Commit c347e9fc authored by Clemens Ladisch's avatar Clemens Ladisch Committed by Jaroslav Kysela
Browse files

[ALSA] usb-audio: fix Emagic MIDI protocol handling 



USB generic driver
Emagic devices pad their packets not with 0xff bytes but with a 0xff
byte followed by garbage, so we have to stop at the first such byte.

Signed-off-by: default avatarClemens Ladisch <clemens@ladisch.de>
parent a278655f

sound/usb/usbmidi.c

+12 −5
Original line number Diff line number Diff line
@@ -594,17 +594,20 @@ static void snd_usbmidi_emagic_finish_out(snd_usb_midi_out_endpoint_t* ep) 
static void snd_usbmidi_emagic_input(snd_usb_midi_in_endpoint_t* ep,

				     uint8_t* buffer, int buffer_length)

{

	/* ignore padding bytes at end of buffer */

	while (buffer_length > 0 && buffer[buffer_length - 1] == 0xff)

		--buffer_length;

	int i;



	/* FF indicates end of valid data */

	for (i = 0; i < buffer_length; ++i)

		if (buffer[i] == 0xff) {

			buffer_length = i;

			break;

		}



	/* handle F5 at end of last buffer */

	if (ep->seen_f5)

		goto switch_port;



	while (buffer_length > 0) {

		int i;



		/* determine size of data until next F5 */

		for (i = 0; i < buffer_length; ++i)

			if (buffer[i] == 0xf5)
@@ -671,6 +674,10 @@ static void snd_usbmidi_emagic_output(snd_usb_midi_out_endpoint_t* ep) 
				break;

		}

	}

	if (buf_free < ep->max_transfer && buf_free > 0) {

		*buf = 0xff;

		--buf_free;

	}

	ep->urb->transfer_buffer_length = ep->max_transfer - buf_free;

}