[pulseaudio-discuss] Dealing with the ThinkPad hardware mixer

[Tom Gundersen]

I don't know much about this, but since there might be differences
between different models, I'll add my two cents. I have a ThinkPad
X60.

On Tue, May 24, 2011 at 7:39 AM, David Henningsson
<david.henningsson at canonical.com> wrote:
> On 2011-05-23 19:21, Andrew Lutomirski wrote:
>> Most ThinkPad laptops have an extra mixer that has nothing to do with
>> the HDA audio hardware.  The kernel can talk to it through the
>> embedded controller and, if it's muted, then there's no sound even if
>> the normal controls are all set on.
>
> Does this concern the internal speaker only, or headphones / line out as
> well? Or can that differ between models? I'm assuming it doesn't mute e g
> USB headset or audio out over HDMI.

The buttons affect both the speakers and headset. When the headest is
connected the speaker is muted (I don't know if this is done in
software or in hardware, but I always assumed it was done in hardware
as it always worked this way). I never tried usb headset, and don't
have HDMI.

>> 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.
>
> So, what can the thinkpad-acpi driver do here? Can it e g control the
> hardware mute status at all, or can that only be done by pressing the keys?

At least on my laptop alsamixer can not set the volume/mute of -c29,
this can only be done by the buttons.

Cheers,

Tom