of/irq: Add of_msi_xlate() helper function

Add an of_msi_xlate() helper that maps a device ID and returns
the device node of the MSI controller the device ID is mapped to.

Required by core functions that need an MSI controller device node
pointer at the same time as a mapped device ID, of_msi_map_id() is not
sufficient for that purpose.

Signed-off-by: Lorenzo Pieralisi <[e-mail]>
Reviewed-by: Marc Zyngier <[e-mail]>
Cc: Rob Herring <[e-mail]>
Cc: Marc Zyngier <[e-mail]>
Reviewed-by: Rob Herring (Arm) <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Marc Zyngier <[e-mail]>

drivers/of/irq.c

···
 	}
 }
 
-static u32 __of_msi_map_id(struct device *dev, struct device_node **np,
-			    u32 id_in)
+/**
+ * of_msi_xlate - map a MSI ID and find relevant MSI controller node
+ * @dev: device for which the mapping is to be done.
+ * @msi_np: Pointer to store the MSI controller node
+ * @id_in: Device ID.
+ *
+ * Walk up the device hierarchy looking for devices with a "msi-map"
+ * property. If found, apply the mapping to @id_in. @msi_np pointed
+ * value must be NULL on entry, if an MSI controller is found @msi_np is
+ * initialized to the MSI controller node with a reference held.
+ *
+ * Returns: The mapped MSI id.
+ */
+u32 of_msi_xlate(struct device *dev, struct device_node **msi_np, u32 id_in)
 {
 	struct device *parent_dev;
 	u32 id_out = id_in;
···
 	 */
 	for (parent_dev = dev; parent_dev; parent_dev = parent_dev->parent)
 		if (!of_map_id(parent_dev->of_node, id_in, "msi-map",
-				"msi-map-mask", np, &id_out))
+				"msi-map-mask", msi_np, &id_out))
 			break;
 	return id_out;
 }
···
  */
 u32 of_msi_map_id(struct device *dev, struct device_node *msi_np, u32 id_in)
 {
-	return __of_msi_map_id(dev, &msi_np, id_in);
+	return of_msi_xlate(dev, &msi_np, id_in);
 }
 
 /**
···
 {
 	struct device_node *np = NULL;
 
-	__of_msi_map_id(dev, &np, id);
+	of_msi_xlate(dev, &np, id);
 	return irq_find_matching_host(np, bus_token);
 }
 

include/linux/of_irq.h

···
 							u32 id,
 							u32 bus_token);
 extern void of_msi_configure(struct device *dev, const struct device_node *np);
+extern u32 of_msi_xlate(struct device *dev, struct device_node **msi_np, u32 id_in);
 u32 of_msi_map_id(struct device *dev, struct device_node *msi_np, u32 id_in);
 #else
 static inline void of_irq_init(const struct of_device_id *matches)
···
 }
 static inline void of_msi_configure(struct device *dev, struct device_node *np)
 {
+}
+static inline u32 of_msi_xlate(struct device *dev, struct device_node **msi_np, u32 id_in)
+{
+	return id_in;
 }
 static inline u32 of_msi_map_id(struct device *dev,
 				 struct device_node *msi_np, u32 id_in)