What were you trying to do that didn't work?

Auto brightness in GNOME does not work although the ambient light sensor (ALS) is present and reports changing values via sysfs. The ALS device does not emit any IIO/udev events, so gnome-settings-daemon (power plugin) never detects changes and therefore never updates backlight brightness.

What is the impact of this issue to you?

Please provide the package NVR for which the bug is seen:

kernel-6.12.0-191.el10
gnome-shell-49.1-8.el10
gnome-settings-daemon-47.2-7.el10

How reproducible is this bug?:

100%

Steps to reproduce

1. Ensure auto brightness is enabled in GNOME
2. Monitor ALS raw values

   watch -n 1 cat /sys/bus/iio/devices/iio:device2/in_illuminance_raw
   

3. Change ambient light (cover/uncover sensor, use flashlight)
4. Monitor IIO udev events:

   udevadm monitor --kernel --subsystem-match=iio
   

Expected results

• ALS changes should generate IIO/udev events
• GNOME Settings Daemon Power plugin should detect the change
• Screen brightness should adjust automatically

  Actual results

• in_illuminance_raw changes correctly in sysfs
• No events are emitted by the ALS device:

  udevadm monitor --kernel --subsystem-match=iio
  (no output at all when light changes)
  

gsettings get org.gnome.settings-daemon.plugins.power ambient-enabled
true

Detected IIO devices:

/sys/bus/iio/devices/iio:device0/name: gyro_3d
/sys/bus/iio/devices/iio:device1/name: accel_3d
/sys/bus/iio/devices/iio:device2/name: als

Backlight interface:

/sys/class/backlight/intel_backlight

UEVENT output for ALS:

DEVTYPE=iio_device
DEVNAME=iio:device2
NAME=als
MAJOR=235
MINOR=2