From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mout02.posteo.de (mout02.posteo.de [185.67.36.66]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EFCE236920E for ; Fri, 20 Mar 2026 21:08:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.67.36.66 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774040906; cv=none; b=ZP916dqzyeJFO4Lep0dZAJsB7kkt23f19g9pSfFaaEXxTlT2NuyAD+bH+YlHE9Tjvccs9DdajhosFyK7e7uI4i0NyDYsyS70UZVE9oczJN6UX5iU+5iCVo533+N/gD5D7t0HWRu2hbiNKAwEXuFtSZUk9gzRkp5tSuaRX/5sXR4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774040906; c=relaxed/simple; bh=bOXHsWAp1TX0zN8K8H757WiBAvP7U7qBrrbxGi3Pp24=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=smgCaoGNjoR7bZpy4RKbUGuv0sMkAXig4QtBPQ3NsSboa8OMvA18285P8KVcXBw1PXFZPFOgggj783/UA7SRw3nWpHbvQUcM3JyWWuHMlLI5JJMTIh9A4qZ3WSn8eFg74q3pI02iFxaRor33tzc7zaGDh2Lso53eHtfOF9mFGnc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=posteo.de; spf=pass smtp.mailfrom=posteo.de; dkim=pass (2048-bit key) header.d=posteo.de header.i=@posteo.de header.b=PX0Z1sp0; arc=none smtp.client-ip=185.67.36.66 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=posteo.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=posteo.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=posteo.de header.i=@posteo.de header.b="PX0Z1sp0" Received: from submission (posteo.de [185.67.36.169]) by mout02.posteo.de (Postfix) with ESMTPS id 431CC240103 for ; Fri, 20 Mar 2026 22:08:17 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=posteo.de; s=2017; t=1774040897; bh=bOXHsWAp1TX0zN8K8H757WiBAvP7U7qBrrbxGi3Pp24=; h=Message-ID:Subject:From:To:Cc:Date:Autocrypt:Content-Type: MIME-Version:OpenPGP:From; b=PX0Z1sp0t6pX38KaTQ49UnsvJxfg0VQwnrCce046SBz06hkxbI9XvGx0TUKJnYwGC 6gAgjBy3IH310/CXMKV1Ps/yRHmr2MYEwBSwLQy5zdmrNt/5Z2ZJMeQz/VDYIs2Lzj 1h9vBzUu6qhZTXbg6CTZcLxTj2jMfT6aTVueBE17ESmZZYL7atxMHCN9Jxpdmt3D3+ cXq8MkMOYGKWR6kt45tg86fTr5P0StedTybxO0q/ce+tkK54+0mo2QJB6+iEuDeX7h Qp0NGu4xujF8eTB0p4Bzr+J1B1/3TIroKuffPwTY/jdthOcCPbqdFDDjq7bSInSkZp REi52bFkXkf8Q== Received: from customer (localhost [127.0.0.1]) by submission (posteo.de) with ESMTPSA id 4fcwC22z7dz9rxB; Fri, 20 Mar 2026 22:08:14 +0100 (CET) Message-ID: <6d9004bbfcce5158fc502a560ff14a0ce15d9a63.camel@posteo.de> Subject: Re: [PATCH v3 2/4] serdev: add rust private data to serdev_device From: Markus Probst To: Danilo Krummrich Cc: Greg Kroah-Hartman , Rob Herring , Jiri Slaby , Miguel Ojeda , Gary Guo , =?ISO-8859-1?Q?Bj=F6rn?= Roy Baron , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Kari Argillander , "Rafael J. Wysocki" , Viresh Kumar , Boqun Feng , David Airlie , Simona Vetter , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-pm@vger.kernel.org, driver-core@lists.linux.dev, dri-devel@lists.freedesktop.org Date: Fri, 20 Mar 2026 21:08:16 +0000 In-Reply-To: References: <20260313-rust_serdev-v3-0-c9a3af214f7f@posteo.de> <20260313-rust_serdev-v3-2-c9a3af214f7f@posteo.de> <2026031402-absence-graph-af5d@gregkh> <2026031422-shaded-matchbook-5078@gregkh> <2026031447-margarita-untamed-e976@gregkh> <9e07a53053d1dd75a4ebe94aaa06e2279ef3701d.camel@posteo.de> <2026032048-curtly-refold-e4df@gregkh> <4f4c09d683023df9daef89ca634b17b5c16625f7.camel@posteo.de> Autocrypt: addr=markus.probst@posteo.de; prefer-encrypt=mutual; keydata=mQINBGiDvXgBEADAXUceKafpl46S35UmDh2wRvvx+UfZbcTjeQOlSwKP7YVJ4JOZrVs93 qReNLkOWguIqPBxR9blQ4nyYrqSCV+MMw/3ifyXIm6Pw2YRUDg+WTEOjTixRCoWDgUj1nOsvJ9tVA m76Ww+/pAnepVRafMID0rqEfD9oGv1YrfpeFJhyE2zUw3SyyNLIKWD6QeLRhKQRbSnsXhGLFBXCqt 9k5JARhgQof9zvztcCVlT5KVvuyfC4H+HzeGmu9201BVyihJwKdcKPq+n/aY5FUVxNTgtI9f8wIbm fAjaoT1pjXSp+dszakA98fhONM98pOq723o/1ZGMZukyXFfsDGtA3BB79HoopHKujLGWAGskzClwT jRQxBqxh/U/lL1pc+0xPWikTNCmtziCOvv0KA0arDOMQlyFvImzX6oGVgE4ksKQYbMZ3Ikw6L1Rv1 J+FvN0aNwOKgL2ztBRYscUGcQvA0Zo1fGCAn/BLEJvQYShWKeKqjyncVGoXFsz2AcuFKe1pwETSsN 6OZncjy32e4ktgs07cWBfx0v62b8md36jau+B6RVnnodaA8++oXl3FRwiEW8XfXWIjy4umIv93tb8 8ekYsfOfWkTSewZYXGoqe4RtK80ulMHb/dh2FZQIFyRdN4HOmB4FYO5sEYFr9YjHLmDkrUgNodJCX CeMe4BO4iaxUQARAQABtCdNYXJrdXMgUHJvYnN0IDxtYXJrdXMucHJvYnN0QHBvc3Rlby5kZT6JAl QEEwEIAD4CGwMFCwkIBwICIgIGFQoJCAsCBBYCAwECHgcCF4AWIQSCdBjE9KxY53IwxHM0dh/4561 D0gUCaIZ9HQIZAQAKCRA0dh/4561D0pKmD/92zsCfbD+SrvBpNWtbit7J9wFBNr9qSFFm2n/65qen NNWKDrCzDsjRbALMHSO8nigMWzjofbVjj8Nf7SDcdapRjrMCnidS0DuW3pZBo6W0sZqV/fLx+AzgQ 7PAr6jtBbUoKW/GCGHLLtb6Hv+zjL17KGVO0DdQeoHEXMa48mJh8rS7VlUzVtpbxsWbb1wRZJTD88 ALDOLTWGqMbCTFDKFfGcqBLdUT13vx706Q29wrDiogmQhLGYKc6fQzpHhCLNhHTl8ZVLuKVY3wTT+ f9TzW1BDzFTAe3ZXsKhrzF+ud7vr6ff9p1Zl+Nujz94EDYHi/5Yrtp//+N/ZjDGDmqZOEA86/Gybu 6XE/v4S85ls0cAe37WTqsMCJjVRMP52r7Y1AuOONJDe3sIsDge++XFhwfGPbZwBnwd4gEVcdrKhnO ntuP9TvBMFWeTvtLqlWJUt7n8f/ELCcGoO5acai1iZ59GC81GLl2izObOLNjyv3G6hia/w50Mw9MU dAdZQ2MxM6k+x4L5XeysdcR/2AydVLtu2LGFOrKyEe0M9XmlE6OvziWXvVVwomvTN3LaNUmaINhr7 pHTFwDiZCSWKnwnvD2+jA1trKq1xKUQY1uGW9XgSj98pKyixHWoeEpydr+alSTB43c3m0351/9rYT TTi4KSk73wtapPKtaoIR3rOFHLQXbWFya3VzLnByb2JzdEBwb3N0ZW8uZGWJAlEEEwEIADsWIQSCd BjE9KxY53IwxHM0dh/4561D0gUCaIO9eAIbAwULCQgHAgIiAgYVCgkICwIEFgIDAQIeBwIXgAAKCR A0dh/4561D0oHZEACEmk5Ng9+OXoVxJJ+c9slBI2lYxyBO84qkWjoJ/0GpwoHk1IpyL+i+kF1Bb7y Hx9Tiz8ENYX7xIPTZzS8hXs1ksuo76FQUyD6onA/69xZIrYZ0NSA5HUo62qzzMSZL7od5e12R6OPR lR0PIuc4ecOGCEq3BLRPfZSYrL54tiase8HubXsvb6EBQ8jPI8ZUlr96ZqFEwrQZF/3ihyV6LILLk geExgwlTzo5Wv3piOXPTITBuzuFhBJqEnT25q2j8OumGQ+ri8oVeAzx24g1kc11pwpR0sowfa5MvZ WrrBcaIL7uJfR/ig7FyGnTQ1nS3btf3p0v8A3fc4eUu/K2No3l2huJp3+LHhCmpmeykOhSB63Mj3s 3Q87LD0HE0HBkTEMwp+sD97ZRpO67H5shzJRanUaDTb/mREfzpJmRT1uuec0X2zItL7a6itgMJvYI KG29aJLX3fTzzVzFGPgzVZYEdhu4y53p0qEGrrC1JtKR6DRPE1hb/OdWOkjmJ75+PPLD9U5IuRd6y sHJWsEBR1F0wkMPkEofWsvMYJzWXx/rvTWO8N4D6HigTgBXAXNgbc3IHpHlkvKoBJptv6DRVRtIrz 0G0cfBY0Sm7he4N2IYDWWdGnPBZ3rlLSdj5EiBU2YWgIgtLrb8ZNJ3ZlhYluGnBJDGRqy2jC9s1jY 66sLA9rQZMHhJTzMyIDwweGlvMzJAcG9zdGVvLmV1PokCbQQTAQgAVxYhBIJ0GMT0rFjncjDEczR2 H/jnrUPSBQJpa71VGxSAAAAAAAQADm1hbnUyLDIuNSsxLjExLDIsMgIbAwULCQgHAgIiAgYVCgkIC wIEFgIDAQIeBwIXgAAKCRA0dh/4561D0gKJD/9uOQKYlsDoQX65Gd0LiMT0C+5vXgr3VI0PHDOwcv 51fJ3A1vNyPZRFPGrz8+mDEXUQOF/INfnz5Tu1QHwf+iYcWcTGAN/FHgVR6ET6VBNU2hJaKhu+Ggo kjYyJTOvyX+3yNRUfSny0GjTjIPuPTErjqmHF+BtjXslpgwqnNMznf3lRIuUjRORupos6p3k1DndE 5vzUTmXSvMyXyOD2KhBl/kL76k0bHYyAQytZPag12pltrtFbA/r2phDGN2si8PooDT99bSTJjaM45 MTAAHbHKJfvgfK41bNFD5mMtpWpL195XRtS0Nrxdg3PaYBxN5gtTG0RyZfpYRlkdEhm+jj/8RxuSG i/qdhRdbiI7K2IELWeQVHSNDi9JabR/UzlR4NSnhfAjRIVlRM+eFbUl8XwxwVrAkojF5IraH2qRvg VCmuFsHUW07FUlrDrzpjXsD73cKppoFGDCdDR0BHJepXbFLS9+AqkT+guRJlnCTg2p+TQtnbwPgKp Vj98JixovCl99zRYTsL2bRNU5+q8iET65VMJ1ydyNanvLd5vI/NqDkXhlXLsGmdaDTtu4R21PkToX dQNGrZ91M9nlIBKw8Y7c7xZ4098qX2b8JX/CxD+gC1r4C8vuA3GkhFLx+KlkON7LyiJPkrePp6Qky jfGillcaQOqFZ3WwVqyzG1BUfTow== Content-Type: multipart/signed; micalg="pgp-sha256"; protocol="application/pgp-signature"; boundary="=-sp4lf+Wd/8VggGMFY3qC" Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 OpenPGP: url=https://posteo.de/keys/markus.probst@posteo.de.asc; preference=encrypt --=-sp4lf+Wd/8VggGMFY3qC Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Fri, 2026-03-20 at 20:59 +0100, Danilo Krummrich wrote: > On 3/20/26 6:13 PM, Markus Probst wrote: > > This is unique for a bus device. > >=20 > > A class device has its own Data (e. g. PwmOps), i. e. it will only be > > registered after this Data has been initialized by the driver. > >=20 > > The receive_buf callback on the serdev device on the other hand must > > happen on the drvdata, as there is no place to store its own Data. > >=20 > > The drvdata is only available at the end of the probe in Rust. >=20 > In other words, devm_serdev_device_open() relies on the driver having its > private data set before this is called, since once devm_serdev_device_ope= n() has > been called, the driver's receive_buf() callback may be called. >=20 > So, in C it is the driver's responsibility to do things in the correct or= der, in > Rust we want to make sure the driver can't do it out of order in the firs= t place. >=20 > I'm still not sure whether the current approach is the best option. For > instance, we could also solve this with a separate callback. >=20 > Wasn't this even > what you had in a previous version? Yes, but Kari pointed out that changing the ops while it is in use is unsafe [1]. Thanks - Markus Probst [1] https://lore.kernel.org/rust-for-linux/CAC=3DeVgR2WYdDTW3kOeemyQPP-H0aAUsrz= n5Gk5zCe2hQEB709w@mail.gmail.com/ --=-sp4lf+Wd/8VggGMFY3qC Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- iQJPBAABCAA5FiEEgnQYxPSsWOdyMMRzNHYf+OetQ9IFAmm9tzsbFIAAAAAABAAO bWFudTIsMi41KzEuMTEsMiwyAAoJEDR2H/jnrUPSq2EQAKirZFnVWlQ38HRT0Hri Co3bk89tdBXqZBKxN1NK9kUMFnOxDFAjA+PeK2YE+RzCPxFDvvASsLmp9ooZ7lJv IVUdDTxJrQ+j74dMk7mkuC/m0O/ZXMaEf3RVRScQCgeogpRBUjK24nTVNz8cCNS+ 485UOa9F5v3aIwkiWv7+XP2rF/8AH8NxaL5N1OngmxJ7K78GVgDvsXPM33u2DsBd XWkDqW+dhJtSGRHueTbqV+BZX7wI0SIGPuSCI+9+l/lX7Pr3jhPrWk6G1B/QExY7 GO7+uu7WH+Gkjfhckhj0+4oXC3wpVB8fFIDCqJxtArbkXeKmS5oH9z7VijESjaQn dVY+iX8wTODaP9x4nO9QaaqenYy7ofuJYEWRTbQRv06lUYlSKVWuwolr+/QXoCUl cDvu9kVDOnY7Vh3GDWsYwDPgsSGr+VaBMJIV+URuwX49XPC9BO31gmt3WQFP2Hul BHctukmiJLXPkXaNKlzl+SKD4GUyqJZcMBmOO7HZlaF+YXhP+18ENdX2wMm9l0Eu o9N+NUir/FPsChx0ktWcnpl4OCrtHLQqlQ4JfxGLK9zoSK5inCx8KGWqQanFlziT M15TwJ1gtH19R4kyeedwRTJORGHWIaeatWpBckpdXLfAyWVM+FtAEwnbKdNlxUbD /vp/9ilH+WH0BoOCSaQjYp0g =0B9T -----END PGP SIGNATURE----- --=-sp4lf+Wd/8VggGMFY3qC--