genirq: Allow the affinity of a percpu interrupt to be set/retrieved

In order to prepare the genirq layer for the concept of partitionned
percpu interrupts, let's allow an affinity to be associated with
such an interrupt. We introduce:

- irq_set_percpu_devid_partition: flag an interrupt as a percpu-devid
interrupt, and associate it with an affinity
- irq_get_percpu_devid_partition: allow the affinity of that interrupt
to be retrieved.

This will allow a driver to discover which CPUs the per-cpu interrupt
can actually fire on.

Signed-off-by: Marc Zyngier <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: [e-mail]
Cc: Jason Cooper <[e-mail]>
Cc: Will Deacon <[e-mail]>
Cc: Rob Herring <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Thomas Gleixner <[e-mail]>

include/linux/irq.h

···
 }
 
 extern int irq_set_percpu_devid(unsigned int irq);
+extern int irq_set_percpu_devid_partition(unsigned int irq,
+					  const struct cpumask *affinity);
+extern int irq_get_percpu_devid_partition(unsigned int irq,
+					  struct cpumask *affinity);
 
 extern void
 __irq_set_handler(unsigned int irq, irq_flow_handler_t handle, int is_chained,

include/linux/irqdesc.h

···
 	int			threads_handled_last;
 	raw_spinlock_t		lock;
 	struct cpumask		*percpu_enabled;
+	const struct cpumask	*percpu_affinity;
 #ifdef CONFIG_SMP
 	const struct cpumask	*affinity_hint;
 	struct irq_affinity_notify *affinity_notify;

kernel/irq/irqdesc.c

···
 		chip_bus_sync_unlock(desc);
 }
 
-int irq_set_percpu_devid(unsigned int irq)
+int irq_set_percpu_devid_partition(unsigned int irq,
+				   const struct cpumask *affinity)
 {
 	struct irq_desc *desc = irq_to_desc(irq);
 
···
 	if (!desc->percpu_enabled)
 		return -ENOMEM;
 
+	if (affinity)
+		desc->percpu_affinity = affinity;
+	else
+		desc->percpu_affinity = cpu_possible_mask;
+
 	irq_set_percpu_devid_flags(irq);
+	return 0;
+}
+
+int irq_set_percpu_devid(unsigned int irq)
+{
+	return irq_set_percpu_devid_partition(irq, NULL);
+}
+
+int irq_get_percpu_devid_partition(unsigned int irq, struct cpumask *affinity)
+{
+	struct irq_desc *desc = irq_to_desc(irq);
+
+	if (!desc || !desc->percpu_enabled)
+		return -EINVAL;
+
+	if (affinity)
+		cpumask_copy(affinity, desc->percpu_affinity);
+
 	return 0;
 }