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I have a Dell latop and Ubuntu 12.04. The system will completely hang when I try to adjust the brightness either through the function buttons or through the system's brightness manager module. This hangs the system beyond the REISUB trick, I have to manually shut it down and I've had hard drive warnings because of this.

Brightness adjustment works flawlessly with KDE, so the issue is with the Unity shell.

What can I do about this? Should I just report a bug or is there something I should try first?

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up vote 1 down vote accepted

Apparently this is a known kernel bug . A workaround to your problem is explained in comment #71.

  1. Open the file /etc/defult/grub as root: sudo gedit /etc/default/grub
  2. Change the value of GRUB_CMDLINE_LINUX_DEFAULT to "quiet splash pcie_aspm=force acpi_backlight=vendor"
  3. Update the grub sudo update-grub
  4. And reboot sudo reboot
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Not working in Ubuntu 13.10 :( – mac Mar 1 '14 at 15:25

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