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 <sfalco@xxxxxxxxxx>
> Signed-off-by: Anton Vorontsov <avorontsov@xxxxxxxxxxxxx>
> ---
>
> 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.
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