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Tue, 14 Jul 2020 08:54:17 +0000 Subject: Re: [PATCH] spi: spidev: Add compatible for external SPI ports on Kontron boards To: Mark Brown Cc: linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org References: <20200702141846.7752-1-frieder.schrempf@kontron.de> <20200702142511.GF4483@sirena.org.uk> <24ec4eed-de01-28df-ee1f-f7bcfc80051a@kontron.de> <20200702150725.GI4483@sirena.org.uk> <479d566a-213f-4e33-8ac7-7637ae88e31c@kontron.de> <20200713151108.GB4420@sirena.org.uk> From: Frieder Schrempf Message-ID: <2eb6971b-7ea4-c9c8-5452-6f4b17e8860a@kontron.de> Date: Tue, 14 Jul 2020 10:54:15 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 In-Reply-To: <20200713151108.GB4420@sirena.org.uk> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: AM0PR02CA0079.eurprd02.prod.outlook.com (2603:10a6:208:154::20) To DB7PR10MB2490.EURPRD10.PROD.OUTLOOK.COM (2603:10a6:10:50::12) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [192.168.99.63] (80.147.118.32) by AM0PR02CA0079.eurprd02.prod.outlook.com (2603:10a6:208:154::20) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3174.20 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: 6YYE6bwsWAc1g48CZYSW39kOwi9MBrsvUU+Y/zG+XO0m9krhLYJpt9DZdeuI/JvPMQCGjnBRVgSClGIQecGeqow6sm9XYn7w0ksAEvvsmvvtfJN0rmbcZFsc/LO4m1aap0zx+VB2YEK8VoNEfCXICQQyXtgEvo/TMWB11r8iQImcL3hqglRt9G9B+jgI6AMqN54HgTnTEcgDbGPdreD/joumI5uGMZuenfmZK2qBIyRM3Uw99dvQw+ATeLZLGZ/3KZ/Mr5ihi68t4KDXKWQKTi+FalDQfVHCWO7w91SL2aK3G4WiXruwNP2fEEwUfWUsShCX1IPRHtZvqz9pMTrsUgN8+F7fYyxU01m9uB5GKDZsQnCTmTwO6pQ2+2r6LlARBBb4Od+Nmf2a45YxT9WWJQ8QIhYcBX4icyIlKzo//BhJWQrTbv0o4Q6zt1goiqGL0Mfk3RBKjRSN8WhfZdJ91g9Vnr+lfUiFz9/4hj9z/ns= X-OriginatorOrg: kontron.de X-MS-Exchange-CrossTenant-Network-Message-Id: 7a3aa5c4-18ac-4b1c-63ed-08d827d37da3 X-MS-Exchange-CrossTenant-AuthSource: DB7PR10MB2490.EURPRD10.PROD.OUTLOOK.COM X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 14 Jul 2020 08:54:17.4736 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 8c9d3c97-3fd9-41c8-a2b1-646f3942daf1 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: g4JVprxkDccXSTUcrXodhzOw3XXA7s0QYgKUGzOUNelIyAim9Nc5YKVlwfOkvD35b1qhrT550/gJwFHOzE8puNojulOwOOEacJK7lpwgqgQ= X-MS-Exchange-Transport-CrossTenantHeadersStamped: DB8PR10MB3276 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 13.07.20 17:11, Mark Brown wrote: > On Mon, Jul 13, 2020 at 03:19:52PM +0200, Frieder Schrempf wrote: > >> I would have expected that there is some kind of existing userspace API to >> load an overlay manually, but it seems like there isn't!? > >> So what's the reasoning behind this? How can I solve this in a >> mainline-compliant way, meaning without either keeping downstream patches to >> bind spidev to my device or writing and maintaining code that does the >> overlay loading? > > Basically the reasoning is that nobody's done it rather than any grand > design not to do it. There's some issues for more complex connectors > present on multiple boards with mapping the same connector onto multiple > boards where a resource on the connector might be provided by different > things on the base board so it's not quite as trivial for them as it > should be. Ok, thanks. I'm afraid I'm currently not in the position to work on any generic solution to leverage the loading of DT overlays from userspace. It would still be quite nice to benefit from the flexibility of DT overlays not only for the SPI use case. But before I come up with any custom solution, for now I will rather have the device in the DT statically. I just wonder if I need to keep the DT node for the device in a separate patch in our own tree, or if a node with a custom compatible string like for example "kontron,user-spi" would be accepted upstream, without a matching driver?