diff --git a/usb/constants.go b/usb/constants.go
index aec3a0d..9a8f69a 100644
--- a/usb/constants.go
+++ b/usb/constants.go
@@ -105,8 +105,8 @@ func (dt DescriptorType) String() string {
 type EndpointDirection bool
 
 const (
-	EndpointNumMask       = 0x0f
-	EndpointDirectionMask = 0x80
+	endpointNumMask       = 0x0f
+	endpointDirectionMask = 0x80
 	// EndpointDirectionIn marks data flowing from device to host.
 	EndpointDirectionIn EndpointDirection = true
 	// EndpointDirectionOut marks data flowing from host to device.
@@ -129,7 +129,7 @@ const (
 	TransferTypeIsochronous TransferType = C.LIBUSB_TRANSFER_TYPE_ISOCHRONOUS
 	TransferTypeBulk        TransferType = C.LIBUSB_TRANSFER_TYPE_BULK
 	TransferTypeInterrupt   TransferType = C.LIBUSB_TRANSFER_TYPE_INTERRUPT
-	TransferTypeMask                     = 0x03
+	transferTypeMask                     = 0x03
 )
 
 var transferTypeDescription = map[TransferType]string{
@@ -150,7 +150,7 @@ const (
 	IsoSyncTypeAsync    IsoSyncType = C.LIBUSB_ISO_SYNC_TYPE_ASYNC << 2
 	IsoSyncTypeAdaptive IsoSyncType = C.LIBUSB_ISO_SYNC_TYPE_ADAPTIVE << 2
 	IsoSyncTypeSync     IsoSyncType = C.LIBUSB_ISO_SYNC_TYPE_SYNC << 2
-	IsoSyncTypeMask                 = 0x0C
+	isoSyncTypeMask                 = 0x0C
 )
 
 var isoSyncTypeDescription = map[IsoSyncType]string{
@@ -170,7 +170,7 @@ const (
 	// Note: USB3.0 defines usage type for both isochronous and interrupt
 	// endpoints, with the same constants representing different usage types.
 	// UsageType constants do not correspond to bmAttribute values.
-	UsageTypeMask                = 0x30
+	usageTypeMask                = 0x30
 	UsageTypeUndefined UsageType = iota
 	IsoUsageTypeData
 	IsoUsageTypeFeedback
@@ -235,12 +235,8 @@ func (s DeviceSpeed) String() string {
 }
 
 const (
-	// SelfPoweredMask is the bitmask for "self powered" field of configuration
-	// descriptor bmAttributes.
-	SelfPoweredMask = 0x40
-	// RemoteWakeupMask is the bitmask for "supports remote wakeup" field of
-	// configuration descriptor bmAttributes.
-	RemoteWakeupMask = 0x20
+	selfPoweredMask  = 0x40
+	remoteWakeupMask = 0x20
 )
 
 // Milliamperes is a unit of electric current consumption.
diff --git a/usb/libusb.go b/usb/libusb.go
index db6f8e3..e51f496 100644
--- a/usb/libusb.go
+++ b/usb/libusb.go
@@ -40,9 +40,9 @@ 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) != 0),
-		TransferType:  TransferType(ep.bmAttributes & TransferTypeMask),
+		Number:        uint8(ep.bEndpointAddress & endpointNumMask),
+		Direction:     EndpointDirection((ep.bEndpointAddress & endpointDirectionMask) != 0),
+		TransferType:  TransferType(ep.bmAttributes & transferTypeMask),
 		MaxPacketSize: uint32(ep.wMaxPacketSize),
 	}
 	if ei.TransferType == TransferTypeIsochronous {
@@ -52,8 +52,8 @@ func (ep libusbEndpoint) endpointInfo(dev *Descriptor) EndpointInfo {
 		// max packet sizes.
 		// See http://libusb.org/ticket/77 for more background.
 		ei.MaxPacketSize = uint32(ep.wMaxPacketSize) & 0x07ff * (uint32(ep.wMaxPacketSize)>>11&3 + 1)
-		ei.IsoSyncType = IsoSyncType(ep.bmAttributes & IsoSyncTypeMask)
-		switch ep.bmAttributes & UsageTypeMask {
+		ei.IsoSyncType = IsoSyncType(ep.bmAttributes & isoSyncTypeMask)
+		switch ep.bmAttributes & usageTypeMask {
 		case C.LIBUSB_ISO_USAGE_TYPE_DATA:
 			ei.UsageType = IsoUsageTypeData
 		case C.LIBUSB_ISO_USAGE_TYPE_FEEDBACK:
@@ -214,8 +214,8 @@ func (libusbImpl) getDeviceDesc(d *libusbDevice) (*Descriptor, error) {
 		}
 		c := ConfigInfo{
 			Config:       uint8(cfg.bConfigurationValue),
-			SelfPowered:  (cfg.bmAttributes & SelfPoweredMask) != 0,
-			RemoteWakeup: (cfg.bmAttributes & RemoteWakeupMask) != 0,
+			SelfPowered:  (cfg.bmAttributes & selfPoweredMask) != 0,
+			RemoteWakeup: (cfg.bmAttributes & remoteWakeupMask) != 0,
 			// TODO(sebek): at GenX speeds MaxPower is expressed in units of 8mA, not 2mA.
 			MaxPower: 2 * Milliamperes(cfg.MaxPower),
 		}
@@ -374,9 +374,9 @@ 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)
-	addr := ep.Number & EndpointNumMask
+	addr := ep.Number & endpointNumMask
 	if ep.Direction == EndpointDirectionIn {
-		addr |= EndpointDirectionMask
+		addr |= endpointDirectionMask
 	}
 	xfer.endpoint = C.uchar(addr)
 	xfer.timeout = C.uint(timeout / time.Millisecond)