From c347e9fca710551f0def6a4d58505a6f4c0d87f6 Mon Sep 17 00:00:00 2001 From: Clemens Ladisch Date: Thu, 25 Aug 2005 11:10:05 +0200 Subject: [PATCH] [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 --- sound/usb/usbmidi.c | 17 ++++++++++++----- 1 file 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; } -- GitLab