[Bug 2164918] Re: Linux 7.0.0-30 i915 Backlight Regression on MSI GF63 8RD

*** This bug is a duplicate of bug 2161309 *** https://bugs.launchpad.net/bugs/2161309 ** This bug has been marked a duplicate of bug 2161309 Backlight regression -- You received this bug notification because you are subscribed to linux in Ubuntu. Matching subscriptions: Bgg, Bmail, Nb https://bugs.launchpad.net/bugs/2164918 Title: Linux 7.0.0-30 i915 Backlight Regression on MSI GF63 8RD Status in linux package in Ubuntu: New Bug description: ## Summary Display brightness control is nonfunctional on Linux Mint when running kernel `7.0.0-30-generic` on an MSI GF63 8RD with Intel UHD Graphics 630. The kernel exposes the `intel_backlight` interface normally, and writes to the interface successfully update both `brightness` and `actual_brightness`. However, these changes are not applied to the physical display backlight, which remains at maximum brightness. Booting the same installation with kernel `6.14.0-37-generic` immediately restores normal brightness control. ## Hardware - **Laptop:** MSI GF63 8RD - **Integrated GPU:** Intel CoffeeLake-H GT2 [UHD Graphics 630] - **iGPU driver:** `i915` - **Discrete GPU:** NVIDIA GeForce GTX 1050 Ti Max-Q - **NVIDIA driver:** `580.178.04` - **Internal display:** eDP - **Session:** X11 ## Software - **Distribution:** Linux Mint 22.3 Cinnamon - **Affected kernel:** `7.0.0-30-generic` - **Known-good kernel:** `6.14.0-37-generic` ## Steps to Reproduce 1. Boot Linux Mint using kernel `7.0.0-30-generic`. 2. Attempt to change display brightness using Cinnamon's brightness controls. 3. Observe that the displayed brightness setting changes, but physical screen brightness does not. 4. Alternatively, bypass userspace and directly change the backlight through sysfs: ```bash echo 500 | sudo tee /sys/class/backlight/intel_backlight/brightness ``` 5. Read the resulting values: ```bash cat /sys/class/backlight/intel_backlight/{brightness,actual_brightness,max_brightness} ``` The kernel reports: ```text brightness:500 actual_brightness:500 max_brightness:1023 ``` Despite this, the physical panel remains at maximum brightness. 6. Reboot and select: ```text Advanced options for Linux Mint → Linux Mint, with Linux 6.14.0-37-generic ``` 7. Brightness control now works normally on the same hardware and Linux Mint installation. ## Backlight Interface on Affected Kernel ```text /sys/class/backlight/intel_backlight ``` The device resolves to: ```text ../../devices/pci0000:00/0000:00:02.0/drm/card1/card1-eDP-1/intel_backlight ``` Properties before testing: ```text brightness:1023 actual_brightness:1023 max_brightness:1023 type:raw ``` After writing `500`: ```text brightness:500 actual_brightness:500 max_brightness:1023 type:raw ``` Again, the physical backlight does not change. ## Relevant ACPI Output ```text ACPI: video: Video Device [GFX0] (multi-head: yes rom: no post: no) input: Video Bus as /devices/pci0000:00/acpi.video_bus.0/input/input9 ACPI: video: Video Device [PEGP] (multi-head: no rom: yes post: no) input: Video Bus as /devices/pci0000:00/0000:00:01.0/acpi.video_bus.1/input/input10 ``` The `video` and `msi_wmi` modules are loaded. Loading `video` explicitly does not expose an additional ACPI backlight device; `/sys/class/backlight/` continues to contain only `intel_backlight`. ## Expected Behavior Changing the brightness setting should alter the physical backlight intensity, as it does under kernel `6.14.0-37-generic`. ## Actual Behavior Under `7.0.0-30-generic`, the kernel accepts brightness changes and reports the requested value through both `brightness` and `actual_brightness`, but the physical display remains at maximum brightness. ## Regression This appears to be a kernel regression. The exact same Linux Mint installation and hardware behave as follows: ```text 6.14.0-37-generic → brightness works 7.0.0-30-generic → brightness values change, physical backlight does not ``` No userspace or hardware changes are required to reproduce or resolve the issue; selecting the older kernel at boot is sufficient. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2164918/+subscriptions