regulator: Add devres version of of_regulator_get_optional()

There are existing uses for a devres version of of_regulator_get_optional()
in power domain drivers. On MediaTek platforms, power domains may have
regulator supplies tied to them. The driver currently tries to use
devm_regulator_get() to not have to manage the lifecycle, but ends up
doing it in a very hacky way by replacing the device node of the power
domain controller device to the device node of the power domain that is
currently being registered, getting the supply, and reverting the device
node.

Provide a better API so that the hack can be replaced.

Signed-off-by: Chen-Yu Tsai <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

drivers/regulator/devres.c

···
 	return ptr;
 }
 EXPORT_SYMBOL_GPL(devm_regulator_irq_helper);
+
+#if IS_ENABLED(CONFIG_OF)
+static struct regulator *_devm_of_regulator_get(struct device *dev, struct device_node *node,
+						const char *id, int get_type)
+{
+	struct regulator **ptr, *regulator;
+
+	ptr = devres_alloc(devm_regulator_release, sizeof(*ptr), GFP_KERNEL);
+	if (!ptr)
+		return ERR_PTR(-ENOMEM);
+
+	regulator = _of_regulator_get(dev, node, id, get_type);
+	if (!IS_ERR(regulator)) {
+		*ptr = regulator;
+		devres_add(dev, ptr);
+	} else {
+		devres_free(ptr);
+	}
+
+	return regulator;
+}
+
+/**
+ * devm_of_regulator_get_optional - Resource managed of_regulator_get_optional()
+ * @dev: device used for dev_printk() messages and resource lifetime management
+ * @node: device node for regulator "consumer"
+ * @id:  supply name or regulator ID.
+ *
+ * Managed regulator_get_optional(). Regulators returned from this
+ * function are automatically regulator_put() on driver detach. See
+ * of_regulator_get_optional() for more information.
+ */
+struct regulator *devm_of_regulator_get_optional(struct device *dev, struct device_node *node,
+						 const char *id)
+{
+	return _devm_of_regulator_get(dev, node, id, OPTIONAL_GET);
+}
+EXPORT_SYMBOL_GPL(devm_of_regulator_get_optional);
+#endif

drivers/regulator/internal.h

···
 	return container_of(dev, struct regulator_dev, dev);
 }
 
+enum regulator_get_type {
+	NORMAL_GET,
+	EXCLUSIVE_GET,
+	OPTIONAL_GET,
+	MAX_GET_TYPE
+};
+
 #ifdef CONFIG_OF
 struct regulator_dev *of_regulator_dev_lookup(struct device *dev,
 					      struct device_node *np,
···
 			         const struct regulator_desc *desc,
 				 struct regulator_config *config,
 				 struct device_node **node);
+
+struct regulator *_of_regulator_get(struct device *dev, struct device_node *node,
+				    const char *id, enum regulator_get_type get_type);
 
 struct regulator_dev *of_parse_coupled_regulator(struct regulator_dev *rdev,
 						 int index);
···
 }
 
 #endif
-enum regulator_get_type {
-	NORMAL_GET,
-	EXCLUSIVE_GET,
-	OPTIONAL_GET,
-	MAX_GET_TYPE
-};
 
 int _regulator_get_common_check(struct device *dev, const char *id,
 				enum regulator_get_type get_type);

drivers/regulator/of_regulator.c

···
 	return ERR_PTR(-ENODEV);
 }
 
-static struct regulator *_of_regulator_get(struct device *dev, struct device_node *node,
-					   const char *id, enum regulator_get_type get_type)
+struct regulator *_of_regulator_get(struct device *dev, struct device_node *node,
+				    const char *id, enum regulator_get_type get_type)
 {
 	struct regulator_dev *r;
 	int ret;

include/linux/regulator/consumer.h

···
 struct regulator *__must_check of_regulator_get_optional(struct device *dev,
 							 struct device_node *node,
 							 const char *id);
+struct regulator *__must_check devm_of_regulator_get_optional(struct device *dev,
+							      struct device_node *node,
+							      const char *id);
 #else
 static inline struct regulator *__must_check of_regulator_get_optional(struct device *dev,
 								       struct device_node *node,
 								       const char *id)
+{
+	return ERR_PTR(-ENODEV);
+}
+
+static inline struct regulator *__must_check devm_of_regulator_get_optional(struct device *dev,
+									    struct device_node *node,
+									    const char *id)
 {
 	return ERR_PTR(-ENODEV);
 }
···
 static inline struct regulator *__must_check of_regulator_get_optional(struct device *dev,
 								       struct device_node *node,
 								       const char *id)
+{
+	return ERR_PTR(-ENODEV);
+}
+
+static inline struct regulator *__must_check devm_of_regulator_get_optional(struct device *dev,
+									    struct device_node *node,
+									    const char *id)
 {
 	return ERR_PTR(-ENODEV);
 }