Brightness function keys not working [duplicate]

I have an ASUS X55A-SPD0204O laptop. The rest of the FN+Fx (where x = number) like sound + - mute, screen turn off, wireless etc. work perfectly.

The problem is with the 2 brightness keys. They just won't work. Any suggestions?

Solution 1:

Try adding acpi_backlight=vendor as a boot option. To do that, open a terminal window, and run

gksu gedit /etc/default/grub

Locate this line: GRUB_CMDLINE_LINUX="".

Edit it to look like this: GRUB_CMDLINE_LINUX="acpi_backlight=vendor"

Save the file, then, in a terminal, run sudo update-grub.

Reboot, and check if the brightness keys work.

Solution 2:

You can try to control it from command line and give mesage back if this works in general:

You will need xrandr

xrandr --current --verbose - this will display your current display mode / modes

important is name of your output (clould be LVDS1 or LVDS-0)

xrandr --output <outputname> --brightness 0.5 - this should control your brightnes, you can try different values. Do not use zero (0) what means lamp is switched off and you will see Big nothing. be careful, some types of devices have completely different set of values (as 0-255, etc. Unfortunatelly I do not have your ASUS to test it)

This will work probably independently of the brightness settings reachable normally via keys. If this works, I recommend to watch for key bindings. Advantage is, you can control brightness of external VGA output as well.