Public bug reported:
On Ubuntu 24.04.2 LTS running on a Lenovo Legion 5 Pro 16ACH6H (AMD +
NVIDIA RTX 3070 hybrid system), brightness control breaks starting from
kernel 6.17.0-23-generic and remains broken on all newer kernels up to
6.17.0-35.
The issue is fully reproducible.
WORKING KERNEL:
- 6.17.0-22-generic
- Display session: X11
- NVIDIA proprietary driver in use
- Backlight device present:
/sys/class/backlight/nvidia_0
- Brightness control works normally
BROKEN KERNELS:
- 6.17.0-23-generic and newer (tested up to 6.17.0-35)
- Wayland or X11 both affected
- Backlight directory is empty:
/sys/class/backlight/
SYMPTOMS:
- Brightness stuck at 100%
- No backlight device exposed in sysfs
- Mouse cursor shows trailing/ghosting artifacts on Wayland
- Display rendering instability
EXPECTED BEHAVIOR:
- /sys/class/backlight/nvidia_0 should be present
- Brightness control should function via NVIDIA DRM backlight interface
ACTUAL BEHAVIOR:
- No backlight device is registered at all in /sys/class/backlight/
- GNOME brightness controls have no effect
HARDWARE:
- Lenovo Legion 5 Pro 16ACH6H
- AMD Ryzen CPU (iGPU present but not used for display in working kernel)
- NVIDIA RTX 3070 Mobile (primary display output via nvidia-drm)
- NVIDIA proprietary driver active
REGRESSION:
- Kernel 6.17.0-22 works correctly
- 6.17.0-23 introduces regression and all newer kernels inherit it
This appears to be a regression in NVIDIA DRM backlight device
registration (fbdev / sysfs exposure).
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/2155617
Title:
Backlight device disappears and brightness breaks on kernel 6.17.0-23+
(Lenovo Legion 5 Pro, NVIDIA hybrid graphics)
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