linux-kernel - Re: [PATCH 3/5] dt-bindings: display: simple-bridge: Document DPI color encoder

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Message-ID: <20250304152320.GA2630063-robh@kernel.org>
Date: Tue, 4 Mar 2025 09:23:20 -0600
From: Rob Herring <robh@...nel.org>
To: Liu Ying <victor.liu@....com>
Cc: dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, krzk+dt@...nel.org,
	conor+dt@...nel.org, andrzej.hajda@...el.com,
	neil.armstrong@...aro.org, rfoss@...nel.org,
	Laurent.pinchart@...asonboard.com, jonas@...boo.se,
	jernej.skrabec@...il.com, maarten.lankhorst@...ux.intel.com,
	mripard@...nel.org, tzimmermann@...e.de, airlied@...il.com,
	simona@...ll.ch
Subject: Re: [PATCH 3/5] dt-bindings: display: simple-bridge: Document DPI
 color encoder

On Tue, Mar 04, 2025 at 06:15:28PM +0800, Liu Ying wrote:
> A DPI color encoder, as a simple display bridge, converts input DPI color
> coding to output DPI color coding, like Adafruit Kippah DPI hat[1] which
> converts input 18-bit pixel data to 24-bit pixel data(with 2 low padding
> bits in every color component though). Document the DPI color encoder.

Why do we need a node for this? Isn't this just wired how it is wired 
and there's nothing for s/w to see or do? I suppose if you are trying to 
resolve the mode with 24-bit on one end and 18-bit on the other end, you 
need to allow that and not require an exact match. You still might need 
to figure out which pins the 18-bit data comes out on, but you have that 
problem with an 18-bit panel too. IOW, how is this any different if you 
have an 18-bit panel versus 24-bit panel?

Rob