[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: Clemens Ladisch <clemens@ladisch.de>
diff --git a/sound/usb/usbmidi.c b/sound/usb/usbmidi.c
index d0d895df..5f19b49 100644
--- a/sound/usb/usbmidi.c
+++ b/sound/usb/usbmidi.c
@@ -594,17 +594,20 @@
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 @@
break;
}
}
+ if (buf_free < ep->max_transfer && buf_free > 0) {
+ *buf = 0xff;
+ --buf_free;
+ }
ep->urb->transfer_buffer_length = ep->max_transfer - buf_free;
}