[alsa-devel] Invalid PCM pointer with CMI8738 and pcm.c buffer underuns

andoru andoru.blah at gmail.com
Wed Apr 2 04:24:42 CEST 2014

Raymond Yau wrote:
> >
> > Andoru wrote:
> > > The last time you replied you said that it's a hardware error. If it
> > > is that way then how come the card otherwise works flawlessly in
> > > Windows, and this doesn't happen on Debian when watching videos or
> > > with certain programs?
> The Linux driver seem sharing two Dma channels with at least two playback
> devices and capture device
> The logic seem allow front and rear playing different audio but no capture
> Multi channel playback but no capture
> open three terminals and try different combination of
> speaker-test -c2 -t wav -D front

This gives me: 


Playback device is front
Stream parameters are 48000Hz, S16_LE, 2 channels
WAV file(s)
ALSA lib confmisc.c:768:(parse_card) cannot find card '1'
ALSA lib conf.c:4248:(_snd_config_evaluate) function snd_func_card_driver
returned error: No such file or directory
ALSA lib confmisc.c:392:(snd_func_concat) error evaluating strings
ALSA lib conf.c:4248:(_snd_config_evaluate) function snd_func_concat
returned error: No such file or directory
ALSA lib confmisc.c:1251:(snd_func_refer) error evaluating name
ALSA lib conf.c:4248:(_snd_config_evaluate) function snd_func_refer returned
error: No such file or directory
ALSA lib conf.c:4727:(snd_config_expand) Evaluate error: No such file or
ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM front
Playback open error: -2,No such file or directory

> speaker-test -c2 -t wav -D rear

This gives me the same as above. (except the playback device is "rear" not
"front", as expected)

> arecord -f dat -D plughw:0,0

This just prints a bunch of random characters continiously unless I quit.

> speaker-test -c4 -t wav -D surround40

Same as the first issued command.

> speaker-test -c6 -t wav -D surround51

As expected... same as above.

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