Linux ThinkPad T16 Microphone "Muted" Indicator

This laptop's keyboard has an indicator on the F4 key, which also serves as the mic mute toggle key.

Frustratingly, in Debian 12 ("bookworm") with pipewire audio, the LED doesn't actually follow the mic mute state. This appears to be because pipewire doesn't mute the mic at the hardware level, so setting the corresponding LED's "trigger" to "audio-micmute" does nothing.

I don't know what the proper solution for this is, but I implemented a solution of my own and it seems to work.

First, the LED control file (in my case "/sys/devices/platform/thinkpad_acpi/leds/platform::micmute/brightness") has to be made writable by my user (I don't care about multi-user situations). I did this by making a boot-time cron job as root:

@reboot chown jepler.jepler  /sys/devices/platform/thinkpad_acpi/leds/platform::micmute/brightness

Second, I have to run a script that watches the PulseAudio mic mute status and updates the LED. It's shown at the bottom of this blog post. It requires python3 and the pulsectl library, installable via pip.

I start this script in the background at login time. In my case I do this via the ".xsession" script, but you will need to know the correct way to do it in your desktop environment.

Now, when I press the mute key, Fn-F4, the LED's state follows the mute state.