Cannot change brightness of my laptop

Question

My laptop is a DELL 3521 with dual graphic cards, which usually cause some problems, and I have switched off the AMD Radeon card.

Now, when I want to turn the brightness down by dragging the brightness bar in the "Brightness and lock settings" and I close the window, nothing changes, and when I open "Brightness and Lock Settings" again, the brightness bar turn back to its previous state!

So, is it something is the system or I did some kind of mistake?

Answer 1

Try it once.. It has solved all problems about brightness! Including mine!!

• Open terminal ( Ctrl+Alt+T ) and type:

  sudo gedit /etc/default/grub
  

  You will find this line in the new opened window: GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"

• Change it to:

  GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor"
  

• Save and close the window and type this in the terminal:

  sudo update-grub
  

• Restart your system..