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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FAKE_REPLY_C,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 AA11CC1975A for ; Tue, 17 Mar 2020 22:03:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7CD6020754 for ; Tue, 17 Mar 2020 22:03:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584482618; bh=NRUE2ckhs8n5Ozlq9QGah87GvPHMhCBA9ESXYy5Zdtg=; h=Date:From:To:Cc:Subject:In-Reply-To:List-ID:From; b=rF7w2l1/Vi1gfG4eXigAlC+ijZMSMYJ7bWGyJeUCfx79V4cEwcFSBxWAR9P16Ki/r zoZicypV6tXklEfy6XncyT9D9SxR1Gm5QDcBMUzByMTVTUJ+0hGUd6KcZ7m8XyAPZe xTb0Kh2iq2BWaovzeiRpWuZjx0VKHGmzID270gxg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726761AbgCQWDh (ORCPT ); Tue, 17 Mar 2020 18:03:37 -0400 Received: from mail.kernel.org ([198.145.29.99]:59504 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726476AbgCQWDh (ORCPT ); Tue, 17 Mar 2020 18:03:37 -0400 Received: from localhost (mobile-166-175-186-165.mycingular.net [166.175.186.165]) (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 7BC4B20714; Tue, 17 Mar 2020 22:03:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584482616; bh=NRUE2ckhs8n5Ozlq9QGah87GvPHMhCBA9ESXYy5Zdtg=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=1QGfUU91mkGNhqaAE5qkukrE5YGD0RThABDfnFSsg6yyPBnpZ/OoVSS8JJFuWo23r ThYXwUFPgcoopP7DR1QbWF1dlJInVWRqKWlMr64DZHN0CZJTsg5h3FzHB7jeKPHdn0 O36i7OCDqShLa3H4tFGVcqvDcEDogrn3BnfyYFBg= Date: Tue, 17 Mar 2020 17:03:34 -0500 From: Bjorn Helgaas To: Thomas Gleixner Cc: Marc Gonzalez , Aman Sharma , Lorenzo Pieralisi , Thomas Petazzoni , Andrew Murray , Linus Walleij , Ryder Lee , Karthikeyan Mitran , Hou Zhiqiang , Mans Rullgard , Matthias Brugger , linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org, Marc Zyngier Subject: Re: [PATCH 4/5] pci: handled return value of platform_get_irq correctly Message-ID: <20200317220334.GA230141@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200313215642.GA202015@google.com> User-Agent: Mutt/1.12.2 (2019-09-21) Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Fri, Mar 13, 2020 at 04:56:42PM -0500, Bjorn Helgaas wrote: > On Fri, Mar 13, 2020 at 10:05:58PM +0100, Thomas Gleixner wrote: > > Bjorn Helgaas writes: > > > On Thu, Mar 12, 2020 at 10:53:06AM +0100, Marc Gonzalez wrote: > > >> Last time around, my understanding was that, going forward, > > >> the best solution was: > > >> > > >> virq = platform_get_irq(...) > > >> if (virq <= 0) > > >> return virq ? : -ENODEV; > > >> > > >> i.e. map 0 to -ENODEV, pass other errors as-is, remove the dev_err > > >> > > >> @Bjorn/Lorenzo did you have a change of heart? > > > > > > Yes. In 10006651 (Oct 20, 2017), I thought: > > > > > > irq = platform_get_irq(pdev, 0); > > > if (irq <= 0) > > > return -ENODEV; > > > > > > was fine. In 11066455 (Aug 7, 2019), I said I thought I was wrong and > > > that: > > > > > > platform_get_irq() is a generic interface and we have to be able to > > > interpret return values consistently. The overwhelming consensus > > > among platform_get_irq() callers is to treat "irq < 0" as an error, > > > and I think we should follow suit. > > > ... > > > I think the best pattern is: > > > > > > irq = platform_get_irq(pdev, i); > > > if (irq < 0) > > > return irq; > > > > Careful. 0 is not a valid interrupt. > > Should callers of platform_get_irq() check for a 0 return value? > About 900 of them do not. > > Or should platform_get_irq() return a negative error instead of 0? > If 0 is not a valid interrupt, I think it would be easier to use the > interface if we made it so platform_get_irq() could never return 0, > which I think would also fit the interface documentation better: > > * Return: IRQ number on success, negative error number on failure. Trying again -- I'm not quite catching your meaning, Thomas. If platform_get_irq*() can return 0, but 0 is not a valid IRQ, I think it's sort of complicated to parse that return value. Drivers that require an IRQ would do this: irq = platform_get_irq(pdev, i); if (irq < 0) return irq; if (irq == 0) return -EINVAL; # error since driver requires IRQ return devm_request_irq(dev, irq, ...); Drivers that can either use an IRQ or do polling would do this: irq = platform_get_irq(pdev, i); if (irq <= 0) return setup_polling(); return devm_request_irq(dev, irq, ...); I think those are sort of ungainly, especially the first. If we made it so those functions never returned 0, drivers that need an IRQ could do this: irq = platform_get_irq(pdev, i); if (irq < 0) return irq; return devm_request_irq(dev, irq, ...); and drivers that support polling could do this: irq = platform_get_irq(pdev, i); if (irq < 0) return setup_polling(); return devm_request_irq(dev, irq, ...); That seems a lot easier to get correct, and it matches what most of the callers already do.