I'm unable to change the backlight brightness under 14.04.
habefaro@habefaro-Lenovo-U310:~$ uname -a
Linux habefaro-Lenovo-U310 3.16.0-34-generic #47~14.04.1-Ubuntu SMP Fri Apr 10 17:49:16 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
Using the keys or xbacklight results in changing the values reported by xbacklight or /sys/
habefaro@habefaro-Lenovo-U310:~$ xbacklight
19.991807
habefaro@habefaro-Lenovo-U310:~$ xbacklight -dec 40
habefaro@habefaro-Lenovo-U310:~$ xbacklight
0.000000
Before pressing brightness keys:
habefaro@habefaro-Lenovo-U310:~$ cat /sys/class/backlight/intel_backlight/brightness
0
After "increasing" the brightness:
habefaro@habefaro-Lenovo-U310:~$ cat /sys/class/backlight/intel_backlight/brightness
1464
The actual brightness of the screen however stays the same. It has been suggested to use
acpi_osi=Linux acpi_backlight=vendor
as boot options, but to no avail.