remoteproc: Introduce rproc_of_parse_firmware() helper

Add a new helper function rproc_of_parse_firmware() to the remoteproc
core that can be used by various remoteproc drivers to look up the
the "firmware-name" property from a rproc device node. This property
is already being used by multiple drivers, so this helper can avoid
repeating equivalent code in remoteproc drivers.

Signed-off-by: Suman Anna <s-anna@ti.com>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Link: https://lore.kernel.org/r/20200721223617.20312-3-s-anna@ti.com
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/remoteproc/remoteproc_core.c

@@ -1046,6 +1046,29 @@ rproc_of_resm_mem_entry_init(struct device *dev, u32 of_resm_idx, size_t len,
 }
 EXPORT_SYMBOL(rproc_of_resm_mem_entry_init);
 
+/**
+ * rproc_of_parse_firmware() - parse and return the firmware-name
+ * @dev: pointer on device struct representing a rproc
+ * @index: index to use for the firmware-name retrieval
+ * @fw_name: pointer to a character string, in which the firmware
+ *           name is returned on success and unmodified otherwise.
+ *
+ * This is an OF helper function that parses a device's DT node for
+ * the "firmware-name" property and returns the firmware name pointer
+ * in @fw_name on success.
+ *
+ * Return: 0 on success, or an appropriate failure.
+ */
+int rproc_of_parse_firmware(struct device *dev, int index, const char **fw_name)
+{
+	int ret;
+
+	ret = of_property_read_string_index(dev->of_node, "firmware-name",
+					    index, fw_name);
+	return ret ? ret : 0;
+}
+EXPORT_SYMBOL(rproc_of_parse_firmware);
+
 /*
  * A lookup table for resource handlers. The indices are defined in
  * enum fw_resource_type.

drivers/remoteproc/remoteproc_internal.h

@@ -28,6 +28,8 @@ struct rproc_debug_trace {
 void rproc_release(struct kref *kref);
 irqreturn_t rproc_vq_interrupt(struct rproc *rproc, int vq_id);
 void rproc_vdev_release(struct kref *ref);
+int rproc_of_parse_firmware(struct device *dev, int index,
+			    const char **fw_name);
 
 /* from remoteproc_virtio.c */
 int rproc_add_virtio_dev(struct rproc_vdev *rvdev, int id);