From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750913AbVKUVfn (ORCPT ); Mon, 21 Nov 2005 16:35:43 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750921AbVKUVfm (ORCPT ); Mon, 21 Nov 2005 16:35:42 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:40127 "EHLO mx3.mail.elte.hu") by vger.kernel.org with ESMTP id S1750741AbVKUVf3 (ORCPT ); Mon, 21 Nov 2005 16:35:29 -0500 Date: Mon, 21 Nov 2005 22:35:27 +0100 From: Ingo Molnar To: Paul Mackerras Cc: Linus Torvalds , Matthew Wilcox , David Howells , Andrew Morton , linux-kernel@vger.kernel.org, Russell King , Ian Molton , Benjamin Herrenschmidt Subject: Re: [PATCH 4/5] Centralise NO_IRQ definition Message-ID: <20051121213527.GA6452@elte.hu> References: <24299.1132571556@warthog.cambridge.redhat.com> <20051121121454.GA1598@parisc-linux.org> <20051121190632.GG1598@parisc-linux.org> <20051121194348.GH1598@parisc-linux.org> <20051121211544.GA4924@elte.hu> <17282.15177.804471.298409@cargo.ozlabs.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <17282.15177.804471.298409@cargo.ozlabs.ibm.com> User-Agent: Mutt/1.4.2.1i X-ELTE-SpamScore: 0.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=0.0 required=5.9 tests=AWL autolearn=disabled SpamAssassin version=3.0.3 0.0 AWL AWL: From: address is in the auto white-list X-ELTE-VirusStatus: clean Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Paul Mackerras wrote: > Ingo Molnar writes: > > > is there any architecture where irq 0 is a legitimate setting that could > > occur in drivers, and which would make NO_IRQ define of 0 non-practical? > > Yes, G5 powermacs have the SATA controller on irq 0. So if we can't > use irq 0, I can't get to my hard disk. :) Other powermacs also use > irq 0 for various things, as do embedded PPC machines. oh well [*]. Then it's gotta be the !dev->irq.valid thing i guess. OTOH that has some disadvantages too: any normal access to dev->irq.nr will mean implicit 0xffffffff (or 0xffffffffffffffff) masking generated by the compiler. Also, unless there's some compiler trick, tons of drivers will be affected - because dev->irq isnt valid anymore. A quick grep suggests 5381 lines of code affected, spread out in 917 files. Quite impractical. So we are back to square one and Matthew's patch(es). Ingo [*] is there any weird architecture that hardcodes IRQ -1 to some device? ;-)