Replace EndpointDirection with a bool

usb/config.go

@@ -46,8 +46,12 @@ type EndpointInfo struct {
 
 // String returns the human-readable description of the endpoint.
 func (e EndpointInfo) String() string {
+	addr := e.Number
+	if e.Direction == EndpointDirectionIn {
+		addr |= 0x80
+	}
 	ret := make([]string, 0, 3)
-	ret = append(ret, fmt.Sprintf("Endpoint #%d %s (address 0x%02x) %s", e.Number, e.Direction, uint8(e.Number)|uint8(e.Direction), e.TransferType))
+	ret = append(ret, fmt.Sprintf("Endpoint #%d %s (address 0x%02x) %s", e.Number, e.Direction, addr, e.TransferType))
 	switch e.TransferType {
 	case TransferTypeIsochronous:
 		ret = append(ret, fmt.Sprintf("- %s %s", e.IsoSyncType, e.UsageType))

usb/constants.go

@@ -22,6 +22,7 @@ import "strconv"
 // Class represents a USB-IF class or subclass code.
 type Class uint8
 
+// Standard classes defined by USB spec.
 const (
 	ClassPerInterface Class = C.LIBUSB_CLASS_PER_INTERFACE
 	ClassAudio        Class = C.LIBUSB_CLASS_AUDIO
@@ -67,8 +68,10 @@ func (p Protocol) String() string {
 	return strconv.Itoa(int(p))
 }
 
+// DescriptorType identifies the type of a USB descriptor.
 type DescriptorType uint8
 
+// Descriptor types defined by the USB spec.
 const (
 	DescriptorTypeDevice    DescriptorType = C.LIBUSB_DT_DEVICE
 	DescriptorTypeConfig    DescriptorType = C.LIBUSB_DT_CONFIG
@@ -97,13 +100,17 @@ func (dt DescriptorType) String() string {
 	return descriptorTypeDescription[dt]
 }
 
-type EndpointDirection uint8
+// EndpointDirection defines the direction of data flow - IN (device to host)
+// or OUT (host to device).
+type EndpointDirection bool
 
 const (
-	EndpointNumMask                         = 0x0f
-	EndpointDirectionMask                   = 0x80
-	EndpointDirectionIn   EndpointDirection = C.LIBUSB_ENDPOINT_IN
-	EndpointDirectionOut  EndpointDirection = C.LIBUSB_ENDPOINT_OUT
+	EndpointNumMask       = 0x0f
+	EndpointDirectionMask = 0x80
+	// EndpointDirectionIn marks data flowing from device to host.
+	EndpointDirectionIn EndpointDirection = true
+	// EndpointDirectionOut marks data flowing from host to device.
+	EndpointDirectionOut EndpointDirection = false
 )
 
 var endpointDirectionDescription = map[EndpointDirection]string{

usb/libusb.go

@@ -41,7 +41,7 @@ type libusbEndpoint C.struct_libusb_endpoint_descriptor
 func (ep libusbEndpoint) endpointInfo(dev *Descriptor) EndpointInfo {
 	ei := EndpointInfo{
 		Number:        uint8(ep.bEndpointAddress & EndpointNumMask),
-		Direction:     EndpointDirection(ep.bEndpointAddress & EndpointDirectionMask),
+		Direction:     EndpointDirection((ep.bEndpointAddress & EndpointDirectionMask) != 0),
 		TransferType:  TransferType(ep.bmAttributes & TransferTypeMask),
 		MaxPacketSize: uint32(ep.wMaxPacketSize),
 	}
@@ -374,7 +374,11 @@ func (libusbImpl) alloc(d *libusbDevHandle, ep *EndpointInfo, timeout time.Durat
 		return nil, fmt.Errorf("libusb_alloc_transfer(%d) failed", isoPackets)
 	}
 	xfer.dev_handle = (*C.libusb_device_handle)(d)
-	xfer.endpoint = C.uchar(uint8(ep.Number&EndpointNumMask) | uint8(ep.Direction&EndpointDirectionMask))
+	addr := ep.Number & EndpointNumMask
+	if ep.Direction == EndpointDirectionIn {
+		addr |= EndpointDirectionMask
+	}
+	xfer.endpoint = C.uchar(addr)
 	xfer.timeout = C.uint(timeout / time.Millisecond)
 	xfer._type = C.uchar(ep.TransferType)
 	xfer.num_iso_packets = C.int(isoPackets)