[Bug 2142989] [NEW] Screen brightness adjustment not working on Dell XPS 13 Snapdragon X-Elite

[carmela]

Public bug reported:

Dell XPS 13 Snapdragon (ARM)
Ubuntu 25.10 “Questing”
Kernel: 6.17.0-8-qcom-x1e
GNOME su Wayland

The file /sys/class/backlight/dp_aux_backlight/brightness changes its
value when modified via shell, but the physical screen brightness
remains unchanged.

Function keys (Fn) for increasing/decreasing brightness are not working.

The brightness slider in Settings → Displays doesn't work.

Software-based dimming tools, such as gammastep, fail on Wayland with the following errors:
Error: Could not control gamma, exiting.
Error: Failed to start adjustment method: wayland

** Affects: ubuntu-concept
     Importance: Undecided
         Status: New


** Tags: brightness

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https://bugs.launchpad.net/bugs/2142989

Title:
  Screen brightness adjustment not working on Dell XPS 13 Snapdragon
  X-Elite

Status in ubuntu-concept:
  New

Bug description:
  Dell XPS 13 Snapdragon (ARM)
  Ubuntu 25.10 “Questing”
  Kernel: 6.17.0-8-qcom-x1e
  GNOME su Wayland

  The file /sys/class/backlight/dp_aux_backlight/brightness changes its
  value when modified via shell, but the physical screen brightness
  remains unchanged.

  Function keys (Fn) for increasing/decreasing brightness are not
  working.

  The brightness slider in Settings → Displays doesn't work.

  Software-based dimming tools, such as gammastep, fail on Wayland with the following errors:
  Error: Could not control gamma, exiting.
  Error: Failed to start adjustment method: wayland

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