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

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Date: Fri, 1 Mar 2024 14:19:00 +0200
From: Pekka Paalanen <pekka.paalanen@...labora.com>
To: Maxime Ripard <mripard@...nel.org>
Cc: Sebastian Wick <sebastian.wick@...hat.com>, Maarten Lankhorst
 <maarten.lankhorst@...ux.intel.com>, Thomas Zimmermann
 <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, Daniel Vetter
 <daniel@...ll.ch>, Jonathan Corbet <corbet@....net>, Sandy Huang
 <hjc@...k-chips.com>, Heiko Stübner <heiko@...ech.de>,
 Chen-Yu Tsai <wens@...e.org>, Jernej Skrabec <jernej.skrabec@...il.com>,
 Samuel Holland <samuel@...lland.org>, Hans Verkuil <hverkuil@...all.nl>,
 Ville Syrjälä <ville.syrjala@...ux.intel.com>,
 dri-devel@...ts.freedesktop.org, linux-arm-kernel@...ts.infradead.org,
 linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-media@...r.kernel.org, linux-rockchip@...ts.infradead.org,
 linux-sunxi@...ts.linux.dev, Dave Stevenson
 <dave.stevenson@...pberrypi.com>
Subject: Re: [PATCH v7 21/36] drm/connector: hdmi: Add Broadcast RGB
 property

On Fri, 1 Mar 2024 13:12:02 +0100
Maxime Ripard <mripard@...nel.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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