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

[Stéphane Marchesin]

On Sun, Feb 22, 2015 at 11:59 PM, Jani Nikula <jani.nikula at intel.com> wrote:
>
> 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.

I actually asked Eric to make a property version of this:
https://chromium-review.googlesource.com/#/c/244165/

Once this lands in Chrome OS, we should upstream it.

Stéphane

>
> 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
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