thermal: core: Get thermal zone by id

The next patch will introduce the generic netlink protocol to handle
events, sampling and command from the thermal framework. In order to
deal with the thermal zone, it uses its unique identifier to
characterize it in the message. Passing an integer is more efficient
than passing an entire string.

This change provides a function returning back a thermal zone pointer
corresponding to the identifier passed as parameter.
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Reviewed-by: Amit Kucheria <amit.kucheria@linaro.org>
Acked-by: Zhang Rui <rui.zhang@intel.com>
Link: https://lore.kernel.org/r/20200706105538.2159-2-daniel.lezcano@linaro.org

drivers/thermal/thermal_core.c

@@ -732,6 +732,20 @@ int for_each_thermal_zone(int (*cb)(struct thermal_zone_device *, void *),
 	return ret;
 }
 
+struct thermal_zone_device *thermal_zone_get_by_id(int id)
+{
+	struct thermal_zone_device *tz = NULL;
+
+	mutex_lock(&thermal_list_lock);
+	list_for_each_entry(tz, &thermal_tz_list, node) {
+		if (tz->id == id)
+			break;
+	}
+	mutex_unlock(&thermal_list_lock);
+
+	return tz;
+}
+
 void thermal_zone_device_unbind_exception(struct thermal_zone_device *tz,
 					  const char *cdev_type, size_t size)
 {

drivers/thermal/thermal_core.h

@@ -50,6 +50,8 @@ int for_each_thermal_cooling_device(int (*cb)(struct thermal_cooling_device *,
 int for_each_thermal_governor(int (*cb)(struct thermal_governor *, void *),
 			      void *thermal_governor);
 
+struct thermal_zone_device *thermal_zone_get_by_id(int id);
+
 struct thermal_attr {
 	struct device_attribute attr;
 	char name[THERMAL_NAME_LENGTH];