HP ZBook 15u mic mute button doesn't work

This is mostly similar to this one:
https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1334968

I have an HP Zbook 15u laptop with a mic mute button at fn+f8. I didn't work for me with xubuntu LTS 14.04.03

What is wished: keyboard shortcut fn+f8 should produce XF86AudioMicMute X key code which mutes microphone.
What is happening: keyboard shotcut has keycode 465 which does nothing, while muting microphone through GUI enables led on the keyboard.

How to debug similar issues and fix:
Enable keyboard debug, find your scancode, remap it to f20, restart X.

Now in step by step instruction:
NB: keyboard sends scancodes, kernel makes keycodes from those. Keycodes are remapped in X before getting into applications

1) enable keyboard debug to make things easier: edit /etc/default/grub, add the following options
GRUB_CMDLINE_LINUX="atkbd.softraw=0", Reboot to enable this.
2) install "evtest" utility
3) using "evtest" find your keyboard (was /dev/input/event3 for me)
4) look for the key down and key up scancodes for fn+f8 button. Fixed version looks like this:
Event: time 1453101052.604985, -------------- SYN_REPORT ------------
Event: time 1453101053.883744, type 4 (EV_MSC), code 3 (MSC_RAW), value e0
Event: time 1453101053.883744, type 4 (EV_MSC), code 3 (MSC_RAW), value 01
Event: time 1453101053.883744, type 4 (EV_MSC), code 4 (MSC_SCAN), value 81
Event: time 1453101053.883744, type 1 (EV_KEY), code 190 (KEY_F20), value 1
Event: time 1453101053.883744, -------------- SYN_REPORT ------------
Event: time 1453101053.955411, type 4 (EV_MSC), code 3 (MSC_RAW), value e0
Event: time 1453101053.955411, type 4 (EV_MSC), code 3 (MSC_RAW), value 81
Event: time 1453101053.955411, type 4 (EV_MSC), code 4 (MSC_SCAN), value 81
Event: time 1453101053.955411, type 1 (EV_KEY), code 190 (KEY_F20), value 0

the "code 190 (KEY_F20)" will be different for you.

5) using "eventX" from the above, find corresponding device using "find /sys/ -name event3".
6) find out udev modalias for your keyboard: "udevadm --debug test /devices/platform/i8042/serio0/input/input3/event3 2>&1 | grep dmi/id", The long path is from p.5 'find' output
7) create and change /etc/udev/hwdb.d/60-hp-mic-mute-hotkey.hwdb file. Add following lines there:
keyboard:dmi:bvnHewlett-Packard:bvrM71Ver.01.07:bd07/28/2015:svnHewlett-Packard:pnHPZBook15uG2:pvrA3009D510303:rvnHewlett-Packard:rn2216:rvrKBCVersion96.55:cvnHewlett-Packard:ct10:cvr:
 KEYBOARD_KEY_81=f20
The long identifier is from udevadm point 6 output. "81" is the scan code. f20 - is an alias for the keycode we wish to have (can be replaced with '190' keycode itself)
8) udevadm hwdb --update; udevadm trigger /dev/input/event3
9) test with evtest that you have appropriate keycode for the button. To make it work in X11 you have to restart X (or reboot, don't know for sure)
10) test with xev after reboot: fn+f8 should work as intended this time. (xmodmap maps f20 to XF86AudioMicMute).
11) for xfce4 you might need to map XF86AudioMicMute to a pactl action, but this is xfce specific.

For the maintainers:
Mose of HPProBooks, EliteBooks, ZBooks has the same issue. Could anyone contact HP and request some help with all those keyboards?...

Please, add ZBook into keyboard.hwdb file.