Screen Brightness in Arch

This guide tells us how we can configure laptop Fn keys to control laptop screen brightness. The following steps is tested on a Lenovo Thinkpad T460.

Setting Screen Brightness

We can set screen brightness by manipulating the content of a system file /sys/class/backlight/intel_backlight/brightness. You can find more details here.

Only root user is allowed to manipulate this file. To allow users in video usergroup to make changes to this file, we can add the following udev rule in /etc/udev/rules.d/backlight.rules:

RUN+="/bin/chgrp video /sys/class/backlight/intel_backlight/brightness"
RUN+="/bin/chmod g+w /sys/class/backlight/intel_backlight/brightness"

With the above in place, we should be able to edit the integer in /sys/class/backlight/intel_backlight/brightness, and the screen brightness should change accordingly.

Write a Script

Write a script so that we can run it with options (e.g. -inc, -dec) to increase/descrease screen brightness. For example, ./brightness.sh -inc.

Keybinding

First, find out what keycode is assoicated with the brightness Fn keys. We can run the following to capture the keycode of keyboard events.

xev -event keyboard

We can now bind the keycode with the script from before. For my case, I am using i3wm, so I could do this by adding the following:

bindcode 232 exec ~/.config/abrightness/abrightness.sh -dec
bindcode 233 exec ~/.config/abrightness/abrightness.sh -inc

Other Notes

Using xorg-xbacklight might be a good approach as well. See here. However, the xbacklight command did not work for my case -- after running the command, nothing happens at all (not even an error mesasge).