Merge branch 'gousb2.0-dev' of https://github.com/kylelemons/gousb into gousb2.0-dev

usb/config.go

@@ -15,47 +15,11 @@
 
 package usb
 
-import "fmt"
+import (
-
+	"fmt"
-// InterfaceInfo contains information about a USB interface, extracted from
+	"sync"
-// the descriptor.
+	"time"
-type InterfaceInfo struct {
+)
-	// Number is the number of this interface, a zero-based index in the array
-	// of interfaces supported by the device configuration.
-	Number int
-	// AltSettings is a list of alternate settings supported by the interface.
-	AltSettings []InterfaceSetting
-}
-
-// String returns a human-readable descripton of the interface and it's
-// alternate settings.
-func (i InterfaceInfo) String() string {
-	return fmt.Sprintf("Interface %d (%d alternate settings)", i.Number, len(i.AltSettings))
-}
-
-// InterfaceSetting contains information about a USB interface with a particular
-// alternate setting, extracted from the descriptor.
-type InterfaceSetting struct {
-	// Number is the number of this interface, the same as in InterfaceInfo.
-	Number int
-	// Alternate is the number of this alternate setting.
-	Alternate int
-	// Class is the USB-IF class code, as defined by the USB spec.
-	Class Class
-	// SubClass is the USB-IF subclass code, as defined by the USB spec.
-	SubClass Class
-	// Protocol is USB protocol code, as defined by the USB spe.c
-	Protocol Protocol
-	// Endpoints has the list of endpoints available on this interface with
-	// this alternate setting.
-	Endpoints []EndpointInfo
-}
-
-// String returns a human-readable descripton of the particular
-// alternate setting of an interface.
-func (a InterfaceSetting) String() string {
-	return fmt.Sprintf("Interface %d alternate setting %d", a.Number, a.Alternate)
-}
 
 // ConfigInfo contains the information about a USB device configuration.
 type ConfigInfo struct {
@@ -75,5 +39,73 @@ type ConfigInfo struct {
 
 // String returns the human-readable description of the configuration.
 func (c ConfigInfo) String() string {
-	return fmt.Sprintf("Config %d", c.Config)
+	return fmt.Sprintf("config=%d", c.Config)
+}
+
+// Config represents a USB device set to use a particular configuration.
+// Only one Config of a particular device can be used at any one time.
+type Config struct {
+	Info           ConfigInfo
+	ControlTimeout time.Duration
+
+	dev *Device
+
+	// Claimed interfaces
+	mu      sync.Mutex
+	claimed map[int]bool
+}
+
+// Close releases the underlying device, allowing the caller to switch the device to a different configuration.
+func (c *Config) Close() error {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if len(c.claimed) > 0 {
+		var ifs []int
+		for k := range c.claimed {
+			ifs = append(ifs, k)
+		}
+		return fmt.Errorf("failed to release %s, interfaces %v are still open", c, ifs)
+	}
+	c.dev.mu.Lock()
+	defer c.dev.mu.Unlock()
+	c.dev.claimed = nil
+	return nil
+}
+
+func (c *Config) String() string {
+	return fmt.Sprintf("%s,%s", c.dev.String(), c.Info.String())
+}
+
+// Control sends a control request to the device.
+func (c *Config) Control(rType, request uint8, val, idx uint16, data []byte) (int, error) {
+	return libusb.control(c.dev.handle, c.ControlTimeout, rType, request, val, idx, data)
+}
+
+// Interface claims and returns an interface on a USB device.
+func (c *Config) Interface(intf, alt int) (*Interface, error) {
+	if intf < 0 || intf >= len(c.Info.Interfaces) {
+		return nil, fmt.Errorf("interface %d not found in %s. Interface number needs to be a 0-based index into the interface table, which has %d elements.", intf, c, len(c.Info.Interfaces))
+	}
+	ifInfo := c.Info.Interfaces[intf]
+	if alt < 0 || alt >= len(ifInfo.AltSettings) {
+		return nil, fmt.Errorf("Inteface %d does not have alternate setting %d. Alt setting needs to be a 0-based index into the settings table, which has %d elements.", ifInfo, alt, len(ifInfo.AltSettings))
+	}
+
+	// Claim the interface
+	if err := libusb.claim(c.dev.handle, uint8(intf)); err != nil {
+		return nil, fmt.Errorf("failed to claim interface %d on %s: %v", intf, c, err)
+	}
+
+	if err := libusb.setAlt(c.dev.handle, uint8(intf), uint8(alt)); err != nil {
+		libusb.release(c.dev.handle, uint8(intf))
+		return nil, fmt.Errorf("failed to set alternate config %d on interface %d of %s: %v", alt, intf, c, err)
+	}
+
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	c.claimed[intf] = true
+	return &Interface{
+		Setting: ifInfo.AltSettings[alt],
+		config:  c,
+	}, nil
 }

usb/debug.go

@@ -33,5 +33,5 @@ func init() {
 	if os.Getenv(debugEnvVarName) != "" {
 		out = os.Stderr
 	}
-	debug = log.New(out, "usb", log.LstdFlags|log.Lshortfile)
+	debug = log.New(out, "gousb: ", log.LstdFlags|log.Lshortfile)
 }

usb/descriptor.go

@@ -15,6 +15,8 @@
 
 package usb
 
+import "fmt"
+
 // Descriptor is a representation of a USB device descriptor.
 type Descriptor struct {
 	// Bus information
@@ -37,3 +39,8 @@ type Descriptor struct {
 	// Configuration information
 	Configs []ConfigInfo
 }
+
+// String represents a human readable representation of the device in the descriptor.
+func (d *Descriptor) String() string {
+	return fmt.Sprintf("vid=%s,pid=%s,bus=%d,addr=%d", d.Vendor, d.Product, d.Bus, d.Address)
+}

usb/device.go

@@ -18,16 +18,6 @@ package usb
 import (
 	"fmt"
 	"sync"
-	"time"
-)
-
-var (
-	// DefaultReadTimeout controls the default timeout for IN endpoint transfers.
-	DefaultReadTimeout = 1 * time.Second
-	// DefaultWriteTimeout controls the default timeout for OUT endpoint transfers.
-	DefaultWriteTimeout = 1 * time.Second
-	// DefaultControlTimeout controls the default timeout for control transfers.
-	DefaultControlTimeout = 250 * time.Millisecond
 )
 
 // Device represents an opened USB device.
@@ -37,39 +27,19 @@ type Device struct {
 	// Embed the device information for easy access
 	*Descriptor
 
-	// Timeouts
+	// Claimed config
-	ReadTimeout    time.Duration
+	mu      sync.Mutex
-	WriteTimeout   time.Duration
+	claimed *Config
-	ControlTimeout time.Duration
-
-	// Claimed interfaces
-	lock    *sync.Mutex
-	claimed map[int]int
-}
-
-func newDevice(handle *libusbDevHandle, desc *Descriptor) *Device {
-	ifaces := 0
-	d := &Device{
-		handle:         handle,
-		Descriptor:     desc,
-		ReadTimeout:    DefaultReadTimeout,
-		WriteTimeout:   DefaultWriteTimeout,
-		ControlTimeout: DefaultControlTimeout,
-		lock:           new(sync.Mutex),
-		claimed:        make(map[int]int, ifaces),
-	}
-
-	return d
 }
 
 // Reset performs a USB port reset to reinitialize a device.
 func (d *Device) Reset() error {
-	return libusb.reset(d.handle)
+	d.mu.Lock()
+	defer d.mu.Unlock()
+	if d.claimed != nil {
+		return fmt.Errorf("can't reset a device with an open configuration")
 	}
-
+	return libusb.reset(d.handle)
-// Control sends a control request to the device.
-func (d *Device) Control(rType, request uint8, val, idx uint16, data []byte) (int, error) {
-	return libusb.control(d.handle, d.ControlTimeout, rType, request, val, idx, data)
 }
 
 // ActiveConfig returns the config id (not the index) of the active configuration.
@@ -79,136 +49,51 @@ func (d *Device) ActiveConfig() (int, error) {
 	return int(ret), err
 }
 
-// SetConfig attempts to change the active configuration.
+// Config returns a USB device set to use a particular config.
 // 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 int) error {
+// USB supports only one active config per device at a time. Config claims the
-	return libusb.setConfig(d.handle, uint8(cfg))
+// device before setting the desired config and keeps it locked until Close is called.
+func (d *Device) Config(cfgNum int) (*Config, error) {
+	cfg := &Config{
+		dev:     d,
+		claimed: make(map[int]bool),
+	}
+	var found bool
+	for _, info := range d.Descriptor.Configs {
+		if info.Config == cfgNum {
+			found = true
+			cfg.Info = info
+			break
+		}
+	}
+	if !found {
+		return nil, fmt.Errorf("configuration id %d not found in the descriptor of the device %s", cfg, d)
+	}
+	if err := libusb.setConfig(d.handle, uint8(cfgNum)); err != nil {
+		return nil, fmt.Errorf("failed to set active config %d for the device %s: %v", cfgNum, d, err)
+	}
+	d.mu.Lock()
+	defer d.mu.Unlock()
+	d.claimed = cfg
+	return cfg, nil
 }
 
 // Close closes the device.
 func (d *Device) Close() error {
 	if d.handle == nil {
-		return fmt.Errorf("usb: double close on device")
+		return fmt.Errorf("double close on device %s", d)
 	}
-	d.lock.Lock()
+	d.mu.Lock()
-	defer d.lock.Unlock()
+	defer d.mu.Unlock()
-	for iface := range d.claimed {
+	if d.claimed != nil {
-		libusb.release(d.handle, uint8(iface))
+		return fmt.Errorf("can't release the device %s, it has an open config %s", d, d.claimed.Info.Config)
 	}
 	libusb.close(d.handle)
 	d.handle = nil
 	return nil
 }
 
-func (d *Device) openEndpoint(cfgNum, ifNum, setNum, epAddr int) (*endpoint, error) {
-	var cfg *ConfigInfo
-	for _, c := range d.Configs {
-		if c.Config == cfgNum {
-			debug.Printf("found conf: %+v\n", c)
-			cfg = &c
-			break
-		}
-	}
-	if cfg == nil {
-		return nil, fmt.Errorf("usb: unknown configuration 0x%02x", cfgNum)
-	}
-
-	var intf *InterfaceInfo
-	for _, i := range cfg.Interfaces {
-		if i.Number == ifNum {
-			debug.Printf("found iface: %+v\n", i)
-			intf = &i
-			break
-		}
-	}
-	if intf == nil {
-		return nil, fmt.Errorf("usb: unknown interface 0x%02x", ifNum)
-	}
-
-	var setAlternate bool
-	var ifs *InterfaceSetting
-	for i, s := range intf.AltSettings {
-		if s.Alternate == setNum {
-			setAlternate = i != 0
-			debug.Printf("found setup: %+v [default: %v]\n", s, !setAlternate)
-			ifs = &s
-			break
-		}
-	}
-	if ifs == nil {
-		return nil, fmt.Errorf("usb: unknown setup 0x%02x", setNum)
-	}
-
-	var ep *EndpointInfo
-	for _, e := range ifs.Endpoints {
-		if endpointAddr(e.Number, e.Direction) == epAddr {
-			debug.Printf("found ep #%d %s in %+v\n", e.Number, e.Direction, *ifs)
-			ep = &e
-			break
-		}
-	}
-	if ep == nil {
-		return nil, fmt.Errorf("usb: didn't find endpoint address 0x%02x", epAddr)
-	}
-
-	end := newEndpoint(d.handle, *ifs, *ep)
-
-	// Set the configuration
-	activeConf, err := libusb.getConfig(d.handle)
-	if err != nil {
-		return nil, fmt.Errorf("usb: getcfg: %s", err)
-	}
-	if activeConf != uint8(cfgNum) {
-		if err := libusb.setConfig(d.handle, uint8(cfgNum)); err != nil {
-			return nil, fmt.Errorf("usb: setcfg: %s", err)
-		}
-	}
-
-	// Claim the interface
-	if err := libusb.claim(d.handle, uint8(ifNum)); err != nil {
-		return nil, fmt.Errorf("usb: claim: %s", err)
-	}
-
-	// Increment the claim count
-	d.lock.Lock()
-	d.claimed[ifNum]++
-	d.lock.Unlock() // unlock immediately because the next calls may block
-
-	// Choose the alternate
-	if setAlternate {
-		if err := libusb.setAlt(d.handle, uint8(ifNum), uint8(setNum)); err != nil {
-			return nil, fmt.Errorf("usb: setalt: %s", err)
-		}
-	}
-
-	return end, nil
-}
-
-// InEndpoint prepares an IN endpoint for transfer.
-func (d *Device) InEndpoint(cfgNum, ifNum, setNum, epNum int) (*InEndpoint, error) {
-	ep, err := d.openEndpoint(cfgNum, ifNum, setNum, endpointAddr(epNum, EndpointDirectionIn))
-	if err != nil {
-		return nil, err
-	}
-	ep.SetTimeout(d.ReadTimeout)
-	return &InEndpoint{
-		endpoint: ep,
-	}, nil
-}
-
-// OutEndpoint prepares an OUT endpoint for transfer.
-func (d *Device) OutEndpoint(cfgNum, ifNum, setNum, epNum int) (*OutEndpoint, error) {
-	ep, err := d.openEndpoint(cfgNum, ifNum, setNum, endpointAddr(epNum, EndpointDirectionOut))
-	if err != nil {
-		return nil, err
-	}
-	ep.SetTimeout(d.WriteTimeout)
-	return &OutEndpoint{
-		endpoint: ep,
-	}, nil
-}
-
 // GetStringDescriptor returns a device string descriptor with the given index
 // number. The first supported language is always used and the returned
 // descriptor string is converted to ASCII (non-ASCII characters are replaced

usb/device_test.go

@@ -31,9 +31,19 @@ func TestOpenEndpoint(t *testing.T) {
 	}
 	defer dev.Close()
 	if err != nil {
-		t.Fatalf("OpenDeviceWithVidPid(0x8888, 0x0002): got error %v, want nil", err)
+		t.Fatalf("OpenDeviceWithVidPid(0x8888, 0x0002): %v", err)
 	}
-	got, err := dev.InEndpoint(1, 1, 1, 6)
+	cfg, err := dev.Config(1)
+	if err != nil {
+		t.Fatalf("%s Config(1): %v", dev, err)
+	}
+	defer cfg.Close()
+	intf, err := cfg.Interface(1, 1)
+	if err != nil {
+		t.Fatalf("%s Interface(1, 1): %v", cfg, err)
+	}
+	defer intf.Close()
+	got, err := intf.InEndpoint(6)
 	if err != nil {
 		t.Fatalf("InEndpoint(cfg=1, if=1, alt=1, ep=6IN): got error %v, want nil", err)
 	}

usb/endpoint.go

@@ -57,7 +57,7 @@ func endpointAddr(n int, d EndpointDirection) int {
 // String returns the human-readable description of the endpoint.
 func (e EndpointInfo) String() string {
 	ret := make([]string, 0, 3)
-	ret = append(ret, fmt.Sprintf("Endpoint #%d %s (address 0x%02x) %s", e.Number, e.Direction, endpointAddr(e.Number, e.Direction), e.TransferType))
+	ret = append(ret, fmt.Sprintf("ep #%d %s (address 0x%02x) %s", e.Number, e.Direction, endpointAddr(e.Number, e.Direction), e.TransferType))
 	switch e.TransferType {
 	case TransferTypeIsochronous:
 		ret = append(ret, fmt.Sprintf("- %s %s", e.IsoSyncType, e.UsageType))
@@ -74,7 +74,7 @@ type endpoint struct {
 	InterfaceSetting
 	Info EndpointInfo
 
-	timeout time.Duration
+	Timeout time.Duration
 }
 
 // String returns a human-readable description of the endpoint.
@@ -82,18 +82,12 @@ func (e *endpoint) String() string {
 	return e.Info.String()
 }
 
-// SetTimeout sets a timeout duration for all new USB transfers involving
-// this endpoint.
-func (e *endpoint) SetTimeout(t time.Duration) {
-	e.timeout = t
-}
-
 func (e *endpoint) transfer(buf []byte) (int, error) {
 	if len(buf) == 0 {
 		return 0, nil
 	}
 
-	t, err := newUSBTransfer(e.h, &e.Info, buf, e.timeout)
+	t, err := newUSBTransfer(e.h, &e.Info, buf, e.Timeout)
 	if err != nil {
 		return 0, err
 	}
@@ -110,14 +104,6 @@ func (e *endpoint) transfer(buf []byte) (int, error) {
 	return n, nil
 }
 
-func newEndpoint(h *libusbDevHandle, s InterfaceSetting, e EndpointInfo) *endpoint {
-	return &endpoint{
-		InterfaceSetting: s,
-		Info:             e,
-		h:                h,
-	}
-}
-
 // InEndpoint represents an IN endpoint open for transfer.
 type InEndpoint struct {
 	*endpoint

usb/endpoint_stream.go

@@ -17,7 +17,7 @@ package usb
 func (e *endpoint) newStream(size, count int, submit bool) (*stream, error) {
 	var ts []transferIntf
 	for i := 0; i < count; i++ {
-		t, err := newUSBTransfer(e.h, &e.Info, make([]byte, size), e.timeout)
+		t, err := newUSBTransfer(e.h, &e.Info, make([]byte, size), e.Timeout)
 		if err != nil {
 			for _, t := range ts {
 				t.free()

usb/endpoint_test.go

@@ -85,7 +85,7 @@ func TestEndpoint(t *testing.T) {
 				wantErr: true,
 			},
 		} {
-			ep := newEndpoint(nil, epData.intf, epData.ei)
+			ep := &endpoint{h: nil, InterfaceSetting: epData.intf, Info: epData.ei}
 			go func() {
 				fakeT := lib.waitForSubmitted()
 				fakeT.length = tc.ret
@@ -116,7 +116,7 @@ func TestEndpointInfo(t *testing.T) {
 				TransferType:  TransferTypeBulk,
 				MaxPacketSize: 512,
 			},
-			want: "Endpoint #6 IN (address 0x86) bulk [512 bytes]",
+			want: "ep #6 IN (address 0x86) bulk [512 bytes]",
 		},
 		{
 			ep: EndpointInfo{
@@ -127,7 +127,7 @@ func TestEndpointInfo(t *testing.T) {
 				IsoSyncType:   IsoSyncTypeAsync,
 				UsageType:     IsoUsageTypeData,
 			},
-			want: "Endpoint #2 OUT (address 0x02) isochronous - asynchronous data [512 bytes]",
+			want: "ep #2 OUT (address 0x02) isochronous - asynchronous data [512 bytes]",
 		},
 		{
 			ep: EndpointInfo{
@@ -137,7 +137,7 @@ func TestEndpointInfo(t *testing.T) {
 				MaxPacketSize: 16,
 				UsageType:     InterruptUsageTypePeriodic,
 			},
-			want: "Endpoint #3 IN (address 0x83) interrupt - periodic [16 bytes]",
+			want: "ep #3 IN (address 0x83) interrupt - periodic [16 bytes]",
 		},
 	} {
 		if got := tc.ep.String(); got != tc.want {
@@ -146,7 +146,7 @@ func TestEndpointInfo(t *testing.T) {
 	}
 }
 
-func TestEndpointIn(t *testing.T) {
+func TestEndpointInOut(t *testing.T) {
 	defer func(i libusbIntf) { libusb = i }(libusb)
 
 	lib, done := newFakeLibusb()
@@ -158,9 +158,30 @@ func TestEndpointIn(t *testing.T) {
 	if err != nil {
 		t.Fatalf("OpenDeviceWithVidPid(0x9999, 0x0001): got error %v, want nil", err)
 	}
-	ep, err := d.InEndpoint(1, 0, 0, 2)
+	defer func() {
+		if err := d.Close(); err != nil {
+			t.Errorf("%s.Close(): %v", d, err)
+		}
+	}()
+	cfg, err := d.Config(1)
 	if err != nil {
-		t.Fatalf("InEndpoint(1, 0, 0, 2): got error %v, want nil", err)
+		t.Fatalf("%s.Config(1): %v", d, err)
+	}
+	defer func() {
+		if err := cfg.Close(); err != nil {
+			t.Errorf("%s.Close(): %v", cfg, err)
+		}
+	}()
+	intf, err := cfg.Interface(0, 0)
+	if err != nil {
+		t.Fatalf("%s.Interface(0, 0): %v", cfg, err)
+	}
+	defer intf.Close()
+
+	// IN endpoint 2
+	iep, err := intf.InEndpoint(2)
+	if err != nil {
+		t.Fatalf("%s.InEndpoint(2): got error %v, want nil", intf, err)
 	}
 	dataTransferred := 100
 	go func() {
@@ -170,52 +191,38 @@ func TestEndpointIn(t *testing.T) {
 		close(fakeT.done)
 	}()
 	buf := make([]byte, 512)
-	got, err := ep.Read(buf)
+	got, err := iep.Read(buf)
 	if err != nil {
-		t.Errorf("ep.Read: got error %v, want nil", err)
+		t.Errorf("%s.Read: got error %v, want nil", iep, err)
 	} else if got != dataTransferred {
-		t.Errorf("ep.Read: got %d, want %d", got, dataTransferred)
+		t.Errorf("%s.Read: got %d, want %d", iep, got, dataTransferred)
 	}
 
-	_, err = d.InEndpoint(1, 0, 0, 1)
+	_, err = intf.InEndpoint(1)
 	if err == nil {
-		t.Error("InEndpoint(1, 0, 0, 1): got nil, want error")
+		t.Errorf("%s.InEndpoint(1): got nil, want error", intf)
-	}
 	}
 
-func TestEndpointOut(t *testing.T) {
+	// OUT endpoint 1
-	defer func(i libusbIntf) { libusb = i }(libusb)
+	oep, err := intf.OutEndpoint(1)
-
-	lib, done := newFakeLibusb()
-	defer done()
-
-	ctx := NewContext()
-	defer ctx.Close()
-	d, err := ctx.OpenDeviceWithVidPid(0x9999, 0x0001)
 	if err != nil {
-		t.Fatalf("OpenDeviceWithVidPid(0x9999, 0x0001): got error %v, want nil", err)
+		t.Fatalf("%s.OutEndpoint(1): got error %v, want nil", intf, err)
 	}
-	ep, err := d.OutEndpoint(1, 0, 0, 1)
-	if err != nil {
-		t.Fatalf("OutEndpoint(1, 0, 0, 1): got error %v, want nil", err)
-	}
-	dataTransferred := 100
 	go func() {
 		fakeT := lib.waitForSubmitted()
 		fakeT.length = dataTransferred
 		fakeT.status = TransferCompleted
 		close(fakeT.done)
 	}()
-	buf := make([]byte, 512)
+	got, err = oep.Write(buf)
-	got, err := ep.Write(buf)
 	if err != nil {
-		t.Errorf("ep.Write: got error %v, want nil", err)
+		t.Errorf("%s.Write: got error %v, want nil", oep, err)
 	} else if got != dataTransferred {
-		t.Errorf("ep.Write: got %d, want %d", got, dataTransferred)
+		t.Errorf("%s.Write: got %d, want %d", oep, got, dataTransferred)
 	}
 
-	_, err = d.OutEndpoint(1, 0, 0, 2)
+	_, err = intf.OutEndpoint(2)
 	if err == nil {
-		t.Error("OutEndpoint(1, 0, 0, 2): got nil, want error")
+		t.Errorf("%s.OutEndpoint(2): got nil, want error", intf)
 	}
 }

usb/fakelibusb_test.go

@@ -214,6 +214,7 @@ func (f *fakeLibusb) control(*libusbDevHandle, time.Duration, uint8, uint8, uint
 }
 func (f *fakeLibusb) getConfig(*libusbDevHandle) (uint8, error) { return 1, nil }
 func (f *fakeLibusb) setConfig(d *libusbDevHandle, cfg uint8) error {
+	debug.Printf("setConfig(%p, %d)\n", d, cfg)
 	f.mu.Lock()
 	defer f.mu.Unlock()
 	if len(f.claims[f.handles[d]]) != 0 {
@@ -230,6 +231,7 @@ func (f *fakeLibusb) getStringDesc(*libusbDevHandle, int) (string, error) {
 func (f *fakeLibusb) setAutoDetach(*libusbDevHandle, int) error { return nil }
 
 func (f *fakeLibusb) claim(d *libusbDevHandle, intf uint8) error {
+	debug.Printf("claim(%p, %d)\n", d, intf)
 	f.mu.Lock()
 	defer f.mu.Unlock()
 	c := f.claims[f.handles[d]]
@@ -241,6 +243,7 @@ func (f *fakeLibusb) claim(d *libusbDevHandle, intf uint8) error {
 	return nil
 }
 func (f *fakeLibusb) release(d *libusbDevHandle, intf uint8) {
+	debug.Printf("release(%p, %d)\n", d, intf)
 	f.mu.Lock()
 	defer f.mu.Unlock()
 	c := f.claims[f.handles[d]]
@@ -250,6 +253,7 @@ func (f *fakeLibusb) release(d *libusbDevHandle, intf uint8) {
 	c[intf] = false
 }
 func (f *fakeLibusb) setAlt(d *libusbDevHandle, intf, alt uint8) error {
+	debug.Printf("setAlt(%p, %d, %d)\n", d, intf, alt)
 	f.mu.Lock()
 	defer f.mu.Unlock()
 	if !f.claims[f.handles[d]][intf] {

usb/interface.go

@@ -0,0 +1,127 @@
+// Copyright 2013 Google Inc.  All rights reserved.
+// Copyright 2016 the gousb Authors.  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"
+)
+
+// InterfaceInfo contains information about a USB interface, extracted from
+// the descriptor.
+type InterfaceInfo struct {
+	// Number is the number of this interface, a zero-based index in the array
+	// of interfaces supported by the device configuration.
+	Number int
+	// AltSettings is a list of alternate settings supported by the interface.
+	AltSettings []InterfaceSetting
+}
+
+// String returns a human-readable descripton of the interface and it's
+// alternate settings.
+func (i InterfaceInfo) String() string {
+	return fmt.Sprintf("if=%d", i.Number)
+}
+
+// InterfaceSetting contains information about a USB interface with a particular
+// alternate setting, extracted from the descriptor.
+type InterfaceSetting struct {
+	// Number is the number of this interface, the same as in InterfaceInfo.
+	Number int
+	// Alternate is the number of this alternate setting.
+	Alternate int
+	// Class is the USB-IF class code, as defined by the USB spec.
+	Class Class
+	// SubClass is the USB-IF subclass code, as defined by the USB spec.
+	SubClass Class
+	// Protocol is USB protocol code, as defined by the USB spe.c
+	Protocol Protocol
+	// Endpoints has the list of endpoints available on this interface with
+	// this alternate setting.
+	Endpoints []EndpointInfo
+}
+
+// String returns a human-readable descripton of the particular
+// alternate setting of an interface.
+func (a InterfaceSetting) String() string {
+	return fmt.Sprintf("Interface %d alternate setting %d", a.Number, a.Alternate)
+}
+
+type Interface struct {
+	Setting InterfaceSetting
+
+	config *Config
+}
+
+func (i *Interface) String() string {
+	return fmt.Sprintf("%s,if=%d,alt=%d", i.config, i.Setting.Number, i.Setting.Alternate)
+}
+
+// Close releases the interface.
+func (i *Interface) Close() {
+	libusb.release(i.config.dev.handle, uint8(i.Setting.Number))
+	i.config.mu.Lock()
+	defer i.config.mu.Unlock()
+	delete(i.config.claimed, i.Setting.Number)
+}
+
+func (i *Interface) openEndpoint(epNum int) (*endpoint, error) {
+	var ep EndpointInfo
+	var found bool
+	for _, e := range i.Setting.Endpoints {
+		if e.Number == epNum {
+			debug.Printf("found ep %s in %s\n", e, i)
+			ep = e
+			found = true
+			break
+		}
+	}
+	if !found {
+		return nil, fmt.Errorf("%s does not have endpoint number %d. Available endpoints: %v", epNum, i.Setting.Endpoints)
+	}
+	return &endpoint{
+		InterfaceSetting: i.Setting,
+		Info:             ep,
+		h:                i.config.dev.handle,
+	}, nil
+}
+
+// InEndpoint prepares an IN endpoint for transfer.
+func (i *Interface) InEndpoint(epNum int) (*InEndpoint, error) {
+	ep, err := i.openEndpoint(epNum)
+	if err != nil {
+		return nil, err
+	}
+	if ep.Info.Direction != EndpointDirectionIn {
+		return nil, fmt.Errorf("%s is not an IN endpoint", ep)
+	}
+	return &InEndpoint{
+		endpoint: ep,
+	}, nil
+}
+
+// OutEndpoint prepares an OUT endpoint for transfer.
+func (i *Interface) OutEndpoint(epNum int) (*OutEndpoint, error) {
+	ep, err := i.openEndpoint(epNum)
+	if err != nil {
+		return nil, err
+	}
+	if ep.Info.Direction != EndpointDirectionOut {
+		return nil, fmt.Errorf("%s is not an OUT endpoint", ep)
+	}
+	return &OutEndpoint{
+		endpoint: ep,
+	}, nil
+}

usb/transfer_stream_test.go

@@ -226,7 +226,7 @@ func TestReadStream(t *testing.T) {
 			got := make([]readRes, len(tc.want))
 			for i := range tc.want {
 				if i == tc.closeBefore-1 {
-					t.Logf("Close()", tcNum)
+					t.Log("Close()")
 					s.Close()
 				}
 				n, err := s.Read(buf)

usb/usb.go

@@ -68,7 +68,7 @@ func (c *Context) ListDevices(each func(desc *Descriptor) bool) ([]*Device, erro
 				reterr = err
 				continue
 			}
-			ret = append(ret, newDevice(handle, desc))
+			ret = append(ret, &Device{handle: handle, Descriptor: desc})
 		} else {
 			libusb.dereference(dev)
 		}