From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: Nicolas Dufresne <nicolas@ndufresne.ca>
Cc: Paul Kocialkowski <paul.kocialkowski@bootlin.com>,
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>,
linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
Hans Verkuil <hans.verkuil@cisco.com>,
Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
linux-media@vger.kernel.org, Daniel Stone <daniels@collabora.com>
Subject: Re: [RFC PATCH 18/20] lib: image-formats: Add v4l2 formats support
Date: Fri, 22 Mar 2019 16:42:10 +0200 [thread overview]
Message-ID: <20190322144210.GB3888@intel.com> (raw)
In-Reply-To: <ac5329d77f83af2804c240ebe479ec323b60aec3.camel@ndufresne.ca>
On Thu, Mar 21, 2019 at 03:14:06PM -0400, Nicolas Dufresne wrote:
> Le jeudi 21 mars 2019 à 18:35 +0200, Ville Syrjälä a écrit :
> > > I'm not sure what it's worth, but there is a "pixel format guide"
> > > project that is all about matching formats from one API to another:
> > > https://afrantzis.com/pixel-format-guide/ (and it has an associated
> > > tool too).
> > >
> > > On the page about DRM, it seems that they got the word that DRM formats
> > > are the native pixel order in little-endian systems:
> > > https://afrantzis.com/pixel-format-guide/drm.html
> >
> > Looks consistent with the official word in drm_fourcc.h.
> >
> > $ python3 -m pfg find-compatible V4L2_PIX_FMT_XBGR32 drm
> > Format: V4L2_PIX_FMT_XBGR32
> > Is compatible on all systems with:
> > DRM_FORMAT_XRGB8888
> > Is compatible on little-endian systems with:
> > Is compatible on big-endian systems with:
> >
> > $ python3 -m pfg find-compatible DRM_FORMAT_XRGB8888 v4l2
> > Format: DRM_FORMAT_XRGB8888
> > Is compatible on all systems with:
> > V4L2_PIX_FMT_XBGR32
> > Is compatible on little-endian systems with:
> > Is compatible on big-endian systems with:
> >
> > Even works both ways :)
> >
> > > Perhaps some drivers have been abusing the format definitions, leading
> > > to the inconsistencies that Nicolas could witness?
> >
> > That is quite possible, perhaps even likely. No one really
> > seems interested in making sure big endian systems actually
> > work properly. I believe the usual approach is to hack
> > around semi-rnadomly until the correct colors accidentally
> > appear on the screen.
>
> We did not hack around randomly.
BTW I didn't mean to imply it was you who hacked around randomly.
Sorry if you got that impression.
What I was trying to convey is the following sequence of events:
1. random person X gets their hand on a big endian machine for
a while
2. colors are wrong
3. they hack stuff until the colors are correct in their
current use case
4. they move on to more interesting things
--
Ville Syrjälä
Intel
next prev parent reply other threads:[~2019-03-22 14:42 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-19 21:57 [RFC PATCH 00/20] drm: Split out the formats API and move it to a common place Maxime Ripard
2019-03-19 21:57 ` [RFC PATCH 01/20] drm: Remove users of drm_format_num_planes Maxime Ripard
2019-03-20 14:16 ` Paul Kocialkowski
2019-04-02 9:43 ` Emil Velikov
2019-04-02 14:51 ` Maxime Ripard
2019-04-04 16:24 ` Emil Velikov
2019-03-19 21:57 ` [RFC PATCH 02/20] drm: Remove users of drm_format_(horz|vert)_chroma_subsampling Maxime Ripard
2019-03-20 14:19 ` Paul Kocialkowski
2019-03-19 21:57 ` [RFC PATCH 03/20] drm/fourcc: Pass the format_info pointer to drm_format_plane_cpp Maxime Ripard
2019-03-20 14:24 ` Paul Kocialkowski
2019-03-21 10:13 ` Maxime Ripard
2019-03-19 21:57 ` [RFC PATCH 04/20] drm/fourcc: Pass the format_info pointer to drm_format_plane_width/height Maxime Ripard
2019-03-20 14:26 ` Paul Kocialkowski
2019-03-19 21:57 ` [RFC PATCH 05/20] drm: Replace instances of drm_format_info by drm_get_format_info Maxime Ripard
2019-03-20 14:27 ` Paul Kocialkowski
2019-03-19 21:57 ` [RFC PATCH 06/20] lib: Add video format information library Maxime Ripard
2019-03-20 13:39 ` Boris Brezillon
2019-03-21 8:20 ` Maxime Ripard
2019-03-21 8:40 ` Boris Brezillon
2019-03-19 21:57 ` [RFC PATCH 07/20] drm/fb: Move from drm_format_info to image_format_info Maxime Ripard
2019-03-19 21:57 ` [RFC PATCH 08/20] drm/malidp: Convert to generic image format library Maxime Ripard
2019-03-19 21:57 ` [RFC PATCH 09/20] drm/client: " Maxime Ripard
2019-03-19 21:57 ` [RFC PATCH 10/20] drm/exynos: " Maxime Ripard
2019-03-19 21:57 ` [RFC PATCH 11/20] drm/i915: " Maxime Ripard
2019-03-19 21:57 ` [RFC PATCH 12/20] drm/ipuv3: " Maxime Ripard
2019-03-19 21:57 ` [RFC PATCH 13/20] drm/msm: " Maxime Ripard
2019-03-19 21:57 ` [RFC PATCH 14/20] drm/omap: " Maxime Ripard
2019-03-19 21:57 ` [RFC PATCH 15/20] drm/rockchip: " Maxime Ripard
2019-03-19 21:57 ` [RFC PATCH 16/20] drm/tegra: " Maxime Ripard
2019-03-19 21:57 ` [RFC PATCH 17/20] drm/fourcc: Remove old DRM format API Maxime Ripard
2019-03-19 21:57 ` [RFC PATCH 18/20] lib: image-formats: Add v4l2 formats support Maxime Ripard
2019-03-19 23:29 ` Nicolas Dufresne
2019-03-20 14:27 ` Ville Syrjälä
2019-03-20 15:51 ` Nicolas Dufresne
[not found] ` <20190320160939.GR3888@intel.com>
2019-03-20 16:30 ` Nicolas Dufresne
[not found] ` <20190320164133.GT3888@intel.com>
2019-03-20 18:27 ` Nicolas Dufresne
2019-03-20 18:39 ` Ville Syrjälä
2019-03-21 16:04 ` Paul Kocialkowski
2019-03-21 16:35 ` Ville Syrjälä
2019-03-21 19:14 ` Nicolas Dufresne
2019-03-21 21:44 ` Ville Syrjälä
2019-03-22 18:24 ` Nicolas Dufresne
2019-03-22 18:44 ` Ville Syrjälä
2019-03-22 19:25 ` Nicolas Dufresne
2019-03-22 14:42 ` Ville Syrjälä [this message]
2019-03-22 18:11 ` Nicolas Dufresne
2019-03-20 18:15 ` Brian Starkey
2019-03-21 15:47 ` Maxime Ripard
2019-03-22 19:55 ` Nicolas Dufresne
2019-04-01 14:44 ` Maxime Ripard
2019-04-11 7:24 ` Hans Verkuil
2019-04-11 7:38 ` Hans Verkuil
2019-04-11 15:55 ` Maxime Ripard
2019-04-11 7:12 ` Hans Verkuil
2019-04-11 7:15 ` Hans Verkuil
2019-03-19 21:57 ` [RFC PATCH 19/20] lib: image-formats: Add more functions Maxime Ripard
2019-03-19 21:57 ` [RFC PATCH 20/20] media: sun6i: Convert to the image format API Maxime Ripard
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