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

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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>
This commit is contained in:
Daniel Girnus 2016-12-06 14:46:15 +09:00 committed by Takashi Iwai
parent 4763601a56
commit 1e2e3fe480
1 changed files with 11 additions and 10 deletions
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21
sound/usb/pcm.c
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@ -806,17 +806,18 @@ static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream)
if (ret < 0)
goto unlock;
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,
subs->cur_audiofmt->iface,
alts,
subs->cur_audiofmt,
subs->cur_rate);
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,
subs->cur_audiofmt->iface,
alts,
subs->cur_audiofmt,
subs->cur_rate);
if (ret < 0)
goto unlock;
ret = configure_endpoint(subs);
if (ret < 0)
goto unlock;