linux-kernel - Re: Re: Re: [PATCH v5 08/44] drm/connector: hdmi: Add Broadcast RGB property

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Message-ID: <uplclresnokchsgutsd27ihv4422sob77reobw6ygx3c3cqnti@hjmrhut7l5r5>
Date: Mon, 12 Feb 2024 10:55:32 +0100
From: Maxime Ripard <mripard@...nel.org>
To: Sebastian Wick <sebastian.wick@...hat.com>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, 
	Daniel Vetter <daniel@...ll.ch>, Emma Anholt <emma@...olt.net>, 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>, linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, 
	dri-devel@...ts.freedesktop.org, Hans Verkuil <hverkuil@...all.nl>, 
	linux-rockchip@...ts.infradead.org, linux-sunxi@...ts.linux.dev, 
	linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org
Subject: Re: Re: Re: [PATCH v5 08/44] drm/connector: hdmi: Add Broadcast RGB
 property

On Fri, Feb 09, 2024 at 09:30:46PM +0100, Sebastian Wick wrote:
> On Fri, Feb 02, 2024 at 04:49:04PM +0100, Maxime Ripard wrote:
> > Hi Sebastian,
> > 
> > On Mon, Jan 15, 2024 at 03:33:08PM +0100, Sebastian Wick wrote:
> > > >  /**
> > > >   * DOC: HDMI connector properties
> > > >   *
> > > > + * Broadcast RGB
> > > > + *      Indicates the RGB Quantization Range (Full vs Limited) used.
> > > > + *      Infoframes will be generated according to that value.
> > > > + *
> > > > + *      The value of this property can be one of the following:
> > > > + *
> > > > + *      Automatic:
> > > > + *              RGB Range is selected automatically based on the mode
> > > > + *              according to the HDMI specifications.
> > > > + *
> > > > + *      Full:
> > > > + *              Full RGB Range is forced.
> > > > + *
> > > > + *      Limited 16:235:
> > > > + *              Limited RGB Range is forced. Unlike the name suggests,
> > > > + *              this works for any number of bits-per-component.
> > > > + *
> > > > + *      Drivers can set up this property by calling
> > > > + *      drm_connector_attach_broadcast_rgb_property().
> > > > + *
> > > 
> > > This is a good time to document this in more detail. There might be two
> > > different things being affected:
> > > 
> > > 1. The signalling (InfoFrame/SDP/...)
> > > 2. The color pipeline processing
> > > 
> > > All values of Broadcast RGB always affect the color pipeline processing
> > > such that a full-range input to the CRTC is converted to either full- or
> > > limited-range, depending on what the monitor is supposed to accept.
> > > 
> > > When automatic is selected, does that mean that there is no signalling,
> > > or that the signalling matches what the monitor is supposed to accept
> > > according to the spec? Also, is this really HDMI specific?
> > > 
> > > When full or limited is selected and the monitor doesn't support the
> > > signalling, what happens?
> > 
> > Leaving the YCbCr vs RGB discussion aside, would this be better ?
> 
> Yes, it is. Thanks.

Great, it'll be in the next version.

> We do have to resolve the YCbCr vs RGB issue though.
> 
> >  * 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
> 
> Ah, another thing no note here is that the CRTC as configured by user
> space must always produce full range pixels.

Added too

Thanks

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