[pulseaudio-discuss] ThinkPad T-510 audio output mute LED non-workingness

Glenn Golden gdg at zplane.com
Sat Apr 4 20:17:43 PDT 2015

Raymond Yau <superquad.vortex2 at gmail.com> [2015-04-05 09:47:36 +0800]:
> >
> > HW: ThinkPad T-510, x86_64
> > SW: Arch Linux (synched within a week) kernel = 3.19.2, PA 6.0
> >
> > On the above setup, the mic mute function (invoked via pavucontrol) works
> > as expected: Click the mute icon, it mutes the mic input, indicates the
> > muted state by greying out the pavucontrol mic gain control, and
> > illuminates the little LED on the mic mute button.
> >
> > But the analogous functionality for muting audio output only does the
> > first two things, and has no effect on the mute LED. (The LED is always
> > off.)
> >
> > From googling around, I'm pretty sure that these two particular LEDs are
> > not directly under user control (e.g. via ACPI) but are somehow bound to 
> > the mute/unmute functionality in the snd-hda-intel driver. This
> > understanding is based on kernel posts like this:
> >
> >     https://bugzilla.kernel.org/show_bug.cgi?id=49391
> >
> > and other similar ones.
> The above report seem has no relationship with your problem, the laoptop
> has dual headphone jacks, four speakers and subwoofers

I didn't say that report (or the laptop it pertains to) had anything directly
to do with the problem being reported here.

All I said was that post (and others similar) led me to believe -- see
comments #7, #8, and #11 there -- that the mute LEDs are probably controlled
by the snd-hda-intel driver itself, rather than under userspace control. 
That in turn suggested that the problem was most likely a kernel driver issue
and unrelated to pulseaudio. I was asking the question here just to verify
that understanding before filing a kernel bug report.

Based on the follow-on comments here by Hui and David, it seems that
understanding was correct; it is a kernel issue, so I filed a report on LKML.

> https://bugs.launchpad.net/ubuntu/+source/udev/+bug/408903
> If your mic mute  generate keypress event and key release event, you need
> pulseaudio also listen to those event to update the status of mic mute icon
> in pavucontrol

The problem I reported is not related in any way to keypress events of the
mute keys (or any others).  It is only concerned with the "audio mute" and
"mic mute" indicator LEDs.

As I said early in the post, I was toggling the mute functionality not via 
the mute keys, but via pavucontrol itself. The functionality of both types of
mute operation was confirmed: Toggling the output mute control via pavucontrol
indeed toggled the audio output signal, and togglng the mic mute control
likewise toggled the mic input signal. And both flavors of muting were
accompanied by the expected greying-out of the associated pavucontrol sliders.

The problem is that the audio output mute _LED_ does not toggle with the
output mute state of the driver. (The mic mute LED does toggle with the mic
input mute state.)

I'm aware that in 3.19 kernel, the audio output mute and mic mute keys were
changed from direct driver control of the mute function to ordinary softkeys,
which are under userspace control; I think this might be what you were getting
at in your comment above. But this has nothing to do with the reported issue.

Hope this helps to understand. Thanks for your time in replying in any case.

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