From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from alsa0.perex.cz (alsa0.perex.cz [77.48.224.243]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id CE3BFC4332F for ; Sat, 26 Nov 2022 08:09:06 +0000 (UTC) Received: from alsa1.perex.cz (alsa1.perex.cz [207.180.221.201]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by alsa0.perex.cz (Postfix) with ESMTPS id E27D51863; Sat, 26 Nov 2022 09:08:14 +0100 (CET) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa0.perex.cz E27D51863 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=alsa-project.org; s=default; t=1669450145; bh=W5pjJZCX51+xzRA1zXxpo0Z4g8I2gr5TYetrOYDBeQg=; h=Date:From:To:Subject:References:In-Reply-To:Cc:List-Id: List-Unsubscribe:List-Archive:List-Post:List-Help:List-Subscribe: From; b=Y6CdrPFyXrZADc76Y/9BlSx75ncIf/DDMOq1oforS1nceljkcnTg54TqCzk8twO3t ZgEgNkdlfhzKJdgszRTmalC4aRhxfcaJsMretfzn/WqEAQSyON330vavAWzdOJdDnl tYPtt8zVXEc3lMgyDlRJtd5USvGrHaKc7Pjwkdrw= Received: from alsa1.perex.cz (localhost.localdomain [127.0.0.1]) by alsa1.perex.cz (Postfix) with ESMTP id BB0FCF80621; Sat, 26 Nov 2022 08:59:16 +0100 (CET) Received: by alsa1.perex.cz (Postfix, from userid 50401) id 0F3CAF800BB; Wed, 23 Nov 2022 15:53:51 +0100 (CET) Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by alsa1.perex.cz (Postfix) with ESMTPS id 08178F800BB for ; Wed, 23 Nov 2022 15:53:47 +0100 (CET) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa1.perex.cz 08178F800BB Authentication-Results: alsa1.perex.cz; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="caDYBku0" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=d34IWNksyN/fUaMdJSyNyFr5/NYJSUamcGjA6pAMtuA=; b=caDYBku0DlKozdr16VvQx2Pf47 2FemMLhC3IcrPQOUzURzAZnbhstHNQck3oc9tp/PXObEiBO1MfrwTzqTVM4sWneDrW/0ivZt02rfR GJ97qbtKp6invRyg7JlLsZYl3ZG3vWExlD7hzk57S+mKdQTrPuVtfzCSbDoVVJ8FxhHKtoRSJ0jtU XYB3KakhM7UNmV0lB+Oflj6FYMkeTc2cxN2tMw87mvmQsXCHH2Ve1EXgve0TduL0q7RtvwUTii1c5 R8WonwObHfVSic7ZLMDFLvXv3RjVaPGgy5xWCwSrWbCPm+c1AWWTPP+4n4zTi5sjodPbwnBYZMh7x 2Km029GQ==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1oxr7T-007j3f-RC; Wed, 23 Nov 2022 14:53:00 +0000 Date: Wed, 23 Nov 2022 14:52:59 +0000 From: Matthew Wilcox To: Maximilian Luz Subject: Re: [PATCH 3/5] driver core: make struct device_type.uevent() take a const * Message-ID: References: <20221123122523.1332370-1-gregkh@linuxfoundation.org> <20221123122523.1332370-3-gregkh@linuxfoundation.org> <711d5275-7e80-c00d-0cdc-0f3d52175361@gmail.com> <97be39ed-3cea-d55a-caa6-c2652baef399@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <97be39ed-3cea-d55a-caa6-c2652baef399@gmail.com> X-Mailman-Approved-At: Sat, 26 Nov 2022 08:58:52 +0100 Cc: Alexandre Belloni , Heikki Krogerus , Sean Young , "Rafael J. Wysocki" , alsa-devel@alsa-project.org, platform-driver-x86@vger.kernel.org, linux-i2c@vger.kernel.org, Andreas Noever , linux-i3c@lists.infradead.org, linux1394-devel@lists.sourceforge.net, Bard Liao , Dan Williams , Andy Shevchenko , linux-acpi@vger.kernel.org, Frank Rowand , Pierre-Louis Bossart , Jason Gunthorpe , Alan Stern , linux-serial@vger.kernel.org, linux-input@vger.kernel.org, Won Chung , Len Brown , devicetree@vger.kernel.org, Chaitanya Kulkarni , Ira Weiny , Michael Jamet , Ming Lei , Mark Gross , Hans de Goede , Rob Herring , Jiri Slaby , Thomas Gleixner , Mauro Carvalho Chehab , Mika Westerberg , Jens Axboe , linux-block@vger.kernel.org, Jilin Yuan , "Martin K. Petersen" , Greg Kroah-Hartman , Dmitry Torokhov , linux-kernel@vger.kernel.org, Wolfram Sang , Vinod Koul , Stefan Richter , Sakari Ailus , Yehezkel Bernat , Sanyog Kale , linux-media@vger.kernel.org, linux-usb@vger.kernel.org X-BeenThere: alsa-devel@alsa-project.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: "Alsa-devel mailing list for ALSA developers - http://www.alsa-project.org" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: "Alsa-devel" On Wed, Nov 23, 2022 at 02:59:00PM +0100, Maximilian Luz wrote: > On 11/23/22 14:34, Andy Shevchenko wrote: > > On Wed, Nov 23, 2022 at 02:14:31PM +0100, Maximilian Luz wrote: > > > On 11/23/22 13:25, Greg Kroah-Hartman wrote: > > > > The uevent() callback in struct device_type should not be modifying the > > > > device that is passed into it, so mark it as a const * and propagate the > > > > function signature changes out into all relevant subsystems that use > > > > this callback. > > > > [...] > > > > > > -static inline struct ssam_device *to_ssam_device(struct device *d) > > > > +static inline struct ssam_device *to_ssam_device(const struct device *d) > > > > { > > > > return container_of(d, struct ssam_device, dev); > > > > } > > > > > > I am slightly conflicted about this change as that now more or less > > > implicitly drops the const. So I'm wondering if it wouldn't be better to > > > either create a function specifically for const pointers or to just > > > open-code it in the instance above. > > > > > > I guess we could also convert this to a macro. Then at least there > > > wouldn't be an explicit and potentially misleading const-conversion > > > indicated in the function signature. > > > > This is an intermediate step as far as I know since moving container_of to > > recognize const is a bit noisy right now. I guess you can find a discussion > > on the topic between Greg and Sakari. > > Thanks! I assume you are referring to the following? > > https://lore.kernel.org/lkml/4218173bd72b4f1899d4c41a8e251f0d@AcuMS.aculab.com/T/ > > As far as I can tell this is only a warning in documentation, not > compile time (which would probably be impossible?). > > As I've said I'd be fine with converting the function to a macro (and > preferably adding a similar warning like the one proposed in that > thread). The point that irks me up is just that, as proposed, the > function signature would now advertise a conversion that should never be > happening. > > Having two separate functions would create a compile-time guarantee, so > I'd prefer that, but I can understand if that might be considered too > noisy in code. Or if there is a push to make container_of() emit a > compile-time warning I'd also be perfectly happy with converting it to a > macro now as that'd alleviate the need for functions in the future. Can't we do: static inline const struct ssam_device *to_ssam_device(const struct device *d) { return container_of(d, const struct ssam_device, dev); }