Brightness keys F4 and F5 not working on Dell XPS 15.6 Laptop

Question

Please provide me a solution how to fix this?

Solution

Edit "/etc/default/grub" as root.

gksu gedit /etc/default/grub

Now, look for the line that looks like:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"

Append "acpi_backlight=vendor acpi_osi=Linux" to the end of that line, before the end quotes, so that the line now looks something like this:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor acpi_osi=Linux"

Save and close the file, and run the following command:

sudo update-grub

Now, reboot, and test out the brightness keys. They should be working correctly now.

Comments

[SirCharlo]

Do you have proprietary graphics drivers installed?

[Eliah Kagan]

@SirCharlo A laptop's backlight is not controlled by the graphics card or graphics drivers.

[Rahul]

I didnt check ur solution,because the above one worked....still anyways thanks for the effort :)

[Rob Hyndman]

That leaves my screen flickering unless it is on full brightness.

[Vic]

I have Dell Inspiron 7520, this solved my problem, but the system became unstable. The brightness controls had some delay before actually changing the brightness, also when I pressed some brightness button the reaction was as if I pressed it twice. When I pressed those buttons quickly and chaotically the system could stuck, the mouse pointer speed reduced and the KDE even logged me off. So very weird behavior.