Regression: Backlight control broken on HP Omen 15‑ax246nf with kernel 7.0.0‑28‑generic

Regression: Backlight control broken on HP Omen 15‑ax246nf with kernel 7.0.0‑28‑generic

[harryblanc]

Hello,

I would like to report a regression affecting backlight control on my HP 
Omen laptop when using kernel 7.0.0‑28‑generic (Ubuntu 24.04 base, Linux 
Mint 22.3 XFCE).

Summary of the issue:
With kernel 7.0, the screen backlight is stuck at maximum brightness.
Brightness keys show the OSD and the slider moves, but the actual 
backlight does not change.
With kernel 6.17, brightness works normally.

Hardware:
- HP Omen 15‑ax246nf
- Intel i5‑7300HQ
- Intel HD Graphics 630 (i915)
- Nvidia GTX 1050 Mobile (disabled via Optimus)
- Linux Mint 22.3 XFCE (Ubuntu 24.04 base)

Backlight controller:
/sys/class/backlight/ → intel_backlight
acpi_video0 is no longer present under kernel 7.0.

ACPI errors visible only with kernel 7.0:
ACPI BIOS Error (bug): Attempt to CreateField of length zero
ACPI Error: Aborting method \_SB.WMID.WQBK
ACPI BIOS Error (bug): AE_AML_BUFFER_LIMIT
ACPI Error: Aborting method \_SB.WMID.HWMC
ACPI: video: [Firmware Bug]: ACPI(PEGP) defines _DOD but not _DOS

Kernel version:
Linux 7.0.0-28-generic #28~24.04.1-Ubuntu SMP PREEMPT_DYNAMIC Wed Jul 1 
15:50:57 UTC 2024 x86_64 GNU/Linux

GPU information (inxi -Gxxx):
Device-1: Intel HD Graphics 630 driver: i915
Device-2: NVIDIA GTX 1050 Mobile driver: N/A (Optimus disabled)
Display: X11 driver: modesetting, iris
Monitor: eDP-1 1920x1080 LG Display

Hardware summary (lshw -short):
Intel(R) Core(TM) i5-7300HQ
HD Graphics 630
GeForce GTX 1050 Mobile (disabled)
16 GiB DDR4
Samsung NVMe SSD + 1TB HDD

Expected behavior:
Backlight should be adjustable via intel_backlight or acpi_video0, as in 
kernel 6.17.

Observed behavior:
Backlight remains at maximum brightness regardless of ACPI events or 
brightness keys.

Steps to reproduce:
1. Boot kernel 7.0.0‑28‑generic
2. Attempt to change brightness
3. Backlight does not change

This appears to be an ACPI/i915 regression introduced in kernel 7.0.

Thank you for your work.