[pulseaudio-discuss] Mixer connection when switching users

[Tanu Kaskinen]

Hi,

I noticed that my headphone volume wasn't getting restored properly
when plugging in the headphones. The probable cause turned out to be
that gdm's PulseAudio instance was messing with the mixer controls,
causing mixer update events in my own PulseAudio instance.

At the time I logged in, the gdm user lost access to the sound cards,
but Linux doesn't revoke access to file descriptors that are already
open. PulseAudio voluntarily closes the PCM device connections in that
situation, but PulseAudio doesn't close the mixer connection, so gdm
still had access to the mixer, and the jack detection events caused the
gdm to fiddle with the mixer controls.

I will fix this issue, but I'm not sure how I should do that. There
might be some simple fix that would prevent mixer modifications when
the sink suspend cause is PA_SUSPEND_SESSION, but I could also do a
bigger change: close the mixer connection when udev changes the device
permissions. I think it's a bug in itself that we keep the mixer
connection open, even if in practice there's no harm from doing that.
Do others think the same, or should I try to only make a minimal fix,
adding a check somewhere that prevents writes to the mixer when
PA_SUSPEND_SESSION is set?

-- 
Tanu