From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2C63FC43381 for ; Fri, 22 Mar 2019 14:42:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 074D32190A for ; Fri, 22 Mar 2019 14:42:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729068AbfCVOmT (ORCPT ); Fri, 22 Mar 2019 10:42:19 -0400 Received: from mga02.intel.com ([134.134.136.20]:30471 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727719AbfCVOmT (ORCPT ); Fri, 22 Mar 2019 10:42:19 -0400 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orsmga101.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 22 Mar 2019 07:42:18 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.60,256,1549958400"; d="scan'208";a="216591125" Received: from stinkbox.fi.intel.com (HELO stinkbox) ([10.237.72.174]) by orsmga001.jf.intel.com with SMTP; 22 Mar 2019 07:42:11 -0700 Received: by stinkbox (sSMTP sendmail emulation); Fri, 22 Mar 2019 16:42:10 +0200 Date: Fri, 22 Mar 2019 16:42:10 +0200 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: Nicolas Dufresne Cc: Paul Kocialkowski , Maxime Ripard , Daniel Vetter , David Airlie , Maarten Lankhorst , Sean Paul , Mauro Carvalho Chehab , Sakari Ailus , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, Hans Verkuil , Laurent Pinchart , Thomas Petazzoni , linux-media@vger.kernel.org, Daniel Stone Subject: Re: [RFC PATCH 18/20] lib: image-formats: Add v4l2 formats support Message-ID: <20190322144210.GB3888@intel.com> References: <20190320142739.GK3888@intel.com> <20190320160939.GR3888@intel.com> <20190320164133.GT3888@intel.com> <20190320183914.GV3888@intel.com> <46df4fb13636b90c147839b0aa5ad1ac33030461.camel@bootlin.com> <20190321163532.GG3888@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 21, 2019 at 03:14:06PM -0400, Nicolas Dufresne wrote: > Le jeudi 21 mars 2019 ā 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