BIOS bug: brightness control broken on Linux - OMEN 16-am0015ns (SKU BP4Q7EA#ABE)

[ludwig475]

Bug Report for HP Support: Brightness Control Non-Functional on Linux — HP OMEN Gaming Laptop 16-am0015ns

Product Information

Field Value

Model	HP OMEN Gaming Laptop 16-am0015ns
SKU	BP4Q7EA#ABE
Serial Number
BIOS Version	F.14 (AMI, released 04/14/2026) — latest available, already updated
Board	HP 8D2F, version 75.54
Family	103C_5335M7 HP OMEN

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Operating System

Fedora 44 KDE Plasma, kernel 7.0.12-201.fc44.x86_64, Wayland session.

(Note: This is a Linux-specific bug. Windows is not affected as HP's proprietary drivers handle brightness differently.)

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Problem Description

Brightness control is completely non-functional. The brightness slider in the desktop environment moves normally, keyboard brightness hotkeys respond, but the display brightness never changes.

This affects:

• KDE Plasma brightness slider
• Keyboard Fn brightness keys
• Direct writes to /sys/class/backlight/intel_backlight/brightness
• Any software brightness control tool

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Root Cause (Technical)

After detailed analysis of the ACPI DSDT table extracted from the system firmware, the cause has been identified:

The ACPI methods responsible for brightness control (_BCM, _BCL, _BQC) are defined in the DSDT under the NVIDIA PCIe device subtree (PEGB/PEGE/DEDP), but the active display panel is driven by the Intel Arc integrated GPU (GFX0).

The Linux i915 driver looks for brightness control methods under the Intel GPU's own ACPI device node (GFX0). Since those methods are placed under the NVIDIA subtree instead, the driver never finds them and brightness control silently fails.

ACPI Device Hierarchy (from DSDT, HPQOEM 8D2F rev 01072009)

\_SB.PCI0
  ├── GFX0  (Intel Arc iGPU, 0000:00:02.0)
  │     └── [NO brightness methods here]
  │
  └── PEGB  (PCIe slot → NVIDIA GPU, 0000:01:00.0)
        └── PEGE
              └── DEDP
                    ├── _BCL  ← Brightness levels (0–100)
                    ├── _BCM  ← Brightness set method
                    └── _BQC  ← Brightness query

The _BCM method correctly writes to the Intel IGD OpRegion (BCLP, ASLC fields), so the logic itself is sound — it is only misplaced in the ACPI table hierarchy.

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Additional ACPI Error at Boot

The following ACPI error also appears at every boot, suggesting additional BIOS/WMI issues:

ACPI BIOS Error: AE_AML_BUFFER_LIMIT, Index (0x000000032) is beyond end of object (length 0x32)
ACPI Error: Aborting method \_SB.WMID.WQBZ
hp_bioscfg: Returned error 0x3, "Invalid command value/Feature not supported"

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Requested Fix

A BIOS update that moves the _BCM, _BCL, and _BQC methods from \_SB.PCI0.PEGB.PEGE.DEDP to \_SB.PCI0.GFX0 (or adds equivalent methods there), so that the Linux i915 driver can correctly discover and invoke them for brightness control.

This is a straightforward DSDT correction that would restore full brightness control functionality on Linux without requiring any kernel-side workarounds.