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I've got a fresh install of trusty (xubuntu if that matters, I don't think it should) on a Asus X551MAV-EB01-B. My function keys for brightness don't work. Here's what I know so far:

If I pass acpi_osi= or acpi_osi=! to grub I can get the brightness and wifi keys to work (I know this because I can see the OSD for brightness change), BUT:

in /sys/class/backlight I have two items:

acpi_video0 -> ../../devices/pci0000:00/0000:00:02.0/backlight/acpi_video0
intel_backlight -> ../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-eDP-1/intel_backlight

With cat I can see the brightness keys are adjusting acpi_video0/brightness and not intel_backlight/brightness.

I've also tried passng acpi_backlight=vendor to grub, and if I do that, then I end up with this : 

asus-nb-wmi -> ../../devices/platform/asus-nb-wmi/backlight/asus-nb-wmi/
intel_backlight -> ../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-eDP-1/intel_backlight

acpi_backlight=vendor also stops the brightness keys from responding at all.

For now, I've set up an echo in /etc/rc.local to change the brightness a few seconds after lightdm starts... but where do I go from here?

Dr. JKL
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4 Answers4

1

I've been using this (self-made) script for quite some time on my NVidia card and works fine. If @TheSchwa's solution doesn't work try this.

Install the script:

  1. Open a Terminal
  2. Type: sudo apt-get install -y inotify-tools and press Enter
  3. Type: sudo nano /usr/local/bin/backlight-sync and press Enter
  4. Copy the script from this page (has been adopted for your intel card already)
  5. Paste it into the Terminal window using Ctrl+Shift+V
  6. Press: Ctrl+X
  7. Press: y
  8. Press: Enter
  9. Type: sudo chmod a+x /usr/local/bin/backlight-sync and press Enter

Test the script:

  1. In the Terminal type sudo backlight-sync and press Enter
  2. Change your screen brightness at least once to see if its working
  3. Press Ctrl+C to quit

Enable the script during boot:

  1. In the Terminal type: sudo nano /etc/rc.local and press Enter
  2. Use the arrow keys to navigate above the line that says exit 0
  3. Type: /usr/local/bin/backlight-sync &
  4. Press: Ctrl+X
  5. Press: y
  6. Press: Enter
  7. Close the Terminal window
ntninja
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0

I had the same problem on a Dell Studio laptop, which also uses intel_backlight. While I'm not sure if this will work on Asus, I think it's worth a shot. See if the answer to this question helps.

Community
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TheSchwa
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0

This worked for me.

Add to /etc/rc.local

echo N | sudo tee /sys/module/video/parameters/brightness_switch_enabled

Reboot

user301845
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-1

Try video.use_native_backlight=1.

Eliah Kagan
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Craig
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