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=-5.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FAKE_REPLY_C,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 3FABAC10DCE for ; Thu, 12 Mar 2020 14:11:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 120A72071C for ; Thu, 12 Mar 2020 14:11:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584022266; bh=R/lnE+ckVywNCWcx1gHvO2Mh70J2f5SW32TxuQf+zGI=; h=Date:From:To:Cc:Subject:In-Reply-To:List-ID:From; b=QqhT/5J8WjgBHAs0DID7Z4Hd9Xa2gEE7RxTYIeGRlE7onvZ9dOXIIHO6wjeh56f3M I+qnRHzNj5xXuwM2Pi98a8oHYdBoTuiiXpGv0EZBuJhmhSZF5h/OrCH+Uh94fwhgQt 3cki6fyJRRhumyWA7qqljN6GFXCOMmVMj1XHiPE4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727431AbgCLOLF (ORCPT ); Thu, 12 Mar 2020 10:11:05 -0400 Received: from mail.kernel.org ([198.145.29.99]:47560 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727123AbgCLOLF (ORCPT ); Thu, 12 Mar 2020 10:11:05 -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 10BBE206E7; Thu, 12 Mar 2020 14:11:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584022264; bh=R/lnE+ckVywNCWcx1gHvO2Mh70J2f5SW32TxuQf+zGI=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=arv7/+jvUj9iJWfWlYdgqEG39OScPnVN8+yN/RSHbmQJwGazVMLlVu+Tctn3gdPTX FNdntEiwli27ScYUOBN6gfOPY6ZhjBhMcMl/D3RquqPL+Y8s6k9qxCCbZiR8x3ervB d5gWiTZ8T/wMs4bdrTy0xx25QCxA3drilWiFDdc0= Date: Thu, 12 Mar 2020 09:11:02 -0500 From: Bjorn Helgaas To: Marc Gonzalez Cc: 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: <20200312141102.GA93224@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6e413f63-06e3-9613-97dc-ff5968a4f759@free.fr> 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 [+cc another Marc] On Thu, Mar 12, 2020 at 10:53:06AM +0100, Marc Gonzalez wrote: > On 11/03/2020 20:19, Aman Sharma wrote: > > > diff --git a/drivers/pci/controller/pcie-tango.c b/drivers/pci/controller/pcie-tango.c > > index 21a208da3f59..18c2c4313eb5 100644 > > --- a/drivers/pci/controller/pcie-tango.c > > +++ b/drivers/pci/controller/pcie-tango.c > > @@ -273,9 +273,9 @@ static int tango_pcie_probe(struct platform_device *pdev) > > writel_relaxed(0, pcie->base + SMP8759_ENABLE + offset); > > > > virq = platform_get_irq(pdev, 1); > > - if (virq <= 0) { > > + if (virq < 0) { > > dev_err(dev, "Failed to map IRQ\n"); > > - return -ENXIO; > > + return virq; > > } > > > > irq_dom = irq_domain_create_linear(fwnode, MSI_MAX, &dom_ops, pcie); > > Weee, here we go again :-) > > https://patchwork.kernel.org/patch/11066455/ > https://patchwork.kernel.org/patch/10006651/ > > 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; I still think what I said in 2019 is the right approach. I do see your comment in 10006651 about this pattern: if (virq <= 0) return virq ? : -ENODEV; but IMHO it's too complicated for general use. Admittedly, it's not *very* complicated, but it's a relatively unusual C idiom and I stumble over it every time I see it. If 0 is a special case I think it should be mapped to a negative error in arch-specific code, which I think is what Linus T suggested in [1]. I think there's still a large consensus that "irq < 0" is the error case. In the tree today we have about 1400 callers of platform_get_irq() and platform_get_irq_byname() [2]. Of those, almost 900 check for "irq < 0" [3], while only about 150 check for "irq <= 0" [4] and about 15 use some variant of a "irq ? : -ENODEV" pattern. The bottom line is that in drivers/pci, I'd like to see either a single style or a compelling argument for why some checks should be "irq < 0" and others should be "irq <= 0". [1] https://yarchive.net/comp/linux/zero.html [2] $ git grep "=.*platform_get_irq" | wc -l 1422 [3] $ git grep -A4 "=.*platform_get_irq" | grep "<\s*0" | wc -l 894 [4] $ git grep -A4 "=.*platform_get_irq" | grep "<=\s*0" | wc -l 151 [5] $ git grep -A4 "=.*platform_get_irq" | grep "return.*?.*:.*;" | wc -l 15