[bug] Screen brightness control unresponsive on ASUS Expertbook Ultra (Panther Lake / Intel Arc B390, Arch Linux)

[levihackerman-102]

Summary

Screen brightness cannot be changed visually. brightnessctl successfully writes values to /sys/class/backlight/intel_backlight/brightness (0–40000), but the physical display brightness does not change at all.

Steps to reproduce

1. Install Arch Linux on ASUS Expertbook Ultra
2. Install asusctl from AUR, start asusd
3. Run brightnessctl set 20% — value updates in sysfs but screen stays at full brightness
4. Fn brightness keys have no effect either

Expected behaviour

Screen brightness changes in response to brightnessctl / Fn keys.

Actual behaviour

Sysfs values update correctly but physical display brightness is always at maximum. No errors in dmesg when brightness is changed.

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System information

Device	ASUS Expertbook Ultra
GPU	Intel Arc B390 (Panther Lake) — driver: xe
OS	Arch Linux
Kernel version	7.0.11-arch1-1
Kernel cmdline	xe.enable_psr=0 xe.enable_psr2_sel_fetch=0 xe.enable_panel_replay=0
Backlight device	/sys/class/backlight/intel_backlight (max: 40000)
asusctl version	v6.3.7

---

Additional context

• Intel Panther Lake is a very new platform (late 2025); the xe DRM driver is in active development
• asusd starts successfully with no errors
• No relevant errors in dmesg during brightness changes
• Tried acpi_backlight=native/vendor/video kernel params — no effect

[levihackerman-102]

I raised this bug for discussion, did you manage to get brightness control working on Linux?

[hoachin]

I had a similar issue, but I found someone suggesting the following on the bug tracker for the xe driver (albeit for a different laptop).

Ultimately adding the following to my kernel boot parameters resolved the issue for me:

xe.enable_dpcd_backlight=2

After that, the brightness controls on the keyboard work (as does using brightnessctl directly)

[levihackerman-102]

I forgot to add my system info:

Operating System: Arch Linux
KDE Plasma Version: 6.6.5
KDE Frameworks Version: 6.26.0
Qt Version: 6.11.1
Kernel Version: 7.0.11-arch1-1 (64-bit)
Graphics Platform: Wayland
Processors: 16 × Intel® Core™ Ultra X7 358H
Memory: 32 GiB of RAM (30.6 GiB usable)
Graphics Processor: Intel® Graphics
Manufacturer: ASUS
Product Name: ASUS EXPERTBOOK B9406CAA
System Version: 1.0

[levihackerman-102]

I had a similar issue, but I found someone suggesting the following on the bug tracker for the xe driver (albeit for a different laptop).

Ultimately adding the following to my kernel boot parameters resolved the issue for me:

xe.enable_dpcd_backlight=2

After that, the brightness controls on the keyboard work (as does using brightnessctl directly)

Hmm this didn't work for me, can you link me to the bug tracker you mentioned? @hoachin

Edit: It worked now! Thanks a lot @hoachin

[levihackerman-102]

I had a similar issue, but I found someone suggesting the following on the bug tracker for the xe driver (albeit for a different laptop).

Ultimately adding the following to my kernel boot parameters resolved the issue for me:

xe.enable_dpcd_backlight=2

After that, the brightness controls on the keyboard work (as does using brightnessctl directly)

I also wanted to ask if you got the fingerprint sensor working? @hoachin

[hoachin]

I also wanted to ask if you got the fingerprint sensor working? @hoachin

I haven't tried yet, as to be honest it's not something I ever use

[burakgon]

I got fingerprint sensor working but you need a few extra modules: I will update the patches for this.

[levihackerman-102]

I got fingerprint sensor working but you need a few extra modules: I will update the patches for this.

I managed to fix it by recompiling fprint after adding my touchpad model to the supported versions since a similar model was already supported.

[levihackerman-102]

I got fingerprint sensor working but you need a few extra modules: I will update the patches for this.

I also wanted to ask if palm rejection is working for you? I'm trying to get it working currently

[adonespitogo]

@levihackerman-102 have you fixed the palm rejection issue?

[levihackerman-102]

@levihackerman-102 have you fixed the palm rejection issue?

Yeah it seems to work fine for me now. There's an option in KDE settings to disable touchpad while typing which did the trick for me.

[robintheilade]

I had a similar issue, but I found someone suggesting the following on the bug tracker for the xe driver (albeit for a different laptop).

Ultimately adding the following to my kernel boot parameters resolved the issue for me:

xe.enable_dpcd_backlight=2

After that, the brightness controls on the keyboard work (as does using brightnessctl directly)

This worked for me as well. Thanks @hoachin !

Laptop: Asus ExpertBook B9406CAA v1.0
OS: CachyOS
Kernel: 7.1.3-2-cachyos
Bootloader: limine