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 27F4FC41535 for ; Wed, 12 Jan 2022 13:53:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353738AbiALNxC (ORCPT ); Wed, 12 Jan 2022 08:53:02 -0500 Received: from mga02.intel.com ([134.134.136.20]:32055 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238942AbiALNw7 (ORCPT ); Wed, 12 Jan 2022 08:52:59 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1641995579; x=1673531579; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=6o9aGlupJ5pLyORTimcn6DvGUzsV6iRYvEXQu/xlHjg=; b=nTwMvAxqsLGjEdnv1t3Ca6fu/Hq6lj112WXRizLYR4VoWx0+vkyZThTa b7lBc3MGDbUX0VW1wivv7gp1TcWtTQd13V9WsPo51aZYSLSMfIoFiIxan Oz6Nlo6b46aTQEG3CSrXU49Yqj0x3qEn5EJ67GitkMfqYiPTHvk49sjoX EpsKnq6y3tYveqbnnT91m0RD/BBqZS9bpj8X13DwcKtJ7waSZYvu4/Z+1 dyL2wAgJbDA3Bqsr+qhEZvsxy96WWR5MFyfij2sHjoNvRYCI2A0y2mAwC ZijHonAVaKuA2uPgMOjfIZQBp0m7sQCKbdJOPa59jC+r//7I/ycScWjpP w==; X-IronPort-AV: E=McAfee;i="6200,9189,10224"; a="231077537" X-IronPort-AV: E=Sophos;i="5.88,282,1635231600"; d="scan'208";a="231077537" Received: from orsmga006.jf.intel.com ([10.7.209.51]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Jan 2022 05:52:58 -0800 X-IronPort-AV: E=Sophos;i="5.88,282,1635231600"; d="scan'208";a="474911438" Received: from smile.fi.intel.com ([10.237.72.61]) by orsmga006-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Jan 2022 05:52:41 -0800 Received: from andy by smile.fi.intel.com with local (Exim 4.95) (envelope-from ) id 1n7e28-009hhk-Us; Wed, 12 Jan 2022 15:51:24 +0200 Date: Wed, 12 Jan 2022 15:51:24 +0200 From: Andy Shevchenko To: Andrew Lunn Cc: Geert Uytterhoeven , 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, 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: Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 12, 2022 at 02:38:37PM +0100, Andrew Lunn wrote: > > 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) No, what is suggested is to (besides the API changes): - do not treat ENXIO as something special in platform_get_irq*() - allow platform_get_irq*() to return other error codes > 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 -- With Best Regards, Andy Shevchenko