From mboxrd@z Thu Jan 1 00:00:00 1970 From: Scott Wood Subject: Re: [PATCH v3] uio/pdrv_genirq: Add OF support Date: Tue, 19 Apr 2011 18:09:19 -0500 Message-ID: <20110419180919.17971598@schlenkerla.am.freescale.net> References: <1303116654-5042-1-git-send-email-monstr@monstr.eu> <20110419060816.GA5252@ponder.secretlab.ca> <20110419220018.GB2772@local> Mime-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20110419220018.GB2772@local> Sender: linux-kernel-owner@vger.kernel.org To: "Hans J. Koch" Cc: Grant Likely , devicetree-discuss@lists.ozlabs.org, linux-kernel@vger.kernel.org, john.williams@petalogix.com List-Id: devicetree@vger.kernel.org On Wed, 20 Apr 2011 00:00:18 +0200 "Hans J. Koch" wrote: > On Tue, Apr 19, 2011 at 12:08:16AM -0600, Grant Likely wrote: > > PowerPC and x86 will return 0 for an unassigned IRQ, as will most platforms. > > That might be right for these architectures. On ARM SoCs, IRQ0 is often a > normal irq like any other (e.g. "Audio DMA Controller 1" on Telechips TCC8000). It's true on at least some powerpc and x86 interrupt controllers as well. ARM isn't special. :-) I'm not sure what goes on on x86, as I see a real " 0:" in /proc/interrupts. But on powerpc, Linux's IRQ numberspace is decoupled from that of any IRQ controller. This is mainly to accommodate multiple IRQ controllers with their own numberspaces in the same system; being able to avoid irq 0 is just a bonus. -Scott