From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Hans J. Koch" Subject: Re: [PATCH 2/2] uio: add an of_genirq driver Date: Mon, 15 Jun 2009 01:45:46 +0200 Message-ID: <20090614234546.GJ3639@local> References: <1244765062-14144-1-git-send-email-w.sang@pengutronix.de> <1244765062-14144-3-git-send-email-w.sang@pengutronix.de> <20090614122136.GD3639@local> <20090615001207.1829e7b5@lxorguk.ukuu.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20090615001207.1829e7b5-qBU/x9rampVanCEyBjwyrvXRex20P6io@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-mnsaURCQ41sdnm+yROfE0A@public.gmane.org Errors-To: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-mnsaURCQ41sdnm+yROfE0A@public.gmane.org To: Alan Cox Cc: devicetree-discuss-mnsaURCQ41sdnm+yROfE0A@public.gmane.org, "Hans J. Koch" , Magnus Damm , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linuxppc-dev-mnsaURCQ41sdnm+yROfE0A@public.gmane.org, Greg KH List-Id: devicetree@vger.kernel.org On Mon, Jun 15, 2009 at 12:12:07AM +0100, Alan Cox wrote: > > > + if (!uioinfo->irq) > > > + uioinfo->irq = UIO_IRQ_NONE; > > > > Please don't do this. It's inconsistent if all other UIO drivers require > > people to use UIO_IRQ_NONE and you also allow zero. UIO_IRQ_NONE was > > introduced because 0 may be a legal interrupt number on some platforms. > > Zero is not a valid IRQ number in the kernel (except in arch specific > depths). IRQ numbers are also *unsigned* so -1 isn't a safe definition. The above uioinfo->irq is a signed long. > > Zero means no IRQ. If any old UIO code is assuming otherwise it wants > fixing. It doesn't. It won't complain about IRQ 0 and will pass it on to request_irq, which will probably fail if it is as you say. I did it that way because I saw IRQ 0 in /proc/interrupts on every PC... > > It is the job of the platform to map a physical IRQ 0 to some other > representation if it exists outside of arch specific code. Funny. > This was > decided some years ago and a large part of the kernel simply doesn't > support any notion of a real IRQ 0. Can you tell me the reason for that decision or point me to some ml archive? Thanks, Hans > > Alan