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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 352AFC47088 for ; Wed, 23 Nov 2022 14:04:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238476AbiKWOD7 (ORCPT ); Wed, 23 Nov 2022 09:03:59 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57088 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238402AbiKWODl (ORCPT ); Wed, 23 Nov 2022 09:03:41 -0500 Received: from mail-ej1-x630.google.com (mail-ej1-x630.google.com [IPv6:2a00:1450:4864:20::630]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 23FAC7658; Wed, 23 Nov 2022 05:59:06 -0800 (PST) Received: by mail-ej1-x630.google.com with SMTP id f18so42997141ejz.5; Wed, 23 Nov 2022 05:59:06 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=AJ96Qo939E/LqBCZfcidWQRpLbhFZIXN8NEAiTpAhxk=; b=iZRqD+AZI8YXmWPNNo+Fwqqrxkdxxp8sdDhXpzQpS+Z7O6ViZRfqwWBRa1+q6Fn++z AayBKunxqdaXyMJwtJZy3prCnDCGQ0bf8s3sNL8v8cU+NRhqFpeFsIofjTg60S/cPv71 H+sPHuj9u82mvhCqWAi/DQC3hw1wr9h8SadxlGtO1i2opKK+8L4eXSIBcFr67zvlz0zl CppQAaJx+cMEavlnguot+la0zcqSDuv3T+S6/PQUa7xI6LA3gJLCSh2MX8CVHkwmdm4o 1ueE/AeHSGD8djbrX3VA431+kO+OYoaPdqwS1MoX0XoMPIRKU2d/L5Kyjwtu65MvGCmS m0iA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=AJ96Qo939E/LqBCZfcidWQRpLbhFZIXN8NEAiTpAhxk=; b=N/g480wtD8DkRSvzjFK0982z5jF2d5bt6Z1mRY2gUT8oWuFBrWpXcTDoTGEPC1oVjY HmgB7FZUep8UNto1dQarttCT5e3x/XLxsACdFjekiqBJLgQa5Aw7Tk6tO3E9FkGwA5ON ALcL2RLr1kNdIuXQyYgriWXLBCa6cFr4zmC/W5v5grjhxxpy2VeztCJkn6jUdMJzHS2M ZBMuVcPqSbispu9NW8zw5xFgVDF+YIR2cpycjrTInTGEAI0B7U4HWbOtVSiJRU84vp43 fy8C2FRHALL5moTG7La08EDJ5ioCnI51rHhzn5kVAn5ZhAEcciSfpraZ5ee5a63WXSVG v5Cg== X-Gm-Message-State: ANoB5pnP/M70V7HMqNOn81cSXBk/Q/kxqbX6LGjBSOfq10OY/urW1f+G X13+ETVLkpWNCdJ4HXMB4YA= X-Google-Smtp-Source: AA0mqf4zngmNYriYQQf6WQDa/SSuXsv/0hsexE8WPkPKL+mwy2wneQC+ycXRX8UErwxgAKGb3ytkyA== X-Received: by 2002:a17:906:c30c:b0:7ba:1f48:ccec with SMTP id s12-20020a170906c30c00b007ba1f48ccecmr1909635ejz.105.1669211944571; Wed, 23 Nov 2022 05:59:04 -0800 (PST) Received: from [10.20.0.7] ([37.120.217.162]) by smtp.gmail.com with ESMTPSA id d12-20020a056402078c00b0045b3853c4b7sm7741854edy.51.2022.11.23.05.59.01 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 23 Nov 2022 05:59:04 -0800 (PST) Message-ID: <97be39ed-3cea-d55a-caa6-c2652baef399@gmail.com> Date: Wed, 23 Nov 2022 14:59:00 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.5.0 Subject: Re: [PATCH 3/5] driver core: make struct device_type.uevent() take a const * Content-Language: en-US To: Andy Shevchenko Cc: Greg Kroah-Hartman , linux-kernel@vger.kernel.org, Jens Axboe , "Rafael J. Wysocki" , Len Brown , Stefan Richter , Wolfram Sang , Alexandre Belloni , Dmitry Torokhov , Sean Young , Mauro Carvalho Chehab , Rob Herring , Frank Rowand , Hans de Goede , Mark Gross , Vinod Koul , Bard Liao , Pierre-Louis Bossart , Sanyog Kale , Andreas Noever , Michael Jamet , Mika Westerberg , Yehezkel Bernat , Jiri Slaby , Heikki Krogerus , "Matthew Wilcox (Oracle)" , "Martin K. Petersen" , Chaitanya Kulkarni , Ming Lei , Jilin Yuan , Alan Stern , Sakari Ailus , Jason Gunthorpe , Thomas Gleixner , Ira Weiny , Dan Williams , Won Chung , alsa-devel@alsa-project.org, devicetree@vger.kernel.org, linux-acpi@vger.kernel.org, linux-block@vger.kernel.org, linux-i2c@vger.kernel.org, linux-i3c@lists.infradead.org, linux-input@vger.kernel.org, linux-media@vger.kernel.org, linux-serial@vger.kernel.org, linux-usb@vger.kernel.org, linux1394-devel@lists.sourceforge.net, platform-driver-x86@vger.kernel.org References: <20221123122523.1332370-1-gregkh@linuxfoundation.org> <20221123122523.1332370-3-gregkh@linuxfoundation.org> <711d5275-7e80-c00d-0cdc-0f3d52175361@gmail.com> From: Maximilian Luz In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org 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. Regards, Max