thermal: of-thermal: add API for getting sensor ID from DT

This patch adds new API thermal_zone_of_get_sensor_id() to
provide the feature of getting sensor ID from DT thermal
zone's node. It's useful for thermal driver to register the
specific thermal zone devices from DT in a common way.
Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Reviewed-by: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/1582330132-13461-2-git-send-email-Anson.Huang@nxp.com

drivers/thermal/of-thermal.c

@@ -448,6 +448,50 @@ thermal_zone_of_add_sensor(struct device_node *zone,
 	return tzd;
 }
 
+/**
+ * thermal_zone_of_get_sensor_id - get sensor ID from a DT thermal zone
+ * @tz_np: a valid thermal zone device node.
+ * @sensor_np: a sensor node of a valid sensor device.
+ * @id: the sensor ID returned if success.
+ *
+ * This function will get sensor ID from a given thermal zone node and
+ * the sensor node must match the temperature provider @sensor_np.
+ *
+ * Return: 0 on success, proper error code otherwise.
+ */
+
+int thermal_zone_of_get_sensor_id(struct device_node *tz_np,
+				  struct device_node *sensor_np,
+				  u32 *id)
+{
+	struct of_phandle_args sensor_specs;
+	int ret;
+
+	ret = of_parse_phandle_with_args(tz_np,
+					 "thermal-sensors",
+					 "#thermal-sensor-cells",
+					 0,
+					 &sensor_specs);
+	if (ret)
+		return ret;
+
+	if (sensor_specs.np != sensor_np) {
+		of_node_put(sensor_specs.np);
+		return -ENODEV;
+	}
+
+	if (sensor_specs.args_count > 1)
+		pr_warn("%pOFn: too many cells in sensor specifier %d\n",
+		     sensor_specs.np, sensor_specs.args_count);
+
+	*id = sensor_specs.args_count ? sensor_specs.args[0] : 0;
+
+	of_node_put(sensor_specs.np);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(thermal_zone_of_get_sensor_id);
+
 /**
  * thermal_zone_of_sensor_register - registers a sensor to a DT thermal zone
  * @dev: a valid struct device pointer of a sensor device. Must contain
@@ -499,36 +543,22 @@ thermal_zone_of_sensor_register(struct device *dev, int sensor_id, void *data,
 	sensor_np = of_node_get(dev->of_node);
 
 	for_each_available_child_of_node(np, child) {
-		struct of_phandle_args sensor_specs;
 		int ret, id;
 
 		/* For now, thermal framework supports only 1 sensor per zone */
-		ret = of_parse_phandle_with_args(child, "thermal-sensors",
-						 "#thermal-sensor-cells",
-						 0, &sensor_specs);
+		ret = thermal_zone_of_get_sensor_id(child, sensor_np, &id);
 		if (ret)
 			continue;
 
-		if (sensor_specs.args_count >= 1) {
-			id = sensor_specs.args[0];
-			WARN(sensor_specs.args_count > 1,
-			     "%pOFn: too many cells in sensor specifier %d\n",
-			     sensor_specs.np, sensor_specs.args_count);
-		} else {
-			id = 0;
-		}
-
-		if (sensor_specs.np == sensor_np && id == sensor_id) {
+		if (id == sensor_id) {
 			tzd = thermal_zone_of_add_sensor(child, sensor_np,
 							 data, ops);
 			if (!IS_ERR(tzd))
 				tzd->ops->set_mode(tzd, THERMAL_DEVICE_ENABLED);
 
-			of_node_put(sensor_specs.np);
 			of_node_put(child);
 			goto exit;
 		}
-		of_node_put(sensor_specs.np);
 	}
 exit:
 	of_node_put(sensor_np);

include/linux/thermal.h

@@ -364,6 +364,9 @@ struct thermal_trip {
 
 /* Function declarations */
 #ifdef CONFIG_THERMAL_OF
+int thermal_zone_of_get_sensor_id(struct device_node *tz_np,
+				  struct device_node *sensor_np,
+				  u32 *id);
 struct thermal_zone_device *
 thermal_zone_of_sensor_register(struct device *dev, int id, void *data,
 				const struct thermal_zone_of_device_ops *ops);
@@ -375,6 +378,13 @@ struct thermal_zone_device *devm_thermal_zone_of_sensor_register(
 void devm_thermal_zone_of_sensor_unregister(struct device *dev,
 					    struct thermal_zone_device *tz);
 #else
+
+static int thermal_zone_of_get_sensor_id(struct device_node *tz_np,
+					 struct device_node *sensor_np,
+					 u32 *id)
+{
+	return -ENOENT;
+}
 static inline struct thermal_zone_device *
 thermal_zone_of_sensor_register(struct device *dev, int id, void *data,
 				const struct thermal_zone_of_device_ops *ops)