[pulseaudio-discuss] Dealing with the ThinkPad hardware mixer

Tom Gundersen teg at jklm.no
Tue May 24 11:54:59 PDT 2011

On Tue, May 24, 2011 at 8:49 PM, Andrew Lutomirski <luto at mit.edu> wrote:
> 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.

Thanks for the hint!

> 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.)
> http://permalink.gmane.org/gmane.linux.drivers.platform.x86.devel/1941

Do you have a public git repo or something like that? I make a mess
when trying to copy your patch from the webinterface (sorry if there
is a nice way to do this that I do not know about).



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