[Intel-gfx] eDP display control registers in Linux kernel

[Jani Nikula]

Hi Michael -

Please always cc: the relevant mailing lists; done now.

On Sun, 22 Feb 2015, Michael Leuchtenburg <michael at slashhome.org> wrote:
> Hi Jani,
>
> I've been trying to figure out how to control the dynamic backlight control
> on my new Dell XPS 13 since the defaults are atrocious - huge swings in
> brightness from a black background to a white one, over a few seconds
> period so it's very obvious. I eventually tracked down a patch from the
> Chromium folks that adds a sysfs interface (
> https://chromium.googlesource.com/chromiumos/third_party/kernel/+/db5eacd6ac7a0cbda4ea1010fabbd3ff6b30e0bc%5E%21/),
> but it seems to depend on your patch that adds eDP display control
> registers (
> http://lists.freedesktop.org/archives/dri-devel/2013-November/049098.html),
> which was never merged into mainline as far as I can tell.
>
> Do you know what the status of that is? Is it still wending its way through
> the process (now, over a year later) or did it die somewhere along the way?
> The patch doesn't apply to mainline today, though it's simple enough that I
> suspect it'd be easy to adapt. I'd rather see where it went, though.
>
> I'd appreciate any help you can offer.

The Chrome OS patches wouldn't be acceptable upstream, and indeed
they've never been posted upstream. A more driver agnostic approach
would be required.

My patches were simple, adding some macros etc. They were reviewed but
apparently forgotten, also by me. I'll repost them, but they won't do
you much good in this case.

I'm also not convinced yet that your problem would be solved by the
patches; are you sure Dell XPS 13 does have dynamic backlight control in
the panel, adjustable via DPCD?

BR,
Jani.


-- 
Jani Nikula, Intel Open Source Technology Center