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authorClemens Ladisch <clemens@ladisch.de>2005-08-25 11:10:05 +0200
committerJaroslav Kysela <perex@suse.cz>2005-08-30 08:47:34 +0200
commitc347e9fca710551f0def6a4d58505a6f4c0d87f6 (patch)
tree7a581a03569249bd70d9dbba96966d94d9e96a9e /sound/usb
parenta278655ff5d0c9d5eb34cf99f3a4c20da09eb09e (diff)
[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>
Diffstat (limited to 'sound/usb')
-rw-r--r--sound/usb/usbmidi.c17
1 files changed, 12 insertions, 5 deletions
diff --git a/sound/usb/usbmidi.c b/sound/usb/usbmidi.c
index d0d895df5375..5f19b494923e 100644
--- a/sound/usb/usbmidi.c
+++ b/sound/usb/usbmidi.c
@@ -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;
}