http://bugzilla.opensuse.org/show_bug.cgi?id=899879
http://bugzilla.opensuse.org/show_bug.cgi?id=899879#c70
--- Comment #70 from Egbert Eich
1. What you get when you do: systemctl list-units | grep backlight
# systemctl list-units | grep backlight
sys-devices-pci0000:00-0000:00:02.0-drm-card0-card0\x2deDP\x2d1- intel_backlight.device loaded active plugged /sys/devices/pci0000:00/0000:00:02.0/drm/card0/card0-eDP-1/intel_backlight systemd-backlight@backlight:intel_backlight.service loaded active exited Load/Save Screen Backlight Brightness of backlight:intel_backlight system-systemd\x2dbacklight.slice loaded active active system-systemd\x2dbacklight.slice
OK, so there is no ACPI backlight. That's what I was trying to find out.
2. What you get by doing: ls /var/lib/systemd/backlight/
# ls /var/lib/systemd/backlight/ pci-0000:00:02.0:backlight:intel_backlight
Ok. This is the file then where systemd stores the backlight value on shut down.
3. Determine if you get a somewhat linear behaviour between 0 and 4687.
No. 0 is black and even 1 is bright. It looks like values above 4687 make a difference in brightness.
This is something we need to report to Intel. The non-linear behavior is of course he root of all your problems. I need one more info, though: (In reply to Freek de Kruijf from comment #69)
# dmesg > dmesg.out Please get me the content of 'dmesg.out'.
See attached file dmesg.out.gz
Ok, this contains a lot of useful information already.
2. run as root: # intel_bios_dumper intel_bios.data get me the output file 'intel_bios.data'
# intel_bios_dumper intel_bios.data Couldn't read graphics card ROM: Input/output error
Ok, not sure why this happens. We should be able to get the information I'm missing from the kernel logs as well if you set drm.debug=0x6 (instead of 0x4) and get me a dmesg again. Do you have an account on bugs.freedesktop.org? I may open a ticket there for Intel to look into this. It would be good if I could add you to this in case Intel needs further information from you. -- You are receiving this mail because: You are on the CC list for the bug.