13.04 Upgrade – Brightness not working

Up until yesterday I was running Ubuntu 12.10 on my Dell Latitude E6530. Recently I played around with the nvidia settings, which caused my brightness control to stop working. However, I could fix it by adding Option "RegistryDwords" "EnableBrightnessControl=1" to /etc/X11/xorg.conf as advised in [1].

Now, last night I upgraded to Ubuntu 13.04 because I needed are newer kernel. After that, the brightness control once again stopped working. But this time, [1] doesn't help. I have also tried the methods in [2]:

• acpi_backlight=vendor in /etc/default/grub
• acpi_osi=Linux in /etc/default/grub
• echo $SOME_VALUE | sudo tee /sys/class/backlight/dell_backlight/brightness

None of them are working, the brightness just doesn't change, but that's about all I could find for this problem. Any ideas on how I can get my brightness control back?

[1] https://askubuntu.com/a/270830

[2] https://askubuntu.com/a/289178/213036

I have similar issue with my Sony Vaio. I tried all the methods that you have listed, but there was no effect.

However, in grub, editing lines as follows helped me. (Be sure to backup grub before any editing as a standard practice).

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=legacy" GRUB_CMDLINE_LINUX="acpi_backlight=legacy"

_{Note: We are using acpi_backlight=legacy instead of acpi_backlight=vendor here.}

After saving, run command $ sudo update-grub and reboot your laptop.

Once I did that, the commands cat and tee started working for me to display and change brightness from Terminal.

• This will give you maximum numeric value of brightness that your screen supports.

  $ cat /sys/class/backlight/dell_backlight/max_brightness
  

• This will set your screen brightness value to your specified value, between 0 to max_brightness.

  $ echo <brightness_value> | sudo tee /sys/class/backlight/dell_backlight/brightness
  

For more information, refer to this backlight Wiki.

See my answer here.

The nomodeset kernel parameter may disable the brightness adjustment when used with acpi_backlight=vendor. Remove the former and add the latter.