From mboxrd@z Thu Jan  1 00:00:00 1970
From: Brian Starkey <Brian.Starkey@arm.com>
Subject: Re: [RFC PATCH 18/20] lib: image-formats: Add v4l2 formats support
Date: Wed, 20 Mar 2019 18:15:54 +0000
Message-ID: <20190320181553.radwlhapzn464dlh@DESKTOP-E1NTVVP.localdomain>
References: <cover.92acdec88ee4c280cb74e08ea22f0075e5fa055c.1553032382.git-series.maxime.ripard@bootlin.com>
 <c97024b97d3261dcf41aad3c8bc1c5d9906f33c9.1553032382.git-series.maxime.ripard@bootlin.com>
 <d8f4a31e35b1702230ced4a0cb43c10d1c7e60c8.camel@ndufresne.ca>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
Return-path: <linux-kernel-owner@vger.kernel.org>
In-Reply-To: <d8f4a31e35b1702230ced4a0cb43c10d1c7e60c8.camel@ndufresne.ca>
Content-Language: en-US
Content-ID: <4811124997DA2F4383E90C1A9A8E2083@eurprd08.prod.outlook.com>
Sender: linux-kernel-owner@vger.kernel.org
To: Nicolas Dufresne <nicolas@ndufresne.ca>
Cc: Maxime Ripard <maxime.ripard@bootlin.com>, Daniel Vetter <daniel.vetter@intel.com>, David Airlie <airlied@linux.ie>, Maarten Lankhorst <maarten.lankhorst@linux.intel.com>, Sean Paul <seanpaul@chromium.org>, Mauro Carvalho Chehab <mchehab@kernel.org>, Sakari Ailus <sakari.ailus@linux.intel.com>, Hans Verkuil <hans.verkuil@cisco.com>, Laurent Pinchart <laurent.pinchart@ideasonboard.com>, Thomas Petazzoni <thomas.petazzoni@bootlin.com>, Paul Kocialkowski <paul.kocialkowski@bootlin.com>, "dri-devel@lists.freedesktop.org" <dri-devel@lists.freedesktop.org>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "linux-media@vger.kernel.org" <linux-media@vger.kernel.org>, nd <nd@arm.com>
List-Id: dri-devel@lists.freedesktop.org

On Tue, Mar 19, 2019 at 07:29:18PM -0400, Nicolas Dufresne wrote:
> All RGB mapping should be surrounded by ifdef, because many (not all)
> DRM formats represent the order of component when placed in a CPU
> register, unlike V4L2 which uses memory order. I've pick this one
> randomly, but this one on most system, little endian, will match
> V4L2_PIX_FMT_XBGR32. This type of complex mapping can be found in
> multiple places, notably in GStreamer:
>=20
> https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/blob/master/sys/=
kms/gstkmsutils.c#L45
>=20

I do sort-of wonder if it's worth trying to switch to common fourccs
between DRM and V4L2 (and whatever else there is).

The V4L2 formats list is quite incomplete and a little quirky in
places (V4L2_PIX_FORMAT_XBGR32 and V4L2_PIX_FORMAT_XRGB32 naming
inconsistency being one. 'X' isn't even next to 'B' in XBGR32).

At least for newly-added formats, not using a common definition
doesn't make a lot of sense to me. Longer term, I also don't really
see any downsides to unification.

-Brian