From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from trinity.fluff.org (trinity.fluff.org [89.145.97.151]) by ozlabs.org (Postfix) with ESMTP id A092BDE368 for ; Tue, 12 Aug 2008 02:37:20 +1000 (EST) Date: Mon, 11 Aug 2008 17:36:48 +0100 From: Ben Dooks To: Anton Vorontsov Subject: Re: [PATCH] pata_of_platform: fix no irq handling Message-ID: <20080811163648.GI26082@trinity.fluff.org> References: <48A05152.7020508@harris.com> <20080811151913.GA14690@oksana.dev.rtsoft.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20080811151913.GA14690@oksana.dev.rtsoft.ru> Cc: linuxppc-dev@ozlabs.org, Jeff Garzik , linux-ide@vger.kernel.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Mon, Aug 11, 2008 at 07:19:13PM +0400, Anton Vorontsov wrote: > When no irq specified, pata_of_platform fills irq_res with -1, > which is wrong to do for two reasons: > > 1. By definition, 'no irq' should be IRQ 0, not some negative integer; interesting, IRQ 0 is actually valid on some ARM systems. > 2. pata_platform checks for irq_res.start > 0, but since irq_res.start > is unsigned type, the check will be true for `-1'. > > Reported-by: Steven A. Falco > Signed-off-by: Anton Vorontsov > --- > > On Mon, Aug 11, 2008 at 10:48:50AM -0400, Steven A. Falco wrote: > > I think there is a bug in the communications between pata_of_platform > > and pata_platform. I will refer to the master branch of the DENX git > > tree, which is roughly v2.6.26.1 at this time. I am using a Sequoia > > board with a PPC440EPx. > > > > In pata_of_platform, we have: > > > > ret = of_irq_to_resource(dn, 0, &irq_res); > > if (ret == NO_IRQ) > > irq_res.start = irq_res.end = -1; > > > > so if there is no interrupt defined, then start and end are -1. > > However, __pata_platform_probe has: > > > > if (irq_res && irq_res->start > 0) { > > irq = irq_res->start; > > irq_flags = irq_res->flags; > > } > > > > You might think that the (irq_res->start > 0) test will fail, as it > > should in this no-irq case. But, start is a u64, so the -1 actually > > looks like a large positive number in the comparison. So, > > __pata_platform_probe attempts to use an interrupt when there isn't one. > > > > I think the fix would be to change __pata_platform_probe to: > > > > if (irq_res && irq_res->start != -1) { > > > > but that might have other unintended consequences, so I'll defer to > > whomever knows more about the intent of this code. > > Something like this patch should work. Thanks for noticing! > > drivers/ata/pata_of_platform.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/drivers/ata/pata_of_platform.c b/drivers/ata/pata_of_platform.c > index 408da30..1f18ad9 100644 > --- a/drivers/ata/pata_of_platform.c > +++ b/drivers/ata/pata_of_platform.c > @@ -52,7 +52,7 @@ static int __devinit pata_of_platform_probe(struct of_device *ofdev, > > ret = of_irq_to_resource(dn, 0, &irq_res); > if (ret == NO_IRQ) > - irq_res.start = irq_res.end = -1; > + irq_res.start = irq_res.end = 0; > else > irq_res.flags = 0; > -- Ben Q: What's a light-year? A: One-third less calories than a regular year.