thermal: core: Add helpers to browse the cdev, tz and governor list

The cdev, tz and governor list, as well as their respective locks are
statically defined in the thermal_core.c file.

In order to give a sane access to these list, like browsing all the
thermal zones or all the cooling devices, let's define a set of
helpers where we pass a callback as a parameter to be called for each
thermal entity.

We keep the self-encapsulation and ensure the locks are correctly
taken when looking at the list.
Acked-by: Zhang Rui <rui.zhang@intel.com>
Reviewed-by: Amit Kucheria <amit.kucheria@linaro.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20200706105538.2159-1-daniel.lezcano@linaro.org

drivers/thermal/thermal_core.c

@@ -681,6 +681,57 @@ void thermal_zone_device_rebind_exception(struct thermal_zone_device *tz,
 	mutex_unlock(&thermal_list_lock);
 }
 
+int for_each_thermal_governor(int (*cb)(struct thermal_governor *, void *),
+			      void *data)
+{
+	struct thermal_governor *gov;
+	int ret = 0;
+
+	mutex_lock(&thermal_governor_lock);
+	list_for_each_entry(gov, &thermal_governor_list, governor_list) {
+		ret = cb(gov, data);
+		if (ret)
+			break;
+	}
+	mutex_unlock(&thermal_governor_lock);
+
+	return ret;
+}
+
+int for_each_thermal_cooling_device(int (*cb)(struct thermal_cooling_device *,
+					      void *), void *data)
+{
+	struct thermal_cooling_device *cdev;
+	int ret = 0;
+
+	mutex_lock(&thermal_list_lock);
+	list_for_each_entry(cdev, &thermal_cdev_list, node) {
+		ret = cb(cdev, data);
+		if (ret)
+			break;
+	}
+	mutex_unlock(&thermal_list_lock);
+
+	return ret;
+}
+
+int for_each_thermal_zone(int (*cb)(struct thermal_zone_device *, void *),
+			  void *data)
+{
+	struct thermal_zone_device *tz;
+	int ret = 0;
+
+	mutex_lock(&thermal_list_lock);
+	list_for_each_entry(tz, &thermal_tz_list, node) {
+		ret = cb(tz, data);
+		if (ret)
+			break;
+	}
+	mutex_unlock(&thermal_list_lock);
+
+	return ret;
+}
+
 void thermal_zone_device_unbind_exception(struct thermal_zone_device *tz,
 					  const char *cdev_type, size_t size)
 {

drivers/thermal/thermal_core.h

@@ -41,6 +41,15 @@ extern struct thermal_governor *__governor_thermal_table_end[];
 	     __governor < __governor_thermal_table_end;	\
 	     __governor++)
 
+int for_each_thermal_zone(int (*cb)(struct thermal_zone_device *, void *),
+			  void *);
+
+int for_each_thermal_cooling_device(int (*cb)(struct thermal_cooling_device *,
+					      void *), void *);
+
+int for_each_thermal_governor(int (*cb)(struct thermal_governor *, void *),
+			      void *thermal_governor);
+
 struct thermal_attr {
 	struct device_attribute attr;
 	char name[THERMAL_NAME_LENGTH];