Comment 2 for bug 810048

The DMI quirk that was the fix for bug 281732 is not in place for the X200s. The DMI quirk should be a last resort though, so let's look for a better fix for the problem first.

First you should try the steps in the "Step-by-step troubleshooting" section of https://wiki.ubuntu.com/Hotkeys/Troubleshooting and report back your observations. Be sure to try the steps in the "Fixing broken keys" section of /usr/share/doc/udev/README.keymap.txt.gz if you don't get any key events from xev.

If you don't find any key events using that technique, try the following. Set your audio to be muted, then execute 'cat /proc/acpi/ibm/volume', then press the mute button and run the command again. Does the reported state change? Try the same thing again, but start with the audio unmuted.

Finally, run 'tail -f /var/log/kern.log', press the mute button, and see if you get any output in response. If you do, please report that output here.

Thanks!