Quote Originally Posted by cyrus_the_virus View Post
I used this/ article that suggests making a change in xorg.conf. I removed this later because it does solve my problem. I think it just tells to which file the brightness value should be echoed, but since echoing a value manually does not work this solution does not work either.

Here is the output of the commands that you gave me:

Code:
$ cat /proc/cmdline
BOOT_IMAGE=/boot/vmlinuz-3.13.0-29-generic root=UUID=4e04ddb0-3020-4b02-827f-635306f670db ro quiet splash video.use_native_backlight=1 vt.handoff=7
Code:
$ ls /sys/class/backlight
intel_backlight
Code:
$ cat /var/log/Xorg.0.log | grep backlight
[    11.054] Kernel command line: BOOT_IMAGE=/boot/vmlinuz-3.13.0-29-generic root=UUID=4e04ddb0-3020-4b02-827f-635306f670db ro quiet splash video.use_native_backlight=1 vt.handoff=7
[    11.101] (--) intel(0): found backlight control interface intel_backlight (type 'raw')
Code:
$ for interface in /sys/class/backlight/*; do echo $interface; cat $interface/actual_brightness; cat $interface/max_brightness; done
/sys/class/backlight/intel_backlight
4882
4882
Note that this was done with video.use_native_backlight=1

Have you tried to set the brightness using
Code:
echo 3500 | sudo tee /sys/class/backlight/intel_backlight/brightness
with and without video.use_native_backlight?

It sounds like using the 3.14.5 kernel fixes a backlight bug on the XPS13 per a bug report https://bugs.freedesktop.org/show_bug.cgi?id=76276