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I've got a Lenovo Thinkpad P71 with the NVidia Quadro P3000, that has the "Discrete Graphics" setting on the BIOS, and I'm using the proprietary drivers on Debian 9.

For some reason, the brightness keys do not work (Fn+F5/Fn+F6)

I've tried adding Option "RegistryDwords" "EnableBrightnessControl=1" to my xorg.conf, adding pcie_aspm=force, acpi_osi=, acpi_osi=Linux, and acpi_backlight=vendor (individually) to my kernel parameters, doing update-grub, and rebooting, but nothing seems to work.

Currently, my kernel parameters are quiet splash acpi_osi= and I have EnableBrightnessControl=1 on my xorg.conf, and the brightness keys appear to work, but won't go past what appears to be 10% on the pop-up, and the actual brightness doesn't actually adjust.

In /sys/class/backlight/thinkpad_screen/ I have brightness, bl_power, max_brightness, and actual_brightness, but adjusting these does not work, and when I try using the Fn+F5/F6 keys, the values are reset to 0. (except for max_brightness, which stays at 15)

Additionally, xbacklight only works when I don't have acpi_osi= in my kernel parameters.

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There are quite a few questions about "brightness keys don't work", and the usual debugging method applies:

  1. Find out with evtest and xev if the brightness keys produce the correct keysyms

  2. Find out how to actually change the backlight intensity. If /sys/class/backlight/... doesn't work, but xbacklight (which uses xrandr) does, I'd stick with xbacklight. So configure boot to make it work.

  3. Configure whatever part of your distro is processing the brightness keys. This varies from desktop to desktop, and some people (like me) without a "proper" desktop also just use the window manager. So you need to either disable the current processing and add your own somewhere else, or change it to use xbacklight instead of adjusting /sys/class/backlight/..., which it probably does. Finding out how to do that needs information about your desktop setup.

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