linux-kernel - Re: [PATCH 0/4] media: Fix CSI2 RGB vs BGR pixel order

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Message-ID: <20250618-qualified-moth-of-infinity-cc6b0c@houat>
Date: Wed, 18 Jun 2025 10:48:47 +0200
From: Maxime Ripard <mripard@...nel.org>
To: Hans Verkuil <hans@...erkuil.nl>
Cc: Mauro Carvalho Chehab <mchehab@...nel.org>, 
	Hans Verkuil <hverkuil@...all.nl>, Mats Randgaard <matrandg@...co.com>, 
	Alain Volmat <alain.volmat@...s.st.com>, Sakari Ailus <sakari.ailus@...ux.intel.com>, 
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Dave Stevenson <dave.stevenson@...pberrypi.com>
Subject: Re: [PATCH 0/4] media: Fix CSI2 RGB vs BGR pixel order

Hi Hans,

On Mon, Jun 16, 2025 at 10:02:57AM +0200, Hans Verkuil wrote:
> On 12/06/2025 14:53, Maxime Ripard wrote:
> > Here's an(other [1]) attempt at fixing the current mess due to the
> > opposite meaning of what v4l2 and the MIPI-CSI2 spec call "RGB". By v4l2
> > nomenclature, the format CSI calls RGB is actually BGR.
> > 
> > Unfortunately, a handful of CSI transceivers report through RGB media
> > bus pixel code, which is then understood as V4L2_PIX_FMT_RGB24 by CSI
> > receivers.
> > 
> > This is made somewhat worse the fact that media bus codes have been made
> > mostly with parallel busses in mind, and thus the order of pixels wasn't
> > clearly defined anywhere.
> > 
> > So the v4l2 vs CSI mismatch was confusing (but there's nothing we can do
> > about it), but the doc didn't really make an attempt at clearing it up
> > either.
> > 
> > We did have a convention so far though, that about half the affected
> > drivers were following. 
> > 
> > This series improves the doc, adds the missing media bus codes, and
> > converts the transceiver drivers to the rightful media bus format.
> > 
> > We'll also need that series [2] from Laurent to fix all the affected
> > transceivers. 
> > 
> > Let me know what you think,
> > Maxime
> > 
> > 1: https://lore.kernel.org/r/20250606-rpi-unicam-rgb-bgr-fix-v1-1-9930b963f3eb@kernel.org
> > 2: https://lore.kernel.org/r/20250611181528.19542-1-laurent.pinchart@ideasonboard.com
> 
> This link seems to be wrong. Can you give the correct URL?

Yeah, sorry about that. Laurent sent a series to a bunch of us after
discussing it in private, but I assumed it was public.

Hopefully he'll post it soon :)

Maxime

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