FS#77056 - [linux-zen] Lost backlight property with 6.1.4.zen2-1

Attached to Project: Arch Linux
Opened by Eivind (mokkurkalve) - Sunday, 08 January 2023, 23:18 GMT
Last edited by Toolybird (Toolybird) - Tuesday, 10 January 2023, 00:20 GMT
Task Type Bug Report
Category Packages: Extra
Status Closed
Assigned To No-one
Architecture x86_64
Severity Medium
Priority Normal
Reported Version
Due in Version Undecided
Due Date Undecided
Percent Complete 100%
Votes 4
Private No

Details

Description:

Upgraded linux-zen from 6.1.3.zen1-1 to 6.1.4.zen2-1.
After upgrade xbacklight return "No outputs have backlight property" and /sys/class/backlight/ are empty.
Downgrade to 6.1.3.zen1-1 and i have backlight property again.
Graphics are Intel CometLake-U GT2 [UHD Graphics] and I'm using xf86-video-intel


Additional info:
* package version(s)
6.1.4.zen2-1
* config and/or log files etc.
* link to upstream bug report, if any

Steps to reproduce:
This task depends upon

Closed by  Toolybird (Toolybird)
Tuesday, 10 January 2023, 00:20 GMT
Reason for closing:  Not a bug
Additional comments about closing:  See comments
Comment by loqs (loqs) - Sunday, 08 January 2023, 23:37 GMT
Have you tried changing the backlight control [1][2] via a kernel parameter[3]?

[1] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit?id=8af3d02aae3ecc23ee84d7078d1ebb3df7557dda
[2] https://wiki.archlinux.org/title/backlight
[3] https://wiki.archlinux.org/title/Kernel_parameters
Comment by fzap (fzap) - Monday, 09 January 2023, 05:56 GMT
I can confirm this issue using a Lenovo Thinkpad E15 Gen 2 with xf86-video-amdgpu and 'light' (instead of xbacklight). I also put the kernel parameter 'acpi_backlight=vendor' on my systemd-boot configuration. Since 6.1.4 it doesn't work anymore, but I am using the default kernel.
Comment by Eivind (mokkurkalve) - Monday, 09 January 2023, 09:52 GMT
Yes. I forgot that I've added the following to the kernel commandline a long time ago in order to be able to control the keyboard backlight with the Fn-key:
acpi_os_name=Linux acpi_osi=! acpi_osi=Linux acpi_backlight=vendor
Testing it out here I find that using the same with kernel 6.1.4, only replacing acpi_backlight=vendor with acpi_backlight=native, I get what I want; the ability to control both the screen backlight and the keyboard backlight.
So AFAIK the problem are solved for me.
Comment by fzap (fzap) - Monday, 09 January 2023, 16:08 GMT
I've changed 'acpi_backlight=vendor' to 'acpi_backlight=native', that fixed the problem, thanks Eivind

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