Comment 6 for bug 1339998

Please do the test under ubuntu-14.04 as below:

generate a file named 60-dell-mic-mute-hotkey.hwdb and place the file at /etc/udev/hwdb.d/

add the content below into the 60-dell-mic-mute-hotkey.hwdb:
# Dell platform kernel driver
keyboard:name:Dell WMI hotkeys:dmi:bvn*:bvr*:bd*:svnDell*:pn*
 KEYBOARD_KEY_150=f20 # Mic mute toggle

Then run the command below to update the udev database:
sudo udevadm hwdb -u

then re-test mic mute function on this machine or use showkey -k to test

This should fix the mic mute hotkey problem, but it can't help to fix the mic mute led problem, to fix mic mute led problem, it needs kernel driver modification. Let's look at if the above fix can fix the hotkey problem or not.