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System: Dell N4110 Ubuntu ver: Oneric

My /sys/class/backlight has two entries acpi_video0 and intel_backlight? Is it normal to have two entries here?

When I try to change the screen brightness using Fn + Brightness, the brightness changes with uneven steps. I'm suspecting the dual entries in the /sys/class folder is pointing to some issues?

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It's likely that you have a newer Intel Sandy bridge processor in the Dell which has integrated graphics as well as a graphics card - that is the reason for the two entries in your /sys/class/backlight folder.

You can do two things - disable one of the graphics cards via the bios settings and see if it solves the problem or you can follow the instructions in this Ubuntu Forums post to blacklist one of the entries.

My first option would be to disable via bios and see if it is acceptable.

  • I couldn't find the BIOS setting to disable the graphics card. I'll give the second option a try. – sauravrt Mar 8 '12 at 19:53
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You can try this:

Edit the following file as root:

/etc/default/grub

GRUB_CMDLINE_LINUX="acpi_backlight=vendor"

Then as root run:

/usr/sbin/update-grub

Then reboot and your brightness keys should function as expected.

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