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 A9883288C2F for ; Sun, 21 Dec 2025 16:28:13 +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=1766334496; cv=none; b=mMYYAX8az7P+oHfzgpcd68n00i856htMAigFaJbgH6i1Gyh5jPr3pdiNockFsf6Uv7qMFD/smuV4YJVl0PRHNNE9UA4EbXcGq3hhBIU6LmWsfCCF8w2kGmqwc1PhGDlUrKD71A99Fz8+jU+XbWEW0/OxTdPNvqCZIXN7J+ArakE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766334496; c=relaxed/simple; bh=jaxJJlMUxlb7zkwYnER72vo6g0NjPi9r0zxdT1k8B7w=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=nYuuYJWk/IsX99luza/9Yzb/8//0K84KM+HlkNU+NiGF4rfnBdKRRu+U/IhNDL89pniuDoK3lGBHgjTTdIbRa/XUnwBgZ5PcmiFzy5BKd8Pq8gpu4vmjvjDbWwTSoyWkz2XOfxkXz1+Yd0GOiubxIVHuzoXvtTl8MxjKSFrt+CA= 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=gUkOSVzG; 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="gUkOSVzG" Received: from submission (posteo.de [185.67.36.169]) by mout02.posteo.de (Postfix) with ESMTPS id C8A66240106 for ; Sun, 21 Dec 2025 17:28:11 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=posteo.de; s=2017; t=1766334491; bh=KSBZG3aCk3iKW2RACGge8JSEllNpFt79wXFY4DPunNc=; h=Message-ID:Subject:From:To:Cc:Date:Autocrypt:Content-Type: MIME-Version:OpenPGP:From; b=gUkOSVzGmWErs58XRXdmdWjZ+c4kmFf6SrNbJYV0R6IoQQJoQPusa4lkSMQXAbzTG ZHkXW0ZaUXxsLJ9fvEx6eAlih1LUSzlUhDO3AuxR1sF9kevyFELSM8DwOiYnYut930 JxKuk5H2ED/1SEzoU7JPzRr7voACPD+9xO2tj7qNNp4leQFb21F0i4J6R0mf0GxFXu NxtVsrEZRmQoXCOWiVai8hA1shuEG2FP3cId9pgiPvgDcFyoSW+MSS+16zhwU4FyfW UNwAlBLE0rmDQztjnHpSEBQLCrkQj1w12O94FRLs6xJECm8WrBfrY9e/ksrkh73bEg +1ez/yUHP9iFg== Received: from customer (localhost [127.0.0.1]) by submission (posteo.de) with ESMTPSA id 4dZ6By0bGRz9rwn; Sun, 21 Dec 2025 17:28:10 +0100 (CET) Message-ID: <4b55501e500edb8416ed690757f72752f1c49517.camel@posteo.de> Subject: Re: [PATCH RFC 1/4] serdev: Export internal is_serdev_device() for drivers From: Markus Probst To: Greg Kroah-Hartman Cc: Rob Herring , Jiri Slaby , Miguel Ojeda , Boqun Feng , Gary Guo , =?ISO-8859-1?Q?Bj=F6rn?= Roy Baron , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Danilo Krummrich , Kari Argillander , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org Date: Sun, 21 Dec 2025 16:28:11 +0000 In-Reply-To: <2025122138-saucy-unexpired-0b98@gregkh> References: <20251220-rust_serdev-v1-0-e44645767621@posteo.de> <20251220-rust_serdev-v1-1-e44645767621@posteo.de> <2025122138-saucy-unexpired-0b98@gregkh> 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 66sLA9g== Content-Type: multipart/signed; micalg="pgp-sha256"; protocol="application/pgp-signature"; boundary="=-8wUYIeHj/nRVOf9CAnMD" 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 --=-8wUYIeHj/nRVOf9CAnMD Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Sun, 2025-12-21 at 17:10 +0100, Greg Kroah-Hartman wrote: > On Sat, Dec 20, 2025 at 06:44:05PM +0000, Markus Probst wrote: > > From: Kari Argillander > >=20 > > The serdev core has an internal is_serdev_device() helper, but it was > > not accessible to drivers. Make it public by declaring it in serdev.h > > and exporting the symbol so that modular serdev drivers can rely on it > > instead of duplicating type checks. > >=20 > > This allows example future Rust serdev abstraction to have > >=20 > > TryFrom<&device::Device> for &serdev::Device >=20 > But why is that going to be needed? >=20 > > That way using bus is easy for other substystems. Also some other > > subsystems expose similar function: > >=20 > > - bool is_usb_device(const struct device *dev) > > - bool dev_is_pci(const struct device *dev) >=20 > Yes, and usually that's not a good idea, unless you have a bus with > multiple types of devices on it. I don't think serdev has that, does > it? >=20 > Only under special circumstances should this be required, so I'm curious > as to why you would ever have a pointer to a struct device and not > "know" that it is of this type? Who is passing that to you? For example, the pwm rust abstraction currently only provides a `device::Device` reference in callbacks [1]. If we want to write data to the serial device in one of the pwm callbacks, we need to convert the `device::Device` reference to `serdev::Device`. The TryFrom implementation provides a *safe* abstraction. At least in the pwm example, this could/should be circumvented with the `AsBusDevice` trait [2]. But this technically also applies to all other bus device abstractions and they also have a `TryFrom<&device::Device>` implementation, so with this it would be consistent across all rust bus device abstractions. Thanks - Markus Probst [1] https://rust.docs.kernel.org/kernel/pwm/trait.PwmOps.html [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/r= ust/kernel/device.rs?id=3De4addc7cc2dfcc19f1c8c8e47f3834b22cb21559 >=20 > thanks, >=20 > greg k-h --=-8wUYIeHj/nRVOf9CAnMD Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- iQJPBAABCAA5FiEEgnQYxPSsWOdyMMRzNHYf+OetQ9IFAmlIIBEbFIAAAAAABAAO bWFudTIsMi41KzEuMTEsMiwyAAoJEDR2H/jnrUPSs5MQAKVKI/dhoBIA0RVMM6nk 2hUgtZ4qeLm7mSwlNkaiAWwDvTXHuspbnmVtfMaZNTD6TfS0cnjlj4VMzOBgcIte KmfuuCEeRZHBlp6CfgohL65q/yo1yto0+/SwI3+HCl36VekOhlKxkaIAea39QFXA MICf/aT8CSVWXutsfocbO2vCj/+xEAymMeWUlO3au6hDdfMz6lAeA/ehzor9qhKg PXSiQAHysAol0Q+wBQKHHsImaHm9HWp+cgtZMlpiKLah+yUqbbEpvGbPI+baW9Ni FtUBveW5xC+cjkbSZohjWpUFX1dYNrPUiM6jYL+cB7cm5z7arfoQcB/hcu4UD39G Tn457ZaiYScZXH5FJAZDhrtymFewD4yGUydc1oWmtpCwVfK8DpD5eu7PVjJWqEAX mt2Sr3NvHEh5yD5n+s8ILn25DenO7C/RCpVHXN9+6GSnd3NOLey330+2L5jyrK/w eZlvTDHIzMzim/eOdGcB+MF0lJOK4gkEqxrDxCRNnhwRlpe/65gW4QQwQzIJwrkM dA6np/kFZxkPR3y+xdv9ysk999eZbOmidezd3NzmqqvPJnOI20Ca1macm6md0ciJ ZO1WSQjQcbUBVEfoEXnOyRVIiBew+DOd0Ye/jGVdHVANuNtbi2olhaKnbcFDbm2t 3iIJ8nkF5djbAPex8sYgN8/s =zmgk -----END PGP SIGNATURE----- --=-8wUYIeHj/nRVOf9CAnMD--