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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?Nat/862J1OqxLPmXLxlZPBsq++kfq6bMwKkg0njOB+l6FHfcwHAtAlVEwRV0?= =?us-ascii?Q?Nz0ycGHHf5GIi3Hg6B5qk1ZWpRqdKTVXn/D1EzJ0muKW4RFxMwSCsRBS5wl7?= =?us-ascii?Q?oSJ3+qGB2LKUyEtPj5RJzStu4FtoqmRd4zuWPQBdkjPwoIiCr4yKUFlAHpNd?= =?us-ascii?Q?K05YDJI4Xf+o5FmocA/vdQjHkeJnejZSEBkvYKFAKEsAh4NGR6UApitCpABf?= =?us-ascii?Q?ynbifUx6xrUe4wo1zPIana40J3kv1dnV8ixp46To9TMb1Cu+Hd6x64J1MN2M?= =?us-ascii?Q?/Xz83Dlvoy/bOahaMWB0abDgkb1EEwH3DXA1AtTq110KstyZbqVAKmw8+XEK?= =?us-ascii?Q?Ax4Ef8GGCdgsgEyx+e9pWQNzB9Ju4VWeu9UltbsMqyT6NMVW+CnBp55ByXKo?= =?us-ascii?Q?hGz6X8SJ681aNXAqF6UtFWjo17ttiftvU3hvY9UK6YoC+V+v6w+7k5zcFPMU?= =?us-ascii?Q?TjDaqHEoAm+/fj2zqxCauCQzScMZJ4mwbzX5CbogttCx3g34Nzf3MufYCbM2?= =?us-ascii?Q?MdMqEHzwYBBqvHuBJAig/gK+cWLW6dIp51LTsxDFZPoKDwDvyyAoARBPwtiG?= =?us-ascii?Q?tev7S45G7U+XaTLikRHHnL0iUrQg6pld4APx3sGYmOi9BXK4AhGbTaddH8eC?= =?us-ascii?Q?6F10pXHRLtzUuSotJSptAvd5hPufFF3Zu3MvO2VeG99ri1YSPoA2VBKN0xRW?= =?us-ascii?Q?w5n/B+z4+00ld/LOg7K5Y5vmTlA+Ya/IjDUxnWcRfTve/p0++eiOyY6kwDyN?= =?us-ascii?Q?FGz04zgO2YqNabwDT6X7xdy5xw0/ICHowhecdPMCy4MD1Fh+2ZbTB6PSNqCq?= =?us-ascii?Q?he50g94B7L6ZBFXu7ccao1/B1b/2QYKU/uOjKnGcD+qp6/pmvzu3di3Er5aD?= =?us-ascii?Q?aScAs3qS6KwgiQkwbySlbA6lMr+6uVf0xdGOLTgfUgGZasNWeElOqyB3SQjX?= =?us-ascii?Q?GSxHu3iP7FO69ZALTCd2uWp//UaF3ClTb4GTJv26fiuCqw78eMeGNk7l+ZoA?= =?us-ascii?Q?Dx9y3anVmLyfN+ri+/h2YWup1fXUPnZPuHAuNukAkPwMzht4HVLK7wl4xRfz?= =?us-ascii?Q?/Monf5l4tO9d2ROgPE//lLMBiBB10t01J/lUE+keMIucFMMTrPKfW4INK+GM?= =?us-ascii?Q?EmzhGJZITJwMa35I2TNuAjb83e2WQJAkR4yQ1AdEeIdrla6ELzMDlBlQhnLx?= =?us-ascii?Q?h3/RWM2sJeIZHy1A5kM4gSg4TEPGuT89bZbvXaaB85X34trFYsKeI/sd56pa?= =?us-ascii?Q?IXF1RICm9cNVyJAtYNpU8w7ESbl2FZbz4g7m4Ydey8Gmfm2TeNLmpMSgmBBt?= =?us-ascii?Q?u/i0oB9gSn6BSyB7WFybh+o4rBc+VcG3D7RoDC6dgDfA1H5XfGQPzTtHKyaN?= =?us-ascii?Q?zRYKzROe5svA5jG3w224tdliWoRMqerGXIAgMBcbGOCgEisJH3UXWtWmLAqh?= =?us-ascii?Q?xSljqW8OvzVLFx18Yr0HabwpKvY/DCCSeGP4DO+MNB/VqmUVFdyCc1yKpFYZ?= =?us-ascii?Q?H47+Vj2WfJOu0MzSO1wmovZGz/mONxpR8tPNaAxZZWJQNToQMwRmh20spt3O?= =?us-ascii?Q?PqFKHe6i/KM1CRLjS1w=3D?= X-MS-Exchange-CrossTenant-Network-Message-Id: e40fb718-eebe-43f9-ad0a-08db6c20fb92 X-MS-Exchange-CrossTenant-AuthSource: HE1PR02MB3227.eurprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Jun 2023 15:15:12.0426 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 78703d3c-b907-432f-b066-88f7af9ca3af X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: pH7Ku7elyG+Q0jFNjg457/Yruu3RmccjVMt6bwhikIixABFlq4v/IfWhazv25/r+BoZxmMK7pmUp1Fp3hrPhhw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DU0PR02MB9194 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 13 Jun 2023, Greg Kroah-Hartman wrote: > On Tue, Jun 13, 2023 at 01:42:27PM +0200, Waqar Hameed wrote: > > `_regmap_update_bits()` checks if the current register value differs > > from the new value, and only writes to the register if they differ. When > > > > + /* > > + * This could interfere with driver operation. Therefore, don't provide > > + * any real compile time configuration option for this feature. One will > > + * have to modify the source code directly in order to use it. > > + */ > > +#undef REGMAP_ALLOW_FORCE_WRITE_FIELD_DEBUGFS > > +#ifdef REGMAP_ALLOW_FORCE_WRITE_FIELD_DEBUGFS > > + debugfs_create_bool("force_write_field", 0600, map->debugfs, > > + &map->force_write_field); > > +#endif > > Please no, that means this will never ever ever get used, and if it > happens to break the build or runtime, no one will ever notice it. > > If you need this for your device/tree/distro, great, just keep it as an > out-of-tree patch with the huge header "NEVER ENABLE THIS IN A REAL > SYSTEM" or something like that. The ordinary only-write-if-bits-have-changed behavior of _regmap_update_bits would seem to be mostly an optimization to minimize the number of writes to a device. The way it is normally used in the code, it's not easy to predict when it in fact will result in a write, because the whole idea of a function like this is that a driver doesn't have to keep track of which bits are actually set or not, or else the function would not be useful in the first place. I can understand that enabling a write-always behavior results in a different behavior on the associated bus (e.g. I2C), but in the end it shouldn't affect the functionality of the peripheral device any more than rearranging driver code to perform regmap writes in a different order, which might also lead to fewer or more bus writes. It seems I'm clearly in the wrong here, so there must be some scenario I've missed. It just doesn't seem that dangerous; it's a debug functionality after all. /Ricard -- Ricard Wolf Wanderlof ricardw(at)axis.com Axis Communications AB, Lund, Sweden www.axis.com Phone +46 46 272 2016 Fax +46 46 13 61 30