OLED panel brightness support

[Kai-Heng Feng]

at 16:26, Jani Nikula <jani.nikula at linux.intel.com> wrote:

> On Tue, 23 Jul 2019, Kai-Heng Feng <kai.heng.feng at canonical.com> wrote:
>> Hi,
>>
>> Currently, OLED panel brightness [1] is not supported.
>
> As a general statement this is not true, and not backed up by the
> referenced bug. We just don't know how brightness is controlled on that
> particular laptop, because it apparently uses a properietary mechanism.
>
> If it used the brightness control mechamism specified in the VESA eDP
> spec, it should work just fine with the i915 aux backlight support, and
> we should also export the regular backlight sysfs for this.

I am told that Windows introduced “NitsBrightness” [1] to support OLED panel.
I don’t know how it’s plumbed to the aux interface though.

Is it possible to ask Windows graphics team how Windows handle OLED panel?

[1]  
https://docs.microsoft.com/en-us/windows-hardware/drivers/ddi/content/d3dkmdt/ns-d3dkmdt-_dxgk_brightness_caps

Kai-Heng

>
> BR,
> Jani.
>
>
>> We have a similar Dell system that also affect by lack of OLED brightness
>> support.
>>
>> I’ve investigated both kernel and user space but I haven’t found a good
>> general solution yet.
>> Dell systems use EDID descriptor 4 as Dell specific descriptor, which
>> reports its panel type and we can know it’s an OLED panel or not.
>>
>> My initial thought is to add a new attribute “oled" in drm_sysfs.c [2] to
>> let userspace like clutter [3] to control the brightness.
>> However other DEs may need to implement their own OLED brightness support
>> which isn’t ideal.
>>
>> So I’d like to know if there’s any good way to support OLED brightness in
>> good old backlight sysfs, to let userspace keep to the current interface.
>>
>> [1] https://bugs.freedesktop.org/show_bug.cgi?id=97883
>> [2] https://pastebin.ubuntu.com/p/QYrRBppVT9/
>> [3]
>> https://gitlab.gnome.org/GNOME/clutter/blob/master/clutter/clutter-brightness-contrast-effect.c#L559
>>
>> Kai-Heng
>
> -- 
> Jani Nikula, Intel Open Source Graphics Center