Comment 13 for bug 1268880

I think I found where the problem started:

I tried different Kernels on my 14.04 devel. branch.
Check with acpi_listen if signal gets catched. This is the result:

kernel version | acpi_listen can see mic mute
------------------------------------------------------
3.11.0 | yes
3.11.9 | yes
3.11.10.4 | yes
3.11.10.6 | yes
3.12.0-031200rc1 | no
3.12.0-031200rc2 | no
3.12.0-031200rc4 | no
3.12.0 | no

So I guess the problem occured first at 3.12.0 rc 1

But the thing is that even if I get the signal (till 3.11.10.6) Ubuntu does not react to this... Is this another issue?