Commit 1e2e3fe4 authored Dec 06, 2016 by Daniel Girnus Committed by Takashi Iwai Dec 06, 2016

ALSA: usb-audio: avoid setting of sample rate multiple times on bus



Some of userland applications call 'snd_pcm_hw_params()' and
'snd_pcm_hw_prepare()' sequentially, which means 'snd_pcm_hw_prepare()'
is called twice and the second 'snd_pcm_hw_prepare()' is called in
'SNDRV_PCM_STATE_PREPARED' state.

Some devices are not able to manage this and they will stop playback
if the sample rate will be configured several times over USB protocol.

V2: updated Changelog

Signed-off-by: Daniel Girnus <dgirnus@de.adit-jv.com>
Signed-off-by: Jens Lorenz <jlorenz@de.adit-jv.com>
Signed-off-by: Jiada Wang <jiada_wang@mentor.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

parent 4763601a

sound/usb/pcm.c

+11 −10

Original line number	Diff line number	Diff line
		@@ -806,6 +806,8 @@ static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream)
		if (ret < 0)
		goto unlock;

		if (subs->need_setup_ep) {

		iface = usb_ifnum_to_if(subs->dev, subs->cur_audiofmt->iface);
		alts = &iface->altsetting[subs->cur_audiofmt->altset_idx];
		ret = snd_usb_init_sample_rate(subs->stream->chip,
		@@ -816,7 +818,6 @@ static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream)
		if (ret < 0)
		goto unlock;

		if (subs->need_setup_ep) {
		ret = configure_endpoint(subs);
		if (ret < 0)
		goto unlock;