[Bug 2112165] Re: Brightness control not working on ASUS ROG Zephyrus G16 GU605MI (no usable backlight interface)

Hi, thank you very much for the shared workaround. I confirm that it
fixed the issue. Thank you once again

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https://bugs.launchpad.net/bugs/2112165

Title:
Brightness control not working on ASUS ROG Zephyrus G16 GU605MI (no
usable backlight interface)

Status in linux package in Ubuntu:
Incomplete

Bug description:
I'm running Ubuntu 24.04 with kernel 6.11 on an ASUS ROG Zephyrus G16
GU605MI laptop.

Screen brightness control does not work. Neither /sys/class/backlight
interfaces nor software tools like xrandr have any effect. The device
uses hybrid graphics (Intel + NVIDIA), and all common kernel boot
parameters have been tested without success.


Model: ASUS ROG Zephyrus G16 GU605MI
Kernel: 6.11.0-26-generic
Display: Internal eDP panel (detected as eDP-1)
GPU: Intel iGPU + NVIDIA RTX 4060 Laptop GPU
/sys/class/backlight: Empty or only intel_backlight, which does nothing
Tried kernel parameters:

acpi_backlight=video

acpi_backlight=native

acpi_backlight=vendor

acpi_backlight=none

acpi_osi=Linux

Expected behavior:
Brightness should be adjustable using brightnessctl, /sys/class/backlight, or xrandr.

Actual behavior:

/sys/class/backlight is missing or ineffective

xrandr --brightness has no effect

brightnessctl runs but does not change brightness

No visible EC or alternative brightness path is exposed
---
ProblemType: Bug
ApportVersion: 2.28.1-0ubuntu3.6
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC1: usuario 2669 F.... wireplumber
/dev/snd/controlC0: usuario 2669 F.... wireplumber
/dev/snd/seq: usuario 2665 F.... pipewire
CRDA: N/A
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
DistroRelease: Ubuntu 24.04
InstallationDate: Installed on 2025-05-06 (27 days ago)
InstallationMedia: Ubuntu 24.04.2 LTS "Noble Numbat" - Release amd64 (20250215)
MachineType: ASUSTeK COMPUTER INC. ROG Zephyrus G16 GU605MI_GU605MI
Package: linux (not installed)
ProcFB: 0 i915drmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-6.11.0-26-generic root=UUID=10b31c36-2ee7-41c7-ba5f-4ce90690c4ab ro quiet splash vt.handoff=7
ProcVersionSignature: Ubuntu 6.11.0-26.26~24.04.1-generic 6.11.11
RebootRequiredPkgs: Error: path contained symlinks.
RelatedPackageVersions:
linux-restricted-modules-6.11.0-26-generic N/A
linux-backports-modules-6.11.0-26-generic N/A
linux-firmware 20240318.git3b128b60-0ubuntu2.12
Tags: noble
Uname: Linux 6.11.0-26-generic x86_64
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: N/A
_MarkForUpload: True
dmi.bios.date: 08/14/2024
dmi.bios.release: 5.32
dmi.bios.vendor: American Megatrends International, LLC.
dmi.bios.version: GU605MI.323
dmi.board.asset.tag: ATN12345678901234567
dmi.board.name: GU605MI
dmi.board.vendor: ASUSTeK COMPUTER INC.
dmi.board.version: 1.0
dmi.chassis.type: 10
dmi.chassis.vendor: ASUSTeK COMPUTER INC.
dmi.chassis.version: 1.0
dmi.ec.firmware.release: 3.22
dmi.modalias: dmi:bvnAmericanMegatrendsInternational,LLC.:bvrGU605MI.323:bd08/14/2024:br5.32:efr3.22:svnASUSTeKCOMPUTERINC.:pnROGZephyrusG16GU605MI_GU605MI:pvr1.0:rvnASUSTeKCOMPUTERINC.:rnGU605MI:rvr1.0:cvnASUSTeKCOMPUTERINC.:ct10:cvr1.0:sku:
dmi.product.family: ROG Zephyrus G16
dmi.product.name: ROG Zephyrus G16 GU605MI_GU605MI
dmi.product.version: 1.0
dmi.sys.vendor: ASUSTeK COMPUTER INC.

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