[pulseaudio-discuss] Dealing with the ThinkPad hardware mixer

Andrew Lutomirski luto at mit.edu
Tue May 24 11:49:08 PDT 2011

On Tue, May 24, 2011 at 10:13 AM, Tom Gundersen <teg at jklm.no> wrote:
> 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.

thinkpad_acpi.volume_control=1 will enable it.  I don't know why the
default is the way it is.

If you run my patch, then you'll have a file
/sys/devices/platform/thinkpad_acpi/volume_autocontrol that configures
whether the mute button just mutes the mixer ("latch"), toggles the
mixer state ("toggle"), or sends KEY_MUTE ("none").  Without the
patch, depending on your model and your acpi_osi parameter, you might
have the button mute the mixer *and* send KEY_MUTE or just send
KEY_MUTE.  The former behavior is not so nice.  (My patch also
prevents typematic repeat of the mute button, which is just silly.)



> Cheers,
> Tom
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