[PATCH] irq: fix possible null-pointer deref irq_domain_to_irq

[Jamie Iles <jamie@jamieiles.com>]

It is optional for an irqdomain to have a to_irq() method, and for
simple domains they often don't require any operations at all - just
hwirq to Linux irq translation.  Check we have valid ops before
dereferencing them.

Patch originally by Rob Herring.

Suggested-by: Rob Herring <robherring2@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Jamie Iles <jamie@jamieiles.com>
---

Rob, I can't see that you've already posted this but I didn't want to
hold Marc's GIC patches up.

 include/linux/irqdomain.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
index 99834e58..78a1e66 100644
--- a/include/linux/irqdomain.h
+++ b/include/linux/irqdomain.h
@@ -74,7 +74,7 @@ struct irq_domain {
 static inline unsigned int irq_domain_to_irq(struct irq_domain *d,
 					     unsigned long hwirq)
 {
-	if (d->ops->to_irq)
+	if (d->ops && d->ops->to_irq)
 		return d->ops->to_irq(d, hwirq);
 	if (WARN_ON(hwirq < d->hwirq_base))
 		return 0;
-- 
1.7.4.1