Set the MaxIsoPacket field in the endpoint info if the endpoint is

an isochronous endpoint. Use MaxIsoPacket as the iso packet size
when preparing the iso transfer.

usb/iso.go

@@ -37,10 +37,8 @@ func iso_callback(cptr unsafe.Pointer) {
 }
 
 func (end *endpoint) allocTransfer() *Transfer {
-	// Use libusb_get_max_iso_packet_size ?
 	const (
-		iso_packets = 8       // 128 // 242
-		packet_size = 2 * 960 // 1760
+		iso_packets = 8 // 128 // 242
 	)
 
 	xfer := C.libusb_alloc_transfer(C.int(iso_packets))
@@ -49,7 +47,7 @@ func (end *endpoint) allocTransfer() *Transfer {
 		return nil
 	}
 
-	buf := make([]byte, iso_packets*packet_size)
+	buf := make([]byte, iso_packets*end.EndpointInfo.MaxIsoPacket)
 	done := make(chan struct{}, 1)
 
 	xfer.dev_handle = end.Device.handle
@@ -60,7 +58,7 @@ func (end *endpoint) allocTransfer() *Transfer {
 	xfer.length = C.int(len(buf))
 	xfer.num_iso_packets = iso_packets
 
-	C.libusb_set_iso_packet_lengths(xfer, packet_size)
+	C.libusb_set_iso_packet_lengths(xfer, C.uint(end.EndpointInfo.MaxIsoPacket))
 	/*
 		pkts := *(*[]C.struct_libusb_packet_descriptor)(unsafe.Pointer(&reflect.SliceHeader{
 			Data: uintptr(unsafe.Pointer(&xfer.iso_packet_desc)),