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Micromot

Member

Registered: 2026-02-13

Posts: 1

No Backlight controller, /sys/class/backlight is empty

I have a similar issue to this person, but the issue still persists after trying everything described in the thread: https://bbs.archlinux.org/viewtopic.php?id=289989

when using ddcutil detect, my monitors show up

Display 1
   I2C bus:  /dev/i2c-4
   DRM_connector:           card1-HDMI-A-1
   EDID synopsis:
      Mfg id:               PHL - Philips Consumer Electronics Company
      Model:                PHL 243S7
      Product code:         2319  (0x090f)
      Serial number:        UHB2045010501
      Binary serial number: 10501 (0x00002905)
      Manufacture year:     2020,  Week: 45
   VCP version:         2.2

Display 2
   I2C bus:  /dev/i2c-7
   DRM_connector:           card1-DP-1
   EDID synopsis:
      Mfg id:               ACR - Acer Technologies
      Model:                Acer XF240H
      Product code:         1138  (0x0472)
      Serial number:        
      Binary serial number: 2223000273 (0x84804ad1)
      Manufacture year:     2018,  Week: 48
   VCP version:         2.1

Display 3
   I2C bus:  /dev/i2c-8
   DRM_connector:           card1-DP-2
   EDID synopsis:
      Mfg id:               MSI - Microstep
      Model:                MSI MAG241C
      Product code:         16034  (0x3ea2)
      Serial number:        
      Binary serial number: 808465241 (0x30303359)
      Manufacture year:     2019,  Week: 50
   VCP version:         2.1

ddcci_backlight and i2c-dev are both loaded

ddcci-driver-linux-dkms is also installed

I can interact with the brightness with ddcutil

With Brillo i get this response:

Error: could not find an accessible controller
Error: initialization failed

sys/class/backlight is empty

Last edited by Micromot (2026-02-13 22:33:06)