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dkim=none (message not signed) header.d=none;dmarc=fail action=none header.from=foss.st.com; Received-SPF: Fail (protection.outlook.com: domain of foss.st.com does not designate 164.130.1.60 as permitted sender) receiver=protection.outlook.com; client-ip=164.130.1.60; helo=smtpO365.st.com; Received: from smtpO365.st.com (164.130.1.60) by DB1PEPF000509E4.mail.protection.outlook.com (10.167.242.54) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9632.12 via Frontend Transport; Fri, 20 Feb 2026 09:16:45 +0000 Received: from STKDAG1NODE2.st.com (10.75.128.133) by smtpO365.st.com (10.250.44.72) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.29; Fri, 20 Feb 2026 10:18:31 +0100 Received: from [10.48.87.127] (10.48.87.127) by STKDAG1NODE2.st.com (10.75.128.133) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.29; Fri, 20 Feb 2026 10:16:43 +0100 Message-ID: Date: Fri, 20 Feb 2026 10:16:42 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v8 3/4] gpio: rpmsg: add generic rpmsg GPIO driver To: Andrew Lunn CC: Shenwei Wang , Linus Walleij , Bartosz Golaszewski , Jonathan Corbet , "Rob Herring" , Krzysztof Kozlowski , "Conor Dooley" , Bjorn Andersson , "Mathieu Poirier" , Frank Li , "Sascha Hauer" , Shuah Khan , , , , Pengutronix Kernel Team , Fabio Estevam , Peng Fan , , , , , , "Bartosz Golaszewski" References: <20260212213656.662437-1-shenwei.wang@nxp.com> <20260212213656.662437-4-shenwei.wang@nxp.com> <13f9d767-61d6-4e29-b36e-6dcc860ccb11@lunn.ch> Content-Language: en-US From: Arnaud POULIQUEN In-Reply-To: <13f9d767-61d6-4e29-b36e-6dcc860ccb11@lunn.ch> Content-Type: text/plain; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: 7m6Px0QhvFi6zktGHOAMR1HOp0llNQ2TIMBdpMHMphhSRXm5BP2bQam1pvTq49TPmXLkpYQ2xpAmkOFFKQ6Z0vZRDrHgYNa4/v0iwOjNsEoItB3dCP+Dmr0M7FcHEzgpnt/9GThMj/JNazhe01x3vGlQU8xCNrFFT9MsoAmcJQPFpzUBQ65eSx/wdH5LLximtPdcjM1TslOYnvNAqj14dM183Iq1fZnMpem/RB8Ju0l0V5os+NX8BaqF3c09fz2xbK3QOYDLF9gz49AjOqIWWQ9XB4PVWuxg3s9lSwV539za97xc+M2QQ4TejnfjyFVhHQ1vx51fSS3/ePfc4AkxXTAGOGbKUqRILw2t/6XLYr/8mHRTrPRzVfWF6sdF94UrINfKMXbQduDcNaew5ILsUaa/b7UL5abQiQXyOZCac86TvIGjrIf4PKLzNc9FBj+k X-OriginatorOrg: foss.st.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 20 Feb 2026 09:16:45.3695 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: d9671b7d-2ddc-4b3e-cea1-08de7060c4d6 X-MS-Exchange-CrossTenant-Id: 75e027c9-20d5-47d5-b82f-77d7cd041e8f X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=75e027c9-20d5-47d5-b82f-77d7cd041e8f;Ip=[164.130.1.60];Helo=[smtpO365.st.com] X-MS-Exchange-CrossTenant-AuthSource: DB1PEPF000509E4.eurprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: AS2PR10MB6614 On 2/19/26 14:42, Andrew Lunn wrote: >>> + u8 id; /* Message ID Code */ >>> + u8 vendor; /* Vendor ID number */ >> >> Does this fields above are mandatory, seems that it is just some constant >> values that are useless. >> >>> + u8 version; /* Vendor-specific version number */ >> >> Why it is vendor specific? the version should represent the rpmsg-tty >> protocol version. >> >>> + u8 type; /* Message type */ >>> + u8 cmd; /* Command code */ >>> + u8 reserved[5]; >> >> What is the purpose of this reserved field? > > They have an implementation of the other end running on there systems, > and it sounds like it is widely deployed, and they are trying to keep > backwards compatibility. The protocol also implements more than > GPIO. There is also I2C, maybe watchdog, i don't remember, but early > versions of this patchset had a list. Some of these fields are used > for some of these other devices. > > I've been arguing it should be a clean design, with the protocol > focusing on GPIO. And that the rpmsg channel makes it clear this is a > GPIO device, the protocol itself does not need to include fields to > differentiate between GPIO, I2C etc. > > When they start submitting I2C over rpmsg, i expect the same sort of > discussion will start again, so the likelihood of keeping backwards > compatible with there firmware seems low to me. Agree with you. Thanks, Arnaud > > Andrew