From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932361AbVKUTnx (ORCPT ); Mon, 21 Nov 2005 14:43:53 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932374AbVKUTnx (ORCPT ); Mon, 21 Nov 2005 14:43:53 -0500 Received: from palinux.external.hp.com ([192.25.206.14]:4557 "EHLO palinux.hppa") by vger.kernel.org with ESMTP id S932361AbVKUTnw (ORCPT ); Mon, 21 Nov 2005 14:43:52 -0500 Date: Mon, 21 Nov 2005 12:43:48 -0700 From: Matthew Wilcox To: Linus Torvalds Cc: David Howells , Andrew Morton , Ingo Molnar , linux-kernel@vger.kernel.org, Russell King , Ian Molton , Benjamin Herrenschmidt , Paul Mackerras Subject: Re: [PATCH 4/5] Centralise NO_IRQ definition Message-ID: <20051121194348.GH1598@parisc-linux.org> References: <24299.1132571556@warthog.cambridge.redhat.com> <20051121121454.GA1598@parisc-linux.org> <20051121190632.GG1598@parisc-linux.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 21, 2005 at 11:27:05AM -0800, Linus Torvalds wrote: > On Mon, 21 Nov 2005, Matthew Wilcox wrote: > > > > On Mon, Nov 21, 2005 at 10:55:24AM -0800, Linus Torvalds wrote: > > > Quite frankly, if we change [PCI_]NO_IRQ to -1, there's almost certainly > > > going to be a lot of drivers breaking. > > > > There's only one driver using NO_IRQ today (outside of architectures > > which define NO_IRQ to -1, that is). So *this* series of patches should > > break nothing. > > Right. But the point is that most drivers will do something like > > if (!dev->irq) > return; > > (whatever, made up). And that having NO_IRQ be anything but 0 is thus > fundamentally broken. The idea was to give them something better to use instead of this. Whether that be if (has_irq(dev)) return; or some other similar construct, I'm not terribly fussed. > I'm NOT talking about PCI specs. > > I'm talking about real hardware. > > Read pretty much _any_ data-sheet for an interrupt router, and you'll see > that the bit pattern 0000 means _disabled_. The only relevant thing I found with google was http://www.microsoft.com/whdc/archive/pciirq.mspx Where it talks about 0 meaning disabled, it says: Link Value for INTn#:A value of zero means this interrupt pin is not connected to any other interrupt pins and is not connected to any of the Interrupt Router's interrupt pins. which is a different bit from where it talks about the AT-compatible IRQ numbers. Everything else I find seems to be talking about Arcnet hardware (!)