[pulseaudio-discuss] Dealing with the ThinkPad hardware mixer

Andrew Lutomirski luto at mit.edu
Mon May 23 10:59:55 PDT 2011

On Mon, May 23, 2011 at 1:50 PM, Colin Guthrie <gmane at colin.guthr.ie> wrote:
> 'Twas brillig, and Andrew Lutomirski at 23/05/11 18:21 did gyre and gimble:
>> What is the kernel supposed to do to get PulseAudio to DTRT?  On some,
>> but not (I think) all, models, we can disable hardware mixer control
>> and make all of the buttons act like ordinary buttons, but that will
>> cause the light (if present) to malfunction, and I don't know if all
>> models can do this.  So as it stands, PulseAudio would have to
>> understand that the mixer is special and watch for ALSA change
>> notifications.
>> I'm willing to change the thinkpad-acpi driver to make it work better,
>> but I know nothing at all about PulseAudio internals.  What should I
>> do?
> Can you give some more details?
> e.g. does it show up under the same alsa card as the HDA or is it separate?
> amixer -c0 (or appropriate number) would be useful to begin with :)

It's separate.  I can send details when I get home, but from memory:

alsamixer -c1 sees the HDA mixers.
alsamixer -c29 sees the thinkpad-acpi mixer.

On recent thinkpads with my pending thinkpad-acpi changes, alsamixer
-c29 will update itself when the hardware buttons change the mixer
state.  Without my patches, alsamixer won't notice.

The magic hardware mixer is a created by the thinkpad-acpi driver
without any attempt to associate it with any other ALSA device on the
system.  I suspect that the driver should be doing something different
(and again, I'm willing to make and submit changes, but I don't know
what it should do to make PulseAudio happy).


> Thanks
> Col
> --
> Colin Guthrie
> gmane(at)colin.guthr.ie
> http://colin.guthr.ie/
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