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 056E0C433EF for ; Thu, 2 Dec 2021 21:12:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1359783AbhLBVPY (ORCPT ); Thu, 2 Dec 2021 16:15:24 -0500 Received: from mxout02.lancloud.ru ([45.84.86.82]:49130 "EHLO mxout02.lancloud.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1358668AbhLBVPX (ORCPT ); Thu, 2 Dec 2021 16:15:23 -0500 Received: from LanCloud DKIM-Filter: OpenDKIM Filter v2.11.0 mxout02.lancloud.ru AA6AA207D577 Received: from LanCloud Received: from LanCloud Received: from LanCloud Subject: Re: [PATCH] platform: finally disallow IRQ0 in platform_get_irq() and its ilk To: Greg Kroah-Hartman CC: "Rafael J. Wysocki" , References: <5e001ec1-d3f1-bcb8-7f30-a6301fd9930c@omp.ru> From: Sergey Shtylyov Organization: Open Mobile Platform Message-ID: Date: Fri, 3 Dec 2021 00:11:57 +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 Hello! On 11/26/21 7:20 PM, Greg Kroah-Hartman 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! >> >> Fixes: a85a6c86c25b ("driver core: platform: Clarify that IRQ 0 is invalid") >> Signed-off-by: Sergey Shtylyov >> >> --- >> The patch is against the 'driver-core-linus' branch of Greg Kroah-Hartman's >> 'driver-core.git' repo. >> >> drivers/base/platform.c | 6 ++++-- >> 1 file changed, 4 insertions(+), 2 deletions(-) >> >> Index: driver-core/drivers/base/platform.c >> =================================================================== >> --- driver-core.orig/drivers/base/platform.c >> +++ driver-core/drivers/base/platform.c >> @@ -231,7 +231,8 @@ int platform_get_irq_optional(struct pla >> out_not_found: >> ret = -ENXIO; >> out: >> - WARN(ret == 0, "0 is an invalid IRQ number\n"); >> + if (WARN(!ret, "0 is an invalid IRQ number\n")) >> + return -EINVAL; > > You need to get approval from the interrrupt developers for this type of > change, as it is a change and might break existing platforms, right? Well, that's always possible... :-) I do remember we had issues with the serial driver on the Alchemy MIPS SoCs back in the 2.6.1x time frame: UART0 used IRQ0 there and the serial driver treated 0 as an indication of the polling mode, IIRC... Now Alchemies have the SoC IRQ0 mapped to the Linux IRQ8, so this is not a problem anymore (the 1st 8 IRQs are mapped to the MIPS CPU IRQs and IRQ0 isn't even used)... > thanks, > > greg k-h MBR, Sergey