Dell Chromebook 11 - unable to set backlight and /sys/class/backlight/ folder is empty

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?

Solution 1:

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...