[PATCH v4 13/20] power_supply: Increment power supply use counter when obtaining references

[Krzysztof Kozlowski]

Increment the power_supply.use_cnt usage counter on:
 - power_supply_get_by_phandle()
 - power_supply_get_by_name()
and decrement it on power_supply_put() call.

This helps tracking of valid usage of power supply instance by
consumers. The usage counter itself also allows safe calling of
power_supply_get_property-like functions even when driver unregisters
this power supply.

Signed-off-by: Krzysztof Kozlowski <k.kozlow...@samsung.com>
Reviewed-by: Bartlomiej Zolnierkiewicz <b.zolnier...@samsung.com>
---
 drivers/power/power_supply_core.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/power/power_supply_core.c 
b/drivers/power/power_supply_core.c
index a94f8c9d5e1e..819430a0bfa6 100644
--- a/drivers/power/power_supply_core.c
+++ b/drivers/power/power_supply_core.c
@@ -349,10 +349,16 @@ static int power_supply_match_device_by_name(struct 
device *dev, const void *dat
  */
 struct power_supply *power_supply_get_by_name(const char *name)
 {
+       struct power_supply *psy = NULL;
        struct device *dev = class_find_device(power_supply_class, NULL, name,
                                        power_supply_match_device_by_name);
 
-       return dev ? dev_get_drvdata(dev) : NULL;
+       if (dev) {
+               psy = dev_get_drvdata(dev);
+               atomic_inc(&psy->use_cnt);
+       }
+
+       return psy;
 }
 EXPORT_SYMBOL_GPL(power_supply_get_by_name);
 
@@ -367,6 +373,7 @@ void power_supply_put(struct power_supply *psy)
 {
        might_sleep();
 
+       atomic_dec(&psy->use_cnt);
        put_device(&psy->dev);
 }
 EXPORT_SYMBOL_GPL(power_supply_put);
@@ -393,6 +400,7 @@ struct power_supply *power_supply_get_by_phandle(struct 
device_node *np,
                                                        const char *property)
 {
        struct device_node *power_supply_np;
+       struct power_supply *psy = NULL;
        struct device *dev;
 
        power_supply_np = of_parse_phandle(np, property, 0);
@@ -404,7 +412,12 @@ struct power_supply *power_supply_get_by_phandle(struct 
device_node *np,
 
        of_node_put(power_supply_np);
 
-       return dev ? dev_get_drvdata(dev) : NULL;
+       if (dev) {
+               psy = dev_get_drvdata(dev);
+               atomic_inc(&psy->use_cnt);
+       }
+
+       return psy;
 }
 EXPORT_SYMBOL_GPL(power_supply_get_by_phandle);
 #endif /* CONFIG_OF */
-- 
1.9.1

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