1 files changed, 70 insertions, 0 deletions
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index c460e0496006..c826ba4141fe 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -371,6 +371,76 @@ int irq_set_affinity_locked(struct irq_data *data, const struct cpumask *mask,
 	return ret;
 }
 
+/**
+ * irq_update_affinity_desc - Update affinity management for an interrupt
+ * @irq:	The interrupt number to update
+ * @affinity:	Pointer to the affinity descriptor
+ *
+ * This interface can be used to configure the affinity management of
+ * interrupts which have been allocated already.
+ *
+ * There are certain limitations on when it may be used - attempts to use it
+ * for when the kernel is configured for generic IRQ reservation mode (in
+ * config GENERIC_IRQ_RESERVATION_MODE) will fail, as it may conflict with
+ * managed/non-managed interrupt accounting. In addition, attempts to use it on
+ * an interrupt which is already started or which has already been configured
+ * as managed will also fail, as these mean invalid init state or double init.
+ */
+int irq_update_affinity_desc(unsigned int irq,
+			     struct irq_affinity_desc *affinity)
+{
+	struct irq_desc *desc;
+	unsigned long flags;
+	bool activated;
+	int ret = 0;
+
+	/*
+	 * Supporting this with the reservation scheme used by x86 needs
+	 * some more thought. Fail it for now.
+	 */
+	if (IS_ENABLED(CONFIG_GENERIC_IRQ_RESERVATION_MODE))
+		return -EOPNOTSUPP;
+
+	desc = irq_get_desc_buslock(irq, &flags, 0);
+	if (!desc)
+		return -EINVAL;
+
+	/* Requires the interrupt to be shut down */
+	if (irqd_is_started(&desc->irq_data)) {
+		ret = -EBUSY;
+		goto out_unlock;
+	}
+
+	/* Interrupts which are already managed cannot be modified */
+	if (irqd_affinity_is_managed(&desc->irq_data)) {
+		ret = -EBUSY;
+		goto out_unlock;
+	}
+
+	/*
+	 * Deactivate the interrupt. That's required to undo
+	 * anything an earlier activation has established.
+	 */
+	activated = irqd_is_activated(&desc->irq_data);
+	if (activated)
+		irq_domain_deactivate_irq(&desc->irq_data);
+
+	if (affinity->is_managed) {
+		irqd_set(&desc->irq_data, IRQD_AFFINITY_MANAGED);
+		irqd_set(&desc->irq_data, IRQD_MANAGED_SHUTDOWN);
+	}
+
+	cpumask_copy(desc->irq_common_data.affinity, &affinity->mask);
+
+	/* Restore the activation state */
+	if (activated)
+		irq_domain_activate_irq(&desc->irq_data, false);
+
+out_unlock:
+	irq_put_desc_busunlock(desc, flags);
+	return ret;
+}
+
 int __irq_set_affinity(unsigned int irq, const struct cpumask *mask, bool force)
 {
 	struct irq_desc *desc = irq_to_desc(irq);