID_PARAM;
+		case ENODEV:
+			return LIBUSB_ERROR_NO_DEVICE;
+		}
+		usbi_err(HANDLE_CTX(handle),
+			"disconnect-and-claim failed errno %d", errno);
+		return LIBUSB_ERROR_OTHER;
+	}
+
+	/* Fallback code for kernels which don't support the
+	   disconnect-and-claim ioctl */
+	r = op_detach_kernel_driver(handle, interface);
+	if (r != 0 && r != LIBUSB_ERROR_NOT_FOUND)
+		return r;
+
+	return claim_interface(handle, interface);
+}
+
+static int op_claim_interface(struct libusb_device_handle *handle, int iface)
+{
+	if (handle->auto_detach_kernel_driver)
+		return detach_kernel_driver_and_claim(handle, iface);
+	else
+		return claim_interface(handle, iface);
+}
+
+static int op_release_interface(struct libusb_device_handle *handle, int iface)
+{
+	int r;
+
+	r = release_interface(handle, iface);
+	if (r)
+		return r;
+
+	if (handle->auto_detach_kernel_driver)
+		op_attach_kernel_driver(handle, iface);
+
+	return 0;
+}
+
+static void op_destroy_device(struct libusb_device *dev)
+{
+	struct linux_device_priv *priv = _device_priv(dev);
+	if (priv->descriptors)
+		free(priv->descriptors);
+	if (priv->sysfs_dir)
+		free(priv->sysfs_dir);
+}
+
+/* URBs are discarded in reverse order of submission to avoid races. */
+static int discard_urbs(struct usbi_transfer *itransfer, int first, int last_plus_one)
+{
+	struct libusb_transfer *transfer =
+		USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	struct linux_transfer_priv *tpriv =
+		usbi_transfer_get_os_priv(itransfer);
+	struct linux_device_handle_priv *dpriv =
+		_device_handle_priv(transfer->dev_handle);
+	int i, ret = 0;
+	struct usbfs_urb *urb;
+
+	for (i = last_plus_one - 1; i >= first; i--) {
+		if (LIBUSB_TRANSFER_TYPE_ISOCHRONOUS == transfer->type)
+			urb = tpriv->iso_urbs[i];
+		else
+			urb = &tpriv->urbs[i];
+
+		if (0 == ioctl(dpriv->fd, IOCTL_USBFS_DISCARDURB, urb))
+			continue;
+
+		if (EINVAL == errno) {
+			usbi_dbg("URB not found --> assuming ready to be reaped");
+			if (i == (last_plus_one - 1))
+				ret = LIBUSB_ERROR_NOT_FOUND;
+		} else if (ENODEV == errno) {
+			usbi_dbg("Device not found for URB --> assuming ready to be reaped");
+			ret = LIBUSB_ERROR_NO_DEVICE;
+		} else {
+			usbi_warn(TRANSFER_CTX(transfer),
+				"unrecognised discard errno %d", errno);
+			ret = LIBUSB_ERROR_OTHER;
+		}
+	}
+	return ret;
+}
+
+static void free_iso_urbs(struct linux_transfer_priv *tpriv)
+{
+	int i;
+	for (i = 0; i < tpriv->num_urbs; i++) {
+		struct usbfs_urb *urb = tpriv->iso_urbs[i];
+		if (!urb)
+			break;
+		free(urb);
+	}
+
+	free(tpriv->iso_urbs);
+	tpriv->iso_urbs = NULL;
+}
+
+static int submit_bulk_transfer(struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer =
+		USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	struct linux_transfer_priv *tpriv = usbi_transfer_get_os_priv(itransfer);
+	struct linux_device_handle_priv *dpriv =
+		_device_handle_priv(transfer->dev_handle);
+	struct usbfs_urb *urbs;
+	int is_out = (transfer->endpoint & LIBUSB_ENDPOINT_DIR_MASK)
+		== LIBUSB_ENDPOINT_OUT;
+	int bulk_buffer_len, use_bulk_continuation;
+	int r;
+	int i;
+
+	if (is_out && (transfer->flags & LIBUSB_TRANSFER_ADD_ZERO_PACKET) &&
+			!(dpriv->caps & USBFS_CAP_ZERO_PACKET))
+		return LIBUSB_ERROR_NOT_SUPPORTED;
+
+	/*
+	 * Older versions of usbfs place a 16kb limit on bulk URBs. We work
+	 * around this by splitting large transfers into 16k blocks, and then
+	 * submit all urbs at once. it would be simpler to submit one urb at
+	 * a time, but there is a big performance gain doing it this way.
+	 *
+	 * Newer versions lift the 16k limit (USBFS_CAP_NO_PACKET_SIZE_LIM),
+	 * using arbritary large transfers can still be a bad idea though, as
+	 * the kernel needs to allocate physical contiguous memory for this,
+	 * which may fail for large buffers.
+	 *
+	 * The kernel solves this problem by splitting the transfer into
+	 * blocks itself when the host-controller is scatter-gather capable
+	 * (USBFS_CAP_BULK_SCATTER_GATHER), which most controllers are.
+	 *
+	 * Last, there is the issue of short-transfers when splitting, for
+	 * short split-transfers to work reliable USBFS_CAP_BULK_CONTINUATION
+	 * is needed, but this is not always available.
+	 */
+	if (dpriv->caps & USBFS_CAP_BULK_SCATTER_GATHER) {
+		/* Good! Just submit everything in one go */
+		bulk_buffer_len = transfer->length ? transfer->length : 1;
+		use_bulk_continuation = 0;
+	} else if (dpriv->caps & USBFS_CAP_BULK_CONTINUATION) {
+		/* Split the transfers and use bulk-continuation to
+		   avoid issues with short-transfers */
+		bulk_buffer_len = MAX_BULK_BUFFER_LENGTH;
+		use_bulk_continuation = 1;
+	} else if (dpriv->caps & USBFS_CAP_NO_PACKET_SIZE_LIM) {
+		/* Don't split, assume the kernel can alloc the buffer
+		   (otherwise the submit will fail with -ENOMEM) */
+		bulk_buffer_len = transfer->length ? transfer->length : 1;
+		use_bulk_continuation = 0;
+	} else {
+		/* Bad, splitting without bulk-continuation, short transfers
+		   which end before the last urb will not work reliable! */
+		/* Note we don't warn here as this is "normal" on kernels <
+		   2.6.32 and not a problem for most applications */
+		bulk_buffer_len = MAX_BULK_BUFFER_LENGTH;
+		use_bulk_continuation = 0;
+	}
+
+	int num_urbs = transfer->length / bulk_buffer_len;
+	int last_urb_partial = 0;
+
+	if (transfer->length == 0) {
+		num_urbs = 1;
+	} else if ((transfer->length % bulk_buffer_len) > 0) {
+		last_urb_partial = 1;
+		num_urbs++;
+	}
+	usbi_dbg("need %d urbs for new transfer with length %d", num_urbs,
+		transfer->length);
+	urbs = calloc(num_urbs, sizeof(struct usbfs_urb));
+	if (!urbs)
+		return LIBUSB_ERROR_NO_MEM;
+	tpriv->urbs = urbs;
+	tpriv->num_urbs = num_urbs;
+	tpriv->num_retired = 0;
+	tpriv->reap_action = NORMAL;
+	tpriv->reap_status = LIBUSB_TRANSFER_COMPLETED;
+
+	for (i = 0; i < num_urbs; i++) {
+		struct usbfs_urb *urb = &urbs[i];
+		urb->usercontext = itransfer;
+		switch (transfer->type) {
+		case LIBUSB_TRANSFER_TYPE_BULK:
+			urb->type = USBFS_URB_TYPE_BULK;
+			urb->stream_id = 0;
+			break;
+		case LIBUSB_TRANSFER_TYPE_BULK_STREAM:
+			urb->type = USBFS_URB_TYPE_BULK;
+			urb->stream_id = itransfer->stream_id;
+			break;
+		case LIBUSB_TRANSFER_TYPE_INTERRUPT:
+			urb->type = USBFS_URB_TYPE_INTERRUPT;
+			break;
+		}
+		urb->endpoint = transfer->endpoint;
+		urb->buffer = transfer->buffer + (i * bulk_buffer_len);
+		/* don't set the short not ok flag for the last URB */
+		if (use_bulk_continuation && !is_out && (i < num_urbs - 1))
+			urb->flags = USBFS_URB_SHORT_NOT_OK;
+		if (i == num_urbs - 1 && last_urb_partial)
+			urb->buffer_length = transfer->length % bulk_buffer_len;
+		else if (transfer->length == 0)
+			urb->buffer_length = 0;
+		else
+			urb->buffer_length = bulk_buffer_len;
+
+		if (i > 0 && use_bulk_continuation)
+			urb->flags |= USBFS_URB_BULK_CONTINUATION;
+
+		/* we have already checked that the flag is supported */
+		if (is_out && i == num_urbs - 1 &&
+		    transfer->flags & LIBUSB_TRANSFER_ADD_ZERO_PACKET)
+			urb->flags |= USBFS_URB_ZERO_PACKET;
+
+		r = ioctl(dpriv->fd, IOCTL_USBFS_SUBMITURB, urb);
+		if (r < 0) {
+			if (errno == ENODEV) {
+				r = LIBUSB_ERROR_NO_DEVICE;
+			} else {
+				usbi_err(TRANSFER_CTX(transfer),
+					"submiturb failed error %d errno=%d", r, errno);
+				r = LIBUSB_ERROR_IO;
+			}
+
+			/* if the first URB submission fails, we can simply free up and
+			 * return failure immediately. */
+			if (i == 0) {
+				usbi_dbg("first URB failed, easy peasy");
+				free(urbs);
+				tpriv->urbs = NULL;
+				return r;
+			}
+
+			/* if it's not the first URB that failed, the situation is a bit
+			 * tricky. we may need to discard all previous URBs. there are
+			 * complications:
+			 *  - discarding is asynchronous - discarded urbs will be reaped
+			 *    later. the user must not have freed the transfer when the
+			 *    discarded URBs are reaped, otherwise libusb will be using
+			 *    freed memory.
+			 *  - the earlier URBs may have completed successfully and we do
+			 *    not want to throw away any data.
+			 *  - this URB failing may be no error; EREMOTEIO means that
+			 *    this transfer simply didn't need all the URBs we submitted
+			 * so, we report that the transfer was submitted successfully and
+			 * in case of error we discard all previous URBs. later when
+			 * the final reap completes we can report error to the user,
+			 * or success if an earlier URB was completed successfully.
+			 */
+			tpriv->reap_action = EREMOTEIO == errno ? COMPLETED_EARLY : SUBMIT_FAILED;
+
+			/* The URBs we haven't submitted yet we count as already
+			 * retired. */
+			tpriv->num_retired += num_urbs - i;
+
+			/* If we completed short then don't try to discard. */
+			if (COMPLETED_EARLY == tpriv->reap_action)
+				return 0;
+
+			discard_urbs(itransfer, 0, i);
+
+			usbi_dbg("reporting successful submission but waiting for %d "
+				"discards before reporting error", i);
+			return 0;
+		}
+	}
+
+	return 0;
+}
+
+static int submit_iso_transfer(struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer =
+		USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	struct linux_transfer_priv *tpriv = usbi_transfer_get_os_priv(itransfer);
+	struct linux_device_handle_priv *dpriv =
+		_device_handle_priv(transfer->dev_handle);
+	struct usbfs_urb **urbs;
+	size_t alloc_size;
+	int num_packets = transfer->num_iso_packets;
+	int i;
+	int this_urb_len = 0;
+	int num_urbs = 1;
+	int packet_offset = 0;
+	unsigned int packet_len;
+	unsigned char *urb_buffer = transfer->buffer;
+
+	/* usbfs places arbitrary limits on iso URBs. this limit has changed
+	 * at least three times, and it's difficult to accurately detect which
+	 * limit this running kernel might impose. so we attempt to submit
+	 * whatever the user has provided. if the kernel rejects the request
+	 * due to its size, we return an error indicating such to the user.
+	 */
+
+	/* calculate how many URBs we need */
+	for (i = 0; i < num_packets; i++) {
+		unsigned int space_remaining = MAX_ISO_BUFFER_LENGTH - this_urb_len;
+		packet_len = transfer->iso_packet_desc[i].length;
+
+		if (packet_len > space_remaining) {
+			num_urbs++;
+			this_urb_len = packet_len;
+			/* check that we can actually support this packet length */
+			if (this_urb_len > MAX_ISO_BUFFER_LENGTH)
+				return LIBUSB_ERROR_INVALID_PARAM;
+		} else {
+			this_urb_len += packet_len;
+		}
+	}
+	usbi_dbg("need %d %dk URBs for transfer", num_urbs, MAX_ISO_BUFFER_LENGTH / 1024);
+
+	urbs = calloc(num_urbs, sizeof(*urbs));
+	if (!urbs)
+		return LIBUSB_ERROR_NO_MEM;
+
+	tpriv->iso_urbs = urbs;
+	tpriv->num_urbs = num_urbs;
+	tpriv->num_retired = 0;
+	tpriv->reap_action = NORMAL;
+	tpriv->iso_packet_offset = 0;
+
+	/* allocate + initialize each URB with the correct number of packets */
+	for (i = 0; i < num_urbs; i++) {
+		struct usbfs_urb *urb;
+		unsigned int space_remaining_in_urb = MAX_ISO_BUFFER_LENGTH;
+		int urb_packet_offset = 0;
+		unsigned char *urb_buffer_orig = urb_buffer;
+		int j;
+		int k;
+
+		/* swallow up all the packets we can fit into this URB */
+		while (packet_offset < transfer->num_iso_packets) {
+			packet_len = transfer->iso_packet_desc[packet_offset].length;
+			if (packet_len <= space_remaining_in_urb) {
+				/* throw it in */
+				urb_packet_offset++;
+				packet_offset++;
+				space_remaining_in_urb -= packet_len;
+				urb_buffer += packet_len;
+			} else {
+				/* it can't fit, save it for the next URB */
+				break;
+			}
+		}
+
+		alloc_size = sizeof(*urb)
+			+ (urb_packet_offset * sizeof(struct usbfs_iso_packet_desc));
+		urb = calloc(1, alloc_size);
+		if (!urb) {
+			free_iso_urbs(tpriv);
+			return LIBUSB_ERROR_NO_MEM;
+		}
+		urbs[i] = urb;
+
+		/* populate packet lengths */
+		for (j = 0, k = packet_offset - urb_packet_offset;
+				k < packet_offset; k++, j++) {
+			packet_len = transfer->iso_packet_desc[k].length;
+			urb->iso_frame_desc[j].length = packet_len;
+		}
+
+		urb->usercontext = itransfer;
+		urb->type = USBFS_URB_TYPE_ISO;
+		/* FIXME: interface for non-ASAP data? */
+		urb->flags = USBFS_URB_ISO_ASAP;
+		urb->endpoint = transfer->endpoint;
+		urb->number_of_packets = urb_packet_offset;
+		urb->buffer = urb_buffer_orig;
+	}
+
+	/* submit URBs */
+	for (i = 0; i < num_urbs; i++) {
+		int r = ioctl(dpriv->fd, IOCTL_USBFS_SUBMITURB, urbs[i]);
+		if (r < 0) {
+			if (errno == ENODEV) {
+				r = LIBUSB_ERROR_NO_DEVICE;
+			} else if (errno == EINVAL) {
+				usbi_warn(TRANSFER_CTX(transfer),
+					"submiturb failed, transfer too large");
+				r = LIBUSB_ERROR_INVALID_PARAM;
+			} else {
+				usbi_err(TRANSFER_CTX(transfer),
+					"submiturb failed error %d errno=%d", r, errno);
+				r = LIBUSB_ERROR_IO;
+			}
+
+			/* if the first URB submission fails, we can simply free up and
+			 * return failure immediately. */
+			if (i == 0) {
+				usbi_dbg("first URB failed, easy peasy");
+				free_iso_urbs(tpriv);
+				return r;
+			}
+
+			/* if it's not the first URB that failed, the situation is a bit
+			 * tricky. we must discard all previous URBs. there are
+			 * complications:
+			 *  - discarding is asynchronous - discarded urbs will be reaped
+			 *    later. the user must not have freed the transfer when the
+			 *    discarded URBs are reaped, otherwise libusb will be using
+			 *    freed memory.
+			 *  - the earlier URBs may have completed successfully and we do
+			 *    not want to throw away any data.
+			 * so, in this case we discard all the previous URBs BUT we report
+			 * that the transfer was submitted successfully. then later when
+			 * the final discard completes we can report error to the user.
+			 */
+			tpriv->reap_action = SUBMIT_FAILED;
+
+			/* The URBs we haven't submitted yet we count as already
+			 * retired. */
+			tpriv->num_retired = num_urbs - i;
+			discard_urbs(itransfer, 0, i);
+
+			usbi_dbg("reporting successful submission but waiting for %d "
+				"discards before reporting error", i);
+			return 0;
+		}
+	}
+
+	return 0;
+}
+
+static int submit_control_transfer(struct usbi_transfer *itransfer)
+{
+	struct linux_transfer_priv *tpriv = usbi_transfer_get_os_priv(itransfer);
+	struct libusb_transfer *transfer =
+		USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	struct linux_device_handle_priv *dpriv =
+		_device_handle_priv(transfer->dev_handle);
+	struct usbfs_urb *urb;
+	int r;
+
+	if (transfer->length - LIBUSB_CONTROL_SETUP_SIZE > MAX_CTRL_BUFFER_LENGTH)
+		return LIBUSB_ERROR_INVALID_PARAM;
+
+	urb = calloc(1, sizeof(struct usbfs_urb));
+	if (!urb)
+		return LIBUSB_ERROR_NO_MEM;
+	tpriv->urbs = urb;
+	tpriv->num_urbs = 1;
+	tpriv->reap_action = NORMAL;
+
+	urb->usercontext = itransfer;
+	urb->type = USBFS_URB_TYPE_CONTROL;
+	urb->endpoint = transfer->endpoint;
+	urb->buffer = transfer->buffer;
+	urb->buffer_length = transfer->length;
+
+	r = ioctl(dpriv->fd, IOCTL_USBFS_SUBMITURB, urb);
+	if (r < 0) {
+		free(urb);
+		tpriv->urbs = NULL;
+		if (errno == ENODEV)
+			return LIBUSB_ERROR_NO_DEVICE;
+
+		usbi_err(TRANSFER_CTX(transfer),
+			"submiturb failed error %d errno=%d", r, errno);
+		return LIBUSB_ERROR_IO;
+	}
+	return 0;
+}
+
+static int op_submit_transfer(struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer =
+		USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+
+	switch (transfer->type) {
+	case LIBUSB_TRANSFER_TYPE_CONTROL:
+		return submit_control_transfer(itransfer);
+	case LIBUSB_TRANSFER_TYPE_BULK:
+	case LIBUSB_TRANSFER_TYPE_BULK_STREAM:
+		return submit_bulk_transfer(itransfer);
+	case LIBUSB_TRANSFER_TYPE_INTERRUPT:
+		return submit_bulk_transfer(itransfer);
+	case LIBUSB_TRANSFER_TYPE_ISOCHRONOUS:
+		return submit_iso_transfer(itransfer);
+	default:
+		usbi_err(TRANSFER_CTX(transfer),
+			"unknown endpoint type %d", transfer->type);
+		return LIBUSB_ERROR_INVALID_PARAM;
+	}
+}
+
+static int op_cancel_transfer(struct usbi_transfer *itransfer)
+{
+	struct linux_transfer_priv *tpriv = usbi_transfer_get_os_priv(itransfer);
+	struct libusb_transfer *transfer =
+		USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	int r;
+
+	if (!tpriv->urbs)
+		return LIBUSB_ERROR_NOT_FOUND;
+
+	r = discard_urbs(itransfer, 0, tpriv->num_urbs);
+	if (r != 0)
+		return r;
+
+	switch (transfer->type) {
+	case LIBUSB_TRANSFER_TYPE_BULK:
+	case LIBUSB_TRANSFER_TYPE_BULK_STREAM:
+		if (tpriv->reap_action == ERROR)
+			break;
+		/* else, fall through */
+	default:
+		tpriv->reap_action = CANCELLED;
+	}
+
+	return 0;
+}
+
+static void op_clear_transfer_priv(struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer =
+		USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	struct linux_transfer_priv *tpriv = usbi_transfer_get_os_priv(itransfer);
+
+	/* urbs can be freed also in submit_transfer so lock mutex first */
+	switch (transfer->type) {
+	case LIBUSB_TRANSFER_TYPE_CONTROL:
+	case LIBUSB_TRANSFER_TYPE_BULK:
+	case LIBUSB_TRANSFER_TYPE_BULK_STREAM:
+	case LIBUSB_TRANSFER_TYPE_INTERRUPT:
+		if (tpriv->urbs) {
+			free(tpriv->urbs);
+			tpriv->urbs = NULL;
+		}
+		break;
+	case LIBUSB_TRANSFER_TYPE_ISOCHRONOUS:
+		if (tpriv->iso_urbs) {
+			free_iso_urbs(tpriv);
+			tpriv->iso_urbs = NULL;
+		}
+		break;
+	default:
+		usbi_err(TRANSFER_CTX(transfer),
+			"unknown endpoint type %d", transfer->type);
+	}
+}
+
+static int handle_bulk_completion(struct usbi_transfer *itransfer,
+	struct usbfs_urb *urb)
+{
+	struct linux_transfer_priv *tpriv = usbi_transfer_get_os_priv(itransfer);
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	int urb_idx = urb - tpriv->urbs;
+
+	usbi_mutex_lock(&itransfer->lock);
+	usbi_dbg("handling completion status %d of bulk urb %d/%d", urb->status,
+		urb_idx + 1, tpriv->num_urbs);
+
+	tpriv->num_retired++;
+
+	if (tpriv->reap_action != NORMAL) {
+		/* cancelled, submit_fail, or completed early */
+		usbi_dbg("abnormal reap: urb status %d", urb->status);
+
+		/* even though we're in the process of cancelling, it's possible that
+		 * we may receive some data in these URBs that we don't want to lose.
+		 * examples:
+		 * 1. while the kernel is cancelling all the packets that make up an
+		 *    URB, a few of them might complete. so we get back a successful
+		 *    cancellation *and* some data.
+		 * 2. we receive a short URB which marks the early completion condition,
+		 *    so we start cancelling the remaining URBs. however, we're too
+		 *    slow and another URB completes (or at least completes partially).
+		 *    (this can't happen since we always use BULK_CONTINUATION.)
+		 *
+		 * When this happens, our objectives are not to lose any "surplus" data,
+		 * and also to stick it at the end of the previously-received data
+		 * (closing any holes), so that libusb reports the total amount of
+		 * transferred data and presents it in a contiguous chunk.
+		 */
+		if (urb->actual_length > 0) {
+			unsigned char *target = transfer->buffer + itransfer->transferred;
+			usbi_dbg("received %d bytes of surplus data", urb->actual_length);
+			if (urb->buffer != target) {
+				usbi_dbg("moving surplus data from offset %d to offset %d",
+					(unsigned char *) urb->buffer - transfer->buffer,
+					target - transfer->buffer);
+				memmove(target, urb->buffer, urb->actual_length);
+			}
+			itransfer->transferred += urb->actual_length;
+		}
+
+		if (tpriv->num_retired == tpriv->num_urbs) {
+			usbi_dbg("abnormal reap: last URB handled, reporting");
+			if (tpriv->reap_action != COMPLETED_EARLY &&
+			    tpriv->reap_status == LIBUSB_TRANSFER_COMPLETED)
+				tpriv->reap_status = LIBUSB_TRANSFER_ERROR;
+			goto completed;
+		}
+		goto out_unlock;
+	}
+
+	itransfer->transferred += urb->actual_length;
+
+	/* Many of these errors can occur on *any* urb of a multi-urb
+	 * transfer.  When they do, we tear down the rest of the transfer.
+	 */
+	switch (urb->status) {
+	case 0:
+		break;
+	case -EREMOTEIO: /* short transfer */
+		break;
+	case -ENOENT: /* cancelled */
+	case -ECONNRESET:
+		break;
+	case -ENODEV:
+	case -ESHUTDOWN:
+		usbi_dbg("device removed");
+		tpriv->reap_status = LIBUSB_TRANSFER_NO_DEVICE;
+		goto cancel_remaining;
+	case -EPIPE:
+		usbi_dbg("detected endpoint stall");
+		if (tpriv->reap_status == LIBUSB_TRANSFER_COMPLETED)
+			tpriv->reap_status = LIBUSB_TRANSFER_STALL;
+		goto cancel_remaining;
+	case -EOVERFLOW:
+		/* overflow can only ever occur in the last urb */
+		usbi_dbg("overflow, actual_length=%d", urb->actual_length);
+		if (tpriv->reap_status == LIBUSB_TRANSFER_COMPLETED)
+			tpriv->reap_status = LIBUSB_TRANSFER_OVERFLOW;
+		goto completed;
+	case -ETIME:
+	case -EPROTO:
+	case -EILSEQ:
+	case -ECOMM:
+	case -ENOSR:
+		usbi_dbg("low level error %d", urb->status);
+		tpriv->reap_action = ERROR;
+		goto cancel_remaining;
+	default:
+		usbi_warn(ITRANSFER_CTX(itransfer),
+			"unrecognised urb status %d", urb->status);
+		tpriv->reap_action = ERROR;
+		goto cancel_remaining;
+	}
+
+	/* if we're the last urb or we got less data than requested then we're
+	 * done */
+	if (urb_idx == tpriv->num_urbs - 1) {
+		usbi_dbg("last URB in transfer --> complete!");
+		goto completed;
+	} else if (urb->actual_length < urb->buffer_length) {
+		usbi_dbg("short transfer %d/%d --> complete!",
+			urb->actual_length, urb->buffer_length);
+		if (tpriv->reap_action == NORMAL)
+			tpriv->reap_action = COMPLETED_EARLY;
+	} else
+		goto out_unlock;
+
+cancel_remaining:
+	if (ERROR == tpriv->reap_action && LIBUSB_TRANSFER_COMPLETED == tpriv->reap_status)
+		tpriv->reap_status = LIBUSB_TRANSFER_ERROR;
+
+	if (tpriv->num_retired == tpriv->num_urbs) /* nothing to cancel */
+		goto completed;
+
+	/* cancel remaining urbs and wait for their completion before
+	 * reporting results */
+	discard_urbs(itransfer, urb_idx + 1, tpriv->num_urbs);
+
+out_unlock:
+	usbi_mutex_unlock(&itransfer->lock);
+	return 0;
+
+completed:
+	free(tpriv->urbs);
+	tpriv->urbs = NULL;
+	usbi_mutex_unlock(&itransfer->lock);
+	return CANCELLED == tpriv->reap_action ?
+		usbi_handle_transfer_cancellation(itransfer) :
+		usbi_handle_transfer_completion(itransfer, tpriv->reap_status);
+}
+
+static int handle_iso_completion(struct usbi_transfer *itransfer,
+	struct usbfs_urb *urb)
+{
+	struct libusb_transfer *transfer =
+		USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	struct linux_transfer_priv *tpriv = usbi_transfer_get_os_priv(itransfer);
+	int num_urbs = tpriv->num_urbs;
+	int urb_idx = 0;
+	int i;
+	enum libusb_transfer_status status = LIBUSB_TRANSFER_COMPLETED;
+
+	usbi_mutex_lock(&itransfer->lock);
+	for (i = 0; i < num_urbs; i++) {
+		if (urb == tpriv->iso_urbs[i]) {
+			urb_idx = i + 1;
+			break;
+		}
+	}
+	if (urb_idx == 0) {
+		usbi_err(TRANSFER_CTX(transfer), "could not locate urb!");
+		usbi_mutex_unlock(&itransfer->lock);
+		return LIBUSB_ERROR_NOT_FOUND;
+	}
+
+	usbi_dbg("handling completion status %d of iso urb %d/%d", urb->status,
+		urb_idx, num_urbs);
+
+	/* copy isochronous results back in */
+
+	for (i = 0; i < urb->number_of_packets; i++) {
+		struct usbfs_iso_packet_desc *urb_desc = &urb->iso_frame_desc[i];
+		struct libusb_iso_packet_descriptor *lib_desc =
+			&transfer->iso_packet_desc[tpriv->iso_packet_offset++];
+		lib_desc->status = LIBUSB_TRANSFER_COMPLETED;
+		switch (urb_desc->status) {
+		case 0:
+			break;
+		case -ENOENT: /* cancelled */
+		case -ECONNRESET:
+			break;
+		case -ENODEV:
+		case -ESHUTDOWN:
+			usbi_dbg("device removed");
+			lib_desc->status = LIBUSB_TRANSFER_NO_DEVICE;
+			break;
+		case -EPIPE:
+			usbi_dbg("detected endpoint stall");
+			lib_desc->status = LIBUSB_TRANSFER_STALL;
+			break;
+		case -EOVERFLOW:
+			usbi_dbg("overflow error");
+			lib_desc->status = LIBUSB_TRANSFER_OVERFLOW;
+			break;
+		case -ETIME:
+		case -EPROTO:
+		case -EILSEQ:
+		case -ECOMM:
+		case -ENOSR:
+		case -EXDEV:
+			usbi_dbg("low-level USB error %d", urb_desc->status);
+			lib_desc->status = LIBUSB_TRANSFER_ERROR;
+			break;
+		default:
+			usbi_warn(TRANSFER_CTX(transfer),
+				"unrecognised urb status %d", urb_desc->status);
+			lib_desc->status = LIBUSB_TRANSFER_ERROR;
+			break;
+		}
+		lib_desc->actual_length = urb_desc->actual_length;
+	}
+
+	tpriv->num_retired++;
+
+	if (tpriv->reap_action != NORMAL) { /* cancelled or submit_fail */
+		usbi_dbg("CANCEL: urb status %d", urb->status);
+
+		if (tpriv->num_retired == num_urbs) {
+			usbi_dbg("CANCEL: last URB handled, reporting");
+			free_iso_urbs(tpriv);
+			if (tpriv->reap_action == CANCELLED) {
+				usbi_mutex_unlock(&itransfer->lock);
+				return usbi_handle_transfer_cancellation(itransfer);
+			} else {
+				usbi_mutex_unlock(&itransfer->lock);
+				return usbi_handle_transfer_completion(itransfer,
+					LIBUSB_TRANSFER_ERROR);
+			}
+		}
+		goto out;
+	}
+
+	switch (urb->status) {
+	case 0:
+		break;
+	case -ENOENT: /* cancelled */
+	case -ECONNRESET:
+		break;
+	case -ESHUTDOWN:
+		usbi_dbg("device removed");
+		status = LIBUSB_TRANSFER_NO_DEVICE;
+		break;
+	default:
+		usbi_warn(TRANSFER_CTX(transfer),
+			"unrecognised urb status %d", urb->status);
+		status = LIBUSB_TRANSFER_ERROR;
+		break;
+	}
+
+	/* if we're the last urb then we're done */
+	if (urb_idx == num_urbs) {
+		usbi_dbg("last URB in transfer --> complete!");
+		free_iso_urbs(tpriv);
+		usbi_mutex_unlock(&itransfer->lock);
+		return usbi_handle_transfer_completion(itransfer, status);
+	}
+
+out:
+	usbi_mutex_unlock(&itransfer->lock);
+	return 0;
+}
+
+static int handle_control_completion(struct usbi_transfer *itransfer,
+	struct usbfs_urb *urb)
+{
+	struct linux_transfer_priv *tpriv = usbi_transfer_get_os_priv(itransfer);
+	int status;
+
+	usbi_mutex_lock(&itransfer->lock);
+	usbi_dbg("handling completion status %d", urb->status);
+
+	itransfer->transferred += urb->actual_length;
+
+	if (tpriv->reap_action == CANCELLED) {
+		if (urb->status != 0 && urb->status != -ENOENT)
+			usbi_warn(ITRANSFER_CTX(itransfer),
+				"cancel: unrecognised urb status %d", urb->status);
+		free(tpriv->urbs);
+		tpriv->urbs = NULL;
+		usbi_mutex_unlock(&itransfer->lock);
+		return usbi_handle_transfer_cancellation(itransfer);
+	}
+
+	switch (urb->status) {
+	case 0:
+		status = LIBUSB_TRANSFER_COMPLETED;
+		break;
+	case -ENOENT: /* cancelled */
+		status = LIBUSB_TRANSFER_CANCELLED;
+		break;
+	case -ENODEV:
+	case -ESHUTDOWN:
+		usbi_dbg("device removed");
+		status = LIBUSB_TRANSFER_NO_DEVICE;
+		break;
+	case -EPIPE:
+		usbi_dbg("unsupported control request");
+		status = LIBUSB_TRANSFER_STALL;
+		break;
+	case -EOVERFLOW:
+		usbi_dbg("control overflow error");
+		status = LIBUSB_TRANSFER_OVERFLOW;
+		break;
+	case -ETIME:
+	case -EPROTO:
+	case -EILSEQ:
+	case -ECOMM:
+	case -ENOSR:
+		usbi_dbg("low-level bus error occurred");
+		status = LIBUSB_TRANSFER_ERROR;
+		break;
+	default:
+		usbi_warn(ITRANSFER_CTX(itransfer),
+			"unrecognised urb status %d", urb->status);
+		status = LIBUSB_TRANSFER_ERROR;
+		break;
+	}
+
+	free(tpriv->urbs);
+	tpriv->urbs = NULL;
+	usbi_mutex_unlock(&itransfer->lock);
+	return usbi_handle_transfer_completion(itransfer, status);
+}
+
+static int reap_for_handle(struct libusb_device_handle *handle)
+{
+	struct linux_device_handle_priv *hpriv = _device_handle_priv(handle);
+	int r;
+	struct usbfs_urb *urb;
+	struct usbi_transfer *itransfer;
+	struct libusb_transfer *transfer;
+
+	r = ioctl(hpriv->fd, IOCTL_USBFS_REAPURBNDELAY, &urb);
+	if (r == -1 && errno == EAGAIN)
+		return 1;
+	if (r < 0) {
+		if (errno == ENODEV)
+			return LIBUSB_ERROR_NO_DEVICE;
+
+		usbi_err(HANDLE_CTX(handle), "reap failed error %d errno=%d",
+			r, errno);
+		return LIBUSB_ERROR_IO;
+	}
+
+	itransfer = urb->usercontext;
+	transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+
+	usbi_dbg("urb type=%d status=%d transferred=%d", urb->type, urb->status,
+		urb->actual_length);
+
+	switch (transfer->type) {
+	case LIBUSB_TRANSFER_TYPE_ISOCHRONOUS:
+		return handle_iso_completion(itransfer, urb);
+	case LIBUSB_TRANSFER_TYPE_BULK:
+	case LIBUSB_TRANSFER_TYPE_BULK_STREAM:
+	case LIBUSB_TRANSFER_TYPE_INTERRUPT:
+		return handle_bulk_completion(itransfer, urb);
+	case LIBUSB_TRANSFER_TYPE_CONTROL:
+		return handle_control_completion(itransfer, urb);
+	default:
+		usbi_err(HANDLE_CTX(handle), "unrecognised endpoint type %x",
+			transfer->type);
+		return LIBUSB_ERROR_OTHER;
+	}
+}
+
+static int op_handle_events(struct libusb_context *ctx,
+	struct pollfd *fds, POLL_NFDS_TYPE nfds, int num_ready)
+{
+	int r;
+	unsigned int i = 0;
+
+	usbi_mutex_lock(&ctx->open_devs_lock);
+	for (i = 0; i < nfds && num_ready > 0; i++) {
+		struct pollfd *pollfd = &fds[i];
+		struct libusb_device_handle *handle;
+		struct linux_device_handle_priv *hpriv = NULL;
+
+		if (!pollfd->revents)
+			continue;
+
+		num_ready--;
+		list_for_each_entry(handle, &ctx->open_devs, list, struct libusb_device_handle) {
+			hpriv = _device_handle_priv(handle);
+			if (hpriv->fd == pollfd->fd)
+				break;
+		}
+
+		if (!hpriv || hpriv->fd != pollfd->fd) {
+			usbi_err(ctx, "cannot find handle for fd %d",
+				 pollfd->fd);
+			continue;
+		}
+
+		if (pollfd->revents & POLLERR) {
+			/* remove the fd from the pollfd set so that it doesn't continuously
+			 * trigger an event, and flag that it has been removed so op_close()
+			 * doesn't try to remove it a second time */
+			usbi_remove_pollfd(HANDLE_CTX(handle), hpriv->fd);
+			hpriv->fd_removed = 1;
+
+			/* device will still be marked as attached if hotplug monitor thread
+			 * hasn't processed remove event yet */
+			usbi_mutex_static_lock(&linux_hotplug_lock);
+			if (handle->dev->attached)
+				linux_device_disconnected(handle->dev->bus_number,
+						handle->dev->device_address);
+			usbi_mutex_static_unlock(&linux_hotplug_lock);
+
+			if (hpriv->caps & USBFS_CAP_REAP_AFTER_DISCONNECT) {
+				do {
+					r = reap_for_handle(handle);
+				} while (r == 0);
+			}
+
+			usbi_handle_disconnect(handle);
+			continue;
+		}
+
+		do {
+			r = reap_for_handle(handle);
+		} while (r == 0);
+		if (r == 1 || r == LIBUSB_ERROR_NO_DEVICE)
+			continue;
+		else if (r < 0)
+			goto out;
+	}
+
+	r = 0;
+out:
+	usbi_mutex_unlock(&ctx->open_devs_lock);
+	return r;
+}
+
+static int op_clock_gettime(int clk_id, struct timespec *tp)
+{
+	switch (clk_id) {
+	case USBI_CLOCK_MONOTONIC:
+		return clock_gettime(monotonic_clkid, tp);
+	case USBI_CLOCK_REALTIME:
+		return clock_gettime(CLOCK_REALTIME, tp);
+	default:
+		return LIBUSB_ERROR_INVALID_PARAM;
+  }
+}
+
+#ifdef USBI_TIMERFD_AVAILABLE
+static clockid_t op_get_timerfd_clockid(void)
+{
+	return monotonic_clkid;
+
+}
+#endif
+
+const struct usbi_os_backend linux_usbfs_backend = {
+	.name = "Linux usbfs",
+	.caps = USBI_CAP_HAS_HID_ACCESS|USBI_CAP_SUPPORTS_DETACH_KERNEL_DRIVER,
+	.init = op_init,
+	.exit = op_exit,
+	.get_device_list = NULL,
+	.hotplug_poll = op_hotplug_poll,
+	.get_device_descriptor = op_get_device_descriptor,
+	.get_active_config_descriptor = op_get_active_config_descriptor,
+	.get_config_descriptor = op_get_config_descriptor,
+	.get_config_descriptor_by_value = op_get_config_descriptor_by_value,
+
+	.open = op_open,
+	.close = op_close,
+	.get_configuration = op_get_configuration,
+	.set_configuration = op_set_configuration,
+	.claim_interface = op_claim_interface,
+	.release_interface = op_release_interface,
+
+	.set_interface_altsetting = op_set_interface,
+	.clear_halt = op_clear_halt,
+	.reset_device = op_reset_device,
+
+	.alloc_streams = op_alloc_streams,
+	.free_streams = op_free_streams,
+
+	.dev_mem_alloc = op_dev_mem_alloc,
+	.dev_mem_free = op_dev_mem_free,
+
+	.kernel_driver_active = op_kernel_driver_active,
+	.detach_kernel_driver = op_detach_kernel_driver,
+	.attach_kernel_driver = op_attach_kernel_driver,
+
+	.destroy_device = op_destroy_device,
+
+	.submit_transfer = op_submit_transfer,
+	.cancel_transfer = op_cancel_transfer,
+	.clear_transfer_priv = op_clear_transfer_priv,
+
+	.handle_events = op_handle_events,
+
+	.clock_gettime = op_clock_gettime,
+
+#ifdef USBI_TIMERFD_AVAILABLE
+	.get_timerfd_clockid = op_get_timerfd_clockid,
+#endif
+
+	.device_priv_size = sizeof(struct linux_device_priv),
+	.device_handle_priv_size = sizeof(struct linux_device_handle_priv),
+	.transfer_priv_size = sizeof(struct linux_transfer_priv),
+};
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/linux_usbfs.h b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/linux_usbfs.h
new file mode 100644
index 000000000..8bd3ebcb1
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/linux_usbfs.h
@@ -0,0 +1,193 @@
+/*
+ * usbfs header structures
+ * Copyright © 2007 Daniel Drake <dsd@gentoo.org>
+ * Copyright © 2001 Johannes Erdfelt <johannes@erdfelt.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef LIBUSB_USBFS_H
+#define LIBUSB_USBFS_H
+
+#include <linux/types.h>
+
+#define SYSFS_DEVICE_PATH "/sys/bus/usb/devices"
+
+struct usbfs_ctrltransfer {
+	/* keep in sync with usbdevice_fs.h:usbdevfs_ctrltransfer */
+	uint8_t  bmRequestType;
+	uint8_t  bRequest;
+	uint16_t wValue;
+	uint16_t wIndex;
+	uint16_t wLength;
+
+	uint32_t timeout;	/* in milliseconds */
+
+	/* pointer to data */
+	void *data;
+};
+
+struct usbfs_bulktransfer {
+	/* keep in sync with usbdevice_fs.h:usbdevfs_bulktransfer */
+	unsigned int ep;
+	unsigned int len;
+	unsigned int timeout;	/* in milliseconds */
+
+	/* pointer to data */
+	void *data;
+};
+
+struct usbfs_setinterface {
+	/* keep in sync with usbdevice_fs.h:usbdevfs_setinterface */
+	unsigned int interface;
+	unsigned int altsetting;
+};
+
+#define USBFS_MAXDRIVERNAME 255
+
+struct usbfs_getdriver {
+	unsigned int interface;
+	char driver[USBFS_MAXDRIVERNAME + 1];
+};
+
+#define USBFS_URB_SHORT_NOT_OK		0x01
+#define USBFS_URB_ISO_ASAP			0x02
+#define USBFS_URB_BULK_CONTINUATION	0x04
+#define USBFS_URB_QUEUE_BULK		0x10
+#define USBFS_URB_ZERO_PACKET		0x40
+
+enum usbfs_urb_type {
+	USBFS_URB_TYPE_ISO = 0,
+	USBFS_URB_TYPE_INTERRUPT = 1,
+	USBFS_URB_TYPE_CONTROL = 2,
+	USBFS_URB_TYPE_BULK = 3,
+};
+
+struct usbfs_iso_packet_desc {
+	unsigned int length;
+	unsigned int actual_length;
+	unsigned int status;
+};
+
+#define MAX_ISO_BUFFER_LENGTH		49152 * 128
+#define MAX_BULK_BUFFER_LENGTH		16384
+#define MAX_CTRL_BUFFER_LENGTH		4096
+
+struct usbfs_urb {
+	unsigned char type;
+	unsigned char endpoint;
+	int status;
+	unsigned int flags;
+	void *buffer;
+	int buffer_length;
+	int actual_length;
+	int start_frame;
+	union {
+		int number_of_packets;	/* Only used for isoc urbs */
+		unsigned int stream_id;	/* Only used with bulk streams */
+	};
+	int error_count;
+	unsigned int signr;
+	void *usercontext;
+	struct usbfs_iso_packet_desc iso_frame_desc[0];
+};
+
+struct usbfs_connectinfo {
+	unsigned int devnum;
+	unsigned char slow;
+};
+
+struct usbfs_ioctl {
+	int ifno;	/* interface 0..N ; negative numbers reserved */
+	int ioctl_code;	/* MUST encode size + direction of data so the
+			 * macros in <asm/ioctl.h> give correct values */
+	void *data;	/* param buffer (in, or out) */
+};
+
+struct usbfs_hub_portinfo {
+	unsigned char numports;
+	unsigned char port[127];	/* port to device num mapping */
+};
+
+#define USBFS_CAP_ZERO_PACKET		0x01
+#define USBFS_CAP_BULK_CONTINUATION	0x02
+#define USBFS_CAP_NO_PACKET_SIZE_LIM	0x04
+#define USBFS_CAP_BULK_SCATTER_GATHER	0x08
+#define USBFS_CAP_REAP_AFTER_DISCONNECT	0x10
+
+#define USBFS_DISCONNECT_CLAIM_IF_DRIVER	0x01
+#define USBFS_DISCONNECT_CLAIM_EXCEPT_DRIVER	0x02
+
+struct usbfs_disconnect_claim {
+	unsigned int interface;
+	unsigned int flags;
+	char driver[USBFS_MAXDRIVERNAME + 1];
+};
+
+struct usbfs_streams {
+	unsigned int num_streams; /* Not used by USBDEVFS_FREE_STREAMS */
+	unsigned int num_eps;
+	unsigned char eps[0];
+};
+
+#define IOCTL_USBFS_CONTROL	_IOWR('U', 0, struct usbfs_ctrltransfer)
+#define IOCTL_USBFS_BULK		_IOWR('U', 2, struct usbfs_bulktransfer)
+#define IOCTL_USBFS_RESETEP	_IOR('U', 3, unsigned int)
+#define IOCTL_USBFS_SETINTF	_IOR('U', 4, struct usbfs_setinterface)
+#define IOCTL_USBFS_SETCONFIG	_IOR('U', 5, unsigned int)
+#define IOCTL_USBFS_GETDRIVER	_IOW('U', 8, struct usbfs_getdriver)
+#define IOCTL_USBFS_SUBMITURB	_IOR('U', 10, struct usbfs_urb)
+#define IOCTL_USBFS_DISCARDURB	_IO('U', 11)
+#define IOCTL_USBFS_REAPURB	_IOW('U', 12, void *)
+#define IOCTL_USBFS_REAPURBNDELAY	_IOW('U', 13, void *)
+#define IOCTL_USBFS_CLAIMINTF	_IOR('U', 15, unsigned int)
+#define IOCTL_USBFS_RELEASEINTF	_IOR('U', 16, unsigned int)
+#define IOCTL_USBFS_CONNECTINFO	_IOW('U', 17, struct usbfs_connectinfo)
+#define IOCTL_USBFS_IOCTL         _IOWR('U', 18, struct usbfs_ioctl)
+#define IOCTL_USBFS_HUB_PORTINFO	_IOR('U', 19, struct usbfs_hub_portinfo)
+#define IOCTL_USBFS_RESET		_IO('U', 20)
+#define IOCTL_USBFS_CLEAR_HALT	_IOR('U', 21, unsigned int)
+#define IOCTL_USBFS_DISCONNECT	_IO('U', 22)
+#define IOCTL_USBFS_CONNECT	_IO('U', 23)
+#define IOCTL_USBFS_CLAIM_PORT	_IOR('U', 24, unsigned int)
+#define IOCTL_USBFS_RELEASE_PORT	_IOR('U', 25, unsigned int)
+#define IOCTL_USBFS_GET_CAPABILITIES	_IOR('U', 26, __u32)
+#define IOCTL_USBFS_DISCONNECT_CLAIM	_IOR('U', 27, struct usbfs_disconnect_claim)
+#define IOCTL_USBFS_ALLOC_STREAMS	_IOR('U', 28, struct usbfs_streams)
+#define IOCTL_USBFS_FREE_STREAMS	_IOR('U', 29, struct usbfs_streams)
+
+extern usbi_mutex_static_t linux_hotplug_lock;
+
+#if defined(HAVE_LIBUDEV)
+int linux_udev_start_event_monitor(void);
+int linux_udev_stop_event_monitor(void);
+int linux_udev_scan_devices(struct libusb_context *ctx);
+void linux_udev_hotplug_poll(void);
+#else
+int linux_netlink_start_event_monitor(void);
+int linux_netlink_stop_event_monitor(void);
+void linux_netlink_hotplug_poll(void);
+#endif
+
+void linux_hotplug_enumerate(uint8_t busnum, uint8_t devaddr, const char *sys_name);
+void linux_device_disconnected(uint8_t busnum, uint8_t devaddr);
+
+int linux_get_device_address (struct libusb_context *ctx, int detached,
+	uint8_t *busnum, uint8_t *devaddr, const char *dev_node,
+	const char *sys_name);
+int linux_enumerate_device(struct libusb_context *ctx,
+	uint8_t busnum, uint8_t devaddr, const char *sysfs_dir);
+
+#endif
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/netbsd_usb.c b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/netbsd_usb.c
new file mode 100644
index 000000000..ad1ede73e
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/netbsd_usb.c
@@ -0,0 +1,677 @@
+/*
+ * Copyright © 2011 Martin Pieuchot <mpi@openbsd.org>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <config.h>
+
+#include <sys/time.h>
+#include <sys/types.h>
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <dev/usb/usb.h>
+
+#include "libusbi.h"
+
+struct device_priv {
+	char devnode[16];
+	int fd;
+
+	unsigned char *cdesc;			/* active config descriptor */
+	usb_device_descriptor_t ddesc;		/* usb device descriptor */
+};
+
+struct handle_priv {
+	int endpoints[USB_MAX_ENDPOINTS];
+};
+
+/*
+ * Backend functions
+ */
+static int netbsd_get_device_list(struct libusb_context *,
+    struct discovered_devs **);
+static int netbsd_open(struct libusb_device_handle *);
+static void netbsd_close(struct libusb_device_handle *);
+
+static int netbsd_get_device_descriptor(struct libusb_device *, unsigned char *,
+    int *);
+static int netbsd_get_active_config_descriptor(struct libusb_device *,
+    unsigned char *, size_t, int *);
+static int netbsd_get_config_descriptor(struct libusb_device *, uint8_t,
+    unsigned char *, size_t, int *);
+
+static int netbsd_get_configuration(struct libusb_device_handle *, int *);
+static int netbsd_set_configuration(struct libusb_device_handle *, int);
+
+static int netbsd_claim_interface(struct libusb_device_handle *, int);
+static int netbsd_release_interface(struct libusb_device_handle *, int);
+
+static int netbsd_set_interface_altsetting(struct libusb_device_handle *, int,
+    int);
+static int netbsd_clear_halt(struct libusb_device_handle *, unsigned char);
+static int netbsd_reset_device(struct libusb_device_handle *);
+static void netbsd_destroy_device(struct libusb_device *);
+
+static int netbsd_submit_transfer(struct usbi_transfer *);
+static int netbsd_cancel_transfer(struct usbi_transfer *);
+static void netbsd_clear_transfer_priv(struct usbi_transfer *);
+static int netbsd_handle_transfer_completion(struct usbi_transfer *);
+static int netbsd_clock_gettime(int, struct timespec *);
+
+/*
+ * Private functions
+ */
+static int _errno_to_libusb(int);
+static int _cache_active_config_descriptor(struct libusb_device *, int);
+static int _sync_control_transfer(struct usbi_transfer *);
+static int _sync_gen_transfer(struct usbi_transfer *);
+static int _access_endpoint(struct libusb_transfer *);
+
+const struct usbi_os_backend netbsd_backend = {
+	"Synchronous NetBSD backend",
+	0,
+	NULL,				/* init() */
+	NULL,				/* exit() */
+	netbsd_get_device_list,
+	NULL,				/* hotplug_poll */
+	netbsd_open,
+	netbsd_close,
+
+	netbsd_get_device_descriptor,
+	netbsd_get_active_config_descriptor,
+	netbsd_get_config_descriptor,
+	NULL,				/* get_config_descriptor_by_value() */
+
+	netbsd_get_configuration,
+	netbsd_set_configuration,
+
+	netbsd_claim_interface,
+	netbsd_release_interface,
+
+	netbsd_set_interface_altsetting,
+	netbsd_clear_halt,
+	netbsd_reset_device,
+
+	NULL,				/* alloc_streams */
+	NULL,				/* free_streams */
+
+	NULL,				/* dev_mem_alloc() */
+	NULL,				/* dev_mem_free() */
+
+	NULL,				/* kernel_driver_active() */
+	NULL,				/* detach_kernel_driver() */
+	NULL,				/* attach_kernel_driver() */
+
+	netbsd_destroy_device,
+
+	netbsd_submit_transfer,
+	netbsd_cancel_transfer,
+	netbsd_clear_transfer_priv,
+
+	NULL,				/* handle_events() */
+	netbsd_handle_transfer_completion,
+
+	netbsd_clock_gettime,
+	sizeof(struct device_priv),
+	sizeof(struct handle_priv),
+	0,				/* transfer_priv_size */
+};
+
+int
+netbsd_get_device_list(struct libusb_context * ctx,
+	struct discovered_devs **discdevs)
+{
+	struct libusb_device *dev;
+	struct device_priv *dpriv;
+	struct usb_device_info di;
+	unsigned long session_id;
+	char devnode[16];
+	int fd, err, i;
+
+	usbi_dbg("");
+
+	/* Only ugen(4) is supported */
+	for (i = 0; i < USB_MAX_DEVICES; i++) {
+		/* Control endpoint is always .00 */
+		snprintf(devnode, sizeof(devnode), "/dev/ugen%d.00", i);
+
+		if ((fd = open(devnode, O_RDONLY)) < 0) {
+			if (errno != ENOENT && errno != ENXIO)
+				usbi_err(ctx, "could not open %s", devnode);
+			continue;
+		}
+
+		if (ioctl(fd, USB_GET_DEVICEINFO, &di) < 0)
+			continue;
+
+		session_id = (di.udi_bus << 8 | di.udi_addr);
+		dev = usbi_get_device_by_session_id(ctx, session_id);
+
+		if (dev == NULL) {
+			dev = usbi_alloc_device(ctx, session_id);
+			if (dev == NULL)
+				return (LIBUSB_ERROR_NO_MEM);
+
+			dev->bus_number = di.udi_bus;
+			dev->device_address = di.udi_addr;
+			dev->speed = di.udi_speed;
+
+			dpriv = (struct device_priv *)dev->os_priv;
+			strlcpy(dpriv->devnode, devnode, sizeof(devnode));
+			dpriv->fd = -1;
+
+			if (ioctl(fd, USB_GET_DEVICE_DESC, &dpriv->ddesc) < 0) {
+				err = errno;
+				goto error;
+			}
+
+			dpriv->cdesc = NULL;
+			if (_cache_active_config_descriptor(dev, fd)) {
+				err = errno;
+				goto error;
+			}
+
+			if ((err = usbi_sanitize_device(dev)))
+				goto error;
+		}
+		close(fd);
+
+		if (discovered_devs_append(*discdevs, dev) == NULL)
+			return (LIBUSB_ERROR_NO_MEM);
+
+		libusb_unref_device(dev);
+	}
+
+	return (LIBUSB_SUCCESS);
+
+error:
+	close(fd);
+	libusb_unref_device(dev);
+	return _errno_to_libusb(err);
+}
+
+int
+netbsd_open(struct libusb_device_handle *handle)
+{
+	struct handle_priv *hpriv = (struct handle_priv *)handle->os_priv;
+	struct device_priv *dpriv = (struct device_priv *)handle->dev->os_priv;
+
+	dpriv->fd = open(dpriv->devnode, O_RDWR);
+	if (dpriv->fd < 0) {
+		dpriv->fd = open(dpriv->devnode, O_RDONLY);
+		if (dpriv->fd < 0)
+			return _errno_to_libusb(errno);
+	}
+
+	usbi_dbg("open %s: fd %d", dpriv->devnode, dpriv->fd);
+
+	return (LIBUSB_SUCCESS);
+}
+
+void
+netbsd_close(struct libusb_device_handle *handle)
+{
+	struct handle_priv *hpriv = (struct handle_priv *)handle->os_priv;
+	struct device_priv *dpriv = (struct device_priv *)handle->dev->os_priv;
+
+	usbi_dbg("close: fd %d", dpriv->fd);
+
+	close(dpriv->fd);
+	dpriv->fd = -1;
+}
+
+int
+netbsd_get_device_descriptor(struct libusb_device *dev, unsigned char *buf,
+    int *host_endian)
+{
+	struct device_priv *dpriv = (struct device_priv *)dev->os_priv;
+
+	usbi_dbg("");
+
+	memcpy(buf, &dpriv->ddesc, DEVICE_DESC_LENGTH);
+
+	*host_endian = 0;
+
+	return (LIBUSB_SUCCESS);
+}
+
+int
+netbsd_get_active_config_descriptor(struct libusb_device *dev,
+    unsigned char *buf, size_t len, int *host_endian)
+{
+	struct device_priv *dpriv = (struct device_priv *)dev->os_priv;
+	usb_config_descriptor_t *ucd;
+
+	ucd = (usb_config_descriptor_t *) dpriv->cdesc;
+	len = MIN(len, UGETW(ucd->wTotalLength));
+
+	usbi_dbg("len %d", len);
+
+	memcpy(buf, dpriv->cdesc, len);
+
+	*host_endian = 0;
+
+	return len;
+}
+
+int
+netbsd_get_config_descriptor(struct libusb_device *dev, uint8_t idx,
+    unsigned char *buf, size_t len, int *host_endian)
+{
+	struct device_priv *dpriv = (struct device_priv *)dev->os_priv;
+	struct usb_full_desc ufd;
+	int fd, err;
+
+	usbi_dbg("index %d, len %d", idx, len);
+
+	/* A config descriptor may be requested before opening the device */
+	if (dpriv->fd >= 0) {
+		fd = dpriv->fd;
+	} else {
+		fd = open(dpriv->devnode, O_RDONLY);
+		if (fd < 0)
+			return _errno_to_libusb(errno);
+	}
+
+	ufd.ufd_config_index = idx;
+	ufd.ufd_size = len;
+	ufd.ufd_data = buf;
+
+	if ((ioctl(fd, USB_GET_FULL_DESC, &ufd)) < 0) {
+		err = errno;
+		if (dpriv->fd < 0)
+			close(fd);
+		return _errno_to_libusb(err);
+	}
+
+	if (dpriv->fd < 0)
+		close(fd);
+
+	*host_endian = 0;
+
+	return len;
+}
+
+int
+netbsd_get_configuration(struct libusb_device_handle *handle, int *config)
+{
+	struct device_priv *dpriv = (struct device_priv *)handle->dev->os_priv;
+
+	usbi_dbg("");
+
+	if (ioctl(dpriv->fd, USB_GET_CONFIG, config) < 0)
+		return _errno_to_libusb(errno);
+
+	usbi_dbg("configuration %d", *config);
+
+	return (LIBUSB_SUCCESS);
+}
+
+int
+netbsd_set_configuration(struct libusb_device_handle *handle, int config)
+{
+	struct device_priv *dpriv = (struct device_priv *)handle->dev->os_priv;
+
+	usbi_dbg("configuration %d", config);
+
+	if (ioctl(dpriv->fd, USB_SET_CONFIG, &config) < 0)
+		return _errno_to_libusb(errno);
+
+	return _cache_active_config_descriptor(handle->dev, dpriv->fd);
+}
+
+int
+netbsd_claim_interface(struct libusb_device_handle *handle, int iface)
+{
+	struct handle_priv *hpriv = (struct handle_priv *)handle->os_priv;
+	int i;
+
+	for (i = 0; i < USB_MAX_ENDPOINTS; i++)
+		hpriv->endpoints[i] = -1;
+
+	return (LIBUSB_SUCCESS);
+}
+
+int
+netbsd_release_interface(struct libusb_device_handle *handle, int iface)
+{
+	struct handle_priv *hpriv = (struct handle_priv *)handle->os_priv;
+	int i;
+
+	for (i = 0; i < USB_MAX_ENDPOINTS; i++)
+		if (hpriv->endpoints[i] >= 0)
+			close(hpriv->endpoints[i]);
+
+	return (LIBUSB_SUCCESS);
+}
+
+int
+netbsd_set_interface_altsetting(struct libusb_device_handle *handle, int iface,
+    int altsetting)
+{
+	struct device_priv *dpriv = (struct device_priv *)handle->dev->os_priv;
+	struct usb_alt_interface intf;
+
+	usbi_dbg("iface %d, setting %d", iface, altsetting);
+
+	memset(&intf, 0, sizeof(intf));
+
+	intf.uai_interface_index = iface;
+	intf.uai_alt_no = altsetting;
+
+	if (ioctl(dpriv->fd, USB_SET_ALTINTERFACE, &intf) < 0)
+		return _errno_to_libusb(errno);
+
+	return (LIBUSB_SUCCESS);
+}
+
+int
+netbsd_clear_halt(struct libusb_device_handle *handle, unsigned char endpoint)
+{
+	struct device_priv *dpriv = (struct device_priv *)handle->dev->os_priv;
+	struct usb_ctl_request req;
+
+	usbi_dbg("");
+
+	req.ucr_request.bmRequestType = UT_WRITE_ENDPOINT;
+	req.ucr_request.bRequest = UR_CLEAR_FEATURE;
+	USETW(req.ucr_request.wValue, UF_ENDPOINT_HALT);
+	USETW(req.ucr_request.wIndex, endpoint);
+	USETW(req.ucr_request.wLength, 0);
+
+	if (ioctl(dpriv->fd, USB_DO_REQUEST, &req) < 0)
+		return _errno_to_libusb(errno);
+
+	return (LIBUSB_SUCCESS);
+}
+
+int
+netbsd_reset_device(struct libusb_device_handle *handle)
+{
+	usbi_dbg("");
+
+	return (LIBUSB_ERROR_NOT_SUPPORTED);
+}
+
+void
+netbsd_destroy_device(struct libusb_device *dev)
+{
+	struct device_priv *dpriv = (struct device_priv *)dev->os_priv;
+
+	usbi_dbg("");
+
+	free(dpriv->cdesc);
+}
+
+int
+netbsd_submit_transfer(struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer;
+	struct handle_priv *hpriv;
+	int err = 0;
+
+	usbi_dbg("");
+
+	transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	hpriv = (struct handle_priv *)transfer->dev_handle->os_priv;
+
+	switch (transfer->type) {
+	case LIBUSB_TRANSFER_TYPE_CONTROL:
+		err = _sync_control_transfer(itransfer);
+		break;
+	case LIBUSB_TRANSFER_TYPE_ISOCHRONOUS:
+		if (IS_XFEROUT(transfer)) {
+			/* Isochronous write is not supported */
+			err = LIBUSB_ERROR_NOT_SUPPORTED;
+			break;
+		}
+		err = _sync_gen_transfer(itransfer);
+		break;
+	case LIBUSB_TRANSFER_TYPE_BULK:
+	case LIBUSB_TRANSFER_TYPE_INTERRUPT:
+		if (IS_XFEROUT(transfer) &&
+		    transfer->flags & LIBUSB_TRANSFER_ADD_ZERO_PACKET) {
+			err = LIBUSB_ERROR_NOT_SUPPORTED;
+			break;
+		}
+		err = _sync_gen_transfer(itransfer);
+		break;
+	case LIBUSB_TRANSFER_TYPE_BULK_STREAM:
+		err = LIBUSB_ERROR_NOT_SUPPORTED;
+		break;
+	}
+
+	if (err)
+		return (err);
+
+	usbi_signal_transfer_completion(itransfer);
+
+	return (LIBUSB_SUCCESS);
+}
+
+int
+netbsd_cancel_transfer(struct usbi_transfer *itransfer)
+{
+	usbi_dbg("");
+
+	return (LIBUSB_ERROR_NOT_SUPPORTED);
+}
+
+void
+netbsd_clear_transfer_priv(struct usbi_transfer *itransfer)
+{
+	usbi_dbg("");
+
+	/* Nothing to do */
+}
+
+int
+netbsd_handle_transfer_completion(struct usbi_transfer *itransfer)
+{
+	return usbi_handle_transfer_completion(itransfer, LIBUSB_TRANSFER_COMPLETED);
+}
+
+int
+netbsd_clock_gettime(int clkid, struct timespec *tp)
+{
+	usbi_dbg("clock %d", clkid);
+
+	if (clkid == USBI_CLOCK_REALTIME)
+		return clock_gettime(CLOCK_REALTIME, tp);
+
+	if (clkid == USBI_CLOCK_MONOTONIC)
+		return clock_gettime(CLOCK_MONOTONIC, tp);
+
+	return (LIBUSB_ERROR_INVALID_PARAM);
+}
+
+int
+_errno_to_libusb(int err)
+{
+	switch (err) {
+	case EIO:
+		return (LIBUSB_ERROR_IO);
+	case EACCES:
+		return (LIBUSB_ERROR_ACCESS);
+	case ENOENT:
+		return (LIBUSB_ERROR_NO_DEVICE);
+	case ENOMEM:
+		return (LIBUSB_ERROR_NO_MEM);
+	}
+
+	usbi_dbg("error: %s", strerror(err));
+
+	return (LIBUSB_ERROR_OTHER);
+}
+
+int
+_cache_active_config_descriptor(struct libusb_device *dev, int fd)
+{
+	struct device_priv *dpriv = (struct device_priv *)dev->os_priv;
+	struct usb_config_desc ucd;
+	struct usb_full_desc ufd;
+	unsigned char* buf;
+	int len;
+
+	usbi_dbg("fd %d", fd);
+
+	ucd.ucd_config_index = USB_CURRENT_CONFIG_INDEX;
+
+	if ((ioctl(fd, USB_GET_CONFIG_DESC, &ucd)) < 0)
+		return _errno_to_libusb(errno);
+
+	usbi_dbg("active bLength %d", ucd.ucd_desc.bLength);
+
+	len = UGETW(ucd.ucd_desc.wTotalLength);
+	buf = malloc(len);
+	if (buf == NULL)
+		return (LIBUSB_ERROR_NO_MEM);
+
+	ufd.ufd_config_index = ucd.ucd_config_index;
+	ufd.ufd_size = len;
+	ufd.ufd_data = buf;
+
+	usbi_dbg("index %d, len %d", ufd.ufd_config_index, len);
+
+	if ((ioctl(fd, USB_GET_FULL_DESC, &ufd)) < 0) {
+		free(buf);
+		return _errno_to_libusb(errno);
+	}
+
+	if (dpriv->cdesc)
+		free(dpriv->cdesc);
+	dpriv->cdesc = buf;
+
+	return (0);
+}
+
+int
+_sync_control_transfer(struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer;
+	struct libusb_control_setup *setup;
+	struct device_priv *dpriv;
+	struct usb_ctl_request req;
+
+	transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	dpriv = (struct device_priv *)transfer->dev_handle->dev->os_priv;
+	setup = (struct libusb_control_setup *)transfer->buffer;
+
+	usbi_dbg("type %d request %d value %d index %d length %d timeout %d",
+	    setup->bmRequestType, setup->bRequest,
+	    libusb_le16_to_cpu(setup->wValue),
+	    libusb_le16_to_cpu(setup->wIndex),
+	    libusb_le16_to_cpu(setup->wLength), transfer->timeout);
+
+	req.ucr_request.bmRequestType = setup->bmRequestType;
+	req.ucr_request.bRequest = setup->bRequest;
+	/* Don't use USETW, libusb already deals with the endianness */
+	(*(uint16_t *)req.ucr_request.wValue) = setup->wValue;
+	(*(uint16_t *)req.ucr_request.wIndex) = setup->wIndex;
+	(*(uint16_t *)req.ucr_request.wLength) = setup->wLength;
+	req.ucr_data = transfer->buffer + LIBUSB_CONTROL_SETUP_SIZE;
+
+	if ((transfer->flags & LIBUSB_TRANSFER_SHORT_NOT_OK) == 0)
+		req.ucr_flags = USBD_SHORT_XFER_OK;
+
+	if ((ioctl(dpriv->fd, USB_SET_TIMEOUT, &transfer->timeout)) < 0)
+		return _errno_to_libusb(errno);
+
+	if ((ioctl(dpriv->fd, USB_DO_REQUEST, &req)) < 0)
+		return _errno_to_libusb(errno);
+
+	itransfer->transferred = req.ucr_actlen;
+
+	usbi_dbg("transferred %d", itransfer->transferred);
+
+	return (0);
+}
+
+int
+_access_endpoint(struct libusb_transfer *transfer)
+{
+	struct handle_priv *hpriv;
+	struct device_priv *dpriv;
+	char *s, devnode[16];
+	int fd, endpt;
+	mode_t mode;
+
+	hpriv = (struct handle_priv *)transfer->dev_handle->os_priv;
+	dpriv = (struct device_priv *)transfer->dev_handle->dev->os_priv;
+
+	endpt = UE_GET_ADDR(transfer->endpoint);
+	mode = IS_XFERIN(transfer) ? O_RDONLY : O_WRONLY;
+
+	usbi_dbg("endpoint %d mode %d", endpt, mode);
+
+	if (hpriv->endpoints[endpt] < 0) {
+		/* Pick the right node given the control one */
+		strlcpy(devnode, dpriv->devnode, sizeof(devnode));
+		s = strchr(devnode, '.');
+		snprintf(s, 4, ".%02d", endpt);
+
+		/* We may need to read/write to the same endpoint later. */
+		if (((fd = open(devnode, O_RDWR)) < 0) && (errno == ENXIO))
+			if ((fd = open(devnode, mode)) < 0)
+				return (-1);
+
+		hpriv->endpoints[endpt] = fd;
+	}
+
+	return (hpriv->endpoints[endpt]);
+}
+
+int
+_sync_gen_transfer(struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer;
+	int fd, nr = 1;
+
+	transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+
+	/*
+	 * Bulk, Interrupt or Isochronous transfer depends on the
+	 * endpoint and thus the node to open.
+	 */
+	if ((fd = _access_endpoint(transfer)) < 0)
+		return _errno_to_libusb(errno);
+
+	if ((ioctl(fd, USB_SET_TIMEOUT, &transfer->timeout)) < 0)
+		return _errno_to_libusb(errno);
+
+	if (IS_XFERIN(transfer)) {
+		if ((transfer->flags & LIBUSB_TRANSFER_SHORT_NOT_OK) == 0)
+			if ((ioctl(fd, USB_SET_SHORT_XFER, &nr)) < 0)
+				return _errno_to_libusb(errno);
+
+		nr = read(fd, transfer->buffer, transfer->length);
+	} else {
+		nr = write(fd, transfer->buffer, transfer->length);
+	}
+
+	if (nr < 0)
+		return _errno_to_libusb(errno);
+
+	itransfer->transferred = nr;
+
+	return (0);
+}
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/openbsd_usb.c b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/openbsd_usb.c
new file mode 100644
index 000000000..c66025711
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/openbsd_usb.c
@@ -0,0 +1,771 @@
+/*
+ * Copyright © 2011-2013 Martin Pieuchot <mpi@openbsd.org>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <config.h>
+
+#include <sys/time.h>
+#include <sys/types.h>
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <dev/usb/usb.h>
+
+#include "libusbi.h"
+
+struct device_priv {
+	char *devname;				/* name of the ugen(4) node */
+	int fd;					/* device file descriptor */
+
+	unsigned char *cdesc;			/* active config descriptor */
+	usb_device_descriptor_t ddesc;		/* usb device descriptor */
+};
+
+struct handle_priv {
+	int endpoints[USB_MAX_ENDPOINTS];
+};
+
+/*
+ * Backend functions
+ */
+static int obsd_get_device_list(struct libusb_context *,
+    struct discovered_devs **);
+static int obsd_open(struct libusb_device_handle *);
+static void obsd_close(struct libusb_device_handle *);
+
+static int obsd_get_device_descriptor(struct libusb_device *, unsigned char *,
+    int *);
+static int obsd_get_active_config_descriptor(struct libusb_device *,
+    unsigned char *, size_t, int *);
+static int obsd_get_config_descriptor(struct libusb_device *, uint8_t,
+    unsigned char *, size_t, int *);
+
+static int obsd_get_configuration(struct libusb_device_handle *, int *);
+static int obsd_set_configuration(struct libusb_device_handle *, int);
+
+static int obsd_claim_interface(struct libusb_device_handle *, int);
+static int obsd_release_interface(struct libusb_device_handle *, int);
+
+static int obsd_set_interface_altsetting(struct libusb_device_handle *, int,
+    int);
+static int obsd_clear_halt(struct libusb_device_handle *, unsigned char);
+static int obsd_reset_device(struct libusb_device_handle *);
+static void obsd_destroy_device(struct libusb_device *);
+
+static int obsd_submit_transfer(struct usbi_transfer *);
+static int obsd_cancel_transfer(struct usbi_transfer *);
+static void obsd_clear_transfer_priv(struct usbi_transfer *);
+static int obsd_handle_transfer_completion(struct usbi_transfer *);
+static int obsd_clock_gettime(int, struct timespec *);
+
+/*
+ * Private functions
+ */
+static int _errno_to_libusb(int);
+static int _cache_active_config_descriptor(struct libusb_device *);
+static int _sync_control_transfer(struct usbi_transfer *);
+static int _sync_gen_transfer(struct usbi_transfer *);
+static int _access_endpoint(struct libusb_transfer *);
+
+static int _bus_open(int);
+
+
+const struct usbi_os_backend openbsd_backend = {
+	"Synchronous OpenBSD backend",
+	0,
+	NULL,				/* init() */
+	NULL,				/* exit() */
+	obsd_get_device_list,
+	NULL,				/* hotplug_poll */
+	obsd_open,
+	obsd_close,
+
+	obsd_get_device_descriptor,
+	obsd_get_active_config_descriptor,
+	obsd_get_config_descriptor,
+	NULL,				/* get_config_descriptor_by_value() */
+
+	obsd_get_configuration,
+	obsd_set_configuration,
+
+	obsd_claim_interface,
+	obsd_release_interface,
+
+	obsd_set_interface_altsetting,
+	obsd_clear_halt,
+	obsd_reset_device,
+
+	NULL,				/* alloc_streams */
+	NULL,				/* free_streams */
+
+	NULL,				/* dev_mem_alloc() */
+	NULL,				/* dev_mem_free() */
+
+	NULL,				/* kernel_driver_active() */
+	NULL,				/* detach_kernel_driver() */
+	NULL,				/* attach_kernel_driver() */
+
+	obsd_destroy_device,
+
+	obsd_submit_transfer,
+	obsd_cancel_transfer,
+	obsd_clear_transfer_priv,
+
+	NULL,				/* handle_events() */
+	obsd_handle_transfer_completion,
+
+	obsd_clock_gettime,
+	sizeof(struct device_priv),
+	sizeof(struct handle_priv),
+	0,				/* transfer_priv_size */
+};
+
+#define DEVPATH	"/dev/"
+#define USBDEV	DEVPATH "usb"
+
+int
+obsd_get_device_list(struct libusb_context * ctx,
+	struct discovered_devs **discdevs)
+{
+	struct discovered_devs *ddd;
+	struct libusb_device *dev;
+	struct device_priv *dpriv;
+	struct usb_device_info di;
+	struct usb_device_ddesc dd;
+	unsigned long session_id;
+	char devices[USB_MAX_DEVICES];
+	char busnode[16];
+	char *udevname;
+	int fd, addr, i, j;
+
+	usbi_dbg("");
+
+	for (i = 0; i < 8; i++) {
+		snprintf(busnode, sizeof(busnode), USBDEV "%d", i);
+
+		if ((fd = open(busnode, O_RDWR)) < 0) {
+			if (errno != ENOENT && errno != ENXIO)
+				usbi_err(ctx, "could not open %s", busnode);
+			continue;
+		}
+
+		bzero(devices, sizeof(devices));
+		for (addr = 1; addr < USB_MAX_DEVICES; addr++) {
+			if (devices[addr])
+				continue;
+
+			di.udi_addr = addr;
+			if (ioctl(fd, USB_DEVICEINFO, &di) < 0)
+				continue;
+
+			/*
+			 * XXX If ugen(4) is attached to the USB device
+			 * it will be used.
+			 */
+			udevname = NULL;
+			for (j = 0; j < USB_MAX_DEVNAMES; j++)
+				if (!strncmp("ugen", di.udi_devnames[j], 4)) {
+					udevname = strdup(di.udi_devnames[j]);
+					break;
+				}
+
+			session_id = (di.udi_bus << 8 | di.udi_addr);
+			dev = usbi_get_device_by_session_id(ctx, session_id);
+
+			if (dev == NULL) {
+				dev = usbi_alloc_device(ctx, session_id);
+				if (dev == NULL) {
+					close(fd);
+					return (LIBUSB_ERROR_NO_MEM);
+				}
+
+				dev->bus_number = di.udi_bus;
+				dev->device_address = di.udi_addr;
+				dev->speed = di.udi_speed;
+
+				dpriv = (struct device_priv *)dev->os_priv;
+				dpriv->fd = -1;
+				dpriv->cdesc = NULL;
+				dpriv->devname = udevname;
+
+				dd.udd_bus = di.udi_bus;
+				dd.udd_addr = di.udi_addr;
+				if (ioctl(fd, USB_DEVICE_GET_DDESC, &dd) < 0) {
+					libusb_unref_device(dev);
+					continue;
+				}
+				dpriv->ddesc = dd.udd_desc;
+
+				if (_cache_active_config_descriptor(dev)) {
+					libusb_unref_device(dev);
+					continue;
+				}
+
+				if (usbi_sanitize_device(dev)) {
+					libusb_unref_device(dev);
+					continue;
+				}
+			}
+
+			ddd = discovered_devs_append(*discdevs, dev);
+			if (ddd == NULL) {
+				close(fd);
+				return (LIBUSB_ERROR_NO_MEM);
+			}
+			libusb_unref_device(dev);
+
+			*discdevs = ddd;
+			devices[addr] = 1;
+		}
+
+		close(fd);
+	}
+
+	return (LIBUSB_SUCCESS);
+}
+
+int
+obsd_open(struct libusb_device_handle *handle)
+{
+	struct handle_priv *hpriv = (struct handle_priv *)handle->os_priv;
+	struct device_priv *dpriv = (struct device_priv *)handle->dev->os_priv;
+	char devnode[16];
+
+	if (dpriv->devname) {
+		/*
+		 * Only open ugen(4) attached devices read-write, all
+		 * read-only operations are done through the bus node.
+		 */
+		snprintf(devnode, sizeof(devnode), DEVPATH "%s.00",
+		    dpriv->devname);
+		dpriv->fd = open(devnode, O_RDWR);
+		if (dpriv->fd < 0)
+			return _errno_to_libusb(errno);
+
+		usbi_dbg("open %s: fd %d", devnode, dpriv->fd);
+	}
+
+	return (LIBUSB_SUCCESS);
+}
+
+void
+obsd_close(struct libusb_device_handle *handle)
+{
+	struct handle_priv *hpriv = (struct handle_priv *)handle->os_priv;
+	struct device_priv *dpriv = (struct device_priv *)handle->dev->os_priv;
+
+	if (dpriv->devname) {
+		usbi_dbg("close: fd %d", dpriv->fd);
+
+		close(dpriv->fd);
+		dpriv->fd = -1;
+	}
+}
+
+int
+obsd_get_device_descriptor(struct libusb_device *dev, unsigned char *buf,
+    int *host_endian)
+{
+	struct device_priv *dpriv = (struct device_priv *)dev->os_priv;
+
+	usbi_dbg("");
+
+	memcpy(buf, &dpriv->ddesc, DEVICE_DESC_LENGTH);
+
+	*host_endian = 0;
+
+	return (LIBUSB_SUCCESS);
+}
+
+int
+obsd_get_active_config_descriptor(struct libusb_device *dev,
+    unsigned char *buf, size_t len, int *host_endian)
+{
+	struct device_priv *dpriv = (struct device_priv *)dev->os_priv;
+	usb_config_descriptor_t *ucd = (usb_config_descriptor_t *)dpriv->cdesc;
+
+	len = MIN(len, UGETW(ucd->wTotalLength));
+
+	usbi_dbg("len %d", len);
+
+	memcpy(buf, dpriv->cdesc, len);
+
+	*host_endian = 0;
+
+	return (len);
+}
+
+int
+obsd_get_config_descriptor(struct libusb_device *dev, uint8_t idx,
+    unsigned char *buf, size_t len, int *host_endian)
+{
+	struct usb_device_fdesc udf;
+	int fd, err;
+
+	if ((fd = _bus_open(dev->bus_number)) < 0)
+		return _errno_to_libusb(errno);
+
+	udf.udf_bus = dev->bus_number;
+	udf.udf_addr = dev->device_address;
+	udf.udf_config_index = idx;
+	udf.udf_size = len;
+	udf.udf_data = buf;
+
+	usbi_dbg("index %d, len %d", udf.udf_config_index, len);
+
+	if (ioctl(fd, USB_DEVICE_GET_FDESC, &udf) < 0) {
+		err = errno;
+		close(fd);
+		return _errno_to_libusb(err);
+	}
+	close(fd);
+
+	*host_endian = 0;
+
+	return (len);
+}
+
+int
+obsd_get_configuration(struct libusb_device_handle *handle, int *config)
+{
+	struct device_priv *dpriv = (struct device_priv *)handle->dev->os_priv;
+	usb_config_descriptor_t *ucd = (usb_config_descriptor_t *)dpriv->cdesc;
+
+	*config = ucd->bConfigurationValue;
+
+	usbi_dbg("bConfigurationValue %d", *config);
+
+	return (LIBUSB_SUCCESS);
+}
+
+int
+obsd_set_configuration(struct libusb_device_handle *handle, int config)
+{
+	struct device_priv *dpriv = (struct device_priv *)handle->dev->os_priv;
+
+	if (dpriv->devname == NULL)
+		return (LIBUSB_ERROR_NOT_SUPPORTED);
+
+	usbi_dbg("bConfigurationValue %d", config);
+
+	if (ioctl(dpriv->fd, USB_SET_CONFIG, &config) < 0)
+		return _errno_to_libusb(errno);
+
+	return _cache_active_config_descriptor(handle->dev);
+}
+
+int
+obsd_claim_interface(struct libusb_device_handle *handle, int iface)
+{
+	struct handle_priv *hpriv = (struct handle_priv *)handle->os_priv;
+	int i;
+
+	for (i = 0; i < USB_MAX_ENDPOINTS; i++)
+		hpriv->endpoints[i] = -1;
+
+	return (LIBUSB_SUCCESS);
+}
+
+int
+obsd_release_interface(struct libusb_device_handle *handle, int iface)
+{
+	struct handle_priv *hpriv = (struct handle_priv *)handle->os_priv;
+	int i;
+
+	for (i = 0; i < USB_MAX_ENDPOINTS; i++)
+		if (hpriv->endpoints[i] >= 0)
+			close(hpriv->endpoints[i]);
+
+	return (LIBUSB_SUCCESS);
+}
+
+int
+obsd_set_interface_altsetting(struct libusb_device_handle *handle, int iface,
+    int altsetting)
+{
+	struct device_priv *dpriv = (struct device_priv *)handle->dev->os_priv;
+	struct usb_alt_interface intf;
+
+	if (dpriv->devname == NULL)
+		return (LIBUSB_ERROR_NOT_SUPPORTED);
+
+	usbi_dbg("iface %d, setting %d", iface, altsetting);
+
+	memset(&intf, 0, sizeof(intf));
+
+	intf.uai_interface_index = iface;
+	intf.uai_alt_no = altsetting;
+
+	if (ioctl(dpriv->fd, USB_SET_ALTINTERFACE, &intf) < 0)
+		return _errno_to_libusb(errno);
+
+	return (LIBUSB_SUCCESS);
+}
+
+int
+obsd_clear_halt(struct libusb_device_handle *handle, unsigned char endpoint)
+{
+	struct usb_ctl_request req;
+	int fd, err;
+
+	if ((fd = _bus_open(handle->dev->bus_number)) < 0)
+		return _errno_to_libusb(errno);
+
+	usbi_dbg("");
+
+	req.ucr_addr = handle->dev->device_address;
+	req.ucr_request.bmRequestType = UT_WRITE_ENDPOINT;
+	req.ucr_request.bRequest = UR_CLEAR_FEATURE;
+	USETW(req.ucr_request.wValue, UF_ENDPOINT_HALT);
+	USETW(req.ucr_request.wIndex, endpoint);
+	USETW(req.ucr_request.wLength, 0);
+
+	if (ioctl(fd, USB_REQUEST, &req) < 0) {
+		err = errno;
+		close(fd);
+		return _errno_to_libusb(err);
+	}
+	close(fd);
+
+	return (LIBUSB_SUCCESS);
+}
+
+int
+obsd_reset_device(struct libusb_device_handle *handle)
+{
+	usbi_dbg("");
+
+	return (LIBUSB_ERROR_NOT_SUPPORTED);
+}
+
+void
+obsd_destroy_device(struct libusb_device *dev)
+{
+	struct device_priv *dpriv = (struct device_priv *)dev->os_priv;
+
+	usbi_dbg("");
+
+	free(dpriv->cdesc);
+	free(dpriv->devname);
+}
+
+int
+obsd_submit_transfer(struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer;
+	struct handle_priv *hpriv;
+	int err = 0;
+
+	usbi_dbg("");
+
+	transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	hpriv = (struct handle_priv *)transfer->dev_handle->os_priv;
+
+	switch (transfer->type) {
+	case LIBUSB_TRANSFER_TYPE_CONTROL:
+		err = _sync_control_transfer(itransfer);
+		break;
+	case LIBUSB_TRANSFER_TYPE_ISOCHRONOUS:
+		if (IS_XFEROUT(transfer)) {
+			/* Isochronous write is not supported */
+			err = LIBUSB_ERROR_NOT_SUPPORTED;
+			break;
+		}
+		err = _sync_gen_transfer(itransfer);
+		break;
+	case LIBUSB_TRANSFER_TYPE_BULK:
+	case LIBUSB_TRANSFER_TYPE_INTERRUPT:
+		if (IS_XFEROUT(transfer) &&
+		    transfer->flags & LIBUSB_TRANSFER_ADD_ZERO_PACKET) {
+			err = LIBUSB_ERROR_NOT_SUPPORTED;
+			break;
+		}
+		err = _sync_gen_transfer(itransfer);
+		break;
+	case LIBUSB_TRANSFER_TYPE_BULK_STREAM:
+		err = LIBUSB_ERROR_NOT_SUPPORTED;
+		break;
+	}
+
+	if (err)
+		return (err);
+
+	usbi_signal_transfer_completion(itransfer);
+
+	return (LIBUSB_SUCCESS);
+}
+
+int
+obsd_cancel_transfer(struct usbi_transfer *itransfer)
+{
+	usbi_dbg("");
+
+	return (LIBUSB_ERROR_NOT_SUPPORTED);
+}
+
+void
+obsd_clear_transfer_priv(struct usbi_transfer *itransfer)
+{
+	usbi_dbg("");
+
+	/* Nothing to do */
+}
+
+int
+obsd_handle_transfer_completion(struct usbi_transfer *itransfer)
+{
+	return usbi_handle_transfer_completion(itransfer, LIBUSB_TRANSFER_COMPLETED);
+}
+
+int
+obsd_clock_gettime(int clkid, struct timespec *tp)
+{
+	usbi_dbg("clock %d", clkid);
+
+	if (clkid == USBI_CLOCK_REALTIME)
+		return clock_gettime(CLOCK_REALTIME, tp);
+
+	if (clkid == USBI_CLOCK_MONOTONIC)
+		return clock_gettime(CLOCK_MONOTONIC, tp);
+
+	return (LIBUSB_ERROR_INVALID_PARAM);
+}
+
+int
+_errno_to_libusb(int err)
+{
+	usbi_dbg("error: %s (%d)", strerror(err), err);
+
+	switch (err) {
+	case EIO:
+		return (LIBUSB_ERROR_IO);
+	case EACCES:
+		return (LIBUSB_ERROR_ACCESS);
+	case ENOENT:
+		return (LIBUSB_ERROR_NO_DEVICE);
+	case ENOMEM:
+		return (LIBUSB_ERROR_NO_MEM);
+	case ETIMEDOUT:
+		return (LIBUSB_ERROR_TIMEOUT);
+	}
+
+	return (LIBUSB_ERROR_OTHER);
+}
+
+int
+_cache_active_config_descriptor(struct libusb_device *dev)
+{
+	struct device_priv *dpriv = (struct device_priv *)dev->os_priv;
+	struct usb_device_cdesc udc;
+	struct usb_device_fdesc udf;
+	unsigned char* buf;
+	int fd, len, err;
+
+	if ((fd = _bus_open(dev->bus_number)) < 0)
+		return _errno_to_libusb(errno);
+
+	usbi_dbg("fd %d, addr %d", fd, dev->device_address);
+
+	udc.udc_bus = dev->bus_number;
+	udc.udc_addr = dev->device_address;
+	udc.udc_config_index = USB_CURRENT_CONFIG_INDEX;
+	if (ioctl(fd, USB_DEVICE_GET_CDESC, &udc) < 0) {
+		err = errno;
+		close(fd);
+		return _errno_to_libusb(errno);
+	}
+
+	usbi_dbg("active bLength %d", udc.udc_desc.bLength);
+
+	len = UGETW(udc.udc_desc.wTotalLength);
+	buf = malloc(len);
+	if (buf == NULL)
+		return (LIBUSB_ERROR_NO_MEM);
+
+	udf.udf_bus = dev->bus_number;
+	udf.udf_addr = dev->device_address;
+	udf.udf_config_index = udc.udc_config_index;
+	udf.udf_size = len;
+	udf.udf_data = buf;
+
+	usbi_dbg("index %d, len %d", udf.udf_config_index, len);
+
+	if (ioctl(fd, USB_DEVICE_GET_FDESC, &udf) < 0) {
+		err = errno;
+		close(fd);
+		free(buf);
+		return _errno_to_libusb(err);
+	}
+	close(fd);
+
+	if (dpriv->cdesc)
+		free(dpriv->cdesc);
+	dpriv->cdesc = buf;
+
+	return (LIBUSB_SUCCESS);
+}
+
+int
+_sync_control_transfer(struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer;
+	struct libusb_control_setup *setup;
+	struct device_priv *dpriv;
+	struct usb_ctl_request req;
+
+	transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	dpriv = (struct device_priv *)transfer->dev_handle->dev->os_priv;
+	setup = (struct libusb_control_setup *)transfer->buffer;
+
+	usbi_dbg("type %x request %x value %x index %d length %d timeout %d",
+	    setup->bmRequestType, setup->bRequest,
+	    libusb_le16_to_cpu(setup->wValue),
+	    libusb_le16_to_cpu(setup->wIndex),
+	    libusb_le16_to_cpu(setup->wLength), transfer->timeout);
+
+	req.ucr_addr = transfer->dev_handle->dev->device_address;
+	req.ucr_request.bmRequestType = setup->bmRequestType;
+	req.ucr_request.bRequest = setup->bRequest;
+	/* Don't use USETW, libusb already deals with the endianness */
+	(*(uint16_t *)req.ucr_request.wValue) = setup->wValue;
+	(*(uint16_t *)req.ucr_request.wIndex) = setup->wIndex;
+	(*(uint16_t *)req.ucr_request.wLength) = setup->wLength;
+	req.ucr_data = transfer->buffer + LIBUSB_CONTROL_SETUP_SIZE;
+
+	if ((transfer->flags & LIBUSB_TRANSFER_SHORT_NOT_OK) == 0)
+		req.ucr_flags = USBD_SHORT_XFER_OK;
+
+	if (dpriv->devname == NULL) {
+		/*
+		 * XXX If the device is not attached to ugen(4) it is
+		 * XXX still possible to submit a control transfer but
+		 * XXX with the default timeout only.
+		 */
+		int fd, err;
+
+		if ((fd = _bus_open(transfer->dev_handle->dev->bus_number)) < 0)
+			return _errno_to_libusb(errno);
+
+		if ((ioctl(fd, USB_REQUEST, &req)) < 0) {
+			err = errno;
+			close(fd);
+			return _errno_to_libusb(err);
+		}
+		close(fd);
+	} else {
+		if ((ioctl(dpriv->fd, USB_SET_TIMEOUT, &transfer->timeout)) < 0)
+			return _errno_to_libusb(errno);
+
+		if ((ioctl(dpriv->fd, USB_DO_REQUEST, &req)) < 0)
+			return _errno_to_libusb(errno);
+	}
+
+	itransfer->transferred = req.ucr_actlen;
+
+	usbi_dbg("transferred %d", itransfer->transferred);
+
+	return (0);
+}
+
+int
+_access_endpoint(struct libusb_transfer *transfer)
+{
+	struct handle_priv *hpriv;
+	struct device_priv *dpriv;
+	char devnode[16];
+	int fd, endpt;
+	mode_t mode;
+
+	hpriv = (struct handle_priv *)transfer->dev_handle->os_priv;
+	dpriv = (struct device_priv *)transfer->dev_handle->dev->os_priv;
+
+	endpt = UE_GET_ADDR(transfer->endpoint);
+	mode = IS_XFERIN(transfer) ? O_RDONLY : O_WRONLY;
+
+	usbi_dbg("endpoint %d mode %d", endpt, mode);
+
+	if (hpriv->endpoints[endpt] < 0) {
+		/* Pick the right endpoint node */
+		snprintf(devnode, sizeof(devnode), DEVPATH "%s.%02d",
+		    dpriv->devname, endpt);
+
+		/* We may need to read/write to the same endpoint later. */
+		if (((fd = open(devnode, O_RDWR)) < 0) && (errno == ENXIO))
+			if ((fd = open(devnode, mode)) < 0)
+				return (-1);
+
+		hpriv->endpoints[endpt] = fd;
+	}
+
+	return (hpriv->endpoints[endpt]);
+}
+
+int
+_sync_gen_transfer(struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer;
+	struct device_priv *dpriv;
+	int fd, nr = 1;
+
+	transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	dpriv = (struct device_priv *)transfer->dev_handle->dev->os_priv;
+
+	if (dpriv->devname == NULL)
+		return (LIBUSB_ERROR_NOT_SUPPORTED);
+
+	/*
+	 * Bulk, Interrupt or Isochronous transfer depends on the
+	 * endpoint and thus the node to open.
+	 */
+	if ((fd = _access_endpoint(transfer)) < 0)
+		return _errno_to_libusb(errno);
+
+	if ((ioctl(fd, USB_SET_TIMEOUT, &transfer->timeout)) < 0)
+		return _errno_to_libusb(errno);
+
+	if (IS_XFERIN(transfer)) {
+		if ((transfer->flags & LIBUSB_TRANSFER_SHORT_NOT_OK) == 0)
+			if ((ioctl(fd, USB_SET_SHORT_XFER, &nr)) < 0)
+				return _errno_to_libusb(errno);
+
+		nr = read(fd, transfer->buffer, transfer->length);
+	} else {
+		nr = write(fd, transfer->buffer, transfer->length);
+	}
+
+	if (nr < 0)
+		return _errno_to_libusb(errno);
+
+	itransfer->transferred = nr;
+
+	return (0);
+}
+
+int
+_bus_open(int number)
+{
+	char busnode[16];
+
+	snprintf(busnode, sizeof(busnode), USBDEV "%d", number);
+
+	return open(busnode, O_RDWR);
+}
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/poll_posix.c b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/poll_posix.c
new file mode 100644
index 000000000..e2f55a57a
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/poll_posix.c
@@ -0,0 +1,53 @@
+/*
+ * poll_posix: poll compatibility wrapper for POSIX systems
+ * Copyright © 2013 RealVNC Ltd.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ *
+ */
+
+#include <config.h>
+
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <stdlib.h>
+
+#include "libusbi.h"
+
+int usbi_pipe(int pipefd[2])
+{
+	int ret = pipe(pipefd);
+	if (ret != 0) {
+		return ret;
+	}
+	ret = fcntl(pipefd[1], F_GETFL);
+	if (ret == -1) {
+		usbi_dbg("Failed to get pipe fd flags: %d", errno);
+		goto err_close_pipe;
+	}
+	ret = fcntl(pipefd[1], F_SETFL, ret | O_NONBLOCK);
+	if (ret != 0) {
+		usbi_dbg("Failed to set non-blocking on new pipe: %d", errno);
+		goto err_close_pipe;
+	}
+
+	return 0;
+
+err_close_pipe:
+	usbi_close(pipefd[0]);
+	usbi_close(pipefd[1]);
+	return ret;
+}
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/poll_posix.h b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/poll_posix.h
new file mode 100644
index 000000000..5b4b2c905
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/poll_posix.h
@@ -0,0 +1,11 @@
+#ifndef LIBUSB_POLL_POSIX_H
+#define LIBUSB_POLL_POSIX_H
+
+#define usbi_write write
+#define usbi_read read
+#define usbi_close close
+#define usbi_poll poll
+
+int usbi_pipe(int pipefd[2]);
+
+#endif /* LIBUSB_POLL_POSIX_H */
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/poll_windows.c b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/poll_windows.c
new file mode 100644
index 000000000..982560751
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/poll_windows.c
@@ -0,0 +1,728 @@
+/*
+ * poll_windows: poll compatibility wrapper for Windows
+ * Copyright © 2012-2013 RealVNC Ltd.
+ * Copyright © 2009-2010 Pete Batard <pete@akeo.ie>
+ * With contributions from Michael Plante, Orin Eman et al.
+ * Parts of poll implementation from libusb-win32, by Stephan Meyer et al.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ *
+ */
+
+/*
+ * poll() and pipe() Windows compatibility layer for libusb 1.0
+ *
+ * The way this layer works is by using OVERLAPPED with async I/O transfers, as
+ * OVERLAPPED have an associated event which is flagged for I/O completion.
+ *
+ * For USB pollable async I/O, you would typically:
+ * - obtain a Windows HANDLE to a file or device that has been opened in
+ *   OVERLAPPED mode
+ * - call usbi_create_fd with this handle to obtain a custom fd.
+ *   Note that if you need simultaneous R/W access, you need to call create_fd
+ *   twice, once in RW_READ and once in RW_WRITE mode to obtain 2 separate
+ *   pollable fds
+ * - leave the core functions call the poll routine and flag POLLIN/POLLOUT
+ *
+ * The pipe pollable synchronous I/O works using the overlapped event associated
+ * with a fake pipe. The read/write functions are only meant to be used in that
+ * context.
+ */
+#include <config.h>
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "libusbi.h"
+
+// Uncomment to debug the polling layer
+//#define DEBUG_POLL_WINDOWS
+#if defined(DEBUG_POLL_WINDOWS)
+#define poll_dbg usbi_dbg
+#else
+// MSVC++ < 2005 cannot use a variadic argument and non MSVC
+// compilers produce warnings if parenthesis are omitted.
+#if defined(_MSC_VER) && (_MSC_VER < 1400)
+#define poll_dbg
+#else
+#define poll_dbg(...)
+#endif
+#endif
+
+#if defined(_PREFAST_)
+#pragma warning(disable:28719)
+#endif
+
+#define CHECK_INIT_POLLING do {if(!is_polling_set) init_polling();} while(0)
+
+// public fd data
+const struct winfd INVALID_WINFD = {-1, INVALID_HANDLE_VALUE, NULL, NULL, NULL, RW_NONE};
+struct winfd poll_fd[MAX_FDS];
+// internal fd data
+struct {
+	CRITICAL_SECTION mutex; // lock for fds
+	// Additional variables for XP CancelIoEx partial emulation
+	HANDLE original_handle;
+	DWORD thread_id;
+} _poll_fd[MAX_FDS];
+
+// globals
+BOOLEAN is_polling_set = FALSE;
+LONG pipe_number = 0;
+static volatile LONG compat_spinlock = 0;
+
+#if !defined(_WIN32_WCE)
+// CancelIoEx, available on Vista and later only, provides the ability to cancel
+// a single transfer (OVERLAPPED) when used. As it may not be part of any of the
+// platform headers, we hook into the Kernel32 system DLL directly to seek it.
+static BOOL (__stdcall *pCancelIoEx)(HANDLE, LPOVERLAPPED) = NULL;
+#define Use_Duplicate_Handles (pCancelIoEx == NULL)
+
+static inline void setup_cancel_io(void)
+{
+	HMODULE hKernel32 = GetModuleHandleA("KERNEL32");
+	if (hKernel32 != NULL) {
+		pCancelIoEx = (BOOL (__stdcall *)(HANDLE,LPOVERLAPPED))
+			GetProcAddress(hKernel32, "CancelIoEx");
+	}
+	usbi_dbg("Will use CancelIo%s for I/O cancellation",
+		Use_Duplicate_Handles?"":"Ex");
+}
+
+static inline BOOL cancel_io(int _index)
+{
+	if ((_index < 0) || (_index >= MAX_FDS)) {
+		return FALSE;
+	}
+
+	if ( (poll_fd[_index].fd < 0) || (poll_fd[_index].handle == INVALID_HANDLE_VALUE)
+	  || (poll_fd[_index].handle == 0) || (poll_fd[_index].overlapped == NULL) ) {
+		return TRUE;
+	}
+	if (poll_fd[_index].itransfer && poll_fd[_index].cancel_fn) {
+		// Cancel outstanding transfer via the specific callback
+		(*poll_fd[_index].cancel_fn)(poll_fd[_index].itransfer);
+		return TRUE;
+	}
+	if (pCancelIoEx != NULL) {
+		return (*pCancelIoEx)(poll_fd[_index].handle, poll_fd[_index].overlapped);
+	}
+	if (_poll_fd[_index].thread_id == GetCurrentThreadId()) {
+		return CancelIo(poll_fd[_index].handle);
+	}
+	usbi_warn(NULL, "Unable to cancel I/O that was started from another thread");
+	return FALSE;
+}
+#else
+#define Use_Duplicate_Handles FALSE
+
+static __inline void setup_cancel_io()
+{
+	// No setup needed on WinCE
+}
+
+static __inline BOOL cancel_io(int _index)
+{
+	if ((_index < 0) || (_index >= MAX_FDS)) {
+		return FALSE;
+	}
+	if ( (poll_fd[_index].fd < 0) || (poll_fd[_index].handle == INVALID_HANDLE_VALUE)
+	  || (poll_fd[_index].handle == 0) || (poll_fd[_index].overlapped == NULL) ) {
+		return TRUE;
+	}
+	if (poll_fd[_index].itransfer && poll_fd[_index].cancel_fn) {
+		// Cancel outstanding transfer via the specific callback
+		(*poll_fd[_index].cancel_fn)(poll_fd[_index].itransfer);
+	}
+	return TRUE;
+}
+#endif
+
+// Init
+void init_polling(void)
+{
+	int i;
+
+	while (InterlockedExchange((LONG *)&compat_spinlock, 1) == 1) {
+		SleepEx(0, TRUE);
+	}
+	if (!is_polling_set) {
+		setup_cancel_io();
+		for (i=0; i<MAX_FDS; i++) {
+			poll_fd[i] = INVALID_WINFD;
+			_poll_fd[i].original_handle = INVALID_HANDLE_VALUE;
+			_poll_fd[i].thread_id = 0;
+			InitializeCriticalSection(&_poll_fd[i].mutex);
+		}
+		is_polling_set = TRUE;
+	}
+	InterlockedExchange((LONG *)&compat_spinlock, 0);
+}
+
+// Internal function to retrieve the table index (and lock the fd mutex)
+static int _fd_to_index_and_lock(int fd)
+{
+	int i;
+
+	if (fd < 0)
+		return -1;
+
+	for (i=0; i<MAX_FDS; i++) {
+		if (poll_fd[i].fd == fd) {
+			EnterCriticalSection(&_poll_fd[i].mutex);
+			// fd might have changed before we got to critical
+			if (poll_fd[i].fd != fd) {
+				LeaveCriticalSection(&_poll_fd[i].mutex);
+				continue;
+			}
+			return i;
+		}
+	}
+	return -1;
+}
+
+static OVERLAPPED *create_overlapped(void)
+{
+	OVERLAPPED *overlapped = (OVERLAPPED*) calloc(1, sizeof(OVERLAPPED));
+	if (overlapped == NULL) {
+		return NULL;
+	}
+	overlapped->hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
+	if(overlapped->hEvent == NULL) {
+		free (overlapped);
+		return NULL;
+	}
+	return overlapped;
+}
+
+static void free_overlapped(OVERLAPPED *overlapped)
+{
+	if (overlapped == NULL)
+		return;
+
+	if ( (overlapped->hEvent != 0)
+	  && (overlapped->hEvent != INVALID_HANDLE_VALUE) ) {
+		CloseHandle(overlapped->hEvent);
+	}
+	free(overlapped);
+}
+
+void exit_polling(void)
+{
+	int i;
+
+	while (InterlockedExchange((LONG *)&compat_spinlock, 1) == 1) {
+		SleepEx(0, TRUE);
+	}
+	if (is_polling_set) {
+		is_polling_set = FALSE;
+
+		for (i=0; i<MAX_FDS; i++) {
+			// Cancel any async I/O (handle can be invalid)
+			cancel_io(i);
+			// If anything was pending on that I/O, it should be
+			// terminating, and we should be able to access the fd
+			// mutex lock before too long
+			EnterCriticalSection(&_poll_fd[i].mutex);
+			free_overlapped(poll_fd[i].overlapped);
+			if (Use_Duplicate_Handles) {
+				// Close duplicate handle
+				if (_poll_fd[i].original_handle != INVALID_HANDLE_VALUE) {
+					CloseHandle(poll_fd[i].handle);
+				}
+			}
+			poll_fd[i] = INVALID_WINFD;
+			LeaveCriticalSection(&_poll_fd[i].mutex);
+			DeleteCriticalSection(&_poll_fd[i].mutex);
+		}
+	}
+	InterlockedExchange((LONG *)&compat_spinlock, 0);
+}
+
+/*
+ * Create a fake pipe.
+ * As libusb only uses pipes for signaling, all we need from a pipe is an
+ * event. To that extent, we create a single wfd and overlapped as a means
+ * to access that event.
+ */
+int usbi_pipe(int filedes[2])
+{
+	int i;
+	OVERLAPPED* overlapped;
+
+	CHECK_INIT_POLLING;
+
+	overlapped = create_overlapped();
+
+	if (overlapped == NULL) {
+		return -1;
+	}
+	// The overlapped must have status pending for signaling to work in poll
+	overlapped->Internal = STATUS_PENDING;
+	overlapped->InternalHigh = 0;
+
+	for (i=0; i<MAX_FDS; i++) {
+		if (poll_fd[i].fd < 0) {
+			EnterCriticalSection(&_poll_fd[i].mutex);
+			// fd might have been allocated before we got to critical
+			if (poll_fd[i].fd >= 0) {
+				LeaveCriticalSection(&_poll_fd[i].mutex);
+				continue;
+			}
+
+			// Use index as the unique fd number
+			poll_fd[i].fd = i;
+			// Read end of the "pipe"
+			filedes[0] = poll_fd[i].fd;
+			// We can use the same handle for both ends
+			filedes[1] = filedes[0];
+
+			poll_fd[i].handle = DUMMY_HANDLE;
+			poll_fd[i].overlapped = overlapped;
+			// There's no polling on the write end, so we just use READ for our needs
+			poll_fd[i].rw = RW_READ;
+			_poll_fd[i].original_handle = INVALID_HANDLE_VALUE;
+			LeaveCriticalSection(&_poll_fd[i].mutex);
+			return 0;
+		}
+	}
+	free_overlapped(overlapped);
+	return -1;
+}
+
+/*
+ * Create both an fd and an OVERLAPPED from an open Windows handle, so that
+ * it can be used with our polling function
+ * The handle MUST support overlapped transfers (usually requires CreateFile
+ * with FILE_FLAG_OVERLAPPED)
+ * Return a pollable file descriptor struct, or INVALID_WINFD on error
+ *
+ * Note that the fd returned by this function is a per-transfer fd, rather
+ * than a per-session fd and cannot be used for anything else but our
+ * custom functions (the fd itself points to the NUL: device)
+ * if you plan to do R/W on the same handle, you MUST create 2 fds: one for
+ * read and one for write. Using a single R/W fd is unsupported and will
+ * produce unexpected results
+ */
+struct winfd usbi_create_fd(HANDLE handle, int access_mode, struct usbi_transfer *itransfer, cancel_transfer *cancel_fn)
+{
+	int i;
+	struct winfd wfd = INVALID_WINFD;
+	OVERLAPPED* overlapped = NULL;
+
+	CHECK_INIT_POLLING;
+
+	if ((handle == 0) || (handle == INVALID_HANDLE_VALUE)) {
+		return INVALID_WINFD;
+	}
+
+	wfd.itransfer = itransfer;
+	wfd.cancel_fn = cancel_fn;
+
+	if ((access_mode != RW_READ) && (access_mode != RW_WRITE)) {
+		usbi_warn(NULL, "only one of RW_READ or RW_WRITE are supported. "
+			"If you want to poll for R/W simultaneously, create multiple fds from the same handle.");
+		return INVALID_WINFD;
+	}
+	if (access_mode == RW_READ) {
+		wfd.rw = RW_READ;
+	} else {
+		wfd.rw = RW_WRITE;
+	}
+
+	overlapped = create_overlapped();
+	if(overlapped == NULL) {
+		return INVALID_WINFD;
+	}
+
+	for (i=0; i<MAX_FDS; i++) {
+		if (poll_fd[i].fd < 0) {
+			EnterCriticalSection(&_poll_fd[i].mutex);
+			// fd might have been removed before we got to critical
+			if (poll_fd[i].fd >= 0) {
+				LeaveCriticalSection(&_poll_fd[i].mutex);
+				continue;
+			}
+			// Use index as the unique fd number
+			wfd.fd = i;
+			// Attempt to emulate some of the CancelIoEx behaviour on platforms
+			// that don't have it
+			if (Use_Duplicate_Handles) {
+				_poll_fd[i].thread_id = GetCurrentThreadId();
+				if (!DuplicateHandle(GetCurrentProcess(), handle, GetCurrentProcess(),
+					&wfd.handle, 0, TRUE, DUPLICATE_SAME_ACCESS)) {
+					usbi_dbg("could not duplicate handle for CancelIo - using original one");
+					wfd.handle = handle;
+					// Make sure we won't close the original handle on fd deletion then
+					_poll_fd[i].original_handle = INVALID_HANDLE_VALUE;
+				} else {
+					_poll_fd[i].original_handle = handle;
+				}
+			} else {
+				wfd.handle = handle;
+			}
+			wfd.overlapped = overlapped;
+			memcpy(&poll_fd[i], &wfd, sizeof(struct winfd));
+			LeaveCriticalSection(&_poll_fd[i].mutex);
+			return wfd;
+		}
+	}
+	free_overlapped(overlapped);
+	return INVALID_WINFD;
+}
+
+static void _free_index(int _index)
+{
+	// Cancel any async IO (Don't care about the validity of our handles for this)
+	cancel_io(_index);
+	// close the duplicate handle (if we have an actual duplicate)
+	if (Use_Duplicate_Handles) {
+		if (_poll_fd[_index].original_handle != INVALID_HANDLE_VALUE) {
+			CloseHandle(poll_fd[_index].handle);
+		}
+		_poll_fd[_index].original_handle = INVALID_HANDLE_VALUE;
+		_poll_fd[_index].thread_id = 0;
+	}
+	free_overlapped(poll_fd[_index].overlapped);
+	poll_fd[_index] = INVALID_WINFD;
+}
+
+/*
+ * Release a pollable file descriptor.
+ *
+ * Note that the associated Windows handle is not closed by this call
+ */
+void usbi_free_fd(struct winfd *wfd)
+{
+	int _index;
+
+	CHECK_INIT_POLLING;
+
+	_index = _fd_to_index_and_lock(wfd->fd);
+	if (_index < 0) {
+		return;
+	}
+	_free_index(_index);
+	*wfd = INVALID_WINFD;
+	LeaveCriticalSection(&_poll_fd[_index].mutex);
+}
+
+/*
+ * The functions below perform various conversions between fd, handle and OVERLAPPED
+ */
+struct winfd fd_to_winfd(int fd)
+{
+	int i;
+	struct winfd wfd;
+
+	CHECK_INIT_POLLING;
+
+	if (fd < 0)
+		return INVALID_WINFD;
+
+	for (i=0; i<MAX_FDS; i++) {
+		if (poll_fd[i].fd == fd) {
+			EnterCriticalSection(&_poll_fd[i].mutex);
+			// fd might have been deleted before we got to critical
+			if (poll_fd[i].fd != fd) {
+				LeaveCriticalSection(&_poll_fd[i].mutex);
+				continue;
+			}
+			memcpy(&wfd, &poll_fd[i], sizeof(struct winfd));
+			LeaveCriticalSection(&_poll_fd[i].mutex);
+			return wfd;
+		}
+	}
+	return INVALID_WINFD;
+}
+
+struct winfd handle_to_winfd(HANDLE handle)
+{
+	int i;
+	struct winfd wfd;
+
+	CHECK_INIT_POLLING;
+
+	if ((handle == 0) || (handle == INVALID_HANDLE_VALUE))
+		return INVALID_WINFD;
+
+	for (i=0; i<MAX_FDS; i++) {
+		if (poll_fd[i].handle == handle) {
+			EnterCriticalSection(&_poll_fd[i].mutex);
+			// fd might have been deleted before we got to critical
+			if (poll_fd[i].handle != handle) {
+				LeaveCriticalSection(&_poll_fd[i].mutex);
+				continue;
+			}
+			memcpy(&wfd, &poll_fd[i], sizeof(struct winfd));
+			LeaveCriticalSection(&_poll_fd[i].mutex);
+			return wfd;
+		}
+	}
+	return INVALID_WINFD;
+}
+
+struct winfd overlapped_to_winfd(OVERLAPPED* overlapped)
+{
+	int i;
+	struct winfd wfd;
+
+	CHECK_INIT_POLLING;
+
+	if (overlapped == NULL)
+		return INVALID_WINFD;
+
+	for (i=0; i<MAX_FDS; i++) {
+		if (poll_fd[i].overlapped == overlapped) {
+			EnterCriticalSection(&_poll_fd[i].mutex);
+			// fd might have been deleted before we got to critical
+			if (poll_fd[i].overlapped != overlapped) {
+				LeaveCriticalSection(&_poll_fd[i].mutex);
+				continue;
+			}
+			memcpy(&wfd, &poll_fd[i], sizeof(struct winfd));
+			LeaveCriticalSection(&_poll_fd[i].mutex);
+			return wfd;
+		}
+	}
+	return INVALID_WINFD;
+}
+
+/*
+ * POSIX poll equivalent, using Windows OVERLAPPED
+ * Currently, this function only accepts one of POLLIN or POLLOUT per fd
+ * (but you can create multiple fds from the same handle for read and write)
+ */
+int usbi_poll(struct pollfd *fds, unsigned int nfds, int timeout)
+{
+	unsigned i;
+	int _index, object_index, triggered;
+	HANDLE *handles_to_wait_on;
+	int *handle_to_index;
+	DWORD nb_handles_to_wait_on = 0;
+	DWORD ret;
+
+	CHECK_INIT_POLLING;
+
+	triggered = 0;
+	handles_to_wait_on = (HANDLE*) calloc(nfds+1, sizeof(HANDLE));	// +1 for fd_update
+	handle_to_index = (int*) calloc(nfds, sizeof(int));
+	if ((handles_to_wait_on == NULL) || (handle_to_index == NULL)) {
+		errno = ENOMEM;
+		triggered = -1;
+		goto poll_exit;
+	}
+
+	for (i = 0; i < nfds; ++i) {
+		fds[i].revents = 0;
+
+		// Only one of POLLIN or POLLOUT can be selected with this version of poll (not both)
+		if ((fds[i].events & ~POLLIN) && (!(fds[i].events & POLLOUT))) {
+			fds[i].revents |= POLLERR;
+			errno = EACCES;
+			usbi_warn(NULL, "unsupported set of events");
+			triggered = -1;
+			goto poll_exit;
+		}
+
+		_index = _fd_to_index_and_lock(fds[i].fd);
+		poll_dbg("fd[%d]=%d: (overlapped=%p) got events %04X", i, poll_fd[_index].fd, poll_fd[_index].overlapped, fds[i].events);
+
+		if ( (_index < 0) || (poll_fd[_index].handle == INVALID_HANDLE_VALUE)
+		  || (poll_fd[_index].handle == 0) || (poll_fd[_index].overlapped == NULL)) {
+			fds[i].revents |= POLLNVAL | POLLERR;
+			errno = EBADF;
+			if (_index >= 0) {
+				LeaveCriticalSection(&_poll_fd[_index].mutex);
+			}
+			usbi_warn(NULL, "invalid fd");
+			triggered = -1;
+			goto poll_exit;
+		}
+
+		// IN or OUT must match our fd direction
+		if ((fds[i].events & POLLIN) && (poll_fd[_index].rw != RW_READ)) {
+			fds[i].revents |= POLLNVAL | POLLERR;
+			errno = EBADF;
+			usbi_warn(NULL, "attempted POLLIN on fd without READ access");
+			LeaveCriticalSection(&_poll_fd[_index].mutex);
+			triggered = -1;
+			goto poll_exit;
+		}
+
+		if ((fds[i].events & POLLOUT) && (poll_fd[_index].rw != RW_WRITE)) {
+			fds[i].revents |= POLLNVAL | POLLERR;
+			errno = EBADF;
+			usbi_warn(NULL, "attempted POLLOUT on fd without WRITE access");
+			LeaveCriticalSection(&_poll_fd[_index].mutex);
+			triggered = -1;
+			goto poll_exit;
+		}
+
+		// The following macro only works if overlapped I/O was reported pending
+		if ( (HasOverlappedIoCompleted(poll_fd[_index].overlapped))
+		  || (HasOverlappedIoCompletedSync(poll_fd[_index].overlapped)) ) {
+			poll_dbg("  completed");
+			// checks above should ensure this works:
+			fds[i].revents = fds[i].events;
+			triggered++;
+		} else {
+			handles_to_wait_on[nb_handles_to_wait_on] = poll_fd[_index].overlapped->hEvent;
+			handle_to_index[nb_handles_to_wait_on] = i;
+			nb_handles_to_wait_on++;
+		}
+		LeaveCriticalSection(&_poll_fd[_index].mutex);
+	}
+
+	// If nothing was triggered, wait on all fds that require it
+	if ((timeout != 0) && (triggered == 0) && (nb_handles_to_wait_on != 0)) {
+		if (timeout < 0) {
+			poll_dbg("starting infinite wait for %u handles...", (unsigned int)nb_handles_to_wait_on);
+		} else {
+			poll_dbg("starting %d ms wait for %u handles...", timeout, (unsigned int)nb_handles_to_wait_on);
+		}
+		ret = WaitForMultipleObjects(nb_handles_to_wait_on, handles_to_wait_on,
+			FALSE, (timeout<0)?INFINITE:(DWORD)timeout);
+		object_index = ret-WAIT_OBJECT_0;
+		if ((object_index >= 0) && ((DWORD)object_index < nb_handles_to_wait_on)) {
+			poll_dbg("  completed after wait");
+			i = handle_to_index[object_index];
+			_index = _fd_to_index_and_lock(fds[i].fd);
+			fds[i].revents = fds[i].events;
+			triggered++;
+			if (_index >= 0) {
+				LeaveCriticalSection(&_poll_fd[_index].mutex);
+			}
+		} else if (ret == WAIT_TIMEOUT) {
+			poll_dbg("  timed out");
+			triggered = 0;	// 0 = timeout
+		} else {
+			errno = EIO;
+			triggered = -1;	// error
+		}
+	}
+
+poll_exit:
+	if (handles_to_wait_on != NULL) {
+		free(handles_to_wait_on);
+	}
+	if (handle_to_index != NULL) {
+		free(handle_to_index);
+	}
+	return triggered;
+}
+
+/*
+ * close a fake pipe fd
+ */
+int usbi_close(int fd)
+{
+	int _index;
+	int r = -1;
+
+	CHECK_INIT_POLLING;
+
+	_index = _fd_to_index_and_lock(fd);
+
+	if (_index < 0) {
+		errno = EBADF;
+	} else {
+		free_overlapped(poll_fd[_index].overlapped);
+		poll_fd[_index] = INVALID_WINFD;
+		LeaveCriticalSection(&_poll_fd[_index].mutex);
+	}
+	return r;
+}
+
+/*
+ * synchronous write for fake "pipe" signaling
+ */
+ssize_t usbi_write(int fd, const void *buf, size_t count)
+{
+	int _index;
+	UNUSED(buf);
+
+	CHECK_INIT_POLLING;
+
+	if (count != sizeof(unsigned char)) {
+		usbi_err(NULL, "this function should only used for signaling");
+		return -1;
+	}
+
+	_index = _fd_to_index_and_lock(fd);
+
+	if ( (_index < 0) || (poll_fd[_index].overlapped == NULL) ) {
+		errno = EBADF;
+		if (_index >= 0) {
+			LeaveCriticalSection(&_poll_fd[_index].mutex);
+		}
+		return -1;
+	}
+
+	poll_dbg("set pipe event (fd = %d, thread = %08X)", _index, (unsigned int)GetCurrentThreadId());
+	SetEvent(poll_fd[_index].overlapped->hEvent);
+	poll_fd[_index].overlapped->Internal = STATUS_WAIT_0;
+	// If two threads write on the pipe at the same time, we need to
+	// process two separate reads => use the overlapped as a counter
+	poll_fd[_index].overlapped->InternalHigh++;
+
+	LeaveCriticalSection(&_poll_fd[_index].mutex);
+	return sizeof(unsigned char);
+}
+
+/*
+ * synchronous read for fake "pipe" signaling
+ */
+ssize_t usbi_read(int fd, void *buf, size_t count)
+{
+	int _index;
+	ssize_t r = -1;
+	UNUSED(buf);
+
+	CHECK_INIT_POLLING;
+
+	if (count != sizeof(unsigned char)) {
+		usbi_err(NULL, "this function should only used for signaling");
+		return -1;
+	}
+
+	_index = _fd_to_index_and_lock(fd);
+
+	if (_index < 0) {
+		errno = EBADF;
+		return -1;
+	}
+
+	if (WaitForSingleObject(poll_fd[_index].overlapped->hEvent, INFINITE) != WAIT_OBJECT_0) {
+		usbi_warn(NULL, "waiting for event failed: %u", (unsigned int)GetLastError());
+		errno = EIO;
+		goto out;
+	}
+
+	poll_dbg("clr pipe event (fd = %d, thread = %08X)", _index, (unsigned int)GetCurrentThreadId());
+	poll_fd[_index].overlapped->InternalHigh--;
+	// Don't reset unless we don't have any more events to process
+	if (poll_fd[_index].overlapped->InternalHigh <= 0) {
+		ResetEvent(poll_fd[_index].overlapped->hEvent);
+		poll_fd[_index].overlapped->Internal = STATUS_PENDING;
+	}
+
+	r = sizeof(unsigned char);
+
+out:
+	LeaveCriticalSection(&_poll_fd[_index].mutex);
+	return r;
+}
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/poll_windows.h b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/poll_windows.h
new file mode 100644
index 000000000..aa4c985da
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/poll_windows.h
@@ -0,0 +1,131 @@
+/*
+ * Windows compat: POSIX compatibility wrapper
+ * Copyright © 2012-2013 RealVNC Ltd.
+ * Copyright © 2009-2010 Pete Batard <pete@akeo.ie>
+ * With contributions from Michael Plante, Orin Eman et al.
+ * Parts of poll implementation from libusb-win32, by Stephan Meyer et al.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ *
+ */
+#pragma once
+
+#if defined(_MSC_VER)
+// disable /W4 MSVC warnings that are benign
+#pragma warning(disable:4127) // conditional expression is constant
+#endif
+
+// Handle synchronous completion through the overlapped structure
+#if !defined(STATUS_REPARSE)	// reuse the REPARSE status code
+#define STATUS_REPARSE ((LONG)0x00000104L)
+#endif
+#define STATUS_COMPLETED_SYNCHRONOUSLY	STATUS_REPARSE
+#if defined(_WIN32_WCE)
+// WinCE doesn't have a HasOverlappedIoCompleted() macro, so attempt to emulate it
+#define HasOverlappedIoCompleted(lpOverlapped) (((DWORD)(lpOverlapped)->Internal) != STATUS_PENDING)
+#endif
+#define HasOverlappedIoCompletedSync(lpOverlapped)	(((DWORD)(lpOverlapped)->Internal) == STATUS_COMPLETED_SYNCHRONOUSLY)
+
+#define DUMMY_HANDLE ((HANDLE)(LONG_PTR)-2)
+
+/* Windows versions */
+enum windows_version {
+	WINDOWS_CE = -2,
+	WINDOWS_UNDEFINED = -1,
+	WINDOWS_UNSUPPORTED = 0,
+	WINDOWS_XP = 0x51,
+	WINDOWS_2003 = 0x52,	// Also XP x64
+	WINDOWS_VISTA = 0x60,
+	WINDOWS_7 = 0x61,
+	WINDOWS_8 = 0x62,
+	WINDOWS_8_1_OR_LATER = 0x63,
+	WINDOWS_MAX
+};
+extern int windows_version;
+
+#define MAX_FDS     256
+
+#define POLLIN      0x0001    /* There is data to read */
+#define POLLPRI     0x0002    /* There is urgent data to read */
+#define POLLOUT     0x0004    /* Writing now will not block */
+#define POLLERR     0x0008    /* Error condition */
+#define POLLHUP     0x0010    /* Hung up */
+#define POLLNVAL    0x0020    /* Invalid request: fd not open */
+
+struct pollfd {
+    int fd;           /* file descriptor */
+    short events;     /* requested events */
+    short revents;    /* returned events */
+};
+
+// access modes
+enum rw_type {
+	RW_NONE,
+	RW_READ,
+	RW_WRITE,
+};
+
+// fd struct that can be used for polling on Windows
+typedef int cancel_transfer(struct usbi_transfer *itransfer);
+
+struct winfd {
+	int fd;							// what's exposed to libusb core
+	HANDLE handle;					// what we need to attach overlapped to the I/O op, so we can poll it
+	OVERLAPPED* overlapped;			// what will report our I/O status
+	struct usbi_transfer *itransfer;		// Associated transfer, or NULL if completed
+	cancel_transfer *cancel_fn;		// Function pointer to cancel transfer API
+	enum rw_type rw;				// I/O transfer direction: read *XOR* write (NOT BOTH)
+};
+extern const struct winfd INVALID_WINFD;
+
+int usbi_pipe(int pipefd[2]);
+int usbi_poll(struct pollfd *fds, unsigned int nfds, int timeout);
+ssize_t usbi_write(int fd, const void *buf, size_t count);
+ssize_t usbi_read(int fd, void *buf, size_t count);
+int usbi_close(int fd);
+
+void init_polling(void);
+void exit_polling(void);
+struct winfd usbi_create_fd(HANDLE handle, int access_mode, 
+	struct usbi_transfer *transfer, cancel_transfer *cancel_fn);
+void usbi_free_fd(struct winfd* winfd);
+struct winfd fd_to_winfd(int fd);
+struct winfd handle_to_winfd(HANDLE handle);
+struct winfd overlapped_to_winfd(OVERLAPPED* overlapped);
+
+/*
+ * Timeval operations
+ */
+#if defined(DDKBUILD)
+#include <winsock.h>	// defines timeval functions on DDK
+#endif
+
+#if !defined(TIMESPEC_TO_TIMEVAL)
+#define TIMESPEC_TO_TIMEVAL(tv, ts) {                   \
+	(tv)->tv_sec = (long)(ts)->tv_sec;                  \
+	(tv)->tv_usec = (long)(ts)->tv_nsec / 1000;         \
+}
+#endif
+#if !defined(timersub)
+#define timersub(a, b, result)                          \
+do {                                                    \
+	(result)->tv_sec = (a)->tv_sec - (b)->tv_sec;       \
+	(result)->tv_usec = (a)->tv_usec - (b)->tv_usec;    \
+	if ((result)->tv_usec < 0) {                        \
+		--(result)->tv_sec;                             \
+		(result)->tv_usec += 1000000;                   \
+	}                                                   \
+} while (0)
+#endif
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/sunos_usb.c b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/sunos_usb.c
new file mode 100644
index 000000000..cb608976b
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/sunos_usb.c
@@ -0,0 +1,1292 @@
+/*
+ *
+ * Copyright (c) 2016, Oracle and/or its affiliates.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <config.h>
+
+#include <sys/time.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <strings.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <aio.h>
+#include <libdevinfo.h>
+#include <sys/usb/clients/ugen/usb_ugen.h>
+#include <sys/usb/usba.h>
+#include <sys/pci.h>
+
+#include "libusbi.h"
+#include "sunos_usb.h"
+
+/*
+ * Backend functions
+ */
+static int sunos_init(struct libusb_context *);
+static void sunos_exit(void);
+static int sunos_get_device_list(struct libusb_context *,
+    struct discovered_devs **);
+static int sunos_open(struct libusb_device_handle *);
+static void sunos_close(struct libusb_device_handle *);
+static int sunos_get_device_descriptor(struct libusb_device *,
+    uint8_t*, int *);
+static int sunos_get_active_config_descriptor(struct libusb_device *,
+    uint8_t*, size_t, int *);
+static int sunos_get_config_descriptor(struct libusb_device *, uint8_t,
+    uint8_t*, size_t, int *);
+static int sunos_get_configuration(struct libusb_device_handle *, int *);
+static int sunos_set_configuration(struct libusb_device_handle *, int);
+static int sunos_claim_interface(struct libusb_device_handle *, int);
+static int sunos_release_interface(struct libusb_device_handle *, int);
+static int sunos_set_interface_altsetting(struct libusb_device_handle *,
+    int, int);
+static int sunos_clear_halt(struct libusb_device_handle *, uint8_t);
+static int sunos_reset_device(struct libusb_device_handle *);
+static void sunos_destroy_device(struct libusb_device *);
+static int sunos_submit_transfer(struct usbi_transfer *);
+static int sunos_cancel_transfer(struct usbi_transfer *);
+static void sunos_clear_transfer_priv(struct usbi_transfer *);
+static int sunos_handle_transfer_completion(struct usbi_transfer *);
+static int sunos_clock_gettime(int, struct timespec *);
+
+/*
+ * Private functions
+ */
+static int _errno_to_libusb(int);
+static int sunos_usb_get_status(int fd);
+
+static int sunos_init(struct libusb_context *ctx)
+{
+	return (LIBUSB_SUCCESS);
+}
+
+static void sunos_exit(void)
+{
+	usbi_dbg("");
+}
+
+static int
+sunos_fill_in_dev_info(di_node_t node, struct libusb_device *dev)
+{
+	int	proplen;
+	int	n, *addr, *port_prop;
+	char	*phypath;
+	uint8_t	*rdata;
+	struct libusb_device_descriptor	*descr;
+	sunos_dev_priv_t	*dpriv = (sunos_dev_priv_t *)dev->os_priv;
+
+	/* Device descriptors */
+	proplen = di_prop_lookup_bytes(DDI_DEV_T_ANY, node,
+	    "usb-dev-descriptor", &rdata);
+	if (proplen <= 0) {
+
+		return (LIBUSB_ERROR_IO);
+	}
+
+	descr = (struct libusb_device_descriptor *)rdata;
+	bcopy(descr, &dpriv->dev_descr, LIBUSB_DT_DEVICE_SIZE);
+	dpriv->dev_descr.bcdUSB = libusb_cpu_to_le16(descr->bcdUSB);
+	dpriv->dev_descr.idVendor = libusb_cpu_to_le16(descr->idVendor);
+	dpriv->dev_descr.idProduct = libusb_cpu_to_le16(descr->idProduct);
+	dpriv->dev_descr.bcdDevice = libusb_cpu_to_le16(descr->bcdDevice);
+
+	/* Raw configuration descriptors */
+	proplen = di_prop_lookup_bytes(DDI_DEV_T_ANY, node,
+	    "usb-raw-cfg-descriptors", &rdata);
+	if (proplen <= 0) {
+		usbi_dbg("can't find raw config descriptors");
+
+		return (LIBUSB_ERROR_IO);
+	}
+	dpriv->raw_cfgdescr = calloc(1, proplen);
+	if (dpriv->raw_cfgdescr == NULL) {
+		return (LIBUSB_ERROR_NO_MEM);
+	} else {
+		bcopy(rdata, dpriv->raw_cfgdescr, proplen);
+		dpriv->cfgvalue = ((struct libusb_config_descriptor *)
+		    rdata)->bConfigurationValue;
+	}
+
+	n = di_prop_lookup_ints(DDI_DEV_T_ANY, node, "reg", &port_prop);
+
+	if ((n != 1) || (*port_prop <= 0)) {
+		return (LIBUSB_ERROR_IO);
+	}
+	dev->port_number = *port_prop;
+
+	/* device physical path */
+	phypath = di_devfs_path(node);
+	if (phypath) {
+		dpriv->phypath = strdup(phypath);
+		di_devfs_path_free(phypath);
+	} else {
+		free(dpriv->raw_cfgdescr);
+
+		return (LIBUSB_ERROR_IO);
+	}
+
+	/* address */
+	n = di_prop_lookup_ints(DDI_DEV_T_ANY, node, "assigned-address", &addr);
+	if (n != 1 || *addr == 0) {
+		usbi_dbg("can't get address");
+	} else {
+		dev->device_address = *addr;
+	}
+
+	/* speed */
+	if (di_prop_exists(DDI_DEV_T_ANY, node, "low-speed") == 1) {
+		dev->speed = LIBUSB_SPEED_LOW;
+	} else if (di_prop_exists(DDI_DEV_T_ANY, node, "high-speed") == 1) {
+		dev->speed = LIBUSB_SPEED_HIGH;
+	} else if (di_prop_exists(DDI_DEV_T_ANY, node, "full-speed") == 1) {
+		dev->speed = LIBUSB_SPEED_FULL;
+	} else if (di_prop_exists(DDI_DEV_T_ANY, node, "super-speed") == 1) {
+		dev->speed = LIBUSB_SPEED_SUPER;
+	}
+
+	usbi_dbg("vid=%x pid=%x, path=%s, bus_nmber=0x%x, port_number=%d, "
+	    "speed=%d", dpriv->dev_descr.idVendor, dpriv->dev_descr.idProduct,
+	    dpriv->phypath, dev->bus_number, dev->port_number, dev->speed);
+
+	return (LIBUSB_SUCCESS);
+}
+
+
+static int
+sunos_add_devices(di_devlink_t link, void *arg)
+{
+	struct devlink_cbarg	*largs = (struct devlink_cbarg *)arg;
+	struct node_args	*nargs;
+	di_node_t		myself, pnode;
+	uint64_t		session_id = 0;
+	uint16_t		bdf = 0;
+	struct libusb_device	*dev;
+	sunos_dev_priv_t	*devpriv;
+	const char		*path, *newpath;
+	int			 n, i;
+	int			*addr_prop;
+	uint8_t			bus_number = 0;
+
+	nargs = (struct node_args *)largs->nargs;
+	myself = largs->myself;
+	if (nargs->last_ugenpath) {
+		/* the same node's links */
+		return (DI_WALK_CONTINUE);
+	}
+
+	/*
+	 * Construct session ID.
+	 * session ID = ...parent hub addr|hub addr|dev addr.
+	 */
+	pnode = myself;
+	i = 0;
+	while (pnode != DI_NODE_NIL) {
+		if (di_prop_exists(DDI_DEV_T_ANY, pnode, "root-hub") == 1) {
+			/* walk to root */
+			uint32_t *regbuf = NULL;
+			uint32_t reg;
+
+			n = di_prop_lookup_ints(DDI_DEV_T_ANY, pnode, "reg",
+			    (int **)&regbuf);
+			reg = regbuf[0];
+			bdf = (PCI_REG_BUS_G(reg) << 8) |
+			    (PCI_REG_DEV_G(reg) << 3) | PCI_REG_FUNC_G(reg);
+			session_id |= (bdf << i * 8);
+
+			/* same as 'unit-address' property */
+			bus_number =
+			    (PCI_REG_DEV_G(reg) << 3) | PCI_REG_FUNC_G(reg);
+
+			usbi_dbg("device bus address=%s:%x",
+			    di_bus_addr(pnode), bus_number);
+
+			break;
+		}
+
+		/* usb_addr */
+		n = di_prop_lookup_ints(DDI_DEV_T_ANY, pnode,
+		    "assigned-address", &addr_prop);
+		if ((n != 1) || (addr_prop[0] == 0)) {
+			usbi_dbg("cannot get valid usb_addr");
+
+			return (DI_WALK_CONTINUE);
+		}
+
+		session_id |= ((addr_prop[0] & 0xff) << i * 8);
+		if (++i > 7)
+			break;
+
+		pnode = di_parent_node(pnode);
+	}
+
+	path = di_devlink_path(link);
+	dev = usbi_get_device_by_session_id(nargs->ctx, session_id);
+	if (dev == NULL) {
+		dev = usbi_alloc_device(nargs->ctx, session_id);
+		if (dev == NULL) {
+			usbi_dbg("can't alloc device");
+
+			return (DI_WALK_TERMINATE);
+		}
+		devpriv = (sunos_dev_priv_t *)dev->os_priv;
+		if ((newpath = strrchr(path, '/')) == NULL) {
+			libusb_unref_device(dev);
+
+			return (DI_WALK_TERMINATE);
+		}
+		devpriv->ugenpath = strndup(path, strlen(path) -
+		    strlen(newpath));
+		dev->bus_number = bus_number;
+
+		if (sunos_fill_in_dev_info(myself, dev) != LIBUSB_SUCCESS) {
+			libusb_unref_device(dev);
+
+			return (DI_WALK_TERMINATE);
+		}
+		if (usbi_sanitize_device(dev) < 0) {
+			libusb_unref_device(dev);
+			usbi_dbg("sanatize failed: ");
+			return (DI_WALK_TERMINATE);
+		}
+	} else {
+		usbi_dbg("Dev %s exists", path);
+	}
+
+	devpriv = (sunos_dev_priv_t *)dev->os_priv;
+	if (nargs->last_ugenpath == NULL) {
+		/* first device */
+		nargs->last_ugenpath = devpriv->ugenpath;
+
+		if (discovered_devs_append(*(nargs->discdevs), dev) == NULL) {
+			usbi_dbg("cannot append device");
+		}
+
+		/*
+		 * we alloc and hence ref this dev. We don't need to ref it
+		 * hereafter. Front end or app should take care of their ref.
+		 */
+		libusb_unref_device(dev);
+	}
+
+	usbi_dbg("Device %s %s id=0x%llx, devcount:%d, bdf=%x",
+	    devpriv->ugenpath, path, (uint64_t)session_id,
+	    (*nargs->discdevs)->len, bdf);
+
+	return (DI_WALK_CONTINUE);
+}
+
+static int
+sunos_walk_minor_node_link(di_node_t node, void *args)
+{
+        di_minor_t minor = DI_MINOR_NIL;
+        char *minor_path;
+        struct devlink_cbarg arg;
+	struct node_args *nargs = (struct node_args *)args;
+	di_devlink_handle_t devlink_hdl = nargs->dlink_hdl;
+
+	/* walk each minor to find ugen devices */
+        while ((minor = di_minor_next(node, minor)) != DI_MINOR_NIL) {
+                minor_path = di_devfs_minor_path(minor);
+                arg.nargs = args;
+		arg.myself = node;
+                arg.minor = minor;
+                (void) di_devlink_walk(devlink_hdl,
+		    "^usb/[0-9a-f]+[.][0-9a-f]+", minor_path,
+		    DI_PRIMARY_LINK, (void *)&arg, sunos_add_devices);
+                di_devfs_path_free(minor_path);
+        }
+
+	/* switch to a different node */
+	nargs->last_ugenpath = NULL;
+
+	return (DI_WALK_CONTINUE);
+}
+
+int
+sunos_get_device_list(struct libusb_context * ctx,
+	struct discovered_devs **discdevs)
+{
+	di_node_t root_node;
+	struct node_args args;
+	di_devlink_handle_t devlink_hdl;
+
+	args.ctx = ctx;
+	args.discdevs = discdevs;
+	args.last_ugenpath = NULL;
+	if ((root_node = di_init("/", DINFOCPYALL)) == DI_NODE_NIL) {
+		usbi_dbg("di_int() failed: %s", strerror(errno));
+		return (LIBUSB_ERROR_IO);
+	}
+
+	if ((devlink_hdl = di_devlink_init(NULL, 0)) == NULL) {
+		di_fini(root_node);
+		usbi_dbg("di_devlink_init() failed: %s", strerror(errno));
+
+		return (LIBUSB_ERROR_IO);
+	}
+	args.dlink_hdl = devlink_hdl;
+
+	/* walk each node to find USB devices */
+	if (di_walk_node(root_node, DI_WALK_SIBFIRST, &args,
+	    sunos_walk_minor_node_link) == -1) {
+		usbi_dbg("di_walk_node() failed: %s", strerror(errno));
+		di_fini(root_node);
+
+		return (LIBUSB_ERROR_IO);
+	}
+
+	di_fini(root_node);
+	di_devlink_fini(&devlink_hdl);
+
+	usbi_dbg("%d devices", (*discdevs)->len);
+
+	return ((*discdevs)->len);
+}
+
+static int
+sunos_usb_open_ep0(sunos_dev_handle_priv_t *hpriv, sunos_dev_priv_t *dpriv)
+{
+	char filename[PATH_MAX + 1];
+
+	if (hpriv->eps[0].datafd > 0) {
+
+		return (LIBUSB_SUCCESS);
+	}
+	snprintf(filename, PATH_MAX, "%s/cntrl0", dpriv->ugenpath);
+
+	usbi_dbg("opening %s", filename);
+	hpriv->eps[0].datafd = open(filename, O_RDWR);
+	if (hpriv->eps[0].datafd < 0) {
+		return(_errno_to_libusb(errno));
+	}
+
+	snprintf(filename, PATH_MAX, "%s/cntrl0stat", dpriv->ugenpath);
+	hpriv->eps[0].statfd = open(filename, O_RDONLY);
+	if (hpriv->eps[0].statfd < 0) {
+		close(hpriv->eps[0].datafd);
+		hpriv->eps[0].datafd = -1;
+
+		return(_errno_to_libusb(errno));
+	}
+
+	return (LIBUSB_SUCCESS);
+}
+
+static void
+sunos_usb_close_all_eps(sunos_dev_handle_priv_t *hdev)
+{
+	int i;
+
+	/* not close ep0 */
+	for (i = 1; i < USB_MAXENDPOINTS; i++) {
+		if (hdev->eps[i].datafd != -1) {
+			(void) close(hdev->eps[i].datafd);
+			hdev->eps[i].datafd = -1;
+		}
+		if (hdev->eps[i].statfd != -1) {
+			(void) close(hdev->eps[i].statfd);
+			hdev->eps[i].statfd = -1;
+		}
+	}
+}
+
+static void
+sunos_usb_close_ep0(sunos_dev_handle_priv_t *hdev, sunos_dev_priv_t *dpriv)
+{
+	if (hdev->eps[0].datafd >= 0) {
+		close(hdev->eps[0].datafd);
+		close(hdev->eps[0].statfd);
+		hdev->eps[0].datafd = -1;
+		hdev->eps[0].statfd = -1;
+	}
+}
+
+static uchar_t
+sunos_usb_ep_index(uint8_t ep_addr)
+{
+	return ((ep_addr & LIBUSB_ENDPOINT_ADDRESS_MASK) +
+	    ((ep_addr & LIBUSB_ENDPOINT_DIR_MASK) ? 16 : 0));
+}
+
+static int
+sunos_find_interface(struct libusb_device_handle *hdev,
+    uint8_t endpoint, uint8_t *interface)
+{
+	struct libusb_config_descriptor *config;
+	int r;
+	int iface_idx;
+
+	r = libusb_get_active_config_descriptor(hdev->dev, &config);
+	if (r < 0) {
+		return (LIBUSB_ERROR_INVALID_PARAM);
+	}
+
+	for (iface_idx = 0; iface_idx < config->bNumInterfaces; iface_idx++) {
+		const struct libusb_interface *iface =
+		    &config->interface[iface_idx];
+		int altsetting_idx;
+
+		for (altsetting_idx = 0; altsetting_idx < iface->num_altsetting;
+		    altsetting_idx++) {
+			const struct libusb_interface_descriptor *altsetting =
+			    &iface->altsetting[altsetting_idx];
+			int ep_idx;
+
+			for (ep_idx = 0; ep_idx < altsetting->bNumEndpoints;
+			    ep_idx++) {
+				const struct libusb_endpoint_descriptor *ep =
+					&altsetting->endpoint[ep_idx];
+				if (ep->bEndpointAddress == endpoint) {
+					*interface = iface_idx;
+					libusb_free_config_descriptor(config);
+
+					return (LIBUSB_SUCCESS);
+				}
+			}
+		}
+	}
+	libusb_free_config_descriptor(config);
+
+	return (LIBUSB_ERROR_INVALID_PARAM);
+}
+
+static int
+sunos_check_device_and_status_open(struct libusb_device_handle *hdl,
+    uint8_t ep_addr, int ep_type)
+{
+	char	filename[PATH_MAX + 1], statfilename[PATH_MAX + 1];
+	char	cfg_num[16], alt_num[16];
+	int	fd, fdstat, mode;
+	uint8_t	ifc = 0;
+	uint8_t	ep_index;
+	sunos_dev_handle_priv_t *hpriv;
+
+	usbi_dbg("open ep 0x%02x", ep_addr);
+	hpriv = (sunos_dev_handle_priv_t *)hdl->os_priv;
+	ep_index = sunos_usb_ep_index(ep_addr);
+	/* ep already opened */
+	if ((hpriv->eps[ep_index].datafd > 0) &&
+	    (hpriv->eps[ep_index].statfd > 0)) {
+		usbi_dbg("ep 0x%02x already opened, return success",
+			ep_addr);
+
+		return (0);
+	}
+
+	if (sunos_find_interface(hdl, ep_addr, &ifc) < 0) {
+		usbi_dbg("can't find interface for endpoint 0x%02x",
+		    ep_addr);
+
+		return (LIBUSB_ERROR_ACCESS);
+	}
+
+	/* create filename */
+	if (hpriv->config_index > 0) {
+		(void) snprintf(cfg_num, sizeof (cfg_num), "cfg%d",
+		    hpriv->config_index + 1);
+	} else {
+		bzero(cfg_num, sizeof (cfg_num));
+	}
+
+	if (hpriv->altsetting[ifc] > 0) {
+		(void) snprintf(alt_num, sizeof (alt_num), ".%d",
+		    hpriv->altsetting[ifc]);
+	} else {
+		bzero(alt_num, sizeof (alt_num));
+	}
+
+	(void) snprintf(filename, PATH_MAX, "%s/%sif%d%s%s%d",
+	    hpriv->dpriv->ugenpath, cfg_num, ifc, alt_num,
+	    (ep_addr & LIBUSB_ENDPOINT_DIR_MASK) ? "in" :
+	    "out", (ep_addr & LIBUSB_ENDPOINT_ADDRESS_MASK));
+	(void) snprintf(statfilename, PATH_MAX, "%sstat", filename);
+
+	/*
+	 * for interrupt IN endpoints, we need to enable one xfer
+	 * mode before opening the endpoint
+	 */
+	if ((ep_type == LIBUSB_TRANSFER_TYPE_INTERRUPT) &&
+	    (ep_addr & LIBUSB_ENDPOINT_IN)) {
+		char	control = USB_EP_INTR_ONE_XFER;
+		int	count;
+
+		/* open the status device node for the ep first RDWR */
+		if ((fdstat = open(statfilename, O_RDWR)) == -1) {
+			usbi_dbg("can't open %s RDWR: %d",
+				statfilename, errno);
+		} else {
+			count = write(fdstat, &control, sizeof (control));
+			if (count != 1) {
+				/* this should have worked */
+				usbi_dbg("can't write to %s: %d",
+					statfilename, errno);
+				(void) close(fdstat);
+
+				return (errno);
+			}
+			/* close status node and open xfer node first */
+			close (fdstat);
+		}
+	}
+
+	/* open the xfer node first in case alt needs to be changed */
+	if (ep_type == LIBUSB_TRANSFER_TYPE_ISOCHRONOUS) {
+		mode = O_RDWR;
+	} else if (ep_addr & LIBUSB_ENDPOINT_IN) {
+		mode = O_RDONLY;
+	} else {
+		mode = O_WRONLY;
+	}
+
+	/*
+	 * IMPORTANT: must open data xfer node first and then open stat node
+	 * Otherwise, it will fail on multi-config or multi-altsetting devices
+	 * with "Device Busy" error. See ugen_epxs_switch_cfg_alt() and
+	 * ugen_epxs_check_alt_switch() in ugen driver source code.
+	 */
+	if ((fd = open(filename, mode)) == -1) {
+		usbi_dbg("can't open %s: %d(%s)", filename, errno,
+		    strerror(errno));
+
+		return (errno);
+	}
+	/* open the status node */
+	if ((fdstat = open(statfilename, O_RDONLY)) == -1) {
+		usbi_dbg("can't open %s: %d", statfilename, errno);
+
+		(void) close(fd);
+
+		return (errno);
+	}
+
+	hpriv->eps[ep_index].datafd = fd;
+	hpriv->eps[ep_index].statfd = fdstat;
+	usbi_dbg("ep=0x%02x datafd=%d, statfd=%d", ep_addr, fd, fdstat);
+
+	return (0);
+}
+
+int
+sunos_open(struct libusb_device_handle *handle)
+{
+	sunos_dev_handle_priv_t	*hpriv;
+	sunos_dev_priv_t	*dpriv;
+	int	i;
+	int	ret;
+
+	hpriv = (sunos_dev_handle_priv_t *)handle->os_priv;
+	dpriv = (sunos_dev_priv_t *)handle->dev->os_priv;
+	hpriv->dpriv = dpriv;
+
+	/* set all file descriptors to "closed" */
+	for (i = 0; i < USB_MAXENDPOINTS; i++) {
+		hpriv->eps[i].datafd = -1;
+		hpriv->eps[i].statfd = -1;
+	}
+
+	if ((ret = sunos_usb_open_ep0(hpriv, dpriv)) != LIBUSB_SUCCESS) {
+		usbi_dbg("fail: %d", ret);
+		return (ret);
+	}
+
+	return (LIBUSB_SUCCESS);
+}
+
+void
+sunos_close(struct libusb_device_handle *handle)
+{
+	sunos_dev_handle_priv_t *hpriv;
+	sunos_dev_priv_t *dpriv;
+
+	usbi_dbg("");
+	if (!handle) {
+		return;
+	}
+
+	hpriv = (sunos_dev_handle_priv_t *)handle->os_priv;
+	if (!hpriv) {
+		return;
+	}
+	dpriv = (sunos_dev_priv_t *)handle->dev->os_priv;
+	if (!dpriv) {
+		return;
+	}
+
+	sunos_usb_close_all_eps(hpriv);
+	sunos_usb_close_ep0(hpriv, dpriv);
+}
+
+int
+sunos_get_device_descriptor(struct libusb_device *dev, uint8_t *buf,
+    int *host_endian)
+{
+	sunos_dev_priv_t *dpriv = (sunos_dev_priv_t *)dev->os_priv;
+
+	memcpy(buf, &dpriv->dev_descr, LIBUSB_DT_DEVICE_SIZE);
+	*host_endian = 0;
+
+	return (LIBUSB_SUCCESS);
+}
+
+int
+sunos_get_active_config_descriptor(struct libusb_device *dev,
+    uint8_t *buf, size_t len, int *host_endian)
+{
+	sunos_dev_priv_t *dpriv = (sunos_dev_priv_t *)dev->os_priv;
+	struct libusb_config_descriptor *cfg;
+	int proplen;
+	di_node_t node;
+	uint8_t	*rdata;
+
+	/*
+	 * Keep raw configuration descriptors updated, in case config
+	 * has ever been changed through setCfg.
+	 */
+	if ((node = di_init(dpriv->phypath, DINFOCPYALL)) == DI_NODE_NIL) {
+		usbi_dbg("di_int() failed: %s", strerror(errno));
+		return (LIBUSB_ERROR_IO);
+	}
+	proplen = di_prop_lookup_bytes(DDI_DEV_T_ANY, node,
+	    "usb-raw-cfg-descriptors", &rdata);
+	if (proplen <= 0) {
+		usbi_dbg("can't find raw config descriptors");
+
+		return (LIBUSB_ERROR_IO);
+	}
+	dpriv->raw_cfgdescr = realloc(dpriv->raw_cfgdescr, proplen);
+	if (dpriv->raw_cfgdescr == NULL) {
+		return (LIBUSB_ERROR_NO_MEM);
+	} else {
+		bcopy(rdata, dpriv->raw_cfgdescr, proplen);
+		dpriv->cfgvalue = ((struct libusb_config_descriptor *)
+		    rdata)->bConfigurationValue;
+	}
+	di_fini(node);
+
+	cfg = (struct libusb_config_descriptor *)dpriv->raw_cfgdescr;
+	len = MIN(len, libusb_le16_to_cpu(cfg->wTotalLength));
+	memcpy(buf, dpriv->raw_cfgdescr, len);
+	*host_endian = 0;
+	usbi_dbg("path:%s len %d", dpriv->phypath, len);
+
+	return (len);
+}
+
+int
+sunos_get_config_descriptor(struct libusb_device *dev, uint8_t idx,
+    uint8_t *buf, size_t len, int *host_endian)
+{
+	/* XXX */
+	return(sunos_get_active_config_descriptor(dev, buf, len, host_endian));
+}
+
+int
+sunos_get_configuration(struct libusb_device_handle *handle, int *config)
+{
+	sunos_dev_priv_t *dpriv = (sunos_dev_priv_t *)handle->dev->os_priv;
+
+	*config = dpriv->cfgvalue;
+
+	usbi_dbg("bConfigurationValue %d", *config);
+
+	return (LIBUSB_SUCCESS);
+}
+
+int
+sunos_set_configuration(struct libusb_device_handle *handle, int config)
+{
+	sunos_dev_priv_t *dpriv = (sunos_dev_priv_t *)handle->dev->os_priv;
+	sunos_dev_handle_priv_t *hpriv;
+
+	usbi_dbg("bConfigurationValue %d", config);
+	hpriv = (sunos_dev_handle_priv_t *)handle->os_priv;
+
+	if (dpriv->ugenpath == NULL)
+		return (LIBUSB_ERROR_NOT_SUPPORTED);
+
+	if (config < 1 || config > dpriv->dev_descr.bNumConfigurations)
+		return (LIBUSB_ERROR_INVALID_PARAM);
+
+	dpriv->cfgvalue = config;
+	hpriv->config_index = config - 1;
+
+	return (LIBUSB_SUCCESS);
+}
+
+int
+sunos_claim_interface(struct libusb_device_handle *handle, int iface)
+{
+	usbi_dbg("iface %d", iface);
+	if (iface < 0) {
+		return (LIBUSB_ERROR_INVALID_PARAM);
+	}
+
+	return (LIBUSB_SUCCESS);
+}
+
+int
+sunos_release_interface(struct libusb_device_handle *handle, int iface)
+{
+	sunos_dev_handle_priv_t *hpriv =
+	    (sunos_dev_handle_priv_t *)handle->os_priv;
+
+	usbi_dbg("iface %d", iface);
+	if (iface < 0) {
+		return (LIBUSB_ERROR_INVALID_PARAM);
+	}
+
+	/* XXX: can we release it? */
+	hpriv->altsetting[iface] = 0;
+
+	return (LIBUSB_SUCCESS);
+}
+
+int
+sunos_set_interface_altsetting(struct libusb_device_handle *handle, int iface,
+    int altsetting)
+{
+	sunos_dev_priv_t *dpriv = (sunos_dev_priv_t *)handle->dev->os_priv;
+	sunos_dev_handle_priv_t *hpriv =
+	    (sunos_dev_handle_priv_t *)handle->os_priv;
+
+	usbi_dbg("iface %d, setting %d", iface, altsetting);
+
+	if (iface < 0 || altsetting < 0) {
+		return (LIBUSB_ERROR_INVALID_PARAM);
+	}
+	if (dpriv->ugenpath == NULL)
+		return (LIBUSB_ERROR_NOT_FOUND);
+
+	/* XXX: can we switch altsetting? */
+	hpriv->altsetting[iface] = altsetting;
+
+	return (LIBUSB_SUCCESS);
+}
+
+static void
+usb_dump_data(unsigned char *data, size_t size)
+{
+	int i;
+
+	if (getenv("LIBUSB_DEBUG") == NULL) {
+		return;
+	}
+
+	(void) fprintf(stderr, "data dump:");
+	for (i = 0; i < size; i++) {
+		if (i % 16 == 0) {
+			(void) fprintf(stderr, "\n%08x	", i);
+		}
+		(void) fprintf(stderr, "%02x ", (uchar_t)data[i]);
+	}
+	(void) fprintf(stderr, "\n");
+}
+
+static void
+sunos_async_callback(union sigval arg)
+{
+	struct sunos_transfer_priv *tpriv =
+	    (struct sunos_transfer_priv *)arg.sival_ptr;
+	struct libusb_transfer *xfer = tpriv->transfer;
+	struct aiocb *aiocb = &tpriv->aiocb;
+	int ret;
+	sunos_dev_handle_priv_t *hpriv;
+	uint8_t ep;
+
+	hpriv = (sunos_dev_handle_priv_t *)xfer->dev_handle->os_priv;
+	ep = sunos_usb_ep_index(xfer->endpoint);
+
+	ret = aio_error(aiocb);
+	if (ret != 0) {
+		xfer->status = sunos_usb_get_status(hpriv->eps[ep].statfd);
+	} else {
+		xfer->actual_length =
+		    LIBUSB_TRANSFER_TO_USBI_TRANSFER(xfer)->transferred =
+		    aio_return(aiocb);
+	}
+
+	usb_dump_data(xfer->buffer, xfer->actual_length);
+
+	usbi_dbg("ret=%d, len=%d, actual_len=%d", ret, xfer->length,
+	    xfer->actual_length);
+
+	/* async notification */
+	usbi_signal_transfer_completion(LIBUSB_TRANSFER_TO_USBI_TRANSFER(xfer));
+}
+
+static int
+sunos_do_async_io(struct libusb_transfer *transfer)
+{
+	int ret = -1;
+	struct aiocb *aiocb;
+	sunos_dev_handle_priv_t *hpriv;
+	uint8_t ep;
+	struct sunos_transfer_priv *tpriv;
+
+	usbi_dbg("");
+
+	tpriv = usbi_transfer_get_os_priv(LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer));
+	hpriv = (sunos_dev_handle_priv_t *)transfer->dev_handle->os_priv;
+	ep = sunos_usb_ep_index(transfer->endpoint);
+
+	tpriv->transfer = transfer;
+	aiocb = &tpriv->aiocb;
+	bzero(aiocb, sizeof (*aiocb));
+	aiocb->aio_fildes = hpriv->eps[ep].datafd;
+	aiocb->aio_buf = transfer->buffer;
+	aiocb->aio_nbytes = transfer->length;
+	aiocb->aio_lio_opcode =
+	    ((transfer->endpoint & LIBUSB_ENDPOINT_DIR_MASK) ==
+	    LIBUSB_ENDPOINT_IN) ? LIO_READ:LIO_WRITE;
+	aiocb->aio_sigevent.sigev_notify = SIGEV_THREAD;
+	aiocb->aio_sigevent.sigev_value.sival_ptr = tpriv;
+	aiocb->aio_sigevent.sigev_notify_function = sunos_async_callback;
+
+	if (aiocb->aio_lio_opcode == LIO_READ) {
+		ret = aio_read(aiocb);
+	} else {
+		ret = aio_write(aiocb);
+	}
+
+	return (ret);
+}
+
+/* return the number of bytes read/written */
+static int
+usb_do_io(int fd, int stat_fd, char *data, size_t size, int flag, int *status)
+{
+	int error;
+	int ret = -1;
+
+	usbi_dbg("usb_do_io(): datafd=%d statfd=%d size=0x%x flag=%s",
+	    fd, stat_fd, size, flag? "WRITE":"READ");
+
+	switch (flag) {
+	case READ:
+		errno = 0;
+		ret = read(fd, data, size);
+		usb_dump_data(data, size);
+		break;
+	case WRITE:
+		usb_dump_data(data, size);
+		errno = 0;
+		ret = write(fd, data, size);
+		break;
+	}
+
+	usbi_dbg("usb_do_io(): amount=%d", ret);
+
+	if (ret < 0) {
+		int save_errno = errno;
+
+		usbi_dbg("TID=%x io %s errno=%d(%s) ret=%d", pthread_self(),
+		    flag?"WRITE":"READ", errno, strerror(errno), ret);
+
+		/* sunos_usb_get_status will do a read and overwrite errno */
+		error = sunos_usb_get_status(stat_fd);
+		usbi_dbg("io status=%d errno=%d(%s)", error,
+			save_errno, strerror(save_errno));
+
+		if (status) {
+			*status = save_errno;
+		}
+
+		return (save_errno);
+
+	} else if (status) {
+		*status = 0;
+	}
+
+	return (ret);
+}
+
+static int
+solaris_submit_ctrl_on_default(struct libusb_transfer *transfer)
+{
+	int		ret = -1, setup_ret;
+	int		status;
+	sunos_dev_handle_priv_t *hpriv;
+	struct		libusb_device_handle *hdl = transfer->dev_handle;
+	uint16_t	wLength;
+	uint8_t		*data = transfer->buffer;
+
+	hpriv = (sunos_dev_handle_priv_t *)hdl->os_priv;
+	wLength = transfer->length - LIBUSB_CONTROL_SETUP_SIZE;
+
+	if (hpriv->eps[0].datafd == -1) {
+		usbi_dbg("ep0 not opened");
+
+		return (LIBUSB_ERROR_NOT_FOUND);
+	}
+
+	if ((data[0] & LIBUSB_ENDPOINT_DIR_MASK) == LIBUSB_ENDPOINT_IN) {
+		usbi_dbg("IN request");
+		ret = usb_do_io(hpriv->eps[0].datafd,
+		    hpriv->eps[0].statfd, (char *)data, LIBUSB_CONTROL_SETUP_SIZE,
+		    WRITE, (int *)&status);
+	} else {
+		usbi_dbg("OUT request");
+		ret = usb_do_io(hpriv->eps[0].datafd, hpriv->eps[0].statfd,
+		    transfer->buffer, transfer->length, WRITE,
+		    (int *)&transfer->status);
+	}
+
+	setup_ret = ret;
+	if (ret < LIBUSB_CONTROL_SETUP_SIZE) {
+		usbi_dbg("error sending control msg: %d", ret);
+
+		return (LIBUSB_ERROR_IO);
+	}
+
+	ret = transfer->length - LIBUSB_CONTROL_SETUP_SIZE;
+
+	/* Read the remaining bytes for IN request */
+	if ((wLength) && ((data[0] & LIBUSB_ENDPOINT_DIR_MASK) ==
+	    LIBUSB_ENDPOINT_IN)) {
+		usbi_dbg("DATA: %d", transfer->length - setup_ret);
+		ret = usb_do_io(hpriv->eps[0].datafd,
+			hpriv->eps[0].statfd,
+			(char *)transfer->buffer + LIBUSB_CONTROL_SETUP_SIZE,
+			wLength, READ, (int *)&transfer->status);
+	}
+
+	if (ret >= 0) {
+		transfer->actual_length = ret;
+		LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer)->transferred = ret;
+	}
+	usbi_dbg("Done: ctrl data bytes %d", ret);
+
+	/* sync transfer handling */
+	ret = usbi_handle_transfer_completion(LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer),
+	    transfer->status);
+
+	return (ret);
+}
+
+int
+sunos_clear_halt(struct libusb_device_handle *handle, uint8_t endpoint)
+{
+	int ret;
+
+	usbi_dbg("endpoint=0x%02x", endpoint);
+
+	ret = libusb_control_transfer(handle, LIBUSB_ENDPOINT_OUT |
+	    LIBUSB_RECIPIENT_ENDPOINT | LIBUSB_REQUEST_TYPE_STANDARD,
+	    LIBUSB_REQUEST_CLEAR_FEATURE, 0, endpoint, NULL, 0, 1000);
+
+	usbi_dbg("ret=%d", ret);
+
+	return (ret);
+}
+
+int
+sunos_reset_device(struct libusb_device_handle *handle)
+{
+	usbi_dbg("");
+
+	return (LIBUSB_ERROR_NOT_SUPPORTED);
+}
+
+void
+sunos_destroy_device(struct libusb_device *dev)
+{
+	sunos_dev_priv_t *dpriv = (sunos_dev_priv_t *)dev->os_priv;
+
+	usbi_dbg("");
+
+	free(dpriv->raw_cfgdescr);
+	free(dpriv->ugenpath);
+	free(dpriv->phypath);
+}
+
+int
+sunos_submit_transfer(struct usbi_transfer *itransfer)
+{
+	struct	libusb_transfer *transfer;
+	struct	libusb_device_handle *hdl;
+	int	err = 0;
+
+	transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	hdl = transfer->dev_handle;
+
+	err = sunos_check_device_and_status_open(hdl,
+	    transfer->endpoint, transfer->type);
+	if (err < 0) {
+
+		return (_errno_to_libusb(err));
+	}
+
+	switch (transfer->type) {
+	case LIBUSB_TRANSFER_TYPE_CONTROL:
+		/* sync transfer */
+		usbi_dbg("CTRL transfer: %d", transfer->length);
+		err = solaris_submit_ctrl_on_default(transfer);
+		break;
+
+	case LIBUSB_TRANSFER_TYPE_BULK:
+		/* fallthru */
+	case LIBUSB_TRANSFER_TYPE_INTERRUPT:
+		if (transfer->type == LIBUSB_TRANSFER_TYPE_BULK)
+			usbi_dbg("BULK transfer: %d", transfer->length);
+		else
+			usbi_dbg("INTR transfer: %d", transfer->length);
+		err = sunos_do_async_io(transfer);
+		break;
+
+	case LIBUSB_TRANSFER_TYPE_ISOCHRONOUS:
+		/* Isochronous/Stream is not supported */
+
+		/* fallthru */
+	case LIBUSB_TRANSFER_TYPE_BULK_STREAM:
+		if (transfer->type == LIBUSB_TRANSFER_TYPE_ISOCHRONOUS)
+			usbi_dbg("ISOC transfer: %d", transfer->length);
+		else
+			usbi_dbg("BULK STREAM transfer: %d", transfer->length);
+		err = LIBUSB_ERROR_NOT_SUPPORTED;
+		break;
+	}
+
+	return (err);
+}
+
+int
+sunos_cancel_transfer(struct usbi_transfer *itransfer)
+{
+	sunos_xfer_priv_t	*tpriv;
+	sunos_dev_handle_priv_t	*hpriv;
+	struct libusb_transfer	*transfer;
+	struct aiocb	*aiocb;
+	uint8_t		ep;
+	int		ret;
+
+	tpriv = usbi_transfer_get_os_priv(itransfer);
+	aiocb = &tpriv->aiocb;
+	transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	hpriv = (sunos_dev_handle_priv_t *)transfer->dev_handle->os_priv;
+	ep = sunos_usb_ep_index(transfer->endpoint);
+
+	ret = aio_cancel(hpriv->eps[ep].datafd, aiocb);
+
+	usbi_dbg("aio->fd=%d fd=%d ret = %d, %s", aiocb->aio_fildes,
+	    hpriv->eps[ep].datafd, ret, (ret == AIO_CANCELED)?
+	    strerror(0):strerror(errno));
+
+	if (ret != AIO_CANCELED) {
+		ret = _errno_to_libusb(errno);
+	} else {
+	/*
+	 * we don't need to call usbi_handle_transfer_cancellation(),
+	 * because we'll handle everything in sunos_async_callback.
+	 */
+		ret = LIBUSB_SUCCESS;
+	}
+
+	return (ret);
+}
+
+void
+sunos_clear_transfer_priv(struct usbi_transfer *itransfer)
+{
+	usbi_dbg("");
+
+	/* Nothing to do */
+}
+
+int
+sunos_handle_transfer_completion(struct usbi_transfer *itransfer)
+{
+	return usbi_handle_transfer_completion(itransfer, LIBUSB_TRANSFER_COMPLETED);
+}
+
+int
+sunos_clock_gettime(int clkid, struct timespec *tp)
+{
+	usbi_dbg("clock %d", clkid);
+
+	if (clkid == USBI_CLOCK_REALTIME)
+		return clock_gettime(CLOCK_REALTIME, tp);
+
+	if (clkid == USBI_CLOCK_MONOTONIC)
+		return clock_gettime(CLOCK_MONOTONIC, tp);
+
+	return (LIBUSB_ERROR_INVALID_PARAM);
+}
+
+int
+_errno_to_libusb(int err)
+{
+	usbi_dbg("error: %s (%d)", strerror(err), err);
+
+	switch (err) {
+	case EIO:
+		return (LIBUSB_ERROR_IO);
+	case EACCES:
+		return (LIBUSB_ERROR_ACCESS);
+	case ENOENT:
+		return (LIBUSB_ERROR_NO_DEVICE);
+	case ENOMEM:
+		return (LIBUSB_ERROR_NO_MEM);
+	case ETIMEDOUT:
+		return (LIBUSB_ERROR_TIMEOUT);
+	}
+
+	return (LIBUSB_ERROR_OTHER);
+}
+
+/*
+ * sunos_usb_get_status:
+ *	gets status of endpoint
+ *
+ * Returns: ugen's last cmd status
+ */
+static int
+sunos_usb_get_status(int fd)
+{
+	int status, ret;
+
+	usbi_dbg("sunos_usb_get_status(): fd=%d", fd);
+
+	ret = read(fd, &status, sizeof (status));
+	if (ret == sizeof (status)) {
+		switch (status) {
+		case USB_LC_STAT_NOERROR:
+			usbi_dbg("No Error");
+			break;
+		case USB_LC_STAT_CRC:
+			usbi_dbg("CRC Timeout Detected\n");
+			break;
+		case USB_LC_STAT_BITSTUFFING:
+			usbi_dbg("Bit Stuffing Violation\n");
+			break;
+		case USB_LC_STAT_DATA_TOGGLE_MM:
+			usbi_dbg("Data Toggle Mismatch\n");
+			break;
+		case USB_LC_STAT_STALL:
+			usbi_dbg("End Point Stalled\n");
+			break;
+		case USB_LC_STAT_DEV_NOT_RESP:
+			usbi_dbg("Device is Not Responding\n");
+			break;
+		case USB_LC_STAT_PID_CHECKFAILURE:
+			usbi_dbg("PID Check Failure\n");
+			break;
+		case USB_LC_STAT_UNEXP_PID:
+			usbi_dbg("Unexpected PID\n");
+			break;
+		case USB_LC_STAT_DATA_OVERRUN:
+			usbi_dbg("Data Exceeded Size\n");
+			break;
+		case USB_LC_STAT_DATA_UNDERRUN:
+			usbi_dbg("Less data received\n");
+			break;
+		case USB_LC_STAT_BUFFER_OVERRUN:
+			usbi_dbg("Buffer Size Exceeded\n");
+			break;
+		case USB_LC_STAT_BUFFER_UNDERRUN:
+			usbi_dbg("Buffer Underrun\n");
+			break;
+		case USB_LC_STAT_TIMEOUT:
+			usbi_dbg("Command Timed Out\n");
+			break;
+		case USB_LC_STAT_NOT_ACCESSED:
+			usbi_dbg("Not Accessed by h/w\n");
+			break;
+		case USB_LC_STAT_UNSPECIFIED_ERR:
+			usbi_dbg("Unspecified Error\n");
+			break;
+		case USB_LC_STAT_NO_BANDWIDTH:
+			usbi_dbg("No Bandwidth\n");
+			break;
+		case USB_LC_STAT_HW_ERR:
+			usbi_dbg("Host Controller h/w Error\n");
+			break;
+		case USB_LC_STAT_SUSPENDED:
+			usbi_dbg("Device was Suspended\n");
+			break;
+		case USB_LC_STAT_DISCONNECTED:
+			usbi_dbg("Device was Disconnected\n");
+			break;
+		case USB_LC_STAT_INTR_BUF_FULL:
+			usbi_dbg("Interrupt buffer was full\n");
+			break;
+		case USB_LC_STAT_INVALID_REQ:
+			usbi_dbg("Request was Invalid\n");
+			break;
+		case USB_LC_STAT_INTERRUPTED:
+			usbi_dbg("Request was Interrupted\n");
+			break;
+		case USB_LC_STAT_NO_RESOURCES:
+			usbi_dbg("No resources available for "
+			    "request\n");
+			break;
+		case USB_LC_STAT_INTR_POLLING_FAILED:
+			usbi_dbg("Failed to Restart Poll");
+			break;
+		default:
+			usbi_dbg("Error Not Determined %d\n",
+			    status);
+			break;
+		}
+	} else {
+		usbi_dbg("read stat error: %s",strerror(errno));
+		status = -1;
+	}
+
+	return (status);
+}
+
+const struct usbi_os_backend sunos_backend = {
+        .name = "Solaris",
+        .caps = 0,
+        .init = sunos_init,
+        .exit = sunos_exit,
+        .get_device_list = sunos_get_device_list,
+        .get_device_descriptor = sunos_get_device_descriptor,
+        .get_active_config_descriptor = sunos_get_active_config_descriptor,
+        .get_config_descriptor = sunos_get_config_descriptor,
+        .hotplug_poll = NULL,
+        .open = sunos_open,
+        .close = sunos_close,
+        .get_configuration = sunos_get_configuration,
+        .set_configuration = sunos_set_configuration,
+
+        .claim_interface = sunos_claim_interface,
+        .release_interface = sunos_release_interface,
+        .set_interface_altsetting = sunos_set_interface_altsetting,
+        .clear_halt = sunos_clear_halt,
+        .reset_device = sunos_reset_device, /* TODO */
+        .alloc_streams = NULL,
+        .free_streams = NULL,
+        .kernel_driver_active = NULL,
+        .detach_kernel_driver = NULL,
+        .attach_kernel_driver = NULL,
+        .destroy_device = sunos_destroy_device,
+        .submit_transfer = sunos_submit_transfer,
+        .cancel_transfer = sunos_cancel_transfer,
+	.handle_events = NULL,
+        .clear_transfer_priv = sunos_clear_transfer_priv,
+        .handle_transfer_completion = sunos_handle_transfer_completion,
+        .clock_gettime = sunos_clock_gettime,
+        .device_priv_size = sizeof(sunos_dev_priv_t),
+        .device_handle_priv_size = sizeof(sunos_dev_handle_priv_t),
+        .transfer_priv_size = sizeof(sunos_xfer_priv_t),
+};
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/sunos_usb.h b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/sunos_usb.h
new file mode 100644
index 000000000..574166031
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/sunos_usb.h
@@ -0,0 +1,74 @@
+/*
+ *
+ * Copyright (c) 2016, Oracle and/or its affiliates.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef	LIBUSB_SUNOS_H
+#define	LIBUSB_SUNOS_H
+
+#include <libdevinfo.h>
+#include <pthread.h>
+#include "libusbi.h"
+
+#define	READ	0
+#define	WRITE	1
+
+typedef struct sunos_device_priv {
+	uint8_t	cfgvalue;		/* active config value */
+	uint8_t	*raw_cfgdescr;		/* active config descriptor */
+	struct libusb_device_descriptor	dev_descr;	/* usb device descriptor */
+	char	*ugenpath;		/* name of the ugen(4) node */
+	char	*phypath;		/* physical path */
+} sunos_dev_priv_t;
+
+typedef	struct endpoint {
+	int datafd;	/* data file */
+	int statfd;	/* state file */
+} sunos_ep_priv_t;
+
+typedef struct sunos_device_handle_priv {
+	uint8_t			altsetting[USB_MAXINTERFACES];	/* a interface's alt */
+	uint8_t			config_index;
+	sunos_ep_priv_t		eps[USB_MAXENDPOINTS];
+	sunos_dev_priv_t	*dpriv; /* device private */
+} sunos_dev_handle_priv_t;
+
+typedef	struct sunos_transfer_priv {
+	struct aiocb		aiocb;
+	struct libusb_transfer	*transfer;
+} sunos_xfer_priv_t;
+
+struct node_args {
+	struct libusb_context	*ctx;
+	struct discovered_devs	**discdevs;
+	const char		*last_ugenpath;
+	di_devlink_handle_t	dlink_hdl;
+};
+
+struct devlink_cbarg {
+	struct node_args	*nargs;	/* di node walk arguments */
+	di_node_t		myself;	/* the di node */
+	di_minor_t		minor;
+};
+
+/* AIO callback args */
+struct aio_callback_args{
+	struct libusb_transfer *transfer;
+	struct aiocb aiocb;
+};
+
+#endif /* LIBUSB_SUNOS_H */
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/threads_posix.c b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/threads_posix.c
new file mode 100644
index 000000000..a4f270bbe
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/threads_posix.c
@@ -0,0 +1,79 @@
+/*
+ * libusb synchronization using POSIX Threads
+ *
+ * Copyright © 2011 Vitali Lovich <vlovich@aliph.com>
+ * Copyright © 2011 Peter Stuge <peter@stuge.se>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <config.h>
+
+#include <time.h>
+#if defined(__linux__) || defined(__OpenBSD__)
+# if defined(__OpenBSD__)
+#  define _BSD_SOURCE
+# endif
+# include <unistd.h>
+# include <sys/syscall.h>
+#elif defined(__APPLE__)
+# include <mach/mach.h>
+#elif defined(__CYGWIN__)
+# include <windows.h>
+#endif
+
+#include "threads_posix.h"
+#include "libusbi.h"
+
+int usbi_cond_timedwait(pthread_cond_t *cond,
+	pthread_mutex_t *mutex, const struct timeval *tv)
+{
+	struct timespec timeout;
+	int r;
+
+	r = usbi_backend->clock_gettime(USBI_CLOCK_REALTIME, &timeout);
+	if (r < 0)
+		return r;
+
+	timeout.tv_sec += tv->tv_sec;
+	timeout.tv_nsec += tv->tv_usec * 1000;
+	while (timeout.tv_nsec >= 1000000000L) {
+		timeout.tv_nsec -= 1000000000L;
+		timeout.tv_sec++;
+	}
+
+	return pthread_cond_timedwait(cond, mutex, &timeout);
+}
+
+int usbi_get_tid(void)
+{
+	int ret = -1;
+#if defined(__ANDROID__)
+	ret = gettid();
+#elif defined(__linux__)
+	ret = syscall(SYS_gettid);
+#elif defined(__OpenBSD__)
+	/* The following only works with OpenBSD > 5.1 as it requires
+	   real thread support. For 5.1 and earlier, -1 is returned. */
+	ret = syscall(SYS_getthrid);
+#elif defined(__APPLE__)
+	ret = mach_thread_self();
+	mach_port_deallocate(mach_task_self(), ret);
+#elif defined(__CYGWIN__)
+	ret = GetCurrentThreadId();
+#endif
+/* TODO: NetBSD thread ID support */
+	return ret;
+}
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/threads_posix.h b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/threads_posix.h
new file mode 100644
index 000000000..4c1514ea6
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/threads_posix.h
@@ -0,0 +1,55 @@
+/*
+ * libusb synchronization using POSIX Threads
+ *
+ * Copyright © 2010 Peter Stuge <peter@stuge.se>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef LIBUSB_THREADS_POSIX_H
+#define LIBUSB_THREADS_POSIX_H
+
+#include <pthread.h>
+#ifdef HAVE_SYS_TIME_H
+#include <sys/time.h>
+#endif
+
+#define usbi_mutex_static_t		pthread_mutex_t
+#define USBI_MUTEX_INITIALIZER		PTHREAD_MUTEX_INITIALIZER
+#define usbi_mutex_static_lock		pthread_mutex_lock
+#define usbi_mutex_static_unlock	pthread_mutex_unlock
+
+#define usbi_mutex_t			pthread_mutex_t
+#define usbi_mutex_init(mutex)		pthread_mutex_init((mutex), NULL)
+#define usbi_mutex_lock			pthread_mutex_lock
+#define usbi_mutex_unlock		pthread_mutex_unlock
+#define usbi_mutex_trylock		pthread_mutex_trylock
+#define usbi_mutex_destroy		pthread_mutex_destroy
+
+#define usbi_cond_t			pthread_cond_t
+#define usbi_cond_init(cond)		pthread_cond_init((cond), NULL)
+#define usbi_cond_wait			pthread_cond_wait
+#define usbi_cond_broadcast		pthread_cond_broadcast
+#define usbi_cond_destroy		pthread_cond_destroy
+
+#define usbi_tls_key_t			pthread_key_t
+#define usbi_tls_key_create(key)	pthread_key_create((key), NULL)
+#define usbi_tls_key_get		pthread_getspecific
+#define usbi_tls_key_set		pthread_setspecific
+#define usbi_tls_key_delete		pthread_key_delete
+
+int usbi_get_tid(void);
+
+#endif /* LIBUSB_THREADS_POSIX_H */
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/threads_windows.c b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/threads_windows.c
new file mode 100644
index 000000000..7c2e52dba
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/threads_windows.c
@@ -0,0 +1,259 @@
+/*
+ * libusb synchronization on Microsoft Windows
+ *
+ * Copyright © 2010 Michael Plante <michael.plante@gmail.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <config.h>
+
+#include <objbase.h>
+#include <errno.h>
+
+#include "libusbi.h"
+
+struct usbi_cond_perthread {
+	struct list_head list;
+	DWORD tid;
+	HANDLE event;
+};
+
+int usbi_mutex_static_lock(usbi_mutex_static_t *mutex)
+{
+	if (!mutex)
+		return EINVAL;
+	while (InterlockedExchange(mutex, 1) == 1)
+		SleepEx(0, TRUE);
+	return 0;
+}
+
+int usbi_mutex_static_unlock(usbi_mutex_static_t *mutex)
+{
+	if (!mutex)
+		return EINVAL;
+	InterlockedExchange(mutex, 0);
+	return 0;
+}
+
+int usbi_mutex_init(usbi_mutex_t *mutex)
+{
+	if (!mutex)
+		return EINVAL;
+	*mutex = CreateMutex(NULL, FALSE, NULL);
+	if (!*mutex)
+		return ENOMEM;
+	return 0;
+}
+
+int usbi_mutex_lock(usbi_mutex_t *mutex)
+{
+	DWORD result;
+
+	if (!mutex)
+		return EINVAL;
+	result = WaitForSingleObject(*mutex, INFINITE);
+	if (result == WAIT_OBJECT_0 || result == WAIT_ABANDONED)
+		return 0; // acquired (ToDo: check that abandoned is ok)
+	else
+		return EINVAL; // don't know how this would happen
+			       //   so don't know proper errno
+}
+
+int usbi_mutex_unlock(usbi_mutex_t *mutex)
+{
+	if (!mutex)
+		return EINVAL;
+	if (ReleaseMutex(*mutex))
+		return 0;
+	else
+		return EPERM;
+}
+
+int usbi_mutex_trylock(usbi_mutex_t *mutex)
+{
+	DWORD result;
+
+	if (!mutex)
+		return EINVAL;
+	result = WaitForSingleObject(*mutex, 0);
+	if (result == WAIT_OBJECT_0 || result == WAIT_ABANDONED)
+		return 0; // acquired (ToDo: check that abandoned is ok)
+	else if (result == WAIT_TIMEOUT)
+		return EBUSY;
+	else
+		return EINVAL; // don't know how this would happen
+			       //   so don't know proper error
+}
+
+int usbi_mutex_destroy(usbi_mutex_t *mutex)
+{
+	// It is not clear if CloseHandle failure is due to failure to unlock.
+	//   If so, this should be errno=EBUSY.
+	if (!mutex || !CloseHandle(*mutex))
+		return EINVAL;
+	*mutex = NULL;
+	return 0;
+}
+
+int usbi_cond_init(usbi_cond_t *cond)
+{
+	if (!cond)
+		return EINVAL;
+	list_init(&cond->waiters);
+	list_init(&cond->not_waiting);
+	return 0;
+}
+
+int usbi_cond_destroy(usbi_cond_t *cond)
+{
+	// This assumes no one is using this anymore.  The check MAY NOT BE safe.
+	struct usbi_cond_perthread *pos, *next_pos;
+
+	if(!cond)
+		return EINVAL;
+	if (!list_empty(&cond->waiters))
+		return EBUSY; // (!see above!)
+	list_for_each_entry_safe(pos, next_pos, &cond->not_waiting, list, struct usbi_cond_perthread) {
+		CloseHandle(pos->event);
+		list_del(&pos->list);
+		free(pos);
+	}
+	return 0;
+}
+
+int usbi_cond_broadcast(usbi_cond_t *cond)
+{
+	// Assumes mutex is locked; this is not in keeping with POSIX spec, but
+	//   libusb does this anyway, so we simplify by not adding more sync
+	//   primitives to the CV definition!
+	int fail = 0;
+	struct usbi_cond_perthread *pos;
+
+	if (!cond)
+		return EINVAL;
+	list_for_each_entry(pos, &cond->waiters, list, struct usbi_cond_perthread) {
+		if (!SetEvent(pos->event))
+			fail = 1;
+	}
+	// The wait function will remove its respective item from the list.
+	return fail ? EINVAL : 0;
+}
+
+__inline static int usbi_cond_intwait(usbi_cond_t *cond,
+	usbi_mutex_t *mutex, DWORD timeout_ms)
+{
+	struct usbi_cond_perthread *pos;
+	int r, found = 0;
+	DWORD r2, tid = GetCurrentThreadId();
+
+	if (!cond || !mutex)
+		return EINVAL;
+	list_for_each_entry(pos, &cond->not_waiting, list, struct usbi_cond_perthread) {
+		if(tid == pos->tid) {
+			found = 1;
+			break;
+		}
+	}
+
+	if (!found) {
+		pos = calloc(1, sizeof(struct usbi_cond_perthread));
+		if (!pos)
+			return ENOMEM; // This errno is not POSIX-allowed.
+		pos->tid = tid;
+		pos->event = CreateEvent(NULL, FALSE, FALSE, NULL); // auto-reset.
+		if (!pos->event) {
+			free(pos);
+			return ENOMEM;
+		}
+		list_add(&pos->list, &cond->not_waiting);
+	}
+
+	list_del(&pos->list); // remove from not_waiting list.
+	list_add(&pos->list, &cond->waiters);
+
+	r  = usbi_mutex_unlock(mutex);
+	if (r)
+		return r;
+
+	r2 = WaitForSingleObject(pos->event, timeout_ms);
+	r = usbi_mutex_lock(mutex);
+	if (r)
+		return r;
+
+	list_del(&pos->list);
+	list_add(&pos->list, &cond->not_waiting);
+
+	if (r2 == WAIT_OBJECT_0)
+		return 0;
+	else if (r2 == WAIT_TIMEOUT)
+		return ETIMEDOUT;
+	else
+		return EINVAL;
+}
+// N.B.: usbi_cond_*wait() can also return ENOMEM, even though pthread_cond_*wait cannot!
+int usbi_cond_wait(usbi_cond_t *cond, usbi_mutex_t *mutex)
+{
+	return usbi_cond_intwait(cond, mutex, INFINITE);
+}
+
+int usbi_cond_timedwait(usbi_cond_t *cond,
+	usbi_mutex_t *mutex, const struct timeval *tv)
+{
+	DWORD millis;
+
+	millis = (DWORD)(tv->tv_sec * 1000) + (tv->tv_usec / 1000);
+	/* round up to next millisecond */
+	if (tv->tv_usec % 1000)
+		millis++;
+	return usbi_cond_intwait(cond, mutex, millis);
+}
+
+int usbi_tls_key_create(usbi_tls_key_t *key)
+{
+	if (!key)
+		return EINVAL;
+	*key = TlsAlloc();
+	if (*key == TLS_OUT_OF_INDEXES)
+		return ENOMEM;
+	else
+		return 0;
+}
+
+void *usbi_tls_key_get(usbi_tls_key_t key)
+{
+	return TlsGetValue(key);
+}
+
+int usbi_tls_key_set(usbi_tls_key_t key, void *value)
+{
+	if (TlsSetValue(key, value))
+		return 0;
+	else
+		return EINVAL;
+}
+
+int usbi_tls_key_delete(usbi_tls_key_t key)
+{
+	if (TlsFree(key))
+		return 0;
+	else
+		return EINVAL;
+}
+
+int usbi_get_tid(void)
+{
+	return (int)GetCurrentThreadId();
+}
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/threads_windows.h b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/threads_windows.h
new file mode 100644
index 000000000..e97ee7875
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/threads_windows.h
@@ -0,0 +1,76 @@
+/*
+ * libusb synchronization on Microsoft Windows
+ *
+ * Copyright © 2010 Michael Plante <michael.plante@gmail.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef LIBUSB_THREADS_WINDOWS_H
+#define LIBUSB_THREADS_WINDOWS_H
+
+#define usbi_mutex_static_t	volatile LONG
+#define USBI_MUTEX_INITIALIZER	0
+
+#define usbi_mutex_t		HANDLE
+
+typedef struct usbi_cond {
+	// Every time a thread touches the CV, it winds up in one of these lists.
+	//   It stays there until the CV is destroyed, even if the thread terminates.
+	struct list_head waiters;
+	struct list_head not_waiting;
+} usbi_cond_t;
+
+// We *were* getting timespec from pthread.h:
+#if (!defined(HAVE_STRUCT_TIMESPEC) && !defined(_TIMESPEC_DEFINED))
+#define HAVE_STRUCT_TIMESPEC 1
+#define _TIMESPEC_DEFINED 1
+struct timespec {
+	long tv_sec;
+	long tv_nsec;
+};
+#endif /* HAVE_STRUCT_TIMESPEC | _TIMESPEC_DEFINED */
+
+// We *were* getting ETIMEDOUT from pthread.h:
+#ifndef ETIMEDOUT
+#  define ETIMEDOUT 10060     /* This is the value in winsock.h. */
+#endif
+
+#define usbi_tls_key_t		DWORD
+
+int usbi_mutex_static_lock(usbi_mutex_static_t *mutex);
+int usbi_mutex_static_unlock(usbi_mutex_static_t *mutex);
+
+int usbi_mutex_init(usbi_mutex_t *mutex);
+int usbi_mutex_lock(usbi_mutex_t *mutex);
+int usbi_mutex_unlock(usbi_mutex_t *mutex);
+int usbi_mutex_trylock(usbi_mutex_t *mutex);
+int usbi_mutex_destroy(usbi_mutex_t *mutex);
+
+int usbi_cond_init(usbi_cond_t *cond);
+int usbi_cond_wait(usbi_cond_t *cond, usbi_mutex_t *mutex);
+int usbi_cond_timedwait(usbi_cond_t *cond,
+	usbi_mutex_t *mutex, const struct timeval *tv);
+int usbi_cond_broadcast(usbi_cond_t *cond);
+int usbi_cond_destroy(usbi_cond_t *cond);
+
+int usbi_tls_key_create(usbi_tls_key_t *key);
+void *usbi_tls_key_get(usbi_tls_key_t key);
+int usbi_tls_key_set(usbi_tls_key_t key, void *value);
+int usbi_tls_key_delete(usbi_tls_key_t key);
+
+int usbi_get_tid(void);
+
+#endif /* LIBUSB_THREADS_WINDOWS_H */
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/wince_usb.c b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/wince_usb.c
new file mode 100644
index 000000000..0d466b8c9
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/wince_usb.c
@@ -0,0 +1,899 @@
+/*
+ * Windows CE backend for libusb 1.0
+ * Copyright © 2011-2013 RealVNC Ltd.
+ * Large portions taken from Windows backend, which is
+ * Copyright © 2009-2010 Pete Batard <pbatard@gmail.com>
+ * With contributions from Michael Plante, Orin Eman et al.
+ * Parts of this code adapted from libusb-win32-v1 by Stephan Meyer
+ * Major code testing contribution by Xiaofan Chen
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <config.h>
+
+#include <stdint.h>
+#include <inttypes.h>
+
+#include "libusbi.h"
+#include "wince_usb.h"
+
+// Global variables
+int windows_version = WINDOWS_CE;
+static uint64_t hires_frequency, hires_ticks_to_ps;
+static HANDLE driver_handle = INVALID_HANDLE_VALUE;
+static int concurrent_usage = -1;
+
+/*
+ * Converts a windows error to human readable string
+ * uses retval as errorcode, or, if 0, use GetLastError()
+ */
+#if defined(ENABLE_LOGGING)
+static const char *windows_error_str(DWORD error_code)
+{
+	static TCHAR wErr_string[ERR_BUFFER_SIZE];
+	static char err_string[ERR_BUFFER_SIZE];
+
+	DWORD size;
+	int len;
+
+	if (error_code == 0)
+		error_code = GetLastError();
+
+	len = sprintf(err_string, "[%u] ", (unsigned int)error_code);
+
+	size = FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM|FORMAT_MESSAGE_IGNORE_INSERTS,
+		NULL, error_code, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
+		wErr_string, ERR_BUFFER_SIZE, NULL);
+	if (size == 0) {
+		DWORD format_error = GetLastError();
+		if (format_error)
+			snprintf(err_string, ERR_BUFFER_SIZE,
+				"Windows error code %u (FormatMessage error code %u)",
+				(unsigned int)error_code, (unsigned int)format_error);
+		else
+			snprintf(err_string, ERR_BUFFER_SIZE, "Unknown error code %u", (unsigned int)error_code);
+	} else {
+		// Remove CR/LF terminators, if present
+		size_t pos = size - 2;
+		if (wErr_string[pos] == 0x0D)
+			wErr_string[pos] = 0;
+
+		if (!WideCharToMultiByte(CP_ACP, 0, wErr_string, -1, &err_string[len], ERR_BUFFER_SIZE - len, NULL, NULL))
+			strcpy(err_string, "Unable to convert error string");
+	}
+
+	return err_string;
+}
+#endif
+
+static struct wince_device_priv *_device_priv(struct libusb_device *dev)
+{
+	return (struct wince_device_priv *)dev->os_priv;
+}
+
+// ceusbkwrapper to libusb error code mapping
+static int translate_driver_error(DWORD error)
+{
+	switch (error) {
+	case ERROR_INVALID_PARAMETER:
+		return LIBUSB_ERROR_INVALID_PARAM;
+	case ERROR_CALL_NOT_IMPLEMENTED:
+	case ERROR_NOT_SUPPORTED:
+		return LIBUSB_ERROR_NOT_SUPPORTED;
+	case ERROR_NOT_ENOUGH_MEMORY:
+		return LIBUSB_ERROR_NO_MEM;
+	case ERROR_INVALID_HANDLE:
+		return LIBUSB_ERROR_NO_DEVICE;
+	case ERROR_BUSY:
+		return LIBUSB_ERROR_BUSY;
+
+	// Error codes that are either unexpected, or have
+	// no suitable LIBUSB_ERROR equivalent.
+	case ERROR_CANCELLED:
+	case ERROR_INTERNAL_ERROR:
+	default:
+		return LIBUSB_ERROR_OTHER;
+	}
+}
+
+static int init_dllimports(void)
+{
+	DLL_GET_HANDLE(ceusbkwrapper);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwOpenDriver, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwGetDeviceList, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwReleaseDeviceList, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwGetDeviceAddress, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwGetDeviceDescriptor, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwGetConfigDescriptor, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwCloseDriver, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwCancelTransfer, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwIssueControlTransfer, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwClaimInterface, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwReleaseInterface, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwSetInterfaceAlternateSetting, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwClearHaltHost, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwClearHaltDevice, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwGetConfig, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwSetConfig, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwResetDevice, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwKernelDriverActive, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwAttachKernelDriver, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwDetachKernelDriver, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwIssueBulkTransfer, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwIsPipeHalted, TRUE);
+
+	return LIBUSB_SUCCESS;
+}
+
+static void exit_dllimports(void)
+{
+	DLL_FREE_HANDLE(ceusbkwrapper);
+}
+
+static int init_device(
+	struct libusb_device *dev, UKW_DEVICE drv_dev,
+	unsigned char bus_addr, unsigned char dev_addr)
+{
+	struct wince_device_priv *priv = _device_priv(dev);
+	int r = LIBUSB_SUCCESS;
+
+	dev->bus_number = bus_addr;
+	dev->device_address = dev_addr;
+	priv->dev = drv_dev;
+
+	if (!UkwGetDeviceDescriptor(priv->dev, &(priv->desc)))
+		r = translate_driver_error(GetLastError());
+
+	return r;
+}
+
+// Internal API functions
+static int wince_init(struct libusb_context *ctx)
+{
+	int r = LIBUSB_ERROR_OTHER;
+	HANDLE semaphore;
+	LARGE_INTEGER li_frequency;
+	TCHAR sem_name[11 + 8 + 1]; // strlen("libusb_init") + (32-bit hex PID) + '\0'
+
+	_stprintf(sem_name, _T("libusb_init%08X"), (unsigned int)(GetCurrentProcessId() & 0xFFFFFFFF));
+	semaphore = CreateSemaphore(NULL, 1, 1, sem_name);
+	if (semaphore == NULL) {
+		usbi_err(ctx, "could not create semaphore: %s", windows_error_str(0));
+		return LIBUSB_ERROR_NO_MEM;
+	}
+
+	// A successful wait brings our semaphore count to 0 (unsignaled)
+	// => any concurent wait stalls until the semaphore's release
+	if (WaitForSingleObject(semaphore, INFINITE) != WAIT_OBJECT_0) {
+		usbi_err(ctx, "failure to access semaphore: %s", windows_error_str(0));
+		CloseHandle(semaphore);
+		return LIBUSB_ERROR_NO_MEM;
+	}
+
+	// NB: concurrent usage supposes that init calls are equally balanced with
+	// exit calls. If init is called more than exit, we will not exit properly
+	if ( ++concurrent_usage == 0 ) {	// First init?
+		// Initialize pollable file descriptors
+		init_polling();
+
+		// Load DLL imports
+		if (init_dllimports() != LIBUSB_SUCCESS) {
+			usbi_err(ctx, "could not resolve DLL functions");
+			r = LIBUSB_ERROR_NOT_SUPPORTED;
+			goto init_exit;
+		}
+
+		// try to open a handle to the driver
+		driver_handle = UkwOpenDriver();
+		if (driver_handle == INVALID_HANDLE_VALUE) {
+			usbi_err(ctx, "could not connect to driver");
+			r = LIBUSB_ERROR_NOT_SUPPORTED;
+			goto init_exit;
+		}
+
+		// find out if we have access to a monotonic (hires) timer
+		if (QueryPerformanceFrequency(&li_frequency)) {
+			hires_frequency = li_frequency.QuadPart;
+			// The hires frequency can go as high as 4 GHz, so we'll use a conversion
+			// to picoseconds to compute the tv_nsecs part in clock_gettime
+			hires_ticks_to_ps = UINT64_C(1000000000000) / hires_frequency;
+			usbi_dbg("hires timer available (Frequency: %"PRIu64" Hz)", hires_frequency);
+		} else {
+			usbi_dbg("no hires timer available on this platform");
+			hires_frequency = 0;
+			hires_ticks_to_ps = UINT64_C(0);
+		}
+	}
+	// At this stage, either we went through full init successfully, or didn't need to
+	r = LIBUSB_SUCCESS;
+
+init_exit: // Holds semaphore here.
+	if (!concurrent_usage && r != LIBUSB_SUCCESS) { // First init failed?
+		exit_dllimports();
+		exit_polling();
+
+		if (driver_handle != INVALID_HANDLE_VALUE) {
+			UkwCloseDriver(driver_handle);
+			driver_handle = INVALID_HANDLE_VALUE;
+		}
+	}
+
+	if (r != LIBUSB_SUCCESS)
+		--concurrent_usage; // Not expected to call libusb_exit if we failed.
+
+	ReleaseSemaphore(semaphore, 1, NULL);	// increase count back to 1
+	CloseHandle(semaphore);
+	return r;
+}
+
+static void wince_exit(void)
+{
+	HANDLE semaphore;
+	TCHAR sem_name[11 + 8 + 1]; // strlen("libusb_init") + (32-bit hex PID) + '\0'
+
+	_stprintf(sem_name, _T("libusb_init%08X"), (unsigned int)(GetCurrentProcessId() & 0xFFFFFFFF));
+	semaphore = CreateSemaphore(NULL, 1, 1, sem_name);
+	if (semaphore == NULL)
+		return;
+
+	// A successful wait brings our semaphore count to 0 (unsignaled)
+	// => any concurent wait stalls until the semaphore release
+	if (WaitForSingleObject(semaphore, INFINITE) != WAIT_OBJECT_0) {
+		CloseHandle(semaphore);
+		return;
+	}
+
+	// Only works if exits and inits are balanced exactly
+	if (--concurrent_usage < 0) {	// Last exit
+		exit_dllimports();
+		exit_polling();
+
+		if (driver_handle != INVALID_HANDLE_VALUE) {
+			UkwCloseDriver(driver_handle);
+			driver_handle = INVALID_HANDLE_VALUE;
+		}
+	}
+
+	ReleaseSemaphore(semaphore, 1, NULL);	// increase count back to 1
+	CloseHandle(semaphore);
+}
+
+static int wince_get_device_list(
+	struct libusb_context *ctx,
+	struct discovered_devs **discdevs)
+{
+	UKW_DEVICE devices[MAX_DEVICE_COUNT];
+	struct discovered_devs *new_devices = *discdevs;
+	DWORD count = 0, i;
+	struct libusb_device *dev = NULL;
+	unsigned char bus_addr, dev_addr;
+	unsigned long session_id;
+	BOOL success;
+	DWORD release_list_offset = 0;
+	int r = LIBUSB_SUCCESS;
+
+	success = UkwGetDeviceList(driver_handle, devices, MAX_DEVICE_COUNT, &count);
+	if (!success) {
+		int libusbErr = translate_driver_error(GetLastError());
+		usbi_err(ctx, "could not get devices: %s", windows_error_str(0));
+		return libusbErr;
+	}
+
+	for (i = 0; i < count; ++i) {
+		release_list_offset = i;
+		success = UkwGetDeviceAddress(devices[i], &bus_addr, &dev_addr, &session_id);
+		if (!success) {
+			r = translate_driver_error(GetLastError());
+			usbi_err(ctx, "could not get device address for %u: %s", (unsigned int)i, windows_error_str(0));
+			goto err_out;
+		}
+
+		dev = usbi_get_device_by_session_id(ctx, session_id);
+		if (dev) {
+			usbi_dbg("using existing device for %u/%u (session %lu)",
+					bus_addr, dev_addr, session_id);
+			// Release just this element in the device list (as we already hold a
+			// reference to it).
+			UkwReleaseDeviceList(driver_handle, &devices[i], 1);
+			release_list_offset++;
+		} else {
+			usbi_dbg("allocating new device for %u/%u (session %lu)",
+					bus_addr, dev_addr, session_id);
+			dev = usbi_alloc_device(ctx, session_id);
+			if (!dev) {
+				r = LIBUSB_ERROR_NO_MEM;
+				goto err_out;
+			}
+
+			r = init_device(dev, devices[i], bus_addr, dev_addr);
+			if (r < 0)
+				goto err_out;
+
+			r = usbi_sanitize_device(dev);
+			if (r < 0)
+				goto err_out;
+		}
+
+		new_devices = discovered_devs_append(new_devices, dev);
+		if (!discdevs) {
+			r = LIBUSB_ERROR_NO_MEM;
+			goto err_out;
+		}
+
+		libusb_unref_device(dev);
+	}
+
+	*discdevs = new_devices;
+	return r;
+err_out:
+	*discdevs = new_devices;
+	libusb_unref_device(dev);
+	// Release the remainder of the unprocessed device list.
+	// The devices added to new_devices already will still be passed up to libusb,
+	// which can dispose of them at its leisure.
+	UkwReleaseDeviceList(driver_handle, &devices[release_list_offset], count - release_list_offset);
+	return r;
+}
+
+static int wince_open(struct libusb_device_handle *handle)
+{
+	// Nothing to do to open devices as a handle to it has
+	// been retrieved by wince_get_device_list
+	return LIBUSB_SUCCESS;
+}
+
+static void wince_close(struct libusb_device_handle *handle)
+{
+	// Nothing to do as wince_open does nothing.
+}
+
+static int wince_get_device_descriptor(
+	struct libusb_device *device,
+	unsigned char *buffer, int *host_endian)
+{
+	struct wince_device_priv *priv = _device_priv(device);
+
+	*host_endian = 1;
+	memcpy(buffer, &priv->desc, DEVICE_DESC_LENGTH);
+	return LIBUSB_SUCCESS;
+}
+
+static int wince_get_active_config_descriptor(
+	struct libusb_device *device,
+	unsigned char *buffer, size_t len, int *host_endian)
+{
+	struct wince_device_priv *priv = _device_priv(device);
+	DWORD actualSize = len;
+
+	*host_endian = 0;
+	if (!UkwGetConfigDescriptor(priv->dev, UKW_ACTIVE_CONFIGURATION, buffer, len, &actualSize))
+		return translate_driver_error(GetLastError());
+
+	return actualSize;
+}
+
+static int wince_get_config_descriptor(
+	struct libusb_device *device,
+	uint8_t config_index,
+	unsigned char *buffer, size_t len, int *host_endian)
+{
+	struct wince_device_priv *priv = _device_priv(device);
+	DWORD actualSize = len;
+
+	*host_endian = 0;
+	if (!UkwGetConfigDescriptor(priv->dev, config_index, buffer, len, &actualSize))
+		return translate_driver_error(GetLastError());
+
+	return actualSize;
+}
+
+static int wince_get_configuration(
+	struct libusb_device_handle *handle,
+	int *config)
+{
+	struct wince_device_priv *priv = _device_priv(handle->dev);
+	UCHAR cv = 0;
+
+	if (!UkwGetConfig(priv->dev, &cv))
+		return translate_driver_error(GetLastError());
+
+	(*config) = cv;
+	return LIBUSB_SUCCESS;
+}
+
+static int wince_set_configuration(
+	struct libusb_device_handle *handle,
+	int config)
+{
+	struct wince_device_priv *priv = _device_priv(handle->dev);
+	// Setting configuration 0 places the device in Address state.
+	// This should correspond to the "unconfigured state" required by
+	// libusb when the specified configuration is -1.
+	UCHAR cv = (config < 0) ? 0 : config;
+	if (!UkwSetConfig(priv->dev, cv))
+		return translate_driver_error(GetLastError());
+
+	return LIBUSB_SUCCESS;
+}
+
+static int wince_claim_interface(
+	struct libusb_device_handle *handle,
+	int interface_number)
+{
+	struct wince_device_priv *priv = _device_priv(handle->dev);
+
+	if (!UkwClaimInterface(priv->dev, interface_number))
+		return translate_driver_error(GetLastError());
+
+	return LIBUSB_SUCCESS;
+}
+
+static int wince_release_interface(
+	struct libusb_device_handle *handle,
+	int interface_number)
+{
+	struct wince_device_priv *priv = _device_priv(handle->dev);
+
+	if (!UkwSetInterfaceAlternateSetting(priv->dev, interface_number, 0))
+		return translate_driver_error(GetLastError());
+
+	if (!UkwReleaseInterface(priv->dev, interface_number))
+		return translate_driver_error(GetLastError());
+
+	return LIBUSB_SUCCESS;
+}
+
+static int wince_set_interface_altsetting(
+	struct libusb_device_handle *handle,
+	int interface_number, int altsetting)
+{
+	struct wince_device_priv *priv = _device_priv(handle->dev);
+
+	if (!UkwSetInterfaceAlternateSetting(priv->dev, interface_number, altsetting))
+		return translate_driver_error(GetLastError());
+
+	return LIBUSB_SUCCESS;
+}
+
+static int wince_clear_halt(
+	struct libusb_device_handle *handle,
+	unsigned char endpoint)
+{
+	struct wince_device_priv *priv = _device_priv(handle->dev);
+
+	if (!UkwClearHaltHost(priv->dev, endpoint))
+		return translate_driver_error(GetLastError());
+
+	if (!UkwClearHaltDevice(priv->dev, endpoint))
+		return translate_driver_error(GetLastError());
+
+	return LIBUSB_SUCCESS;
+}
+
+static int wince_reset_device(
+	struct libusb_device_handle *handle)
+{
+	struct wince_device_priv *priv = _device_priv(handle->dev);
+
+	if (!UkwResetDevice(priv->dev))
+		return translate_driver_error(GetLastError());
+
+	return LIBUSB_SUCCESS;
+}
+
+static int wince_kernel_driver_active(
+	struct libusb_device_handle *handle,
+	int interface_number)
+{
+	struct wince_device_priv *priv = _device_priv(handle->dev);
+	BOOL result = FALSE;
+
+	if (!UkwKernelDriverActive(priv->dev, interface_number, &result))
+		return translate_driver_error(GetLastError());
+
+	return result ? 1 : 0;
+}
+
+static int wince_detach_kernel_driver(
+	struct libusb_device_handle *handle,
+	int interface_number)
+{
+	struct wince_device_priv *priv = _device_priv(handle->dev);
+
+	if (!UkwDetachKernelDriver(priv->dev, interface_number))
+		return translate_driver_error(GetLastError());
+
+	return LIBUSB_SUCCESS;
+}
+
+static int wince_attach_kernel_driver(
+	struct libusb_device_handle *handle,
+	int interface_number)
+{
+	struct wince_device_priv *priv = _device_priv(handle->dev);
+
+	if (!UkwAttachKernelDriver(priv->dev, interface_number))
+		return translate_driver_error(GetLastError());
+
+	return LIBUSB_SUCCESS;
+}
+
+static void wince_destroy_device(struct libusb_device *dev)
+{
+	struct wince_device_priv *priv = _device_priv(dev);
+
+	UkwReleaseDeviceList(driver_handle, &priv->dev, 1);
+}
+
+static void wince_clear_transfer_priv(struct usbi_transfer *itransfer)
+{
+	struct wince_transfer_priv *transfer_priv = usbi_transfer_get_os_priv(itransfer);
+	struct winfd wfd = fd_to_winfd(transfer_priv->pollable_fd.fd);
+
+	// No need to cancel transfer as it is either complete or abandoned
+	wfd.itransfer = NULL;
+	CloseHandle(wfd.handle);
+	usbi_free_fd(&transfer_priv->pollable_fd);
+}
+
+static int wince_cancel_transfer(struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	struct wince_device_priv *priv = _device_priv(transfer->dev_handle->dev);
+	struct wince_transfer_priv *transfer_priv = usbi_transfer_get_os_priv(itransfer);
+
+	if (!UkwCancelTransfer(priv->dev, transfer_priv->pollable_fd.overlapped, UKW_TF_NO_WAIT))
+		return translate_driver_error(GetLastError());
+
+	return LIBUSB_SUCCESS;
+}
+
+static int wince_submit_control_or_bulk_transfer(struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	struct libusb_context *ctx = DEVICE_CTX(transfer->dev_handle->dev);
+	struct wince_transfer_priv *transfer_priv = usbi_transfer_get_os_priv(itransfer);
+	struct wince_device_priv *priv = _device_priv(transfer->dev_handle->dev);
+	BOOL direction_in, ret;
+	struct winfd wfd;
+	DWORD flags;
+	HANDLE eventHandle;
+	PUKW_CONTROL_HEADER setup = NULL;
+	const BOOL control_transfer = transfer->type == LIBUSB_TRANSFER_TYPE_CONTROL;
+
+	transfer_priv->pollable_fd = INVALID_WINFD;
+	if (control_transfer) {
+		setup = (PUKW_CONTROL_HEADER) transfer->buffer;
+		direction_in = setup->bmRequestType & LIBUSB_ENDPOINT_IN;
+	} else {
+		direction_in = transfer->endpoint & LIBUSB_ENDPOINT_IN;
+	}
+	flags = direction_in ? UKW_TF_IN_TRANSFER : UKW_TF_OUT_TRANSFER;
+	flags |= UKW_TF_SHORT_TRANSFER_OK;
+
+	eventHandle = CreateEvent(NULL, FALSE, FALSE, NULL);
+	if (eventHandle == NULL) {
+		usbi_err(ctx, "Failed to create event for async transfer");
+		return LIBUSB_ERROR_NO_MEM;
+	}
+
+	wfd = usbi_create_fd(eventHandle, direction_in ? RW_READ : RW_WRITE, itransfer, &wince_cancel_transfer);
+	if (wfd.fd < 0) {
+		CloseHandle(eventHandle);
+		return LIBUSB_ERROR_NO_MEM;
+	}
+
+	transfer_priv->pollable_fd = wfd;
+	if (control_transfer) {
+		// Split out control setup header and data buffer
+		DWORD bufLen = transfer->length - sizeof(UKW_CONTROL_HEADER);
+		PVOID buf = (PVOID) &transfer->buffer[sizeof(UKW_CONTROL_HEADER)];
+
+		ret = UkwIssueControlTransfer(priv->dev, flags, setup, buf, bufLen, &transfer->actual_length, wfd.overlapped);
+	} else {
+		ret = UkwIssueBulkTransfer(priv->dev, flags, transfer->endpoint, transfer->buffer,
+			transfer->length, &transfer->actual_length, wfd.overlapped);
+	}
+
+	if (!ret) {
+		int libusbErr = translate_driver_error(GetLastError());
+		usbi_err(ctx, "UkwIssue%sTransfer failed: error %u",
+			control_transfer ? "Control" : "Bulk", (unsigned int)GetLastError());
+		wince_clear_transfer_priv(itransfer);
+		return libusbErr;
+	}
+	usbi_add_pollfd(ctx, transfer_priv->pollable_fd.fd, direction_in ? POLLIN : POLLOUT);
+
+	return LIBUSB_SUCCESS;
+}
+
+static int wince_submit_iso_transfer(struct usbi_transfer *itransfer)
+{
+	return LIBUSB_ERROR_NOT_SUPPORTED;
+}
+
+static int wince_submit_transfer(struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+
+	switch (transfer->type) {
+	case LIBUSB_TRANSFER_TYPE_CONTROL:
+	case LIBUSB_TRANSFER_TYPE_BULK:
+	case LIBUSB_TRANSFER_TYPE_INTERRUPT:
+		return wince_submit_control_or_bulk_transfer(itransfer);
+	case LIBUSB_TRANSFER_TYPE_ISOCHRONOUS:
+		return wince_submit_iso_transfer(itransfer);
+	case LIBUSB_TRANSFER_TYPE_BULK_STREAM:
+		return LIBUSB_ERROR_NOT_SUPPORTED;
+	default:
+		usbi_err(TRANSFER_CTX(transfer), "unknown endpoint type %d", transfer->type);
+		return LIBUSB_ERROR_INVALID_PARAM;
+	}
+}
+
+static void wince_transfer_callback(
+	struct usbi_transfer *itransfer,
+	uint32_t io_result, uint32_t io_size)
+{
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	struct wince_transfer_priv *transfer_priv = (struct wince_transfer_priv*)usbi_transfer_get_os_priv(itransfer);
+	struct wince_device_priv *priv = _device_priv(transfer->dev_handle->dev);
+	int status;
+
+	usbi_dbg("handling I/O completion with errcode %u", io_result);
+
+	if (io_result == ERROR_NOT_SUPPORTED &&
+		transfer->type != LIBUSB_TRANSFER_TYPE_CONTROL) {
+		/* For functional stalls, the WinCE USB layer (and therefore the USB Kernel Wrapper
+		 * Driver) will report USB_ERROR_STALL/ERROR_NOT_SUPPORTED in situations where the
+		 * endpoint isn't actually stalled.
+		 *
+		 * One example of this is that some devices will occasionally fail to reply to an IN
+		 * token. The WinCE USB layer carries on with the transaction until it is completed
+		 * (or cancelled) but then completes it with USB_ERROR_STALL.
+		 *
+		 * This code therefore needs to confirm that there really is a stall error, by both
+		 * checking the pipe status and requesting the endpoint status from the device.
+		 */
+		BOOL halted = FALSE;
+		usbi_dbg("checking I/O completion with errcode ERROR_NOT_SUPPORTED is really a stall");
+		if (UkwIsPipeHalted(priv->dev, transfer->endpoint, &halted)) {
+			/* Pipe status retrieved, so now request endpoint status by sending a GET_STATUS
+			 * control request to the device. This is done synchronously, which is a bit
+			 * naughty, but this is a special corner case.
+			 */
+			WORD wStatus = 0;
+			DWORD written = 0;
+			UKW_CONTROL_HEADER ctrlHeader;
+			ctrlHeader.bmRequestType = LIBUSB_REQUEST_TYPE_STANDARD |
+				LIBUSB_ENDPOINT_IN | LIBUSB_RECIPIENT_ENDPOINT;
+			ctrlHeader.bRequest = LIBUSB_REQUEST_GET_STATUS;
+			ctrlHeader.wValue = 0;
+			ctrlHeader.wIndex = transfer->endpoint;
+			ctrlHeader.wLength = sizeof(wStatus);
+			if (UkwIssueControlTransfer(priv->dev,
+					UKW_TF_IN_TRANSFER | UKW_TF_SEND_TO_ENDPOINT,
+					&ctrlHeader, &wStatus, sizeof(wStatus), &written, NULL)) {
+				if (written == sizeof(wStatus) &&
+						(wStatus & STATUS_HALT_FLAG) == 0) {
+					if (!halted || UkwClearHaltHost(priv->dev, transfer->endpoint)) {
+						usbi_dbg("Endpoint doesn't appear to be stalled, overriding error with success");
+						io_result = ERROR_SUCCESS;
+					} else {
+						usbi_dbg("Endpoint doesn't appear to be stalled, but the host is halted, changing error");
+						io_result = ERROR_IO_DEVICE;
+					}
+				}
+			}
+		}
+	}
+
+	switch(io_result) {
+	case ERROR_SUCCESS:
+		itransfer->transferred += io_size;
+		status = LIBUSB_TRANSFER_COMPLETED;
+		break;
+	case ERROR_CANCELLED:
+		usbi_dbg("detected transfer cancel");
+		status = LIBUSB_TRANSFER_CANCELLED;
+		break;
+	case ERROR_NOT_SUPPORTED:
+	case ERROR_GEN_FAILURE:
+		usbi_dbg("detected endpoint stall");
+		status = LIBUSB_TRANSFER_STALL;
+		break;
+	case ERROR_SEM_TIMEOUT:
+		usbi_dbg("detected semaphore timeout");
+		status = LIBUSB_TRANSFER_TIMED_OUT;
+		break;
+	case ERROR_OPERATION_ABORTED:
+		usbi_dbg("detected operation aborted");
+		status = LIBUSB_TRANSFER_CANCELLED;
+		break;
+	default:
+		usbi_err(ITRANSFER_CTX(itransfer), "detected I/O error: %s", windows_error_str(io_result));
+		status = LIBUSB_TRANSFER_ERROR;
+		break;
+	}
+
+	wince_clear_transfer_priv(itransfer);
+	if (status == LIBUSB_TRANSFER_CANCELLED)
+		usbi_handle_transfer_cancellation(itransfer);
+	else
+		usbi_handle_transfer_completion(itransfer, (enum libusb_transfer_status)status);
+}
+
+static void wince_handle_callback(
+	struct usbi_transfer *itransfer,
+	uint32_t io_result, uint32_t io_size)
+{
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+
+	switch (transfer->type) {
+	case LIBUSB_TRANSFER_TYPE_CONTROL:
+	case LIBUSB_TRANSFER_TYPE_BULK:
+	case LIBUSB_TRANSFER_TYPE_INTERRUPT:
+	case LIBUSB_TRANSFER_TYPE_ISOCHRONOUS:
+		wince_transfer_callback (itransfer, io_result, io_size);
+		break;
+	case LIBUSB_TRANSFER_TYPE_BULK_STREAM:
+		break;
+	default:
+		usbi_err(ITRANSFER_CTX(itransfer), "unknown endpoint type %d", transfer->type);
+	}
+}
+
+static int wince_handle_events(
+	struct libusb_context *ctx,
+	struct pollfd *fds, POLL_NFDS_TYPE nfds, int num_ready)
+{
+	struct wince_transfer_priv* transfer_priv = NULL;
+	POLL_NFDS_TYPE i = 0;
+	BOOL found = FALSE;
+	struct usbi_transfer *transfer;
+	DWORD io_size, io_result;
+	int r = LIBUSB_SUCCESS;
+
+	usbi_mutex_lock(&ctx->open_devs_lock);
+	for (i = 0; i < nfds && num_ready > 0; i++) {
+
+		usbi_dbg("checking fd %d with revents = %04x", fds[i].fd, fds[i].revents);
+
+		if (!fds[i].revents)
+			continue;
+
+		num_ready--;
+
+		// Because a Windows OVERLAPPED is used for poll emulation,
+		// a pollable fd is created and stored with each transfer
+		usbi_mutex_lock(&ctx->flying_transfers_lock);
+		list_for_each_entry(transfer, &ctx->flying_transfers, list, struct usbi_transfer) {
+			transfer_priv = usbi_transfer_get_os_priv(transfer);
+			if (transfer_priv->pollable_fd.fd == fds[i].fd) {
+				found = TRUE;
+				break;
+			}
+		}
+		usbi_mutex_unlock(&ctx->flying_transfers_lock);
+
+		if (found && HasOverlappedIoCompleted(transfer_priv->pollable_fd.overlapped)) {
+			io_result = (DWORD)transfer_priv->pollable_fd.overlapped->Internal;
+			io_size = (DWORD)transfer_priv->pollable_fd.overlapped->InternalHigh;
+			usbi_remove_pollfd(ctx, transfer_priv->pollable_fd.fd);
+			// let handle_callback free the event using the transfer wfd
+			// If you don't use the transfer wfd, you run a risk of trying to free a
+			// newly allocated wfd that took the place of the one from the transfer.
+			wince_handle_callback(transfer, io_result, io_size);
+		} else if (found) {
+			usbi_err(ctx, "matching transfer for fd %d has not completed", fds[i]);
+			r = LIBUSB_ERROR_OTHER;
+			break;
+		} else {
+			usbi_err(ctx, "could not find a matching transfer for fd %d", fds[i]);
+			r = LIBUSB_ERROR_NOT_FOUND;
+			break;
+		}
+	}
+	usbi_mutex_unlock(&ctx->open_devs_lock);
+
+	return r;
+}
+
+/*
+ * Monotonic and real time functions
+ */
+static int wince_clock_gettime(int clk_id, struct timespec *tp)
+{
+	LARGE_INTEGER hires_counter;
+	ULARGE_INTEGER rtime;
+	FILETIME filetime;
+	SYSTEMTIME st;
+
+	switch(clk_id) {
+	case USBI_CLOCK_MONOTONIC:
+		if (hires_frequency != 0 && QueryPerformanceCounter(&hires_counter)) {
+			tp->tv_sec = (long)(hires_counter.QuadPart / hires_frequency);
+			tp->tv_nsec = (long)(((hires_counter.QuadPart % hires_frequency) / 1000) * hires_ticks_to_ps);
+			return LIBUSB_SUCCESS;
+		}
+		// Fall through and return real-time if monotonic read failed or was not detected @ init
+	case USBI_CLOCK_REALTIME:
+		// We follow http://msdn.microsoft.com/en-us/library/ms724928%28VS.85%29.aspx
+		// with a predef epoch time to have an epoch that starts at 1970.01.01 00:00
+		// Note however that our resolution is bounded by the Windows system time
+		// functions and is at best of the order of 1 ms (or, usually, worse)
+		GetSystemTime(&st);
+		SystemTimeToFileTime(&st, &filetime);
+		rtime.LowPart = filetime.dwLowDateTime;
+		rtime.HighPart = filetime.dwHighDateTime;
+		rtime.QuadPart -= EPOCH_TIME;
+		tp->tv_sec = (long)(rtime.QuadPart / 10000000);
+		tp->tv_nsec = (long)((rtime.QuadPart % 10000000)*100);
+		return LIBUSB_SUCCESS;
+	default:
+		return LIBUSB_ERROR_INVALID_PARAM;
+	}
+}
+
+const struct usbi_os_backend wince_backend = {
+	"Windows CE",
+	0,
+	wince_init,
+	wince_exit,
+
+	wince_get_device_list,
+	NULL,				/* hotplug_poll */
+	wince_open,
+	wince_close,
+
+	wince_get_device_descriptor,
+	wince_get_active_config_descriptor,
+	wince_get_config_descriptor,
+	NULL,				/* get_config_descriptor_by_value() */
+
+	wince_get_configuration,
+	wince_set_configuration,
+	wince_claim_interface,
+	wince_release_interface,
+
+	wince_set_interface_altsetting,
+	wince_clear_halt,
+	wince_reset_device,
+
+	NULL,				/* alloc_streams */
+	NULL,				/* free_streams */
+
+	NULL,				/* dev_mem_alloc() */
+	NULL,				/* dev_mem_free() */
+
+	wince_kernel_driver_active,
+	wince_detach_kernel_driver,
+	wince_attach_kernel_driver,
+
+	wince_destroy_device,
+
+	wince_submit_transfer,
+	wince_cancel_transfer,
+	wince_clear_transfer_priv,
+
+	wince_handle_events,
+	NULL,				/* handle_transfer_completion() */
+
+	wince_clock_gettime,
+	sizeof(struct wince_device_priv),
+	0,
+	sizeof(struct wince_transfer_priv),
+};
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/wince_usb.h b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/wince_usb.h
new file mode 100644
index 000000000..edcb9fcc4
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/wince_usb.h
@@ -0,0 +1,126 @@
+/*
+ * Windows CE backend for libusb 1.0
+ * Copyright © 2011-2013 RealVNC Ltd.
+ * Portions taken from Windows backend, which is
+ * Copyright © 2009-2010 Pete Batard <pbatard@gmail.com>
+ * With contributions from Michael Plante, Orin Eman et al.
+ * Parts of this code adapted from libusb-win32-v1 by Stephan Meyer
+ * Major code testing contribution by Xiaofan Chen
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+#pragma once
+
+#include "windows_common.h"
+
+#include <windows.h>
+#include "poll_windows.h"
+
+#define MAX_DEVICE_COUNT            256
+
+// This is a modified dump of the types in the ceusbkwrapper.h library header
+// with functions transformed into extern pointers.
+//
+// This backend dynamically loads ceusbkwrapper.dll and doesn't include
+// ceusbkwrapper.h directly to simplify the build process. The kernel
+// side wrapper driver is built using the platform image build tools,
+// which makes it difficult to reference directly from the libusb build
+// system.
+struct UKW_DEVICE_PRIV;
+typedef struct UKW_DEVICE_PRIV *UKW_DEVICE;
+typedef UKW_DEVICE *PUKW_DEVICE, *LPUKW_DEVICE;
+
+typedef struct {
+	UINT8 bLength;
+	UINT8 bDescriptorType;
+	UINT16 bcdUSB;
+	UINT8 bDeviceClass;
+	UINT8 bDeviceSubClass;
+	UINT8 bDeviceProtocol;
+	UINT8 bMaxPacketSize0;
+	UINT16 idVendor;
+	UINT16 idProduct;
+	UINT16 bcdDevice;
+	UINT8 iManufacturer;
+	UINT8 iProduct;
+	UINT8 iSerialNumber;
+	UINT8 bNumConfigurations;
+} UKW_DEVICE_DESCRIPTOR, *PUKW_DEVICE_DESCRIPTOR, *LPUKW_DEVICE_DESCRIPTOR;
+
+typedef struct {
+	UINT8 bmRequestType;
+	UINT8 bRequest;
+	UINT16 wValue;
+	UINT16 wIndex;
+	UINT16 wLength;
+} UKW_CONTROL_HEADER, *PUKW_CONTROL_HEADER, *LPUKW_CONTROL_HEADER;
+
+// Collection of flags which can be used when issuing transfer requests
+/* Indicates that the transfer direction is 'in' */
+#define UKW_TF_IN_TRANSFER        0x00000001
+/* Indicates that the transfer direction is 'out' */
+#define UKW_TF_OUT_TRANSFER       0x00000000
+/* Specifies that the transfer should complete as soon as possible,
+ * even if no OVERLAPPED structure has been provided. */
+#define UKW_TF_NO_WAIT            0x00000100
+/* Indicates that transfers shorter than the buffer are ok */
+#define UKW_TF_SHORT_TRANSFER_OK  0x00000200
+#define UKW_TF_SEND_TO_DEVICE     0x00010000
+#define UKW_TF_SEND_TO_INTERFACE  0x00020000
+#define UKW_TF_SEND_TO_ENDPOINT   0x00040000
+/* Don't block when waiting for memory allocations */
+#define UKW_TF_DONT_BLOCK_FOR_MEM 0x00080000
+
+/* Value to use when dealing with configuration values, such as UkwGetConfigDescriptor, 
+ * to specify the currently active configuration for the device. */
+#define UKW_ACTIVE_CONFIGURATION -1
+
+DLL_DECLARE_HANDLE(ceusbkwrapper);
+DLL_DECLARE_FUNC(WINAPI, HANDLE, UkwOpenDriver, ());
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwGetDeviceList, (HANDLE, LPUKW_DEVICE, DWORD, LPDWORD));
+DLL_DECLARE_FUNC(WINAPI, void, UkwReleaseDeviceList, (HANDLE, LPUKW_DEVICE, DWORD));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwGetDeviceAddress, (UKW_DEVICE, unsigned char*, unsigned char*, unsigned long*));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwGetDeviceDescriptor, (UKW_DEVICE, LPUKW_DEVICE_DESCRIPTOR));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwGetConfigDescriptor, (UKW_DEVICE, DWORD, LPVOID, DWORD, LPDWORD));
+DLL_DECLARE_FUNC(WINAPI, void, UkwCloseDriver, (HANDLE));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwCancelTransfer, (UKW_DEVICE, LPOVERLAPPED, DWORD));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwIssueControlTransfer, (UKW_DEVICE, DWORD, LPUKW_CONTROL_HEADER, LPVOID, DWORD, LPDWORD, LPOVERLAPPED));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwClaimInterface, (UKW_DEVICE, DWORD));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwReleaseInterface, (UKW_DEVICE, DWORD));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwSetInterfaceAlternateSetting, (UKW_DEVICE, DWORD, DWORD));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwClearHaltHost, (UKW_DEVICE, UCHAR));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwClearHaltDevice, (UKW_DEVICE, UCHAR));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwGetConfig, (UKW_DEVICE, PUCHAR));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwSetConfig, (UKW_DEVICE, UCHAR));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwResetDevice, (UKW_DEVICE));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwKernelDriverActive, (UKW_DEVICE, DWORD, PBOOL));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwAttachKernelDriver, (UKW_DEVICE, DWORD));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwDetachKernelDriver, (UKW_DEVICE, DWORD));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwIssueBulkTransfer, (UKW_DEVICE, DWORD, UCHAR, LPVOID, DWORD, LPDWORD, LPOVERLAPPED));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwIsPipeHalted, (UKW_DEVICE, UCHAR, LPBOOL));
+
+// Used to determine if an endpoint status really is halted on a failed transfer.
+#define STATUS_HALT_FLAG 0x1
+
+struct wince_device_priv {
+	UKW_DEVICE dev;
+	UKW_DEVICE_DESCRIPTOR desc;
+};
+
+struct wince_transfer_priv {
+	struct winfd pollable_fd;
+	uint8_t interface_number;
+};
+
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/windows_common.h b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/windows_common.h
new file mode 100644
index 000000000..55344ca26
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/windows_common.h
@@ -0,0 +1,124 @@
+/*
+ * Windows backend common header for libusb 1.0
+ *
+ * This file brings together header code common between
+ * the desktop Windows and Windows CE backends.
+ * Copyright © 2012-2013 RealVNC Ltd.
+ * Copyright © 2009-2012 Pete Batard <pete@akeo.ie>
+ * With contributions from Michael Plante, Orin Eman et al.
+ * Parts of this code adapted from libusb-win32-v1 by Stephan Meyer
+ * Major code testing contribution by Xiaofan Chen
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#pragma once
+
+// Windows API default is uppercase - ugh!
+#if !defined(bool)
+#define bool BOOL
+#endif
+#if !defined(true)
+#define true TRUE
+#endif
+#if !defined(false)
+#define false FALSE
+#endif
+
+#define EPOCH_TIME	UINT64_C(116444736000000000)	// 1970.01.01 00:00:000 in MS Filetime
+
+#if defined(__CYGWIN__ )
+#define _stricmp strcasecmp
+#define _strdup strdup
+// _beginthreadex is MSVCRT => unavailable for cygwin. Fallback to using CreateThread
+#define _beginthreadex(a, b, c, d, e, f) CreateThread(a, b, (LPTHREAD_START_ROUTINE)c, d, e, (LPDWORD)f)
+#endif
+
+#define safe_free(p) do {if (p != NULL) {free((void *)p); p = NULL;}} while (0)
+
+#ifndef ARRAYSIZE
+#define ARRAYSIZE(A) (sizeof(A)/sizeof((A)[0]))
+#endif
+
+#define ERR_BUFFER_SIZE	256
+
+/*
+ * API macros - leveraged from libusb-win32 1.x
+ */
+#ifndef _WIN32_WCE
+#define DLL_STRINGIFY(s) #s
+#define DLL_LOAD_LIBRARY(name) LoadLibraryA(DLL_STRINGIFY(name))
+#else
+#define DLL_STRINGIFY(s) L#s
+#define DLL_LOAD_LIBRARY(name) LoadLibrary(DLL_STRINGIFY(name))
+#endif
+
+/*
+ * Macros for handling DLL themselves
+ */
+#define DLL_DECLARE_HANDLE(name)				\
+	static HMODULE __dll_##name##_handle = NULL
+
+#define DLL_GET_HANDLE(name)					\
+	do {							\
+		__dll_##name##_handle = DLL_LOAD_LIBRARY(name);	\
+		if (!__dll_##name##_handle)			\
+			return LIBUSB_ERROR_OTHER;		\
+	} while (0)
+
+#define DLL_FREE_HANDLE(name)					\
+	do {							\
+		if (__dll_##name##_handle) {			\
+			FreeLibrary(__dll_##name##_handle);	\
+			__dll_##name##_handle = NULL;		\
+		}						\
+	} while(0)
+
+
+/*
+ * Macros for handling functions within a DLL
+ */
+#define DLL_DECLARE_FUNC_PREFIXNAME(api, ret, prefixname, name, args)	\
+	typedef ret (api * __dll_##name##_func_t)args;			\
+	static __dll_##name##_func_t prefixname = NULL
+
+#define DLL_DECLARE_FUNC(api, ret, name, args)				\
+	DLL_DECLARE_FUNC_PREFIXNAME(api, ret, name, name, args)
+#define DLL_DECLARE_FUNC_PREFIXED(api, ret, prefix, name, args)		\
+	DLL_DECLARE_FUNC_PREFIXNAME(api, ret, prefix##name, name, args)
+
+#define DLL_LOAD_FUNC_PREFIXNAME(dll, prefixname, name, ret_on_failure)	\
+	do {								\
+		HMODULE h = __dll_##dll##_handle;			\
+		prefixname = (__dll_##name##_func_t)GetProcAddress(h,	\
+				DLL_STRINGIFY(name));			\
+		if (prefixname)						\
+			break;						\
+		prefixname = (__dll_##name##_func_t)GetProcAddress(h,	\
+				DLL_STRINGIFY(name) DLL_STRINGIFY(A));	\
+		if (prefixname)						\
+			break;						\
+		prefixname = (__dll_##name##_func_t)GetProcAddress(h,	\
+				DLL_STRINGIFY(name) DLL_STRINGIFY(W));	\
+		if (prefixname)						\
+			break;						\
+		if (ret_on_failure)					\
+			return LIBUSB_ERROR_NOT_FOUND;			\
+	} while(0)
+
+#define DLL_LOAD_FUNC(dll, name, ret_on_failure)			\
+	DLL_LOAD_FUNC_PREFIXNAME(dll, name, name, ret_on_failure)
+#define DLL_LOAD_FUNC_PREFIXED(dll, prefix, name, ret_on_failure)	\
+	DLL_LOAD_FUNC_PREFIXNAME(dll, prefix##name, name, ret_on_failure)
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/windows_nt_common.c b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/windows_nt_common.c
new file mode 100644
index 000000000..d935394a6
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/windows_nt_common.c
@@ -0,0 +1,591 @@
+/*
+ * windows backend for libusb 1.0
+ * Copyright © 2009-2012 Pete Batard <pete@akeo.ie>
+ * With contributions from Michael Plante, Orin Eman et al.
+ * Parts of this code adapted from libusb-win32-v1 by Stephan Meyer
+ * HID Reports IOCTLs inspired from HIDAPI by Alan Ott, Signal 11 Software
+ * Hash table functions adapted from glibc, by Ulrich Drepper et al.
+ * Major code testing contribution by Xiaofan Chen
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <config.h>
+
+#include <inttypes.h>
+#include <process.h>
+#include <stdio.h>
+
+#include "libusbi.h"
+#include "windows_common.h"
+#include "windows_nt_common.h"
+
+// Global variables for clock_gettime mechanism
+static uint64_t hires_ticks_to_ps;
+static uint64_t hires_frequency;
+
+#define TIMER_REQUEST_RETRY_MS	100
+#define WM_TIMER_REQUEST	(WM_USER + 1)
+#define WM_TIMER_EXIT		(WM_USER + 2)
+
+// used for monotonic clock_gettime()
+struct timer_request {
+	struct timespec *tp;
+	HANDLE event;
+};
+
+// Timer thread
+static HANDLE timer_thread = NULL;
+static DWORD timer_thread_id = 0;
+
+/* User32 dependencies */
+DLL_DECLARE_HANDLE(User32);
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, BOOL, p, GetMessageA, (LPMSG, HWND, UINT, UINT));
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, BOOL, p, PeekMessageA, (LPMSG, HWND, UINT, UINT, UINT));
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, BOOL, p, PostThreadMessageA, (DWORD, UINT, WPARAM, LPARAM));
+
+static unsigned __stdcall windows_clock_gettime_threaded(void *param);
+
+/*
+* Converts a windows error to human readable string
+* uses retval as errorcode, or, if 0, use GetLastError()
+*/
+#if defined(ENABLE_LOGGING)
+const char *windows_error_str(DWORD error_code)
+{
+	static char err_string[ERR_BUFFER_SIZE];
+
+	DWORD size;
+	int len;
+
+	if (error_code == 0)
+		error_code = GetLastError();
+
+	len = sprintf(err_string, "[%u] ", (unsigned int)error_code);
+
+	// Translate codes returned by SetupAPI. The ones we are dealing with are either
+	// in 0x0000xxxx or 0xE000xxxx and can be distinguished from standard error codes.
+	// See http://msdn.microsoft.com/en-us/library/windows/hardware/ff545011.aspx
+	switch (error_code & 0xE0000000) {
+	case 0:
+		error_code = HRESULT_FROM_WIN32(error_code); // Still leaves ERROR_SUCCESS unmodified
+		break;
+	case 0xE0000000:
+		error_code = 0x80000000 | (FACILITY_SETUPAPI << 16) | (error_code & 0x0000FFFF);
+		break;
+	default:
+		break;
+	}
+
+	size = FormatMessageA(FORMAT_MESSAGE_FROM_SYSTEM|FORMAT_MESSAGE_IGNORE_INSERTS,
+			NULL, error_code, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
+			&err_string[len], ERR_BUFFER_SIZE - len, NULL);
+	if (size == 0) {
+		DWORD format_error = GetLastError();
+		if (format_error)
+			snprintf(err_string, ERR_BUFFER_SIZE,
+				"Windows error code %u (FormatMessage error code %u)",
+				(unsigned int)error_code, (unsigned int)format_error);
+		else
+			snprintf(err_string, ERR_BUFFER_SIZE, "Unknown error code %u", (unsigned int)error_code);
+	} else {
+		// Remove CRLF from end of message, if present
+		size_t pos = len + size - 2;
+		if (err_string[pos] == '\r')
+			err_string[pos] = '\0';
+	}
+
+	return err_string;
+}
+#endif
+
+/* Hash table functions - modified From glibc 2.3.2:
+   [Aho,Sethi,Ullman] Compilers: Principles, Techniques and Tools, 1986
+   [Knuth]            The Art of Computer Programming, part 3 (6.4)  */
+
+#define HTAB_SIZE 1021UL	// *MUST* be a prime number!!
+
+typedef struct htab_entry {
+	unsigned long used;
+	char *str;
+} htab_entry;
+
+static htab_entry *htab_table = NULL;
+static usbi_mutex_t htab_mutex = NULL;
+static unsigned long htab_filled;
+
+/* Before using the hash table we must allocate memory for it.
+   We allocate one element more as the found prime number says.
+   This is done for more effective indexing as explained in the
+   comment for the hash function.  */
+static bool htab_create(struct libusb_context *ctx)
+{
+	if (htab_table != NULL) {
+		usbi_err(ctx, "hash table already allocated");
+		return true;
+	}
+
+	// Create a mutex
+	usbi_mutex_init(&htab_mutex);
+
+	usbi_dbg("using %lu entries hash table", HTAB_SIZE);
+	htab_filled = 0;
+
+	// allocate memory and zero out.
+	htab_table = calloc(HTAB_SIZE + 1, sizeof(htab_entry));
+	if (htab_table == NULL) {
+		usbi_err(ctx, "could not allocate space for hash table");
+		return false;
+	}
+
+	return true;
+}
+
+/* After using the hash table it has to be destroyed.  */
+static void htab_destroy(void)
+{
+	unsigned long i;
+
+	if (htab_table == NULL)
+		return;
+
+	for (i = 0; i < HTAB_SIZE; i++)
+		free(htab_table[i].str);
+
+	safe_free(htab_table);
+
+	usbi_mutex_destroy(&htab_mutex);
+}
+
+/* This is the search function. It uses double hashing with open addressing.
+   We use a trick to speed up the lookup. The table is created with one
+   more element available. This enables us to use the index zero special.
+   This index will never be used because we store the first hash index in
+   the field used where zero means not used. Every other value means used.
+   The used field can be used as a first fast comparison for equality of
+   the stored and the parameter value. This helps to prevent unnecessary
+   expensive calls of strcmp.  */
+unsigned long htab_hash(const char *str)
+{
+	unsigned long hval, hval2;
+	unsigned long idx;
+	unsigned long r = 5381;
+	int c;
+	const char *sz = str;
+
+	if (str == NULL)
+		return 0;
+
+	// Compute main hash value (algorithm suggested by Nokia)
+	while ((c = *sz++) != 0)
+		r = ((r << 5) + r) + c;
+	if (r == 0)
+		++r;
+
+	// compute table hash: simply take the modulus
+	hval = r % HTAB_SIZE;
+	if (hval == 0)
+		++hval;
+
+	// Try the first index
+	idx = hval;
+
+	// Mutually exclusive access (R/W lock would be better)
+	usbi_mutex_lock(&htab_mutex);
+
+	if (htab_table[idx].used) {
+		if ((htab_table[idx].used == hval) && (strcmp(str, htab_table[idx].str) == 0))
+			goto out_unlock; // existing hash
+
+		usbi_dbg("hash collision ('%s' vs '%s')", str, htab_table[idx].str);
+
+		// Second hash function, as suggested in [Knuth]
+		hval2 = 1 + hval % (HTAB_SIZE - 2);
+
+		do {
+			// Because size is prime this guarantees to step through all available indexes
+			if (idx <= hval2)
+				idx = HTAB_SIZE + idx - hval2;
+			else
+				idx -= hval2;
+
+			// If we visited all entries leave the loop unsuccessfully
+			if (idx == hval)
+				break;
+
+			// If entry is found use it.
+			if ((htab_table[idx].used == hval) && (strcmp(str, htab_table[idx].str) == 0))
+				goto out_unlock;
+		} while (htab_table[idx].used);
+	}
+
+	// Not found => New entry
+
+	// If the table is full return an error
+	if (htab_filled >= HTAB_SIZE) {
+		usbi_err(NULL, "hash table is full (%lu entries)", HTAB_SIZE);
+		idx = 0;
+		goto out_unlock;
+	}
+
+	htab_table[idx].str = _strdup(str);
+	if (htab_table[idx].str == NULL) {
+		usbi_err(NULL, "could not duplicate string for hash table");
+		idx = 0;
+		goto out_unlock;
+	}
+
+	htab_table[idx].used = hval;
+	++htab_filled;
+
+out_unlock:
+	usbi_mutex_unlock(&htab_mutex);
+
+	return idx;
+}
+
+static int windows_init_dlls(void)
+{
+	DLL_GET_HANDLE(User32);
+	DLL_LOAD_FUNC_PREFIXED(User32, p, GetMessageA, TRUE);
+	DLL_LOAD_FUNC_PREFIXED(User32, p, PeekMessageA, TRUE);
+	DLL_LOAD_FUNC_PREFIXED(User32, p, PostThreadMessageA, TRUE);
+
+	return LIBUSB_SUCCESS;
+}
+
+static void windows_exit_dlls(void)
+{
+	DLL_FREE_HANDLE(User32);
+}
+
+static bool windows_init_clock(struct libusb_context *ctx)
+{
+	DWORD_PTR affinity, dummy;
+	HANDLE event = NULL;
+	LARGE_INTEGER li_frequency;
+	int i;
+
+	if (QueryPerformanceFrequency(&li_frequency)) {
+		// Load DLL imports
+		if (windows_init_dlls() != LIBUSB_SUCCESS) {
+			usbi_err(ctx, "could not resolve DLL functions");
+			return false;
+		}
+
+		// The hires frequency can go as high as 4 GHz, so we'll use a conversion
+		// to picoseconds to compute the tv_nsecs part in clock_gettime
+		hires_frequency = li_frequency.QuadPart;
+		hires_ticks_to_ps = UINT64_C(1000000000000) / hires_frequency;
+		usbi_dbg("hires timer available (Frequency: %"PRIu64" Hz)", hires_frequency);
+
+		// Because QueryPerformanceCounter might report different values when
+		// running on different cores, we create a separate thread for the timer
+		// calls, which we glue to the first available core always to prevent timing discrepancies.
+		if (!GetProcessAffinityMask(GetCurrentProcess(), &affinity, &dummy) || (affinity == 0)) {
+			usbi_err(ctx, "could not get process affinity: %s", windows_error_str(0));
+			return false;
+		}
+
+		// The process affinity mask is a bitmask where each set bit represents a core on
+		// which this process is allowed to run, so we find the first set bit
+		for (i = 0; !(affinity & (DWORD_PTR)(1 << i)); i++);
+		affinity = (DWORD_PTR)(1 << i);
+
+		usbi_dbg("timer thread will run on core #%d", i);
+
+		event = CreateEvent(NULL, FALSE, FALSE, NULL);
+		if (event == NULL) {
+			usbi_err(ctx, "could not create event: %s", windows_error_str(0));
+			return false;
+		}
+
+		timer_thread = (HANDLE)_beginthreadex(NULL, 0, windows_clock_gettime_threaded, (void *)event,
+				0, (unsigned int *)&timer_thread_id);
+		if (timer_thread == NULL) {
+			usbi_err(ctx, "unable to create timer thread - aborting");
+			CloseHandle(event);
+			return false;
+		}
+
+		if (!SetThreadAffinityMask(timer_thread, affinity))
+			usbi_warn(ctx, "unable to set timer thread affinity, timer discrepancies may arise");
+
+		// Wait for timer thread to init before continuing.
+		if (WaitForSingleObject(event, INFINITE) != WAIT_OBJECT_0) {
+			usbi_err(ctx, "failed to wait for timer thread to become ready - aborting");
+			CloseHandle(event);
+			return false;
+		}
+
+		CloseHandle(event);
+	} else {
+		usbi_dbg("no hires timer available on this platform");
+		hires_frequency = 0;
+		hires_ticks_to_ps = UINT64_C(0);
+	}
+
+	return true;
+}
+
+void windows_destroy_clock(void)
+{
+	if (timer_thread) {
+		// actually the signal to quit the thread.
+		if (!pPostThreadMessageA(timer_thread_id, WM_TIMER_EXIT, 0, 0)
+				|| (WaitForSingleObject(timer_thread, INFINITE) != WAIT_OBJECT_0)) {
+			usbi_dbg("could not wait for timer thread to quit");
+			TerminateThread(timer_thread, 1);
+			// shouldn't happen, but we're destroying
+			// all objects it might have held anyway.
+		}
+		CloseHandle(timer_thread);
+		timer_thread = NULL;
+		timer_thread_id = 0;
+	}
+}
+
+/*
+* Monotonic and real time functions
+*/
+static unsigned __stdcall windows_clock_gettime_threaded(void *param)
+{
+	struct timer_request *request;
+	LARGE_INTEGER hires_counter;
+	MSG msg;
+
+	// The following call will create this thread's message queue
+	// See https://msdn.microsoft.com/en-us/library/windows/desktop/ms644946.aspx
+	pPeekMessageA(&msg, NULL, WM_USER, WM_USER, PM_NOREMOVE);
+
+	// Signal windows_init_clock() that we're ready to service requests
+	if (!SetEvent((HANDLE)param))
+		usbi_dbg("SetEvent failed for timer init event: %s", windows_error_str(0));
+	param = NULL;
+
+	// Main loop - wait for requests
+	while (1) {
+		if (pGetMessageA(&msg, NULL, WM_TIMER_REQUEST, WM_TIMER_EXIT) == -1) {
+			usbi_err(NULL, "GetMessage failed for timer thread: %s", windows_error_str(0));
+			return 1;
+		}
+
+		switch (msg.message) {
+		case WM_TIMER_REQUEST:
+			// Requests to this thread are for hires always
+			// Microsoft says that this function always succeeds on XP and later
+			// See https://msdn.microsoft.com/en-us/library/windows/desktop/ms644904.aspx
+			request = (struct timer_request *)msg.lParam;
+			QueryPerformanceCounter(&hires_counter);
+			request->tp->tv_sec = (long)(hires_counter.QuadPart / hires_frequency);
+			request->tp->tv_nsec = (long)(((hires_counter.QuadPart % hires_frequency) / 1000) * hires_ticks_to_ps);
+			if (!SetEvent(request->event))
+				usbi_err(NULL, "SetEvent failed for timer request: %s", windows_error_str(0));
+			break;
+		case WM_TIMER_EXIT:
+			usbi_dbg("timer thread quitting");
+			return 0;
+		}
+	}
+}
+
+int windows_clock_gettime(int clk_id, struct timespec *tp)
+{
+	struct timer_request request;
+#if !defined(_MSC_VER) || (_MSC_VER < 1900)
+	FILETIME filetime;
+	ULARGE_INTEGER rtime;
+#endif
+	DWORD r;
+
+	switch (clk_id) {
+	case USBI_CLOCK_MONOTONIC:
+		if (timer_thread) {
+			request.tp = tp;
+			request.event = CreateEvent(NULL, FALSE, FALSE, NULL);
+			if (request.event == NULL)
+				return LIBUSB_ERROR_NO_MEM;
+
+			if (!pPostThreadMessageA(timer_thread_id, WM_TIMER_REQUEST, 0, (LPARAM)&request)) {
+				usbi_err(NULL, "PostThreadMessage failed for timer thread: %s", windows_error_str(0));
+				CloseHandle(request.event);
+				return LIBUSB_ERROR_OTHER;
+			}
+
+			do {
+				r = WaitForSingleObject(request.event, TIMER_REQUEST_RETRY_MS);
+				if (r == WAIT_TIMEOUT)
+					usbi_dbg("could not obtain a timer value within reasonable timeframe - too much load?");
+				else if (r == WAIT_FAILED)
+					usbi_err(NULL, "WaitForSingleObject failed: %s", windows_error_str(0));
+			} while (r == WAIT_TIMEOUT);
+			CloseHandle(request.event);
+
+			if (r == WAIT_OBJECT_0)
+				return LIBUSB_SUCCESS;
+			else
+				return LIBUSB_ERROR_OTHER;
+		}
+		// Fall through and return real-time if monotonic was not detected @ timer init
+	case USBI_CLOCK_REALTIME:
+#if defined(_MSC_VER) && (_MSC_VER >= 1900)
+		timespec_get(tp, TIME_UTC);
+#else
+		// We follow http://msdn.microsoft.com/en-us/library/ms724928%28VS.85%29.aspx
+		// with a predef epoch time to have an epoch that starts at 1970.01.01 00:00
+		// Note however that our resolution is bounded by the Windows system time
+		// functions and is at best of the order of 1 ms (or, usually, worse)
+		GetSystemTimeAsFileTime(&filetime);
+		rtime.LowPart = filetime.dwLowDateTime;
+		rtime.HighPart = filetime.dwHighDateTime;
+		rtime.QuadPart -= EPOCH_TIME;
+		tp->tv_sec = (long)(rtime.QuadPart / 10000000);
+		tp->tv_nsec = (long)((rtime.QuadPart % 10000000) * 100);
+#endif
+		return LIBUSB_SUCCESS;
+	default:
+		return LIBUSB_ERROR_INVALID_PARAM;
+	}
+}
+
+static void windows_transfer_callback(struct usbi_transfer *itransfer, uint32_t io_result, uint32_t io_size)
+{
+	int status, istatus;
+
+	usbi_dbg("handling I/O completion with errcode %u, size %u", io_result, io_size);
+
+	switch (io_result) {
+	case NO_ERROR:
+		status = windows_copy_transfer_data(itransfer, io_size);
+		break;
+	case ERROR_GEN_FAILURE:
+		usbi_dbg("detected endpoint stall");
+		status = LIBUSB_TRANSFER_STALL;
+		break;
+	case ERROR_SEM_TIMEOUT:
+		usbi_dbg("detected semaphore timeout");
+		status = LIBUSB_TRANSFER_TIMED_OUT;
+		break;
+	case ERROR_OPERATION_ABORTED:
+		istatus = windows_copy_transfer_data(itransfer, io_size);
+		if (istatus != LIBUSB_TRANSFER_COMPLETED)
+			usbi_dbg("Failed to copy partial data in aborted operation: %d", istatus);
+
+		usbi_dbg("detected operation aborted");
+		status = LIBUSB_TRANSFER_CANCELLED;
+		break;
+	default:
+		usbi_err(ITRANSFER_CTX(itransfer), "detected I/O error %u: %s", io_result, windows_error_str(io_result));
+		status = LIBUSB_TRANSFER_ERROR;
+		break;
+	}
+	windows_clear_transfer_priv(itransfer);	// Cancel polling
+	if (status == LIBUSB_TRANSFER_CANCELLED)
+		usbi_handle_transfer_cancellation(itransfer);
+	else
+		usbi_handle_transfer_completion(itransfer, (enum libusb_transfer_status)status);
+}
+
+void windows_handle_callback(struct usbi_transfer *itransfer, uint32_t io_result, uint32_t io_size)
+{
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+
+	switch (transfer->type) {
+	case LIBUSB_TRANSFER_TYPE_CONTROL:
+	case LIBUSB_TRANSFER_TYPE_BULK:
+	case LIBUSB_TRANSFER_TYPE_INTERRUPT:
+	case LIBUSB_TRANSFER_TYPE_ISOCHRONOUS:
+		windows_transfer_callback(itransfer, io_result, io_size);
+		break;
+	case LIBUSB_TRANSFER_TYPE_BULK_STREAM:
+		usbi_warn(ITRANSFER_CTX(itransfer), "bulk stream transfers are not yet supported on this platform");
+		break;
+	default:
+		usbi_err(ITRANSFER_CTX(itransfer), "unknown endpoint type %d", transfer->type);
+	}
+}
+
+int windows_handle_events(struct libusb_context *ctx, struct pollfd *fds, POLL_NFDS_TYPE nfds, int num_ready)
+{
+	POLL_NFDS_TYPE i;
+	bool found = false;
+	struct usbi_transfer *transfer;
+	struct winfd *pollable_fd = NULL;
+	DWORD io_size, io_result;
+	int r = LIBUSB_SUCCESS;
+
+	usbi_mutex_lock(&ctx->open_devs_lock);
+	for (i = 0; i < nfds && num_ready > 0; i++) {
+
+		usbi_dbg("checking fd %d with revents = %04x", fds[i].fd, fds[i].revents);
+
+		if (!fds[i].revents)
+			continue;
+
+		num_ready--;
+
+		// Because a Windows OVERLAPPED is used for poll emulation,
+		// a pollable fd is created and stored with each transfer
+		usbi_mutex_lock(&ctx->flying_transfers_lock);
+		found = false;
+		list_for_each_entry(transfer, &ctx->flying_transfers, list, struct usbi_transfer) {
+			pollable_fd = windows_get_fd(transfer);
+			if (pollable_fd->fd == fds[i].fd) {
+				found = true;
+				break;
+			}
+		}
+		usbi_mutex_unlock(&ctx->flying_transfers_lock);
+
+		if (found) {
+			windows_get_overlapped_result(transfer, pollable_fd, &io_result, &io_size);
+
+			usbi_remove_pollfd(ctx, pollable_fd->fd);
+			// let handle_callback free the event using the transfer wfd
+			// If you don't use the transfer wfd, you run a risk of trying to free a
+			// newly allocated wfd that took the place of the one from the transfer.
+			windows_handle_callback(transfer, io_result, io_size);
+		} else {
+			usbi_err(ctx, "could not find a matching transfer for fd %d", fds[i]);
+			r = LIBUSB_ERROR_NOT_FOUND;
+			break;
+		}
+	}
+	usbi_mutex_unlock(&ctx->open_devs_lock);
+
+	return r;
+}
+
+int windows_common_init(struct libusb_context *ctx)
+{
+	if (!windows_init_clock(ctx))
+		goto error_roll_back;
+
+	if (!htab_create(ctx))
+		goto error_roll_back;
+
+	return LIBUSB_SUCCESS;
+
+error_roll_back:
+	windows_common_exit();
+	return LIBUSB_ERROR_NO_MEM;
+}
+
+void windows_common_exit(void)
+{
+	htab_destroy();
+	windows_destroy_clock();
+	windows_exit_dlls();
+}
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/windows_nt_common.h b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/windows_nt_common.h
new file mode 100644
index 000000000..52ea8708b
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/windows_nt_common.h
@@ -0,0 +1,63 @@
+/*
+ * Windows backend common header for libusb 1.0
+ *
+ * This file brings together header code common between
+ * the desktop Windows backends.
+ * Copyright © 2012-2013 RealVNC Ltd.
+ * Copyright © 2009-2012 Pete Batard <pete@akeo.ie>
+ * With contributions from Michael Plante, Orin Eman et al.
+ * Parts of this code adapted from libusb-win32-v1 by Stephan Meyer
+ * Major code testing contribution by Xiaofan Chen
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#pragma once
+
+// Missing from MinGW
+#if !defined(FACILITY_SETUPAPI)
+#define FACILITY_SETUPAPI	15
+#endif
+
+typedef struct USB_CONFIGURATION_DESCRIPTOR {
+  UCHAR  bLength;
+  UCHAR  bDescriptorType;
+  USHORT wTotalLength;
+  UCHAR  bNumInterfaces;
+  UCHAR  bConfigurationValue;
+  UCHAR  iConfiguration;
+  UCHAR  bmAttributes;
+  UCHAR  MaxPower;
+} USB_CONFIGURATION_DESCRIPTOR, *PUSB_CONFIGURATION_DESCRIPTOR;
+
+typedef struct libusb_device_descriptor USB_DEVICE_DESCRIPTOR, *PUSB_DEVICE_DESCRIPTOR;
+
+int windows_common_init(struct libusb_context *ctx);
+void windows_common_exit(void);
+
+unsigned long htab_hash(const char *str);
+int windows_clock_gettime(int clk_id, struct timespec *tp);
+
+void windows_clear_transfer_priv(struct usbi_transfer *itransfer);
+int windows_copy_transfer_data(struct usbi_transfer *itransfer, uint32_t io_size);
+struct winfd *windows_get_fd(struct usbi_transfer *transfer);
+void windows_get_overlapped_result(struct usbi_transfer *transfer, struct winfd *pollable_fd, DWORD *io_result, DWORD *io_size);
+
+void windows_handle_callback(struct usbi_transfer *itransfer, uint32_t io_result, uint32_t io_size);
+int windows_handle_events(struct libusb_context *ctx, struct pollfd *fds, POLL_NFDS_TYPE nfds, int num_ready);
+
+#if defined(ENABLE_LOGGING)
+const char *windows_error_str(DWORD error_code);
+#endif
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/windows_usbdk.c b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/windows_usbdk.c
new file mode 100644
index 000000000..7cc579387
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/windows_usbdk.c
@@ -0,0 +1,905 @@
+/*
+ * windows UsbDk backend for libusb 1.0
+ * Copyright © 2014 Red Hat, Inc.
+
+ * Authors:
+ * Dmitry Fleytman <dmitry@daynix.com>
+ * Pavel Gurvich <pavel@daynix.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <config.h>
+
+#if defined(USE_USBDK)
+
+#include <windows.h>
+#include <cfgmgr32.h>
+#include <stdio.h>
+
+#include "libusbi.h"
+#include "windows_common.h"
+#include "windows_nt_common.h"
+
+#define ULONG64 uint64_t
+#define PVOID64 uint64_t
+
+typedef CONST WCHAR *PCWCHAR;
+#define wcsncpy_s wcsncpy
+
+#include "windows_usbdk.h"
+
+#if !defined(STATUS_SUCCESS)
+typedef LONG NTSTATUS;
+#define STATUS_SUCCESS			((NTSTATUS)0x00000000L)
+#endif
+
+#if !defined(STATUS_CANCELLED)
+#define STATUS_CANCELLED		((NTSTATUS)0xC0000120L)
+#endif
+
+#if !defined(STATUS_REQUEST_CANCELED)
+#define STATUS_REQUEST_CANCELED		((NTSTATUS)0xC0000703L)
+#endif
+
+#if !defined(USBD_SUCCESS)
+typedef int32_t USBD_STATUS;
+#define USBD_SUCCESS(Status)		((USBD_STATUS) (Status) >= 0)
+#define USBD_PENDING(Status)		((ULONG) (Status) >> 30 == 1)
+#define USBD_ERROR(Status)		((USBD_STATUS) (Status) < 0)
+#define USBD_STATUS_STALL_PID		((USBD_STATUS) 0xc0000004)
+#define USBD_STATUS_ENDPOINT_HALTED	((USBD_STATUS) 0xc0000030)
+#define USBD_STATUS_BAD_START_FRAME	((USBD_STATUS) 0xc0000a00)
+#define USBD_STATUS_TIMEOUT		((USBD_STATUS) 0xc0006000)
+#define USBD_STATUS_CANCELED		((USBD_STATUS) 0xc0010000)
+#endif
+
+static int concurrent_usage = -1;
+
+struct usbdk_device_priv {
+	USB_DK_DEVICE_INFO info;
+	PUSB_CONFIGURATION_DESCRIPTOR *config_descriptors;
+	HANDLE redirector_handle;
+	uint8_t active_configuration;
+};
+
+struct usbdk_transfer_priv {
+	USB_DK_TRANSFER_REQUEST request;
+	struct winfd pollable_fd;
+	PULONG64 IsochronousPacketsArray;
+	PUSB_DK_ISO_TRANSFER_RESULT IsochronousResultsArray;
+};
+
+static inline struct usbdk_device_priv *_usbdk_device_priv(struct libusb_device *dev)
+{
+	return (struct usbdk_device_priv *)dev->os_priv;
+}
+
+static inline struct usbdk_transfer_priv *_usbdk_transfer_priv(struct usbi_transfer *itransfer)
+{
+	return (struct usbdk_transfer_priv *)usbi_transfer_get_os_priv(itransfer);
+}
+
+static struct {
+	HMODULE module;
+
+	USBDK_GET_DEVICES_LIST			GetDevicesList;
+	USBDK_RELEASE_DEVICES_LIST		ReleaseDevicesList;
+	USBDK_START_REDIRECT			StartRedirect;
+	USBDK_STOP_REDIRECT			StopRedirect;
+	USBDK_GET_CONFIGURATION_DESCRIPTOR	GetConfigurationDescriptor;
+	USBDK_RELEASE_CONFIGURATION_DESCRIPTOR	ReleaseConfigurationDescriptor;
+	USBDK_READ_PIPE				ReadPipe;
+	USBDK_WRITE_PIPE			WritePipe;
+	USBDK_ABORT_PIPE			AbortPipe;
+	USBDK_RESET_PIPE			ResetPipe;
+	USBDK_SET_ALTSETTING			SetAltsetting;
+	USBDK_RESET_DEVICE			ResetDevice;
+	USBDK_GET_REDIRECTOR_SYSTEM_HANDLE	GetRedirectorSystemHandle;
+} usbdk_helper;
+
+static FARPROC get_usbdk_proc_addr(struct libusb_context *ctx, LPCSTR api_name)
+{
+	FARPROC api_ptr = GetProcAddress(usbdk_helper.module, api_name);
+
+	if (api_ptr == NULL)
+		usbi_err(ctx, "UsbDkHelper API %s not found, error %d", api_name, GetLastError());
+
+	return api_ptr;
+}
+
+static void unload_usbdk_helper_dll(void)
+{
+	if (usbdk_helper.module != NULL) {
+		FreeLibrary(usbdk_helper.module);
+		usbdk_helper.module = NULL;
+	}
+}
+
+static int load_usbdk_helper_dll(struct libusb_context *ctx)
+{
+	usbdk_helper.module = LoadLibraryA("UsbDkHelper");
+	if (usbdk_helper.module == NULL) {
+		usbi_err(ctx, "Failed to load UsbDkHelper.dll, error %d", GetLastError());
+		return LIBUSB_ERROR_NOT_FOUND;
+	}
+
+	usbdk_helper.GetDevicesList = (USBDK_GET_DEVICES_LIST)get_usbdk_proc_addr(ctx, "UsbDk_GetDevicesList");
+	if (usbdk_helper.GetDevicesList == NULL)
+		goto error_unload;
+
+	usbdk_helper.ReleaseDevicesList = (USBDK_RELEASE_DEVICES_LIST)get_usbdk_proc_addr(ctx, "UsbDk_ReleaseDevicesList");
+	if (usbdk_helper.ReleaseDevicesList == NULL)
+		goto error_unload;
+
+	usbdk_helper.StartRedirect = (USBDK_START_REDIRECT)get_usbdk_proc_addr(ctx, "UsbDk_StartRedirect");
+	if (usbdk_helper.StartRedirect == NULL)
+		goto error_unload;
+
+	usbdk_helper.StopRedirect = (USBDK_STOP_REDIRECT)get_usbdk_proc_addr(ctx, "UsbDk_StopRedirect");
+	if (usbdk_helper.StopRedirect == NULL)
+		goto error_unload;
+
+	usbdk_helper.GetConfigurationDescriptor = (USBDK_GET_CONFIGURATION_DESCRIPTOR)get_usbdk_proc_addr(ctx, "UsbDk_GetConfigurationDescriptor");
+	if (usbdk_helper.GetConfigurationDescriptor == NULL)
+		goto error_unload;
+
+	usbdk_helper.ReleaseConfigurationDescriptor = (USBDK_RELEASE_CONFIGURATION_DESCRIPTOR)get_usbdk_proc_addr(ctx, "UsbDk_ReleaseConfigurationDescriptor");
+	if (usbdk_helper.ReleaseConfigurationDescriptor == NULL)
+		goto error_unload;
+
+	usbdk_helper.ReadPipe = (USBDK_READ_PIPE)get_usbdk_proc_addr(ctx, "UsbDk_ReadPipe");
+	if (usbdk_helper.ReadPipe == NULL)
+		goto error_unload;
+
+	usbdk_helper.WritePipe = (USBDK_WRITE_PIPE)get_usbdk_proc_addr(ctx, "UsbDk_WritePipe");
+	if (usbdk_helper.WritePipe == NULL)
+		goto error_unload;
+
+	usbdk_helper.AbortPipe = (USBDK_ABORT_PIPE)get_usbdk_proc_addr(ctx, "UsbDk_AbortPipe");
+	if (usbdk_helper.AbortPipe == NULL)
+		goto error_unload;
+
+	usbdk_helper.ResetPipe = (USBDK_RESET_PIPE)get_usbdk_proc_addr(ctx, "UsbDk_ResetPipe");
+	if (usbdk_helper.ResetPipe == NULL)
+		goto error_unload;
+
+	usbdk_helper.SetAltsetting = (USBDK_SET_ALTSETTING)get_usbdk_proc_addr(ctx, "UsbDk_SetAltsetting");
+	if (usbdk_helper.SetAltsetting == NULL)
+		goto error_unload;
+
+	usbdk_helper.ResetDevice = (USBDK_RESET_DEVICE)get_usbdk_proc_addr(ctx, "UsbDk_ResetDevice");
+	if (usbdk_helper.ResetDevice == NULL)
+		goto error_unload;
+
+	usbdk_helper.GetRedirectorSystemHandle = (USBDK_GET_REDIRECTOR_SYSTEM_HANDLE)get_usbdk_proc_addr(ctx, "UsbDk_GetRedirectorSystemHandle");
+	if (usbdk_helper.GetRedirectorSystemHandle == NULL)
+		goto error_unload;
+
+	return LIBUSB_SUCCESS;
+
+error_unload:
+	FreeLibrary(usbdk_helper.module);
+	usbdk_helper.module = NULL;
+	return LIBUSB_ERROR_NOT_FOUND;
+}
+
+static int usbdk_init(struct libusb_context *ctx)
+{
+	int r;
+
+	if (++concurrent_usage == 0) { // First init?
+		r = load_usbdk_helper_dll(ctx);
+		if (r)
+			goto init_exit;
+
+		init_polling();
+
+		r = windows_common_init(ctx);
+		if (r)
+			goto init_exit;
+	}
+	// At this stage, either we went through full init successfully, or didn't need to
+	r = LIBUSB_SUCCESS;
+
+init_exit:
+	if (!concurrent_usage && r != LIBUSB_SUCCESS) { // First init failed?
+		exit_polling();
+		windows_common_exit();
+		unload_usbdk_helper_dll();
+	}
+
+	if (r != LIBUSB_SUCCESS)
+		--concurrent_usage; // Not expected to call libusb_exit if we failed.
+
+	return r;
+}
+
+static int usbdk_get_session_id_for_device(struct libusb_context *ctx,
+	PUSB_DK_DEVICE_ID id, unsigned long *session_id)
+{
+	char dev_identity[ARRAYSIZE(id->DeviceID) + ARRAYSIZE(id->InstanceID)];
+
+	if (sprintf(dev_identity, "%S%S", id->DeviceID, id->InstanceID) == -1) {
+		usbi_warn(ctx, "cannot form device identity", id->DeviceID);
+		return LIBUSB_ERROR_NOT_SUPPORTED;
+	}
+
+	*session_id = htab_hash(dev_identity);
+
+	return LIBUSB_SUCCESS;
+}
+
+static void usbdk_release_config_descriptors(struct usbdk_device_priv *p, uint8_t count)
+{
+	uint8_t i;
+
+	for (i = 0; i < count; i++)
+		usbdk_helper.ReleaseConfigurationDescriptor(p->config_descriptors[i]);
+
+	free(p->config_descriptors);
+	p->config_descriptors = NULL;
+}
+
+static int usbdk_cache_config_descriptors(struct libusb_context *ctx,
+	struct usbdk_device_priv *p, PUSB_DK_DEVICE_INFO info)
+{
+	uint8_t i;
+	USB_DK_CONFIG_DESCRIPTOR_REQUEST Request;
+	Request.ID = info->ID;
+
+	p->config_descriptors = calloc(info->DeviceDescriptor.bNumConfigurations, sizeof(PUSB_CONFIGURATION_DESCRIPTOR));
+	if (p->config_descriptors == NULL) {
+		usbi_err(ctx, "failed to allocate configuration descriptors holder");
+		return LIBUSB_ERROR_NO_MEM;
+	}
+
+	for (i = 0; i < info->DeviceDescriptor.bNumConfigurations; i++) {
+		ULONG Length;
+
+		Request.Index = i;
+		if (!usbdk_helper.GetConfigurationDescriptor(&Request, &p->config_descriptors[i], &Length)) {
+			usbi_err(ctx, "failed to retrieve configuration descriptors");
+			usbdk_release_config_descriptors(p, i);
+			return LIBUSB_ERROR_OTHER;
+		}
+	}
+
+	return LIBUSB_SUCCESS;
+}
+
+static inline int usbdk_device_priv_init(struct libusb_context *ctx, struct libusb_device *dev, PUSB_DK_DEVICE_INFO info)
+{
+	struct usbdk_device_priv *p = _usbdk_device_priv(dev);
+
+	p->info = *info;
+	p->active_configuration = 0;
+
+	return usbdk_cache_config_descriptors(ctx, p, info);
+}
+
+static void usbdk_device_init(libusb_device *dev, PUSB_DK_DEVICE_INFO info)
+{
+	dev->bus_number = (uint8_t)info->FilterID;
+	dev->port_number = (uint8_t)info->Port;
+	dev->parent_dev = NULL;
+
+	//Addresses in libusb are 1-based
+	dev->device_address = (uint8_t)(info->Port + 1);
+
+	dev->num_configurations = info->DeviceDescriptor.bNumConfigurations;
+	dev->device_descriptor = info->DeviceDescriptor;
+
+	switch (info->Speed) {
+	case LowSpeed:
+		dev->speed = LIBUSB_SPEED_LOW;
+		break;
+	case FullSpeed:
+		dev->speed = LIBUSB_SPEED_FULL;
+		break;
+	case HighSpeed:
+		dev->speed = LIBUSB_SPEED_HIGH;
+		break;
+	case SuperSpeed:
+		dev->speed = LIBUSB_SPEED_SUPER;
+		break;
+	case NoSpeed:
+	default:
+		dev->speed = LIBUSB_SPEED_UNKNOWN;
+		break;
+	}
+}
+
+static int usbdk_get_device_list(struct libusb_context *ctx, struct discovered_devs **_discdevs)
+{
+	int r = LIBUSB_SUCCESS;
+	ULONG i;
+	struct discovered_devs *discdevs = NULL;
+	ULONG dev_number;
+	PUSB_DK_DEVICE_INFO devices;
+
+	if(!usbdk_helper.GetDevicesList(&devices, &dev_number))
+		return LIBUSB_ERROR_OTHER;
+
+	for (i = 0; i < dev_number; i++) {
+		unsigned long session_id;
+		struct libusb_device *dev = NULL;
+
+		if (usbdk_get_session_id_for_device(ctx, &devices[i].ID, &session_id))
+			continue;
+
+		dev = usbi_get_device_by_session_id(ctx, session_id);
+		if (dev == NULL) {
+			dev = usbi_alloc_device(ctx, session_id);
+			if (dev == NULL) {
+				usbi_err(ctx, "failed to allocate a new device structure");
+				continue;
+			}
+
+			usbdk_device_init(dev, &devices[i]);
+			if (usbdk_device_priv_init(ctx, dev, &devices[i]) != LIBUSB_SUCCESS) {
+				libusb_unref_device(dev);
+				continue;
+			}
+		}
+
+		discdevs = discovered_devs_append(*_discdevs, dev);
+		libusb_unref_device(dev);
+		if (!discdevs) {
+			usbi_err(ctx, "cannot append new device to list");
+			r = LIBUSB_ERROR_NO_MEM;
+			goto func_exit;
+		}
+
+		*_discdevs = discdevs;
+	}
+
+func_exit:
+	usbdk_helper.ReleaseDevicesList(devices);
+	return r;
+}
+
+static void usbdk_exit(void)
+{
+	if (--concurrent_usage < 0) {
+		windows_common_exit();
+		exit_polling();
+		unload_usbdk_helper_dll();
+	}
+}
+
+static int usbdk_get_device_descriptor(struct libusb_device *dev, unsigned char *buffer, int *host_endian)
+{
+	struct usbdk_device_priv *priv = _usbdk_device_priv(dev);
+
+	memcpy(buffer, &priv->info.DeviceDescriptor, DEVICE_DESC_LENGTH);
+	*host_endian = 0;
+
+	return LIBUSB_SUCCESS;
+}
+
+static int usbdk_get_config_descriptor(struct libusb_device *dev, uint8_t config_index, unsigned char *buffer, size_t len, int *host_endian)
+{
+	struct usbdk_device_priv *priv = _usbdk_device_priv(dev);
+	PUSB_CONFIGURATION_DESCRIPTOR config_header;
+	size_t size;
+
+	if (config_index >= dev->num_configurations)
+		return LIBUSB_ERROR_INVALID_PARAM;
+
+	config_header = (PUSB_CONFIGURATION_DESCRIPTOR)priv->config_descriptors[config_index];
+
+	size = min(config_header->wTotalLength, len);
+	memcpy(buffer, config_header, size);
+	*host_endian = 0;
+
+	return (int)size;
+}
+
+static inline int usbdk_get_active_config_descriptor(struct libusb_device *dev, unsigned char *buffer, size_t len, int *host_endian)
+{
+	return usbdk_get_config_descriptor(dev, _usbdk_device_priv(dev)->active_configuration,
+			buffer, len, host_endian);
+}
+
+static int usbdk_open(struct libusb_device_handle *dev_handle)
+{
+	struct usbdk_device_priv *priv = _usbdk_device_priv(dev_handle->dev);
+
+	priv->redirector_handle = usbdk_helper.StartRedirect(&priv->info.ID);
+	if (priv->redirector_handle == INVALID_HANDLE_VALUE) {
+		usbi_err(DEVICE_CTX(dev_handle->dev), "Redirector startup failed");
+		return LIBUSB_ERROR_OTHER;
+	}
+
+	return LIBUSB_SUCCESS;
+}
+
+static void usbdk_close(struct libusb_device_handle *dev_handle)
+{
+	struct usbdk_device_priv *priv = _usbdk_device_priv(dev_handle->dev);
+
+	if (!usbdk_helper.StopRedirect(priv->redirector_handle)) {
+		struct libusb_context *ctx = DEVICE_CTX(dev_handle->dev);
+		usbi_err(ctx, "Redirector shutdown failed");
+	}
+}
+
+static int usbdk_get_configuration(struct libusb_device_handle *dev_handle, int *config)
+{
+	*config = _usbdk_device_priv(dev_handle->dev)->active_configuration;
+
+	return LIBUSB_SUCCESS;
+}
+
+static int usbdk_set_configuration(struct libusb_device_handle *dev_handle, int config)
+{
+	UNUSED(dev_handle);
+	UNUSED(config);
+	return LIBUSB_SUCCESS;
+}
+
+static int usbdk_claim_interface(struct libusb_device_handle *dev_handle, int iface)
+{
+	UNUSED(dev_handle);
+	UNUSED(iface);
+	return LIBUSB_SUCCESS;
+}
+
+static int usbdk_set_interface_altsetting(struct libusb_device_handle *dev_handle, int iface, int altsetting)
+{
+	struct libusb_context *ctx = DEVICE_CTX(dev_handle->dev);
+	struct usbdk_device_priv *priv = _usbdk_device_priv(dev_handle->dev);
+
+	if (!usbdk_helper.SetAltsetting(priv->redirector_handle, iface, altsetting)) {
+		usbi_err(ctx, "SetAltsetting failed: %s", windows_error_str(0));
+		return LIBUSB_ERROR_NO_DEVICE;
+	}
+
+	return LIBUSB_SUCCESS;
+}
+
+static int usbdk_release_interface(struct libusb_device_handle *dev_handle, int iface)
+{
+	UNUSED(dev_handle);
+	UNUSED(iface);
+	return LIBUSB_SUCCESS;
+}
+
+static int usbdk_clear_halt(struct libusb_device_handle *dev_handle, unsigned char endpoint)
+{
+	struct libusb_context *ctx = DEVICE_CTX(dev_handle->dev);
+	struct usbdk_device_priv *priv = _usbdk_device_priv(dev_handle->dev);
+
+	if (!usbdk_helper.ResetPipe(priv->redirector_handle, endpoint)) {
+		usbi_err(ctx, "ResetPipe failed: %s", windows_error_str(0));
+		return LIBUSB_ERROR_NO_DEVICE;
+	}
+
+	return LIBUSB_SUCCESS;
+}
+
+static int usbdk_reset_device(struct libusb_device_handle *dev_handle)
+{
+	struct libusb_context *ctx = DEVICE_CTX(dev_handle->dev);
+	struct usbdk_device_priv *priv = _usbdk_device_priv(dev_handle->dev);
+
+	if (!usbdk_helper.ResetDevice(priv->redirector_handle)) {
+		usbi_err(ctx, "ResetDevice failed: %s", windows_error_str(0));
+		return LIBUSB_ERROR_NO_DEVICE;
+	}
+
+	return LIBUSB_SUCCESS;
+}
+
+static int usbdk_kernel_driver_active(struct libusb_device_handle *dev_handle, int iface)
+{
+	UNUSED(dev_handle);
+	UNUSED(iface);
+	return LIBUSB_ERROR_NOT_SUPPORTED;
+}
+
+static int usbdk_attach_kernel_driver(struct libusb_device_handle *dev_handle, int iface)
+{
+	UNUSED(dev_handle);
+	UNUSED(iface);
+	return LIBUSB_ERROR_NOT_SUPPORTED;
+}
+
+static int usbdk_detach_kernel_driver(struct libusb_device_handle *dev_handle, int iface)
+{
+	UNUSED(dev_handle);
+	UNUSED(iface);
+	return LIBUSB_ERROR_NOT_SUPPORTED;
+}
+
+static void usbdk_destroy_device(struct libusb_device *dev)
+{
+	struct usbdk_device_priv* p = _usbdk_device_priv(dev);
+
+	if (p->config_descriptors != NULL)
+		usbdk_release_config_descriptors(p, p->info.DeviceDescriptor.bNumConfigurations);
+}
+
+void windows_clear_transfer_priv(struct usbi_transfer *itransfer)
+{
+	struct usbdk_transfer_priv *transfer_priv = _usbdk_transfer_priv(itransfer);
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+
+	usbi_free_fd(&transfer_priv->pollable_fd);
+
+	if (transfer->type == LIBUSB_TRANSFER_TYPE_ISOCHRONOUS) {
+		safe_free(transfer_priv->IsochronousPacketsArray);
+		safe_free(transfer_priv->IsochronousResultsArray);
+	}
+}
+
+static int usbdk_do_control_transfer(struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	struct usbdk_device_priv *priv = _usbdk_device_priv(transfer->dev_handle->dev);
+	struct usbdk_transfer_priv *transfer_priv = _usbdk_transfer_priv(itransfer);
+	struct libusb_context *ctx = DEVICE_CTX(transfer->dev_handle->dev);
+	struct winfd wfd;
+	ULONG Length;
+	TransferResult transResult;
+	HANDLE sysHandle;
+
+	sysHandle = usbdk_helper.GetRedirectorSystemHandle(priv->redirector_handle);
+
+	wfd = usbi_create_fd(sysHandle, RW_READ, NULL, NULL);
+	// Always use the handle returned from usbi_create_fd (wfd.handle)
+	if (wfd.fd < 0)
+		return LIBUSB_ERROR_NO_MEM;
+
+	transfer_priv->request.Buffer = (PVOID64)(uintptr_t)transfer->buffer;
+	transfer_priv->request.BufferLength = transfer->length;
+	transfer_priv->request.TransferType = ControlTransferType;
+	transfer_priv->pollable_fd = INVALID_WINFD;
+	Length = (ULONG)transfer->length;
+
+	if (IS_XFERIN(transfer))
+		transResult = usbdk_helper.ReadPipe(priv->redirector_handle, &transfer_priv->request, wfd.overlapped);
+	else
+		transResult = usbdk_helper.WritePipe(priv->redirector_handle, &transfer_priv->request, wfd.overlapped);
+
+	switch (transResult) {
+	case TransferSuccess:
+		wfd.overlapped->Internal = STATUS_COMPLETED_SYNCHRONOUSLY;
+		wfd.overlapped->InternalHigh = (DWORD)Length;
+		break;
+	case TransferSuccessAsync:
+		break;
+	case TransferFailure:
+		usbi_err(ctx, "ControlTransfer failed: %s", windows_error_str(0));
+		usbi_free_fd(&wfd);
+		return LIBUSB_ERROR_IO;
+	}
+
+	// Use priv_transfer to store data needed for async polling
+	transfer_priv->pollable_fd = wfd;
+	usbi_add_pollfd(ctx, transfer_priv->pollable_fd.fd, POLLIN);
+
+	return LIBUSB_SUCCESS;
+}
+
+static int usbdk_do_bulk_transfer(struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	struct usbdk_device_priv *priv = _usbdk_device_priv(transfer->dev_handle->dev);
+	struct usbdk_transfer_priv *transfer_priv = _usbdk_transfer_priv(itransfer);
+	struct libusb_context *ctx = DEVICE_CTX(transfer->dev_handle->dev);
+	struct winfd wfd;
+	TransferResult transferRes;
+	HANDLE sysHandle;
+
+	transfer_priv->request.Buffer = (PVOID64)(uintptr_t)transfer->buffer;
+	transfer_priv->request.BufferLength = transfer->length;
+	transfer_priv->request.EndpointAddress = transfer->endpoint;
+
+	switch (transfer->type) {
+	case LIBUSB_TRANSFER_TYPE_BULK:
+		transfer_priv->request.TransferType = BulkTransferType;
+		break;
+	case LIBUSB_TRANSFER_TYPE_INTERRUPT:
+		transfer_priv->request.TransferType = IntertuptTransferType;
+		break;
+	default:
+		usbi_err(ctx, "Wrong transfer type (%d) in usbdk_do_bulk_transfer. %s", transfer->type, windows_error_str(0));
+		return LIBUSB_ERROR_INVALID_PARAM;
+	}
+
+	transfer_priv->pollable_fd = INVALID_WINFD;
+
+	sysHandle = usbdk_helper.GetRedirectorSystemHandle(priv->redirector_handle);
+
+	wfd = usbi_create_fd(sysHandle, IS_XFERIN(transfer) ? RW_READ : RW_WRITE, NULL, NULL);
+	// Always use the handle returned from usbi_create_fd (wfd.handle)
+	if (wfd.fd < 0)
+		return LIBUSB_ERROR_NO_MEM;
+
+	if (IS_XFERIN(transfer))
+		transferRes = usbdk_helper.ReadPipe(priv->redirector_handle, &transfer_priv->request, wfd.overlapped);
+	else
+		transferRes = usbdk_helper.WritePipe(priv->redirector_handle, &transfer_priv->request, wfd.overlapped);
+
+	switch (transferRes) {
+	case TransferSuccess:
+		wfd.overlapped->Internal = STATUS_COMPLETED_SYNCHRONOUSLY;
+		break;
+	case TransferSuccessAsync:
+		break;
+	case TransferFailure:
+		usbi_err(ctx, "ReadPipe/WritePipe failed: %s", windows_error_str(0));
+		usbi_free_fd(&wfd);
+		return LIBUSB_ERROR_IO;
+	}
+
+	transfer_priv->pollable_fd = wfd;
+	usbi_add_pollfd(ctx, transfer_priv->pollable_fd.fd, IS_XFERIN(transfer) ? POLLIN : POLLOUT);
+
+	return LIBUSB_SUCCESS;
+}
+
+static int usbdk_do_iso_transfer(struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	struct usbdk_device_priv *priv = _usbdk_device_priv(transfer->dev_handle->dev);
+	struct usbdk_transfer_priv *transfer_priv = _usbdk_transfer_priv(itransfer);
+	struct libusb_context *ctx = DEVICE_CTX(transfer->dev_handle->dev);
+	struct winfd wfd;
+	TransferResult transferRes;
+	int i;
+	HANDLE sysHandle;
+
+	transfer_priv->request.Buffer = (PVOID64)(uintptr_t)transfer->buffer;
+	transfer_priv->request.BufferLength = transfer->length;
+	transfer_priv->request.EndpointAddress = transfer->endpoint;
+	transfer_priv->request.TransferType = IsochronousTransferType;
+	transfer_priv->request.IsochronousPacketsArraySize = transfer->num_iso_packets;
+	transfer_priv->IsochronousPacketsArray = malloc(transfer->num_iso_packets * sizeof(ULONG64));
+	transfer_priv->request.IsochronousPacketsArray = (PVOID64)(uintptr_t)transfer_priv->IsochronousPacketsArray;
+	if (!transfer_priv->IsochronousPacketsArray) {
+		usbi_err(ctx, "Allocation of IsochronousPacketsArray is failed, %s", windows_error_str(0));
+		return LIBUSB_ERROR_IO;
+	}
+
+	transfer_priv->IsochronousResultsArray = malloc(transfer->num_iso_packets * sizeof(USB_DK_ISO_TRANSFER_RESULT));
+	transfer_priv->request.Result.IsochronousResultsArray = (PVOID64)(uintptr_t)transfer_priv->IsochronousResultsArray;
+	if (!transfer_priv->IsochronousResultsArray) {
+		usbi_err(ctx, "Allocation of isochronousResultsArray is failed, %s", windows_error_str(0));
+		free(transfer_priv->IsochronousPacketsArray);
+		return LIBUSB_ERROR_IO;
+	}
+
+	for (i = 0; i < transfer->num_iso_packets; i++)
+		transfer_priv->IsochronousPacketsArray[i] = transfer->iso_packet_desc[i].length;
+
+	transfer_priv->pollable_fd = INVALID_WINFD;
+
+	sysHandle = usbdk_helper.GetRedirectorSystemHandle(priv->redirector_handle);
+
+	wfd = usbi_create_fd(sysHandle, IS_XFERIN(transfer) ? RW_READ : RW_WRITE, NULL, NULL);
+	// Always use the handle returned from usbi_create_fd (wfd.handle)
+	if (wfd.fd < 0) {
+		free(transfer_priv->IsochronousPacketsArray);
+		free(transfer_priv->IsochronousResultsArray);
+		return LIBUSB_ERROR_NO_MEM;
+	}
+
+	if (IS_XFERIN(transfer))
+		transferRes = usbdk_helper.ReadPipe(priv->redirector_handle, &transfer_priv->request, wfd.overlapped);
+	else
+		transferRes = usbdk_helper.WritePipe(priv->redirector_handle, &transfer_priv->request, wfd.overlapped);
+
+	switch (transferRes) {
+	case TransferSuccess:
+		wfd.overlapped->Internal = STATUS_COMPLETED_SYNCHRONOUSLY;
+		break;
+	case TransferSuccessAsync:
+		break;
+	case TransferFailure:
+		usbi_err(ctx, "ReadPipe/WritePipe failed: %s", windows_error_str(0));
+		usbi_free_fd(&wfd);
+		free(transfer_priv->IsochronousPacketsArray);
+		free(transfer_priv->IsochronousResultsArray);
+		return LIBUSB_ERROR_IO;
+	}
+
+	transfer_priv->pollable_fd = wfd;
+	usbi_add_pollfd(ctx, transfer_priv->pollable_fd.fd, IS_XFERIN(transfer) ? POLLIN : POLLOUT);
+
+	return LIBUSB_SUCCESS;
+}
+
+static int usbdk_submit_transfer(struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+
+	switch (transfer->type) {
+	case LIBUSB_TRANSFER_TYPE_CONTROL:
+		return usbdk_do_control_transfer(itransfer);
+	case LIBUSB_TRANSFER_TYPE_BULK:
+	case LIBUSB_TRANSFER_TYPE_INTERRUPT:
+		if (IS_XFEROUT(transfer) && (transfer->flags & LIBUSB_TRANSFER_ADD_ZERO_PACKET))
+			return LIBUSB_ERROR_NOT_SUPPORTED; //TODO: Check whether we can support this in UsbDk
+		else
+			return usbdk_do_bulk_transfer(itransfer);
+	case LIBUSB_TRANSFER_TYPE_ISOCHRONOUS:
+		return usbdk_do_iso_transfer(itransfer);
+	default:
+		usbi_err(TRANSFER_CTX(transfer), "unknown endpoint type %d", transfer->type);
+		return LIBUSB_ERROR_INVALID_PARAM;
+	}
+}
+
+static int usbdk_abort_transfers(struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	struct libusb_context *ctx = DEVICE_CTX(transfer->dev_handle->dev);
+	struct usbdk_device_priv *priv = _usbdk_device_priv(transfer->dev_handle->dev);
+
+	if (!usbdk_helper.AbortPipe(priv->redirector_handle, transfer->endpoint)) {
+		usbi_err(ctx, "AbortPipe failed: %s", windows_error_str(0));
+		return LIBUSB_ERROR_NO_DEVICE;
+	}
+
+	return LIBUSB_SUCCESS;
+}
+
+static int usbdk_cancel_transfer(struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+
+	switch (transfer->type) {
+	case LIBUSB_TRANSFER_TYPE_CONTROL:
+		// Control transfers cancelled by IoCancelXXX() API
+		// No special treatment needed
+		return LIBUSB_SUCCESS;
+	case LIBUSB_TRANSFER_TYPE_BULK:
+	case LIBUSB_TRANSFER_TYPE_INTERRUPT:
+	case LIBUSB_TRANSFER_TYPE_ISOCHRONOUS:
+		return usbdk_abort_transfers(itransfer);
+	default:
+		usbi_err(ITRANSFER_CTX(itransfer), "unknown endpoint type %d", transfer->type);
+		return LIBUSB_ERROR_INVALID_PARAM;
+	}
+}
+
+int windows_copy_transfer_data(struct usbi_transfer *itransfer, uint32_t io_size)
+{
+	itransfer->transferred += io_size;
+	return LIBUSB_TRANSFER_COMPLETED;
+}
+
+struct winfd *windows_get_fd(struct usbi_transfer *transfer)
+{
+	struct usbdk_transfer_priv *transfer_priv = _usbdk_transfer_priv(transfer);
+	return &transfer_priv->pollable_fd;
+}
+
+static DWORD usbdk_translate_usbd_status(USBD_STATUS UsbdStatus)
+{
+	if (USBD_SUCCESS(UsbdStatus))
+		return NO_ERROR;
+
+	switch (UsbdStatus) {
+	case USBD_STATUS_STALL_PID:
+	case USBD_STATUS_ENDPOINT_HALTED:
+	case USBD_STATUS_BAD_START_FRAME:
+		return ERROR_GEN_FAILURE;
+	case USBD_STATUS_TIMEOUT:
+		return ERROR_SEM_TIMEOUT;
+	case USBD_STATUS_CANCELED:
+		return ERROR_OPERATION_ABORTED;
+	default:
+		return ERROR_FUNCTION_FAILED;
+	}
+}
+
+void windows_get_overlapped_result(struct usbi_transfer *transfer, struct winfd *pollable_fd, DWORD *io_result, DWORD *io_size)
+{
+	if (HasOverlappedIoCompletedSync(pollable_fd->overlapped) // Handle async requests that completed synchronously first
+			|| GetOverlappedResult(pollable_fd->handle, pollable_fd->overlapped, io_size, false)) { // Regular async overlapped
+		struct libusb_transfer *ltransfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(transfer);
+		struct usbdk_transfer_priv *transfer_priv = _usbdk_transfer_priv(transfer);
+
+		if (ltransfer->type == LIBUSB_TRANSFER_TYPE_ISOCHRONOUS) {
+			int i;
+			for (i = 0; i < transfer_priv->request.IsochronousPacketsArraySize; i++) {
+				struct libusb_iso_packet_descriptor *lib_desc = &ltransfer->iso_packet_desc[i];
+
+				switch (transfer_priv->IsochronousResultsArray[i].TransferResult) {
+				case STATUS_SUCCESS:
+				case STATUS_CANCELLED:
+				case STATUS_REQUEST_CANCELED:
+					lib_desc->status = LIBUSB_TRANSFER_COMPLETED; // == ERROR_SUCCESS
+					break;
+				default:
+					lib_desc->status = LIBUSB_TRANSFER_ERROR; // ERROR_UNKNOWN_EXCEPTION;
+					break;
+				}
+
+				lib_desc->actual_length = (unsigned int)transfer_priv->IsochronousResultsArray[i].ActualLength;
+			}
+		}
+
+		*io_size = (DWORD) transfer_priv->request.Result.GenResult.BytesTransferred;
+		*io_result = usbdk_translate_usbd_status((USBD_STATUS) transfer_priv->request.Result.GenResult.UsbdStatus);
+	}
+	else {
+		*io_result = GetLastError();
+	}
+}
+
+static int usbdk_clock_gettime(int clk_id, struct timespec *tp)
+{
+	return windows_clock_gettime(clk_id, tp);
+}
+
+const struct usbi_os_backend usbdk_backend = {
+	"Windows",
+	USBI_CAP_HAS_HID_ACCESS,
+	usbdk_init,
+	usbdk_exit,
+
+	usbdk_get_device_list,
+	NULL,
+	usbdk_open,
+	usbdk_close,
+
+	usbdk_get_device_descriptor,
+	usbdk_get_active_config_descriptor,
+	usbdk_get_config_descriptor,
+	NULL,
+
+	usbdk_get_configuration,
+	usbdk_set_configuration,
+	usbdk_claim_interface,
+	usbdk_release_interface,
+
+	usbdk_set_interface_altsetting,
+	usbdk_clear_halt,
+	usbdk_reset_device,
+
+	NULL,
+	NULL,
+
+	NULL,	// dev_mem_alloc()
+	NULL,	// dev_mem_free()
+
+	usbdk_kernel_driver_active,
+	usbdk_detach_kernel_driver,
+	usbdk_attach_kernel_driver,
+
+	usbdk_destroy_device,
+
+	usbdk_submit_transfer,
+	usbdk_cancel_transfer,
+	windows_clear_transfer_priv,
+
+	windows_handle_events,
+	NULL,
+
+	usbdk_clock_gettime,
+#if defined(USBI_TIMERFD_AVAILABLE)
+	NULL,
+#endif
+	sizeof(struct usbdk_device_priv),
+	0,
+	sizeof(struct usbdk_transfer_priv),
+};
+
+#endif /* USE_USBDK */
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/windows_usbdk.h b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/windows_usbdk.h
new file mode 100644
index 000000000..04a9787f2
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/windows_usbdk.h
@@ -0,0 +1,146 @@
+/*
+* windows UsbDk backend for libusb 1.0
+* Copyright © 2014 Red Hat, Inc.
+
+* Authors:
+* Dmitry Fleytman <dmitry@daynix.com>
+* Pavel Gurvich <pavel@daynix.com>
+*
+* This library is free software; you can redistribute it and/or
+* modify it under the terms of the GNU Lesser General Public
+* License as published by the Free Software Foundation; either
+* version 2.1 of the License, or (at your option) any later version.
+*
+* This library is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+* Lesser General Public License for more details.
+*
+* You should have received a copy of the GNU Lesser General Public
+* License along with this library; if not, write to the Free Software
+* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+*/
+
+#pragma once
+
+typedef struct tag_USB_DK_DEVICE_ID {
+	WCHAR DeviceID[MAX_DEVICE_ID_LEN];
+	WCHAR InstanceID[MAX_DEVICE_ID_LEN];
+} USB_DK_DEVICE_ID, *PUSB_DK_DEVICE_ID;
+
+static inline void UsbDkFillIDStruct(USB_DK_DEVICE_ID *ID, PCWCHAR DeviceID, PCWCHAR InstanceID)
+{
+	wcsncpy_s(ID->DeviceID, DeviceID, MAX_DEVICE_ID_LEN);
+	wcsncpy_s(ID->InstanceID, InstanceID, MAX_DEVICE_ID_LEN);
+}
+
+typedef struct tag_USB_DK_DEVICE_INFO {
+	USB_DK_DEVICE_ID ID;
+	ULONG64 FilterID;
+	ULONG64 Port;
+	ULONG64 Speed;
+	USB_DEVICE_DESCRIPTOR DeviceDescriptor;
+} USB_DK_DEVICE_INFO, *PUSB_DK_DEVICE_INFO;
+
+typedef struct tag_USB_DK_CONFIG_DESCRIPTOR_REQUEST {
+	USB_DK_DEVICE_ID ID;
+	ULONG64 Index;
+} USB_DK_CONFIG_DESCRIPTOR_REQUEST, *PUSB_DK_CONFIG_DESCRIPTOR_REQUEST;
+
+typedef struct tag_USB_DK_ISO_TRANSFER_RESULT {
+	ULONG64 ActualLength;
+	ULONG64 TransferResult;
+} USB_DK_ISO_TRANSFER_RESULT, *PUSB_DK_ISO_TRANSFER_RESULT;
+
+typedef struct tag_USB_DK_GEN_TRANSFER_RESULT {
+	ULONG64 BytesTransferred;
+	ULONG64 UsbdStatus; // USBD_STATUS code
+} USB_DK_GEN_TRANSFER_RESULT, *PUSB_DK_GEN_TRANSFER_RESULT;
+
+typedef struct tag_USB_DK_TRANSFER_RESULT {
+	USB_DK_GEN_TRANSFER_RESULT GenResult;
+	PVOID64 IsochronousResultsArray; // array of USB_DK_ISO_TRANSFER_RESULT
+} USB_DK_TRANSFER_RESULT, *PUSB_DK_TRANSFER_RESULT;
+
+typedef struct tag_USB_DK_TRANSFER_REQUEST {
+	ULONG64 EndpointAddress;
+	PVOID64 Buffer;
+	ULONG64 BufferLength;
+	ULONG64 TransferType;
+	ULONG64 IsochronousPacketsArraySize;
+	PVOID64 IsochronousPacketsArray;
+
+	USB_DK_TRANSFER_RESULT Result;
+} USB_DK_TRANSFER_REQUEST, *PUSB_DK_TRANSFER_REQUEST;
+
+typedef enum {
+	TransferFailure = 0,
+	TransferSuccess,
+	TransferSuccessAsync
+} TransferResult;
+
+typedef enum {
+	NoSpeed = 0,
+	LowSpeed,
+	FullSpeed,
+	HighSpeed,
+	SuperSpeed
+} USB_DK_DEVICE_SPEED;
+
+typedef enum {
+	ControlTransferType,
+	BulkTransferType,
+	IntertuptTransferType,
+	IsochronousTransferType
+} USB_DK_TRANSFER_TYPE;
+
+typedef BOOL (__cdecl *USBDK_GET_DEVICES_LIST)(
+	PUSB_DK_DEVICE_INFO *DeviceInfo,
+	PULONG DeviceNumber
+);
+typedef void (__cdecl *USBDK_RELEASE_DEVICES_LIST)(
+	PUSB_DK_DEVICE_INFO DeviceInfo
+);
+typedef HANDLE (__cdecl *USBDK_START_REDIRECT)(
+	PUSB_DK_DEVICE_ID DeviceId
+);
+typedef BOOL (__cdecl *USBDK_STOP_REDIRECT)(
+	HANDLE DeviceHandle
+);
+typedef BOOL (__cdecl *USBDK_GET_CONFIGURATION_DESCRIPTOR)(
+	PUSB_DK_CONFIG_DESCRIPTOR_REQUEST Request,
+	PUSB_CONFIGURATION_DESCRIPTOR *Descriptor,
+	PULONG Length
+);
+typedef void (__cdecl *USBDK_RELEASE_CONFIGURATION_DESCRIPTOR)(
+	PUSB_CONFIGURATION_DESCRIPTOR Descriptor
+);
+typedef TransferResult (__cdecl *USBDK_WRITE_PIPE)(
+	HANDLE DeviceHandle,
+	PUSB_DK_TRANSFER_REQUEST Request,
+	LPOVERLAPPED lpOverlapped
+);
+typedef TransferResult (__cdecl *USBDK_READ_PIPE)(
+	HANDLE DeviceHandle,
+	PUSB_DK_TRANSFER_REQUEST Request,
+	LPOVERLAPPED lpOverlapped
+);
+typedef BOOL (__cdecl *USBDK_ABORT_PIPE)(
+	HANDLE DeviceHandle,
+	ULONG64 PipeAddress
+);
+typedef BOOL (__cdecl *USBDK_RESET_PIPE)(
+	HANDLE DeviceHandle,
+	ULONG64 PipeAddress
+);
+typedef BOOL (__cdecl *USBDK_SET_ALTSETTING)(
+	HANDLE DeviceHandle,
+	ULONG64 InterfaceIdx,
+	ULONG64 AltSettingIdx
+);
+typedef BOOL (__cdecl *USBDK_RESET_DEVICE)(
+	HANDLE DeviceHandle
+);
+typedef HANDLE (__cdecl *USBDK_GET_REDIRECTOR_SYSTEM_HANDLE)(
+	HANDLE DeviceHandle
+);
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/windows_winusb.c b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/windows_winusb.c
new file mode 100644
index 000000000..0dce0ea6c
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/windows_winusb.c
@@ -0,0 +1,4290 @@
+/*
+ * windows backend for libusb 1.0
+ * Copyright © 2009-2012 Pete Batard <pete@akeo.ie>
+ * With contributions from Michael Plante, Orin Eman et al.
+ * Parts of this code adapted from libusb-win32-v1 by Stephan Meyer
+ * HID Reports IOCTLs inspired from HIDAPI by Alan Ott, Signal 11 Software
+ * Hash table functions adapted from glibc, by Ulrich Drepper et al.
+ * Major code testing contribution by Xiaofan Chen
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <config.h>
+
+#if !defined(USE_USBDK)
+
+#include <windows.h>
+#include <setupapi.h>
+#include <ctype.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <process.h>
+#include <stdio.h>
+#include <inttypes.h>
+#include <objbase.h>
+#include <winioctl.h>
+
+#include "libusbi.h"
+#include "poll_windows.h"
+#include "windows_winusb.h"
+
+#define HANDLE_VALID(h) (((h) != 0) && ((h) != INVALID_HANDLE_VALUE))
+
+// The 2 macros below are used in conjunction with safe loops.
+#define LOOP_CHECK(fcall)			\
+	{					\
+		r = fcall;			\
+		if (r != LIBUSB_SUCCESS)	\
+			continue;		\
+	}
+#define LOOP_BREAK(err)				\
+	{					\
+		r = err;			\
+		continue;			\
+	}
+
+// WinUSB-like API prototypes
+static int winusbx_init(int sub_api, struct libusb_context *ctx);
+static int winusbx_exit(int sub_api);
+static int winusbx_open(int sub_api, struct libusb_device_handle *dev_handle);
+static void winusbx_close(int sub_api, struct libusb_device_handle *dev_handle);
+static int winusbx_configure_endpoints(int sub_api, struct libusb_device_handle *dev_handle, int iface);
+static int winusbx_claim_interface(int sub_api, struct libusb_device_handle *dev_handle, int iface);
+static int winusbx_release_interface(int sub_api, struct libusb_device_handle *dev_handle, int iface);
+static int winusbx_submit_control_transfer(int sub_api, struct usbi_transfer *itransfer);
+static int winusbx_set_interface_altsetting(int sub_api, struct libusb_device_handle *dev_handle, int iface, int altsetting);
+static int winusbx_submit_bulk_transfer(int sub_api, struct usbi_transfer *itransfer);
+static int winusbx_clear_halt(int sub_api, struct libusb_device_handle *dev_handle, unsigned char endpoint);
+static int winusbx_abort_transfers(int sub_api, struct usbi_transfer *itransfer);
+static int winusbx_abort_control(int sub_api, struct usbi_transfer *itransfer);
+static int winusbx_reset_device(int sub_api, struct libusb_device_handle *dev_handle);
+static int winusbx_copy_transfer_data(int sub_api, struct usbi_transfer *itransfer, uint32_t io_size);
+// HID API prototypes
+static int hid_init(int sub_api, struct libusb_context *ctx);
+static int hid_exit(int sub_api);
+static int hid_open(int sub_api, struct libusb_device_handle *dev_handle);
+static void hid_close(int sub_api, struct libusb_device_handle *dev_handle);
+static int hid_claim_interface(int sub_api, struct libusb_device_handle *dev_handle, int iface);
+static int hid_release_interface(int sub_api, struct libusb_device_handle *dev_handle, int iface);
+static int hid_set_interface_altsetting(int sub_api, struct libusb_device_handle *dev_handle, int iface, int altsetting);
+static int hid_submit_control_transfer(int sub_api, struct usbi_transfer *itransfer);
+static int hid_submit_bulk_transfer(int sub_api, struct usbi_transfer *itransfer);
+static int hid_clear_halt(int sub_api, struct libusb_device_handle *dev_handle, unsigned char endpoint);
+static int hid_abort_transfers(int sub_api, struct usbi_transfer *itransfer);
+static int hid_reset_device(int sub_api, struct libusb_device_handle *dev_handle);
+static int hid_copy_transfer_data(int sub_api, struct usbi_transfer *itransfer, uint32_t io_size);
+// Composite API prototypes
+static int composite_init(int sub_api, struct libusb_context *ctx);
+static int composite_exit(int sub_api);
+static int composite_open(int sub_api, struct libusb_device_handle *dev_handle);
+static void composite_close(int sub_api, struct libusb_device_handle *dev_handle);
+static int composite_claim_interface(int sub_api, struct libusb_device_handle *dev_handle, int iface);
+static int composite_set_interface_altsetting(int sub_api, struct libusb_device_handle *dev_handle, int iface, int altsetting);
+static int composite_release_interface(int sub_api, struct libusb_device_handle *dev_handle, int iface);
+static int composite_submit_control_transfer(int sub_api, struct usbi_transfer *itransfer);
+static int composite_submit_bulk_transfer(int sub_api, struct usbi_transfer *itransfer);
+static int composite_submit_iso_transfer(int sub_api, struct usbi_transfer *itransfer);
+static int composite_clear_halt(int sub_api, struct libusb_device_handle *dev_handle, unsigned char endpoint);
+static int composite_abort_transfers(int sub_api, struct usbi_transfer *itransfer);
+static int composite_abort_control(int sub_api, struct usbi_transfer *itransfer);
+static int composite_reset_device(int sub_api, struct libusb_device_handle *dev_handle);
+static int composite_copy_transfer_data(int sub_api, struct usbi_transfer *itransfer, uint32_t io_size);
+
+
+// Global variables
+int windows_version = WINDOWS_UNDEFINED;
+static char windows_version_str[128] = "Undefined";
+// Concurrency
+static int concurrent_usage = -1;
+static usbi_mutex_t autoclaim_lock;
+// API globals
+#define CHECK_WINUSBX_AVAILABLE(sub_api)		\
+	do {						\
+		if (sub_api == SUB_API_NOTSET)		\
+			sub_api = priv->sub_api;	\
+		if (!WinUSBX[sub_api].initialized) 	\
+			return LIBUSB_ERROR_ACCESS;	\
+	} while(0)
+
+static HMODULE WinUSBX_handle = NULL;
+static struct winusb_interface WinUSBX[SUB_API_MAX];
+static const char *sub_api_name[SUB_API_MAX] = WINUSBX_DRV_NAMES;
+
+static bool api_hid_available = false;
+#define CHECK_HID_AVAILABLE				\
+	do {						\
+		if (!api_hid_available)			\
+			return LIBUSB_ERROR_ACCESS;	\
+	} while (0)
+
+static inline BOOLEAN guid_eq(const GUID *guid1, const GUID *guid2)
+{
+	if ((guid1 != NULL) && (guid2 != NULL))
+		return (memcmp(guid1, guid2, sizeof(GUID)) == 0);
+
+	return false;
+}
+
+#if defined(ENABLE_LOGGING)
+static char *guid_to_string(const GUID *guid)
+{
+	static char guid_string[MAX_GUID_STRING_LENGTH];
+
+	if (guid == NULL)
+		return NULL;
+
+	sprintf(guid_string, "{%08X-%04X-%04X-%02X%02X-%02X%02X%02X%02X%02X%02X}",
+		(unsigned int)guid->Data1, guid->Data2, guid->Data3,
+		guid->Data4[0], guid->Data4[1], guid->Data4[2], guid->Data4[3],
+		guid->Data4[4], guid->Data4[5], guid->Data4[6], guid->Data4[7]);
+
+	return guid_string;
+}
+#endif
+
+/*
+ * Sanitize Microsoft's paths: convert to uppercase, add prefix and fix backslashes.
+ * Return an allocated sanitized string or NULL on error.
+ */
+static char *sanitize_path(const char *path)
+{
+	const char root_prefix[] = { '\\', '\\', '.', '\\' };
+	size_t j, size;
+	char *ret_path;
+	size_t add_root = 0;
+
+	if (path == NULL)
+		return NULL;
+
+	size = strlen(path) + 1;
+
+	// Microsoft indiscriminately uses '\\?\', '\\.\', '##?#" or "##.#" for root prefixes.
+	if (!((size > 3) && (((path[0] == '\\') && (path[1] == '\\') && (path[3] == '\\'))
+			|| ((path[0] == '#') && (path[1] == '#') && (path[3] == '#'))))) {
+		add_root = sizeof(root_prefix);
+		size += add_root;
+	}
+
+	ret_path = malloc(size);
+	if (ret_path == NULL)
+		return NULL;
+
+	strcpy(&ret_path[add_root], path);
+
+	// Ensure consistency with root prefix
+	memcpy(ret_path, root_prefix, sizeof(root_prefix));
+
+	// Same goes for '\' and '#' after the root prefix. Ensure '#' is used
+	for (j = sizeof(root_prefix); j < size; j++) {
+		ret_path[j] = (char)toupper((int)ret_path[j]); // Fix case too
+		if (ret_path[j] == '\\')
+			ret_path[j] = '#';
+	}
+
+	return ret_path;
+}
+
+/*
+ * Cfgmgr32, OLE32 and SetupAPI DLL functions
+ */
+static int init_dlls(void)
+{
+	DLL_GET_HANDLE(Cfgmgr32);
+	DLL_LOAD_FUNC(Cfgmgr32, CM_Get_Parent, TRUE);
+	DLL_LOAD_FUNC(Cfgmgr32, CM_Get_Child, TRUE);
+	DLL_LOAD_FUNC(Cfgmgr32, CM_Get_Sibling, TRUE);
+	DLL_LOAD_FUNC(Cfgmgr32, CM_Get_Device_IDA, TRUE);
+
+	// Prefixed to avoid conflict with header files
+	DLL_GET_HANDLE(AdvAPI32);
+	DLL_LOAD_FUNC_PREFIXED(AdvAPI32, p, RegQueryValueExW, TRUE);
+	DLL_LOAD_FUNC_PREFIXED(AdvAPI32, p, RegCloseKey, TRUE);
+
+	DLL_GET_HANDLE(Kernel32);
+	DLL_LOAD_FUNC_PREFIXED(Kernel32, p, IsWow64Process, FALSE);
+
+	DLL_GET_HANDLE(OLE32);
+	DLL_LOAD_FUNC_PREFIXED(OLE32, p, CLSIDFromString, TRUE);
+
+	DLL_GET_HANDLE(SetupAPI);
+	DLL_LOAD_FUNC_PREFIXED(SetupAPI, p, SetupDiGetClassDevsA, TRUE);
+	DLL_LOAD_FUNC_PREFIXED(SetupAPI, p, SetupDiEnumDeviceInfo, TRUE);
+	DLL_LOAD_FUNC_PREFIXED(SetupAPI, p, SetupDiEnumDeviceInterfaces, TRUE);
+	DLL_LOAD_FUNC_PREFIXED(SetupAPI, p, SetupDiGetDeviceInterfaceDetailA, TRUE);
+	DLL_LOAD_FUNC_PREFIXED(SetupAPI, p, SetupDiDestroyDeviceInfoList, TRUE);
+	DLL_LOAD_FUNC_PREFIXED(SetupAPI, p, SetupDiOpenDevRegKey, TRUE);
+	DLL_LOAD_FUNC_PREFIXED(SetupAPI, p, SetupDiGetDeviceRegistryPropertyA, TRUE);
+	DLL_LOAD_FUNC_PREFIXED(SetupAPI, p, SetupDiOpenDeviceInterfaceRegKey, TRUE);
+
+	return LIBUSB_SUCCESS;
+}
+
+static void exit_dlls(void)
+{
+	DLL_FREE_HANDLE(Cfgmgr32);
+	DLL_FREE_HANDLE(AdvAPI32);
+	DLL_FREE_HANDLE(Kernel32);
+	DLL_FREE_HANDLE(OLE32);
+	DLL_FREE_HANDLE(SetupAPI);
+}
+
+/*
+ * enumerate interfaces for the whole USB class
+ *
+ * Parameters:
+ * dev_info: a pointer to a dev_info list
+ * dev_info_data: a pointer to an SP_DEVINFO_DATA to be filled (or NULL if not needed)
+ * usb_class: the generic USB class for which to retrieve interface details
+ * index: zero based index of the interface in the device info list
+ *
+ * Note: it is the responsibility of the caller to free the DEVICE_INTERFACE_DETAIL_DATA
+ * structure returned and call this function repeatedly using the same guid (with an
+ * incremented index starting at zero) until all interfaces have been returned.
+ */
+static bool get_devinfo_data(struct libusb_context *ctx,
+	HDEVINFO *dev_info, SP_DEVINFO_DATA *dev_info_data, const char *usb_class, unsigned _index)
+{
+	if (_index <= 0) {
+		*dev_info = pSetupDiGetClassDevsA(NULL, usb_class, NULL, DIGCF_PRESENT|DIGCF_ALLCLASSES);
+		if (*dev_info == INVALID_HANDLE_VALUE)
+			return false;
+	}
+
+	dev_info_data->cbSize = sizeof(SP_DEVINFO_DATA);
+	if (!pSetupDiEnumDeviceInfo(*dev_info, _index, dev_info_data)) {
+		if (GetLastError() != ERROR_NO_MORE_ITEMS)
+			usbi_err(ctx, "Could not obtain device info data for index %u: %s",
+				_index, windows_error_str(0));
+
+		pSetupDiDestroyDeviceInfoList(*dev_info);
+		*dev_info = INVALID_HANDLE_VALUE;
+		return false;
+	}
+	return true;
+}
+
+/*
+ * enumerate interfaces for a specific GUID
+ *
+ * Parameters:
+ * dev_info: a pointer to a dev_info list
+ * dev_info_data: a pointer to an SP_DEVINFO_DATA to be filled (or NULL if not needed)
+ * guid: the GUID for which to retrieve interface details
+ * index: zero based index of the interface in the device info list
+ *
+ * Note: it is the responsibility of the caller to free the DEVICE_INTERFACE_DETAIL_DATA
+ * structure returned and call this function repeatedly using the same guid (with an
+ * incremented index starting at zero) until all interfaces have been returned.
+ */
+static SP_DEVICE_INTERFACE_DETAIL_DATA_A *get_interface_details(struct libusb_context *ctx,
+	HDEVINFO *dev_info, SP_DEVINFO_DATA *dev_info_data, const GUID *guid, unsigned _index)
+{
+	SP_DEVICE_INTERFACE_DATA dev_interface_data;
+	SP_DEVICE_INTERFACE_DETAIL_DATA_A *dev_interface_details;
+	DWORD size;
+
+	if (_index <= 0)
+		*dev_info = pSetupDiGetClassDevsA(guid, NULL, NULL, DIGCF_PRESENT|DIGCF_DEVICEINTERFACE);
+
+	if (dev_info_data != NULL) {
+		dev_info_data->cbSize = sizeof(SP_DEVINFO_DATA);
+		if (!pSetupDiEnumDeviceInfo(*dev_info, _index, dev_info_data)) {
+			if (GetLastError() != ERROR_NO_MORE_ITEMS)
+				usbi_err(ctx, "Could not obtain device info data for index %u: %s",
+					_index, windows_error_str(0));
+
+			pSetupDiDestroyDeviceInfoList(*dev_info);
+			*dev_info = INVALID_HANDLE_VALUE;
+			return NULL;
+		}
+	}
+
+	dev_interface_data.cbSize = sizeof(SP_DEVICE_INTERFACE_DATA);
+	if (!pSetupDiEnumDeviceInterfaces(*dev_info, NULL, guid, _index, &dev_interface_data)) {
+		if (GetLastError() != ERROR_NO_MORE_ITEMS)
+			usbi_err(ctx, "Could not obtain interface data for index %u: %s",
+				_index, windows_error_str(0));
+
+		pSetupDiDestroyDeviceInfoList(*dev_info);
+		*dev_info = INVALID_HANDLE_VALUE;
+		return NULL;
+	}
+
+	// Read interface data (dummy + actual) to access the device path
+	if (!pSetupDiGetDeviceInterfaceDetailA(*dev_info, &dev_interface_data, NULL, 0, &size, NULL)) {
+		// The dummy call should fail with ERROR_INSUFFICIENT_BUFFER
+		if (GetLastError() != ERROR_INSUFFICIENT_BUFFER) {
+			usbi_err(ctx, "could not access interface data (dummy) for index %u: %s",
+				_index, windows_error_str(0));
+			goto err_exit;
+		}
+	} else {
+		usbi_err(ctx, "program assertion failed - http://msdn.microsoft.com/en-us/library/ms792901.aspx is wrong.");
+		goto err_exit;
+	}
+
+	dev_interface_details = calloc(1, size);
+	if (dev_interface_details == NULL) {
+		usbi_err(ctx, "could not allocate interface data for index %u.", _index);
+		goto err_exit;
+	}
+
+	dev_interface_details->cbSize = sizeof(SP_DEVICE_INTERFACE_DETAIL_DATA_A);
+	if (!pSetupDiGetDeviceInterfaceDetailA(*dev_info, &dev_interface_data,
+		dev_interface_details, size, &size, NULL)) {
+		usbi_err(ctx, "could not access interface data (actual) for index %u: %s",
+			_index, windows_error_str(0));
+	}
+
+	return dev_interface_details;
+
+err_exit:
+	pSetupDiDestroyDeviceInfoList(*dev_info);
+	*dev_info = INVALID_HANDLE_VALUE;
+	return NULL;
+}
+
+/* For libusb0 filter */
+static SP_DEVICE_INTERFACE_DETAIL_DATA_A *get_interface_details_filter(struct libusb_context *ctx,
+	HDEVINFO *dev_info, SP_DEVINFO_DATA *dev_info_data, const GUID *guid, unsigned _index, char *filter_path)
+{
+	SP_DEVICE_INTERFACE_DATA dev_interface_data;
+	SP_DEVICE_INTERFACE_DETAIL_DATA_A *dev_interface_details;
+	DWORD size;
+
+	if (_index <= 0)
+		*dev_info = pSetupDiGetClassDevsA(guid, NULL, NULL, DIGCF_PRESENT|DIGCF_DEVICEINTERFACE);
+
+	if (dev_info_data != NULL) {
+		dev_info_data->cbSize = sizeof(SP_DEVINFO_DATA);
+		if (!pSetupDiEnumDeviceInfo(*dev_info, _index, dev_info_data)) {
+			if (GetLastError() != ERROR_NO_MORE_ITEMS)
+				usbi_err(ctx, "Could not obtain device info data for index %u: %s",
+					_index, windows_error_str(0));
+
+			pSetupDiDestroyDeviceInfoList(*dev_info);
+			*dev_info = INVALID_HANDLE_VALUE;
+			return NULL;
+		}
+	}
+
+	dev_interface_data.cbSize = sizeof(SP_DEVICE_INTERFACE_DATA);
+	if (!pSetupDiEnumDeviceInterfaces(*dev_info, NULL, guid, _index, &dev_interface_data)) {
+		if (GetLastError() != ERROR_NO_MORE_ITEMS)
+			usbi_err(ctx, "Could not obtain interface data for index %u: %s",
+				_index, windows_error_str(0));
+
+		pSetupDiDestroyDeviceInfoList(*dev_info);
+		*dev_info = INVALID_HANDLE_VALUE;
+		return NULL;
+	}
+
+	// Read interface data (dummy + actual) to access the device path
+	if (!pSetupDiGetDeviceInterfaceDetailA(*dev_info, &dev_interface_data, NULL, 0, &size, NULL)) {
+		// The dummy call should fail with ERROR_INSUFFICIENT_BUFFER
+		if (GetLastError() != ERROR_INSUFFICIENT_BUFFER) {
+			usbi_err(ctx, "could not access interface data (dummy) for index %u: %s",
+				_index, windows_error_str(0));
+			goto err_exit;
+		}
+	} else {
+		usbi_err(ctx, "program assertion failed - http://msdn.microsoft.com/en-us/library/ms792901.aspx is wrong.");
+		goto err_exit;
+	}
+
+	dev_interface_details = calloc(1, size);
+	if (dev_interface_details == NULL) {
+		usbi_err(ctx, "could not allocate interface data for index %u.", _index);
+		goto err_exit;
+	}
+
+	dev_interface_details->cbSize = sizeof(SP_DEVICE_INTERFACE_DETAIL_DATA_A);
+	if (!pSetupDiGetDeviceInterfaceDetailA(*dev_info, &dev_interface_data, dev_interface_details, size, &size, NULL))
+		usbi_err(ctx, "could not access interface data (actual) for index %u: %s",
+			_index, windows_error_str(0));
+
+	// [trobinso] lookup the libusb0 symbolic index.
+	if (dev_interface_details) {
+		HKEY hkey_device_interface = pSetupDiOpenDeviceInterfaceRegKey(*dev_info, &dev_interface_data, 0, KEY_READ);
+		if (hkey_device_interface != INVALID_HANDLE_VALUE) {
+			DWORD libusb0_symboliclink_index = 0;
+			DWORD value_length = sizeof(DWORD);
+			DWORD value_type = 0;
+			LONG status;
+
+			status = pRegQueryValueExW(hkey_device_interface, L"LUsb0", NULL, &value_type,
+				(LPBYTE)&libusb0_symboliclink_index, &value_length);
+			if (status == ERROR_SUCCESS) {
+				if (libusb0_symboliclink_index < 256) {
+					// libusb0.sys is connected to this device instance.
+					// If the the device interface guid is {F9F3FF14-AE21-48A0-8A25-8011A7A931D9} then it's a filter.
+					sprintf(filter_path, "\\\\.\\libusb0-%04u", (unsigned int)libusb0_symboliclink_index);
+					usbi_dbg("assigned libusb0 symbolic link %s", filter_path);
+				} else {
+					// libusb0.sys was connected to this device instance at one time; but not anymore.
+				}
+			}
+			pRegCloseKey(hkey_device_interface);
+		}
+	}
+
+	return dev_interface_details;
+
+err_exit:
+	pSetupDiDestroyDeviceInfoList(*dev_info);
+	*dev_info = INVALID_HANDLE_VALUE;
+	return NULL;
+}
+
+/*
+ * Returns the session ID of a device's nth level ancestor
+ * If there's no device at the nth level, return 0
+ */
+static unsigned long get_ancestor_session_id(DWORD devinst, unsigned level)
+{
+	DWORD parent_devinst;
+	unsigned long session_id;
+	char *sanitized_path;
+	char path[MAX_PATH_LENGTH];
+	unsigned i;
+
+	if (level < 1)
+		return 0;
+
+	for (i = 0; i < level; i++) {
+		if (CM_Get_Parent(&parent_devinst, devinst, 0) != CR_SUCCESS)
+			return 0;
+		devinst = parent_devinst;
+	}
+
+	if (CM_Get_Device_IDA(devinst, path, MAX_PATH_LENGTH, 0) != CR_SUCCESS)
+		return 0;
+
+	// TODO: (post hotplug): try without sanitizing
+	sanitized_path = sanitize_path(path);
+	if (sanitized_path == NULL)
+		return 0;
+
+	session_id = htab_hash(sanitized_path);
+	free(sanitized_path);
+	return session_id;
+}
+
+/*
+ * Determine which interface the given endpoint address belongs to
+ */
+static int get_interface_by_endpoint(struct libusb_config_descriptor *conf_desc, uint8_t ep)
+{
+	const struct libusb_interface *intf;
+	const struct libusb_interface_descriptor *intf_desc;
+	int i, j, k;
+
+	for (i = 0; i < conf_desc->bNumInterfaces; i++) {
+		intf = &conf_desc->interface[i];
+		for (j = 0; j < intf->num_altsetting; j++) {
+			intf_desc = &intf->altsetting[j];
+			for (k = 0; k < intf_desc->bNumEndpoints; k++) {
+				if (intf_desc->endpoint[k].bEndpointAddress == ep) {
+					usbi_dbg("found endpoint %02X on interface %d", intf_desc->bInterfaceNumber, i);
+					return intf_desc->bInterfaceNumber;
+				}
+			}
+		}
+	}
+
+	usbi_dbg("endpoint %02X not found on any interface", ep);
+	return LIBUSB_ERROR_NOT_FOUND;
+}
+
+/*
+ * Populate the endpoints addresses of the device_priv interface helper structs
+ */
+static int windows_assign_endpoints(struct libusb_device_handle *dev_handle, int iface, int altsetting)
+{
+	int i, r;
+	struct windows_device_priv *priv = _device_priv(dev_handle->dev);
+	struct libusb_config_descriptor *conf_desc;
+	const struct libusb_interface_descriptor *if_desc;
+	struct libusb_context *ctx = DEVICE_CTX(dev_handle->dev);
+
+	r = libusb_get_active_config_descriptor(dev_handle->dev, &conf_desc);
+	if (r != LIBUSB_SUCCESS) {
+		usbi_warn(ctx, "could not read config descriptor: error %d", r);
+		return r;
+	}
+
+	if_desc = &conf_desc->interface[iface].altsetting[altsetting];
+	safe_free(priv->usb_interface[iface].endpoint);
+
+	if (if_desc->bNumEndpoints == 0) {
+		usbi_dbg("no endpoints found for interface %d", iface);
+		libusb_free_config_descriptor(conf_desc);
+		return LIBUSB_SUCCESS;
+	}
+
+	priv->usb_interface[iface].endpoint = malloc(if_desc->bNumEndpoints);
+	if (priv->usb_interface[iface].endpoint == NULL) {
+		libusb_free_config_descriptor(conf_desc);
+		return LIBUSB_ERROR_NO_MEM;
+	}
+
+	priv->usb_interface[iface].nb_endpoints = if_desc->bNumEndpoints;
+	for (i = 0; i < if_desc->bNumEndpoints; i++) {
+		priv->usb_interface[iface].endpoint[i] = if_desc->endpoint[i].bEndpointAddress;
+		usbi_dbg("(re)assigned endpoint %02X to interface %d", priv->usb_interface[iface].endpoint[i], iface);
+	}
+	libusb_free_config_descriptor(conf_desc);
+
+	// Extra init may be required to configure endpoints
+	return priv->apib->configure_endpoints(SUB_API_NOTSET, dev_handle, iface);
+}
+
+// Lookup for a match in the list of API driver names
+// return -1 if not found, driver match number otherwise
+static int get_sub_api(char *driver, int api)
+{
+	int i;
+	const char sep_str[2] = {LIST_SEPARATOR, 0};
+	char *tok, *tmp_str;
+	size_t len = strlen(driver);
+
+	if (len == 0)
+		return SUB_API_NOTSET;
+
+	tmp_str = _strdup(driver);
+	if (tmp_str == NULL)
+		return SUB_API_NOTSET;
+
+	tok = strtok(tmp_str, sep_str);
+	while (tok != NULL) {
+		for (i = 0; i < usb_api_backend[api].nb_driver_names; i++) {
+			if (_stricmp(tok, usb_api_backend[api].driver_name_list[i]) == 0) {
+				free(tmp_str);
+				return i;
+			}
+		}
+		tok = strtok(NULL, sep_str);
+	}
+
+	free(tmp_str);
+	return SUB_API_NOTSET;
+}
+
+/*
+ * auto-claiming and auto-release helper functions
+ */
+static int auto_claim(struct libusb_transfer *transfer, int *interface_number, int api_type)
+{
+	struct libusb_context *ctx = DEVICE_CTX(transfer->dev_handle->dev);
+	struct windows_device_handle_priv *handle_priv = _device_handle_priv(
+		transfer->dev_handle);
+	struct windows_device_priv *priv = _device_priv(transfer->dev_handle->dev);
+	int current_interface = *interface_number;
+	int r = LIBUSB_SUCCESS;
+
+	switch(api_type) {
+	case USB_API_WINUSBX:
+	case USB_API_HID:
+		break;
+	default:
+		return LIBUSB_ERROR_INVALID_PARAM;
+	}
+
+	usbi_mutex_lock(&autoclaim_lock);
+	if (current_interface < 0) { // No serviceable interface was found
+		for (current_interface = 0; current_interface < USB_MAXINTERFACES; current_interface++) {
+			// Must claim an interface of the same API type
+			if ((priv->usb_interface[current_interface].apib->id == api_type)
+					&& (libusb_claim_interface(transfer->dev_handle, current_interface) == LIBUSB_SUCCESS)) {
+				usbi_dbg("auto-claimed interface %d for control request", current_interface);
+				if (handle_priv->autoclaim_count[current_interface] != 0)
+					usbi_warn(ctx, "program assertion failed - autoclaim_count was nonzero");
+				handle_priv->autoclaim_count[current_interface]++;
+				break;
+			}
+		}
+		if (current_interface == USB_MAXINTERFACES) {
+			usbi_err(ctx, "could not auto-claim any interface");
+			r = LIBUSB_ERROR_NOT_FOUND;
+		}
+	} else {
+		// If we have a valid interface that was autoclaimed, we must increment
+		// its autoclaim count so that we can prevent an early release.
+		if (handle_priv->autoclaim_count[current_interface] != 0)
+			handle_priv->autoclaim_count[current_interface]++;
+	}
+	usbi_mutex_unlock(&autoclaim_lock);
+
+	*interface_number = current_interface;
+	return r;
+}
+
+static void auto_release(struct usbi_transfer *itransfer)
+{
+	struct windows_transfer_priv *transfer_priv = usbi_transfer_get_os_priv(itransfer);
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	libusb_device_handle *dev_handle = transfer->dev_handle;
+	struct windows_device_handle_priv *handle_priv = _device_handle_priv(dev_handle);
+	int r;
+
+	usbi_mutex_lock(&autoclaim_lock);
+	if (handle_priv->autoclaim_count[transfer_priv->interface_number] > 0) {
+		handle_priv->autoclaim_count[transfer_priv->interface_number]--;
+		if (handle_priv->autoclaim_count[transfer_priv->interface_number] == 0) {
+			r = libusb_release_interface(dev_handle, transfer_priv->interface_number);
+			if (r == LIBUSB_SUCCESS)
+				usbi_dbg("auto-released interface %d", transfer_priv->interface_number);
+			else
+				usbi_dbg("failed to auto-release interface %d (%s)",
+					transfer_priv->interface_number, libusb_error_name((enum libusb_error)r));
+		}
+	}
+	usbi_mutex_unlock(&autoclaim_lock);
+}
+
+/* Windows version dtection */
+static BOOL is_x64(void)
+{
+	BOOL ret = FALSE;
+
+	// Detect if we're running a 32 or 64 bit system
+	if (sizeof(uintptr_t) < 8) {
+		if (pIsWow64Process != NULL)
+			pIsWow64Process(GetCurrentProcess(), &ret);
+	} else {
+		ret = TRUE;
+	}
+
+	return ret;
+}
+
+static void get_windows_version(void)
+{
+	OSVERSIONINFOEXA vi, vi2;
+	const char *arch, *w = NULL;
+	unsigned major, minor;
+	ULONGLONG major_equal, minor_equal;
+	BOOL ws;
+
+	memset(&vi, 0, sizeof(vi));
+	vi.dwOSVersionInfoSize = sizeof(vi);
+	if (!GetVersionExA((OSVERSIONINFOA *)&vi)) {
+		memset(&vi, 0, sizeof(vi));
+		vi.dwOSVersionInfoSize = sizeof(OSVERSIONINFOA);
+		if (!GetVersionExA((OSVERSIONINFOA *)&vi))
+			return;
+	}
+
+	if (vi.dwPlatformId == VER_PLATFORM_WIN32_NT) {
+		if (vi.dwMajorVersion > 6 || (vi.dwMajorVersion == 6 && vi.dwMinorVersion >= 2)) {
+			// Starting with Windows 8.1 Preview, GetVersionEx() does no longer report the actual OS version
+			// See: http://msdn.microsoft.com/en-us/library/windows/desktop/dn302074.aspx
+
+			major_equal = VerSetConditionMask(0, VER_MAJORVERSION, VER_EQUAL);
+			for (major = vi.dwMajorVersion; major <= 9; major++) {
+				memset(&vi2, 0, sizeof(vi2));
+				vi2.dwOSVersionInfoSize = sizeof(vi2);
+				vi2.dwMajorVersion = major;
+				if (!VerifyVersionInfoA(&vi2, VER_MAJORVERSION, major_equal))
+					continue;
+
+				if (vi.dwMajorVersion < major) {
+					vi.dwMajorVersion = major;
+					vi.dwMinorVersion = 0;
+				}
+
+				minor_equal = VerSetConditionMask(0, VER_MINORVERSION, VER_EQUAL);
+				for (minor = vi.dwMinorVersion; minor <= 9; minor++) {
+					memset(&vi2, 0, sizeof(vi2));
+					vi2.dwOSVersionInfoSize = sizeof(vi2);
+					vi2.dwMinorVersion = minor;
+					if (!VerifyVersionInfoA(&vi2, VER_MINORVERSION, minor_equal))
+						continue;
+
+					vi.dwMinorVersion = minor;
+					break;
+				}
+
+				break;
+			}
+		}
+
+		if (vi.dwMajorVersion <= 0xf && vi.dwMinorVersion <= 0xf) {
+			ws = (vi.wProductType <= VER_NT_WORKSTATION);
+			windows_version = vi.dwMajorVersion << 4 | vi.dwMinorVersion;
+			switch (windows_version) {
+			case 0x50: w = "2000"; break;
+			case 0x51: w = "XP"; break;
+			case 0x52: w = "2003"; break;
+			case 0x60: w = (ws ? "Vista" : "2008"); break;
+			case 0x61: w = (ws ? "7" : "2008_R2"); break;
+			case 0x62: w = (ws ? "8" : "2012"); break;
+			case 0x63: w = (ws ? "8.1" : "2012_R2"); break;
+			case 0x64: w = (ws ? "10" : "2015"); break;
+			default:
+				if (windows_version < 0x50)
+					windows_version = WINDOWS_UNSUPPORTED;
+				else
+					w = "11 or later";
+				break;
+			}
+		}
+	}
+
+	arch = is_x64() ? "64-bit" : "32-bit";
+
+	if (w == NULL)
+		snprintf(windows_version_str, sizeof(windows_version_str), "%s %u.%u %s",
+			(vi.dwPlatformId == VER_PLATFORM_WIN32_NT ? "NT" : "??"),
+			(unsigned int)vi.dwMajorVersion, (unsigned int)vi.dwMinorVersion, arch);
+	else if (vi.wServicePackMinor)
+		snprintf(windows_version_str, sizeof(windows_version_str), "%s SP%u.%u %s",
+			w, vi.wServicePackMajor, vi.wServicePackMinor, arch);
+	else if (vi.wServicePackMajor)
+		snprintf(windows_version_str, sizeof(windows_version_str), "%s SP%u %s",
+			w, vi.wServicePackMajor, arch);
+	else
+		snprintf(windows_version_str, sizeof(windows_version_str), "%s %s",
+			w, arch);
+}
+
+/*
+ * init: libusb backend init function
+ *
+ * This function enumerates the HCDs (Host Controller Drivers) and populates our private HCD list
+ * In our implementation, we equate Windows' "HCD" to libusb's "bus". Note that bus is zero indexed.
+ * HCDs are not expected to change after init (might not hold true for hot pluggable USB PCI card?)
+ */
+static int windows_init(struct libusb_context *ctx)
+{
+	int i, r = LIBUSB_ERROR_OTHER;
+	HANDLE semaphore;
+	char sem_name[11 + 8 + 1]; // strlen("libusb_init") + (32-bit hex PID) + '\0'
+
+	sprintf(sem_name, "libusb_init%08X", (unsigned int)(GetCurrentProcessId() & 0xFFFFFFFF));
+	semaphore = CreateSemaphoreA(NULL, 1, 1, sem_name);
+	if (semaphore == NULL) {
+		usbi_err(ctx, "could not create semaphore: %s", windows_error_str(0));
+		return LIBUSB_ERROR_NO_MEM;
+	}
+
+	// A successful wait brings our semaphore count to 0 (unsignaled)
+	// => any concurent wait stalls until the semaphore's release
+	if (WaitForSingleObject(semaphore, INFINITE) != WAIT_OBJECT_0) {
+		usbi_err(ctx, "failure to access semaphore: %s", windows_error_str(0));
+		CloseHandle(semaphore);
+		return LIBUSB_ERROR_NO_MEM;
+	}
+
+	// NB: concurrent usage supposes that init calls are equally balanced with
+	// exit calls. If init is called more than exit, we will not exit properly
+	if (++concurrent_usage == 0) { // First init?
+		get_windows_version();
+		usbi_dbg("Windows %s", windows_version_str);
+
+		if (windows_version == WINDOWS_UNSUPPORTED) {
+			usbi_err(ctx, "This version of Windows is NOT supported");
+			r = LIBUSB_ERROR_NOT_SUPPORTED;
+			goto init_exit;
+		}
+
+		// We need a lock for proper auto-release
+		usbi_mutex_init(&autoclaim_lock);
+
+		// Initialize pollable file descriptors
+		init_polling();
+
+		// Load DLL imports
+		if (init_dlls() != LIBUSB_SUCCESS) {
+			usbi_err(ctx, "could not resolve DLL functions");
+			goto init_exit;
+		}
+
+		// Initialize the low level APIs (we don't care about errors at this stage)
+		for (i = 0; i < USB_API_MAX; i++)
+			usb_api_backend[i].init(SUB_API_NOTSET, ctx);
+
+		r = windows_common_init(ctx);
+		if (r)
+			goto init_exit;
+	}
+	// At this stage, either we went through full init successfully, or didn't need to
+	r = LIBUSB_SUCCESS;
+
+init_exit: // Holds semaphore here.
+	if (!concurrent_usage && r != LIBUSB_SUCCESS) { // First init failed?
+		for (i = 0; i < USB_API_MAX; i++)
+			usb_api_backend[i].exit(SUB_API_NOTSET);
+		exit_dlls();
+		exit_polling();
+		windows_common_exit();
+		usbi_mutex_destroy(&autoclaim_lock);
+	}
+
+	if (r != LIBUSB_SUCCESS)
+		--concurrent_usage; // Not expected to call libusb_exit if we failed.
+
+	ReleaseSemaphore(semaphore, 1, NULL); // increase count back to 1
+	CloseHandle(semaphore);
+	return r;
+}
+
+/*
+ * HCD (root) hubs need to have their device descriptor manually populated
+ *
+ * Note that, like Microsoft does in the device manager, we populate the
+ * Vendor and Device ID for HCD hubs with the ones from the PCI HCD device.
+ */
+static int force_hcd_device_descriptor(struct libusb_device *dev)
+{
+	struct windows_device_priv *parent_priv, *priv = _device_priv(dev);
+	struct libusb_context *ctx = DEVICE_CTX(dev);
+	int vid, pid;
+
+	dev->num_configurations = 1;
+	priv->dev_descriptor.bLength = sizeof(USB_DEVICE_DESCRIPTOR);
+	priv->dev_descriptor.bDescriptorType = USB_DEVICE_DESCRIPTOR_TYPE;
+	priv->dev_descriptor.bNumConfigurations = 1;
+	priv->active_config = 1;
+
+	if (dev->parent_dev == NULL) {
+		usbi_err(ctx, "program assertion failed - HCD hub has no parent");
+		return LIBUSB_ERROR_NO_DEVICE;
+	}
+
+	parent_priv = _device_priv(dev->parent_dev);
+	if (sscanf(parent_priv->path, "\\\\.\\PCI#VEN_%04x&DEV_%04x%*s", &vid, &pid) == 2) {
+		priv->dev_descriptor.idVendor = (uint16_t)vid;
+		priv->dev_descriptor.idProduct = (uint16_t)pid;
+	} else {
+		usbi_warn(ctx, "could not infer VID/PID of HCD hub from '%s'", parent_priv->path);
+		priv->dev_descriptor.idVendor = 0x1d6b; // Linux Foundation root hub
+		priv->dev_descriptor.idProduct = 1;
+	}
+
+	return LIBUSB_SUCCESS;
+}
+
+/*
+ * fetch and cache all the config descriptors through I/O
+ */
+static int cache_config_descriptors(struct libusb_device *dev, HANDLE hub_handle, char *device_id)
+{
+	DWORD size, ret_size;
+	struct libusb_context *ctx = DEVICE_CTX(dev);
+	struct windows_device_priv *priv = _device_priv(dev);
+	int r;
+	uint8_t i;
+
+	USB_CONFIGURATION_DESCRIPTOR_SHORT cd_buf_short; // dummy request
+	PUSB_DESCRIPTOR_REQUEST cd_buf_actual = NULL;    // actual request
+	PUSB_CONFIGURATION_DESCRIPTOR cd_data = NULL;
+
+	if (dev->num_configurations == 0)
+		return LIBUSB_ERROR_INVALID_PARAM;
+
+	priv->config_descriptor = calloc(dev->num_configurations, sizeof(unsigned char *));
+	if (priv->config_descriptor == NULL)
+		return LIBUSB_ERROR_NO_MEM;
+
+	for (i = 0; i < dev->num_configurations; i++)
+		priv->config_descriptor[i] = NULL;
+
+	for (i = 0, r = LIBUSB_SUCCESS; ; i++) {
+		// safe loop: release all dynamic resources
+		safe_free(cd_buf_actual);
+
+		// safe loop: end of loop condition
+		if ((i >= dev->num_configurations) || (r != LIBUSB_SUCCESS))
+			break;
+
+		size = sizeof(USB_CONFIGURATION_DESCRIPTOR_SHORT);
+		memset(&cd_buf_short, 0, size);
+
+		cd_buf_short.req.ConnectionIndex = (ULONG)priv->port;
+		cd_buf_short.req.SetupPacket.bmRequest = LIBUSB_ENDPOINT_IN;
+		cd_buf_short.req.SetupPacket.bRequest = USB_REQUEST_GET_DESCRIPTOR;
+		cd_buf_short.req.SetupPacket.wValue = (USB_CONFIGURATION_DESCRIPTOR_TYPE << 8) | i;
+		cd_buf_short.req.SetupPacket.wIndex = 0;
+		cd_buf_short.req.SetupPacket.wLength = (USHORT)(size - sizeof(USB_DESCRIPTOR_REQUEST));
+
+		// Dummy call to get the required data size. Initial failures are reported as info rather
+		// than error as they can occur for non-penalizing situations, such as with some hubs.
+		// coverity[tainted_data_argument]
+		if (!DeviceIoControl(hub_handle, IOCTL_USB_GET_DESCRIPTOR_FROM_NODE_CONNECTION, &cd_buf_short, size,
+			&cd_buf_short, size, &ret_size, NULL)) {
+			usbi_info(ctx, "could not access configuration descriptor (dummy) for '%s': %s", device_id, windows_error_str(0));
+			LOOP_BREAK(LIBUSB_ERROR_IO);
+		}
+
+		if ((ret_size != size) || (cd_buf_short.data.wTotalLength < sizeof(USB_CONFIGURATION_DESCRIPTOR))) {
+			usbi_info(ctx, "unexpected configuration descriptor size (dummy) for '%s'.", device_id);
+			LOOP_BREAK(LIBUSB_ERROR_IO);
+		}
+
+		size = sizeof(USB_DESCRIPTOR_REQUEST) + cd_buf_short.data.wTotalLength;
+		cd_buf_actual = calloc(1, size);
+		if (cd_buf_actual == NULL) {
+			usbi_err(ctx, "could not allocate configuration descriptor buffer for '%s'.", device_id);
+			LOOP_BREAK(LIBUSB_ERROR_NO_MEM);
+		}
+
+		// Actual call
+		cd_buf_actual->ConnectionIndex = (ULONG)priv->port;
+		cd_buf_actual->SetupPacket.bmRequest = LIBUSB_ENDPOINT_IN;
+		cd_buf_actual->SetupPacket.bRequest = USB_REQUEST_GET_DESCRIPTOR;
+		cd_buf_actual->SetupPacket.wValue = (USB_CONFIGURATION_DESCRIPTOR_TYPE << 8) | i;
+		cd_buf_actual->SetupPacket.wIndex = 0;
+		cd_buf_actual->SetupPacket.wLength = (USHORT)(size - sizeof(USB_DESCRIPTOR_REQUEST));
+
+		if (!DeviceIoControl(hub_handle, IOCTL_USB_GET_DESCRIPTOR_FROM_NODE_CONNECTION, cd_buf_actual, size,
+			cd_buf_actual, size, &ret_size, NULL)) {
+			usbi_err(ctx, "could not access configuration descriptor (actual) for '%s': %s", device_id, windows_error_str(0));
+			LOOP_BREAK(LIBUSB_ERROR_IO);
+		}
+
+		cd_data = (PUSB_CONFIGURATION_DESCRIPTOR)((UCHAR *)cd_buf_actual + sizeof(USB_DESCRIPTOR_REQUEST));
+
+		if ((size != ret_size) || (cd_data->wTotalLength != cd_buf_short.data.wTotalLength)) {
+			usbi_err(ctx, "unexpected configuration descriptor size (actual) for '%s'.", device_id);
+			LOOP_BREAK(LIBUSB_ERROR_IO);
+		}
+
+		if (cd_data->bDescriptorType != USB_CONFIGURATION_DESCRIPTOR_TYPE) {
+			usbi_err(ctx, "not a configuration descriptor for '%s'", device_id);
+			LOOP_BREAK(LIBUSB_ERROR_IO);
+		}
+
+		usbi_dbg("cached config descriptor %d (bConfigurationValue=%u, %u bytes)",
+			i, cd_data->bConfigurationValue, cd_data->wTotalLength);
+
+		// Cache the descriptor
+		priv->config_descriptor[i] = malloc(cd_data->wTotalLength);
+		if (priv->config_descriptor[i] == NULL)
+			LOOP_BREAK(LIBUSB_ERROR_NO_MEM);
+		memcpy(priv->config_descriptor[i], cd_data, cd_data->wTotalLength);
+	}
+	return LIBUSB_SUCCESS;
+}
+
+/*
+ * Populate a libusb device structure
+ */
+static int init_device(struct libusb_device *dev, struct libusb_device *parent_dev,
+	uint8_t port_number, char *device_id, DWORD devinst)
+{
+	HANDLE handle;
+	DWORD size;
+	USB_NODE_CONNECTION_INFORMATION_EX conn_info;
+	USB_NODE_CONNECTION_INFORMATION_EX_V2 conn_info_v2;
+	struct windows_device_priv *priv, *parent_priv;
+	struct libusb_context *ctx;
+	struct libusb_device *tmp_dev;
+	unsigned long tmp_id;
+	unsigned i;
+
+	if ((dev == NULL) || (parent_dev == NULL))
+		return LIBUSB_ERROR_NOT_FOUND;
+
+	ctx = DEVICE_CTX(dev);
+	priv = _device_priv(dev);
+	parent_priv = _device_priv(parent_dev);
+	if (parent_priv->apib->id != USB_API_HUB) {
+		usbi_warn(ctx, "parent for device '%s' is not a hub", device_id);
+		return LIBUSB_ERROR_NOT_FOUND;
+	}
+
+	// It is possible for the parent hub not to have been initialized yet
+	// If that's the case, lookup the ancestors to set the bus number
+	if (parent_dev->bus_number == 0) {
+		for (i = 2; ; i++) {
+			tmp_id = get_ancestor_session_id(devinst, i);
+			if (tmp_id == 0)
+				break;
+
+			tmp_dev = usbi_get_device_by_session_id(ctx, tmp_id);
+			if (tmp_dev == NULL)
+				continue;
+
+			if (tmp_dev->bus_number != 0) {
+				usbi_dbg("got bus number from ancestor #%u", i);
+				parent_dev->bus_number = tmp_dev->bus_number;
+				libusb_unref_device(tmp_dev);
+				break;
+			}
+
+			libusb_unref_device(tmp_dev);
+		}
+	}
+
+	if (parent_dev->bus_number == 0) {
+		usbi_err(ctx, "program assertion failed: unable to find ancestor bus number for '%s'", device_id);
+		return LIBUSB_ERROR_NOT_FOUND;
+	}
+
+	dev->bus_number = parent_dev->bus_number;
+	priv->port = port_number;
+	dev->port_number = port_number;
+	priv->depth = parent_priv->depth + 1;
+	dev->parent_dev = parent_dev;
+
+	// If the device address is already set, we can stop here
+	if (dev->device_address != 0)
+		return LIBUSB_SUCCESS;
+
+	memset(&conn_info, 0, sizeof(conn_info));
+	if (priv->depth != 0) { // Not a HCD hub
+		handle = CreateFileA(parent_priv->path, GENERIC_WRITE, FILE_SHARE_WRITE, NULL, OPEN_EXISTING,
+			FILE_FLAG_OVERLAPPED, NULL);
+		if (handle == INVALID_HANDLE_VALUE) {
+			usbi_warn(ctx, "could not open hub %s: %s", parent_priv->path, windows_error_str(0));
+			return LIBUSB_ERROR_ACCESS;
+		}
+
+		size = sizeof(conn_info);
+		conn_info.ConnectionIndex = (ULONG)port_number;
+		// coverity[tainted_data_argument]
+		if (!DeviceIoControl(handle, IOCTL_USB_GET_NODE_CONNECTION_INFORMATION_EX, &conn_info, size,
+			&conn_info, size, &size, NULL)) {
+			usbi_warn(ctx, "could not get node connection information for device '%s': %s",
+				device_id, windows_error_str(0));
+			CloseHandle(handle);
+			return LIBUSB_ERROR_NO_DEVICE;
+		}
+
+		if (conn_info.ConnectionStatus == NoDeviceConnected) {
+			usbi_err(ctx, "device '%s' is no longer connected!", device_id);
+			CloseHandle(handle);
+			return LIBUSB_ERROR_NO_DEVICE;
+		}
+
+		memcpy(&priv->dev_descriptor, &(conn_info.DeviceDescriptor), sizeof(USB_DEVICE_DESCRIPTOR));
+		dev->num_configurations = priv->dev_descriptor.bNumConfigurations;
+		priv->active_config = conn_info.CurrentConfigurationValue;
+		usbi_dbg("found %u configurations (active conf: %u)", dev->num_configurations, priv->active_config);
+
+		// If we can't read the config descriptors, just set the number of confs to zero
+		if (cache_config_descriptors(dev, handle, device_id) != LIBUSB_SUCCESS) {
+			dev->num_configurations = 0;
+			priv->dev_descriptor.bNumConfigurations = 0;
+		}
+
+		// In their great wisdom, Microsoft decided to BREAK the USB speed report between Windows 7 and Windows 8
+		if (windows_version >= WINDOWS_8) {
+			memset(&conn_info_v2, 0, sizeof(conn_info_v2));
+			size = sizeof(conn_info_v2);
+			conn_info_v2.ConnectionIndex = (ULONG)port_number;
+			conn_info_v2.Length = size;
+			conn_info_v2.SupportedUsbProtocols.Usb300 = 1;
+			if (!DeviceIoControl(handle, IOCTL_USB_GET_NODE_CONNECTION_INFORMATION_EX_V2,
+				&conn_info_v2, size, &conn_info_v2, size, &size, NULL)) {
+				usbi_warn(ctx, "could not get node connection information (V2) for device '%s': %s",
+					device_id,  windows_error_str(0));
+			} else if (conn_info_v2.Flags.DeviceIsOperatingAtSuperSpeedOrHigher) {
+				conn_info.Speed = 3;
+			}
+		}
+
+		CloseHandle(handle);
+
+		if (conn_info.DeviceAddress > UINT8_MAX)
+			usbi_err(ctx, "program assertion failed: device address overflow");
+
+		dev->device_address = (uint8_t)conn_info.DeviceAddress + 1;
+		if (dev->device_address == 1)
+			usbi_err(ctx, "program assertion failed: device address collision with root hub");
+
+		switch (conn_info.Speed) {
+		case 0: dev->speed = LIBUSB_SPEED_LOW; break;
+		case 1: dev->speed = LIBUSB_SPEED_FULL; break;
+		case 2: dev->speed = LIBUSB_SPEED_HIGH; break;
+		case 3: dev->speed = LIBUSB_SPEED_SUPER; break;
+		default:
+			usbi_warn(ctx, "Got unknown device speed %u", conn_info.Speed);
+			break;
+		}
+	} else {
+		dev->device_address = 1; // root hubs are set to use device number 1
+		force_hcd_device_descriptor(dev);
+	}
+
+	usbi_sanitize_device(dev);
+
+	usbi_dbg("(bus: %u, addr: %u, depth: %u, port: %u): '%s'",
+		dev->bus_number, dev->device_address, priv->depth, priv->port, device_id);
+
+	return LIBUSB_SUCCESS;
+}
+
+// Returns the api type, or 0 if not found/unsupported
+static void get_api_type(struct libusb_context *ctx, HDEVINFO *dev_info,
+	SP_DEVINFO_DATA *dev_info_data, int *api, int *sub_api)
+{
+	// Precedence for filter drivers vs driver is in the order of this array
+	struct driver_lookup lookup[3] = {
+		{"\0\0", SPDRP_SERVICE, "driver"},
+		{"\0\0", SPDRP_UPPERFILTERS, "upper filter driver"},
+		{"\0\0", SPDRP_LOWERFILTERS, "lower filter driver"}
+	};
+	DWORD size, reg_type;
+	unsigned k, l;
+	int i, j;
+
+	*api = USB_API_UNSUPPORTED;
+	*sub_api = SUB_API_NOTSET;
+
+	// Check the service & filter names to know the API we should use
+	for (k = 0; k < 3; k++) {
+		if (pSetupDiGetDeviceRegistryPropertyA(*dev_info, dev_info_data, lookup[k].reg_prop,
+			&reg_type, (BYTE *)lookup[k].list, MAX_KEY_LENGTH, &size)) {
+			// Turn the REG_SZ SPDRP_SERVICE into REG_MULTI_SZ
+			if (lookup[k].reg_prop == SPDRP_SERVICE)
+				// our buffers are MAX_KEY_LENGTH + 1 so we can overflow if needed
+				lookup[k].list[strlen(lookup[k].list) + 1] = 0;
+
+			// MULTI_SZ is a pain to work with. Turn it into something much more manageable
+			// NB: none of the driver names we check against contain LIST_SEPARATOR,
+			// (currently ';'), so even if an unsuported one does, it's not an issue
+			for (l = 0; (lookup[k].list[l] != 0) || (lookup[k].list[l + 1] != 0); l++) {
+				if (lookup[k].list[l] == 0)
+					lookup[k].list[l] = LIST_SEPARATOR;
+			}
+			usbi_dbg("%s(s): %s", lookup[k].designation, lookup[k].list);
+		} else {
+			if (GetLastError() != ERROR_INVALID_DATA)
+				usbi_dbg("could not access %s: %s", lookup[k].designation, windows_error_str(0));
+			lookup[k].list[0] = 0;
+		}
+	}
+
+	for (i = 1; i < USB_API_MAX; i++) {
+		for (k = 0; k < 3; k++) {
+			j = get_sub_api(lookup[k].list, i);
+			if (j >= 0) {
+				usbi_dbg("matched %s name against %s", lookup[k].designation,
+					(i != USB_API_WINUSBX) ? usb_api_backend[i].designation : sub_api_name[j]);
+				*api = i;
+				*sub_api = j;
+				return;
+			}
+		}
+	}
+}
+
+static int set_composite_interface(struct libusb_context *ctx, struct libusb_device *dev,
+	char *dev_interface_path, char *device_id, int api, int sub_api)
+{
+	unsigned i;
+	struct windows_device_priv *priv = _device_priv(dev);
+	int interface_number;
+
+	if (priv->apib->id != USB_API_COMPOSITE) {
+		usbi_err(ctx, "program assertion failed: '%s' is not composite", device_id);
+		return LIBUSB_ERROR_NO_DEVICE;
+	}
+
+	// Because MI_## are not necessarily in sequential order (some composite
+	// devices will have only MI_00 & MI_03 for instance), we retrieve the actual
+	// interface number from the path's MI value
+	interface_number = 0;
+	for (i = 0; device_id[i] != 0; ) {
+		if ((device_id[i++] == 'M') && (device_id[i++] == 'I')
+				&& (device_id[i++] == '_')) {
+			interface_number = (device_id[i++] - '0') * 10;
+			interface_number += device_id[i] - '0';
+			break;
+		}
+	}
+
+	if (device_id[i] == 0)
+		usbi_warn(ctx, "failure to read interface number for %s. Using default value %d",
+			device_id, interface_number);
+
+	if (priv->usb_interface[interface_number].path != NULL) {
+		if (api == USB_API_HID) {
+			// HID devices can have multiple collections (COL##) for each MI_## interface
+			usbi_dbg("interface[%d] already set - ignoring HID collection: %s",
+				interface_number, device_id);
+			return LIBUSB_ERROR_ACCESS;
+		}
+		// In other cases, just use the latest data
+		safe_free(priv->usb_interface[interface_number].path);
+	}
+
+	usbi_dbg("interface[%d] = %s", interface_number, dev_interface_path);
+	priv->usb_interface[interface_number].path = dev_interface_path;
+	priv->usb_interface[interface_number].apib = &usb_api_backend[api];
+	priv->usb_interface[interface_number].sub_api = sub_api;
+	if ((api == USB_API_HID) && (priv->hid == NULL)) {
+		priv->hid = calloc(1, sizeof(struct hid_device_priv));
+		if (priv->hid == NULL)
+			return LIBUSB_ERROR_NO_MEM;
+	}
+
+	return LIBUSB_SUCCESS;
+}
+
+static int set_hid_interface(struct libusb_context *ctx, struct libusb_device *dev,
+	char *dev_interface_path)
+{
+	int i;
+	struct windows_device_priv *priv = _device_priv(dev);
+
+	if (priv->hid == NULL) {
+		usbi_err(ctx, "program assertion failed: parent is not HID");
+		return LIBUSB_ERROR_NO_DEVICE;
+	} else if (priv->hid->nb_interfaces == USB_MAXINTERFACES) {
+		usbi_err(ctx, "program assertion failed: max USB interfaces reached for HID device");
+		return LIBUSB_ERROR_NO_DEVICE;
+	}
+
+	for (i = 0; i < priv->hid->nb_interfaces; i++) {
+		if ((priv->usb_interface[i].path != NULL) && strcmp(priv->usb_interface[i].path, dev_interface_path) == 0) {
+			usbi_dbg("interface[%d] already set to %s", i, dev_interface_path);
+			return LIBUSB_ERROR_ACCESS;
+		}
+	}
+
+	priv->usb_interface[priv->hid->nb_interfaces].path = dev_interface_path;
+	priv->usb_interface[priv->hid->nb_interfaces].apib = &usb_api_backend[USB_API_HID];
+	usbi_dbg("interface[%u] = %s", priv->hid->nb_interfaces, dev_interface_path);
+	priv->hid->nb_interfaces++;
+	return LIBUSB_SUCCESS;
+}
+
+/*
+ * get_device_list: libusb backend device enumeration function
+ */
+static int windows_get_device_list(struct libusb_context *ctx, struct discovered_devs **_discdevs)
+{
+	struct discovered_devs *discdevs;
+	HDEVINFO dev_info = { 0 };
+	const char *usb_class[] = {"USB", "NUSB3", "IUSB3", "IARUSB3"};
+	SP_DEVINFO_DATA dev_info_data = { 0 };
+	SP_DEVICE_INTERFACE_DETAIL_DATA_A *dev_interface_details = NULL;
+	GUID hid_guid;
+#define MAX_ENUM_GUIDS 64
+	const GUID *guid[MAX_ENUM_GUIDS];
+#define HCD_PASS 0
+#define HUB_PASS 1
+#define GEN_PASS 2
+#define DEV_PASS 3
+#define HID_PASS 4
+	int r = LIBUSB_SUCCESS;
+	int api, sub_api;
+	size_t class_index = 0;
+	unsigned int nb_guids, pass, i, j, ancestor;
+	char path[MAX_PATH_LENGTH];
+	char strbuf[MAX_PATH_LENGTH];
+	struct libusb_device *dev, *parent_dev;
+	struct windows_device_priv *priv, *parent_priv;
+	char *dev_interface_path = NULL;
+	char *dev_id_path = NULL;
+	unsigned long session_id;
+	DWORD size, reg_type, port_nr, install_state;
+	HKEY key;
+	WCHAR guid_string_w[MAX_GUID_STRING_LENGTH];
+	GUID *if_guid;
+	LONG s;
+	// Keep a list of newly allocated devs to unref
+	libusb_device **unref_list, **new_unref_list;
+	unsigned int unref_size = 64;
+	unsigned int unref_cur = 0;
+
+	// PASS 1 : (re)enumerate HCDs (allows for HCD hotplug)
+	// PASS 2 : (re)enumerate HUBS
+	// PASS 3 : (re)enumerate generic USB devices (including driverless)
+	//           and list additional USB device interface GUIDs to explore
+	// PASS 4 : (re)enumerate master USB devices that have a device interface
+	// PASS 5+: (re)enumerate device interfaced GUIDs (including HID) and
+	//           set the device interfaces.
+
+	// Init the GUID table
+	guid[HCD_PASS] = &GUID_DEVINTERFACE_USB_HOST_CONTROLLER;
+	guid[HUB_PASS] = &GUID_DEVINTERFACE_USB_HUB;
+	guid[GEN_PASS] = NULL;
+	guid[DEV_PASS] = &GUID_DEVINTERFACE_USB_DEVICE;
+	HidD_GetHidGuid(&hid_guid);
+	guid[HID_PASS] = &hid_guid;
+	nb_guids = HID_PASS + 1;
+
+	unref_list = calloc(unref_size, sizeof(libusb_device *));
+	if (unref_list == NULL)
+		return LIBUSB_ERROR_NO_MEM;
+
+	for (pass = 0; ((pass < nb_guids) && (r == LIBUSB_SUCCESS)); pass++) {
+//#define ENUM_DEBUG
+#if defined(ENABLE_LOGGING) && defined(ENUM_DEBUG)
+		const char *passname[] = { "HCD", "HUB", "GEN", "DEV", "HID", "EXT" };
+		usbi_dbg("#### PROCESSING %ss %s", passname[(pass <= HID_PASS) ? pass : (HID_PASS + 1)],
+			(pass != GEN_PASS) ? guid_to_string(guid[pass]) : "");
+#endif
+		for (i = 0; ; i++) {
+			// safe loop: free up any (unprotected) dynamic resource
+			// NB: this is always executed before breaking the loop
+			safe_free(dev_interface_details);
+			safe_free(dev_interface_path);
+			safe_free(dev_id_path);
+			priv = parent_priv = NULL;
+			dev = parent_dev = NULL;
+
+			// Safe loop: end of loop conditions
+			if (r != LIBUSB_SUCCESS)
+				break;
+
+			if ((pass == HCD_PASS) && (i == UINT8_MAX)) {
+				usbi_warn(ctx, "program assertion failed - found more than %d buses, skipping the rest.", UINT8_MAX);
+				break;
+			}
+
+			if (pass != GEN_PASS) {
+				// Except for GEN, all passes deal with device interfaces
+				dev_interface_details = get_interface_details(ctx, &dev_info, &dev_info_data, guid[pass], i);
+				if (dev_interface_details == NULL)
+					break;
+
+				dev_interface_path = sanitize_path(dev_interface_details->DevicePath);
+				if (dev_interface_path == NULL) {
+					usbi_warn(ctx, "could not sanitize device interface path for '%s'", dev_interface_details->DevicePath);
+					continue;
+				}
+			} else {
+				// Workaround for a Nec/Renesas USB 3.0 driver bug where root hubs are
+				// being listed under the "NUSB3" PnP Symbolic Name rather than "USB".
+				// The Intel USB 3.0 driver behaves similar, but uses "IUSB3"
+				// The Intel Alpine Ridge USB 3.1 driver uses "IARUSB3"
+				for (; class_index < ARRAYSIZE(usb_class); class_index++) {
+					if (get_devinfo_data(ctx, &dev_info, &dev_info_data, usb_class[class_index], i))
+						break;
+					i = 0;
+				}
+				if (class_index >= ARRAYSIZE(usb_class))
+					break;
+			}
+
+			// Read the Device ID path. This is what we'll use as UID
+			// Note that if the device is plugged in a different port or hub, the Device ID changes
+			if (CM_Get_Device_IDA(dev_info_data.DevInst, path, sizeof(path), 0) != CR_SUCCESS) {
+				usbi_warn(ctx, "could not read the device id path for devinst %X, skipping",
+					(unsigned int)dev_info_data.DevInst);
+				continue;
+			}
+
+			dev_id_path = sanitize_path(path);
+			if (dev_id_path == NULL) {
+				usbi_warn(ctx, "could not sanitize device id path for devinst %X, skipping",
+					(unsigned int)dev_info_data.DevInst);
+				continue;
+			}
+#ifdef ENUM_DEBUG
+			usbi_dbg("PRO: %s", dev_id_path);
+#endif
+
+			// The SPDRP_ADDRESS for USB devices is the device port number on the hub
+			port_nr = 0;
+			if ((pass >= HUB_PASS) && (pass <= GEN_PASS)) {
+				if ((!pSetupDiGetDeviceRegistryPropertyA(dev_info, &dev_info_data, SPDRP_ADDRESS,
+					&reg_type, (BYTE *)&port_nr, 4, &size)) || (size != 4)) {
+					usbi_warn(ctx, "could not retrieve port number for device '%s', skipping: %s",
+						dev_id_path, windows_error_str(0));
+					continue;
+				}
+			}
+
+			// Set API to use or get additional data from generic pass
+			api = USB_API_UNSUPPORTED;
+			sub_api = SUB_API_NOTSET;
+			switch (pass) {
+			case HCD_PASS:
+				break;
+			case GEN_PASS:
+				// We use the GEN pass to detect driverless devices...
+				size = sizeof(strbuf);
+				if (!pSetupDiGetDeviceRegistryPropertyA(dev_info, &dev_info_data, SPDRP_DRIVER,
+					&reg_type, (BYTE *)strbuf, size, &size)) {
+						usbi_info(ctx, "The following device has no driver: '%s'", dev_id_path);
+						usbi_info(ctx, "libusb will not be able to access it.");
+				}
+				// ...and to add the additional device interface GUIDs
+				key = pSetupDiOpenDevRegKey(dev_info, &dev_info_data, DICS_FLAG_GLOBAL, 0, DIREG_DEV, KEY_READ);
+				if (key != INVALID_HANDLE_VALUE) {
+					size = sizeof(guid_string_w);
+					s = pRegQueryValueExW(key, L"DeviceInterfaceGUIDs", NULL, &reg_type,
+						(BYTE *)guid_string_w, &size);
+					pRegCloseKey(key);
+					if (s == ERROR_SUCCESS) {
+						if (nb_guids >= MAX_ENUM_GUIDS) {
+							// If this assert is ever reported, grow a GUID table dynamically
+							usbi_err(ctx, "program assertion failed: too many GUIDs");
+							LOOP_BREAK(LIBUSB_ERROR_OVERFLOW);
+						}
+						if_guid = calloc(1, sizeof(GUID));
+						if (if_guid == NULL) {
+							usbi_err(ctx, "could not calloc for if_guid: not enough memory");
+							LOOP_BREAK(LIBUSB_ERROR_NO_MEM);
+						}
+						pCLSIDFromString(guid_string_w, if_guid);
+						guid[nb_guids++] = if_guid;
+						usbi_dbg("extra GUID: %s", guid_to_string(if_guid));
+					}
+				}
+				break;
+			case HID_PASS:
+				api = USB_API_HID;
+				break;
+			default:
+				// Get the API type (after checking that the driver installation is OK)
+				if ((!pSetupDiGetDeviceRegistryPropertyA(dev_info, &dev_info_data, SPDRP_INSTALL_STATE,
+					&reg_type, (BYTE *)&install_state, 4, &size)) || (size != 4)) {
+					usbi_warn(ctx, "could not detect installation state of driver for '%s': %s",
+						dev_id_path, windows_error_str(0));
+				} else if (install_state != 0) {
+					usbi_warn(ctx, "driver for device '%s' is reporting an issue (code: %u) - skipping",
+						dev_id_path, (unsigned int)install_state);
+					continue;
+				}
+				get_api_type(ctx, &dev_info, &dev_info_data, &api, &sub_api);
+				break;
+			}
+
+			// Find parent device (for the passes that need it)
+			switch (pass) {
+			case HCD_PASS:
+			case DEV_PASS:
+			case HUB_PASS:
+				break;
+			default:
+				// Go through the ancestors until we see a face we recognize
+				parent_dev = NULL;
+				for (ancestor = 1; parent_dev == NULL; ancestor++) {
+					session_id = get_ancestor_session_id(dev_info_data.DevInst, ancestor);
+					if (session_id == 0)
+						break;
+
+					parent_dev = usbi_get_device_by_session_id(ctx, session_id);
+				}
+
+				if (parent_dev == NULL) {
+					usbi_dbg("unlisted ancestor for '%s' (non USB HID, newly connected, etc.) - ignoring", dev_id_path);
+					continue;
+				}
+
+				parent_priv = _device_priv(parent_dev);
+				// virtual USB devices are also listed during GEN - don't process these yet
+				if ((pass == GEN_PASS) && (parent_priv->apib->id != USB_API_HUB)) {
+					libusb_unref_device(parent_dev);
+					continue;
+				}
+
+				break;
+			}
+
+			// Create new or match existing device, using the (hashed) device_id as session id
+			if (pass <= DEV_PASS) {	// For subsequent passes, we'll lookup the parent
+				// These are the passes that create "new" devices
+				session_id = htab_hash(dev_id_path);
+				dev = usbi_get_device_by_session_id(ctx, session_id);
+				if (dev == NULL) {
+					if (pass == DEV_PASS) {
+						// This can occur if the OS only reports a newly plugged device after we started enum
+						usbi_warn(ctx, "'%s' was only detected in late pass (newly connected device?)"
+							" - ignoring", dev_id_path);
+						continue;
+					}
+
+					usbi_dbg("allocating new device for session [%lX]", session_id);
+					dev = usbi_alloc_device(ctx, session_id);
+					if (dev == NULL)
+						LOOP_BREAK(LIBUSB_ERROR_NO_MEM);
+
+					priv = windows_device_priv_init(dev);
+				} else {
+					usbi_dbg("found existing device for session [%lX] (%u.%u)",
+						session_id, dev->bus_number, dev->device_address);
+
+					priv = _device_priv(dev);
+					if ((parent_dev != NULL) && (dev->parent_dev != NULL)) {
+						if (dev->parent_dev != parent_dev) {
+							// It is possible for the actual parent device to not have existed at the
+							// time of enumeration, so the currently assigned parent may in fact be a
+							// grandparent.  If the devices differ, we assume the "new" parent device
+							// is in fact closer to the device.
+                                                        usbi_dbg("updating parent device [session %lX -> %lX]",
+                                                                dev->parent_dev->session_data, parent_dev->session_data);
+							libusb_unref_device(dev->parent_dev);
+							dev->parent_dev = parent_dev;
+						} else {
+							// We hold a reference to parent_dev instance, but this device already
+							// has a parent_dev reference (only one per child)
+							libusb_unref_device(parent_dev);
+						}
+					}
+				}
+
+				// Keep track of devices that need unref
+				unref_list[unref_cur++] = dev;
+				if (unref_cur >= unref_size) {
+					unref_size += 64;
+					new_unref_list = usbi_reallocf(unref_list, unref_size * sizeof(libusb_device *));
+					if (new_unref_list == NULL) {
+						usbi_err(ctx, "could not realloc list for unref - aborting.");
+						LOOP_BREAK(LIBUSB_ERROR_NO_MEM);
+					} else {
+						unref_list = new_unref_list;
+					}
+				}
+			}
+
+			// Setup device
+			switch (pass) {
+			case HCD_PASS:
+				// If the hcd has already been setup, don't do it again
+				if (priv->path != NULL)
+					break;
+				dev->bus_number = (uint8_t)(i + 1); // bus 0 is reserved for disconnected
+				dev->device_address = 0;
+				dev->num_configurations = 0;
+				priv->apib = &usb_api_backend[USB_API_HUB];
+				priv->sub_api = SUB_API_NOTSET;
+				priv->depth = UINT8_MAX; // Overflow to 0 for HCD Hubs
+				priv->path = dev_interface_path;
+				dev_interface_path = NULL;
+				break;
+			case HUB_PASS:
+			case DEV_PASS:
+				// If the device has already been setup, don't do it again
+				if (priv->path != NULL)
+					break;
+				// Take care of API initialization
+				priv->path = dev_interface_path;
+				dev_interface_path = NULL;
+				priv->apib = &usb_api_backend[api];
+				priv->sub_api = sub_api;
+				switch(api) {
+				case USB_API_COMPOSITE:
+				case USB_API_HUB:
+					break;
+				case USB_API_HID:
+					priv->hid = calloc(1, sizeof(struct hid_device_priv));
+					if (priv->hid == NULL)
+						LOOP_BREAK(LIBUSB_ERROR_NO_MEM);
+
+					priv->hid->nb_interfaces = 0;
+					break;
+				default:
+					// For other devices, the first interface is the same as the device
+					priv->usb_interface[0].path = _strdup(priv->path);
+					if (priv->usb_interface[0].path == NULL)
+						usbi_warn(ctx, "could not duplicate interface path '%s'", priv->path);
+					// The following is needed if we want API calls to work for both simple
+					// and composite devices.
+					for (j = 0; j < USB_MAXINTERFACES; j++)
+						priv->usb_interface[j].apib = &usb_api_backend[api];
+
+					break;
+				}
+				break;
+			case GEN_PASS:
+				r = init_device(dev, parent_dev, (uint8_t)port_nr, dev_id_path, dev_info_data.DevInst);
+				if (r == LIBUSB_SUCCESS) {
+					// Append device to the list of discovered devices
+					discdevs = discovered_devs_append(*_discdevs, dev);
+					if (!discdevs)
+						LOOP_BREAK(LIBUSB_ERROR_NO_MEM);
+
+					*_discdevs = discdevs;
+				} else if (r == LIBUSB_ERROR_NO_DEVICE) {
+					// This can occur if the device was disconnected but Windows hasn't
+					// refreshed its enumeration yet - in that case, we ignore the device
+					r = LIBUSB_SUCCESS;
+				}
+				break;
+			default: // HID_PASS and later
+				if (parent_priv->apib->id == USB_API_HID || parent_priv->apib->id == USB_API_COMPOSITE) {
+					if (parent_priv->apib->id == USB_API_HID) {
+						usbi_dbg("setting HID interface for [%lX]:", parent_dev->session_data);
+						r = set_hid_interface(ctx, parent_dev, dev_interface_path);
+					} else {
+						usbi_dbg("setting composite interface for [%lX]:", parent_dev->session_data);
+						r = set_composite_interface(ctx, parent_dev, dev_interface_path, dev_id_path, api, sub_api);
+					}
+					switch (r) {
+					case LIBUSB_SUCCESS:
+						dev_interface_path = NULL;
+						break;
+					case LIBUSB_ERROR_ACCESS:
+						// interface has already been set => make sure dev_interface_path is freed then
+						r = LIBUSB_SUCCESS;
+						break;
+					default:
+						LOOP_BREAK(r);
+						break;
+					}
+				}
+				libusb_unref_device(parent_dev);
+				break;
+			}
+		}
+	}
+
+	// Free any additional GUIDs
+	for (pass = HID_PASS + 1; pass < nb_guids; pass++)
+		free((void *)guid[pass]);
+
+	// Unref newly allocated devs
+	for (i = 0; i < unref_cur; i++)
+		libusb_unref_device(unref_list[i]);
+	free(unref_list);
+
+	return r;
+}
+
+/*
+ * exit: libusb backend deinitialization function
+ */
+static void windows_exit(void)
+{
+	int i;
+	HANDLE semaphore;
+	char sem_name[11 + 8 + 1]; // strlen("libusb_init") + (32-bit hex PID) + '\0'
+
+	sprintf(sem_name, "libusb_init%08X", (unsigned int)(GetCurrentProcessId() & 0xFFFFFFFF));
+	semaphore = CreateSemaphoreA(NULL, 1, 1, sem_name);
+	if (semaphore == NULL)
+		return;
+
+	// A successful wait brings our semaphore count to 0 (unsignaled)
+	// => any concurent wait stalls until the semaphore release
+	if (WaitForSingleObject(semaphore, INFINITE) != WAIT_OBJECT_0) {
+		CloseHandle(semaphore);
+		return;
+	}
+
+	// Only works if exits and inits are balanced exactly
+	if (--concurrent_usage < 0) { // Last exit
+		for (i = 0; i < USB_API_MAX; i++)
+			usb_api_backend[i].exit(SUB_API_NOTSET);
+		exit_dlls();
+		exit_polling();
+		windows_common_exit();
+		usbi_mutex_destroy(&autoclaim_lock);
+	}
+
+	ReleaseSemaphore(semaphore, 1, NULL); // increase count back to 1
+	CloseHandle(semaphore);
+}
+
+static int windows_get_device_descriptor(struct libusb_device *dev, unsigned char *buffer, int *host_endian)
+{
+	struct windows_device_priv *priv = _device_priv(dev);
+
+	memcpy(buffer, &priv->dev_descriptor, DEVICE_DESC_LENGTH);
+	*host_endian = 0;
+
+	return LIBUSB_SUCCESS;
+}
+
+static int windows_get_config_descriptor(struct libusb_device *dev, uint8_t config_index, unsigned char *buffer, size_t len, int *host_endian)
+{
+	struct windows_device_priv *priv = _device_priv(dev);
+	PUSB_CONFIGURATION_DESCRIPTOR config_header;
+	size_t size;
+
+	// config index is zero based
+	if (config_index >= dev->num_configurations)
+		return LIBUSB_ERROR_INVALID_PARAM;
+
+	if ((priv->config_descriptor == NULL) || (priv->config_descriptor[config_index] == NULL))
+		return LIBUSB_ERROR_NOT_FOUND;
+
+	config_header = (PUSB_CONFIGURATION_DESCRIPTOR)priv->config_descriptor[config_index];
+
+	size = MIN(config_header->wTotalLength, len);
+	memcpy(buffer, priv->config_descriptor[config_index], size);
+	*host_endian = 0;
+
+	return (int)size;
+}
+
+static int windows_get_config_descriptor_by_value(struct libusb_device *dev, uint8_t bConfigurationValue,
+	unsigned char **buffer, int *host_endian)
+{
+	struct windows_device_priv *priv = _device_priv(dev);
+	PUSB_CONFIGURATION_DESCRIPTOR config_header;
+	uint8_t index;
+
+	*buffer = NULL;
+	*host_endian = 0;
+
+	if (priv->config_descriptor == NULL)
+		return LIBUSB_ERROR_NOT_FOUND;
+
+	for (index = 0; index < dev->num_configurations; index++) {
+		config_header = (PUSB_CONFIGURATION_DESCRIPTOR)priv->config_descriptor[index];
+		if (config_header->bConfigurationValue == bConfigurationValue) {
+			*buffer = priv->config_descriptor[index];
+			return (int)config_header->wTotalLength;
+		}
+	}
+
+	return LIBUSB_ERROR_NOT_FOUND;
+}
+
+/*
+ * return the cached copy of the active config descriptor
+ */
+static int windows_get_active_config_descriptor(struct libusb_device *dev, unsigned char *buffer, size_t len, int *host_endian)
+{
+	struct windows_device_priv *priv = _device_priv(dev);
+	unsigned char *config_desc;
+	int r;
+
+	if (priv->active_config == 0)
+		return LIBUSB_ERROR_NOT_FOUND;
+
+	r = windows_get_config_descriptor_by_value(dev, priv->active_config, &config_desc, host_endian);
+	if (r < 0)
+		return r;
+
+	len = MIN((size_t)r, len);
+	memcpy(buffer, config_desc, len);
+	return (int)len;
+}
+
+static int windows_open(struct libusb_device_handle *dev_handle)
+{
+	struct windows_device_priv *priv = _device_priv(dev_handle->dev);
+	struct libusb_context *ctx = DEVICE_CTX(dev_handle->dev);
+
+	if (priv->apib == NULL) {
+		usbi_err(ctx, "program assertion failed - device is not initialized");
+		return LIBUSB_ERROR_NO_DEVICE;
+	}
+
+	return priv->apib->open(SUB_API_NOTSET, dev_handle);
+}
+
+static void windows_close(struct libusb_device_handle *dev_handle)
+{
+	struct windows_device_priv *priv = _device_priv(dev_handle->dev);
+
+	priv->apib->close(SUB_API_NOTSET, dev_handle);
+}
+
+static int windows_get_configuration(struct libusb_device_handle *dev_handle, int *config)
+{
+	struct windows_device_priv *priv = _device_priv(dev_handle->dev);
+
+	if (priv->active_config == 0) {
+		*config = 0;
+		return LIBUSB_ERROR_NOT_FOUND;
+	}
+
+	*config = priv->active_config;
+	return LIBUSB_SUCCESS;
+}
+
+/*
+ * from http://msdn.microsoft.com/en-us/library/ms793522.aspx: "The port driver
+ * does not currently expose a service that allows higher-level drivers to set
+ * the configuration."
+ */
+static int windows_set_configuration(struct libusb_device_handle *dev_handle, int config)
+{
+	struct windows_device_priv *priv = _device_priv(dev_handle->dev);
+	int r = LIBUSB_SUCCESS;
+
+	if (config >= USB_MAXCONFIG)
+		return LIBUSB_ERROR_INVALID_PARAM;
+
+	r = libusb_control_transfer(dev_handle, LIBUSB_ENDPOINT_OUT |
+		LIBUSB_REQUEST_TYPE_STANDARD | LIBUSB_RECIPIENT_DEVICE,
+		LIBUSB_REQUEST_SET_CONFIGURATION, (uint16_t)config,
+		0, NULL, 0, 1000);
+
+	if (r == LIBUSB_SUCCESS)
+		priv->active_config = (uint8_t)config;
+
+	return r;
+}
+
+static int windows_claim_interface(struct libusb_device_handle *dev_handle, int iface)
+{
+	int r = LIBUSB_SUCCESS;
+	struct windows_device_priv *priv = _device_priv(dev_handle->dev);
+
+	safe_free(priv->usb_interface[iface].endpoint);
+	priv->usb_interface[iface].nb_endpoints = 0;
+
+	r = priv->apib->claim_interface(SUB_API_NOTSET, dev_handle, iface);
+
+	if (r == LIBUSB_SUCCESS)
+		r = windows_assign_endpoints(dev_handle, iface, 0);
+
+	return r;
+}
+
+static int windows_set_interface_altsetting(struct libusb_device_handle *dev_handle, int iface, int altsetting)
+{
+	int r = LIBUSB_SUCCESS;
+	struct windows_device_priv *priv = _device_priv(dev_handle->dev);
+
+	safe_free(priv->usb_interface[iface].endpoint);
+	priv->usb_interface[iface].nb_endpoints = 0;
+
+	r = priv->apib->set_interface_altsetting(SUB_API_NOTSET, dev_handle, iface, altsetting);
+
+	if (r == LIBUSB_SUCCESS)
+		r = windows_assign_endpoints(dev_handle, iface, altsetting);
+
+	return r;
+}
+
+static int windows_release_interface(struct libusb_device_handle *dev_handle, int iface)
+{
+	struct windows_device_priv *priv = _device_priv(dev_handle->dev);
+
+	return priv->apib->release_interface(SUB_API_NOTSET, dev_handle, iface);
+}
+
+static int windows_clear_halt(struct libusb_device_handle *dev_handle, unsigned char endpoint)
+{
+	struct windows_device_priv *priv = _device_priv(dev_handle->dev);
+	return priv->apib->clear_halt(SUB_API_NOTSET, dev_handle, endpoint);
+}
+
+static int windows_reset_device(struct libusb_device_handle *dev_handle)
+{
+	struct windows_device_priv *priv = _device_priv(dev_handle->dev);
+	return priv->apib->reset_device(SUB_API_NOTSET, dev_handle);
+}
+
+// The 3 functions below are unlikely to ever get supported on Windows
+static int windows_kernel_driver_active(struct libusb_device_handle *dev_handle, int iface)
+{
+	return LIBUSB_ERROR_NOT_SUPPORTED;
+}
+
+static int windows_attach_kernel_driver(struct libusb_device_handle *dev_handle, int iface)
+{
+	return LIBUSB_ERROR_NOT_SUPPORTED;
+}
+
+static int windows_detach_kernel_driver(struct libusb_device_handle *dev_handle, int iface)
+{
+	return LIBUSB_ERROR_NOT_SUPPORTED;
+}
+
+static void windows_destroy_device(struct libusb_device *dev)
+{
+	windows_device_priv_release(dev);
+}
+
+void windows_clear_transfer_priv(struct usbi_transfer *itransfer)
+{
+	struct windows_transfer_priv *transfer_priv = usbi_transfer_get_os_priv(itransfer);
+
+	usbi_free_fd(&transfer_priv->pollable_fd);
+	safe_free(transfer_priv->hid_buffer);
+	// When auto claim is in use, attempt to release the auto-claimed interface
+	auto_release(itransfer);
+}
+
+static int submit_bulk_transfer(struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	struct libusb_context *ctx = DEVICE_CTX(transfer->dev_handle->dev);
+	struct windows_transfer_priv *transfer_priv = usbi_transfer_get_os_priv(itransfer);
+	struct windows_device_priv *priv = _device_priv(transfer->dev_handle->dev);
+	int r;
+
+	r = priv->apib->submit_bulk_transfer(SUB_API_NOTSET, itransfer);
+	if (r != LIBUSB_SUCCESS)
+		return r;
+
+	usbi_add_pollfd(ctx, transfer_priv->pollable_fd.fd,
+		(short)(IS_XFERIN(transfer) ? POLLIN : POLLOUT));
+
+	return LIBUSB_SUCCESS;
+}
+
+static int submit_iso_transfer(struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	struct libusb_context *ctx = DEVICE_CTX(transfer->dev_handle->dev);
+	struct windows_transfer_priv *transfer_priv = usbi_transfer_get_os_priv(itransfer);
+	struct windows_device_priv *priv = _device_priv(transfer->dev_handle->dev);
+	int r;
+
+	r = priv->apib->submit_iso_transfer(SUB_API_NOTSET, itransfer);
+	if (r != LIBUSB_SUCCESS)
+		return r;
+
+	usbi_add_pollfd(ctx, transfer_priv->pollable_fd.fd,
+		(short)(IS_XFERIN(transfer) ? POLLIN : POLLOUT));
+
+	return LIBUSB_SUCCESS;
+}
+
+static int submit_control_transfer(struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	struct libusb_context *ctx = DEVICE_CTX(transfer->dev_handle->dev);
+	struct windows_transfer_priv *transfer_priv = usbi_transfer_get_os_priv(itransfer);
+	struct windows_device_priv *priv = _device_priv(transfer->dev_handle->dev);
+	int r;
+
+	r = priv->apib->submit_control_transfer(SUB_API_NOTSET, itransfer);
+	if (r != LIBUSB_SUCCESS)
+		return r;
+
+	usbi_add_pollfd(ctx, transfer_priv->pollable_fd.fd, POLLIN);
+
+	return LIBUSB_SUCCESS;
+}
+
+static int windows_submit_transfer(struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+
+	switch (transfer->type) {
+	case LIBUSB_TRANSFER_TYPE_CONTROL:
+		return submit_control_transfer(itransfer);
+	case LIBUSB_TRANSFER_TYPE_BULK:
+	case LIBUSB_TRANSFER_TYPE_INTERRUPT:
+		if (IS_XFEROUT(transfer) && (transfer->flags & LIBUSB_TRANSFER_ADD_ZERO_PACKET))
+			return LIBUSB_ERROR_NOT_SUPPORTED;
+		return submit_bulk_transfer(itransfer);
+	case LIBUSB_TRANSFER_TYPE_ISOCHRONOUS:
+		return submit_iso_transfer(itransfer);
+	case LIBUSB_TRANSFER_TYPE_BULK_STREAM:
+		return LIBUSB_ERROR_NOT_SUPPORTED;
+	default:
+		usbi_err(TRANSFER_CTX(transfer), "unknown endpoint type %d", transfer->type);
+		return LIBUSB_ERROR_INVALID_PARAM;
+	}
+}
+
+static int windows_abort_control(struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	struct windows_device_priv *priv = _device_priv(transfer->dev_handle->dev);
+
+	return priv->apib->abort_control(SUB_API_NOTSET, itransfer);
+}
+
+static int windows_abort_transfers(struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	struct windows_device_priv *priv = _device_priv(transfer->dev_handle->dev);
+
+	return priv->apib->abort_transfers(SUB_API_NOTSET, itransfer);
+}
+
+static int windows_cancel_transfer(struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+
+	switch (transfer->type) {
+	case LIBUSB_TRANSFER_TYPE_CONTROL:
+		return windows_abort_control(itransfer);
+	case LIBUSB_TRANSFER_TYPE_BULK:
+	case LIBUSB_TRANSFER_TYPE_INTERRUPT:
+	case LIBUSB_TRANSFER_TYPE_ISOCHRONOUS:
+		return windows_abort_transfers(itransfer);
+	case LIBUSB_TRANSFER_TYPE_BULK_STREAM:
+		return LIBUSB_ERROR_NOT_SUPPORTED;
+	default:
+		usbi_err(ITRANSFER_CTX(itransfer), "unknown endpoint type %d", transfer->type);
+		return LIBUSB_ERROR_INVALID_PARAM;
+	}
+}
+
+int windows_copy_transfer_data(struct usbi_transfer *itransfer, uint32_t io_size)
+{
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	struct windows_device_priv *priv = _device_priv(transfer->dev_handle->dev);
+	return priv->apib->copy_transfer_data(SUB_API_NOTSET, itransfer, io_size);
+}
+
+struct winfd *windows_get_fd(struct usbi_transfer *transfer)
+{
+	struct windows_transfer_priv *transfer_priv = usbi_transfer_get_os_priv(transfer);
+	return &transfer_priv->pollable_fd;
+}
+
+void windows_get_overlapped_result(struct usbi_transfer *transfer, struct winfd *pollable_fd, DWORD *io_result, DWORD *io_size)
+{
+	if (HasOverlappedIoCompletedSync(pollable_fd->overlapped)) {
+		*io_result = NO_ERROR;
+		*io_size = (DWORD)pollable_fd->overlapped->InternalHigh;
+	} else if (GetOverlappedResult(pollable_fd->handle, pollable_fd->overlapped, io_size, false)) {
+		// Regular async overlapped
+		*io_result = NO_ERROR;
+	} else {
+		*io_result = GetLastError();
+	}
+}
+
+// NB: MSVC6 does not support named initializers.
+const struct usbi_os_backend windows_backend = {
+	"Windows",
+	USBI_CAP_HAS_HID_ACCESS,
+	windows_init,
+	windows_exit,
+
+	windows_get_device_list,
+	NULL,				/* hotplug_poll */
+	windows_open,
+	windows_close,
+
+	windows_get_device_descriptor,
+	windows_get_active_config_descriptor,
+	windows_get_config_descriptor,
+	windows_get_config_descriptor_by_value,
+
+	windows_get_configuration,
+	windows_set_configuration,
+	windows_claim_interface,
+	windows_release_interface,
+
+	windows_set_interface_altsetting,
+	windows_clear_halt,
+	windows_reset_device,
+
+	NULL,				/* alloc_streams */
+	NULL,				/* free_streams */
+
+	NULL,				/* dev_mem_alloc */
+	NULL,				/* dev_mem_free */
+
+	windows_kernel_driver_active,
+	windows_detach_kernel_driver,
+	windows_attach_kernel_driver,
+
+	windows_destroy_device,
+
+	windows_submit_transfer,
+	windows_cancel_transfer,
+	windows_clear_transfer_priv,
+
+	windows_handle_events,
+	NULL,
+
+	windows_clock_gettime,
+#if defined(USBI_TIMERFD_AVAILABLE)
+	NULL,
+#endif
+	sizeof(struct windows_device_priv),
+	sizeof(struct windows_device_handle_priv),
+	sizeof(struct windows_transfer_priv),
+};
+
+
+/*
+ * USB API backends
+ */
+static int unsupported_init(int sub_api, struct libusb_context *ctx)
+{
+	return LIBUSB_SUCCESS;
+}
+
+static int unsupported_exit(int sub_api)
+{
+	return LIBUSB_SUCCESS;
+}
+
+static int unsupported_open(int sub_api, struct libusb_device_handle *dev_handle)
+{
+	PRINT_UNSUPPORTED_API(open);
+}
+
+static void unsupported_close(int sub_api, struct libusb_device_handle *dev_handle)
+{
+	usbi_dbg("unsupported API call for 'close'");
+}
+
+static int unsupported_configure_endpoints(int sub_api, struct libusb_device_handle *dev_handle, int iface)
+{
+	PRINT_UNSUPPORTED_API(configure_endpoints);
+}
+
+static int unsupported_claim_interface(int sub_api, struct libusb_device_handle *dev_handle, int iface)
+{
+	PRINT_UNSUPPORTED_API(claim_interface);
+}
+
+static int unsupported_set_interface_altsetting(int sub_api, struct libusb_device_handle *dev_handle, int iface, int altsetting)
+{
+	PRINT_UNSUPPORTED_API(set_interface_altsetting);
+}
+
+static int unsupported_release_interface(int sub_api, struct libusb_device_handle *dev_handle, int iface)
+{
+	PRINT_UNSUPPORTED_API(release_interface);
+}
+
+static int unsupported_clear_halt(int sub_api, struct libusb_device_handle *dev_handle, unsigned char endpoint)
+{
+	PRINT_UNSUPPORTED_API(clear_halt);
+}
+
+static int unsupported_reset_device(int sub_api, struct libusb_device_handle *dev_handle)
+{
+	PRINT_UNSUPPORTED_API(reset_device);
+}
+
+static int unsupported_submit_bulk_transfer(int sub_api, struct usbi_transfer *itransfer)
+{
+	PRINT_UNSUPPORTED_API(submit_bulk_transfer);
+}
+
+static int unsupported_submit_iso_transfer(int sub_api, struct usbi_transfer *itransfer)
+{
+	PRINT_UNSUPPORTED_API(submit_iso_transfer);
+}
+
+static int unsupported_submit_control_transfer(int sub_api, struct usbi_transfer *itransfer)
+{
+	PRINT_UNSUPPORTED_API(submit_control_transfer);
+}
+
+static int unsupported_abort_control(int sub_api, struct usbi_transfer *itransfer)
+{
+	PRINT_UNSUPPORTED_API(abort_control);
+}
+
+static int unsupported_abort_transfers(int sub_api, struct usbi_transfer *itransfer)
+{
+	PRINT_UNSUPPORTED_API(abort_transfers);
+}
+
+static int unsupported_copy_transfer_data(int sub_api, struct usbi_transfer *itransfer, uint32_t io_size)
+{
+	PRINT_UNSUPPORTED_API(copy_transfer_data);
+}
+
+static int common_configure_endpoints(int sub_api, struct libusb_device_handle *dev_handle, int iface)
+{
+	return LIBUSB_SUCCESS;
+}
+
+// These names must be uppercase
+static const char *hub_driver_names[] = {"USBHUB", "USBHUB3", "USB3HUB", "NUSB3HUB", "RUSB3HUB", "FLXHCIH", "TIHUB3", "ETRONHUB3", "VIAHUB3", "ASMTHUB3", "IUSB3HUB", "VUSB3HUB", "AMDHUB30", "VHHUB", "AUSB3HUB"};
+static const char *composite_driver_names[] = {"USBCCGP"};
+static const char *winusbx_driver_names[] = WINUSBX_DRV_NAMES;
+static const char *hid_driver_names[] = {"HIDUSB", "MOUHID", "KBDHID"};
+const struct windows_usb_api_backend usb_api_backend[USB_API_MAX] = {
+	{
+		USB_API_UNSUPPORTED,
+		"Unsupported API",
+		NULL,
+		0,
+		unsupported_init,
+		unsupported_exit,
+		unsupported_open,
+		unsupported_close,
+		unsupported_configure_endpoints,
+		unsupported_claim_interface,
+		unsupported_set_interface_altsetting,
+		unsupported_release_interface,
+		unsupported_clear_halt,
+		unsupported_reset_device,
+		unsupported_submit_bulk_transfer,
+		unsupported_submit_iso_transfer,
+		unsupported_submit_control_transfer,
+		unsupported_abort_control,
+		unsupported_abort_transfers,
+		unsupported_copy_transfer_data,
+	},
+	{
+		USB_API_HUB,
+		"HUB API",
+		hub_driver_names,
+		ARRAYSIZE(hub_driver_names),
+		unsupported_init,
+		unsupported_exit,
+		unsupported_open,
+		unsupported_close,
+		unsupported_configure_endpoints,
+		unsupported_claim_interface,
+		unsupported_set_interface_altsetting,
+		unsupported_release_interface,
+		unsupported_clear_halt,
+		unsupported_reset_device,
+		unsupported_submit_bulk_transfer,
+		unsupported_submit_iso_transfer,
+		unsupported_submit_control_transfer,
+		unsupported_abort_control,
+		unsupported_abort_transfers,
+		unsupported_copy_transfer_data,
+	},
+	{
+		USB_API_COMPOSITE,
+		"Composite API",
+		composite_driver_names,
+		ARRAYSIZE(composite_driver_names),
+		composite_init,
+		composite_exit,
+		composite_open,
+		composite_close,
+		common_configure_endpoints,
+		composite_claim_interface,
+		composite_set_interface_altsetting,
+		composite_release_interface,
+		composite_clear_halt,
+		composite_reset_device,
+		composite_submit_bulk_transfer,
+		composite_submit_iso_transfer,
+		composite_submit_control_transfer,
+		composite_abort_control,
+		composite_abort_transfers,
+		composite_copy_transfer_data,
+	},
+	{
+		USB_API_WINUSBX,
+		"WinUSB-like APIs",
+		winusbx_driver_names,
+		ARRAYSIZE(winusbx_driver_names),
+		winusbx_init,
+		winusbx_exit,
+		winusbx_open,
+		winusbx_close,
+		winusbx_configure_endpoints,
+		winusbx_claim_interface,
+		winusbx_set_interface_altsetting,
+		winusbx_release_interface,
+		winusbx_clear_halt,
+		winusbx_reset_device,
+		winusbx_submit_bulk_transfer,
+		unsupported_submit_iso_transfer,
+		winusbx_submit_control_transfer,
+		winusbx_abort_control,
+		winusbx_abort_transfers,
+		winusbx_copy_transfer_data,
+	},
+	{
+		USB_API_HID,
+		"HID API",
+		hid_driver_names,
+		ARRAYSIZE(hid_driver_names),
+		hid_init,
+		hid_exit,
+		hid_open,
+		hid_close,
+		common_configure_endpoints,
+		hid_claim_interface,
+		hid_set_interface_altsetting,
+		hid_release_interface,
+		hid_clear_halt,
+		hid_reset_device,
+		hid_submit_bulk_transfer,
+		unsupported_submit_iso_transfer,
+		hid_submit_control_transfer,
+		hid_abort_transfers,
+		hid_abort_transfers,
+		hid_copy_transfer_data,
+	},
+};
+
+
+/*
+ * WinUSB-like (WinUSB, libusb0/libusbK through libusbk DLL) API functions
+ */
+#define WinUSBX_Set(fn)										\
+	do {											\
+		if (native_winusb)								\
+			WinUSBX[i].fn = (WinUsb_##fn##_t)GetProcAddress(h, "WinUsb_" #fn);	\
+		else										\
+			pLibK_GetProcAddress((PVOID *)&WinUSBX[i].fn, i, KUSB_FNID_##fn);	\
+	} while (0)
+
+static int winusbx_init(int sub_api, struct libusb_context *ctx)
+{
+	HMODULE h;
+	bool native_winusb;
+	int i;
+	KLIB_VERSION LibK_Version;
+	LibK_GetProcAddress_t pLibK_GetProcAddress = NULL;
+	LibK_GetVersion_t pLibK_GetVersion;
+
+	h = LoadLibraryA("libusbK");
+
+	if (h == NULL) {
+		usbi_info(ctx, "libusbK DLL is not available, will use native WinUSB");
+		h = LoadLibraryA("WinUSB");
+
+		if (h == NULL) {
+			usbi_warn(ctx, "WinUSB DLL is not available either, "
+				"you will not be able to access devices outside of enumeration");
+			return LIBUSB_ERROR_NOT_FOUND;
+		}
+	} else {
+		usbi_dbg("using libusbK DLL for universal access");
+		pLibK_GetVersion = (LibK_GetVersion_t)GetProcAddress(h, "LibK_GetVersion");
+		if (pLibK_GetVersion != NULL) {
+			pLibK_GetVersion(&LibK_Version);
+			usbi_dbg("libusbK version: %d.%d.%d.%d", LibK_Version.Major, LibK_Version.Minor,
+				LibK_Version.Micro, LibK_Version.Nano);
+		}
+		pLibK_GetProcAddress = (LibK_GetProcAddress_t)GetProcAddress(h, "LibK_GetProcAddress");
+		if (pLibK_GetProcAddress == NULL) {
+			usbi_err(ctx, "LibK_GetProcAddress() not found in libusbK DLL");
+			FreeLibrary(h);
+			return LIBUSB_ERROR_NOT_FOUND;
+		}
+	}
+
+	native_winusb = (pLibK_GetProcAddress == NULL);
+	for (i = SUB_API_LIBUSBK; i < SUB_API_MAX; i++) {
+		WinUSBX_Set(AbortPipe);
+		WinUSBX_Set(ControlTransfer);
+		WinUSBX_Set(FlushPipe);
+		WinUSBX_Set(Free);
+		WinUSBX_Set(GetAssociatedInterface);
+		WinUSBX_Set(GetCurrentAlternateSetting);
+		WinUSBX_Set(GetDescriptor);
+		WinUSBX_Set(GetOverlappedResult);
+		WinUSBX_Set(GetPipePolicy);
+		WinUSBX_Set(GetPowerPolicy);
+		WinUSBX_Set(Initialize);
+		WinUSBX_Set(QueryDeviceInformation);
+		WinUSBX_Set(QueryInterfaceSettings);
+		WinUSBX_Set(QueryPipe);
+		WinUSBX_Set(ReadPipe);
+		WinUSBX_Set(ResetPipe);
+		WinUSBX_Set(SetCurrentAlternateSetting);
+		WinUSBX_Set(SetPipePolicy);
+		WinUSBX_Set(SetPowerPolicy);
+		WinUSBX_Set(WritePipe);
+		if (!native_winusb)
+			WinUSBX_Set(ResetDevice);
+
+		if (WinUSBX[i].Initialize != NULL) {
+			WinUSBX[i].initialized = true;
+			usbi_dbg("initalized sub API %s", sub_api_name[i]);
+		} else {
+			usbi_warn(ctx, "Failed to initalize sub API %s", sub_api_name[i]);
+			WinUSBX[i].initialized = false;
+		}
+	}
+
+	WinUSBX_handle = h;
+	return LIBUSB_SUCCESS;
+}
+
+static int winusbx_exit(int sub_api)
+{
+	if (WinUSBX_handle != NULL) {
+		FreeLibrary(WinUSBX_handle);
+		WinUSBX_handle = NULL;
+
+		/* Reset the WinUSBX API structures */
+		memset(&WinUSBX, 0, sizeof(WinUSBX));
+	}
+
+	return LIBUSB_SUCCESS;
+}
+
+// NB: open and close must ensure that they only handle interface of
+// the right API type, as these functions can be called wholesale from
+// composite_open(), with interfaces belonging to different APIs
+static int winusbx_open(int sub_api, struct libusb_device_handle *dev_handle)
+{
+	struct libusb_context *ctx = DEVICE_CTX(dev_handle->dev);
+	struct windows_device_priv *priv = _device_priv(dev_handle->dev);
+	struct windows_device_handle_priv *handle_priv = _device_handle_priv(dev_handle);
+
+	HANDLE file_handle;
+	int i;
+
+	CHECK_WINUSBX_AVAILABLE(sub_api);
+
+	// WinUSB requires a separate handle for each interface
+	for (i = 0; i < USB_MAXINTERFACES; i++) {
+		if ((priv->usb_interface[i].path != NULL)
+				&& (priv->usb_interface[i].apib->id == USB_API_WINUSBX)) {
+			file_handle = CreateFileA(priv->usb_interface[i].path, GENERIC_WRITE | GENERIC_READ, FILE_SHARE_WRITE | FILE_SHARE_READ,
+				NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED, NULL);
+			if (file_handle == INVALID_HANDLE_VALUE) {
+				usbi_err(ctx, "could not open device %s (interface %d): %s", priv->usb_interface[i].path, i, windows_error_str(0));
+				switch(GetLastError()) {
+				case ERROR_FILE_NOT_FOUND: // The device was disconnected
+					return LIBUSB_ERROR_NO_DEVICE;
+				case ERROR_ACCESS_DENIED:
+					return LIBUSB_ERROR_ACCESS;
+				default:
+					return LIBUSB_ERROR_IO;
+				}
+			}
+			handle_priv->interface_handle[i].dev_handle = file_handle;
+		}
+	}
+
+	return LIBUSB_SUCCESS;
+}
+
+static void winusbx_close(int sub_api, struct libusb_device_handle *dev_handle)
+{
+	struct windows_device_handle_priv *handle_priv = _device_handle_priv(dev_handle);
+	struct windows_device_priv *priv = _device_priv(dev_handle->dev);
+	HANDLE handle;
+	int i;
+
+	if (sub_api == SUB_API_NOTSET)
+		sub_api = priv->sub_api;
+
+	if (!WinUSBX[sub_api].initialized)
+		return;
+
+	if (priv->apib->id == USB_API_COMPOSITE) {
+		// If this is a composite device, just free and close all WinUSB-like
+		// interfaces directly (each is independent and not associated with another)
+		for (i = 0; i < USB_MAXINTERFACES; i++) {
+			if (priv->usb_interface[i].apib->id == USB_API_WINUSBX) {
+				handle = handle_priv->interface_handle[i].api_handle;
+				if (HANDLE_VALID(handle))
+					WinUSBX[sub_api].Free(handle);
+
+				handle = handle_priv->interface_handle[i].dev_handle;
+				if (HANDLE_VALID(handle))
+					CloseHandle(handle);
+			}
+		}
+	} else {
+		// If this is a WinUSB device, free all interfaces above interface 0,
+		// then free and close interface 0 last
+		for (i = 1; i < USB_MAXINTERFACES; i++) {
+			handle = handle_priv->interface_handle[i].api_handle;
+			if (HANDLE_VALID(handle))
+				WinUSBX[sub_api].Free(handle);
+		}
+		handle = handle_priv->interface_handle[0].api_handle;
+		if (HANDLE_VALID(handle))
+			WinUSBX[sub_api].Free(handle);
+
+		handle = handle_priv->interface_handle[0].dev_handle;
+		if (HANDLE_VALID(handle))
+			CloseHandle(handle);
+	}
+}
+
+static int winusbx_configure_endpoints(int sub_api, struct libusb_device_handle *dev_handle, int iface)
+{
+	struct windows_device_handle_priv *handle_priv = _device_handle_priv(dev_handle);
+	struct windows_device_priv *priv = _device_priv(dev_handle->dev);
+	HANDLE winusb_handle = handle_priv->interface_handle[iface].api_handle;
+	UCHAR policy;
+	ULONG timeout = 0;
+	uint8_t endpoint_address;
+	int i;
+
+	CHECK_WINUSBX_AVAILABLE(sub_api);
+
+	// With handle and enpoints set (in parent), we can setup the default pipe properties
+	// see http://download.microsoft.com/download/D/1/D/D1DD7745-426B-4CC3-A269-ABBBE427C0EF/DVC-T705_DDC08.pptx
+	for (i = -1; i < priv->usb_interface[iface].nb_endpoints; i++) {
+		endpoint_address = (i == -1) ? 0 : priv->usb_interface[iface].endpoint[i];
+		if (!WinUSBX[sub_api].SetPipePolicy(winusb_handle, endpoint_address,
+			PIPE_TRANSFER_TIMEOUT, sizeof(ULONG), &timeout))
+			usbi_dbg("failed to set PIPE_TRANSFER_TIMEOUT for control endpoint %02X", endpoint_address);
+
+		if ((i == -1) || (sub_api == SUB_API_LIBUSB0))
+			continue; // Other policies don't apply to control endpoint or libusb0
+
+		policy = false;
+		if (!WinUSBX[sub_api].SetPipePolicy(winusb_handle, endpoint_address,
+			SHORT_PACKET_TERMINATE, sizeof(UCHAR), &policy))
+			usbi_dbg("failed to disable SHORT_PACKET_TERMINATE for endpoint %02X", endpoint_address);
+
+		if (!WinUSBX[sub_api].SetPipePolicy(winusb_handle, endpoint_address,
+			IGNORE_SHORT_PACKETS, sizeof(UCHAR), &policy))
+			usbi_dbg("failed to disable IGNORE_SHORT_PACKETS for endpoint %02X", endpoint_address);
+
+		policy = true;
+		/* ALLOW_PARTIAL_READS must be enabled due to likely libusbK bug. See:
+		   https://sourceforge.net/mailarchive/message.php?msg_id=29736015 */
+		if (!WinUSBX[sub_api].SetPipePolicy(winusb_handle, endpoint_address,
+			ALLOW_PARTIAL_READS, sizeof(UCHAR), &policy))
+			usbi_dbg("failed to enable ALLOW_PARTIAL_READS for endpoint %02X", endpoint_address);
+
+		if (!WinUSBX[sub_api].SetPipePolicy(winusb_handle, endpoint_address,
+			AUTO_CLEAR_STALL, sizeof(UCHAR), &policy))
+			usbi_dbg("failed to enable AUTO_CLEAR_STALL for endpoint %02X", endpoint_address);
+	}
+
+	return LIBUSB_SUCCESS;
+}
+
+static int winusbx_claim_interface(int sub_api, struct libusb_device_handle *dev_handle, int iface)
+{
+	struct libusb_context *ctx = DEVICE_CTX(dev_handle->dev);
+	struct windows_device_handle_priv *handle_priv = _device_handle_priv(dev_handle);
+	struct windows_device_priv *priv = _device_priv(dev_handle->dev);
+	bool is_using_usbccgp = (priv->apib->id == USB_API_COMPOSITE);
+	SP_DEVICE_INTERFACE_DETAIL_DATA_A *dev_interface_details = NULL;
+	HDEVINFO dev_info = INVALID_HANDLE_VALUE;
+	SP_DEVINFO_DATA dev_info_data;
+	char *dev_path_no_guid = NULL;
+	char filter_path[] = "\\\\.\\libusb0-0000";
+	bool found_filter = false;
+	HANDLE file_handle, winusb_handle;
+	DWORD err;
+	int i;
+
+	CHECK_WINUSBX_AVAILABLE(sub_api);
+
+	// If the device is composite, but using the default Windows composite parent driver (usbccgp)
+	// or if it's the first WinUSB-like interface, we get a handle through Initialize().
+	if ((is_using_usbccgp) || (iface == 0)) {
+		// composite device (independent interfaces) or interface 0
+		file_handle = handle_priv->interface_handle[iface].dev_handle;
+		if (!HANDLE_VALID(file_handle))
+			return LIBUSB_ERROR_NOT_FOUND;
+
+		if (!WinUSBX[sub_api].Initialize(file_handle, &winusb_handle)) {
+			handle_priv->interface_handle[iface].api_handle = INVALID_HANDLE_VALUE;
+			err = GetLastError();
+			switch(err) {
+			case ERROR_BAD_COMMAND:
+				// The device was disconnected
+				usbi_err(ctx, "could not access interface %d: %s", iface, windows_error_str(0));
+				return LIBUSB_ERROR_NO_DEVICE;
+			default:
+				// it may be that we're using the libusb0 filter driver.
+				// TODO: can we move this whole business into the K/0 DLL?
+				for (i = 0; ; i++) {
+					safe_free(dev_interface_details);
+					safe_free(dev_path_no_guid);
+
+					dev_interface_details = get_interface_details_filter(ctx, &dev_info, &dev_info_data, &GUID_DEVINTERFACE_LIBUSB0_FILTER, i, filter_path);
+					if ((found_filter) || (dev_interface_details == NULL))
+						break;
+
+					// ignore GUID part
+					dev_path_no_guid = sanitize_path(strtok(dev_interface_details->DevicePath, "{"));
+					if (dev_path_no_guid == NULL)
+						continue;
+
+					if (strncmp(dev_path_no_guid, priv->usb_interface[iface].path, strlen(dev_path_no_guid)) == 0) {
+						file_handle = CreateFileA(filter_path, GENERIC_WRITE | GENERIC_READ, FILE_SHARE_WRITE | FILE_SHARE_READ,
+							NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED, NULL);
+						if (file_handle != INVALID_HANDLE_VALUE) {
+							if (WinUSBX[sub_api].Initialize(file_handle, &winusb_handle)) {
+								// Replace the existing file handle with the working one
+								CloseHandle(handle_priv->interface_handle[iface].dev_handle);
+								handle_priv->interface_handle[iface].dev_handle = file_handle;
+								found_filter = true;
+							} else {
+								usbi_err(ctx, "could not initialize filter driver for %s", filter_path);
+								CloseHandle(file_handle);
+							}
+						} else {
+							usbi_err(ctx, "could not open device %s: %s", filter_path, windows_error_str(0));
+						}
+					}
+				}
+				free(dev_interface_details);
+				if (!found_filter) {
+					usbi_err(ctx, "could not access interface %d: %s", iface, windows_error_str(err));
+					return LIBUSB_ERROR_ACCESS;
+				}
+			}
+		}
+		handle_priv->interface_handle[iface].api_handle = winusb_handle;
+	} else {
+		// For all other interfaces, use GetAssociatedInterface()
+		winusb_handle = handle_priv->interface_handle[0].api_handle;
+		// It is a requirement for multiple interface devices on Windows that, to you
+		// must first claim the first interface before you claim the others
+		if (!HANDLE_VALID(winusb_handle)) {
+			file_handle = handle_priv->interface_handle[0].dev_handle;
+			if (WinUSBX[sub_api].Initialize(file_handle, &winusb_handle)) {
+				handle_priv->interface_handle[0].api_handle = winusb_handle;
+				usbi_warn(ctx, "auto-claimed interface 0 (required to claim %d with WinUSB)", iface);
+			} else {
+				usbi_warn(ctx, "failed to auto-claim interface 0 (required to claim %d with WinUSB): %s", iface, windows_error_str(0));
+				return LIBUSB_ERROR_ACCESS;
+			}
+		}
+		if (!WinUSBX[sub_api].GetAssociatedInterface(winusb_handle, (UCHAR)(iface - 1),
+			&handle_priv->interface_handle[iface].api_handle)) {
+			handle_priv->interface_handle[iface].api_handle = INVALID_HANDLE_VALUE;
+			switch(GetLastError()) {
+			case ERROR_NO_MORE_ITEMS:   // invalid iface
+				return LIBUSB_ERROR_NOT_FOUND;
+			case ERROR_BAD_COMMAND:     // The device was disconnected
+				return LIBUSB_ERROR_NO_DEVICE;
+			case ERROR_ALREADY_EXISTS:  // already claimed
+				return LIBUSB_ERROR_BUSY;
+			default:
+				usbi_err(ctx, "could not claim interface %d: %s", iface, windows_error_str(0));
+				return LIBUSB_ERROR_ACCESS;
+			}
+		}
+	}
+	usbi_dbg("claimed interface %d", iface);
+	handle_priv->active_interface = iface;
+
+	return LIBUSB_SUCCESS;
+}
+
+static int winusbx_release_interface(int sub_api, struct libusb_device_handle *dev_handle, int iface)
+{
+	struct windows_device_handle_priv *handle_priv = _device_handle_priv(dev_handle);
+	struct windows_device_priv *priv = _device_priv(dev_handle->dev);
+	HANDLE winusb_handle;
+
+	CHECK_WINUSBX_AVAILABLE(sub_api);
+
+	winusb_handle = handle_priv->interface_handle[iface].api_handle;
+	if (!HANDLE_VALID(winusb_handle))
+		return LIBUSB_ERROR_NOT_FOUND;
+
+	WinUSBX[sub_api].Free(winusb_handle);
+	handle_priv->interface_handle[iface].api_handle = INVALID_HANDLE_VALUE;
+
+	return LIBUSB_SUCCESS;
+}
+
+/*
+ * Return the first valid interface (of the same API type), for control transfers
+ */
+static int get_valid_interface(struct libusb_device_handle *dev_handle, int api_id)
+{
+	struct windows_device_handle_priv *handle_priv = _device_handle_priv(dev_handle);
+	struct windows_device_priv *priv = _device_priv(dev_handle->dev);
+	int i;
+
+	if ((api_id < USB_API_WINUSBX) || (api_id > USB_API_HID)) {
+		usbi_dbg("unsupported API ID");
+		return -1;
+	}
+
+	for (i = 0; i < USB_MAXINTERFACES; i++) {
+		if (HANDLE_VALID(handle_priv->interface_handle[i].dev_handle)
+				&& HANDLE_VALID(handle_priv->interface_handle[i].api_handle)
+				&& (priv->usb_interface[i].apib->id == api_id))
+			return i;
+	}
+
+	return -1;
+}
+
+/*
+ * Lookup interface by endpoint address. -1 if not found
+ */
+static int interface_by_endpoint(struct windows_device_priv *priv,
+	struct windows_device_handle_priv *handle_priv, uint8_t endpoint_address)
+{
+	int i, j;
+
+	for (i = 0; i < USB_MAXINTERFACES; i++) {
+		if (!HANDLE_VALID(handle_priv->interface_handle[i].api_handle))
+			continue;
+		if (priv->usb_interface[i].endpoint == NULL)
+			continue;
+		for (j = 0; j < priv->usb_interface[i].nb_endpoints; j++) {
+			if (priv->usb_interface[i].endpoint[j] == endpoint_address)
+				return i;
+		}
+	}
+
+	return -1;
+}
+
+static int winusbx_submit_control_transfer(int sub_api, struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	struct libusb_context *ctx = DEVICE_CTX(transfer->dev_handle->dev);
+	struct windows_device_priv *priv = _device_priv(transfer->dev_handle->dev);
+	struct windows_transfer_priv *transfer_priv = usbi_transfer_get_os_priv(itransfer);
+	struct windows_device_handle_priv *handle_priv = _device_handle_priv(transfer->dev_handle);
+	WINUSB_SETUP_PACKET *setup = (WINUSB_SETUP_PACKET *)transfer->buffer;
+	ULONG size;
+	HANDLE winusb_handle;
+	int current_interface;
+	struct winfd wfd;
+
+	CHECK_WINUSBX_AVAILABLE(sub_api);
+
+	transfer_priv->pollable_fd = INVALID_WINFD;
+	size = transfer->length - LIBUSB_CONTROL_SETUP_SIZE;
+
+	// Windows places upper limits on the control transfer size
+	// See: https://msdn.microsoft.com/en-us/library/windows/hardware/ff538112.aspx
+	if (size > MAX_CTRL_BUFFER_LENGTH)
+		return LIBUSB_ERROR_INVALID_PARAM;
+
+	current_interface = get_valid_interface(transfer->dev_handle, USB_API_WINUSBX);
+	if (current_interface < 0) {
+		if (auto_claim(transfer, &current_interface, USB_API_WINUSBX) != LIBUSB_SUCCESS)
+			return LIBUSB_ERROR_NOT_FOUND;
+	}
+
+	usbi_dbg("will use interface %d", current_interface);
+	winusb_handle = handle_priv->interface_handle[current_interface].api_handle;
+
+	wfd = usbi_create_fd(winusb_handle, RW_READ, NULL, NULL);
+	// Always use the handle returned from usbi_create_fd (wfd.handle)
+	if (wfd.fd < 0)
+		return LIBUSB_ERROR_NO_MEM;
+
+	// Sending of set configuration control requests from WinUSB creates issues
+	if (((setup->request_type & (0x03 << 5)) == LIBUSB_REQUEST_TYPE_STANDARD)
+			&& (setup->request == LIBUSB_REQUEST_SET_CONFIGURATION)) {
+		if (setup->value != priv->active_config) {
+			usbi_warn(ctx, "cannot set configuration other than the default one");
+			usbi_free_fd(&wfd);
+			return LIBUSB_ERROR_INVALID_PARAM;
+		}
+		wfd.overlapped->Internal = STATUS_COMPLETED_SYNCHRONOUSLY;
+		wfd.overlapped->InternalHigh = 0;
+	} else {
+		if (!WinUSBX[sub_api].ControlTransfer(wfd.handle, *setup, transfer->buffer + LIBUSB_CONTROL_SETUP_SIZE, size, NULL, wfd.overlapped)) {
+			if (GetLastError() != ERROR_IO_PENDING) {
+				usbi_warn(ctx, "ControlTransfer failed: %s", windows_error_str(0));
+				usbi_free_fd(&wfd);
+				return LIBUSB_ERROR_IO;
+			}
+		} else {
+			wfd.overlapped->Internal = STATUS_COMPLETED_SYNCHRONOUSLY;
+			wfd.overlapped->InternalHigh = (DWORD)size;
+		}
+	}
+
+	// Use priv_transfer to store data needed for async polling
+	transfer_priv->pollable_fd = wfd;
+	transfer_priv->interface_number = (uint8_t)current_interface;
+
+	return LIBUSB_SUCCESS;
+}
+
+static int winusbx_set_interface_altsetting(int sub_api, struct libusb_device_handle *dev_handle, int iface, int altsetting)
+{
+	struct libusb_context *ctx = DEVICE_CTX(dev_handle->dev);
+	struct windows_device_handle_priv *handle_priv = _device_handle_priv(dev_handle);
+	struct windows_device_priv *priv = _device_priv(dev_handle->dev);
+	HANDLE winusb_handle;
+
+	CHECK_WINUSBX_AVAILABLE(sub_api);
+
+	if (altsetting > 255)
+		return LIBUSB_ERROR_INVALID_PARAM;
+
+	winusb_handle = handle_priv->interface_handle[iface].api_handle;
+	if (!HANDLE_VALID(winusb_handle)) {
+		usbi_err(ctx, "interface must be claimed first");
+		return LIBUSB_ERROR_NOT_FOUND;
+	}
+
+	if (!WinUSBX[sub_api].SetCurrentAlternateSetting(winusb_handle, (UCHAR)altsetting)) {
+		usbi_err(ctx, "SetCurrentAlternateSetting failed: %s", windows_error_str(0));
+		return LIBUSB_ERROR_IO;
+	}
+
+	return LIBUSB_SUCCESS;
+}
+
+static int winusbx_submit_bulk_transfer(int sub_api, struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	struct libusb_context *ctx = DEVICE_CTX(transfer->dev_handle->dev);
+	struct windows_transfer_priv *transfer_priv = usbi_transfer_get_os_priv(itransfer);
+	struct windows_device_handle_priv *handle_priv = _device_handle_priv(transfer->dev_handle);
+	struct windows_device_priv *priv = _device_priv(transfer->dev_handle->dev);
+	HANDLE winusb_handle;
+	bool ret;
+	int current_interface;
+	struct winfd wfd;
+
+	CHECK_WINUSBX_AVAILABLE(sub_api);
+
+	transfer_priv->pollable_fd = INVALID_WINFD;
+
+	current_interface = interface_by_endpoint(priv, handle_priv, transfer->endpoint);
+	if (current_interface < 0) {
+		usbi_err(ctx, "unable to match endpoint to an open interface - cancelling transfer");
+		return LIBUSB_ERROR_NOT_FOUND;
+	}
+
+	usbi_dbg("matched endpoint %02X with interface %d", transfer->endpoint, current_interface);
+
+	winusb_handle = handle_priv->interface_handle[current_interface].api_handle;
+
+	wfd = usbi_create_fd(winusb_handle, IS_XFERIN(transfer) ? RW_READ : RW_WRITE, NULL, NULL);
+	// Always use the handle returned from usbi_create_fd (wfd.handle)
+	if (wfd.fd < 0)
+		return LIBUSB_ERROR_NO_MEM;
+
+	if (IS_XFERIN(transfer)) {
+		usbi_dbg("reading %d bytes", transfer->length);
+		ret = WinUSBX[sub_api].ReadPipe(wfd.handle, transfer->endpoint, transfer->buffer, transfer->length, NULL, wfd.overlapped);
+	} else {
+		usbi_dbg("writing %d bytes", transfer->length);
+		ret = WinUSBX[sub_api].WritePipe(wfd.handle, transfer->endpoint, transfer->buffer, transfer->length, NULL, wfd.overlapped);
+	}
+
+	if (!ret) {
+		if (GetLastError() != ERROR_IO_PENDING) {
+			usbi_err(ctx, "ReadPipe/WritePipe failed: %s", windows_error_str(0));
+			usbi_free_fd(&wfd);
+			return LIBUSB_ERROR_IO;
+		}
+	} else {
+		wfd.overlapped->Internal = STATUS_COMPLETED_SYNCHRONOUSLY;
+		wfd.overlapped->InternalHigh = (DWORD)transfer->length;
+	}
+
+	transfer_priv->pollable_fd = wfd;
+	transfer_priv->interface_number = (uint8_t)current_interface;
+
+	return LIBUSB_SUCCESS;
+}
+
+static int winusbx_clear_halt(int sub_api, struct libusb_device_handle *dev_handle, unsigned char endpoint)
+{
+	struct libusb_context *ctx = DEVICE_CTX(dev_handle->dev);
+	struct windows_device_handle_priv *handle_priv = _device_handle_priv(dev_handle);
+	struct windows_device_priv *priv = _device_priv(dev_handle->dev);
+	HANDLE winusb_handle;
+	int current_interface;
+
+	CHECK_WINUSBX_AVAILABLE(sub_api);
+
+	current_interface = interface_by_endpoint(priv, handle_priv, endpoint);
+	if (current_interface < 0) {
+		usbi_err(ctx, "unable to match endpoint to an open interface - cannot clear");
+		return LIBUSB_ERROR_NOT_FOUND;
+	}
+
+	usbi_dbg("matched endpoint %02X with interface %d", endpoint, current_interface);
+	winusb_handle = handle_priv->interface_handle[current_interface].api_handle;
+
+	if (!WinUSBX[sub_api].ResetPipe(winusb_handle, endpoint)) {
+		usbi_err(ctx, "ResetPipe failed: %s", windows_error_str(0));
+		return LIBUSB_ERROR_NO_DEVICE;
+	}
+
+	return LIBUSB_SUCCESS;
+}
+
+/*
+ * from http://www.winvistatips.com/winusb-bugchecks-t335323.html (confirmed
+ * through testing as well):
+ * "You can not call WinUsb_AbortPipe on control pipe. You can possibly cancel
+ * the control transfer using CancelIo"
+ */
+static int winusbx_abort_control(int sub_api, struct usbi_transfer *itransfer)
+{
+	// Cancelling of the I/O is done in the parent
+	return LIBUSB_SUCCESS;
+}
+
+static int winusbx_abort_transfers(int sub_api, struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	struct libusb_context *ctx = DEVICE_CTX(transfer->dev_handle->dev);
+	struct windows_device_handle_priv *handle_priv = _device_handle_priv(transfer->dev_handle);
+	struct windows_transfer_priv *transfer_priv = usbi_transfer_get_os_priv(itransfer);
+	struct windows_device_priv *priv = _device_priv(transfer->dev_handle->dev);
+	HANDLE winusb_handle;
+	int current_interface;
+
+	CHECK_WINUSBX_AVAILABLE(sub_api);
+
+	current_interface = transfer_priv->interface_number;
+	if ((current_interface < 0) || (current_interface >= USB_MAXINTERFACES)) {
+		usbi_err(ctx, "program assertion failed: invalid interface_number");
+		return LIBUSB_ERROR_NOT_FOUND;
+	}
+	usbi_dbg("will use interface %d", current_interface);
+
+	winusb_handle = handle_priv->interface_handle[current_interface].api_handle;
+
+	if (!WinUSBX[sub_api].AbortPipe(winusb_handle, transfer->endpoint)) {
+		usbi_err(ctx, "AbortPipe failed: %s", windows_error_str(0));
+		return LIBUSB_ERROR_NO_DEVICE;
+	}
+
+	return LIBUSB_SUCCESS;
+}
+
+/*
+ * from the "How to Use WinUSB to Communicate with a USB Device" Microsoft white paper
+ * (http://www.microsoft.com/whdc/connect/usb/winusb_howto.mspx):
+ * "WinUSB does not support host-initiated reset port and cycle port operations" and
+ * IOCTL_INTERNAL_USB_CYCLE_PORT is only available in kernel mode and the
+ * IOCTL_USB_HUB_CYCLE_PORT ioctl was removed from Vista => the best we can do is
+ * cycle the pipes (and even then, the control pipe can not be reset using WinUSB)
+ */
+// TODO: (post hotplug): see if we can force eject the device and redetect it (reuse hotplug?)
+static int winusbx_reset_device(int sub_api, struct libusb_device_handle *dev_handle)
+{
+	struct libusb_context *ctx = DEVICE_CTX(dev_handle->dev);
+	struct windows_device_handle_priv *handle_priv = _device_handle_priv(dev_handle);
+	struct windows_device_priv *priv = _device_priv(dev_handle->dev);
+	struct winfd wfd;
+	HANDLE winusb_handle;
+	int i, j;
+
+	CHECK_WINUSBX_AVAILABLE(sub_api);
+
+	// Reset any available pipe (except control)
+	for (i = 0; i < USB_MAXINTERFACES; i++) {
+		winusb_handle = handle_priv->interface_handle[i].api_handle;
+		for (wfd = handle_to_winfd(winusb_handle); wfd.fd > 0; ) {
+			// Cancel any pollable I/O
+			usbi_remove_pollfd(ctx, wfd.fd);
+			usbi_free_fd(&wfd);
+			wfd = handle_to_winfd(winusb_handle);
+		}
+
+		if (HANDLE_VALID(winusb_handle)) {
+			for (j = 0; j < priv->usb_interface[i].nb_endpoints; j++) {
+				usbi_dbg("resetting ep %02X", priv->usb_interface[i].endpoint[j]);
+				if (!WinUSBX[sub_api].AbortPipe(winusb_handle, priv->usb_interface[i].endpoint[j]))
+					usbi_err(ctx, "AbortPipe (pipe address %02X) failed: %s",
+						priv->usb_interface[i].endpoint[j], windows_error_str(0));
+
+				// FlushPipe seems to fail on OUT pipes
+				if (IS_EPIN(priv->usb_interface[i].endpoint[j])
+						&& (!WinUSBX[sub_api].FlushPipe(winusb_handle, priv->usb_interface[i].endpoint[j])))
+					usbi_err(ctx, "FlushPipe (pipe address %02X) failed: %s",
+						priv->usb_interface[i].endpoint[j], windows_error_str(0));
+
+				if (!WinUSBX[sub_api].ResetPipe(winusb_handle, priv->usb_interface[i].endpoint[j]))
+					usbi_err(ctx, "ResetPipe (pipe address %02X) failed: %s",
+						priv->usb_interface[i].endpoint[j], windows_error_str(0));
+			}
+		}
+	}
+
+	// libusbK & libusb0 have the ability to issue an actual device reset
+	if (WinUSBX[sub_api].ResetDevice != NULL) {
+		winusb_handle = handle_priv->interface_handle[0].api_handle;
+		if (HANDLE_VALID(winusb_handle))
+			WinUSBX[sub_api].ResetDevice(winusb_handle);
+	}
+
+	return LIBUSB_SUCCESS;
+}
+
+static int winusbx_copy_transfer_data(int sub_api, struct usbi_transfer *itransfer, uint32_t io_size)
+{
+	itransfer->transferred += io_size;
+	return LIBUSB_TRANSFER_COMPLETED;
+}
+
+/*
+ * Internal HID Support functions (from libusb-win32)
+ * Note that functions that complete data transfer synchronously must return
+ * LIBUSB_COMPLETED instead of LIBUSB_SUCCESS
+ */
+static int _hid_get_hid_descriptor(struct hid_device_priv *dev, void *data, size_t *size);
+static int _hid_get_report_descriptor(struct hid_device_priv *dev, void *data, size_t *size);
+
+static int _hid_wcslen(WCHAR *str)
+{
+	int i = 0;
+
+	while (str[i] && (str[i] != 0x409))
+		i++;
+
+	return i;
+}
+
+static int _hid_get_device_descriptor(struct hid_device_priv *dev, void *data, size_t *size)
+{
+	struct libusb_device_descriptor d;
+
+	d.bLength = LIBUSB_DT_DEVICE_SIZE;
+	d.bDescriptorType = LIBUSB_DT_DEVICE;
+	d.bcdUSB = 0x0200; /* 2.00 */
+	d.bDeviceClass = 0;
+	d.bDeviceSubClass = 0;
+	d.bDeviceProtocol = 0;
+	d.bMaxPacketSize0 = 64; /* fix this! */
+	d.idVendor = (uint16_t)dev->vid;
+	d.idProduct = (uint16_t)dev->pid;
+	d.bcdDevice = 0x0100;
+	d.iManufacturer = dev->string_index[0];
+	d.iProduct = dev->string_index[1];
+	d.iSerialNumber = dev->string_index[2];
+	d.bNumConfigurations = 1;
+
+	if (*size > LIBUSB_DT_DEVICE_SIZE)
+		*size = LIBUSB_DT_DEVICE_SIZE;
+	memcpy(data, &d, *size);
+
+	return LIBUSB_COMPLETED;
+}
+
+static int _hid_get_config_descriptor(struct hid_device_priv *dev, void *data, size_t *size)
+{
+	char num_endpoints = 0;
+	size_t config_total_len = 0;
+	char tmp[HID_MAX_CONFIG_DESC_SIZE];
+	struct libusb_config_descriptor *cd;
+	struct libusb_interface_descriptor *id;
+	struct libusb_hid_descriptor *hd;
+	struct libusb_endpoint_descriptor *ed;
+	size_t tmp_size;
+
+	if (dev->input_report_size)
+		num_endpoints++;
+	if (dev->output_report_size)
+		num_endpoints++;
+
+	config_total_len = LIBUSB_DT_CONFIG_SIZE + LIBUSB_DT_INTERFACE_SIZE
+		+ LIBUSB_DT_HID_SIZE + num_endpoints * LIBUSB_DT_ENDPOINT_SIZE;
+
+	cd = (struct libusb_config_descriptor *)tmp;
+	id = (struct libusb_interface_descriptor *)(tmp + LIBUSB_DT_CONFIG_SIZE);
+	hd = (struct libusb_hid_descriptor *)(tmp + LIBUSB_DT_CONFIG_SIZE
+		+ LIBUSB_DT_INTERFACE_SIZE);
+	ed = (struct libusb_endpoint_descriptor *)(tmp + LIBUSB_DT_CONFIG_SIZE
+		+ LIBUSB_DT_INTERFACE_SIZE
+		+ LIBUSB_DT_HID_SIZE);
+
+	cd->bLength = LIBUSB_DT_CONFIG_SIZE;
+	cd->bDescriptorType = LIBUSB_DT_CONFIG;
+	cd->wTotalLength = (uint16_t)config_total_len;
+	cd->bNumInterfaces = 1;
+	cd->bConfigurationValue = 1;
+	cd->iConfiguration = 0;
+	cd->bmAttributes = 1 << 7; /* bus powered */
+	cd->MaxPower = 50;
+
+	id->bLength = LIBUSB_DT_INTERFACE_SIZE;
+	id->bDescriptorType = LIBUSB_DT_INTERFACE;
+	id->bInterfaceNumber = 0;
+	id->bAlternateSetting = 0;
+	id->bNumEndpoints = num_endpoints;
+	id->bInterfaceClass = 3;
+	id->bInterfaceSubClass = 0;
+	id->bInterfaceProtocol = 0;
+	id->iInterface = 0;
+
+	tmp_size = LIBUSB_DT_HID_SIZE;
+	_hid_get_hid_descriptor(dev, hd, &tmp_size);
+
+	if (dev->input_report_size) {
+		ed->bLength = LIBUSB_DT_ENDPOINT_SIZE;
+		ed->bDescriptorType = LIBUSB_DT_ENDPOINT;
+		ed->bEndpointAddress = HID_IN_EP;
+		ed->bmAttributes = 3;
+		ed->wMaxPacketSize = dev->input_report_size - 1;
+		ed->bInterval = 10;
+		ed = (struct libusb_endpoint_descriptor *)((char *)ed + LIBUSB_DT_ENDPOINT_SIZE);
+	}
+
+	if (dev->output_report_size) {
+		ed->bLength = LIBUSB_DT_ENDPOINT_SIZE;
+		ed->bDescriptorType = LIBUSB_DT_ENDPOINT;
+		ed->bEndpointAddress = HID_OUT_EP;
+		ed->bmAttributes = 3;
+		ed->wMaxPacketSize = dev->output_report_size - 1;
+		ed->bInterval = 10;
+	}
+
+	if (*size > config_total_len)
+		*size = config_total_len;
+	memcpy(data, tmp, *size);
+
+	return LIBUSB_COMPLETED;
+}
+
+static int _hid_get_string_descriptor(struct hid_device_priv *dev, int _index,
+	void *data, size_t *size)
+{
+	void *tmp = NULL;
+	size_t tmp_size = 0;
+	int i;
+
+	/* language ID, EN-US */
+	char string_langid[] = {0x09, 0x04};
+
+	if ((*size < 2) || (*size > 255))
+		return LIBUSB_ERROR_OVERFLOW;
+
+	if (_index == 0) {
+		tmp = string_langid;
+		tmp_size = sizeof(string_langid) + 2;
+	} else {
+		for (i = 0; i < 3; i++) {
+			if (_index == (dev->string_index[i])) {
+				tmp = dev->string[i];
+				tmp_size = (_hid_wcslen(dev->string[i]) + 1) * sizeof(WCHAR);
+				break;
+			}
+		}
+
+		if (i == 3) // not found
+			return LIBUSB_ERROR_INVALID_PARAM;
+	}
+
+	if (!tmp_size)
+		return LIBUSB_ERROR_INVALID_PARAM;
+
+	if (tmp_size < *size)
+		*size = tmp_size;
+
+	// 2 byte header
+	((uint8_t *)data)[0] = (uint8_t)*size;
+	((uint8_t *)data)[1] = LIBUSB_DT_STRING;
+	memcpy((uint8_t *)data + 2, tmp, *size - 2);
+
+	return LIBUSB_COMPLETED;
+}
+
+static int _hid_get_hid_descriptor(struct hid_device_priv *dev, void *data, size_t *size)
+{
+	struct libusb_hid_descriptor d;
+	uint8_t tmp[MAX_HID_DESCRIPTOR_SIZE];
+	size_t report_len = MAX_HID_DESCRIPTOR_SIZE;
+
+	_hid_get_report_descriptor(dev, tmp, &report_len);
+
+	d.bLength = LIBUSB_DT_HID_SIZE;
+	d.bDescriptorType = LIBUSB_DT_HID;
+	d.bcdHID = 0x0110; /* 1.10 */
+	d.bCountryCode = 0;
+	d.bNumDescriptors = 1;
+	d.bClassDescriptorType = LIBUSB_DT_REPORT;
+	d.wClassDescriptorLength = (uint16_t)report_len;
+
+	if (*size > LIBUSB_DT_HID_SIZE)
+		*size = LIBUSB_DT_HID_SIZE;
+	memcpy(data, &d, *size);
+
+	return LIBUSB_COMPLETED;
+}
+
+static int _hid_get_report_descriptor(struct hid_device_priv *dev, void *data, size_t *size)
+{
+	uint8_t d[MAX_HID_DESCRIPTOR_SIZE];
+	size_t i = 0;
+
+	/* usage page (0xFFA0 == vendor defined) */
+	d[i++] = 0x06; d[i++] = 0xA0; d[i++] = 0xFF;
+	/* usage (vendor defined) */
+	d[i++] = 0x09; d[i++] = 0x01;
+	/* start collection (application) */
+	d[i++] = 0xA1; d[i++] = 0x01;
+	/* input report */
+	if (dev->input_report_size) {
+		/* usage (vendor defined) */
+		d[i++] = 0x09; d[i++] = 0x01;
+		/* logical minimum (0) */
+		d[i++] = 0x15; d[i++] = 0x00;
+		/* logical maximum (255) */
+		d[i++] = 0x25; d[i++] = 0xFF;
+		/* report size (8 bits) */
+		d[i++] = 0x75; d[i++] = 0x08;
+		/* report count */
+		d[i++] = 0x95; d[i++] = (uint8_t)dev->input_report_size - 1;
+		/* input (data, variable, absolute) */
+		d[i++] = 0x81; d[i++] = 0x00;
+	}
+	/* output report */
+	if (dev->output_report_size) {
+		/* usage (vendor defined) */
+		d[i++] = 0x09; d[i++] = 0x02;
+		/* logical minimum (0) */
+		d[i++] = 0x15; d[i++] = 0x00;
+		/* logical maximum (255) */
+		d[i++] = 0x25; d[i++] = 0xFF;
+		/* report size (8 bits) */
+		d[i++] = 0x75; d[i++] = 0x08;
+		/* report count */
+		d[i++] = 0x95; d[i++] = (uint8_t)dev->output_report_size - 1;
+		/* output (data, variable, absolute) */
+		d[i++] = 0x91; d[i++] = 0x00;
+	}
+	/* feature report */
+	if (dev->feature_report_size) {
+		/* usage (vendor defined) */
+		d[i++] = 0x09; d[i++] = 0x03;
+		/* logical minimum (0) */
+		d[i++] = 0x15; d[i++] = 0x00;
+		/* logical maximum (255) */
+		d[i++] = 0x25; d[i++] = 0xFF;
+		/* report size (8 bits) */
+		d[i++] = 0x75; d[i++] = 0x08;
+		/* report count */
+		d[i++] = 0x95; d[i++] = (uint8_t)dev->feature_report_size - 1;
+		/* feature (data, variable, absolute) */
+		d[i++] = 0xb2; d[i++] = 0x02; d[i++] = 0x01;
+	}
+
+	/* end collection */
+	d[i++] = 0xC0;
+
+	if (*size > i)
+		*size = i;
+	memcpy(data, d, *size);
+
+	return LIBUSB_COMPLETED;
+}
+
+static int _hid_get_descriptor(struct hid_device_priv *dev, HANDLE hid_handle, int recipient,
+	int type, int _index, void *data, size_t *size)
+{
+	switch(type) {
+	case LIBUSB_DT_DEVICE:
+		usbi_dbg("LIBUSB_DT_DEVICE");
+		return _hid_get_device_descriptor(dev, data, size);
+	case LIBUSB_DT_CONFIG:
+		usbi_dbg("LIBUSB_DT_CONFIG");
+		if (!_index)
+			return _hid_get_config_descriptor(dev, data, size);
+		return LIBUSB_ERROR_INVALID_PARAM;
+	case LIBUSB_DT_STRING:
+		usbi_dbg("LIBUSB_DT_STRING");
+		return _hid_get_string_descriptor(dev, _index, data, size);
+	case LIBUSB_DT_HID:
+		usbi_dbg("LIBUSB_DT_HID");
+		if (!_index)
+			return _hid_get_hid_descriptor(dev, data, size);
+		return LIBUSB_ERROR_INVALID_PARAM;
+	case LIBUSB_DT_REPORT:
+		usbi_dbg("LIBUSB_DT_REPORT");
+		if (!_index)
+			return _hid_get_report_descriptor(dev, data, size);
+		return LIBUSB_ERROR_INVALID_PARAM;
+	case LIBUSB_DT_PHYSICAL:
+		usbi_dbg("LIBUSB_DT_PHYSICAL");
+		if (HidD_GetPhysicalDescriptor(hid_handle, data, (ULONG)*size))
+			return LIBUSB_COMPLETED;
+		return LIBUSB_ERROR_OTHER;
+	}
+
+	usbi_dbg("unsupported");
+	return LIBUSB_ERROR_NOT_SUPPORTED;
+}
+
+static int _hid_get_report(struct hid_device_priv *dev, HANDLE hid_handle, int id, void *data,
+	struct windows_transfer_priv *tp, size_t *size, OVERLAPPED *overlapped, int report_type)
+{
+	uint8_t *buf;
+	DWORD ioctl_code, read_size, expected_size = (DWORD)*size;
+	int r = LIBUSB_SUCCESS;
+
+	if (tp->hid_buffer != NULL)
+		usbi_dbg("program assertion failed: hid_buffer is not NULL");
+
+	if ((*size == 0) || (*size > MAX_HID_REPORT_SIZE)) {
+		usbi_dbg("invalid size (%u)", *size);
+		return LIBUSB_ERROR_INVALID_PARAM;
+	}
+
+	switch (report_type) {
+	case HID_REPORT_TYPE_INPUT:
+		ioctl_code = IOCTL_HID_GET_INPUT_REPORT;
+		break;
+	case HID_REPORT_TYPE_FEATURE:
+		ioctl_code = IOCTL_HID_GET_FEATURE;
+		break;
+	default:
+		usbi_dbg("unknown HID report type %d", report_type);
+		return LIBUSB_ERROR_INVALID_PARAM;
+	}
+
+	// Add a trailing byte to detect overflows
+	buf = calloc(1, expected_size + 1);
+	if (buf == NULL)
+		return LIBUSB_ERROR_NO_MEM;
+
+	buf[0] = (uint8_t)id; // Must be set always
+	usbi_dbg("report ID: 0x%02X", buf[0]);
+
+	tp->hid_expected_size = expected_size;
+	read_size = expected_size;
+
+	// NB: The size returned by DeviceIoControl doesn't include report IDs when not in use (0)
+	if (!DeviceIoControl(hid_handle, ioctl_code, buf, expected_size + 1,
+		buf, expected_size + 1, &read_size, overlapped)) {
+		if (GetLastError() != ERROR_IO_PENDING) {
+			usbi_dbg("Failed to Read HID Report: %s", windows_error_str(0));
+			free(buf);
+			return LIBUSB_ERROR_IO;
+		}
+		// Asynchronous wait
+		tp->hid_buffer = buf;
+		tp->hid_dest = data; // copy dest, as not necessarily the start of the transfer buffer
+		return LIBUSB_SUCCESS;
+	}
+
+	// Transfer completed synchronously => copy and discard extra buffer
+	if (read_size == 0) {
+		usbi_warn(NULL, "program assertion failed - read completed synchronously, but no data was read");
+		*size = 0;
+	} else {
+		if (buf[0] != id)
+			usbi_warn(NULL, "mismatched report ID (data is %02X, parameter is %02X)", buf[0], id);
+
+		if ((size_t)read_size > expected_size) {
+			r = LIBUSB_ERROR_OVERFLOW;
+			usbi_dbg("OVERFLOW!");
+		} else {
+			r = LIBUSB_COMPLETED;
+		}
+
+		*size = MIN((size_t)read_size, *size);
+		if (id == 0)
+			memcpy(data, buf + 1, *size); // Discard report ID
+		else
+			memcpy(data, buf, *size);
+	}
+
+	free(buf);
+	return r;
+}
+
+static int _hid_set_report(struct hid_device_priv *dev, HANDLE hid_handle, int id, void *data,
+	struct windows_transfer_priv *tp, size_t *size, OVERLAPPED *overlapped, int report_type)
+{
+	uint8_t *buf = NULL;
+	DWORD ioctl_code, write_size = (DWORD)*size;
+
+	if (tp->hid_buffer != NULL)
+		usbi_dbg("program assertion failed: hid_buffer is not NULL");
+
+	if ((*size == 0) || (*size > MAX_HID_REPORT_SIZE)) {
+		usbi_dbg("invalid size (%u)", *size);
+		return LIBUSB_ERROR_INVALID_PARAM;
+	}
+
+	switch (report_type) {
+	case HID_REPORT_TYPE_OUTPUT:
+		ioctl_code = IOCTL_HID_SET_OUTPUT_REPORT;
+		break;
+	case HID_REPORT_TYPE_FEATURE:
+		ioctl_code = IOCTL_HID_SET_FEATURE;
+		break;
+	default:
+		usbi_dbg("unknown HID report type %d", report_type);
+		return LIBUSB_ERROR_INVALID_PARAM;
+	}
+
+	usbi_dbg("report ID: 0x%02X", id);
+	// When report IDs are not used (i.e. when id == 0), we must add
+	// a null report ID. Otherwise, we just use original data buffer
+	if (id == 0)
+		write_size++;
+
+	buf = malloc(write_size);
+	if (buf == NULL)
+		return LIBUSB_ERROR_NO_MEM;
+
+	if (id == 0) {
+		buf[0] = 0;
+		memcpy(buf + 1, data, *size);
+	} else {
+		// This seems like a waste, but if we don't duplicate the
+		// data, we'll get issues when freeing hid_buffer
+		memcpy(buf, data, *size);
+		if (buf[0] != id)
+			usbi_warn(NULL, "mismatched report ID (data is %02X, parameter is %02X)", buf[0], id);
+	}
+
+	// NB: The size returned by DeviceIoControl doesn't include report IDs when not in use (0)
+	if (!DeviceIoControl(hid_handle, ioctl_code, buf, write_size,
+		buf, write_size, &write_size, overlapped)) {
+		if (GetLastError() != ERROR_IO_PENDING) {
+			usbi_dbg("Failed to Write HID Output Report: %s", windows_error_str(0));
+			free(buf);
+			return LIBUSB_ERROR_IO;
+		}
+		tp->hid_buffer = buf;
+		tp->hid_dest = NULL;
+		return LIBUSB_SUCCESS;
+	}
+
+	// Transfer completed synchronously
+	*size = write_size;
+	if (write_size == 0)
+		usbi_dbg("program assertion failed - write completed synchronously, but no data was written");
+
+	free(buf);
+	return LIBUSB_COMPLETED;
+}
+
+static int _hid_class_request(struct hid_device_priv *dev, HANDLE hid_handle, int request_type,
+	int request, int value, int _index, void *data, struct windows_transfer_priv *tp,
+	size_t *size, OVERLAPPED *overlapped)
+{
+	int report_type = (value >> 8) & 0xFF;
+	int report_id = value & 0xFF;
+
+	if ((LIBUSB_REQ_RECIPIENT(request_type) != LIBUSB_RECIPIENT_INTERFACE)
+			&& (LIBUSB_REQ_RECIPIENT(request_type) != LIBUSB_RECIPIENT_DEVICE))
+		return LIBUSB_ERROR_INVALID_PARAM;
+
+	if (LIBUSB_REQ_OUT(request_type) && request == HID_REQ_SET_REPORT)
+		return _hid_set_report(dev, hid_handle, report_id, data, tp, size, overlapped, report_type);
+
+	if (LIBUSB_REQ_IN(request_type) && request == HID_REQ_GET_REPORT)
+		return _hid_get_report(dev, hid_handle, report_id, data, tp, size, overlapped, report_type);
+
+	return LIBUSB_ERROR_INVALID_PARAM;
+}
+
+
+/*
+ * HID API functions
+ */
+static int hid_init(int sub_api, struct libusb_context *ctx)
+{
+	DLL_GET_HANDLE(hid);
+	DLL_LOAD_FUNC(hid, HidD_GetAttributes, TRUE);
+	DLL_LOAD_FUNC(hid, HidD_GetHidGuid, TRUE);
+	DLL_LOAD_FUNC(hid, HidD_GetPreparsedData, TRUE);
+	DLL_LOAD_FUNC(hid, HidD_FreePreparsedData, TRUE);
+	DLL_LOAD_FUNC(hid, HidD_GetManufacturerString, TRUE);
+	DLL_LOAD_FUNC(hid, HidD_GetProductString, TRUE);
+	DLL_LOAD_FUNC(hid, HidD_GetSerialNumberString, TRUE);
+	DLL_LOAD_FUNC(hid, HidP_GetCaps, TRUE);
+	DLL_LOAD_FUNC(hid, HidD_SetNumInputBuffers, TRUE);
+	DLL_LOAD_FUNC(hid, HidD_SetFeature, TRUE);
+	DLL_LOAD_FUNC(hid, HidD_GetFeature, TRUE);
+	DLL_LOAD_FUNC(hid, HidD_GetPhysicalDescriptor, TRUE);
+	DLL_LOAD_FUNC(hid, HidD_GetInputReport, FALSE);
+	DLL_LOAD_FUNC(hid, HidD_SetOutputReport, FALSE);
+	DLL_LOAD_FUNC(hid, HidD_FlushQueue, TRUE);
+	DLL_LOAD_FUNC(hid, HidP_GetValueCaps, TRUE);
+
+	api_hid_available = true;
+	return LIBUSB_SUCCESS;
+}
+
+static int hid_exit(int sub_api)
+{
+	DLL_FREE_HANDLE(hid);
+
+	return LIBUSB_SUCCESS;
+}
+
+// NB: open and close must ensure that they only handle interface of
+// the right API type, as these functions can be called wholesale from
+// composite_open(), with interfaces belonging to different APIs
+static int hid_open(int sub_api, struct libusb_device_handle *dev_handle)
+{
+	struct libusb_context *ctx = DEVICE_CTX(dev_handle->dev);
+	struct windows_device_priv *priv = _device_priv(dev_handle->dev);
+	struct windows_device_handle_priv *handle_priv = _device_handle_priv(dev_handle);
+	HIDD_ATTRIBUTES hid_attributes;
+	PHIDP_PREPARSED_DATA preparsed_data = NULL;
+	HIDP_CAPS capabilities;
+	HIDP_VALUE_CAPS *value_caps;
+	HANDLE hid_handle = INVALID_HANDLE_VALUE;
+	int i, j;
+	// report IDs handling
+	ULONG size[3];
+	int nb_ids[2]; // zero and nonzero report IDs
+#if defined(ENABLE_LOGGING)
+	const char *type[3] = {"input", "output", "feature"};
+#endif
+
+	CHECK_HID_AVAILABLE;
+
+	if (priv->hid == NULL) {
+		usbi_err(ctx, "program assertion failed - private HID structure is unitialized");
+		return LIBUSB_ERROR_NOT_FOUND;
+	}
+
+	for (i = 0; i < USB_MAXINTERFACES; i++) {
+		if ((priv->usb_interface[i].path != NULL)
+				&& (priv->usb_interface[i].apib->id == USB_API_HID)) {
+			hid_handle = CreateFileA(priv->usb_interface[i].path, GENERIC_WRITE | GENERIC_READ, FILE_SHARE_WRITE | FILE_SHARE_READ,
+				NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED, NULL);
+			/*
+			 * http://www.lvr.com/hidfaq.htm: Why do I receive "Access denied" when attempting to access my HID?
+			 * "Windows 2000 and later have exclusive read/write access to HIDs that are configured as a system
+			 * keyboards or mice. An application can obtain a handle to a system keyboard or mouse by not
+			 * requesting READ or WRITE access with CreateFile. Applications can then use HidD_SetFeature and
+			 * HidD_GetFeature (if the device supports Feature reports)."
+			 */
+			if (hid_handle == INVALID_HANDLE_VALUE) {
+				usbi_warn(ctx, "could not open HID device in R/W mode (keyboard or mouse?) - trying without");
+				hid_handle = CreateFileA(priv->usb_interface[i].path, 0, FILE_SHARE_WRITE | FILE_SHARE_READ,
+					NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED, NULL);
+				if (hid_handle == INVALID_HANDLE_VALUE) {
+					usbi_err(ctx, "could not open device %s (interface %d): %s", priv->path, i, windows_error_str(0));
+					switch(GetLastError()) {
+					case ERROR_FILE_NOT_FOUND: // The device was disconnected
+						return LIBUSB_ERROR_NO_DEVICE;
+					case ERROR_ACCESS_DENIED:
+						return LIBUSB_ERROR_ACCESS;
+					default:
+						return LIBUSB_ERROR_IO;
+					}
+				}
+				priv->usb_interface[i].restricted_functionality = true;
+			}
+			handle_priv->interface_handle[i].api_handle = hid_handle;
+		}
+	}
+
+	hid_attributes.Size = sizeof(hid_attributes);
+	do {
+		if (!HidD_GetAttributes(hid_handle, &hid_attributes)) {
+			usbi_err(ctx, "could not gain access to HID top collection (HidD_GetAttributes)");
+			break;
+		}
+
+		priv->hid->vid = hid_attributes.VendorID;
+		priv->hid->pid = hid_attributes.ProductID;
+
+		// Set the maximum available input buffer size
+		for (i = 32; HidD_SetNumInputBuffers(hid_handle, i); i *= 2);
+		usbi_dbg("set maximum input buffer size to %d", i / 2);
+
+		// Get the maximum input and output report size
+		if (!HidD_GetPreparsedData(hid_handle, &preparsed_data) || !preparsed_data) {
+			usbi_err(ctx, "could not read HID preparsed data (HidD_GetPreparsedData)");
+			break;
+		}
+		if (HidP_GetCaps(preparsed_data, &capabilities) != HIDP_STATUS_SUCCESS) {
+			usbi_err(ctx, "could not parse HID capabilities (HidP_GetCaps)");
+			break;
+		}
+
+		// Find out if interrupt will need report IDs
+		size[0] = capabilities.NumberInputValueCaps;
+		size[1] = capabilities.NumberOutputValueCaps;
+		size[2] = capabilities.NumberFeatureValueCaps;
+		for (j = HidP_Input; j <= HidP_Feature; j++) {
+			usbi_dbg("%u HID %s report value(s) found", (unsigned int)size[j], type[j]);
+			priv->hid->uses_report_ids[j] = false;
+			if (size[j] > 0) {
+				value_caps = calloc(size[j], sizeof(HIDP_VALUE_CAPS));
+				if ((value_caps != NULL)
+						&& (HidP_GetValueCaps((HIDP_REPORT_TYPE)j, value_caps, &size[j], preparsed_data) == HIDP_STATUS_SUCCESS)
+						&& (size[j] >= 1)) {
+					nb_ids[0] = 0;
+					nb_ids[1] = 0;
+					for (i = 0; i < (int)size[j]; i++) {
+						usbi_dbg("  Report ID: 0x%02X", value_caps[i].ReportID);
+						if (value_caps[i].ReportID != 0)
+							nb_ids[1]++;
+						else
+							nb_ids[0]++;
+					}
+					if (nb_ids[1] != 0) {
+						if (nb_ids[0] != 0)
+							usbi_warn(ctx, "program assertion failed: zero and nonzero report IDs used for %s",
+								type[j]);
+						priv->hid->uses_report_ids[j] = true;
+					}
+				} else {
+					usbi_warn(ctx, "  could not process %s report IDs", type[j]);
+				}
+				free(value_caps);
+			}
+		}
+
+		// Set the report sizes
+		priv->hid->input_report_size = capabilities.InputReportByteLength;
+		priv->hid->output_report_size = capabilities.OutputReportByteLength;
+		priv->hid->feature_report_size = capabilities.FeatureReportByteLength;
+
+		// Fetch string descriptors
+		priv->hid->string_index[0] = priv->dev_descriptor.iManufacturer;
+		if (priv->hid->string_index[0] != 0)
+			HidD_GetManufacturerString(hid_handle, priv->hid->string[0], sizeof(priv->hid->string[0]));
+		else
+			priv->hid->string[0][0] = 0;
+
+		priv->hid->string_index[1] = priv->dev_descriptor.iProduct;
+		if (priv->hid->string_index[1] != 0)
+			HidD_GetProductString(hid_handle, priv->hid->string[1], sizeof(priv->hid->string[1]));
+		else
+			priv->hid->string[1][0] = 0;
+
+		priv->hid->string_index[2] = priv->dev_descriptor.iSerialNumber;
+		if (priv->hid->string_index[2] != 0)
+			HidD_GetSerialNumberString(hid_handle, priv->hid->string[2], sizeof(priv->hid->string[2]));
+		else
+			priv->hid->string[2][0] = 0;
+	} while(0);
+
+	if (preparsed_data)
+		HidD_FreePreparsedData(preparsed_data);
+
+	return LIBUSB_SUCCESS;
+}
+
+static void hid_close(int sub_api, struct libusb_device_handle *dev_handle)
+{
+	struct windows_device_priv *priv = _device_priv(dev_handle->dev);
+	struct windows_device_handle_priv *handle_priv = _device_handle_priv(dev_handle);
+	HANDLE file_handle;
+	int i;
+
+	if (!api_hid_available)
+		return;
+
+	for (i = 0; i < USB_MAXINTERFACES; i++) {
+		if (priv->usb_interface[i].apib->id == USB_API_HID) {
+			file_handle = handle_priv->interface_handle[i].api_handle;
+			if (HANDLE_VALID(file_handle))
+				CloseHandle(file_handle);
+		}
+	}
+}
+
+static int hid_claim_interface(int sub_api, struct libusb_device_handle *dev_handle, int iface)
+{
+	struct windows_device_handle_priv *handle_priv = _device_handle_priv(dev_handle);
+	struct windows_device_priv *priv = _device_priv(dev_handle->dev);
+
+	CHECK_HID_AVAILABLE;
+
+	// NB: Disconnection detection is not possible in this function
+	if (priv->usb_interface[iface].path == NULL)
+		return LIBUSB_ERROR_NOT_FOUND; // invalid iface
+
+	// We use dev_handle as a flag for interface claimed
+	if (handle_priv->interface_handle[iface].dev_handle == INTERFACE_CLAIMED)
+		return LIBUSB_ERROR_BUSY; // already claimed
+
+
+	handle_priv->interface_handle[iface].dev_handle = INTERFACE_CLAIMED;
+
+	usbi_dbg("claimed interface %d", iface);
+	handle_priv->active_interface = iface;
+
+	return LIBUSB_SUCCESS;
+}
+
+static int hid_release_interface(int sub_api, struct libusb_device_handle *dev_handle, int iface)
+{
+	struct windows_device_handle_priv *handle_priv = _device_handle_priv(dev_handle);
+	struct windows_device_priv *priv = _device_priv(dev_handle->dev);
+
+	CHECK_HID_AVAILABLE;
+
+	if (priv->usb_interface[iface].path == NULL)
+		return LIBUSB_ERROR_NOT_FOUND; // invalid iface
+
+	if (handle_priv->interface_handle[iface].dev_handle != INTERFACE_CLAIMED)
+		return LIBUSB_ERROR_NOT_FOUND; // invalid iface
+
+	handle_priv->interface_handle[iface].dev_handle = INVALID_HANDLE_VALUE;
+
+	return LIBUSB_SUCCESS;
+}
+
+static int hid_set_interface_altsetting(int sub_api, struct libusb_device_handle *dev_handle, int iface, int altsetting)
+{
+	struct libusb_context *ctx = DEVICE_CTX(dev_handle->dev);
+
+	CHECK_HID_AVAILABLE;
+
+	if (altsetting > 255)
+		return LIBUSB_ERROR_INVALID_PARAM;
+
+	if (altsetting != 0) {
+		usbi_err(ctx, "set interface altsetting not supported for altsetting >0");
+		return LIBUSB_ERROR_NOT_SUPPORTED;
+	}
+
+	return LIBUSB_SUCCESS;
+}
+
+static int hid_submit_control_transfer(int sub_api, struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	struct windows_transfer_priv *transfer_priv = usbi_transfer_get_os_priv(itransfer);
+	struct windows_device_handle_priv *handle_priv = _device_handle_priv(transfer->dev_handle);
+	struct windows_device_priv *priv = _device_priv(transfer->dev_handle->dev);
+	struct libusb_context *ctx = DEVICE_CTX(transfer->dev_handle->dev);
+	WINUSB_SETUP_PACKET *setup = (WINUSB_SETUP_PACKET *)transfer->buffer;
+	HANDLE hid_handle;
+	struct winfd wfd;
+	int current_interface, config;
+	size_t size;
+	int r = LIBUSB_ERROR_INVALID_PARAM;
+
+	CHECK_HID_AVAILABLE;
+
+	transfer_priv->pollable_fd = INVALID_WINFD;
+	safe_free(transfer_priv->hid_buffer);
+	transfer_priv->hid_dest = NULL;
+	size = transfer->length - LIBUSB_CONTROL_SETUP_SIZE;
+
+	if (size > MAX_CTRL_BUFFER_LENGTH)
+		return LIBUSB_ERROR_INVALID_PARAM;
+
+	current_interface = get_valid_interface(transfer->dev_handle, USB_API_HID);
+	if (current_interface < 0) {
+		if (auto_claim(transfer, &current_interface, USB_API_HID) != LIBUSB_SUCCESS)
+			return LIBUSB_ERROR_NOT_FOUND;
+	}
+
+	usbi_dbg("will use interface %d", current_interface);
+	hid_handle = handle_priv->interface_handle[current_interface].api_handle;
+	// Always use the handle returned from usbi_create_fd (wfd.handle)
+	wfd = usbi_create_fd(hid_handle, RW_READ, NULL, NULL);
+	if (wfd.fd < 0)
+		return LIBUSB_ERROR_NOT_FOUND;
+
+	switch(LIBUSB_REQ_TYPE(setup->request_type)) {
+	case LIBUSB_REQUEST_TYPE_STANDARD:
+		switch(setup->request) {
+		case LIBUSB_REQUEST_GET_DESCRIPTOR:
+			r = _hid_get_descriptor(priv->hid, wfd.handle, LIBUSB_REQ_RECIPIENT(setup->request_type),
+				(setup->value >> 8) & 0xFF, setup->value & 0xFF, transfer->buffer + LIBUSB_CONTROL_SETUP_SIZE, &size);
+			break;
+		case LIBUSB_REQUEST_GET_CONFIGURATION:
+			r = windows_get_configuration(transfer->dev_handle, &config);
+			if (r == LIBUSB_SUCCESS) {
+				size = 1;
+				((uint8_t *)transfer->buffer)[LIBUSB_CONTROL_SETUP_SIZE] = (uint8_t)config;
+				r = LIBUSB_COMPLETED;
+			}
+			break;
+		case LIBUSB_REQUEST_SET_CONFIGURATION:
+			if (setup->value == priv->active_config) {
+				r = LIBUSB_COMPLETED;
+			} else {
+				usbi_warn(ctx, "cannot set configuration other than the default one");
+				r = LIBUSB_ERROR_NOT_SUPPORTED;
+			}
+			break;
+		case LIBUSB_REQUEST_GET_INTERFACE:
+			size = 1;
+			((uint8_t *)transfer->buffer)[LIBUSB_CONTROL_SETUP_SIZE] = 0;
+			r = LIBUSB_COMPLETED;
+			break;
+		case LIBUSB_REQUEST_SET_INTERFACE:
+			r = hid_set_interface_altsetting(0, transfer->dev_handle, setup->index, setup->value);
+			if (r == LIBUSB_SUCCESS)
+				r = LIBUSB_COMPLETED;
+			break;
+		default:
+			usbi_warn(ctx, "unsupported HID control request");
+			r = LIBUSB_ERROR_NOT_SUPPORTED;
+			break;
+		}
+		break;
+	case LIBUSB_REQUEST_TYPE_CLASS:
+		r = _hid_class_request(priv->hid, wfd.handle, setup->request_type, setup->request, setup->value,
+			setup->index, transfer->buffer + LIBUSB_CONTROL_SETUP_SIZE, transfer_priv,
+			&size, wfd.overlapped);
+		break;
+	default:
+		usbi_warn(ctx, "unsupported HID control request");
+		r = LIBUSB_ERROR_NOT_SUPPORTED;
+		break;
+	}
+
+	if (r == LIBUSB_COMPLETED) {
+		// Force request to be completed synchronously. Transferred size has been set by previous call
+		wfd.overlapped->Internal = STATUS_COMPLETED_SYNCHRONOUSLY;
+		// http://msdn.microsoft.com/en-us/library/ms684342%28VS.85%29.aspx
+		// set InternalHigh to the number of bytes transferred
+		wfd.overlapped->InternalHigh = (DWORD)size;
+		r = LIBUSB_SUCCESS;
+	}
+
+	if (r == LIBUSB_SUCCESS) {
+		// Use priv_transfer to store data needed for async polling
+		transfer_priv->pollable_fd = wfd;
+		transfer_priv->interface_number = (uint8_t)current_interface;
+	} else {
+		usbi_free_fd(&wfd);
+	}
+
+	return r;
+}
+
+static int hid_submit_bulk_transfer(int sub_api, struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	struct windows_transfer_priv *transfer_priv = usbi_transfer_get_os_priv(itransfer);
+	struct libusb_context *ctx = DEVICE_CTX(transfer->dev_handle->dev);
+	struct windows_device_handle_priv *handle_priv = _device_handle_priv(transfer->dev_handle);
+	struct windows_device_priv *priv = _device_priv(transfer->dev_handle->dev);
+	struct winfd wfd;
+	HANDLE hid_handle;
+	bool direction_in, ret;
+	int current_interface, length;
+	DWORD size;
+	int r = LIBUSB_SUCCESS;
+
+	CHECK_HID_AVAILABLE;
+
+	transfer_priv->pollable_fd = INVALID_WINFD;
+	transfer_priv->hid_dest = NULL;
+	safe_free(transfer_priv->hid_buffer);
+
+	current_interface = interface_by_endpoint(priv, handle_priv, transfer->endpoint);
+	if (current_interface < 0) {
+		usbi_err(ctx, "unable to match endpoint to an open interface - cancelling transfer");
+		return LIBUSB_ERROR_NOT_FOUND;
+	}
+
+	usbi_dbg("matched endpoint %02X with interface %d", transfer->endpoint, current_interface);
+
+	hid_handle = handle_priv->interface_handle[current_interface].api_handle;
+	direction_in = transfer->endpoint & LIBUSB_ENDPOINT_IN;
+
+	wfd = usbi_create_fd(hid_handle, direction_in?RW_READ:RW_WRITE, NULL, NULL);
+	// Always use the handle returned from usbi_create_fd (wfd.handle)
+	if (wfd.fd < 0)
+		return LIBUSB_ERROR_NO_MEM;
+
+	// If report IDs are not in use, an extra prefix byte must be added
+	if (((direction_in) && (!priv->hid->uses_report_ids[0]))
+			|| ((!direction_in) && (!priv->hid->uses_report_ids[1])))
+		length = transfer->length + 1;
+	else
+		length = transfer->length;
+
+	// Add a trailing byte to detect overflows on input
+	transfer_priv->hid_buffer = calloc(1, length + 1);
+	if (transfer_priv->hid_buffer == NULL)
+		return LIBUSB_ERROR_NO_MEM;
+
+	transfer_priv->hid_expected_size = length;
+
+	if (direction_in) {
+		transfer_priv->hid_dest = transfer->buffer;
+		usbi_dbg("reading %d bytes (report ID: 0x00)", length);
+		ret = ReadFile(wfd.handle, transfer_priv->hid_buffer, length + 1, &size, wfd.overlapped);
+	} else {
+		if (!priv->hid->uses_report_ids[1])
+			memcpy(transfer_priv->hid_buffer + 1, transfer->buffer, transfer->length);
+		else
+			// We could actually do without the calloc and memcpy in this case
+			memcpy(transfer_priv->hid_buffer, transfer->buffer, transfer->length);
+
+		usbi_dbg("writing %d bytes (report ID: 0x%02X)", length, transfer_priv->hid_buffer[0]);
+		ret = WriteFile(wfd.handle, transfer_priv->hid_buffer, length, &size, wfd.overlapped);
+	}
+
+	if (!ret) {
+		if (GetLastError() != ERROR_IO_PENDING) {
+			usbi_err(ctx, "HID transfer failed: %s", windows_error_str(0));
+			usbi_free_fd(&wfd);
+			safe_free(transfer_priv->hid_buffer);
+			return LIBUSB_ERROR_IO;
+		}
+	} else {
+		// Only write operations that completed synchronously need to free up
+		// hid_buffer. For reads, copy_transfer_data() handles that process.
+		if (!direction_in)
+			safe_free(transfer_priv->hid_buffer);
+
+		if (size == 0) {
+			usbi_err(ctx, "program assertion failed - no data was transferred");
+			size = 1;
+		}
+		if (size > (size_t)length) {
+			usbi_err(ctx, "OVERFLOW!");
+			r = LIBUSB_ERROR_OVERFLOW;
+		}
+		wfd.overlapped->Internal = STATUS_COMPLETED_SYNCHRONOUSLY;
+		wfd.overlapped->InternalHigh = size;
+	}
+
+	transfer_priv->pollable_fd = wfd;
+	transfer_priv->interface_number = (uint8_t)current_interface;
+
+	return r;
+}
+
+static int hid_abort_transfers(int sub_api, struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	struct windows_transfer_priv *transfer_priv = usbi_transfer_get_os_priv(itransfer);
+	struct windows_device_handle_priv *handle_priv = _device_handle_priv(transfer->dev_handle);
+	HANDLE hid_handle;
+	int current_interface;
+
+	CHECK_HID_AVAILABLE;
+
+	current_interface = transfer_priv->interface_number;
+	hid_handle = handle_priv->interface_handle[current_interface].api_handle;
+	CancelIo(hid_handle);
+
+	return LIBUSB_SUCCESS;
+}
+
+static int hid_reset_device(int sub_api, struct libusb_device_handle *dev_handle)
+{
+	struct windows_device_handle_priv *handle_priv = _device_handle_priv(dev_handle);
+	HANDLE hid_handle;
+	int current_interface;
+
+	CHECK_HID_AVAILABLE;
+
+	// Flushing the queues on all interfaces is the best we can achieve
+	for (current_interface = 0; current_interface < USB_MAXINTERFACES; current_interface++) {
+		hid_handle = handle_priv->interface_handle[current_interface].api_handle;
+		if (HANDLE_VALID(hid_handle))
+			HidD_FlushQueue(hid_handle);
+	}
+
+	return LIBUSB_SUCCESS;
+}
+
+static int hid_clear_halt(int sub_api, struct libusb_device_handle *dev_handle, unsigned char endpoint)
+{
+	struct libusb_context *ctx = DEVICE_CTX(dev_handle->dev);
+	struct windows_device_handle_priv *handle_priv = _device_handle_priv(dev_handle);
+	struct windows_device_priv *priv = _device_priv(dev_handle->dev);
+	HANDLE hid_handle;
+	int current_interface;
+
+	CHECK_HID_AVAILABLE;
+
+	current_interface = interface_by_endpoint(priv, handle_priv, endpoint);
+	if (current_interface < 0) {
+		usbi_err(ctx, "unable to match endpoint to an open interface - cannot clear");
+		return LIBUSB_ERROR_NOT_FOUND;
+	}
+
+	usbi_dbg("matched endpoint %02X with interface %d", endpoint, current_interface);
+	hid_handle = handle_priv->interface_handle[current_interface].api_handle;
+
+	// No endpoint selection with Microsoft's implementation, so we try to flush the
+	// whole interface. Should be OK for most case scenarios
+	if (!HidD_FlushQueue(hid_handle)) {
+		usbi_err(ctx, "Flushing of HID queue failed: %s", windows_error_str(0));
+		// Device was probably disconnected
+		return LIBUSB_ERROR_NO_DEVICE;
+	}
+
+	return LIBUSB_SUCCESS;
+}
+
+// This extra function is only needed for HID
+static int hid_copy_transfer_data(int sub_api, struct usbi_transfer *itransfer, uint32_t io_size)
+{
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	struct libusb_context *ctx = DEVICE_CTX(transfer->dev_handle->dev);
+	struct windows_transfer_priv *transfer_priv = usbi_transfer_get_os_priv(itransfer);
+	int r = LIBUSB_TRANSFER_COMPLETED;
+	uint32_t corrected_size = io_size;
+
+	if (transfer_priv->hid_buffer != NULL) {
+		// If we have a valid hid_buffer, it means the transfer was async
+		if (transfer_priv->hid_dest != NULL) { // Data readout
+			if (corrected_size > 0) {
+				// First, check for overflow
+				if (corrected_size > transfer_priv->hid_expected_size) {
+					usbi_err(ctx, "OVERFLOW!");
+					corrected_size = (uint32_t)transfer_priv->hid_expected_size;
+					r = LIBUSB_TRANSFER_OVERFLOW;
+				}
+
+				if (transfer_priv->hid_buffer[0] == 0) {
+					// Discard the 1 byte report ID prefix
+					corrected_size--;
+					memcpy(transfer_priv->hid_dest, transfer_priv->hid_buffer + 1, corrected_size);
+				} else {
+					memcpy(transfer_priv->hid_dest, transfer_priv->hid_buffer, corrected_size);
+				}
+			}
+			transfer_priv->hid_dest = NULL;
+		}
+		// For write, we just need to free the hid buffer
+		safe_free(transfer_priv->hid_buffer);
+	}
+
+	itransfer->transferred += corrected_size;
+	return r;
+}
+
+
+/*
+ * Composite API functions
+ */
+static int composite_init(int sub_api, struct libusb_context *ctx)
+{
+	return LIBUSB_SUCCESS;
+}
+
+static int composite_exit(int sub_api)
+{
+	return LIBUSB_SUCCESS;
+}
+
+static int composite_open(int sub_api, struct libusb_device_handle *dev_handle)
+{
+	struct windows_device_priv *priv = _device_priv(dev_handle->dev);
+	int r = LIBUSB_ERROR_NOT_FOUND;
+	uint8_t i;
+	// SUB_API_MAX + 1 as the SUB_API_MAX pos is used to indicate availability of HID
+	bool available[SUB_API_MAX + 1] = { 0 };
+
+	for (i = 0; i < USB_MAXINTERFACES; i++) {
+		switch (priv->usb_interface[i].apib->id) {
+		case USB_API_WINUSBX:
+			if (priv->usb_interface[i].sub_api != SUB_API_NOTSET)
+				available[priv->usb_interface[i].sub_api] = true;
+			break;
+		case USB_API_HID:
+			available[SUB_API_MAX] = true;
+			break;
+		default:
+			break;
+		}
+	}
+
+	for (i = 0; i < SUB_API_MAX; i++) { // WinUSB-like drivers
+		if (available[i]) {
+			r = usb_api_backend[USB_API_WINUSBX].open(i, dev_handle);
+			if (r != LIBUSB_SUCCESS)
+				return r;
+		}
+	}
+
+	if (available[SUB_API_MAX]) // HID driver
+		r = hid_open(SUB_API_NOTSET, dev_handle);
+
+	return r;
+}
+
+static void composite_close(int sub_api, struct libusb_device_handle *dev_handle)
+{
+	struct windows_device_priv *priv = _device_priv(dev_handle->dev);
+	uint8_t i;
+	// SUB_API_MAX + 1 as the SUB_API_MAX pos is used to indicate availability of HID
+	bool available[SUB_API_MAX + 1] = { 0 };
+
+	for (i = 0; i < USB_MAXINTERFACES; i++) {
+		switch (priv->usb_interface[i].apib->id) {
+		case USB_API_WINUSBX:
+			if (priv->usb_interface[i].sub_api != SUB_API_NOTSET)
+				available[priv->usb_interface[i].sub_api] = true;
+			break;
+		case USB_API_HID:
+			available[SUB_API_MAX] = true;
+			break;
+		default:
+			break;
+		}
+	}
+
+	for (i = 0; i < SUB_API_MAX; i++) { // WinUSB-like drivers
+		if (available[i])
+			usb_api_backend[USB_API_WINUSBX].close(i, dev_handle);
+	}
+
+	if (available[SUB_API_MAX]) // HID driver
+		hid_close(SUB_API_NOTSET, dev_handle);
+}
+
+static int composite_claim_interface(int sub_api, struct libusb_device_handle *dev_handle, int iface)
+{
+	struct windows_device_priv *priv = _device_priv(dev_handle->dev);
+
+	return priv->usb_interface[iface].apib->
+		claim_interface(priv->usb_interface[iface].sub_api, dev_handle, iface);
+}
+
+static int composite_set_interface_altsetting(int sub_api, struct libusb_device_handle *dev_handle, int iface, int altsetting)
+{
+	struct windows_device_priv *priv = _device_priv(dev_handle->dev);
+
+	return priv->usb_interface[iface].apib->
+		set_interface_altsetting(priv->usb_interface[iface].sub_api, dev_handle, iface, altsetting);
+}
+
+static int composite_release_interface(int sub_api, struct libusb_device_handle *dev_handle, int iface)
+{
+	struct windows_device_priv *priv = _device_priv(dev_handle->dev);
+
+	return priv->usb_interface[iface].apib->
+		release_interface(priv->usb_interface[iface].sub_api, dev_handle, iface);
+}
+
+static int composite_submit_control_transfer(int sub_api, struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	struct libusb_context *ctx = DEVICE_CTX(transfer->dev_handle->dev);
+	struct windows_device_priv *priv = _device_priv(transfer->dev_handle->dev);
+	struct libusb_config_descriptor *conf_desc;
+	WINUSB_SETUP_PACKET *setup = (WINUSB_SETUP_PACKET *)transfer->buffer;
+	int iface, pass, r;
+
+	// Interface shouldn't matter for control, but it does in practice, with Windows'
+	// restrictions with regards to accessing HID keyboards and mice. Try to target
+	// a specific interface first, if possible.
+	switch (LIBUSB_REQ_RECIPIENT(setup->request_type)) {
+	case LIBUSB_RECIPIENT_INTERFACE:
+		iface = setup->index & 0xFF;
+		break;
+	case LIBUSB_RECIPIENT_ENDPOINT:
+		r = libusb_get_active_config_descriptor(transfer->dev_handle->dev, &conf_desc);
+		if (r == LIBUSB_SUCCESS) {
+			iface = get_interface_by_endpoint(conf_desc, (setup->index & 0xFF));
+			libusb_free_config_descriptor(conf_desc);
+			break;
+		}
+		// Fall through if not able to determine interface
+	default:
+		iface = -1;
+		break;
+	}
+
+	// Try and target a specific interface if the control setup indicates such
+	if ((iface >= 0) && (iface < USB_MAXINTERFACES)) {
+		usbi_dbg("attempting control transfer targeted to interface %d", iface);
+		if (priv->usb_interface[iface].path != NULL) {
+			r = priv->usb_interface[iface].apib->submit_control_transfer(priv->usb_interface[iface].sub_api, itransfer);
+			if (r == LIBUSB_SUCCESS)
+				return r;
+		}
+	}
+
+	// Either not targeted to a specific interface or no luck in doing so.
+	// Try a 2 pass approach with all interfaces.
+	for (pass = 0; pass < 2; pass++) {
+		for (iface = 0; iface < USB_MAXINTERFACES; iface++) {
+			if (priv->usb_interface[iface].path != NULL) {
+				if ((pass == 0) && (priv->usb_interface[iface].restricted_functionality)) {
+					usbi_dbg("trying to skip restricted interface #%d (HID keyboard or mouse?)", iface);
+					continue;
+				}
+				usbi_dbg("using interface %d", iface);
+				r = priv->usb_interface[iface].apib->submit_control_transfer(priv->usb_interface[iface].sub_api, itransfer);
+				// If not supported on this API, it may be supported on another, so don't give up yet!!
+				if (r == LIBUSB_ERROR_NOT_SUPPORTED)
+					continue;
+				return r;
+			}
+		}
+	}
+
+	usbi_err(ctx, "no libusb supported interfaces to complete request");
+	return LIBUSB_ERROR_NOT_FOUND;
+}
+
+static int composite_submit_bulk_transfer(int sub_api, struct usbi_transfer *itransfer) {
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	struct libusb_context *ctx = DEVICE_CTX(transfer->dev_handle->dev);
+	struct windows_device_handle_priv *handle_priv = _device_handle_priv(transfer->dev_handle);
+	struct windows_device_priv *priv = _device_priv(transfer->dev_handle->dev);
+	int current_interface;
+
+	current_interface = interface_by_endpoint(priv, handle_priv, transfer->endpoint);
+	if (current_interface < 0) {
+		usbi_err(ctx, "unable to match endpoint to an open interface - cancelling transfer");
+		return LIBUSB_ERROR_NOT_FOUND;
+	}
+
+	return priv->usb_interface[current_interface].apib->
+		submit_bulk_transfer(priv->usb_interface[current_interface].sub_api, itransfer);
+}
+
+static int composite_submit_iso_transfer(int sub_api, struct usbi_transfer *itransfer) {
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	struct libusb_context *ctx = DEVICE_CTX(transfer->dev_handle->dev);
+	struct windows_device_handle_priv *handle_priv = _device_handle_priv(transfer->dev_handle);
+	struct windows_device_priv *priv = _device_priv(transfer->dev_handle->dev);
+	int current_interface;
+
+	current_interface = interface_by_endpoint(priv, handle_priv, transfer->endpoint);
+	if (current_interface < 0) {
+		usbi_err(ctx, "unable to match endpoint to an open interface - cancelling transfer");
+		return LIBUSB_ERROR_NOT_FOUND;
+	}
+
+	return priv->usb_interface[current_interface].apib->
+		submit_iso_transfer(priv->usb_interface[current_interface].sub_api, itransfer);
+}
+
+static int composite_clear_halt(int sub_api, struct libusb_device_handle *dev_handle, unsigned char endpoint)
+{
+	struct libusb_context *ctx = DEVICE_CTX(dev_handle->dev);
+	struct windows_device_handle_priv *handle_priv = _device_handle_priv(dev_handle);
+	struct windows_device_priv *priv = _device_priv(dev_handle->dev);
+	int current_interface;
+
+	current_interface = interface_by_endpoint(priv, handle_priv, endpoint);
+	if (current_interface < 0) {
+		usbi_err(ctx, "unable to match endpoint to an open interface - cannot clear");
+		return LIBUSB_ERROR_NOT_FOUND;
+	}
+
+	return priv->usb_interface[current_interface].apib->
+		clear_halt(priv->usb_interface[current_interface].sub_api, dev_handle, endpoint);
+}
+
+static int composite_abort_control(int sub_api, struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	struct windows_transfer_priv *transfer_priv = usbi_transfer_get_os_priv(itransfer);
+	struct windows_device_priv *priv = _device_priv(transfer->dev_handle->dev);
+
+	return priv->usb_interface[transfer_priv->interface_number].apib->
+		abort_control(priv->usb_interface[transfer_priv->interface_number].sub_api, itransfer);
+}
+
+static int composite_abort_transfers(int sub_api, struct usbi_transfer *itransfer)
+{
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	struct windows_transfer_priv *transfer_priv = usbi_transfer_get_os_priv(itransfer);
+	struct windows_device_priv *priv = _device_priv(transfer->dev_handle->dev);
+
+	return priv->usb_interface[transfer_priv->interface_number].apib->
+		abort_transfers(priv->usb_interface[transfer_priv->interface_number].sub_api, itransfer);
+}
+
+static int composite_reset_device(int sub_api, struct libusb_device_handle *dev_handle)
+{
+	struct windows_device_priv *priv = _device_priv(dev_handle->dev);
+	int r;
+	uint8_t i;
+	bool available[SUB_API_MAX];
+
+	for (i = 0; i < SUB_API_MAX; i++)
+		available[i] = false;
+
+	for (i = 0; i < USB_MAXINTERFACES; i++) {
+		if ((priv->usb_interface[i].apib->id == USB_API_WINUSBX)
+				&& (priv->usb_interface[i].sub_api != SUB_API_NOTSET))
+			available[priv->usb_interface[i].sub_api] = true;
+	}
+
+	for (i = 0; i < SUB_API_MAX; i++) {
+		if (available[i]) {
+			r = usb_api_backend[USB_API_WINUSBX].reset_device(i, dev_handle);
+			if (r != LIBUSB_SUCCESS)
+				return r;
+		}
+	}
+
+	return LIBUSB_SUCCESS;
+}
+
+static int composite_copy_transfer_data(int sub_api, struct usbi_transfer *itransfer, uint32_t io_size)
+{
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+	struct windows_transfer_priv *transfer_priv = usbi_transfer_get_os_priv(itransfer);
+	struct windows_device_priv *priv = _device_priv(transfer->dev_handle->dev);
+
+	return priv->usb_interface[transfer_priv->interface_number].apib->
+		copy_transfer_data(priv->usb_interface[transfer_priv->interface_number].sub_api, itransfer, io_size);
+}
+
+#endif /* !USE_USBDK */
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/windows_winusb.h b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/windows_winusb.h
new file mode 100644
index 000000000..b7b9cd919
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/os/windows_winusb.h
@@ -0,0 +1,937 @@
+/*
+ * Windows backend for libusb 1.0
+ * Copyright © 2009-2012 Pete Batard <pete@akeo.ie>
+ * With contributions from Michael Plante, Orin Eman et al.
+ * Parts of this code adapted from libusb-win32-v1 by Stephan Meyer
+ * Major code testing contribution by Xiaofan Chen
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#pragma once
+
+#include "windows_common.h"
+#include "windows_nt_common.h"
+
+#if defined(_MSC_VER)
+// disable /W4 MSVC warnings that are benign
+#pragma warning(disable:4100)  // unreferenced formal parameter
+#pragma warning(disable:4127)  // conditional expression is constant
+#pragma warning(disable:4201)  // nameless struct/union
+#pragma warning(disable:4214)  // bit field types other than int
+#pragma warning(disable:4996)  // deprecated API calls
+#pragma warning(disable:28159) // more deprecated API calls
+#endif
+
+// Missing from MSVC6 setupapi.h
+#if !defined(SPDRP_ADDRESS)
+#define SPDRP_ADDRESS		28
+#endif
+#if !defined(SPDRP_INSTALL_STATE)
+#define SPDRP_INSTALL_STATE	34
+#endif
+
+#define MAX_CTRL_BUFFER_LENGTH	4096
+#define MAX_USB_DEVICES		256
+#define MAX_USB_STRING_LENGTH	128
+#define MAX_HID_REPORT_SIZE	1024
+#define MAX_HID_DESCRIPTOR_SIZE	256
+#define MAX_GUID_STRING_LENGTH	40
+#define MAX_PATH_LENGTH		128
+#define MAX_KEY_LENGTH		256
+#define LIST_SEPARATOR		';'
+
+// Handle code for HID interface that have been claimed ("dibs")
+#define INTERFACE_CLAIMED	((HANDLE)(intptr_t)0xD1B5)
+// Additional return code for HID operations that completed synchronously
+#define LIBUSB_COMPLETED	(LIBUSB_SUCCESS + 1)
+
+// http://msdn.microsoft.com/en-us/library/ff545978.aspx
+// http://msdn.microsoft.com/en-us/library/ff545972.aspx
+// http://msdn.microsoft.com/en-us/library/ff545982.aspx
+#if !defined(GUID_DEVINTERFACE_USB_HOST_CONTROLLER)
+const GUID GUID_DEVINTERFACE_USB_HOST_CONTROLLER = { 0x3ABF6F2D, 0x71C4, 0x462A, {0x8A, 0x92, 0x1E, 0x68, 0x61, 0xE6, 0xAF, 0x27} };
+#endif
+#if !defined(GUID_DEVINTERFACE_USB_DEVICE)
+const GUID GUID_DEVINTERFACE_USB_DEVICE = { 0xA5DCBF10, 0x6530, 0x11D2, {0x90, 0x1F, 0x00, 0xC0, 0x4F, 0xB9, 0x51, 0xED} };
+#endif
+#if !defined(GUID_DEVINTERFACE_USB_HUB)
+const GUID GUID_DEVINTERFACE_USB_HUB = { 0xF18A0E88, 0xC30C, 0x11D0, {0x88, 0x15, 0x00, 0xA0, 0xC9, 0x06, 0xBE, 0xD8} };
+#endif
+#if !defined(GUID_DEVINTERFACE_LIBUSB0_FILTER)
+const GUID GUID_DEVINTERFACE_LIBUSB0_FILTER = { 0xF9F3FF14, 0xAE21, 0x48A0, {0x8A, 0x25, 0x80, 0x11, 0xA7, 0xA9, 0x31, 0xD9} };
+#endif
+
+
+/*
+ * Multiple USB API backend support
+ */
+#define USB_API_UNSUPPORTED	0
+#define USB_API_HUB		1
+#define USB_API_COMPOSITE	2
+#define USB_API_WINUSBX		3
+#define USB_API_HID		4
+#define USB_API_MAX		5
+// The following is used to indicate if the HID or composite extra props have already been set.
+#define USB_API_SET		(1 << USB_API_MAX)
+
+// Sub-APIs for WinUSB-like driver APIs (WinUSB, libusbK, libusb-win32 through the libusbK DLL)
+// Must have the same values as the KUSB_DRVID enum from libusbk.h
+#define SUB_API_NOTSET		-1
+#define SUB_API_LIBUSBK		0
+#define SUB_API_LIBUSB0		1
+#define SUB_API_WINUSB		2
+#define SUB_API_MAX		3
+
+#define WINUSBX_DRV_NAMES	{"libusbK", "libusb0", "WinUSB"}
+
+struct windows_usb_api_backend {
+	const uint8_t id;
+	const char *designation;
+	const char **driver_name_list; // Driver name, without .sys, e.g. "usbccgp"
+	const uint8_t nb_driver_names;
+	int (*init)(int sub_api, struct libusb_context *ctx);
+	int (*exit)(int sub_api);
+	int (*open)(int sub_api, struct libusb_device_handle *dev_handle);
+	void (*close)(int sub_api, struct libusb_device_handle *dev_handle);
+	int (*configure_endpoints)(int sub_api, struct libusb_device_handle *dev_handle, int iface);
+	int (*claim_interface)(int sub_api, struct libusb_device_handle *dev_handle, int iface);
+	int (*set_interface_altsetting)(int sub_api, struct libusb_device_handle *dev_handle, int iface, int altsetting);
+	int (*release_interface)(int sub_api, struct libusb_device_handle *dev_handle, int iface);
+	int (*clear_halt)(int sub_api, struct libusb_device_handle *dev_handle, unsigned char endpoint);
+	int (*reset_device)(int sub_api, struct libusb_device_handle *dev_handle);
+	int (*submit_bulk_transfer)(int sub_api, struct usbi_transfer *itransfer);
+	int (*submit_iso_transfer)(int sub_api, struct usbi_transfer *itransfer);
+	int (*submit_control_transfer)(int sub_api, struct usbi_transfer *itransfer);
+	int (*abort_control)(int sub_api, struct usbi_transfer *itransfer);
+	int (*abort_transfers)(int sub_api, struct usbi_transfer *itransfer);
+	int (*copy_transfer_data)(int sub_api, struct usbi_transfer *itransfer, uint32_t io_size);
+};
+
+extern const struct windows_usb_api_backend usb_api_backend[USB_API_MAX];
+
+#define PRINT_UNSUPPORTED_API(fname)				\
+	usbi_dbg("unsupported API call for '"			\
+		#fname "' (unrecognized device driver)");	\
+	return LIBUSB_ERROR_NOT_SUPPORTED;
+
+/*
+ * private structures definition
+ * with inline pseudo constructors/destructors
+ */
+
+// TODO (v2+): move hid desc to libusb.h?
+struct libusb_hid_descriptor {
+	uint8_t bLength;
+	uint8_t bDescriptorType;
+	uint16_t bcdHID;
+	uint8_t bCountryCode;
+	uint8_t bNumDescriptors;
+	uint8_t bClassDescriptorType;
+	uint16_t wClassDescriptorLength;
+};
+
+#define LIBUSB_DT_HID_SIZE		9
+#define HID_MAX_CONFIG_DESC_SIZE (LIBUSB_DT_CONFIG_SIZE + LIBUSB_DT_INTERFACE_SIZE \
+	+ LIBUSB_DT_HID_SIZE + 2 * LIBUSB_DT_ENDPOINT_SIZE)
+#define HID_MAX_REPORT_SIZE		1024
+#define HID_IN_EP			0x81
+#define HID_OUT_EP			0x02
+#define LIBUSB_REQ_RECIPIENT(request_type)	((request_type) & 0x1F)
+#define LIBUSB_REQ_TYPE(request_type)		((request_type) & (0x03 << 5))
+#define LIBUSB_REQ_IN(request_type)		((request_type) & LIBUSB_ENDPOINT_IN)
+#define LIBUSB_REQ_OUT(request_type)		(!LIBUSB_REQ_IN(request_type))
+
+// The following are used for HID reports IOCTLs
+#define HID_CTL_CODE(id) \
+	CTL_CODE (FILE_DEVICE_KEYBOARD, (id), METHOD_NEITHER, FILE_ANY_ACCESS)
+#define HID_BUFFER_CTL_CODE(id) \
+	CTL_CODE (FILE_DEVICE_KEYBOARD, (id), METHOD_BUFFERED, FILE_ANY_ACCESS)
+#define HID_IN_CTL_CODE(id) \
+	CTL_CODE (FILE_DEVICE_KEYBOARD, (id), METHOD_IN_DIRECT, FILE_ANY_ACCESS)
+#define HID_OUT_CTL_CODE(id) \
+	CTL_CODE (FILE_DEVICE_KEYBOARD, (id), METHOD_OUT_DIRECT, FILE_ANY_ACCESS)
+
+#define IOCTL_HID_GET_FEATURE		HID_OUT_CTL_CODE(100)
+#define IOCTL_HID_GET_INPUT_REPORT	HID_OUT_CTL_CODE(104)
+#define IOCTL_HID_SET_FEATURE		HID_IN_CTL_CODE(100)
+#define IOCTL_HID_SET_OUTPUT_REPORT	HID_IN_CTL_CODE(101)
+
+enum libusb_hid_request_type {
+	HID_REQ_GET_REPORT = 0x01,
+	HID_REQ_GET_IDLE = 0x02,
+	HID_REQ_GET_PROTOCOL = 0x03,
+	HID_REQ_SET_REPORT = 0x09,
+	HID_REQ_SET_IDLE = 0x0A,
+	HID_REQ_SET_PROTOCOL = 0x0B
+};
+
+enum libusb_hid_report_type {
+	HID_REPORT_TYPE_INPUT = 0x01,
+	HID_REPORT_TYPE_OUTPUT = 0x02,
+	HID_REPORT_TYPE_FEATURE = 0x03
+};
+
+struct hid_device_priv {
+	uint16_t vid;
+	uint16_t pid;
+	uint8_t config;
+	uint8_t nb_interfaces;
+	bool uses_report_ids[3]; // input, ouptput, feature
+	uint16_t input_report_size;
+	uint16_t output_report_size;
+	uint16_t feature_report_size;
+	WCHAR string[3][MAX_USB_STRING_LENGTH];
+	uint8_t string_index[3]; // man, prod, ser
+};
+
+struct windows_device_priv {
+	uint8_t depth; // distance to HCD
+	uint8_t port;  // port number on the hub
+	uint8_t active_config;
+	struct windows_usb_api_backend const *apib;
+	char *path;  // device interface path
+	int sub_api; // for WinUSB-like APIs
+	struct {
+		char *path; // each interface needs a device interface path,
+		struct windows_usb_api_backend const *apib; // an API backend (multiple drivers support),
+		int sub_api;
+		int8_t nb_endpoints; // and a set of endpoint addresses (USB_MAXENDPOINTS)
+		uint8_t *endpoint;
+		bool restricted_functionality;  // indicates if the interface functionality is restricted
+                                                // by Windows (eg. HID keyboards or mice cannot do R/W)
+	} usb_interface[USB_MAXINTERFACES];
+	struct hid_device_priv *hid;
+	USB_DEVICE_DESCRIPTOR dev_descriptor;
+	unsigned char **config_descriptor; // list of pointers to the cached config descriptors
+};
+
+static inline struct windows_device_priv *_device_priv(struct libusb_device *dev)
+{
+	return (struct windows_device_priv *)dev->os_priv;
+}
+
+static inline struct windows_device_priv *windows_device_priv_init(struct libusb_device *dev)
+{
+	struct windows_device_priv *p = _device_priv(dev);
+	int i;
+
+	p->apib = &usb_api_backend[USB_API_UNSUPPORTED];
+	p->sub_api = SUB_API_NOTSET;
+	for (i = 0; i < USB_MAXINTERFACES; i++) {
+		p->usb_interface[i].apib = &usb_api_backend[USB_API_UNSUPPORTED];
+		p->usb_interface[i].sub_api = SUB_API_NOTSET;
+	}
+
+	return p;
+}
+
+static inline void windows_device_priv_release(struct libusb_device *dev)
+{
+	struct windows_device_priv *p = _device_priv(dev);
+	int i;
+
+	free(p->path);
+	if ((dev->num_configurations > 0) && (p->config_descriptor != NULL)) {
+		for (i = 0; i < dev->num_configurations; i++)
+			free(p->config_descriptor[i]);
+	}
+	free(p->config_descriptor);
+	free(p->hid);
+	for (i = 0; i < USB_MAXINTERFACES; i++) {
+		free(p->usb_interface[i].path);
+		free(p->usb_interface[i].endpoint);
+	}
+}
+
+struct interface_handle_t {
+	HANDLE dev_handle; // WinUSB needs an extra handle for the file
+	HANDLE api_handle; // used by the API to communicate with the device
+};
+
+struct windows_device_handle_priv {
+	int active_interface;
+	struct interface_handle_t interface_handle[USB_MAXINTERFACES];
+	int autoclaim_count[USB_MAXINTERFACES]; // For auto-release
+};
+
+static inline struct windows_device_handle_priv *_device_handle_priv(
+	struct libusb_device_handle *handle)
+{
+	return (struct windows_device_handle_priv *)handle->os_priv;
+}
+
+// used for async polling functions
+struct windows_transfer_priv {
+	struct winfd pollable_fd;
+	uint8_t interface_number;
+	uint8_t *hid_buffer; // 1 byte extended data buffer, required for HID
+	uint8_t *hid_dest;   // transfer buffer destination, required for HID
+	size_t hid_expected_size;
+};
+
+// used to match a device driver (including filter drivers) against a supported API
+struct driver_lookup {
+	char list[MAX_KEY_LENGTH + 1]; // REG_MULTI_SZ list of services (driver) names
+	const DWORD reg_prop;          // SPDRP registry key to use to retrieve list
+	const char* designation;       // internal designation (for debug output)
+};
+
+/* OLE32 dependency */
+DLL_DECLARE_HANDLE(OLE32);
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, HRESULT, p, CLSIDFromString, (LPCOLESTR, LPCLSID));
+
+/* Kernel32 dependencies */
+DLL_DECLARE_HANDLE(Kernel32);
+/* This call is only available from XP SP2 */
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, BOOL, p, IsWow64Process, (HANDLE, PBOOL));
+
+/* SetupAPI dependencies */
+DLL_DECLARE_HANDLE(SetupAPI);
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, HDEVINFO, p, SetupDiGetClassDevsA, (const GUID*, PCSTR, HWND, DWORD));
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, BOOL, p, SetupDiEnumDeviceInfo, (HDEVINFO, DWORD, PSP_DEVINFO_DATA));
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, BOOL, p, SetupDiEnumDeviceInterfaces, (HDEVINFO, PSP_DEVINFO_DATA,
+			const GUID*, DWORD, PSP_DEVICE_INTERFACE_DATA));
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, BOOL, p, SetupDiGetDeviceInterfaceDetailA, (HDEVINFO, PSP_DEVICE_INTERFACE_DATA,
+			PSP_DEVICE_INTERFACE_DETAIL_DATA_A, DWORD, PDWORD, PSP_DEVINFO_DATA));
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, BOOL, p, SetupDiDestroyDeviceInfoList, (HDEVINFO));
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, HKEY, p, SetupDiOpenDevRegKey, (HDEVINFO, PSP_DEVINFO_DATA, DWORD, DWORD, DWORD, REGSAM));
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, BOOL, p, SetupDiGetDeviceRegistryPropertyA, (HDEVINFO,
+			PSP_DEVINFO_DATA, DWORD, PDWORD, PBYTE, DWORD, PDWORD));
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, HKEY, p, SetupDiOpenDeviceInterfaceRegKey, (HDEVINFO, PSP_DEVICE_INTERFACE_DATA, DWORD, DWORD));
+
+/* AdvAPI32 dependencies */
+DLL_DECLARE_HANDLE(AdvAPI32);
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, LONG, p, RegQueryValueExW, (HKEY, LPCWSTR, LPDWORD, LPDWORD, LPBYTE, LPDWORD));
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, LONG, p, RegCloseKey, (HKEY));
+
+/*
+ * Windows DDK API definitions. Most of it copied from MinGW's includes
+ */
+typedef DWORD DEVNODE, DEVINST;
+typedef DEVNODE *PDEVNODE, *PDEVINST;
+typedef DWORD RETURN_TYPE;
+typedef RETURN_TYPE CONFIGRET;
+
+#define CR_SUCCESS				0x00000000
+#define CR_NO_SUCH_DEVNODE			0x0000000D
+
+#define USB_DEVICE_DESCRIPTOR_TYPE		LIBUSB_DT_DEVICE
+#define USB_CONFIGURATION_DESCRIPTOR_TYPE	LIBUSB_DT_CONFIG
+#define USB_STRING_DESCRIPTOR_TYPE		LIBUSB_DT_STRING
+#define USB_INTERFACE_DESCRIPTOR_TYPE		LIBUSB_DT_INTERFACE
+#define USB_ENDPOINT_DESCRIPTOR_TYPE		LIBUSB_DT_ENDPOINT
+
+#define USB_REQUEST_GET_STATUS			LIBUSB_REQUEST_GET_STATUS
+#define USB_REQUEST_CLEAR_FEATURE		LIBUSB_REQUEST_CLEAR_FEATURE
+#define USB_REQUEST_SET_FEATURE			LIBUSB_REQUEST_SET_FEATURE
+#define USB_REQUEST_SET_ADDRESS			LIBUSB_REQUEST_SET_ADDRESS
+#define USB_REQUEST_GET_DESCRIPTOR		LIBUSB_REQUEST_GET_DESCRIPTOR
+#define USB_REQUEST_SET_DESCRIPTOR		LIBUSB_REQUEST_SET_DESCRIPTOR
+#define USB_REQUEST_GET_CONFIGURATION		LIBUSB_REQUEST_GET_CONFIGURATION
+#define USB_REQUEST_SET_CONFIGURATION		LIBUSB_REQUEST_SET_CONFIGURATION
+#define USB_REQUEST_GET_INTERFACE		LIBUSB_REQUEST_GET_INTERFACE
+#define USB_REQUEST_SET_INTERFACE		LIBUSB_REQUEST_SET_INTERFACE
+#define USB_REQUEST_SYNC_FRAME			LIBUSB_REQUEST_SYNCH_FRAME
+
+#define USB_GET_NODE_INFORMATION		258
+#define USB_GET_DESCRIPTOR_FROM_NODE_CONNECTION	260
+#define USB_GET_NODE_CONNECTION_NAME		261
+#define USB_GET_HUB_CAPABILITIES		271
+#if !defined(USB_GET_NODE_CONNECTION_INFORMATION_EX)
+#define USB_GET_NODE_CONNECTION_INFORMATION_EX	274
+#endif
+#if !defined(USB_GET_HUB_CAPABILITIES_EX)
+#define USB_GET_HUB_CAPABILITIES_EX		276
+#endif
+#if !defined(USB_GET_NODE_CONNECTION_INFORMATION_EX_V2)
+#define USB_GET_NODE_CONNECTION_INFORMATION_EX_V2	279
+#endif
+
+#ifndef METHOD_BUFFERED
+#define METHOD_BUFFERED				0
+#endif
+#ifndef FILE_ANY_ACCESS
+#define FILE_ANY_ACCESS				0x00000000
+#endif
+#ifndef FILE_DEVICE_UNKNOWN
+#define FILE_DEVICE_UNKNOWN			0x00000022
+#endif
+#ifndef FILE_DEVICE_USB
+#define FILE_DEVICE_USB				FILE_DEVICE_UNKNOWN
+#endif
+
+#ifndef CTL_CODE
+#define CTL_CODE(DeviceType, Function, Method, Access) \
+	(((DeviceType) << 16) | ((Access) << 14) | ((Function) << 2) | (Method))
+#endif
+
+typedef enum USB_CONNECTION_STATUS {
+	NoDeviceConnected,
+	DeviceConnected,
+	DeviceFailedEnumeration,
+	DeviceGeneralFailure,
+	DeviceCausedOvercurrent,
+	DeviceNotEnoughPower,
+	DeviceNotEnoughBandwidth,
+	DeviceHubNestedTooDeeply,
+	DeviceInLegacyHub
+} USB_CONNECTION_STATUS, *PUSB_CONNECTION_STATUS;
+
+typedef enum USB_HUB_NODE {
+	UsbHub,
+	UsbMIParent
+} USB_HUB_NODE;
+
+/* Cfgmgr32.dll interface */
+DLL_DECLARE_HANDLE(Cfgmgr32);
+DLL_DECLARE_FUNC(WINAPI, CONFIGRET, CM_Get_Parent, (PDEVINST, DEVINST, ULONG));
+DLL_DECLARE_FUNC(WINAPI, CONFIGRET, CM_Get_Child, (PDEVINST, DEVINST, ULONG));
+DLL_DECLARE_FUNC(WINAPI, CONFIGRET, CM_Get_Sibling, (PDEVINST, DEVINST, ULONG));
+DLL_DECLARE_FUNC(WINAPI, CONFIGRET, CM_Get_Device_IDA, (DEVINST, PCHAR, ULONG, ULONG));
+
+#define IOCTL_USB_GET_HUB_CAPABILITIES_EX \
+	CTL_CODE( FILE_DEVICE_USB, USB_GET_HUB_CAPABILITIES_EX, METHOD_BUFFERED, FILE_ANY_ACCESS)
+
+#define IOCTL_USB_GET_HUB_CAPABILITIES \
+	CTL_CODE(FILE_DEVICE_USB, USB_GET_HUB_CAPABILITIES, METHOD_BUFFERED, FILE_ANY_ACCESS)
+
+#define IOCTL_USB_GET_DESCRIPTOR_FROM_NODE_CONNECTION \
+	CTL_CODE(FILE_DEVICE_USB, USB_GET_DESCRIPTOR_FROM_NODE_CONNECTION, METHOD_BUFFERED, FILE_ANY_ACCESS)
+
+#define IOCTL_USB_GET_ROOT_HUB_NAME \
+	CTL_CODE(FILE_DEVICE_USB, HCD_GET_ROOT_HUB_NAME, METHOD_BUFFERED, FILE_ANY_ACCESS)
+
+#define IOCTL_USB_GET_NODE_INFORMATION \
+	CTL_CODE(FILE_DEVICE_USB, USB_GET_NODE_INFORMATION, METHOD_BUFFERED, FILE_ANY_ACCESS)
+
+#define IOCTL_USB_GET_NODE_CONNECTION_INFORMATION_EX \
+	CTL_CODE(FILE_DEVICE_USB, USB_GET_NODE_CONNECTION_INFORMATION_EX, METHOD_BUFFERED, FILE_ANY_ACCESS)
+
+#define IOCTL_USB_GET_NODE_CONNECTION_INFORMATION_EX_V2 \
+	CTL_CODE(FILE_DEVICE_USB, USB_GET_NODE_CONNECTION_INFORMATION_EX_V2, METHOD_BUFFERED, FILE_ANY_ACCESS)
+
+#define IOCTL_USB_GET_NODE_CONNECTION_ATTRIBUTES \
+	CTL_CODE(FILE_DEVICE_USB, USB_GET_NODE_CONNECTION_ATTRIBUTES, METHOD_BUFFERED, FILE_ANY_ACCESS)
+
+#define IOCTL_USB_GET_NODE_CONNECTION_NAME \
+	CTL_CODE(FILE_DEVICE_USB, USB_GET_NODE_CONNECTION_NAME, METHOD_BUFFERED, FILE_ANY_ACCESS)
+
+// Most of the structures below need to be packed
+#pragma pack(push, 1)
+
+typedef struct USB_INTERFACE_DESCRIPTOR {
+	UCHAR bLength;
+	UCHAR bDescriptorType;
+	UCHAR bInterfaceNumber;
+	UCHAR bAlternateSetting;
+	UCHAR bNumEndpoints;
+	UCHAR bInterfaceClass;
+	UCHAR bInterfaceSubClass;
+	UCHAR bInterfaceProtocol;
+	UCHAR iInterface;
+} USB_INTERFACE_DESCRIPTOR, *PUSB_INTERFACE_DESCRIPTOR;
+
+typedef struct USB_CONFIGURATION_DESCRIPTOR_SHORT {
+	struct {
+		ULONG ConnectionIndex;
+		struct {
+			UCHAR bmRequest;
+			UCHAR bRequest;
+			USHORT wValue;
+			USHORT wIndex;
+			USHORT wLength;
+		} SetupPacket;
+	} req;
+	USB_CONFIGURATION_DESCRIPTOR data;
+} USB_CONFIGURATION_DESCRIPTOR_SHORT;
+
+typedef struct USB_ENDPOINT_DESCRIPTOR {
+	UCHAR bLength;
+	UCHAR bDescriptorType;
+	UCHAR bEndpointAddress;
+	UCHAR bmAttributes;
+	USHORT wMaxPacketSize;
+	UCHAR bInterval;
+} USB_ENDPOINT_DESCRIPTOR, *PUSB_ENDPOINT_DESCRIPTOR;
+
+typedef struct USB_DESCRIPTOR_REQUEST {
+	ULONG ConnectionIndex;
+	struct {
+		UCHAR bmRequest;
+		UCHAR bRequest;
+		USHORT wValue;
+		USHORT wIndex;
+		USHORT wLength;
+	} SetupPacket;
+//	UCHAR Data[0];
+} USB_DESCRIPTOR_REQUEST, *PUSB_DESCRIPTOR_REQUEST;
+
+typedef struct USB_HUB_DESCRIPTOR {
+	UCHAR bDescriptorLength;
+	UCHAR bDescriptorType;
+	UCHAR bNumberOfPorts;
+	USHORT wHubCharacteristics;
+	UCHAR bPowerOnToPowerGood;
+	UCHAR bHubControlCurrent;
+	UCHAR bRemoveAndPowerMask[64];
+} USB_HUB_DESCRIPTOR, *PUSB_HUB_DESCRIPTOR;
+
+typedef struct USB_ROOT_HUB_NAME {
+	ULONG ActualLength;
+	WCHAR RootHubName[1];
+} USB_ROOT_HUB_NAME, *PUSB_ROOT_HUB_NAME;
+
+typedef struct USB_ROOT_HUB_NAME_FIXED {
+	ULONG ActualLength;
+	WCHAR RootHubName[MAX_PATH_LENGTH];
+} USB_ROOT_HUB_NAME_FIXED;
+
+typedef struct USB_NODE_CONNECTION_NAME {
+	ULONG ConnectionIndex;
+	ULONG ActualLength;
+	WCHAR NodeName[1];
+} USB_NODE_CONNECTION_NAME, *PUSB_NODE_CONNECTION_NAME;
+
+typedef struct USB_NODE_CONNECTION_NAME_FIXED {
+	ULONG ConnectionIndex;
+	ULONG ActualLength;
+	WCHAR NodeName[MAX_PATH_LENGTH];
+} USB_NODE_CONNECTION_NAME_FIXED;
+
+typedef struct USB_HUB_NAME_FIXED {
+	union {
+		USB_ROOT_HUB_NAME_FIXED root;
+		USB_NODE_CONNECTION_NAME_FIXED node;
+	} u;
+} USB_HUB_NAME_FIXED;
+
+typedef struct USB_HUB_INFORMATION {
+	USB_HUB_DESCRIPTOR HubDescriptor;
+	BOOLEAN HubIsBusPowered;
+} USB_HUB_INFORMATION, *PUSB_HUB_INFORMATION;
+
+typedef struct USB_MI_PARENT_INFORMATION {
+	ULONG NumberOfInterfaces;
+} USB_MI_PARENT_INFORMATION, *PUSB_MI_PARENT_INFORMATION;
+
+typedef struct USB_NODE_INFORMATION {
+	USB_HUB_NODE NodeType;
+	union {
+		USB_HUB_INFORMATION HubInformation;
+		USB_MI_PARENT_INFORMATION MiParentInformation;
+	} u;
+} USB_NODE_INFORMATION, *PUSB_NODE_INFORMATION;
+
+typedef struct USB_PIPE_INFO {
+	USB_ENDPOINT_DESCRIPTOR EndpointDescriptor;
+	ULONG ScheduleOffset;
+} USB_PIPE_INFO, *PUSB_PIPE_INFO;
+
+typedef struct USB_NODE_CONNECTION_INFORMATION_EX {
+	ULONG ConnectionIndex;
+	USB_DEVICE_DESCRIPTOR DeviceDescriptor;
+	UCHAR CurrentConfigurationValue;
+	UCHAR Speed;
+	BOOLEAN DeviceIsHub;
+	USHORT DeviceAddress;
+	ULONG NumberOfOpenPipes;
+	USB_CONNECTION_STATUS ConnectionStatus;
+//	USB_PIPE_INFO PipeList[0];
+} USB_NODE_CONNECTION_INFORMATION_EX, *PUSB_NODE_CONNECTION_INFORMATION_EX;
+
+typedef union _USB_PROTOCOLS {
+	ULONG ul;
+	struct {
+		ULONG Usb110:1;
+		ULONG Usb200:1;
+		ULONG Usb300:1;
+		ULONG ReservedMBZ:29;
+	};
+} USB_PROTOCOLS, *PUSB_PROTOCOLS;
+
+typedef union _USB_NODE_CONNECTION_INFORMATION_EX_V2_FLAGS {
+	ULONG ul;
+	struct {
+		ULONG DeviceIsOperatingAtSuperSpeedOrHigher:1;
+		ULONG DeviceIsSuperSpeedCapableOrHigher:1;
+		ULONG ReservedMBZ:30;
+	};
+} USB_NODE_CONNECTION_INFORMATION_EX_V2_FLAGS, *PUSB_NODE_CONNECTION_INFORMATION_EX_V2_FLAGS;
+
+typedef struct _USB_NODE_CONNECTION_INFORMATION_EX_V2 {
+	ULONG ConnectionIndex;
+	ULONG Length;
+	USB_PROTOCOLS SupportedUsbProtocols;
+	USB_NODE_CONNECTION_INFORMATION_EX_V2_FLAGS Flags;
+} USB_NODE_CONNECTION_INFORMATION_EX_V2, *PUSB_NODE_CONNECTION_INFORMATION_EX_V2;
+
+typedef struct USB_HUB_CAP_FLAGS {
+	ULONG HubIsHighSpeedCapable:1;
+	ULONG HubIsHighSpeed:1;
+	ULONG HubIsMultiTtCapable:1;
+	ULONG HubIsMultiTt:1;
+	ULONG HubIsRoot:1;
+	ULONG HubIsArmedWakeOnConnect:1;
+	ULONG ReservedMBZ:26;
+} USB_HUB_CAP_FLAGS, *PUSB_HUB_CAP_FLAGS;
+
+typedef struct USB_HUB_CAPABILITIES {
+	ULONG HubIs2xCapable:1;
+} USB_HUB_CAPABILITIES, *PUSB_HUB_CAPABILITIES;
+
+typedef struct USB_HUB_CAPABILITIES_EX {
+	USB_HUB_CAP_FLAGS CapabilityFlags;
+} USB_HUB_CAPABILITIES_EX, *PUSB_HUB_CAPABILITIES_EX;
+
+#pragma pack(pop)
+
+/* winusb.dll interface */
+
+#define SHORT_PACKET_TERMINATE	0x01
+#define AUTO_CLEAR_STALL	0x02
+#define PIPE_TRANSFER_TIMEOUT	0x03
+#define IGNORE_SHORT_PACKETS	0x04
+#define ALLOW_PARTIAL_READS	0x05
+#define AUTO_FLUSH		0x06
+#define RAW_IO			0x07
+#define MAXIMUM_TRANSFER_SIZE	0x08
+#define AUTO_SUSPEND		0x81
+#define SUSPEND_DELAY		0x83
+#define DEVICE_SPEED		0x01
+#define LowSpeed		0x01
+#define FullSpeed		0x02
+#define HighSpeed		0x03
+
+typedef enum USBD_PIPE_TYPE {
+	UsbdPipeTypeControl,
+	UsbdPipeTypeIsochronous,
+	UsbdPipeTypeBulk,
+	UsbdPipeTypeInterrupt
+} USBD_PIPE_TYPE;
+
+typedef struct {
+	USBD_PIPE_TYPE PipeType;
+	UCHAR PipeId;
+	USHORT MaximumPacketSize;
+	UCHAR Interval;
+} WINUSB_PIPE_INFORMATION, *PWINUSB_PIPE_INFORMATION;
+
+#pragma pack(1)
+typedef struct {
+	UCHAR request_type;
+	UCHAR request;
+	USHORT value;
+	USHORT index;
+	USHORT length;
+} WINUSB_SETUP_PACKET, *PWINUSB_SETUP_PACKET;
+#pragma pack()
+
+typedef void *WINUSB_INTERFACE_HANDLE, *PWINUSB_INTERFACE_HANDLE;
+
+typedef BOOL (WINAPI *WinUsb_AbortPipe_t)(
+	WINUSB_INTERFACE_HANDLE InterfaceHandle,
+	UCHAR PipeID
+);
+typedef BOOL (WINAPI *WinUsb_ControlTransfer_t)(
+	WINUSB_INTERFACE_HANDLE InterfaceHandle,
+	WINUSB_SETUP_PACKET SetupPacket,
+	PUCHAR Buffer,
+	ULONG BufferLength,
+	PULONG LengthTransferred,
+	LPOVERLAPPED Overlapped
+);
+typedef BOOL (WINAPI *WinUsb_FlushPipe_t)(
+	WINUSB_INTERFACE_HANDLE InterfaceHandle,
+	UCHAR PipeID
+);
+typedef BOOL (WINAPI *WinUsb_Free_t)(
+	WINUSB_INTERFACE_HANDLE InterfaceHandle
+);
+typedef BOOL (WINAPI *WinUsb_GetAssociatedInterface_t)(
+	WINUSB_INTERFACE_HANDLE InterfaceHandle,
+	UCHAR AssociatedInterfaceIndex,
+	PWINUSB_INTERFACE_HANDLE AssociatedInterfaceHandle
+);
+typedef BOOL (WINAPI *WinUsb_GetCurrentAlternateSetting_t)(
+	WINUSB_INTERFACE_HANDLE InterfaceHandle,
+	PUCHAR AlternateSetting
+);
+typedef BOOL (WINAPI *WinUsb_GetDescriptor_t)(
+	WINUSB_INTERFACE_HANDLE InterfaceHandle,
+	UCHAR DescriptorType,
+	UCHAR Index,
+	USHORT LanguageID,
+	PUCHAR Buffer,
+	ULONG BufferLength,
+	PULONG LengthTransferred
+);
+typedef BOOL (WINAPI *WinUsb_GetOverlappedResult_t)(
+	WINUSB_INTERFACE_HANDLE InterfaceHandle,
+	LPOVERLAPPED lpOverlapped,
+	LPDWORD lpNumberOfBytesTransferred,
+	BOOL bWait
+);
+typedef BOOL (WINAPI *WinUsb_GetPipePolicy_t)(
+	WINUSB_INTERFACE_HANDLE InterfaceHandle,
+	UCHAR PipeID,
+	ULONG PolicyType,
+	PULONG ValueLength,
+	PVOID Value
+);
+typedef BOOL (WINAPI *WinUsb_GetPowerPolicy_t)(
+	WINUSB_INTERFACE_HANDLE InterfaceHandle,
+	ULONG PolicyType,
+	PULONG ValueLength,
+	PVOID Value
+);
+typedef BOOL (WINAPI *WinUsb_Initialize_t)(
+	HANDLE DeviceHandle,
+	PWINUSB_INTERFACE_HANDLE InterfaceHandle
+);
+typedef BOOL (WINAPI *WinUsb_QueryDeviceInformation_t)(
+	WINUSB_INTERFACE_HANDLE InterfaceHandle,
+	ULONG InformationType,
+	PULONG BufferLength,
+	PVOID Buffer
+);
+typedef BOOL (WINAPI *WinUsb_QueryInterfaceSettings_t)(
+	WINUSB_INTERFACE_HANDLE InterfaceHandle,
+	UCHAR AlternateSettingNumber,
+	PUSB_INTERFACE_DESCRIPTOR UsbAltInterfaceDescriptor
+);
+typedef BOOL (WINAPI *WinUsb_QueryPipe_t)(
+	WINUSB_INTERFACE_HANDLE InterfaceHandle,
+	UCHAR AlternateInterfaceNumber,
+	UCHAR PipeIndex,
+	PWINUSB_PIPE_INFORMATION PipeInformation
+);
+typedef BOOL (WINAPI *WinUsb_ReadPipe_t)(
+	WINUSB_INTERFACE_HANDLE InterfaceHandle,
+	UCHAR PipeID,
+	PUCHAR Buffer,
+	ULONG BufferLength,
+	PULONG LengthTransferred,
+	LPOVERLAPPED Overlapped
+);
+typedef BOOL (WINAPI *WinUsb_ResetPipe_t)(
+	WINUSB_INTERFACE_HANDLE InterfaceHandle,
+	UCHAR PipeID
+);
+typedef BOOL (WINAPI *WinUsb_SetCurrentAlternateSetting_t)(
+	WINUSB_INTERFACE_HANDLE InterfaceHandle,
+	UCHAR AlternateSetting
+);
+typedef BOOL (WINAPI *WinUsb_SetPipePolicy_t)(
+	WINUSB_INTERFACE_HANDLE InterfaceHandle,
+	UCHAR PipeID,
+	ULONG PolicyType,
+	ULONG ValueLength,
+	PVOID Value
+);
+typedef BOOL (WINAPI *WinUsb_SetPowerPolicy_t)(
+	WINUSB_INTERFACE_HANDLE InterfaceHandle,
+	ULONG PolicyType,
+	ULONG ValueLength,
+	PVOID Value
+);
+typedef BOOL (WINAPI *WinUsb_WritePipe_t)(
+	WINUSB_INTERFACE_HANDLE InterfaceHandle,
+	UCHAR PipeID,
+	PUCHAR Buffer,
+	ULONG BufferLength,
+	PULONG LengthTransferred,
+	LPOVERLAPPED Overlapped
+);
+typedef BOOL (WINAPI *WinUsb_ResetDevice_t)(
+	WINUSB_INTERFACE_HANDLE InterfaceHandle
+);
+
+/* /!\ These must match the ones from the official libusbk.h */
+typedef enum _KUSB_FNID {
+	KUSB_FNID_Init,
+	KUSB_FNID_Free,
+	KUSB_FNID_ClaimInterface,
+	KUSB_FNID_ReleaseInterface,
+	KUSB_FNID_SetAltInterface,
+	KUSB_FNID_GetAltInterface,
+	KUSB_FNID_GetDescriptor,
+	KUSB_FNID_ControlTransfer,
+	KUSB_FNID_SetPowerPolicy,
+	KUSB_FNID_GetPowerPolicy,
+	KUSB_FNID_SetConfiguration,
+	KUSB_FNID_GetConfiguration,
+	KUSB_FNID_ResetDevice,
+	KUSB_FNID_Initialize,
+	KUSB_FNID_SelectInterface,
+	KUSB_FNID_GetAssociatedInterface,
+	KUSB_FNID_Clone,
+	KUSB_FNID_QueryInterfaceSettings,
+	KUSB_FNID_QueryDeviceInformation,
+	KUSB_FNID_SetCurrentAlternateSetting,
+	KUSB_FNID_GetCurrentAlternateSetting,
+	KUSB_FNID_QueryPipe,
+	KUSB_FNID_SetPipePolicy,
+	KUSB_FNID_GetPipePolicy,
+	KUSB_FNID_ReadPipe,
+	KUSB_FNID_WritePipe,
+	KUSB_FNID_ResetPipe,
+	KUSB_FNID_AbortPipe,
+	KUSB_FNID_FlushPipe,
+	KUSB_FNID_IsoReadPipe,
+	KUSB_FNID_IsoWritePipe,
+	KUSB_FNID_GetCurrentFrameNumber,
+	KUSB_FNID_GetOverlappedResult,
+	KUSB_FNID_GetProperty,
+	KUSB_FNID_COUNT,
+} KUSB_FNID;
+
+typedef struct _KLIB_VERSION {
+	INT Major;
+	INT Minor;
+	INT Micro;
+	INT Nano;
+} KLIB_VERSION;
+typedef KLIB_VERSION* PKLIB_VERSION;
+
+typedef BOOL (WINAPI *LibK_GetProcAddress_t)(
+	PVOID *ProcAddress,
+	ULONG DriverID,
+	ULONG FunctionID
+);
+
+typedef VOID (WINAPI *LibK_GetVersion_t)(
+	PKLIB_VERSION Version
+);
+
+struct winusb_interface {
+	bool initialized;
+	WinUsb_AbortPipe_t AbortPipe;
+	WinUsb_ControlTransfer_t ControlTransfer;
+	WinUsb_FlushPipe_t FlushPipe;
+	WinUsb_Free_t Free;
+	WinUsb_GetAssociatedInterface_t GetAssociatedInterface;
+	WinUsb_GetCurrentAlternateSetting_t GetCurrentAlternateSetting;
+	WinUsb_GetDescriptor_t GetDescriptor;
+	WinUsb_GetOverlappedResult_t GetOverlappedResult;
+	WinUsb_GetPipePolicy_t GetPipePolicy;
+	WinUsb_GetPowerPolicy_t GetPowerPolicy;
+	WinUsb_Initialize_t Initialize;
+	WinUsb_QueryDeviceInformation_t QueryDeviceInformation;
+	WinUsb_QueryInterfaceSettings_t QueryInterfaceSettings;
+	WinUsb_QueryPipe_t QueryPipe;
+	WinUsb_ReadPipe_t ReadPipe;
+	WinUsb_ResetPipe_t ResetPipe;
+	WinUsb_SetCurrentAlternateSetting_t SetCurrentAlternateSetting;
+	WinUsb_SetPipePolicy_t SetPipePolicy;
+	WinUsb_SetPowerPolicy_t SetPowerPolicy;
+	WinUsb_WritePipe_t WritePipe;
+	WinUsb_ResetDevice_t ResetDevice;
+};
+
+/* hid.dll interface */
+
+#define HIDP_STATUS_SUCCESS	0x110000
+typedef void * PHIDP_PREPARSED_DATA;
+
+#pragma pack(1)
+typedef struct {
+	ULONG Size;
+	USHORT VendorID;
+	USHORT ProductID;
+	USHORT VersionNumber;
+} HIDD_ATTRIBUTES, *PHIDD_ATTRIBUTES;
+#pragma pack()
+
+typedef USHORT USAGE;
+typedef struct {
+	USAGE Usage;
+	USAGE UsagePage;
+	USHORT InputReportByteLength;
+	USHORT OutputReportByteLength;
+	USHORT FeatureReportByteLength;
+	USHORT Reserved[17];
+	USHORT NumberLinkCollectionNodes;
+	USHORT NumberInputButtonCaps;
+	USHORT NumberInputValueCaps;
+	USHORT NumberInputDataIndices;
+	USHORT NumberOutputButtonCaps;
+	USHORT NumberOutputValueCaps;
+	USHORT NumberOutputDataIndices;
+	USHORT NumberFeatureButtonCaps;
+	USHORT NumberFeatureValueCaps;
+	USHORT NumberFeatureDataIndices;
+} HIDP_CAPS, *PHIDP_CAPS;
+
+typedef enum _HIDP_REPORT_TYPE {
+	HidP_Input,
+	HidP_Output,
+	HidP_Feature
+} HIDP_REPORT_TYPE;
+
+typedef struct _HIDP_VALUE_CAPS {
+	USAGE UsagePage;
+	UCHAR ReportID;
+	BOOLEAN IsAlias;
+	USHORT BitField;
+	USHORT LinkCollection;
+	USAGE LinkUsage;
+	USAGE LinkUsagePage;
+	BOOLEAN IsRange;
+	BOOLEAN IsStringRange;
+	BOOLEAN IsDesignatorRange;
+	BOOLEAN IsAbsolute;
+	BOOLEAN HasNull;
+	UCHAR Reserved;
+	USHORT BitSize;
+	USHORT ReportCount;
+	USHORT Reserved2[5];
+	ULONG UnitsExp;
+	ULONG Units;
+	LONG LogicalMin, LogicalMax;
+	LONG PhysicalMin, PhysicalMax;
+	union {
+		struct {
+			USAGE UsageMin, UsageMax;
+			USHORT StringMin, StringMax;
+			USHORT DesignatorMin, DesignatorMax;
+			USHORT DataIndexMin, DataIndexMax;
+		} Range;
+		struct {
+			USAGE Usage, Reserved1;
+			USHORT StringIndex, Reserved2;
+			USHORT DesignatorIndex, Reserved3;
+			USHORT DataIndex, Reserved4;
+		} NotRange;
+	} u;
+} HIDP_VALUE_CAPS, *PHIDP_VALUE_CAPS;
+
+DLL_DECLARE_HANDLE(hid);
+DLL_DECLARE_FUNC(WINAPI, BOOL, HidD_GetAttributes, (HANDLE, PHIDD_ATTRIBUTES));
+DLL_DECLARE_FUNC(WINAPI, VOID, HidD_GetHidGuid, (LPGUID));
+DLL_DECLARE_FUNC(WINAPI, BOOL, HidD_GetPreparsedData, (HANDLE, PHIDP_PREPARSED_DATA *));
+DLL_DECLARE_FUNC(WINAPI, BOOL, HidD_FreePreparsedData, (PHIDP_PREPARSED_DATA));
+DLL_DECLARE_FUNC(WINAPI, BOOL, HidD_GetManufacturerString, (HANDLE, PVOID, ULONG));
+DLL_DECLARE_FUNC(WINAPI, BOOL, HidD_GetProductString, (HANDLE, PVOID, ULONG));
+DLL_DECLARE_FUNC(WINAPI, BOOL, HidD_GetSerialNumberString, (HANDLE, PVOID, ULONG));
+DLL_DECLARE_FUNC(WINAPI, LONG, HidP_GetCaps, (PHIDP_PREPARSED_DATA, PHIDP_CAPS));
+DLL_DECLARE_FUNC(WINAPI, BOOL, HidD_SetNumInputBuffers, (HANDLE, ULONG));
+DLL_DECLARE_FUNC(WINAPI, BOOL, HidD_SetFeature, (HANDLE, PVOID, ULONG));
+DLL_DECLARE_FUNC(WINAPI, BOOL, HidD_GetFeature, (HANDLE, PVOID, ULONG));
+DLL_DECLARE_FUNC(WINAPI, BOOL, HidD_GetPhysicalDescriptor, (HANDLE, PVOID, ULONG));
+DLL_DECLARE_FUNC(WINAPI, BOOL, HidD_GetInputReport, (HANDLE, PVOID, ULONG));
+DLL_DECLARE_FUNC(WINAPI, BOOL, HidD_SetOutputReport, (HANDLE, PVOID, ULONG));
+DLL_DECLARE_FUNC(WINAPI, BOOL, HidD_FlushQueue, (HANDLE));
+DLL_DECLARE_FUNC(WINAPI, BOOL, HidP_GetValueCaps, (HIDP_REPORT_TYPE, PHIDP_VALUE_CAPS, PULONG, PHIDP_PREPARSED_DATA));
\ No newline at end of file
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/strerror.c b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/strerror.c
new file mode 100644
index 000000000..d2be0e2a0
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/strerror.c
@@ -0,0 +1,202 @@
+/*
+ * libusb strerror code
+ * Copyright © 2013 Hans de Goede <hdegoede@redhat.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <config.h>
+
+#include <locale.h>
+#include <stdlib.h>
+#include <string.h>
+#if defined(HAVE_STRINGS_H)
+#include <strings.h>
+#endif
+
+#include "libusbi.h"
+
+#if defined(_MSC_VER)
+#define strncasecmp _strnicmp
+#endif
+
+static size_t usbi_locale = 0;
+
+/** \ingroup libusb_misc
+ * How to add a new \ref libusb_strerror() translation:
+ * <ol>
+ * <li> Download the latest \c strerror.c from:<br>
+ *      https://raw.github.com/libusb/libusb/master/libusb/sterror.c </li>
+ * <li> Open the file in an UTF-8 capable editor </li>
+ * <li> Add the 2 letter <a href="http://en.wikipedia.org/wiki/List_of_ISO_639-1_codes">ISO 639-1</a>
+ *      code for your locale at the end of \c usbi_locale_supported[]<br>
+ *    Eg. for Chinese, you would add "zh" so that:
+ *    \code... usbi_locale_supported[] = { "en", "nl", "fr" };\endcode
+ *    becomes:
+ *    \code... usbi_locale_supported[] = { "en", "nl", "fr", "zh" };\endcode </li>
+ * <li> Copy the <tt>{ / * English (en) * / ... }</tt> section and add it at the end of \c usbi_localized_errors<br>
+ *    Eg. for Chinese, the last section of \c usbi_localized_errors could look like:
+ *    \code
+ *     }, { / * Chinese (zh) * /
+ *         "Success",
+ *         ...
+ *         "Other error",
+ *     }
+ * };\endcode </li>
+ * <li> Translate each of the English messages from the section you copied into your language </li>
+ * <li> Save the file (in UTF-8 format) and send it to \c libusb-devel\@lists.sourceforge.net </li>
+ * </ol>
+ */
+
+static const char* usbi_locale_supported[] = { "en", "nl", "fr", "ru" };
+static const char* usbi_localized_errors[ARRAYSIZE(usbi_locale_supported)][LIBUSB_ERROR_COUNT] = {
+	{ /* English (en) */
+		"Success",
+		"Input/Output Error",
+		"Invalid parameter",
+		"Access denied (insufficient permissions)",
+		"No such device (it may have been disconnected)",
+		"Entity not found",
+		"Resource busy",
+		"Operation timed out",
+		"Overflow",
+		"Pipe error",
+		"System call interrupted (perhaps due to signal)",
+		"Insufficient memory",
+		"Operation not supported or unimplemented on this platform",
+		"Other error",
+	}, { /* Dutch (nl) */
+		"Gelukt",
+		"Invoer-/uitvoerfout",
+		"Ongeldig argument",
+		"Toegang geweigerd (onvoldoende toegangsrechten)",
+		"Apparaat bestaat niet (verbinding met apparaat verbroken?)",
+		"Niet gevonden",
+		"Apparaat of hulpbron is bezig",
+		"Bewerking verlopen",
+		"Waarde is te groot",
+		"Gebroken pijp",
+		"Onderbroken systeemaanroep",
+		"Onvoldoende geheugen beschikbaar",
+		"Bewerking wordt niet ondersteund",
+		"Andere fout",
+	}, { /* French (fr) */
+		"Succès",
+		"Erreur d'entrée/sortie",
+		"Paramètre invalide",
+		"Accès refusé (permissions insuffisantes)",
+		"Périphérique introuvable (peut-être déconnecté)",
+		"Elément introuvable",
+		"Resource déjà occupée",
+		"Operation expirée",
+		"Débordement",
+		"Erreur de pipe",
+		"Appel système abandonné (peut-être à cause d’un signal)",
+		"Mémoire insuffisante",
+		"Opération non supportée or non implémentée sur cette plateforme",
+		"Autre erreur",
+	}, { /* Russian (ru) */
+		"Успех",
+		"Ошибка ввода/вывода",
+		"Неверный параметр",
+		"Доступ запрещён (не хватает прав)",
+		"Устройство отсутствует (возможно, оно было отсоединено)",
+		"Элемент не найден",
+		"Ресурс занят",
+		"Истекло время ожидания операции",
+		"Переполнение",
+		"Ошибка канала",
+		"Системный вызов прерван (возможно, сигналом)",
+		"Память исчерпана",
+		"Операция не поддерживается данной платформой",
+		"Неизвестная ошибка"
+	}
+};
+
+/** \ingroup libusb_misc
+ * Set the language, and only the language, not the encoding! used for
+ * translatable libusb messages.
+ *
+ * This takes a locale string in the default setlocale format: lang[-region]
+ * or lang[_country_region][.codeset]. Only the lang part of the string is
+ * used, and only 2 letter ISO 639-1 codes are accepted for it, such as "de".
+ * The optional region, country_region or codeset parts are ignored. This
+ * means that functions which return translatable strings will NOT honor the
+ * specified encoding. 
+ * All strings returned are encoded as UTF-8 strings.
+ *
+ * If libusb_setlocale() is not called, all messages will be in English.
+ *
+ * The following functions return translatable strings: libusb_strerror().
+ * Note that the libusb log messages controlled through libusb_set_debug()
+ * are not translated, they are always in English.
+ *
+ * For POSIX UTF-8 environments if you want libusb to follow the standard
+ * locale settings, call libusb_setlocale(setlocale(LC_MESSAGES, NULL)),
+ * after your app has done its locale setup.
+ *
+ * \param locale locale-string in the form of lang[_country_region][.codeset]
+ * or lang[-region], where lang is a 2 letter ISO 639-1 code
+ * \returns LIBUSB_SUCCESS on success
+ * \returns LIBUSB_ERROR_INVALID_PARAM if the locale doesn't meet the requirements
+ * \returns LIBUSB_ERROR_NOT_FOUND if the requested language is not supported
+ * \returns a LIBUSB_ERROR code on other errors
+ */
+
+int API_EXPORTED libusb_setlocale(const char *locale)
+{
+	size_t i;
+
+	if ( (locale == NULL) || (strlen(locale) < 2)
+	  || ((strlen(locale) > 2) && (locale[2] != '-') && (locale[2] != '_') && (locale[2] != '.')) )
+		return LIBUSB_ERROR_INVALID_PARAM;
+
+	for (i=0; i<ARRAYSIZE(usbi_locale_supported); i++) {
+		if (strncasecmp(usbi_locale_supported[i], locale, 2) == 0)
+			break;
+	}
+	if (i >= ARRAYSIZE(usbi_locale_supported)) {
+		return LIBUSB_ERROR_NOT_FOUND;
+	}
+
+	usbi_locale = i;
+
+	return LIBUSB_SUCCESS;
+}
+
+/** \ingroup libusb_misc
+ * Returns a constant string with a short description of the given error code,
+ * this description is intended for displaying to the end user and will be in
+ * the language set by libusb_setlocale().
+ *
+ * The returned string is encoded in UTF-8.
+ *
+ * The messages always start with a capital letter and end without any dot.
+ * The caller must not free() the returned string.
+ *
+ * \param errcode the error code whose description is desired
+ * \returns a short description of the error code in UTF-8 encoding
+ */
+DEFAULT_VISIBILITY const char* LIBUSB_CALL libusb_strerror(enum libusb_error errcode)
+{
+	int errcode_index = -errcode;
+
+	if ((errcode_index < 0) || (errcode_index >= LIBUSB_ERROR_COUNT)) {
+		/* "Other Error", which should always be our last message, is returned */
+		errcode_index = LIBUSB_ERROR_COUNT - 1;
+	}
+
+	return usbi_localized_errors[usbi_locale][errcode_index];
+}
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/sync.c b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/sync.c
new file mode 100644
index 000000000..a609f65f4
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/sync.c
@@ -0,0 +1,327 @@
+/*
+ * Synchronous I/O functions for libusb
+ * Copyright © 2007-2008 Daniel Drake <dsd@gentoo.org>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <config.h>
+
+#include <errno.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "libusbi.h"
+
+/**
+ * @defgroup libusb_syncio Synchronous device I/O
+ *
+ * This page documents libusb's synchronous (blocking) API for USB device I/O.
+ * This interface is easy to use but has some limitations. More advanced users
+ * may wish to consider using the \ref libusb_asyncio "asynchronous I/O API" instead.
+ */
+
+static void LIBUSB_CALL sync_transfer_cb(struct libusb_transfer *transfer)
+{
+	int *completed = transfer->user_data;
+	*completed = 1;
+	usbi_dbg("actual_length=%d", transfer->actual_length);
+	/* caller interprets result and frees transfer */
+}
+
+static void sync_transfer_wait_for_completion(struct libusb_transfer *transfer)
+{
+	int r, *completed = transfer->user_data;
+	struct libusb_context *ctx = HANDLE_CTX(transfer->dev_handle);
+
+	while (!*completed) {
+		r = libusb_handle_events_completed(ctx, completed);
+		if (r < 0) {
+			if (r == LIBUSB_ERROR_INTERRUPTED)
+				continue;
+			usbi_err(ctx, "libusb_handle_events failed: %s, cancelling transfer and retrying",
+				 libusb_error_name(r));
+			libusb_cancel_transfer(transfer);
+			continue;
+		}
+	}
+}
+
+/** \ingroup libusb_syncio
+ * Perform a USB control transfer.
+ *
+ * The direction of the transfer is inferred from the bmRequestType field of
+ * the setup packet.
+ *
+ * The wValue, wIndex and wLength fields values should be given in host-endian
+ * byte order.
+ *
+ * \param dev_handle a handle for the device to communicate with
+ * \param bmRequestType the request type field for the setup packet
+ * \param bRequest the request field for the setup packet
+ * \param wValue the value field for the setup packet
+ * \param wIndex the index field for the setup packet
+ * \param data a suitably-sized data buffer for either input or output
+ * (depending on direction bits within bmRequestType)
+ * \param wLength the length field for the setup packet. The data buffer should
+ * be at least this size.
+ * \param timeout timeout (in millseconds) that this function should wait
+ * before giving up due to no response being received. For an unlimited
+ * timeout, use value 0.
+ * \returns on success, the number of bytes actually transferred
+ * \returns LIBUSB_ERROR_TIMEOUT if the transfer timed out
+ * \returns LIBUSB_ERROR_PIPE if the control request was not supported by the
+ * device
+ * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
+ * \returns LIBUSB_ERROR_BUSY if called from event handling context
+ * \returns LIBUSB_ERROR_INVALID_PARAM if the transfer size is larger than
+ * the operating system and/or hardware can support
+ * \returns another LIBUSB_ERROR code on other failures
+ */
+int API_EXPORTED libusb_control_transfer(libusb_device_handle *dev_handle,
+	uint8_t bmRequestType, uint8_t bRequest, uint16_t wValue, uint16_t wIndex,
+	unsigned char *data, uint16_t wLength, unsigned int timeout)
+{
+	struct libusb_transfer *transfer;
+	unsigned char *buffer;
+	int completed = 0;
+	int r;
+
+	if (usbi_handling_events(HANDLE_CTX(dev_handle)))
+		return LIBUSB_ERROR_BUSY;
+
+	transfer = libusb_alloc_transfer(0);
+	if (!transfer)
+		return LIBUSB_ERROR_NO_MEM;
+
+	buffer = (unsigned char*) malloc(LIBUSB_CONTROL_SETUP_SIZE + wLength);
+	if (!buffer) {
+		libusb_free_transfer(transfer);
+		return LIBUSB_ERROR_NO_MEM;
+	}
+
+	libusb_fill_control_setup(buffer, bmRequestType, bRequest, wValue, wIndex,
+		wLength);
+	if ((bmRequestType & LIBUSB_ENDPOINT_DIR_MASK) == LIBUSB_ENDPOINT_OUT)
+		memcpy(buffer + LIBUSB_CONTROL_SETUP_SIZE, data, wLength);
+
+	libusb_fill_control_transfer(transfer, dev_handle, buffer,
+		sync_transfer_cb, &completed, timeout);
+	transfer->flags = LIBUSB_TRANSFER_FREE_BUFFER;
+	r = libusb_submit_transfer(transfer);
+	if (r < 0) {
+		libusb_free_transfer(transfer);
+		return r;
+	}
+
+	sync_transfer_wait_for_completion(transfer);
+
+	if ((bmRequestType & LIBUSB_ENDPOINT_DIR_MASK) == LIBUSB_ENDPOINT_IN)
+		memcpy(data, libusb_control_transfer_get_data(transfer),
+			transfer->actual_length);
+
+	switch (transfer->status) {
+	case LIBUSB_TRANSFER_COMPLETED:
+		r = transfer->actual_length;
+		break;
+	case LIBUSB_TRANSFER_TIMED_OUT:
+		r = LIBUSB_ERROR_TIMEOUT;
+		break;
+	case LIBUSB_TRANSFER_STALL:
+		r = LIBUSB_ERROR_PIPE;
+		break;
+	case LIBUSB_TRANSFER_NO_DEVICE:
+		r = LIBUSB_ERROR_NO_DEVICE;
+		break;
+	case LIBUSB_TRANSFER_OVERFLOW:
+		r = LIBUSB_ERROR_OVERFLOW;
+		break;
+	case LIBUSB_TRANSFER_ERROR:
+	case LIBUSB_TRANSFER_CANCELLED:
+		r = LIBUSB_ERROR_IO;
+		break;
+	default:
+		usbi_warn(HANDLE_CTX(dev_handle),
+			"unrecognised status code %d", transfer->status);
+		r = LIBUSB_ERROR_OTHER;
+	}
+
+	libusb_free_transfer(transfer);
+	return r;
+}
+
+static int do_sync_bulk_transfer(struct libusb_device_handle *dev_handle,
+	unsigned char endpoint, unsigned char *buffer, int length,
+	int *transferred, unsigned int timeout, unsigned char type)
+{
+	struct libusb_transfer *transfer;
+	int completed = 0;
+	int r;
+
+	if (usbi_handling_events(HANDLE_CTX(dev_handle)))
+		return LIBUSB_ERROR_BUSY;
+
+	transfer = libusb_alloc_transfer(0);
+	if (!transfer)
+		return LIBUSB_ERROR_NO_MEM;
+
+	libusb_fill_bulk_transfer(transfer, dev_handle, endpoint, buffer, length,
+		sync_transfer_cb, &completed, timeout);
+	transfer->type = type;
+
+	r = libusb_submit_transfer(transfer);
+	if (r < 0) {
+		libusb_free_transfer(transfer);
+		return r;
+	}
+
+	sync_transfer_wait_for_completion(transfer);
+
+	if (transferred)
+		*transferred = transfer->actual_length;
+
+	switch (transfer->status) {
+	case LIBUSB_TRANSFER_COMPLETED:
+		r = 0;
+		break;
+	case LIBUSB_TRANSFER_TIMED_OUT:
+		r = LIBUSB_ERROR_TIMEOUT;
+		break;
+	case LIBUSB_TRANSFER_STALL:
+		r = LIBUSB_ERROR_PIPE;
+		break;
+	case LIBUSB_TRANSFER_OVERFLOW:
+		r = LIBUSB_ERROR_OVERFLOW;
+		break;
+	case LIBUSB_TRANSFER_NO_DEVICE:
+		r = LIBUSB_ERROR_NO_DEVICE;
+		break;
+	case LIBUSB_TRANSFER_ERROR:
+	case LIBUSB_TRANSFER_CANCELLED:
+		r = LIBUSB_ERROR_IO;
+		break;
+	default:
+		usbi_warn(HANDLE_CTX(dev_handle),
+			"unrecognised status code %d", transfer->status);
+		r = LIBUSB_ERROR_OTHER;
+	}
+
+	libusb_free_transfer(transfer);
+	return r;
+}
+
+/** \ingroup libusb_syncio
+ * Perform a USB bulk transfer. The direction of the transfer is inferred from
+ * the direction bits of the endpoint address.
+ *
+ * For bulk reads, the <tt>length</tt> field indicates the maximum length of
+ * data you are expecting to receive. If less data arrives than expected,
+ * this function will return that data, so be sure to check the
+ * <tt>transferred</tt> output parameter.
+ *
+ * You should also check the <tt>transferred</tt> parameter for bulk writes.
+ * Not all of the data may have been written.
+ *
+ * Also check <tt>transferred</tt> when dealing with a timeout error code.
+ * libusb may have to split your transfer into a number of chunks to satisfy
+ * underlying O/S requirements, meaning that the timeout may expire after
+ * the first few chunks have completed. libusb is careful not to lose any data
+ * that may have been transferred; do not assume that timeout conditions
+ * indicate a complete lack of I/O.
+ *
+ * \param dev_handle a handle for the device to communicate with
+ * \param endpoint the address of a valid endpoint to communicate with
+ * \param data a suitably-sized data buffer for either input or output
+ * (depending on endpoint)
+ * \param length for bulk writes, the number of bytes from data to be sent. for
+ * bulk reads, the maximum number of bytes to receive into the data buffer.
+ * \param transferred output location for the number of bytes actually
+ * transferred. Since version 1.0.21 (\ref LIBUSB_API_VERSION >= 0x01000105),
+ * it is legal to pass a NULL pointer if you do not wish to receive this
+ * information.
+ * \param timeout timeout (in millseconds) that this function should wait
+ * before giving up due to no response being received. For an unlimited
+ * timeout, use value 0.
+ *
+ * \returns 0 on success (and populates <tt>transferred</tt>)
+ * \returns LIBUSB_ERROR_TIMEOUT if the transfer timed out (and populates
+ * <tt>transferred</tt>)
+ * \returns LIBUSB_ERROR_PIPE if the endpoint halted
+ * \returns LIBUSB_ERROR_OVERFLOW if the device offered more data, see
+ * \ref libusb_packetoverflow
+ * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
+ * \returns LIBUSB_ERROR_BUSY if called from event handling context
+ * \returns another LIBUSB_ERROR code on other failures
+ */
+int API_EXPORTED libusb_bulk_transfer(struct libusb_device_handle *dev_handle,
+	unsigned char endpoint, unsigned char *data, int length, int *transferred,
+	unsigned int timeout)
+{
+	return do_sync_bulk_transfer(dev_handle, endpoint, data, length,
+		transferred, timeout, LIBUSB_TRANSFER_TYPE_BULK);
+}
+
+/** \ingroup libusb_syncio
+ * Perform a USB interrupt transfer. The direction of the transfer is inferred
+ * from the direction bits of the endpoint address.
+ *
+ * For interrupt reads, the <tt>length</tt> field indicates the maximum length
+ * of data you are expecting to receive. If less data arrives than expected,
+ * this function will return that data, so be sure to check the
+ * <tt>transferred</tt> output parameter.
+ *
+ * You should also check the <tt>transferred</tt> parameter for interrupt
+ * writes. Not all of the data may have been written.
+ *
+ * Also check <tt>transferred</tt> when dealing with a timeout error code.
+ * libusb may have to split your transfer into a number of chunks to satisfy
+ * underlying O/S requirements, meaning that the timeout may expire after
+ * the first few chunks have completed. libusb is careful not to lose any data
+ * that may have been transferred; do not assume that timeout conditions
+ * indicate a complete lack of I/O.
+ *
+ * The default endpoint bInterval value is used as the polling interval.
+ *
+ * \param dev_handle a handle for the device to communicate with
+ * \param endpoint the address of a valid endpoint to communicate with
+ * \param data a suitably-sized data buffer for either input or output
+ * (depending on endpoint)
+ * \param length for bulk writes, the number of bytes from data to be sent. for
+ * bulk reads, the maximum number of bytes to receive into the data buffer.
+ * \param transferred output location for the number of bytes actually
+ * transferred. Since version 1.0.21 (\ref LIBUSB_API_VERSION >= 0x01000105),
+ * it is legal to pass a NULL pointer if you do not wish to receive this
+ * information.
+ * \param timeout timeout (in millseconds) that this function should wait
+ * before giving up due to no response being received. For an unlimited
+ * timeout, use value 0.
+ *
+ * \returns 0 on success (and populates <tt>transferred</tt>)
+ * \returns LIBUSB_ERROR_TIMEOUT if the transfer timed out
+ * \returns LIBUSB_ERROR_PIPE if the endpoint halted
+ * \returns LIBUSB_ERROR_OVERFLOW if the device offered more data, see
+ * \ref libusb_packetoverflow
+ * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
+ * \returns LIBUSB_ERROR_BUSY if called from event handling context
+ * \returns another LIBUSB_ERROR code on other error
+ */
+int API_EXPORTED libusb_interrupt_transfer(
+	struct libusb_device_handle *dev_handle, unsigned char endpoint,
+	unsigned char *data, int length, int *transferred, unsigned int timeout)
+{
+	return do_sync_bulk_transfer(dev_handle, endpoint, data, length,
+		transferred, timeout, LIBUSB_TRANSFER_TYPE_INTERRUPT);
+}
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/version.h b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/version.h
new file mode 100644
index 000000000..6ce48a7d0
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/version.h
@@ -0,0 +1,18 @@
+/* This file is parsed by m4 and windres and RC.EXE so please keep it simple. */
+#include "version_nano.h"
+#ifndef LIBUSB_MAJOR
+#define LIBUSB_MAJOR 1
+#endif
+#ifndef LIBUSB_MINOR
+#define LIBUSB_MINOR 0
+#endif
+#ifndef LIBUSB_MICRO
+#define LIBUSB_MICRO 21
+#endif
+#ifndef LIBUSB_NANO
+#define LIBUSB_NANO 0
+#endif
+/* LIBUSB_RC is the release candidate suffix. Should normally be empty. */
+#ifndef LIBUSB_RC
+#define LIBUSB_RC ""
+#endif
diff --git a/vendor/github.com/karalabe/gousb/internal/libusb/libusb/version_nano.h b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/version_nano.h
new file mode 100644
index 000000000..0a5d1c992
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/internal/libusb/libusb/version_nano.h
@@ -0,0 +1 @@
+#define LIBUSB_NANO 11182
diff --git a/vendor/github.com/karalabe/gousb/usb/config.go b/vendor/github.com/karalabe/gousb/usb/config.go
new file mode 100644
index 000000000..840bce63c
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/usb/config.go
@@ -0,0 +1,153 @@
+// Copyright 2013 Google Inc.  All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package usb
+
+/*
+#ifndef OS_WINDOWS
+	#include "os/threads_posix.h"
+#endif
+#include "libusbi.h"
+#include "libusb.h"
+*/
+import "C"
+
+import (
+	"fmt"
+	"reflect"
+	"unsafe"
+)
+
+type EndpointInfo struct {
+	Address       uint8
+	Attributes    uint8
+	MaxPacketSize uint16
+	MaxIsoPacket  uint32
+	PollInterval  uint8
+	RefreshRate   uint8
+	SynchAddress  uint8
+}
+
+func (e EndpointInfo) Number() int {
+	return int(e.Address) & ENDPOINT_NUM_MASK
+}
+
+func (e EndpointInfo) Direction() EndpointDirection {
+	return EndpointDirection(e.Address) & ENDPOINT_DIR_MASK
+}
+
+func (e EndpointInfo) String() string {
+	return fmt.Sprintf("Endpoint %d %-3s %s - %s %s [%d %d]",
+		e.Number(), e.Direction(),
+		TransferType(e.Attributes)&TRANSFER_TYPE_MASK,
+		IsoSyncType(e.Attributes)&ISO_SYNC_TYPE_MASK,
+		IsoUsageType(e.Attributes)&ISO_USAGE_TYPE_MASK,
+		e.MaxPacketSize, e.MaxIsoPacket,
+	)
+}
+
+type InterfaceInfo struct {
+	Number uint8
+	Setups []InterfaceSetup
+}
+
+func (i InterfaceInfo) String() string {
+	return fmt.Sprintf("Interface %02x (%d setups)", i.Number, len(i.Setups))
+}
+
+type InterfaceSetup struct {
+	Number     uint8
+	Alternate  uint8
+	IfClass    uint8
+	IfSubClass uint8
+	IfProtocol uint8
+	Endpoints  []EndpointInfo
+}
+
+func (a InterfaceSetup) String() string {
+	return fmt.Sprintf("Interface %02x Setup %02x", a.Number, a.Alternate)
+}
+
+type ConfigInfo struct {
+	Config     uint8
+	Attributes uint8
+	MaxPower   uint8
+	Interfaces []InterfaceInfo
+}
+
+func (c ConfigInfo) String() string {
+	return fmt.Sprintf("Config %02x", c.Config)
+}
+
+func newConfig(dev *C.libusb_device, cfg *C.struct_libusb_config_descriptor) ConfigInfo {
+	c := ConfigInfo{
+		Config:     uint8(cfg.bConfigurationValue),
+		Attributes: uint8(cfg.bmAttributes),
+		MaxPower:   uint8(cfg.MaxPower),
+	}
+
+	var ifaces []C.struct_libusb_interface
+	*(*reflect.SliceHeader)(unsafe.Pointer(&ifaces)) = reflect.SliceHeader{
+		Data: uintptr(unsafe.Pointer(cfg._interface)),
+		Len:  int(cfg.bNumInterfaces),
+		Cap:  int(cfg.bNumInterfaces),
+	}
+	c.Interfaces = make([]InterfaceInfo, 0, len(ifaces))
+	for _, iface := range ifaces {
+		if iface.num_altsetting == 0 {
+			continue
+		}
+
+		var alts []C.struct_libusb_interface_descriptor
+		*(*reflect.SliceHeader)(unsafe.Pointer(&alts)) = reflect.SliceHeader{
+			Data: uintptr(unsafe.Pointer(iface.altsetting)),
+			Len:  int(iface.num_altsetting),
+			Cap:  int(iface.num_altsetting),
+		}
+		descs := make([]InterfaceSetup, 0, len(alts))
+		for _, alt := range alts {
+			i := InterfaceSetup{
+				Number:     uint8(alt.bInterfaceNumber),
+				Alternate:  uint8(alt.bAlternateSetting),
+				IfClass:    uint8(alt.bInterfaceClass),
+				IfSubClass: uint8(alt.bInterfaceSubClass),
+				IfProtocol: uint8(alt.bInterfaceProtocol),
+			}
+			var ends []C.struct_libusb_endpoint_descriptor
+			*(*reflect.SliceHeader)(unsafe.Pointer(&ends)) = reflect.SliceHeader{
+				Data: uintptr(unsafe.Pointer(alt.endpoint)),
+				Len:  int(alt.bNumEndpoints),
+				Cap:  int(alt.bNumEndpoints),
+			}
+			i.Endpoints = make([]EndpointInfo, 0, len(ends))
+			for _, end := range ends {
+				i.Endpoints = append(i.Endpoints, EndpointInfo{
+					Address:       uint8(end.bEndpointAddress),
+					Attributes:    uint8(end.bmAttributes),
+					MaxPacketSize: uint16(end.wMaxPacketSize),
+					//MaxIsoPacket:  uint32(C.libusb_get_max_iso_packet_size(dev, C.uchar(end.bEndpointAddress))),
+					PollInterval: uint8(end.bInterval),
+					RefreshRate:  uint8(end.bRefresh),
+					SynchAddress: uint8(end.bSynchAddress),
+				})
+			}
+			descs = append(descs, i)
+		}
+		c.Interfaces = append(c.Interfaces, InterfaceInfo{
+			Number: descs[0].Number,
+			Setups: descs,
+		})
+	}
+	return c
+}
diff --git a/vendor/github.com/karalabe/gousb/usb/constants.go b/vendor/github.com/karalabe/gousb/usb/constants.go
new file mode 100644
index 000000000..7f0287d5c
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/usb/constants.go
@@ -0,0 +1,183 @@
+// Copyright 2013 Google Inc.  All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package usb
+
+// #include "libusb.h"
+import "C"
+
+type Class uint8
+
+const (
+	CLASS_PER_INTERFACE Class = C.LIBUSB_CLASS_PER_INTERFACE
+	CLASS_AUDIO         Class = C.LIBUSB_CLASS_AUDIO
+	CLASS_COMM          Class = C.LIBUSB_CLASS_COMM
+	CLASS_HID           Class = C.LIBUSB_CLASS_HID
+	CLASS_PRINTER       Class = C.LIBUSB_CLASS_PRINTER
+	CLASS_PTP           Class = C.LIBUSB_CLASS_PTP
+	CLASS_MASS_STORAGE  Class = C.LIBUSB_CLASS_MASS_STORAGE
+	CLASS_HUB           Class = C.LIBUSB_CLASS_HUB
+	CLASS_DATA          Class = C.LIBUSB_CLASS_DATA
+	CLASS_WIRELESS      Class = C.LIBUSB_CLASS_WIRELESS
+	CLASS_APPLICATION   Class = C.LIBUSB_CLASS_APPLICATION
+	CLASS_VENDOR_SPEC   Class = C.LIBUSB_CLASS_VENDOR_SPEC
+)
+
+var classDescription = map[Class]string{
+	CLASS_PER_INTERFACE: "per-interface",
+	CLASS_AUDIO:         "audio",
+	CLASS_COMM:          "communications",
+	CLASS_HID:           "human interface device",
+	CLASS_PRINTER:       "printer dclass",
+	CLASS_PTP:           "picture transfer protocol",
+	CLASS_MASS_STORAGE:  "mass storage",
+	CLASS_HUB:           "hub",
+	CLASS_DATA:          "data",
+	CLASS_WIRELESS:      "wireless",
+	CLASS_APPLICATION:   "application",
+	CLASS_VENDOR_SPEC:   "vendor-specific",
+}
+
+func (c Class) String() string {
+	return classDescription[c]
+}
+
+type DescriptorType uint8
+
+const (
+	DT_DEVICE    DescriptorType = C.LIBUSB_DT_DEVICE
+	DT_CONFIG    DescriptorType = C.LIBUSB_DT_CONFIG
+	DT_STRING    DescriptorType = C.LIBUSB_DT_STRING
+	DT_INTERFACE DescriptorType = C.LIBUSB_DT_INTERFACE
+	DT_ENDPOINT  DescriptorType = C.LIBUSB_DT_ENDPOINT
+	DT_HID       DescriptorType = C.LIBUSB_DT_HID
+	DT_REPORT    DescriptorType = C.LIBUSB_DT_REPORT
+	DT_PHYSICAL  DescriptorType = C.LIBUSB_DT_PHYSICAL
+	DT_HUB       DescriptorType = C.LIBUSB_DT_HUB
+)
+
+var descriptorTypeDescription = map[DescriptorType]string{
+	DT_DEVICE:    "device",
+	DT_CONFIG:    "configuration",
+	DT_STRING:    "string",
+	DT_INTERFACE: "interface",
+	DT_ENDPOINT:  "endpoint",
+	DT_HID:       "HID",
+	DT_REPORT:    "HID report",
+	DT_PHYSICAL:  "physical",
+	DT_HUB:       "hub",
+}
+
+func (dt DescriptorType) String() string {
+	return descriptorTypeDescription[dt]
+}
+
+type EndpointDirection uint8
+
+const (
+	ENDPOINT_NUM_MASK                   = 0x03
+	ENDPOINT_DIR_IN   EndpointDirection = C.LIBUSB_ENDPOINT_IN
+	ENDPOINT_DIR_OUT  EndpointDirection = C.LIBUSB_ENDPOINT_OUT
+	ENDPOINT_DIR_MASK EndpointDirection = 0x80
+)
+
+var endpointDirectionDescription = map[EndpointDirection]string{
+	ENDPOINT_DIR_IN:  "IN",
+	ENDPOINT_DIR_OUT: "OUT",
+}
+
+func (ed EndpointDirection) String() string {
+	return endpointDirectionDescription[ed]
+}
+
+type TransferType uint8
+
+const (
+	TRANSFER_TYPE_CONTROL     TransferType = C.LIBUSB_TRANSFER_TYPE_CONTROL
+	TRANSFER_TYPE_ISOCHRONOUS TransferType = C.LIBUSB_TRANSFER_TYPE_ISOCHRONOUS
+	TRANSFER_TYPE_BULK        TransferType = C.LIBUSB_TRANSFER_TYPE_BULK
+	TRANSFER_TYPE_INTERRUPT   TransferType = C.LIBUSB_TRANSFER_TYPE_INTERRUPT
+	TRANSFER_TYPE_MASK        TransferType = 0x03
+)
+
+var transferTypeDescription = map[TransferType]string{
+	TRANSFER_TYPE_CONTROL:     "control",
+	TRANSFER_TYPE_ISOCHRONOUS: "isochronous",
+	TRANSFER_TYPE_BULK:        "bulk",
+	TRANSFER_TYPE_INTERRUPT:   "interrupt",
+}
+
+func (tt TransferType) String() string {
+	return transferTypeDescription[tt]
+}
+
+type IsoSyncType uint8
+
+const (
+	ISO_SYNC_TYPE_NONE     IsoSyncType = C.LIBUSB_ISO_SYNC_TYPE_NONE << 2
+	ISO_SYNC_TYPE_ASYNC    IsoSyncType = C.LIBUSB_ISO_SYNC_TYPE_ASYNC << 2
+	ISO_SYNC_TYPE_ADAPTIVE IsoSyncType = C.LIBUSB_ISO_SYNC_TYPE_ADAPTIVE << 2
+	ISO_SYNC_TYPE_SYNC     IsoSyncType = C.LIBUSB_ISO_SYNC_TYPE_SYNC << 2
+	ISO_SYNC_TYPE_MASK     IsoSyncType = 0x0C
+)
+
+var isoSyncTypeDescription = map[IsoSyncType]string{
+	ISO_SYNC_TYPE_NONE:     "unsynchronized",
+	ISO_SYNC_TYPE_ASYNC:    "asynchronous",
+	ISO_SYNC_TYPE_ADAPTIVE: "adaptive",
+	ISO_SYNC_TYPE_SYNC:     "synchronous",
+}
+
+func (ist IsoSyncType) String() string {
+	return isoSyncTypeDescription[ist]
+}
+
+type IsoUsageType uint8
+
+const (
+	ISO_USAGE_TYPE_DATA     IsoUsageType = C.LIBUSB_ISO_USAGE_TYPE_DATA << 4
+	ISO_USAGE_TYPE_FEEDBACK IsoUsageType = C.LIBUSB_ISO_USAGE_TYPE_FEEDBACK << 4
+	ISO_USAGE_TYPE_IMPLICIT IsoUsageType = C.LIBUSB_ISO_USAGE_TYPE_IMPLICIT << 4
+	ISO_USAGE_TYPE_MASK     IsoUsageType = 0x30
+)
+
+var isoUsageTypeDescription = map[IsoUsageType]string{
+	ISO_USAGE_TYPE_DATA:     "data",
+	ISO_USAGE_TYPE_FEEDBACK: "feedback",
+	ISO_USAGE_TYPE_IMPLICIT: "implicit data",
+}
+
+func (iut IsoUsageType) String() string {
+	return isoUsageTypeDescription[iut]
+}
+
+type RequestType uint8
+
+const (
+	REQUEST_TYPE_STANDARD = C.LIBUSB_REQUEST_TYPE_STANDARD
+	REQUEST_TYPE_CLASS    = C.LIBUSB_REQUEST_TYPE_CLASS
+	REQUEST_TYPE_VENDOR   = C.LIBUSB_REQUEST_TYPE_VENDOR
+	REQUEST_TYPE_RESERVED = C.LIBUSB_REQUEST_TYPE_RESERVED
+)
+
+var requestTypeDescription = map[RequestType]string{
+	REQUEST_TYPE_STANDARD: "standard",
+	REQUEST_TYPE_CLASS:    "class",
+	REQUEST_TYPE_VENDOR:   "vendor",
+	REQUEST_TYPE_RESERVED: "reserved",
+}
+
+func (rt RequestType) String() string {
+	return requestTypeDescription[rt]
+}
diff --git a/vendor/github.com/karalabe/gousb/usb/debug.go b/vendor/github.com/karalabe/gousb/usb/debug.go
new file mode 100644
index 000000000..e7de8e522
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/usb/debug.go
@@ -0,0 +1,36 @@
+// Copyright 2013 Google Inc.  All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package usb
+
+// To enable internal debugging:
+//   -ldflags "-X github.com/karalabe/gousb/usb.debugInternal true"
+
+import (
+	"io"
+	"io/ioutil"
+	"log" // TODO(kevlar): make a logger
+	"os"
+)
+
+var debug *log.Logger
+var debugInternal string
+
+func init() {
+	var out io.Writer = ioutil.Discard
+	if debugInternal != "" {
+		out = os.Stderr
+	}
+	debug = log.New(out, "usb", log.LstdFlags|log.Lshortfile)
+}
diff --git a/vendor/github.com/karalabe/gousb/usb/descriptor.go b/vendor/github.com/karalabe/gousb/usb/descriptor.go
new file mode 100644
index 000000000..2551dfc23
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/usb/descriptor.go
@@ -0,0 +1,77 @@
+// Copyright 2013 Google Inc.  All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package usb
+
+/*
+#ifndef OS_WINDOWS
+	#include "os/threads_posix.h"
+#endif
+#include "libusbi.h"
+#include "libusb.h"
+*/
+import "C"
+
+type Descriptor struct {
+	// Bus information
+	Bus     uint8 // The bus on which the device was detected
+	Address uint8 // The address of the device on the bus
+
+	// Version information
+	Spec   BCD // USB Specification Release Number
+	Device BCD // The device version
+
+	// Product information
+	Vendor  ID // The Vendor identifer
+	Product ID // The Product identifier
+
+	// Protocol information
+	Class    uint8 // The class of this device
+	SubClass uint8 // The sub-class (within the class) of this device
+	Protocol uint8 // The protocol (within the sub-class) of this device
+
+	// Configuration information
+	Configs []ConfigInfo
+}
+
+func newDescriptor(dev *C.libusb_device) (*Descriptor, error) {
+	var desc C.struct_libusb_device_descriptor
+	if errno := C.libusb_get_device_descriptor(dev, &desc); errno < 0 {
+		return nil, usbError(errno)
+	}
+
+	// Enumerate configurations
+	var cfgs []ConfigInfo
+	for i := 0; i < int(desc.bNumConfigurations); i++ {
+		var cfg *C.struct_libusb_config_descriptor
+		if errno := C.libusb_get_config_descriptor(dev, C.uint8_t(i), &cfg); errno < 0 {
+			return nil, usbError(errno)
+		}
+		cfgs = append(cfgs, newConfig(dev, cfg))
+		C.libusb_free_config_descriptor(cfg)
+	}
+
+	return &Descriptor{
+		Bus:      uint8(C.libusb_get_bus_number(dev)),
+		Address:  uint8(C.libusb_get_device_address(dev)),
+		Spec:     BCD(desc.bcdUSB),
+		Device:   BCD(desc.bcdDevice),
+		Vendor:   ID(desc.idVendor),
+		Product:  ID(desc.idProduct),
+		Class:    uint8(desc.bDeviceClass),
+		SubClass: uint8(desc.bDeviceSubClass),
+		Protocol: uint8(desc.bDeviceProtocol),
+		Configs:  cfgs,
+	}, nil
+}
diff --git a/vendor/github.com/karalabe/gousb/usb/device.go b/vendor/github.com/karalabe/gousb/usb/device.go
new file mode 100644
index 000000000..b4c4131fa
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/usb/device.go
@@ -0,0 +1,295 @@
+// Copyright 2013 Google Inc.  All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package usb
+
+/*
+#ifndef OS_WINDOWS
+	#include "os/threads_posix.h"
+#endif
+#include "libusbi.h"
+#include "libusb.h"
+*/
+import "C"
+
+import (
+	"fmt"
+	"reflect"
+	"sync"
+	"time"
+	"unsafe"
+)
+
+var DefaultReadTimeout = 1 * time.Second
+var DefaultWriteTimeout = 1 * time.Second
+var DefaultControlTimeout = 250 * time.Millisecond //5 * time.Second
+
+type Device struct {
+	handle *C.libusb_device_handle
+
+	// Embed the device information for easy access
+	*Descriptor
+
+	// Timeouts
+	ReadTimeout    time.Duration
+	WriteTimeout   time.Duration
+	ControlTimeout time.Duration
+
+	// Claimed interfaces
+	lock    *sync.Mutex
+	claimed map[uint8]int
+
+	// Detached kernel interfaces
+	detached map[uint8]int
+}
+
+func newDevice(handle *C.libusb_device_handle, desc *Descriptor) (*Device, error) {
+	ifaces := 0
+	d := &Device{
+		handle:         handle,
+		Descriptor:     desc,
+		ReadTimeout:    DefaultReadTimeout,
+		WriteTimeout:   DefaultWriteTimeout,
+		ControlTimeout: DefaultControlTimeout,
+		lock:           new(sync.Mutex),
+		claimed:        make(map[uint8]int, ifaces),
+		detached:       make(map[uint8]int),
+	}
+
+	if err := d.detachKernelDriver(); err != nil {
+		d.Close()
+		return nil, err
+	}
+
+	return d, nil
+}
+
+// detachKernelDriver detaches any active kernel drivers, if supported by the platform.
+// If there are any errors, like Context.ListDevices, only the final one will be returned.
+func (d *Device) detachKernelDriver() (err error) {
+	for _, cfg := range d.Configs {
+		for _, iface := range cfg.Interfaces {
+			switch activeErr := C.libusb_kernel_driver_active(d.handle, C.int(iface.Number)); activeErr {
+			case C.LIBUSB_ERROR_NOT_SUPPORTED:
+				// no need to do any futher checking, no platform support
+				return
+			case 0:
+				continue
+			case 1:
+				switch detachErr := C.libusb_detach_kernel_driver(d.handle, C.int(iface.Number)); detachErr {
+				case C.LIBUSB_ERROR_NOT_SUPPORTED:
+					// shouldn't ever get here, should be caught by the outer switch
+					return
+				case 0:
+					d.detached[iface.Number]++
+				case C.LIBUSB_ERROR_NOT_FOUND:
+					// this status is returned if libusb's driver is already attached to the device
+					d.detached[iface.Number]++
+				default:
+					err = fmt.Errorf("usb: detach kernel driver: %s", usbError(detachErr))
+				}
+			default:
+				err = fmt.Errorf("usb: active kernel driver check: %s", usbError(activeErr))
+			}
+		}
+	}
+
+	return
+}
+
+// attachKernelDriver re-attaches kernel drivers to any previously detached interfaces, if supported by the platform.
+// If there are any errors, like Context.ListDevices, only the final one will be returned.
+func (d *Device) attachKernelDriver() (err error) {
+	for iface := range d.detached {
+		switch attachErr := C.libusb_attach_kernel_driver(d.handle, C.int(iface)); attachErr {
+		case C.LIBUSB_ERROR_NOT_SUPPORTED:
+			// no need to do any futher checking, no platform support
+			return
+		case 0:
+			continue
+		default:
+			err = fmt.Errorf("usb: attach kernel driver: %s", usbError(attachErr))
+		}
+	}
+
+	return
+}
+
+func (d *Device) Reset() error {
+	if errno := C.libusb_reset_device(d.handle); errno != 0 {
+		return usbError(errno)
+	}
+	return nil
+}
+
+func (d *Device) Control(rType, request uint8, val, idx uint16, data []byte) (int, error) {
+	//log.Printf("control xfer: %d:%d/%d:%d %x", idx, rType, request, val, string(data))
+	dataSlice := (*reflect.SliceHeader)(unsafe.Pointer(&data))
+	n := C.libusb_control_transfer(
+		d.handle,
+		C.uint8_t(rType),
+		C.uint8_t(request),
+		C.uint16_t(val),
+		C.uint16_t(idx),
+		(*C.uchar)(unsafe.Pointer(dataSlice.Data)),
+		C.uint16_t(len(data)),
+		C.uint(d.ControlTimeout/time.Millisecond))
+	if n < 0 {
+		return int(n), usbError(n)
+	}
+	return int(n), nil
+}
+
+// ActiveConfig returns the config id (not the index) of the active configuration.
+// This corresponds to the ConfigInfo.Config field.
+func (d *Device) ActiveConfig() (uint8, error) {
+	var cfg C.int
+	if errno := C.libusb_get_configuration(d.handle, &cfg); errno < 0 {
+		return 0, usbError(errno)
+	}
+	return uint8(cfg), nil
+}
+
+// SetConfig attempts to change the active configuration.
+// The cfg provided is the config id (not the index) of the configuration to set,
+// which corresponds to the ConfigInfo.Config field.
+func (d *Device) SetConfig(cfg uint8) error {
+	if errno := C.libusb_set_configuration(d.handle, C.int(cfg)); errno < 0 {
+		return usbError(errno)
+	}
+	return nil
+}
+
+// Close the device.
+func (d *Device) Close() error {
+	if d.handle == nil {
+		return fmt.Errorf("usb: double close on device")
+	}
+	d.lock.Lock()
+	defer d.lock.Unlock()
+	for iface := range d.claimed {
+		C.libusb_release_interface(d.handle, C.int(iface))
+	}
+	d.attachKernelDriver()
+	C.libusb_close(d.handle)
+	d.handle = nil
+	return nil
+}
+
+func (d *Device) OpenEndpoint(conf, iface, setup, epoint uint8) (Endpoint, error) {
+	end := &endpoint{
+		Device: d,
+	}
+
+	var setAlternate bool
+	for _, c := range d.Configs {
+		if c.Config != conf {
+			continue
+		}
+		debug.Printf("found conf: %#v\n", c)
+		for _, i := range c.Interfaces {
+			if i.Number != iface {
+				continue
+			}
+			debug.Printf("found iface: %#v\n", i)
+			for i, s := range i.Setups {
+				if s.Alternate != setup {
+					continue
+				}
+				setAlternate = i != 0
+
+				debug.Printf("found setup: %#v [default: %v]\n", s, !setAlternate)
+				for _, e := range s.Endpoints {
+					debug.Printf("ep %02x search: %#v\n", epoint, s)
+					if e.Address != epoint {
+						continue
+					}
+					end.InterfaceSetup = s
+					end.EndpointInfo = e
+					switch tt := TransferType(e.Attributes) & TRANSFER_TYPE_MASK; tt {
+					case TRANSFER_TYPE_BULK:
+						end.xfer = bulk_xfer
+					case TRANSFER_TYPE_INTERRUPT:
+						end.xfer = interrupt_xfer
+					case TRANSFER_TYPE_ISOCHRONOUS:
+						end.xfer = isochronous_xfer
+					default:
+						return nil, fmt.Errorf("usb: %s transfer is unsupported", tt)
+					}
+					goto found
+				}
+				return nil, fmt.Errorf("usb: unknown endpoint %02x", epoint)
+			}
+			return nil, fmt.Errorf("usb: unknown setup %02x", setup)
+		}
+		return nil, fmt.Errorf("usb: unknown interface %02x", iface)
+	}
+	return nil, fmt.Errorf("usb: unknown configuration %02x", conf)
+
+found:
+
+	// Set the configuration
+	var activeConf C.int
+	if errno := C.libusb_get_configuration(d.handle, &activeConf); errno < 0 {
+		return nil, fmt.Errorf("usb: getcfg: %s", usbError(errno))
+	}
+	if int(activeConf) != int(conf) {
+		if errno := C.libusb_set_configuration(d.handle, C.int(conf)); errno < 0 {
+			return nil, fmt.Errorf("usb: setcfg: %s", usbError(errno))
+		}
+	}
+
+	// Claim the interface
+	if errno := C.libusb_claim_interface(d.handle, C.int(iface)); errno < 0 {
+		return nil, fmt.Errorf("usb: claim: %s", usbError(errno))
+	}
+
+	// Increment the claim count
+	d.lock.Lock()
+	d.claimed[iface]++
+	d.lock.Unlock() // unlock immediately because the next calls may block
+
+	// Choose the alternate
+	if setAlternate {
+		if errno := C.libusb_set_interface_alt_setting(d.handle, C.int(iface), C.int(setup)); errno < 0 {
+			debug.Printf("altsetting error: %s", usbError(errno))
+			return nil, fmt.Errorf("usb: setalt: %s", usbError(errno))
+		}
+	}
+
+	return end, nil
+}
+
+func (d *Device) GetStringDescriptor(desc_index int) (string, error) {
+
+	// allocate 200-byte array limited the length of string descriptor
+	goBuffer := make([]byte, 200)
+
+	// get string descriptor from libusb. if errno < 0 then there are any errors.
+	// if errno >= 0; it is a length of result string descriptor
+	errno := C.libusb_get_string_descriptor_ascii(
+		d.handle,
+		C.uint8_t(desc_index),
+		(*C.uchar)(unsafe.Pointer(&goBuffer[0])),
+		200)
+
+	// if any errors occur
+	if errno < 0 {
+		return "", fmt.Errorf("usb: getstr: %s", usbError(errno))
+	}
+	// convert slice of byte to string with limited length from errno
+	stringDescriptor := string(goBuffer[:errno])
+
+	return stringDescriptor, nil
+}
diff --git a/vendor/github.com/karalabe/gousb/usb/endpoint.go b/vendor/github.com/karalabe/gousb/usb/endpoint.go
new file mode 100644
index 000000000..12b4ccf95
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/usb/endpoint.go
@@ -0,0 +1,100 @@
+// Copyright 2013 Google Inc.  All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package usb
+
+// #include "libusb.h"
+import "C"
+
+import (
+	"fmt"
+	"reflect"
+	"time"
+	"unsafe"
+)
+
+type Endpoint interface {
+	Read(b []byte) (int, error)
+	Write(b []byte) (int, error)
+	Interface() InterfaceSetup
+	Info() EndpointInfo
+}
+
+type endpoint struct {
+	*Device
+	InterfaceSetup
+	EndpointInfo
+	xfer func(*endpoint, []byte, time.Duration) (int, error)
+}
+
+func (e *endpoint) Read(buf []byte) (int, error) {
+	if EndpointDirection(e.Address)&ENDPOINT_DIR_MASK != ENDPOINT_DIR_IN {
+		return 0, fmt.Errorf("usb: read: not an IN endpoint")
+	}
+
+	return e.xfer(e, buf, e.ReadTimeout)
+}
+
+func (e *endpoint) Write(buf []byte) (int, error) {
+	if EndpointDirection(e.Address)&ENDPOINT_DIR_MASK != ENDPOINT_DIR_OUT {
+		return 0, fmt.Errorf("usb: write: not an OUT endpoint")
+	}
+
+	return e.xfer(e, buf, e.WriteTimeout)
+}
+
+func (e *endpoint) Interface() InterfaceSetup { return e.InterfaceSetup }
+func (e *endpoint) Info() EndpointInfo        { return e.EndpointInfo }
+
+// TODO(kevlar): (*Endpoint).Close
+
+func bulk_xfer(e *endpoint, buf []byte, timeout time.Duration) (int, error) {
+	if len(buf) == 0 {
+		return 0, nil
+	}
+
+	data := (*reflect.SliceHeader)(unsafe.Pointer(&buf)).Data
+
+	var cnt C.int
+	if errno := C.libusb_bulk_transfer(
+		e.handle,
+		C.uchar(e.Address),
+		(*C.uchar)(unsafe.Pointer(data)),
+		C.int(len(buf)),
+		&cnt,
+		C.uint(timeout/time.Millisecond)); errno < 0 {
+		return 0, usbError(errno)
+	}
+	return int(cnt), nil
+}
+
+func interrupt_xfer(e *endpoint, buf []byte, timeout time.Duration) (int, error) {
+	if len(buf) == 0 {
+		return 0, nil
+	}
+
+	data := (*reflect.SliceHeader)(unsafe.Pointer(&buf)).Data
+
+	var cnt C.int
+	if errno := C.libusb_interrupt_transfer(
+		e.handle,
+		C.uchar(e.Address),
+		(*C.uchar)(unsafe.Pointer(data)),
+		C.int(len(buf)),
+		&cnt,
+		C.uint(timeout/time.Millisecond)); errno < 0 {
+		return 0, usbError(errno)
+	}
+	return int(cnt), nil
+}
diff --git a/vendor/github.com/karalabe/gousb/usb/error.go b/vendor/github.com/karalabe/gousb/usb/error.go
new file mode 100644
index 000000000..30d47bce3
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/usb/error.go
@@ -0,0 +1,92 @@
+// Copyright 2013 Google Inc.  All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package usb
+
+import (
+	"fmt"
+)
+
+// #include "libusb.h"
+import "C"
+
+type usbError C.int
+
+func (e usbError) Error() string {
+	return fmt.Sprintf("libusb: %s [code %d]", usbErrorString[e], int(e))
+}
+
+const (
+	SUCCESS             usbError = C.LIBUSB_SUCCESS
+	ERROR_IO            usbError = C.LIBUSB_ERROR_IO
+	ERROR_INVALID_PARAM usbError = C.LIBUSB_ERROR_INVALID_PARAM
+	ERROR_ACCESS        usbError = C.LIBUSB_ERROR_ACCESS
+	ERROR_NO_DEVICE     usbError = C.LIBUSB_ERROR_NO_DEVICE
+	ERROR_NOT_FOUND     usbError = C.LIBUSB_ERROR_NOT_FOUND
+	ERROR_BUSY          usbError = C.LIBUSB_ERROR_BUSY
+	ERROR_TIMEOUT       usbError = C.LIBUSB_ERROR_TIMEOUT
+	ERROR_OVERFLOW      usbError = C.LIBUSB_ERROR_OVERFLOW
+	ERROR_PIPE          usbError = C.LIBUSB_ERROR_PIPE
+	ERROR_INTERRUPTED   usbError = C.LIBUSB_ERROR_INTERRUPTED
+	ERROR_NO_MEM        usbError = C.LIBUSB_ERROR_NO_MEM
+	ERROR_NOT_SUPPORTED usbError = C.LIBUSB_ERROR_NOT_SUPPORTED
+	ERROR_OTHER         usbError = C.LIBUSB_ERROR_OTHER
+)
+
+var usbErrorString = map[usbError]string{
+	C.LIBUSB_SUCCESS:             "success",
+	C.LIBUSB_ERROR_IO:            "i/o error",
+	C.LIBUSB_ERROR_INVALID_PARAM: "invalid param",
+	C.LIBUSB_ERROR_ACCESS:        "bad access",
+	C.LIBUSB_ERROR_NO_DEVICE:     "no device",
+	C.LIBUSB_ERROR_NOT_FOUND:     "not found",
+	C.LIBUSB_ERROR_BUSY:          "device or resource busy",
+	C.LIBUSB_ERROR_TIMEOUT:       "timeout",
+	C.LIBUSB_ERROR_OVERFLOW:      "overflow",
+	C.LIBUSB_ERROR_PIPE:          "pipe error",
+	C.LIBUSB_ERROR_INTERRUPTED:   "interrupted",
+	C.LIBUSB_ERROR_NO_MEM:        "out of memory",
+	C.LIBUSB_ERROR_NOT_SUPPORTED: "not supported",
+	C.LIBUSB_ERROR_OTHER:         "unknown error",
+}
+
+type TransferStatus uint8
+
+const (
+	LIBUSB_TRANSFER_COMPLETED TransferStatus = C.LIBUSB_TRANSFER_COMPLETED
+	LIBUSB_TRANSFER_ERROR     TransferStatus = C.LIBUSB_TRANSFER_ERROR
+	LIBUSB_TRANSFER_TIMED_OUT TransferStatus = C.LIBUSB_TRANSFER_TIMED_OUT
+	LIBUSB_TRANSFER_CANCELLED TransferStatus = C.LIBUSB_TRANSFER_CANCELLED
+	LIBUSB_TRANSFER_STALL     TransferStatus = C.LIBUSB_TRANSFER_STALL
+	LIBUSB_TRANSFER_NO_DEVICE TransferStatus = C.LIBUSB_TRANSFER_NO_DEVICE
+	LIBUSB_TRANSFER_OVERFLOW  TransferStatus = C.LIBUSB_TRANSFER_OVERFLOW
+)
+
+var transferStatusDescription = map[TransferStatus]string{
+	LIBUSB_TRANSFER_COMPLETED: "transfer completed without error",
+	LIBUSB_TRANSFER_ERROR:     "transfer failed",
+	LIBUSB_TRANSFER_TIMED_OUT: "transfer timed out",
+	LIBUSB_TRANSFER_CANCELLED: "transfer was cancelled",
+	LIBUSB_TRANSFER_STALL:     "halt condition detected (endpoint stalled) or control request not supported",
+	LIBUSB_TRANSFER_NO_DEVICE: "device was disconnected",
+	LIBUSB_TRANSFER_OVERFLOW:  "device sent more data than requested",
+}
+
+func (ts TransferStatus) String() string {
+	return transferStatusDescription[ts]
+}
+
+func (ts TransferStatus) Error() string {
+	return "libusb: " + ts.String()
+}
diff --git a/vendor/github.com/karalabe/gousb/usb/iso.c b/vendor/github.com/karalabe/gousb/usb/iso.c
new file mode 100644
index 000000000..054486318
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/usb/iso.c
@@ -0,0 +1,79 @@
+#include "libusb.h"
+#include <stdio.h>
+#include <string.h>
+
+void print_xfer(struct libusb_transfer *xfer);
+void iso_callback(void *);
+
+void callback(struct libusb_transfer *xfer) {
+	//printf("Callback!\n");
+	//print_xfer(xfer);
+	iso_callback(xfer->user_data);
+}
+
+int submit(struct libusb_transfer *xfer) {
+	xfer->callback = &callback;
+	xfer->status = -1;
+	//print_xfer(xfer);
+	//printf("Transfer submitted\n");
+
+	/* fake
+	strcpy(xfer->buffer, "hello");
+	xfer->actual_length = 5;
+	callback(xfer);
+	return 0; */
+	return libusb_submit_transfer(xfer);
+}
+
+void print_xfer(struct libusb_transfer *xfer) {
+	int i;
+
+	printf("Transfer:\n");
+	printf("  dev_handle:   %p\n", xfer->dev_handle);
+	printf("  flags:        %08x\n", xfer->flags);
+	printf("  endpoint:     %x\n", xfer->endpoint);
+	printf("  type:         %x\n", xfer->type);
+	printf("  timeout:      %dms\n", xfer->timeout);
+	printf("  status:       %x\n", xfer->status);
+	printf("  length:       %d (act: %d)\n", xfer->length, xfer->actual_length);
+	printf("  callback:     %p\n", xfer->callback);
+	printf("  user_data:    %p\n", xfer->user_data);
+	printf("  buffer:       %p\n", xfer->buffer);
+	printf("  num_iso_pkts: %d\n", xfer->num_iso_packets);
+	printf("  packets:\n");
+	for (i = 0; i < xfer->num_iso_packets; i++) {
+		printf("    [%04d] %d (act: %d) %x\n", i,
+			xfer->iso_packet_desc[i].length,
+			xfer->iso_packet_desc[i].actual_length,
+			xfer->iso_packet_desc[i].status);
+	}
+}
+
+int extract_data(struct libusb_transfer *xfer, void *raw, int max, unsigned char *status) {
+	int i;
+	int copied = 0;
+	unsigned char *in = xfer->buffer;
+	unsigned char *out = raw;
+	for (i = 0; i < xfer->num_iso_packets; i++) {
+		struct libusb_iso_packet_descriptor pkt = xfer->iso_packet_desc[i];
+
+		// Copy the data
+		int len = pkt.actual_length;
+		if (len > max) {
+			len = max;
+		}
+		memcpy(out, in, len);
+		copied += len;
+
+		// Increment offsets
+		in += pkt.length;
+		out += len;
+
+		// Extract first error
+		if (pkt.status == 0 || *status != 0) {
+			continue;
+		}
+		*status = pkt.status;
+	}
+	return copied;
+}
diff --git a/vendor/github.com/karalabe/gousb/usb/iso.go b/vendor/github.com/karalabe/gousb/usb/iso.go
new file mode 100644
index 000000000..1ba694e0e
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/usb/iso.go
@@ -0,0 +1,148 @@
+// Copyright 2013 Google Inc.  All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package usb
+
+/*
+#include "libusb.h"
+
+int submit(struct libusb_transfer *xfer);
+void print_xfer(struct libusb_transfer *xfer);
+int extract_data(struct libusb_transfer *xfer, void *data, int max, unsigned char *status);
+*/
+import "C"
+
+import (
+	"fmt"
+	"log"
+	"time"
+	"unsafe"
+)
+
+//export iso_callback
+func iso_callback(cptr unsafe.Pointer) {
+	ch := *(*chan struct{})(cptr)
+	close(ch)
+}
+
+func (end *endpoint) allocTransfer() *Transfer {
+	// Use libusb_get_max_iso_packet_size ?
+	const (
+		iso_packets = 8       // 128 // 242
+		packet_size = 2 * 960 // 1760
+	)
+
+	xfer := C.libusb_alloc_transfer(C.int(iso_packets))
+	if xfer == nil {
+		log.Printf("usb: transfer allocation failed?!")
+		return nil
+	}
+
+	buf := make([]byte, iso_packets*packet_size)
+	done := make(chan struct{}, 1)
+
+	xfer.dev_handle = end.Device.handle
+	xfer.endpoint = C.uchar(end.Address)
+	xfer._type = C.LIBUSB_TRANSFER_TYPE_ISOCHRONOUS
+
+	xfer.buffer = (*C.uchar)((unsafe.Pointer)(&buf[0]))
+	xfer.length = C.int(len(buf))
+	xfer.num_iso_packets = iso_packets
+
+	C.libusb_set_iso_packet_lengths(xfer, packet_size)
+	/*
+		pkts := *(*[]C.struct_libusb_packet_descriptor)(unsafe.Pointer(&reflect.SliceHeader{
+			Data: uintptr(unsafe.Pointer(&xfer.iso_packet_desc)),
+			Len:  iso_packets,
+			Cap:  iso_packets,
+		}))
+	*/
+
+	t := &Transfer{
+		xfer: xfer,
+		done: done,
+		buf:  buf,
+	}
+	xfer.user_data = (unsafe.Pointer)(&t.done)
+
+	return t
+}
+
+type Transfer struct {
+	xfer *C.struct_libusb_transfer
+	pkts []*C.struct_libusb_packet_descriptor
+	done chan struct{}
+	buf  []byte
+}
+
+func (t *Transfer) Submit(timeout time.Duration) error {
+	//log.Printf("iso: submitting %#v", t.xfer)
+	t.xfer.timeout = C.uint(timeout / time.Millisecond)
+	if errno := C.submit(t.xfer); errno < 0 {
+		return usbError(errno)
+	}
+	return nil
+}
+
+func (t *Transfer) Wait(b []byte) (n int, err error) {
+	select {
+	case <-time.After(10 * time.Second):
+		return 0, fmt.Errorf("wait timed out after 10s")
+	case <-t.done:
+	}
+	// Non-iso transfers:
+	//n = int(t.xfer.actual_length)
+	//copy(b, ((*[1 << 16]byte)(unsafe.Pointer(t.xfer.buffer)))[:n])
+
+	//C.print_xfer(t.xfer)
+	/*
+		buf, offset := ((*[1 << 16]byte)(unsafe.Pointer(t.xfer.buffer))), 0
+		for i, pkt := range *t.pkts {
+			log.Printf("Type is %T", t.pkts)
+			n += copy(b[n:], buf[offset:][:pkt.actual_length])
+			offset += pkt.Length
+			if pkt.status != 0 && err == nil {
+				err = error(TransferStatus(pkt.status))
+			}
+		}
+	*/
+	var status uint8
+	n = int(C.extract_data(t.xfer, unsafe.Pointer(&b[0]), C.int(len(b)), (*C.uchar)(unsafe.Pointer(&status))))
+	if status != 0 {
+		err = TransferStatus(status)
+	}
+	return n, err
+}
+
+func (t *Transfer) Close() error {
+	C.libusb_free_transfer(t.xfer)
+	return nil
+}
+
+func isochronous_xfer(e *endpoint, buf []byte, timeout time.Duration) (int, error) {
+	t := e.allocTransfer()
+	defer t.Close()
+
+	if err := t.Submit(timeout); err != nil {
+		log.Printf("iso: xfer failed to submit: %s", err)
+		return 0, err
+	}
+
+	n, err := t.Wait(buf)
+	if err != nil {
+		log.Printf("iso: xfer failed: %s", err)
+		return 0, err
+	}
+	return n, err
+}
diff --git a/vendor/github.com/karalabe/gousb/usb/misc.go b/vendor/github.com/karalabe/gousb/usb/misc.go
new file mode 100644
index 000000000..6e25431bf
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/usb/misc.go
@@ -0,0 +1,47 @@
+// Copyright 2013 Google Inc.  All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package usb
+
+import (
+	"fmt"
+)
+
+type BCD uint16
+
+const (
+	USB_2_0 BCD = 0x0200
+	USB_1_1 BCD = 0x0110
+	USB_1_0 BCD = 0x0100
+)
+
+func (d BCD) Int() (i int) {
+	ten := 1
+	for o := uint(0); o < 4; o++ {
+		n := ((0xF << (o * 4)) & d) >> (o * 4)
+		i += int(n) * ten
+		ten *= 10
+	}
+	return
+}
+
+func (d BCD) String() string {
+	return fmt.Sprintf("%02x.%02x", int(d>>8), int(d&0xFF))
+}
+
+type ID uint16
+
+func (id ID) String() string {
+	return fmt.Sprintf("%04x", int(id))
+}
diff --git a/vendor/github.com/karalabe/gousb/usb/usb.go b/vendor/github.com/karalabe/gousb/usb/usb.go
new file mode 100644
index 000000000..366827e69
--- /dev/null
+++ b/vendor/github.com/karalabe/gousb/usb/usb.go
@@ -0,0 +1,178 @@
+// Copyright 2013 Google Inc.  All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package usb provides a wrapper around libusb-1.0.
+package usb
+
+/*
+#cgo CFLAGS: -I../internal/libusb/libusb
+#cgo CFLAGS: -DDEFAULT_VISIBILITY=""
+#cgo linux CFLAGS: -DOS_LINUX -D_GNU_SOURCE -DPOLL_NFDS_TYPE=int
+#cgo darwin CFLAGS: -DOS_DARWIN -DPOLL_NFDS_TYPE=int
+#cgo darwin LDFLAGS: -framework CoreFoundation -framework IOKit -lobjc
+#cgo openbsd CFLAGS: -DOS_OPENBSD -DPOLL_NFDS_TYPE=int
+#cgo windows CFLAGS: -DOS_WINDOWS -DUSE_USBDK -DPOLL_NFDS_TYPE=int
+
+#if defined(OS_LINUX) || defined(OS_DARWIN) || defined(OS_OPENBSD)
+	#include <sys/poll.h>
+	#include "os/threads_posix.c"
+	#include "os/poll_posix.c"
+#elif defined(OS_WINDOWS)
+	#include "os/threads_windows.c"
+	#include "os/poll_windows.c"
+#endif
+
+#ifdef OS_LINUX
+	#include "os/linux_usbfs.c"
+	#include "os/linux_netlink.c"
+#elif OS_DARWIN
+	#include "os/darwin_usb.c"
+#elif OS_OPENBSD
+	#include "os/openbsd_usb.c"
+#elif OS_WINDOWS
+	#include "os/windows_nt_common.c"
+	#include "os/windows_usbdk.c"
+#endif
+
+#include "core.c"
+#include "descriptor.c"
+#include "hotplug.c"
+#include "io.c"
+#include "strerror.c"
+#include "sync.c"
+*/
+import "C"
+
+import (
+	"log"
+	"reflect"
+	"unsafe"
+)
+
+type Context struct {
+	ctx  *C.libusb_context
+	done chan struct{}
+}
+
+func (c *Context) Debug(level int) {
+	C.libusb_set_debug(c.ctx, C.int(level))
+}
+
+func NewContext() (*Context, error) {
+	c := &Context{
+		done: make(chan struct{}),
+	}
+
+	if errno := C.libusb_init(&c.ctx); errno != 0 {
+		return nil, usbError(errno)
+	}
+
+	go func() {
+		tv := C.struct_timeval{
+			tv_sec:  0,
+			tv_usec: 100000,
+		}
+		for {
+			select {
+			case <-c.done:
+				return
+			default:
+			}
+			if errno := C.libusb_handle_events_timeout_completed(c.ctx, &tv, nil); errno < 0 {
+				log.Printf("handle_events: error: %s", usbError(errno))
+				continue
+			}
+			//log.Printf("handle_events returned")
+		}
+	}()
+
+	return c, nil
+}
+
+// ListDevices calls each with each enumerated device.
+// If the function returns true, the device is opened and a Device is returned if the operation succeeds.
+// Every Device returned (whether an error is also returned or not) must be closed.
+// If there are any errors enumerating the devices,
+// the final one is returned along with any successfully opened devices.
+func (c *Context) ListDevices(each func(desc *Descriptor) bool) ([]*Device, error) {
+	var list **C.libusb_device
+	cnt := C.libusb_get_device_list(c.ctx, &list)
+	if cnt < 0 {
+		return nil, usbError(cnt)
+	}
+	defer C.libusb_free_device_list(list, 1)
+
+	var slice []*C.libusb_device
+	*(*reflect.SliceHeader)(unsafe.Pointer(&slice)) = reflect.SliceHeader{
+		Data: uintptr(unsafe.Pointer(list)),
+		Len:  int(cnt),
+		Cap:  int(cnt),
+	}
+
+	var reterr error
+	var ret []*Device
+	for _, dev := range slice {
+		desc, err := newDescriptor(dev)
+		if err != nil {
+			reterr = err
+			continue
+		}
+
+		if each(desc) {
+			var handle *C.libusb_device_handle
+			if errno := C.libusb_open(dev, &handle); errno != 0 {
+				reterr = usbError(errno)
+				continue
+			}
+			if dev, err := newDevice(handle, desc); err != nil {
+				reterr = err
+			} else {
+				ret = append(ret, dev)
+			}
+		}
+	}
+	return ret, reterr
+}
+
+// OpenDeviceWithVidPid opens Device from specific VendorId and ProductId.
+// If there are any errors, it'll returns at second value.
+func (c *Context) OpenDeviceWithVidPid(vid, pid int) (*Device, error) {
+
+	handle := C.libusb_open_device_with_vid_pid(c.ctx, (C.uint16_t)(vid), (C.uint16_t)(pid))
+	if handle == nil {
+		return nil, ERROR_NOT_FOUND
+	}
+
+	dev := C.libusb_get_device(handle)
+	if dev == nil {
+		return nil, ERROR_NO_DEVICE
+	}
+
+	desc, err := newDescriptor(dev)
+
+	// return an error from nil-handle and nil-device
+	if err != nil {
+		return nil, err
+	}
+	return newDevice(handle, desc)
+}
+
+func (c *Context) Close() error {
+	close(c.done)
+	if c.ctx != nil {
+		C.libusb_exit(c.ctx)
+	}
+	c.ctx = nil
+	return nil
+}