of/irq: Add interrupt affinity reporting interface

Plug the irq_populate_fwspec_info() helper into the OF layer to offer an
interrupt affinity reporting function.

Signed-off-by: Marc Zyngier <[e-mail]>
Signed-off-by: Thomas Gleixner <[e-mail]>
Tested-by: Will Deacon <[e-mail]>
Reviewed-by: Jonathan Cameron <[e-mail]>
Link: https://patch.msgid.link/[e-mail]

drivers/of/irq.c

···
 }
 EXPORT_SYMBOL_GPL(of_irq_get);
 
+const struct cpumask *of_irq_get_affinity(struct device_node *dev, int index)
+{
+	struct of_phandle_args oirq;
+	struct irq_fwspec_info info;
+	struct irq_fwspec fwspec;
+	int rc;
+
+	rc = of_irq_parse_one(dev, index, &oirq);
+	if (rc)
+		return NULL;
+
+	of_phandle_args_to_fwspec(oirq.np, oirq.args, oirq.args_count,
+				  &fwspec);
+
+	if (irq_populate_fwspec_info(&fwspec, &info))
+		return NULL;
+
+	return info.affinity;
+}
+
 /**
  * of_irq_get_byname - Decode a node's IRQ and return it as a Linux IRQ number
  * @dev: pointer to device tree node

include/linux/of_irq.h

···
 			  struct of_phandle_args *out_irq);
 extern int of_irq_count(struct device_node *dev);
 extern int of_irq_get(struct device_node *dev, int index);
+extern const struct cpumask *of_irq_get_affinity(struct device_node *dev,
+						      int index);
 extern int of_irq_get_byname(struct device_node *dev, const char *name);
 extern int of_irq_to_resource_table(struct device_node *dev,
 		struct resource *res, int nr_irqs);
···
 static inline int of_irq_get_byname(struct device_node *dev, const char *name)
 {
 	return 0;
+}
+static inline const struct cpumask *of_irq_get_affinity(struct device_node *dev,
+							int index)
+{
+	return NULL;
 }
 static inline int of_irq_to_resource_table(struct device_node *dev,
 					   struct resource *res, int nr_irqs)