I have 15.10 default install, no any changes to /etc/default/grub. Now when I press Fn + arrowUp/Down I can see display brightness change notification. Moreover, /sys/class/backlight/acpi_video0/* seem to reflect my pressings and notifiaction's bar length. So, everything looks good, but display's brightness does not change at all.
When I try to put aspm_pcie=force, acpi_osi=linux, acpi_osi=vendor, acpi_brightness=vendor or some combination of theese --- nothing improves (however I can get things worse: values in /sys/class/backlight/acpi_video0/* stop to reflect my pressings).
There are other solution which says to put into xorg.conf (Device section) the line:
Option "RegistryDwords" "EnableBrightnessControl=1"But where should I try to put this line in 15.10?
Is there any other solution so far?
91 Answer
I had kind of bug that I figured out recently, I don't know if is the same problem.
The button of backlight change when pressed, but it didn't affect the backlight in fact. I tried installing xbacklight and using xrandr to set the backlight and nothing.
Finally, I tried go in BIOS and change with the same button of keyboard, and(I don't know why), it works!! When I came back to ubuntu, the problem was solved.
