power_supply: Add power_supply_put for decrementing device reference counter

The power_supply_get_by_phandle() and power_supply_get_by_name() use
function class_find_device() for obtaining the reference to power
supply. Each use of class_find_device() increases the power supply's
device reference counter.

However the reference counter was not decreased by users of this API.
Thus final device_unregister() call from power_supply_unregister() could
not release the device and clean up its resources. This lead to memory
leak if at least once power_supply_get_by_*() was called between
registering and unregistering the power supply.

Add and document new API power_supply_put() for decrementing the
reference counter.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Reviewed-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Reviewed-by: Sebastian Reichel <sre@kernel.org>
Signed-off-by: Sebastian Reichel <sre@kernel.org>

1 files changed, 38 insertions, 0 deletions

diff --git a/drivers/power/power_supply_core.c b/drivers/power/power_supply_core.c
index e51405b176c8..b4ec14683b7f 100644
--- a/drivers/power/power_supply_core.c
+++ b/drivers/power/power_supply_core.c
@@ -336,6 +336,17 @@ static int power_supply_match_device_by_name(struct device *dev, const void *dat
         return strcmp(psy->desc->name, name) == 0;
 }
 
+/**
+ * power_supply_get_by_name() - Search for a power supply and returns its ref
+ * @name: Power supply name to fetch
+ *
+ * If power supply was found, it increases reference count for the
+ * internal power supply's device. The user should power_supply_put()
+ * after usage.
+ *
+ * Return: On success returns a reference to a power supply with
+ * matching name equals to @name, a NULL otherwise.
+ */
 struct power_supply *power_supply_get_by_name(const char *name)
 {
         struct device *dev = class_find_device(power_supply_class, NULL, name,
@@ -345,12 +356,39 @@ struct power_supply *power_supply_get_by_name(const char *name)
 }
 EXPORT_SYMBOL_GPL(power_supply_get_by_name);
 
+/**
+ * power_supply_put() - Drop reference obtained with power_supply_get_by_name
+ * @psy: Reference to put
+ *
+ * The reference to power supply should be put before unregistering
+ * the power supply.
+ */
+void power_supply_put(struct power_supply *psy)
+{
+        might_sleep();
+
+        put_device(&psy->dev);
+}
+EXPORT_SYMBOL_GPL(power_supply_put);
+
 #ifdef CONFIG_OF
 static int power_supply_match_device_node(struct device *dev, const void *data)
 {
         return dev->parent && dev->parent->of_node == data;
 }
 
+/**
+ * power_supply_get_by_phandle() - Search for a power supply and returns its ref
+ * @np: Pointer to device node holding phandle property
+ * @phandle_name: Name of property holding a power supply name
+ *
+ * If power supply was found, it increases reference count for the
+ * internal power supply's device. The user should power_supply_put()
+ * after usage.
+ *
+ * Return: On success returns a reference to a power supply with
+ * matching name equals to value under @property, NULL or ERR_PTR otherwise.
+ */
 struct power_supply *power_supply_get_by_phandle(struct device_node *np,
                                                         const char *property)
 {