Unable to adjust backlight in Fedora 23 on HP ZBook 15 laptop

Operating Systems & Open Source Linux
,
1

I am completely unable to adjust my backlight brighness in Fedora 23 with ZBook 15 (which is an nvidia optimus laptop).

The install is completely fresh, I have not changed any drivers. /sys/class/backlight/ only contains acpi_video0 and if I try to change the brightness by writing a value to /sys/class/backlight/acpi_video0/brightness nothing happens.

acpi_backlight=video and acpi_osi=Linux is currently set in my GRUB_CMDLINE_LINUX. I have tried all possible values for acpi_backlight.

I have never had this issue before on this laptop, it worked in booth Fedora 22 and openSUSE Leap.

Would really appreciate any help since the brightness is currently stuck at maximum.

2

You probably want to make sure you have the nvidia-drivers installed. I use the ones from here http://negativo17.org/nvidia-driver/

This seems to be the suggested fix

https://jamielinux.com/blog/cannot-adjust-screen-brightness-on-fedora/

You may also want to try this option instead of the two suggested

pcie_aspm=force acpi_osi=Linux acpi_backlight=vendor
3

Thank's a lot for the reply! I could not continue yesterday because I got a headache out of what felt like staring into a flashlight.

I wasn't able to get the drivers working first because I didn't realize that the akmod kernel modules was just source packages that I had to build myself manually, then I realized that I would get the binary modules if I just disabled the RPMFusion repos.

Anyways, I am now able to adjust the backlight using the xbacklight command which didn't work previously which is a big step forward. However, the /sys/... /acpi_video0/brightness still doesn't change anything and there are no other folders in /sys/class/backlight. The file changes it's value when I drag the brightness slider in Gnome but it doesn't change the backlight.

When I set acpi_backlight=vendor the slider disappears entirely.

4

They will build themselves, you just need to make sure you have kernel-devel installed.

Where are you getting the binary modules from?

5

Ah, there was never any binaries, I had istalled kernel-devel before I installed with RMPFusion disabled so the packages actually built that time. So now I have the dkms modules from negativo17 instead of the akmod modules from RPMFusion. dkms and akmod was completely new to me.

6

Ah ok, all good.

Did you try this one? 

GRUB_CMDLINE_LINUX="... rhgb quiet video.use_native_backlight=1"
7

Same result as when I leave out the acpi_backlight=vendor option, /sys/.../acpi_video0/brightness does not change anything.

8

For some reason it works after I suspend the system and then resume again. When I resume, nothing interesting shows up in dmesg other than this message:
video LNXVIDEO:00: Restoring backlight state

I also get this message in dmesg whenever I change the backlight with xbacklight:
ACPI Warning: \_SB_.PCI0.PEGP.DGFX._DSM: Argument #4 type mismatch - Found [Buffer], ACPI requires [Package] (20150930/nsarguments-95)