Re: [PATCH 5/7] drm/uAPI: Add "preferred color format" drm property as setting for userspace

[Werner Sembach <wse@xxxxxxxxxxxxxxxxxxx>]

Hi,

Am 10.01.24 um 14:42 schrieb Andri Yngvason:

> mið., 10. jan. 2024 kl. 13:09 skrifaði Werner Sembach <wse@xxxxxxxxxxxxxxxxxxx>:
> > Hi,
> >
> > Am 10.01.24 um 11:11 schrieb Andri Yngvason:
> > > Hi,
> > >
> > > mið., 10. jan. 2024 kl. 09:27 skrifaði Maxime Ripard <mripard@xxxxxxxxxx>:
> > > > On Tue, Jan 09, 2024 at 06:11:02PM +0000, Andri Yngvason wrote:
> > > > > From: Werner Sembach <wse@xxxxxxxxxxxxxxxxxxx>
> > > > >
> > > > > Add a new general drm property "preferred color format" which can be used
> > > > > by userspace to tell the graphic drivers to which color format to use.
> > > > >
> > > > > Possible options are:
> > > > >      - auto (default/current behaviour)
> > > > >      - rgb
> > > > >      - ycbcr444
> > > > >      - ycbcr422 (not supported by both amdgpu and i915)
> > > > >      - ycbcr420
> > > > >
> > > > > In theory the auto option should choose the best available option for the
> > > > > current setup, but because of bad internal conversion some monitors look
> > > > > better with rgb and some with ycbcr444.
> > > > >             
> > > > I looked at the patch and I couldn't find what is supposed to happen if
> > > > you set it to something else than auto, and the driver can't match that.
> > > > Are we supposed to fallback to the "auto" behaviour, or are we suppose
> > > > to reject the mode entirely?
> > > >
> > > > The combination with the active output format property suggests the
> > > > former, but we should document it explicitly.
> > > >           
> > > It is also my understanding that it should fall back to the "auto"
> > > behaviour. I will add this to the documentation.
> > >         
> > Yes, that was the intention, and then userspace can check, but it wasn't well
> > received: https://gitlab.freedesktop.org/drm/amd/-/issues/476#note_964530
> >
> > Actually a lot of the thoughts that went into the original patch set can be
> > found in that topic.
> >
> > There was another iteration of the patch set that I never finished and sent to
> > the LKML because I got discouraged by this:
> > https://lore.kernel.org/dri-devel/20210623102923.70877c1a@eldfell/
> >       
> Well, I've implemented this for sway and wlroots now and Simon has
> reacted positively, so this does appear likely to end up as a feature
> in wlroots based compositors.
>
> > I can try to dig it up, but it is completely untested and I don't think I still
> > have the respective TODO list anymore, so I don't know if it is a better or
> > worst starting point than the last iteration I sent to the LKML.
> >
> >       
> You can send the patches to me if you want and I can see if they're
> useful. I'm really only interested in the color format part though.
> Alternatively, you can continue your work and post it to LKML and I
> can focus on the userspace side and testing. By the way, I have an
> HDMI analyzer that can tell me the actual color format.
>

Searched for what I still had in my private repo, see attachments, filename is the branch name I used and like I said: I don't know which state these branches are in.

The hacking_ branch was based on 25fe90f43fa312213b653dc1f12fd2d80f855883 from linux-next and the rejected_ one on 132b189b72a94328f17fd70321bfe63e5b4208e9 from drm-tip.

And the rejected_ one is 2 weeks newer.

To pick it up again I would first need to allocate some time for it, ... which could take some time.

With a HDMI analyzer at hand you are better equipped then me already. I was working with printf statements, Monitor OSD's and test patterns like https://media.extron.com/public/technology/landing/vector4k/img/scalfe-444Chroma.png and http://www.lagom.nl/lcd-test/ while being red blind xD.

> Thanks,
> Andri
>

Attachment: hacking_drm_color_management_no_immutable_flag.tar.gz
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Attachment: rejected_drm_color_management.tar.gz
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