[Bug 97883] [i915] intel_backlight does not function - Lenovo X1 Yoga OLED

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=97883

--- Comment #19 from Niklas Kielblock <niklas.kielblock at googlemail.com> ---
(In reply to Jani Nikula from comment #18)
> Basically, we don't know how brightness is controlled on this laptop.

On Windows this is handled by a kernel module separate from the main Intel
graphics driver. The build for the model mentioned in this report is available
at https://support.lenovo.com/en/us/downloads/ds113141 though some other
laptops (X1 Yoga Generation 2, Alienware 13 R3) use slightly different versions
of what's clearly the same codebase.

The download above contains debug symbols, so I've done some cursory analysis.
It communicates with the panel via eDP AUX (couldn't say if it's using
I2C-over-AUX, though) through an interface exposed by the primary Intel
graphics driver. References to gamma and voltages (ELVSS) indicate it's
considerably more low-level.

It's developed by Intel, not a third-party manufacturer; I have no insight into
your organisation so forgive me if I'm wrong but I would imagine you can
inquire about this internally.

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