ThinkPad X1 Touchpad

This is a follow-up to my existing blog post on setting a function-key to toggle the touchpad in Ubuntu 18.04 on the ThinkPad X1 Carbon (5th-Gen).

The instructions worked for awhile, but differences between Wayland and Xorg eventually led to it breaking in kernel version 4.15.0-47-generic. I suspect it has something to do with Xorg’s limit on keycodes above 255.

Here are updated instructions for getting a function-key to toggle the touchpad in Ubuntu 18.04 for Xorg!

Find the event device for function-keys

First, we need to find out the device that handles the function-keys on the ThinkPad keyboard. On my system, it’s called "ThinkPad Extra Buttons".

To get more information about the device, run cat /proc/bus/input/devices. A block for "ThinkPad Extra Buttons" should appear among the list of devices:

I: Bus=0019 Vendor=17aa Product=5054 Version=4101
N: Name="ThinkPad Extra Buttons"
H: Handlers=rfkill kbd event6

Take note of event6. It’ll be used in the next section.

Find the scancode for a function-key

In order to remap our function-key, we’ll need its scancode. This is a signal the keyboard sends to the computer indicating it has been pressed.

To get the scancode, we use a utility named evtest on our event device from the previous step, event6. Run sudo evtest /dev/input/event6:

Input driver version is 1.0.1
Input device ID: bus 0x19 vendor 0x17aa product 0x5054 version 0x4101
Input device name: "ThinkPad Extra Buttons"
Testing ... (interrupt to exit)

While evtest is running, press the function-key. In my case, I wanted to remap the “keyboard” function-key (Fn+F11):

Event: time 1555302565.097470, type 4 (EV_MSC), code 4 (MSC_SCAN), value 49
Event: time 1555302565.097470, type 1 (EV_KEY), code 374 (KEY_KEYBOARD), value 1
Event: time 1555302565.097470, -------------- SYN_REPORT ------------
Event: time 1555302565.097517, type 4 (EV_MSC), code 4 (MSC_SCAN), value 49
Event: time 1555302565.097517, type 1 (EV_KEY), code 374 (KEY_KEYBOARD), value 0
Event: time 1555302565.097517, -------------- SYN_REPORT ------------

Take note of the value 49. This is the scancode!

Create a custom hwdb keyboard mapping

Note: It might be worth some time to read up about hwdb.

Armed with the scancode, we create a custom hwdb configuration to map it to our desired keycode. Create a new file in /lib/udev/hwdb.d/ (I named it 90-custom-keyboard.hwdb, but it can be anything):

evdev:name:ThinkPad Extra Buttons:dmi:bvn*:bvr*:bd*:svnLENOVO*:pn*
 KEYBOARD_KEY_49=f21 # tell keycode 49 to toggle touchpad (f21)

The first line is a match-string for our device, "Thinkpad Extra Buttons". The left-hand side of second line is the scancode for our key appended to "KEYBOARD_KEY_". The event, f21, is the “toggle touchpad” keycode.

Note: I found my device match-string and “toggle touchpad” keycode in /lib/udev/hwdb.d/60-keyboard.hwdb.

After saving the new file, run sudo udevadm hwdb --update.

Finally, restart the system and log back in. If things are set up properly, the function-key should toggle the touchpad!


The following links were extremely helpful in getting this working:

Questions? Suggestions? Corrections? Leave me a comment. Cheers!