Re: [PATCH 3/3] drm/connector: Deprecate split for BT.2020 in drm_colorspace enum

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Fri, Feb 03, 2023 at 09:39:42AM -0500, Harry Wentland wrote:
> 
> 
> On 2/3/23 07:59, Sebastian Wick wrote:
> > On Fri, Feb 3, 2023 at 11:40 AM Ville Syrjälä
> > <ville.syrjala@linux.intel.com> wrote:
> >>
> >> On Fri, Feb 03, 2023 at 02:07:44AM +0000, Joshua Ashton wrote:
> >>> Userspace has no way of controlling or knowing the pixel encoding
> >>> currently, so there is no way for it to ever get the right values here.
> >>
> >> That applies to a lot of the other values as well (they are
> >> explicitly RGB or YCC). The idea was that this property sets the
> >> infoframe/MSA/SDP value exactly, and other properties should be
> >> added to for use userspace to control the pixel encoding/colorspace
> >> conversion(if desired, or userspace just makes sure to
> >> directly feed in correct kind of data).
> > 
> > I'm all for getting userspace control over pixel encoding but even
> > then the kernel always knows which pixel encoding is selected and
> > which InfoFrame has to be sent. Is there a reason why userspace would
> > want to control the variant explicitly to the wrong value?
> > 
> 
> I've asked this before but haven't seen an answer: Is there an existing
> upstream userspace project that makes use of this property (other than
> what Joshua is working on in gamescope right now)? That would help us
> understand the intent better.

The intent was to control the infoframe colorimetry bits,
nothing more. No idea what real userspace there was, if any.

> 
> I don't think giving userspace explicit control over the exact infoframe
> values is the right thing to do.

Only userspace knows what kind of data it's stuffing into
the pixels (and/or how it configures the csc units/etc.) to
generate them.

I really don't want a repeat of the disaster of the
'Broadcast RGB' which has coupled together the infoframe 
and automagic conversion stuff. And I think this one would
be about 100x worse given this property has something
to do with actual colorspaces as well.
 
-- 
Ville Syrjälä
Intel