power: add to_power_supply macro to the API

This patch adds the to_power_supply macro to upcast
a device to a power_supply struct.

This is needed because the same piece of code using
container_of is used in various other places, so we
abstract away such low-level operations via a macro.

Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Ognjen Galic <smclt30p@gmail.com>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/power/supply/ds2780_battery.c

@@ -56,11 +56,6 @@ to_ds2780_device_info(struct power_supply *psy)
 	return power_supply_get_drvdata(psy);
 }
 
-static inline struct power_supply *to_power_supply(struct device *dev)
-{
-	return dev_get_drvdata(dev);
-}
-
 static inline int ds2780_battery_io(struct ds2780_device_info *dev_info,
 	char *buf, int addr, size_t count, int io)
 {

drivers/power/supply/ds2781_battery.c

@@ -54,11 +54,6 @@ to_ds2781_device_info(struct power_supply *psy)
 	return power_supply_get_drvdata(psy);
 }
 
-static inline struct power_supply *to_power_supply(struct device *dev)
-{
-	return dev_get_drvdata(dev);
-}
-
 static inline int ds2781_battery_io(struct ds2781_device_info *dev_info,
 	char *buf, int addr, size_t count, int io)
 {

drivers/power/supply/power_supply_core.c

@@ -668,7 +668,7 @@ EXPORT_SYMBOL_GPL(power_supply_powers);
 
 static void power_supply_dev_release(struct device *dev)
 {
-	struct power_supply *psy = container_of(dev, struct power_supply, dev);
+	struct power_supply *psy = to_power_supply(dev);
 	dev_dbg(dev, "%s\n", __func__);
 	kfree(psy);
 }

include/linux/power_supply.h

@@ -371,6 +371,8 @@ devm_power_supply_register_no_ws(struct device *parent,
 extern void power_supply_unregister(struct power_supply *psy);
 extern int power_supply_powers(struct power_supply *psy, struct device *dev);
 
+#define to_power_supply(device) container_of(device, struct power_supply, dev)
+
 extern void *power_supply_get_drvdata(struct power_supply *psy);
 /* For APM emulation, think legacy userspace. */
 extern struct class *power_supply_class;