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My laptop is an i7 8750H with GTX 1060. Mobo is Clevo P950ER. There is an Intel graphics card also inside. I don't have bumblebee installed and I'm using Nvidia proprietary drivers. Using Xfce desktop env.
Screen backlight controls initially don't change screen brightness. It only blacks out when set to zero. In /sys/class/backlight/intel_backlight the values do change when using Fn-keys for keyboard brightness.
I have tried all the acpi_backlight options, none of which work.
One kernel line works, but not correctly:
Referring to post https://bbs.archlinux.org/viewtopic.php?id=236835
I put i915.conf in modprobe.d with 'options i915 enable_dpcd_backlight=1'
Now screen responds to the brightness buttons, but the actual brightness seems to turn up or down randomly. I tested this also with only Intel graphics card enabled, and the behaviour is the same.
After setting the kernel option, /sys/class/backlight/intel_backlight/max_brightness value changes from 60000 to 65536.
Looking closer, change of brightness is not actually random, as the real brightness up/down change is persistent in a kind of a loop. I'm suspecting max_brightness value is too high, and the brightness change I'm seeing is a remainder of a divisor of the correct max value. So far I didn't find a solution for this, help appreciated!
Last edited by Tuomola (2018-08-01 09:28:47)
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Found a solution, of course there was an issue already on these forums.
https://bbs.archlinux.org/viewtopic.php?id=237257
For my machine, i915.enable_dpcd_backlight=1 kernel param is needed.
What I missed on testing acpi_backlight options, was
acpi_osi="!Windows 2015" acpi_backlight=video
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