PM / devfreq: Add devm_devfreq_{register,unregister}_opp_notfier function

This patch add resource-managed function for devfreq opp as following
functions. The devm_devfreq_register_opp_notifier() manages automatically
the registration of devfreq opp using device resource management.
- devm_devfreq_register_opp_notifier
- devm_devfreq_unregister_opp_notifier()

Signed-off-by: Chanwoo Choi <[e-mail]>
Signed-off-by: MyungJoo Ham <[e-mail]>

drivers/devfreq/devfreq.c

···
 	return ret;
 }
 
+static void devm_devfreq_opp_release(struct device *dev, void *res)
+{
+	devfreq_unregister_opp_notifier(dev, *(struct devfreq **)res);
+}
+
+/**
+ * devm_ devfreq_register_opp_notifier()
+ *		- Resource-managed devfreq_register_opp_notifier()
+ * @dev:	The devfreq user device. (parent of devfreq)
+ * @devfreq:	The devfreq object.
+ */
+int devm_devfreq_register_opp_notifier(struct device *dev,
+				       struct devfreq *devfreq)
+{
+	struct devfreq **ptr;
+	int ret;
+
+	ptr = devres_alloc(devm_devfreq_opp_release, sizeof(*ptr), GFP_KERNEL);
+	if (!ptr)
+		return -ENOMEM;
+
+	ret = devfreq_register_opp_notifier(dev, devfreq);
+	if (ret) {
+		devres_free(ptr);
+		return ret;
+	}
+
+	*ptr = devfreq;
+	devres_add(dev, ptr);
+
+	return 0;
+}
+EXPORT_SYMBOL(devm_devfreq_register_opp_notifier);
+
+/**
+ * devm_devfreq_unregister_opp_notifier()
+ *		- Resource-managed devfreq_unregister_opp_notifier()
+ * @dev:	The devfreq user device. (parent of devfreq)
+ * @devfreq:	The devfreq object.
+ */
+void devm_devfreq_unregister_opp_notifier(struct device *dev,
+					 struct devfreq *devfreq)
+{
+	WARN_ON(devres_release(dev, devm_devfreq_opp_release,
+			       devm_devfreq_dev_match, devfreq));
+}
+EXPORT_SYMBOL(devm_devfreq_unregister_opp_notifier);
+
 MODULE_AUTHOR("MyungJoo Ham <[e-mail]>");
 MODULE_DESCRIPTION("devfreq class support");
 MODULE_LICENSE("GPL");

include/linux/devfreq.h

···
 					 struct devfreq *devfreq);
 extern int devfreq_unregister_opp_notifier(struct device *dev,
 					   struct devfreq *devfreq);
+extern int devm_devfreq_register_opp_notifier(struct device *dev,
+					      struct devfreq *devfreq);
+extern void devm_devfreq_unregister_opp_notifier(struct device *dev,
+						struct devfreq *devfreq);
 
 #if IS_ENABLED(CONFIG_DEVFREQ_GOV_SIMPLE_ONDEMAND)
 /**
···
 	return -EINVAL;
 }
 
+static inline int devm_devfreq_register_opp_notifier(struct device *dev,
+						     struct devfreq *devfreq)
+{
+	return -EINVAL;
+}
+
+static inline void devm_devfreq_unregister_opp_notifier(struct device *dev,
+							struct devfreq *devfreq)
+{
+}
 #endif /* CONFIG_PM_DEVFREQ */
 
 #endif /* __LINUX_DEVFREQ_H__ */