Comment # 15 on bug 1193644 from Michal Suchanek

I don't think that there is a problem with detecting the plug/unplug in
general. There might be a problem with detecting it while the machine is
suspended.

I don't know which component is responsible for changing the levels when
plug/unplug happens. 

However, the level change is generally correct, what is not correct is
projecting this level change to the hardware state - when headphones are muted
speaker is also muted, speaker uses headphone level which is set to 0 when
headphones are unplugged.

The other thing that is not correct is that muting something causes something
else to mute, and unmuting anything does not cause anything else to unmute.