[PATCH] genirq: Only call irq_ack if implemented by chip

[Adrian-Ken Rueegsegger <ken@codelabs.ch>]

Restore the check if an IRQ chip implements the irq_ack function prior
to its invocation. Commit 22a49163e90d ("genirq: Provide compat handling
for chip->ack()") removed the check from handle_edge_irq while keeping
the check in other call paths.

Signed-off-by: Adrian-Ken Rueegsegger <ken@codelabs.ch>
---
 kernel/irq/chip.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index eb9a4ea..3889b02 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -586,7 +586,8 @@ handle_edge_irq(unsigned int irq, struct irq_desc *desc)
 	kstat_incr_irqs_this_cpu(irq, desc);
 
 	/* Start handling the irq */
-	desc->irq_data.chip->irq_ack(&desc->irq_data);
+	if (desc->irq_data.chip->irq_ack)
+		desc->irq_data.chip->irq_ack(&desc->irq_data);
 
 	do {
 		if (unlikely(!desc->action)) {
-- 
1.7.10.4