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I have installed Lubuntu on my Dell Chromebook 11 and everything works except for the backlight. Can't set the backlight with the brightness keys, neither with xbacklight,xdotool or any other GUI tool.

I tried with a combination of grub options like acpibacklight=vendor acpiosi=Linux, acpibacklight=legacy acpiosi=Linux, acpibacklight=vendor acpiosi= and acpibacklight=legacy acpiosi= without success. Even more strange is that /sys/class/backlight/ is empty.

  • dmidecode - http://pastebin.com/hBJxuVvY

  • acpi (grep -r . /proc/acpi) - http://paste.ubuntu.com/9880798/

  • acpidump - paste.ubuntu.com/9880816/

  • results.log (fwts) - paste.ubuntu.com/9880883/

  • video (dmesg | grep 'ACPI: Video') - paste.ubuntu.com/9880928/

  • version (cat /proc/version) - paste.ubuntu.com/9880942/

Does that give any useful information on the issue?

Given that the VGA Graphic hardware is at the addres 00:02.0 I tried to set its register values manually like this setpci -s 00:02.0 F4.B=30 without success as the backlight stays the same. Shouldn't this work on every device given that it interfaces directly to the hardware?

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  • What graphics card is it?
    – rogerdpack
    Jun 18, 2019 at 6:12

1 Answer 1

Reset to default
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If /sys/class/backlight/ is empty, that means that the kernel thinks you have a big bad old CRT attached to the system and that you have to turn the big fat knobs named "Brightness" and "Contrast" on the from to change... well, brightness and contrast...

That being said, if the current kernel doesn't support your hardware, you would be better off looking at the exact hardware your ChromeBook contains and file a bug against the kernel...

It's a labour-intensive job as they first ask you to try with the latest kernel and then you'll have to run a bunch of experimental hardware-detection programs, file the reports, ... But then your name will show up in the Linux kernel as one of the contributors!!! ;-)

So you've got two choices:

  • wait...
  • work hard...
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  • As you're a reputation 6 user: If this all works, don't forget to click the grey check-mark under the "0" at the left of this text, which means "yes, this answer is valid"! ;-)
    – Fabby
    Jan 27, 2015 at 19:07
  • Finally found an answer why would that folder be empty. :-) Can you say what you base this on?
    – LAFK says Reinstate Monica
    Mar 10, 2015 at 15:57
  • @LIttleAncientForestKami: based on Kernel knowledge...
    – Fabby
    Mar 10, 2015 at 16:04
  • Do you mind taking a look at askubuntu.com/q/595098/72260 or askubuntu.com/q/497615/72260? I believe your answer there could help.
    – LAFK says Reinstate Monica
    Mar 10, 2015 at 16:05
  • Upvoted your answer... There is nothing we can do for #2 neither. You might as well tell him.
    – Fabby
    Mar 10, 2015 at 19:44

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