From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759006AbXKGOx7 (ORCPT ); Wed, 7 Nov 2007 09:53:59 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757987AbXKGOxv (ORCPT ); Wed, 7 Nov 2007 09:53:51 -0500 Received: from pip9.gyao.ne.jp ([61.122.117.247]:58212 "EHLO mx.gate01.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1757568AbXKGOxu (ORCPT ); Wed, 7 Nov 2007 09:53:50 -0500 Date: Wed, 7 Nov 2007 23:53:26 +0900 From: Paul Mundt To: Mark Lord Cc: Alan Cox , Jeff Garzik , Andrew Morton , linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org, linuxsh-dev@lists.sourceforge.net Subject: Re: [PATCH 1/2] libata: Support PIO polling-only hosts. Message-ID: <20071107145326.GA27752@linux-sh.org> Mail-Followup-To: Paul Mundt , Mark Lord , Alan Cox , Jeff Garzik , Andrew Morton , linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org, linuxsh-dev@lists.sourceforge.net References: <20071107081052.GA25913@linux-sh.org> <20071107130940.16b5ea86@the-village.bc.nu> <20071107132702.GA27488@linux-sh.org> <4731C71A.4000406@rtr.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4731C71A.4000406@rtr.ca> User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 07, 2007 at 09:09:30AM -0500, Mark Lord wrote: > Paul Mundt wrote: > >On Wed, Nov 07, 2007 at 01:09:40PM +0000, Alan Cox wrote: > >>On Wed, 7 Nov 2007 17:10:52 +0900 > >>Paul Mundt wrote: > >>>By default ata_host_activate() expects a valid IRQ in order to > >>>successfully register the host. This patch enables a special case > >>>for registering polling-only hosts that either don't have IRQs > >>>or have buggy IRQ generation (either in terms of handling or > >>>sensing), which otherwise work fine. > >>> > >>>Hosts that want to use polling mode can simply set ATA_FLAG_PIO_POLLING > >>>and pass in a NULL IRQ handler or invalid (< 0) IRQ. > >>NAK > >> > >>Zero is "no IRQ", please use that for polling not "< 0" > >> > >However, platform_get_irq() will happily return IRQ#0, and it's a valid > >vector on plenty of machines. NO_IRQ is also < 0 on at least FR-V, ARM, > >blackin, PA-RISC, some PowerPC, and even IDE. > > Too bad. The Penultimate Penguin wants zero to continue to mean "no IRQ". > > Dig into the archives for multiple threads on this exact topic. > The end result is that "0" means "no IRQ". If your physical IRQ actually > is the number 0, then reencode it to some other value for this purpose. > I've read the threads, but this does little to do with the fact it's still a perfectly valid vector, and I'm not about to force every IRQ vector on my platform off-by-1 in order to satisfy a religious point of view with zero reflection on what the hardware actually looks like. So I'll change the check to IRQ#0 == invalid, but if that's to be enforced kernel-wide, then all of the existing NO_IRQ cases should be ripped out and set to 0. This way at least people are getting screwed consistently, rather than just in particular subsystems. > Yes, a bit of pain, but that's how many parts of the kernel expect it, Just as many parts of the kernel make no such assumption. > and in the end it's no more overall hassle than doing it differently might > have been. > Spoken like someone who doesn't have to contend with off-by-1 IRQ vectors as a result of an entirely cosmetic change. It's certainly easier to parrot a party line when you aren't being bitten by it. So again, I'll make the change, but it's utter nonsense.