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 X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=BAYES_00,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A9BECC433B4 for ; Tue, 20 Apr 2021 09:08:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 76E4C6127C for ; Tue, 20 Apr 2021 09:08:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231245AbhDTJJO (ORCPT ); Tue, 20 Apr 2021 05:09:14 -0400 Received: from mail.kernel.org ([198.145.29.99]:53202 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230090AbhDTJJM (ORCPT ); Tue, 20 Apr 2021 05:09:12 -0400 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 90FB46101E; Tue, 20 Apr 2021 09:08:41 +0000 (UTC) Received: from 78.163-31-62.static.virginmediabusiness.co.uk ([62.31.163.78] helo=why.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94) (envelope-from ) id 1lYmN4-008SOC-LL; Tue, 20 Apr 2021 10:08:38 +0100 Date: Tue, 20 Apr 2021 10:08:38 +0100 Message-ID: <87eef5qq5l.wl-maz@kernel.org> From: Marc Zyngier To: Thomas Gleixner Cc: linux-kernel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH] genirq/irqaction: Move dev_id and percpu_dev_id in a union In-Reply-To: <87y2dfqhtd.ffs@nanos.tec.linutronix.de> References: <20210410120008.3034091-1-maz@kernel.org> <87y2dfqhtd.ffs@nanos.tec.linutronix.de> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 62.31.163.78 X-SA-Exim-Rcpt-To: tglx@linutronix.de, linux-kernel@vger.kernel.org, kernel-team@android.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 19 Apr 2021 00:44:14 +0100, Thomas Gleixner wrote: > > On Sat, Apr 10 2021 at 13:00, Marc Zyngier wrote: > > dev_id and percpu_dev_id are mutually exclusive in struct irqaction, > > as they conceptually represent the same thing, only in a per-cpu > > fashion. > > > > Move them into an anonymous union, saving a few bytes on the way. > > The reason why they are not in an anomymous union is that any misuse of > interfaces will result in an instantaneous explosion while with your > variant it will cause hard to diagnose side effects. > > I rather waste the extra 4/8 bytes unless there is a compelling reason > not to do so. Fair enough. I just happened to spot it while doing some vaguely related rework (turning the irqaction.irq field into an irqdesc). Happy to leave it as is. Thanks, M. -- Without deviation from the norm, progress is not possible.