Lost screen backlight controls after upgrade to F37

I have a System76 Lemur Pro. Since upgrading to F37 I’ve lost the ability to control the screen brightness in Gnome and via the function keys. The folder /sys/class/backlight doesn’t exist and from what I’ve been reading it should be there.

CometLake graphics

$ lspci -k | grep -EA3 'VGA|3D|Display'
00:02.0 VGA compatible controller: Intel Corporation CometLake-U GT2 [UHD Graphics] (rev 02)
	DeviceName: VGA compatible controller
	Subsystem: CLEVO/KAPOK Computer Device 1401
	Kernel driver in use: i915
	Kernel modules: i915

Kernel includes "acpi_backlight=intel

$ cat /proc/cmdline 
BOOT_IMAGE=(hd0,gpt2)/vmlinuz-6.1.5-200.fc37.x86_64 root=UUID=28730e9c-57a9-4dd4-9aa7-f4eb451cae1f ro resume=/dev/mapper/fedora_localhost--live-swap rd.lvm.lv=fedora_localhost-live/root rd.luks.uuid=luks-7a875e5b-a21e-4e99-9cf6-399a7bd21e5a rd.lvm.lv=fedora_localhost-live/swap rhgb quiet splash acpi_backlight=intel

$ lsmod | grep i915
i915                 3436544  53
drm_buddy              20480  1 i915
drm_display_helper    208896  1 i915
cec                    81920  2 drm_display_helper,i915
video                  65536  1 i915
ttm                    94208  1 i915

Attempting to use the function keys to adjust the brightness yields the following in the syslog:

Failed to set new screen percentage: GDBus.Error:org.gtk.GDBus.UnmappedGError.Quark._gsd_5fpower_5fmanager_5ferror.Code1: No usable backlight could be found!

What other info can I provide to help fix this?

On the next boot try removing this splash acpi_backlight=intel from the kernel command line and see what the result is. I do not have and have never had that in my kernel command line and I see this on my laptop. My laptop has intel + nvidia GPUs.

$ ls /sys/class/backlight/intel_backlight/
actual_brightness  bl_power  brightness  device  max_brightness  power  scale  subsystem  type  uevent

Removing those entries didn’t work.

Aha! I set it to “acpi_backlight=native” and it worked! In case someone else finds this thread…

edit /etc/default/grub and include “acpi_backlight=native” at the end of your GRUB_CMDLINE_LINUX_DEFAULT stanza:


Save your config and run “sudo grub2-mkconfig”. Reboot.

ref: Backlight - ArchWiki

ironically, I often find the best documentation for Fedora in the Archlinux wiki.


Sorry to pile on what looks like the solution to this question, but one clarifying question that I was having trouble getting a clear answer on through Google - is sudo grub2-mkconfig the full command there, or is there a path that you had to type afterward, like sudo grub2-mkconfig --output=<filename here>?


I’m no grub expert, but all I typed was what is in the quotes.

The actual command must have an output file for it to write to a file. Without specifying an output file it writes the output to the screen.

The command is sudo grub2-mkconfig -o /boot/grub2/grub.cfg

To find out what a command does use the man page, as man grub2-mkconfig
You also can peruse the many threads that contain that command, or see the official documentation at

Thanks for the file location info!

FWIW, that page on the Fedora Docs site has a banner at the top that it is deprecated, and “large parts of it are no longer current”, so I was a bit hesitant to assume.

I appreciate the help!

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That doc page was updated fairly recently and I believe is current for all releases since fedora 34.