Re: [PATCH v7 21/36] drm/connector: hdmi: Add Broadcast RGB property

Pekka Paalanen
2024-03-01T12:19:23Z

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On Fri, 1 Mar 2024 13:12:02 +0100
Maxime Ripard <mripard@kernel.org> wrote:

> On Fri, Mar 01, 2024 at 12:29:41PM +0100, Sebastian Wick wrote:
> > On Fri, Mar 01, 2024 at 11:30:56AM +0100, Maxime Ripard wrote:
> > > On Thu, Feb 29, 2024 at 08:47:26PM +0100, Sebastian Wick wrote:
> > > > > @@ -1708,6 +1731,39 @@ EXPORT_SYMBOL(drm_connector_attach_dp_subconnector_property);
> > > > > /**
> > > > > * DOC: HDMI connector properties
> > > > > *
> > > > > + * Broadcast RGB (HDMI specific)
> > > > > + * Indicates the Quantization Range (Full vs Limited) used. The color
> > > > > + * processing pipeline will be adjusted to match the value of the
> > > > > + * property, and the Infoframes will be generated and sent accordingly.
> > > > > + *
> > > > > + * This property is only relevant if the HDMI output format is RGB. If
> > > > > + * it's one of the YCbCr variant, it will be ignored and the output will
> > > > > + * use a limited quantization range.
> > > >
> > > > Uh, maybe just say that the quantization range is selected automatically
> > > > in case a YCbCr output format is in use. I'm not sure every YCbCr
> > > > variant requires limited and even if it does, new formats could change
> > > > this.
> > >
> > > I documented what i915 is doing:
> > > https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/i915/display/intel_hdmi.c#L2143
> >
> > Sure, this is one valid strategy for the automatic behavior of YCbCr.
> > Drivers could also always send an InfoFrame to ensure full range where
> > possible. The point here is that this property shall not affect YCbCr
> > output formats!
> >
> > Maybe it's even better to say "driver specific" instead of "automatic".
>
> Honestly, I'm not sure what you want from me here. Ville and you
> insisted on the previous version to document what i915 is doing and to
> follow whatever the behaviour was, and that we shouldn't spend time
> improving the property. Fine, I did that.
>
> But now, you want me to ... improve the property?

Just drop the "and the output will use a limited quantization range"
part.

Thanks,
pq

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