chromekey

Remap function keys to Chromebook media keys on Linux. This program uses evdev and uinput to perform the key mapping at close to kernel level. It is more flexible than HWDB scancode mapping. Unlike XKB mappings, this program work in the Linux console and the GDM login screen.

Features:

1. Default mapping of function key to the original Chromebook media keys

   1. Press the FN key to toggle the FN locked mode

   2. Press FN+key to select the second level alternate key

2. Support third-level key mapping with FN+Shift+key combinations

   1. FN+Shift+brightness up/down control keyboard backlights

3. Optionally take over an keyboard LED as the FN key lock LED.

Build the binary

Install the Go SDK

Download the Go SDK from the Downloads page.

Following the install instructions.

Download the Go modules

go mod download

Build with cgo

go build

Build without cgo

In case you don't have the C headers for cgo, you can build the pure Go version.

CGO_ENABLED=0 go build

Configuration

First pick a key as the FN key. I don't use the Lock key (at the upper left corner) on my Chromebook, so I turned it into the FN key.

Create a default configuration file with the -dump_config flag.

./chromekey -dump_config > chromekey.config

Use the -show_key flag to find key names

Stop any running instance to release the grab on the keyboard device first.

./chromekey -show_key

FN key configuration snippet

fn_key:  KEY_F13

Set the FN lock state on start up

fn_enabled: true

Set third-level keys for FN+Shift+ key maps

third_level_key:  KEY_LEFTSHIFT
third_level_key:  KEY_RIGHTSHIFT

Map third-level keys for keyboard backlight

Use FN+Shift+F6/F7 for keyboard backlight adjustment:

third_level_key_map:  {
  from:  KEY_F6
  to:  KEY_KBDILLUMDOWN
}
third_level_key_map:  {
  from:  KEY_F7
  to:  KEY_KBDILLUMUP
}

Add additional key map that uses the FN key as a modifier

For example, press FN+backspace to send the DELETE key:

mod_key_map:  {
  from:  KEY_BACKSPACE
  to:  KEY_DELETE
}

Optional: Use the Num Lock LED as the FN Lock LED

NOTE: Don't use this option if you have an external USB keyboard with a numpad.

use_led: NUML

Installation

Copy the binary to /usr/local/bin

sudo cp ./chromekey /usr/local/bin

Copy the configuration file to /usr/local/etc

sudo cp chromekey.config /usr/local/etc/

Add a simple systemd service unit file

sudo tee /etc/systemd/system/chromekey.service <<EOF
[Service]
Type=simple
ExecStart=/usr/local/bin/chromekey -config_file=/usr/local/etc/chromekey.config
EOF

Add a udev rule to trigger the systemd service

sudo tee /etc/udev/rules.d/99-chromekey.rules <<EOF
ACTION=="add", ATTRS{name}=="AT Translated Set 2 keyboard", TAG+="systemd", ENV{SYSTEMD_WANTS}="chromekey.service"
EOF

Optional: Install the bash completion file

sudo cp config/chromekey.completion /etc/bash_completion.d/chromekey

Nice Addition

Install a Lock Keys Gnome Shell extension to show LED status on screen.