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

[Raymond Yau]

>
> I've previously posted under ALSA's user mailing list so to avoid the
> clutter, the details about what's happening is here:
> http://article.gmane.org/gmane.linux.alsa.user/38258
> http://article.gmane.org/gmane.linux.alsa.user/38260
>
> There was no debug info under /proc/asound/card0/ so nothing to give from
> there unless you guys need something specific.
>
> Output of alsa-debug.sh:
> http://www.alsa-project.org/db/?f=26187faadd47f3626029ba667cb004e74695f2b2

https://git.kernel.org/cgit/linux/kernel/git/tiwai/sound.git/commit/sound/pci/cmipci.c?id=1c583063a5c769fe2ec604752e383972c69e6d9b

Seem cannot read valid value from register within three trials

state.CMI8738 {
control.1 {
iface PCM
device 2
name 'Playback Channel Map'
value.0 0
value.1 0
value.2 0
value.3 0
value.4 0
value.5 0
comment {
access read
type INTEGER
count 6
range '0 - 36'
}
}

Seem bug in adding channel map to iec958 instead of analog

https://git.kernel.org/cgit/linux/kernel/git/tiwai/sound.git/commit/sound/pci/cmipci.c?id=f49921b894ec338696e47d985acc09df3cddbfd1

pcm.!default {
    type plug
    slave.pcm "dmixer"
}

You need asym plugin for playback and capture when overwrite pcm.default