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 2FA5CC433EF for ; Thu, 9 Dec 2021 20:21:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231862AbhLIUZZ (ORCPT ); Thu, 9 Dec 2021 15:25:25 -0500 Received: from mxout03.lancloud.ru ([45.84.86.113]:46874 "EHLO mxout03.lancloud.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229487AbhLIUZX (ORCPT ); Thu, 9 Dec 2021 15:25:23 -0500 Received: from LanCloud DKIM-Filter: OpenDKIM Filter v2.11.0 mxout03.lancloud.ru 243B5208EDA3 Received: from LanCloud Received: from LanCloud Received: from LanCloud Subject: Re: [PATCH] platform: finally disallow IRQ0 in platform_get_irq() and its ilk To: Andy Shevchenko CC: Greg Kroah-Hartman , "Rafael J. Wysocki" , References: <5e001ec1-d3f1-bcb8-7f30-a6301fd9930c@omp.ru> From: Sergey Shtylyov Organization: Open Mobile Platform Message-ID: <59f08001-7e1e-7fe2-28ba-045972bbae90@omp.ru> Date: Thu, 9 Dec 2021 23:21:41 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [192.168.11.198] X-ClientProxiedBy: LFEXT01.lancloud.ru (fd00:f066::141) To LFEX1907.lancloud.ru (fd00:f066::207) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/9/21 11:06 PM, Andy Shevchenko wrote: >> The commit a85a6c86c25b ("driver core: platform: Clarify that IRQ 0 is >> invalid") only calls WARN() when IRQ0 is about to be returned, however >> using IRQ0 is considered invalid (according to Linus) outside the arch/ >> code where it's used by the i8253 drivers. Many driver subsystems treat >> 0 specially (e.g. as an indication of the polling mode by libata), so >> the users of platform_get_irq[_byname]() in them would have to filter >> out IRQ0 explicitly and this (quite obviously) doesn't scale... >> Let's finally get this straight and return -EINVAL instead of IRQ0! > > You are changing the return value of platform_get_irq_optional(). > The problem here is the proposed change doesn't bring any value in such > case. platform_get_irq_optional() should be able (at the end of the day) > to return 3 types of values (as other APIs do): > > 0: success > == 0: IRQ not found > < 0: an error that must be consumed by the caller I remember that was in your patch that got reverted right after being merged. ;-) IMHO returning both error code and 0 on failure is a sign of a misdesigned API, it makes the failure check unnecessarily complex and error prone. > 0 is unexpected result for non-optional APIs and there you may try to play > tricks (like replacing it by error code). > > There was a discussion around the topic: > https://lore.kernel.org/lkml/20210331144526.19439-1-andriy.shevchenko@linux.intel.com/T/#u I don't see much of the discussion there... > Wanna help? No, I'm afraid you're on your own here... >> Fixes: a85a6c86c25b ("driver core: platform: Clarify that IRQ 0 is invalid") > > Not sure. Why? It fixes gthe IRQ0 problem, so that you don't have to check for IRQ0 in many callers (for the subsytems that treat 0 as s/th special, like polling mode)... If you have something to improve, you can do that atop of this patch... MBR, Sergey