Introduce two more layers between device and endpoint:

device -> active config -> claimed interface -> endpoints.
Device can have at most one active config. A config can have
multiple claimed interfaces, each with a specific alt setting.
An interface with an alt setting defines a list of endpoints.

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()