From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752338AbbIQVNv (ORCPT ); Thu, 17 Sep 2015 17:13:51 -0400 Received: from pandora.arm.linux.org.uk ([78.32.30.218]:56194 "EHLO pandora.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751906AbbIQVNu (ORCPT ); Thu, 17 Sep 2015 17:13:50 -0400 Date: Thu, 17 Sep 2015 22:13:31 +0100 From: Russell King - ARM Linux To: Daniel Lezcano Cc: Thomas Gleixner , Caesar Wang , Heiko Stuebner , Catalin Marinas , Will Deacon , linux-kernel@vger.kernel.org, linux-rockchip@lists.infradead.org, linux-arm-kernel@lists.infradead.org, Caesar Wang Subject: Re: [PATCH 1/3] clocksource: rockchip: Make the driver more readability and compatible Message-ID: <20150917211331.GU21084@n2100.arm.linux.org.uk> References: <1442476272-31723-1-git-send-email-wxt@rock-chips.com> <1442476272-31723-2-git-send-email-wxt@rock-chips.com> <55FA83D5.9010504@linaro.org> <55FA87AA.4040807@gmail.com> <55FA9099.7000903@linaro.org> <55FA9CB1.8010402@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <55FA9CB1.8010402@linaro.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 17, 2015 at 12:57:53PM +0200, Daniel Lezcano wrote: > Hi Thomas, > > there is one thing I don't understand. > > If the IRQ0 is invalid, irq_of_parse_and_map returning zero means an error > and from what you said it is ok. > > But I see the NO_IRQ on ARM is (-1) and the drivers are checking with NO_IRQ > the return code of irq_of_parse_and_map. So if there is an error, that won't > be detected. NO_IRQ being -1 is a legacy thing for ARM - all ARM drivers are supposed to be converted to use <= 0 or == 0 to detect invalid IRQs, and _eventually_ once all users are gone, NO_IRQ deleted. Moreover, there are supposed to be no _new_ users of NO_IRQ ever added to the kernel. Modern drivers should _all_ be using !irq to detect invalid IRQs, and not using NO_IRQ. The steps here are: 1. Convert all ARM platforms to start numbering IRQs from 1 rather than 0. 2. Convert all drivers used on ARM to detect lack of IRQ by checking for <= 0. 3. Replace NO_IRQ assignments with zero-initialisations. 4. Remove NO_IRQ. The reason it hasn't happened is that it requires effort and testing, and rather than running around getting old platforms to boot (which includes remembering _how_ to get them to boot) with recent kernels, I prefer to spend my time doing more productive work with modern code. -- FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.