OLED panel brightness support

[Jani Nikula]

On Thu, 25 Jul 2019, Daniel Vetter <daniel at ffwll.ch> wrote:
> On Thu, Jul 25, 2019 at 03:35:40PM +0800, Kai-Heng Feng wrote:
>> The next question is, how do we change the brightness level for OLED
>> displays? Is changing gamma value a good way to do it?
>
> There's no overall amplifier knob to set general brightness on these?

Usually there would be. There's no backlight, it's just the OLED
brightness, so you'd need to talk to the panel itself. On eDP this would
be accomplished by using DPCD, on command mode DSI by using DCS
commands. VESA specifies the DPCD commands to use, and we have some
level of support for that in i915 (granted, should be one level higher
in drm core, but I digress).

It's just that at least in the case of the referenced bug, it doesn't
seem to use the standard DPCD commands. To support that, someone would
have to acquire the panel specs or reverse engineer the proprietary
stuff. And then you'd have to mess the driver to do things differently
to cater for individual proprietary panels.

BR,
Jani.


-- 
Jani Nikula, Intel Open Source Graphics Center