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
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.
/sys/class/backlight/thinkpad_screen/ I have
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.