[PATCH v4/RFC 3/4] irq: Add irq_get_affinity() api

[Lina Iyer]

Export irq_get_affinity API for drivers to read the smp affinity of an
IRQ safely.

Signed-off-by: Lina Iyer <lina.iyer at linaro.org>
---
 include/linux/interrupt.h |  8 ++++++++
 kernel/irq/manage.c       | 18 ++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 69517a2..fff619c 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -260,6 +260,8 @@ extern int irq_set_affinity_hint(unsigned int irq, const struct cpumask *m);
 extern int
 irq_set_affinity_notifier(unsigned int irq, struct irq_affinity_notify *notify);
 
+extern int irq_get_affinity(unsigned int irq, struct cpumask *mask);
+
 #else /* CONFIG_SMP */
 
 static inline int irq_set_affinity(unsigned int irq, const struct cpumask *m)
@@ -290,6 +292,12 @@ irq_set_affinity_notifier(unsigned int irq, struct irq_affinity_notify *notify)
 {
 	return 0;
 }
+
+static inline int irq_get_affinity(unsigned int irq, struct cpumask *mask)
+{
+	return -EINVAL;
+}
+
 #endif /* CONFIG_SMP */
 
 /*
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 0a9104b..2d17098 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -246,6 +246,24 @@ int irq_set_affinity_hint(unsigned int irq, const struct cpumask *m)
 }
 EXPORT_SYMBOL_GPL(irq_set_affinity_hint);
 
+int irq_get_affinity(unsigned int irq, struct cpumask *mask)
+{
+	struct irq_desc *desc = irq_to_desc(irq);
+	unsigned long flags;
+
+	if (!mask)
+		return -EINVAL;
+
+	raw_spin_lock_irqsave(&desc->lock, flags);
+	if (!irqd_irq_disabled(&desc->irq_data))
+		cpumask_copy(mask, desc->irq_data.affinity);
+	else
+		cpumask_clear(mask);
+	raw_spin_unlock_irqrestore(&desc->lock, flags);
+
+	return 0;
+}
+
 static void irq_affinity_notify(struct work_struct *work)
 {
 	struct irq_affinity_notify *notify =
-- 
2.1.0