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 1E526ECAAA1 for ; Mon, 24 Oct 2022 09:47:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229679AbiJXJrA convert rfc822-to-8bit (ORCPT ); Mon, 24 Oct 2022 05:47:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53652 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230015AbiJXJqr (ORCPT ); Mon, 24 Oct 2022 05:46:47 -0400 Received: from eu-smtp-delivery-151.mimecast.com (eu-smtp-delivery-151.mimecast.com [185.58.85.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E23A22B603 for ; Mon, 24 Oct 2022 02:46:45 -0700 (PDT) Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id uk-mta-120-uHmcMPlPMjafKyj3wsslNg-1; Mon, 24 Oct 2022 10:46:42 +0100 X-MC-Unique: uHmcMPlPMjafKyj3wsslNg-1 Received: from AcuMS.Aculab.com (10.202.163.6) by AcuMS.aculab.com (10.202.163.6) with Microsoft SMTP Server (TLS) id 15.0.1497.42; Mon, 24 Oct 2022 10:46:40 +0100 Received: from AcuMS.Aculab.com ([::1]) by AcuMS.aculab.com ([::1]) with mapi id 15.00.1497.042; Mon, 24 Oct 2022 10:46:40 +0100 From: David Laight To: 'Andy Shevchenko' CC: Sakari Ailus , Greg Kroah-Hartman , "linux-kernel@vger.kernel.org" , "Rafael J. Wysocki" Subject: RE: [PATCH 1/1] linux/container_of.h: Warn about loss of constness Thread-Topic: [PATCH 1/1] linux/container_of.h: Warn about loss of constness Thread-Index: AQHY54ozH4qdMwC1Yk+S6+0KOnujn64dR6XQ///w5gCAABLzkA== Date: Mon, 24 Oct 2022 09:46:40 +0000 Message-ID: <57360b976d5944babe1e85fc51b3f6f6@AcuMS.aculab.com> References: <20221024082610.74990-1-sakari.ailus@linux.intel.com> In-Reply-To: Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: 'Andy Shevchenko' > Sent: 24 October 2022 10:37 > ... > > > > > > Wait, no one uses this macro, so why not just remove it entirely? > > > > > > > > Good question. It appears to be a (relatively) common pattern to look up > > > > something and the return its containing object if the lookup was > > > > successful. Doing a quick > > > > > > > > $ git grep 'container_of.*:' drivers include > > > > > > > > reveals more than 20 instances of the pattern. There are probably more > > > > those that use if for testing for NULL. I guess people don't know about > > > > this macro, apart from the developers of the staging driver it was added > > > > for (commit 05e6557b8ed833546ee2b66ce6b58fecf09f439e). > > > > > > Maybe we can provide an example to keep this macro in the kernel, meaning > > > convert one of the drivers / subsystem to actually use it? > > > > Adding _safe() to a function name doesn't actually tell you anything. > > You still need to look up what it is 'safe' against. > > > > In this case the full code pattern is actually much clearer. > > > > It is also quite likely that it is followed by an: > > if (!ptr) > > return xxx; > > You that can/should really be put before the container_of() call. > > return statements in macros are no go. Or you meant something else? I meant in the function itself. It might be interesting to check how many of the function can actually have a NULL pointer? Especially in staging code might be being 'defensive'. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)