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 6D16118AE2 for ; Mon, 1 Jun 2026 00:13:48 +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=1780272830; cv=none; b=mBgcEi54Kw881NJeV+U7jM6f5OqfpVMpQXjG2f2Yw0+2wjDicLQNlJdkrO/5uANjB9tkM/JAzQW9Tc56nKqJQR4n2Aa5dakgKgv7vJBoBnX/5EmNb/J3KGFXx4Kc6CsM2nA7NI1iPmxALYGCAJjuQ/SGNP35QsaBd3lqvIdPHmQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780272830; c=relaxed/simple; bh=58DM2kFGXRR5SmndG7V65q0M9IaBZ64o8CgjV+M6VW4=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=k+TbR9Fx2ejjLIovIehznp8gxM6IEaLRGHX5c1c1vVtdonzd5lgbv0Ku8X0ro62Vd95ygfqjl6cSEpP+yRLd5mF5XL7kHOMrDTE439guJ816Orq/GL9ORRS3EeQpERziW3RuCpV1JOHwPOTXaX5PaRsXgch4SttBQRhEH9q5aW8= 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=rGX3uobs; 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="rGX3uobs" Received: from submission (posteo.de [185.67.36.169]) by mout02.posteo.de (Postfix) with ESMTPS id AD5CA240101 for ; Mon, 1 Jun 2026 02:13:46 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=posteo.de; s=2017; t=1780272826; bh=58DM2kFGXRR5SmndG7V65q0M9IaBZ64o8CgjV+M6VW4=; h=Message-ID:Subject:From:To:Cc:Date:Autocrypt:Content-Type: MIME-Version:OpenPGP:From; b=rGX3uobsJNPgjuOz2UMw14IrjFLfcBVZ5BqPQqTYw7daSKrrOx4cNGsZfO/Ip7yjq VbNtvt4wXslom4Rw9FmdGt6xvXOhqAFtnxZk4YcPvoHBRGhm/r3d6V1MhyWtc+rGlO oDOblvKAlza/5J2vLNJxQ6CeV6XhPHuvH7jGG5PwqBWzO9ZixEb4zVC3RDiKJcxz9b j0+P1m2patrY2OtMmwLWo7YDMSXlrc3J/BtYRaI1fzBnNeqq3wZVIS/QbDyXFRHMp9 L7X2wAiIWGQV1nz4a99ORAF347NJCsF05d6BDdEyLU5N/3yc0doy3vtGMqk1LQtn8J 273iMW/a4l+SA== Received: from customer (localhost [127.0.0.1]) by submission (posteo.de) with ESMTPSA id 4gTDvq6Y2sz6trs; Mon, 1 Jun 2026 02:13:43 +0200 (CEST) Message-ID: Subject: Re: [PATCH v11 1/3] rust: add basic serial device bus abstractions From: Markus Probst To: Danilo Krummrich Cc: Markus Probst via B4 Relay , Rob Herring , Greg Kroah-Hartman , 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: Mon, 01 Jun 2026 00:13:45 +0000 In-Reply-To: References: <20260531-rust_serdev-v11-0-dee8e0d830f1@posteo.de> <20260531-rust_serdev-v11-1-dee8e0d830f1@posteo.de> <12fa6237168ecf6dc65ebf46118beeb5c51f3d1c.camel@posteo.de> <7c30276759aaba8127275e602cb78783ec33bbe9.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="=-bug7M99IW+HdQKCtqoS/" 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 --=-bug7M99IW+HdQKCtqoS/ Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Mon, 2026-06-01 at 00:32 +0200, Danilo Krummrich wrote: > On Mon Jun 1, 2026 at 12:00 AM CEST, Markus Probst wrote: > > On Sun, 2026-05-31 at 23:49 +0200, Danilo Krummrich wrote: > > > On Sun May 31, 2026 at 9:42 PM CEST, Markus Probst wrote: > > > > I just noticed, is it even possible to use SRCU here? Currently the= mutex not > > > > only ensures that no drvdata access happens after drvdata drop, but= also that > > > > the receive_buf waits for the probe to complete, as the drvdata has= n't been > > > > initialized yet. > > >=20 > > > Yeah, if you drop the completion, you need the mutex. > > Is the performance impact on an mutex or on srcu + completion higher? >=20 > Weighing in the completion, the mutex probably wins as it will always be > uncontested under normal operation. >=20 > > >=20 > > > (In case it wasn't discussed in previous versions already, there is a= lso the > > > option to just attach separate private data to the receive callback, = which would > > > avoid this synchonization problem in the first place. > > >=20 > > > You could have serdev::Device::open(), which takes its own priv= ate data > > > and a corresponding close(), this way you'd allow drivers to control = whether > > > they want the serial line "open" or not. You just need to make sure i= t is closed > > > eventually.) > > This would add complexity with types, as we need to ensure that write, > > set_baudrate, set_parity etc. does not run when closed. >=20 > Right, but looking at a few serdev drivers, there seem to be a few cases = where > drivers need to close and re-open. That is something we could consider once there is a user. I am certain it would make it more complex, not less. >=20 > > > That said, I don't know what turns out to be the better approach. And= maybe it > > > simply isn't something this initial series has to tackle? I think you= r driver > > > does not implement the receive callback? > > The initial driver with only leds: no. > >=20 > > That changes once the driver also takes care of hwmon (ADC sensor and > > fan failure) and input (power button and possibly other buttons). >=20 > Maybe drop it from this initial series then and revisit with the first us= er? I would prefer it with this series. Except for probe and remove there should be no overhead if receive_buf is not implemented. As it will be needed eventually and it is basic serdev functionality, I don't see a reason to not include it now. Thanks - Markus Probst --=-bug7M99IW+HdQKCtqoS/ Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- iQJPBAABCAA5FiEEgnQYxPSsWOdyMMRzNHYf+OetQ9IFAmoczq8bFIAAAAAABAAO bWFudTIsMi41KzEuMTIsMiwyAAoJEDR2H/jnrUPSZ+0P/2ylwrHvfHKKiTVBl/XF UL+HU/pmQkc3qwxSFyW3P7DLtY10V0r8kzPH2o35AC24avXePqjgo8hW2A5zAGqO u2gh9IV2XNBUKsF1CpV6bGaw/xCd3iUdmS8R8sIJfoNQJFj/EjDpL0SecHKz0iVd ARYzYY+xPCHLPGz8dxtGLgHq1pU4kIafkJ0K2+TYmSDVA9PRPlqhKgxDsWtFWVMb MnK6e+4HAqJaVNpITF7YmojKKIObqCmv8RnQWon6MaSQp1QK7F9b7Szyz1jN6435 iXMUcatC+McjLHNTvnRJgn0G50CNFX+/ETmnGHH6VVt/Mf4M+55B6HV9ziq72RD0 jnczWTHHTZwDgNjPgqQgRjeOOWHuKu4T9QKpJclOlcg6F3dmP7SYNTKX6iYYk1QQ 1cjwkUShY8HfcdcyWBf2ME3+D2fj73z/f59y/gFgIfKcMZGNuUHdbMTgGpUm9tcj GDgupxz7qS+CKzEBHzySTp9gKg6xzvA4gTcvzjoAk+3RrLhtFL/kFa8jvB5pvwlh CO1GwHsgiR6pPzqj4pAFI/JDF2/gcIMeOERTNAuAz1In8LpLCRzJuMFkmXXJ/XRy NYZyHMUT0PzUmfA1869YY2zN+FIRV0ykMAp0aKV4HhWm5qQpb3HYmGRMOhOJriVI sTK0zERHauHUMCm8i58Nnlf1 =TScp -----END PGP SIGNATURE----- --=-bug7M99IW+HdQKCtqoS/--