[Intel-gfx] [PATCH] drm/i915/dp: Stop enabling limited color ranges for everything

Peter Fr├╝hberger fritsch at kodi.tv
Thu Jan 5 09:41:59 UTC 2017


On Thu, Jan 5, 2017 at 9:52 AM, Daniel Vetter <daniel at ffwll.ch> wrote:

> On Thu, Jan 05, 2017 at 10:41:07AM +0200, Jani Nikula wrote:
> > No matter what we do here, the question remains what to do with
> > Chamelium. Changing the color range is really a workaround for
> > Chamelium, not a fix. Using CEA range is perfectly fine per DP spec.
> Can we just set a non-CEA mode/edid for chamelium, problem solved? We want
> to do that anyway for HDMI, where you really have to do the limited range
> dance to make stuff display correctly.
> -Daniel
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch
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> Intel-gfx at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx

I shortly want to emphasize on this:

No matter what you sync with the Port - userspace must have a chance to
know what happens with its DATA. It is a huge problem when the driver
clamps by itself assuming everything it gets would be full range. Or when
the Output device clamps and does not scale, then you loose, e.g. 0 ..16
and 235.. 255. On the other hand such scenarios make userspace scale data -
especially video data - twice. One time to full range and later down in the
driver when using CEA mode, e.g. Limited 16:235.

Please keep that in mind. It's problematic already nowadays when a 1:1
output without color altering is high importance.

Thanks very much
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