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reading data in reversed host ordering To: Petr Mladek , alyssa@rosenzweig.io, Andy Shevchenko , Sven Peter , Thomas Zimmermann , Aun-Ali Zaidi , Maxime Ripard , airlied@redhat.com, Simona Vetter , Steven Rostedt , Rasmus Villemoes , Sergey Senozhatsky , Jonathan Corbet , Andrew Morton , apw@canonical.com, joe@perches.com, dwaipayanray1@gmail.com, lukas.bulwahn@gmail.com, Kees Cook , tamird@gmail.com Cc: Linux Kernel Mailing List , dri-devel@lists.freedesktop.org, linux-doc@vger.kernel.org, Hector Martin , Asahi Linux Mailing List , Geert Uytterhoeven References: <20250428123132.578771-1-pmladek@suse.com> Content-Language: en-US From: Aditya Garg In-Reply-To: <20250428123132.578771-1-pmladek@suse.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: BMXPR01CA0096.INDPRD01.PROD.OUTLOOK.COM (2603:1096:b00:54::36) To PN3PR01MB9597.INDPRD01.PROD.OUTLOOK.COM (2603:1096:c01:f7::14) X-Microsoft-Original-Message-ID: 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X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 84df9e7f-e9f6-40af-b435-aaaaaaaaaaaa X-MS-Exchange-CrossTenant-RMS-PersistedConsumerOrg: 00000000-0000-0000-0000-000000000000 X-MS-Exchange-Transport-CrossTenantHeadersStamped: MA0PR01MB9497 Hi Petr > The generic FourCC format always prints the data using the big endian > order. It is generic because it allows to read the data using a custom > ordering. > > The current code uses "n" for reading data in the reverse host ordering. > It makes the 4 variants [hnbl] consistent with the generic printing > of IPv4 addresses. > > Unfortunately, it creates confusion on big endian systems. For example, > it shows the data &(u32)0x67503030 as > > %p4cn 00Pg (0x30305067) > > But people expect that the ordering stays the same. The network ordering > is a big-endian ordering. > > The problem is that the semantic is not the same. The modifiers affect > the output ordering of IPv4 addresses while they affect the reading order > in case of FourCC code. > > Avoid the confusion by replacing the "n" modifier with "hR", aka > reverse host ordering. It is inspired by the existing %p[mM]R printf > format. > > Reported-by: Geert Uytterhoeven > Closes: https://lore.kernel.org/r/CAMuHMdV9tX=TG7E_CrSF=2PY206tXf+_yYRuacG48EWEtJLo-Q@mail.gmail.com > Signed-off-by: Petr Mladek > --- I just realised you forgot to fix checkpatch.pl with your update: https://gitlab.freedesktop.org/drm/misc/kernel/-/blob/1938479b2720ebc05aab349c7dc0a53921ff7c87/scripts/checkpatch.pl#L6894