This morning I found that I cannot change the brightness of my Dell XPs 13 laptop's display anymore. I tried the following to change the brightness
- Use keyboard brightness keys
- Run the commands shown below
- Boot with kernel option acpi_backlight=vendor. This resulted in a dell_something folder being present in the /sys/class/backlight folder. Changing the brightness file in that folder does not help.
- Add 'intel_backlight' to xorg.conf
- Set "load legacy option ROM" BIOS option to enabled and "secure boot" to disabled
- Boot with kernel option i915.disable-pch_pwm=0
- Boot from a fresh Ubuntu 12.04 USB stick installation. I can still not control the brightness. This is strange as the laptop came preinstalled with 12.04. Maybe this a hardware problem?
- Install latest intel video driver
Any ideas why this broke suddendly? I've upgraded from 12.04 to 14.04 in April and till yesterday the brightness keys were working fine.
echo 100 > /sys/class/backlight/intel_backlight/brightness echo 100 > /sys/class/backlight/acpi_video0/brightness