[PATCH] pata_of_platform: fix no irq handling

[Anton Vorontsov <avorontsov@ru.mvista.com>]

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;
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@harris.com>
Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
---

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;
 
-- 
1.5.6.3