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 B5C2AC4167D for ; Wed, 12 Jan 2022 13:40:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353676AbiALNkT (ORCPT ); Wed, 12 Jan 2022 08:40:19 -0500 Received: from vps0.lunn.ch ([185.16.172.187]:34014 "EHLO vps0.lunn.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241154AbiALNkR (ORCPT ); Wed, 12 Jan 2022 08:40:17 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lunn.ch; s=20171124; h=In-Reply-To:Content-Disposition:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:From:Sender:Reply-To:Subject: Date:Message-ID:To:Cc:MIME-Version:Content-Type:Content-Transfer-Encoding: Content-ID:Content-Description:Content-Disposition:In-Reply-To:References; bh=S/pA7bUX6e4VB1GHe3hlypsDdeFRt4oGL0831NNCTJM=; b=REJii9uMw/mNDMEDkaB6nMl41t HVia+zgOKIfzuMj09o6jQ+IaM7PowDfcCzSXN02NEw/KiBFCm/WUr1uWHbYcv6vi03Q5vZQPWTCZw kZaHOnCDnZ4glu9pEOOBCeugcwmvyPmDFDeJp1Ck0ttEnrICihUcMQo96DS7dmh4ziSA=; Received: from andrew by vps0.lunn.ch with local (Exim 4.94.2) (envelope-from ) id 1n7dpl-001CDK-PQ; Wed, 12 Jan 2022 14:38:37 +0100 Date: Wed, 12 Jan 2022 14:38:37 +0100 From: Andrew Lunn To: Geert Uytterhoeven Cc: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= , Ulf Hansson , Vignesh Raghavendra , KVM list , "Rafael J. Wysocki" , linux-iio@vger.kernel.org, Linus Walleij , Amit Kucheria , ALSA Development Mailing List , Liam Girdwood , Guenter Roeck , Thierry Reding , MTD Maling List , Linux I2C , Miquel Raynal , linux-phy@lists.infradead.org, Jiri Slaby , "David S. Miller" , Khuong Dinh , Florian Fainelli , Matthias Schiffer , Joakim Zhang , Kamal Dasu , Lee Jones , Bartosz Golaszewski , Daniel Lezcano , Tony Luck , Kishon Vijay Abraham I , bcm-kernel-feedback-list , "open list:SERIAL DRIVERS" , Jakub Kicinski , Zhang Rui , Matthias Brugger , platform-driver-x86@vger.kernel.org, Linux PWM List , Robert Richter , Saravanan Sekar , Corey Minyard , Linux PM list , Mauro Carvalho Chehab , John Garry , Peter Korsgaard , William Breathitt Gray , Mark Gross , "open list:GPIO SUBSYSTEM" , Alex Williamson , Mark Brown , Borislav Petkov , Eric Auger , Takashi Iwai , Jaroslav Kysela , openipmi-developer@lists.sourceforge.net, Andy Shevchenko , Benson Leung , Pengutronix Kernel Team , Linux ARM , linux-edac@vger.kernel.org, Sergey Shtylyov , Richard Weinberger , Mun Yew Tham , Hans de Goede , Greg Kroah-Hartman , Yoshihiro Shimoda , Cornelia Huck , Linux MMC List , Linux Kernel Mailing List , linux-spi , Linux-Renesas , Vinod Koul , James Morse , Zha Qipeng , Sebastian Reichel , Niklas =?iso-8859-1?Q?S=F6derlund?= , linux-mediatek@lists.infradead.org, Brian Norris , netdev@vger.kernel.org Subject: Re: [PATCH 1/2] platform: make platform_get_irq_optional() optional Message-ID: References: <20220110195449.12448-1-s.shtylyov@omp.ru> <20220110195449.12448-2-s.shtylyov@omp.ru> <20220110201014.mtajyrfcfznfhyqm@pengutronix.de> <20220112085009.dbasceh3obfok5dc@pengutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > If an optional IRQ is not present, drivers either just ignore it (e.g. > for devices that can have multiple interrupts or a single muxed IRQ), > or they have to resort to polling. For the latter, fall-back handling > is needed elsewhere in the driver. > To me it sounds much more logical for the driver to check if an > optional irq is non-zero (available) or zero (not available), than to > sprinkle around checks for -ENXIO. In addition, you have to remember > that this one returns -ENXIO, while other APIs use -ENOENT or -ENOSYS > (or some other error code) to indicate absence. I thought not having > to care about the actual error code was the main reason behind the > introduction of the *_optional() APIs. The *_optional() functions return an error code if there has been a real error which should be reported up the call stack. This excludes whatever error code indicates the requested resource does not exist, which can be -ENODEV etc. If the device does not exist, a magic cookie is returned which appears to be a valid resources but in fact is not. So the users of these functions just need to check for an error code, and fail the probe if present. You seems to be suggesting in binary return value: non-zero (available) or zero (not available) This discards the error code when something goes wrong. That is useful information to have, so we should not be discarding it. IRQ don't currently have a magic cookie value. One option would be to add such a magic cookie to the subsystem. Otherwise, since 0 is invalid, return 0 to indicate the IRQ does not exist. The request for a script checking this then makes sense. However, i don't know how well coccinelle/sparse can track values across function calls. They probably can check for: ret = irq_get_optional() if (ret < 0) return ret; A missing if < 0 statement somewhere later is very likely to be an error. A comparison of <= 0 is also likely to be an error. A check for > 0 before calling any other IRQ functions would be good. I'm surprised such a check does not already existing in the IRQ API, but there are probably historical reasons for that. Andrew