[Bug 221430] nvidia_wmi_ec_backlight: brightness writes silently dropped on HP OMEN 16 (2025)

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=221430

--- Comment #12 from floquimaurice@gmail.com ---
Hi,

I opened a ticket with the Intel DRM team, and they analyzed the drm.debug=0xe
logs.

https://gitlab.freedesktop.org/drm/i915/kernel/-/work_items/16065

They confirmed that the VBT correctly points to PCH PWM, and the i915 driver is
doing its job perfectly. The logs show the driver successfully calculating and
sending the PWM updates to the registers (set backlight level = 98259).

However, the physical panel ignores it. The Intel developers concluded this is
not an i915 issue. The hardware is deliberately ignoring the PCH PWM registers,
which perfectly confirms your initial theory: the HP Embedded Controller is
waiting for the \_SB.PC00.GFX0.CBL1 ACPI trigger to release the backlight
control.

Now that Intel has officially bounced the ball back to the ACPI/firmware side,
how can we proceed?

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