upgrading 22.11 -> 23.05 removes everything from /sys/class/backlight

[MangoIV]

Describe the bug

I cannot change the brightness of my laptop screen (lenovo thinkpad p14s) after upgrading to 23.05

Steps To Reproduce

Steps to reproduce the behavior:

1. buy thinkpad p14s
2. install https://git.sr.ht/~mangoiv/dotfiles Rev bc5d66b2c6ee0a2d3d9bbc462ad791c70b8eba5b
3. try out brightnessctl or illum

Expected behavior

either of brightnessctl or illum or whatever allow to change brightness

Additional context

Brightnessctl only shows leds

I checked on gnome wayland as well, it's not the fault of the program, seems it really stopped working fundamentally.

Available devices:
Device 'platform::mute' of class 'leds':
	Current brightness: 0 (0%)
	Max brightness: 1

Device 'tpacpi::power' of class 'leds':
	Current brightness: 0 (0%)
	Max brightness: 255

Device 'input0::scrolllock' of class 'leds':
	Current brightness: 0 (0%)
	Max brightness: 1

Device 'input0::capslock' of class 'leds':
	Current brightness: 0 (0%)
	Max brightness: 1

Device 'tpacpi::lid_logo_dot' of class 'leds':
	Current brightness: 0 (0%)
	Max brightness: 255

Device 'tpacpi::standby' of class 'leds':
	Current brightness: 0 (0%)
	Max brightness: 255

Device 'input0::numlock' of class 'leds':
	Current brightness: 0 (0%)
	Max brightness: 1

Device 'tpacpi::thinkvantage' of class 'leds':
	Current brightness: 0 (0%)
	Max brightness: 255

Device 'tpacpi::kbd_backlight' of class 'leds':
	Current brightness: 0 (0%)
	Max brightness: 2

Device 'platform::micmute' of class 'leds':
	Current brightness: 0 (0%)
	Max brightness: 1

Notify maintainers

Metadata

Please run nix-shell -p nix-info --run "nix-info -m" and paste the result.

[user@system:~]$ nix-shell -p nix-info --run "nix-info -m"
 - system: `"x86_64-linux"`
 - host os: `Linux 6.2.9-zen1, NixOS, 23.05 (Stoat), 23.05.20230411.3fb8eed`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix Super) 2.14.0pre20230128_792d83f`
 - nixpkgs: `/nix/var/nix/profiles/per-user/root/channels/nixos`

[MangoIV]

looks like /sys/class/backlight/ is completely empty

[MangoIV]

downgraded to 22.11 and works perfectly fine again.

[megheaiulian]

This looks like something kernel related. Can you try 23.05 but with a bit older kernel? Maybe the one that you use in 22.11 if possible.

[MangoIV]

Thank you. This problem indeed disappears when downgrading to 6.0 which sadly has been removed from the unstable package set.

[MangoIV]

https://github.com/NixOS/nixos-hardware/blob/3006d2860a6ed5e01b0c3e7ffb730e9b293116e2/lenovo/thinkpad/p14s/amd/gen2/default.nix#L11

[Artturin]

Arch report https://bugs.archlinux.org/task/77056

[nixos-discourse]

This issue has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/cannot-control-display-brightness-in-nixos-23-05/29157/2

[orangci]

Hi, after upgrading from 23.05 to 23.11 unstable no sort of brightness control works (other than the physical buttons on my monitor) I tried using nixos-generate-config which is the answer provided in the discourse here. When I do light, I get this message: No backlight controller was found, so we could not decide an automatic target. The current command will have no effect. Please use -L to find a target and then specify it with -s. . There's also no /sys/class/backlight, either :(
\n edit: my computer is an hp elitedesk

[Artturin]

Hi, after upgrading from 23.05 to 23.11 unstable no sort of brightness control works (other than the physical buttons on my monitor) I tried using nixos-generate-config which is the answer provided in the discourse here. When I do light, I get this message: No backlight controller was found, so we could not decide an automatic target. The current command will have no effect. Please use -L to find a target and then specify it with -s. . There's also no /sys/class/backlight, either :( \n edit: my computer is an hp elitedesk

Did you make sure you are using the kernelParams either manually or from the generator.

[orangci]

Did you make sure you are using the kernelParams either manually or from the generator.

Uh, I have no idea what kernelParams is, I am a nix newbie. I just ran nixos-generate-config from my terminal.

[Tchekda]

I can confirm the faulty option was acpi_backlight=none. Either replace it with acpi_backlight=native or remove it from the boot.kernelParams list