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

[Glenn Golden]

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.

Before filing a ticket with the kernel guys, wanted to ask if this
function-LED binding is in any way under control of pulseaudio itself?
In other words, I guess what I'm asking is whether pulseaudio just tells
the driver to "mute the audio", and the driver sets the LED state accordingly,
or whether pulse tells the driver separately to "mute the audio" and also
"turn on the LED".

Knowing the answer to this, I can post a more informative ticket to the
kernel guys. (Or maybe the fix is even in pulseaudio itself?)