ANDROID: power_supply: Add a helper function to retrieve psy array from phandle

power_supply_get_by_phandle retrieves power_supply object based on
phandle. However, when multiple power_supply objects are registered
by the same parent device the first power_supply object's reference
is returned. This returned power_supply object's reference varies
according to probe order. Add a helper to return all the power_supply
object's reference.

The caller has to provide the power_supply pointer array.
-EOVERFLOW is returned when the size of the array is not enough to
pass back all the power_supply objects.

Patch was sent to mainline linux, however, was deemed incomplete due
to lack of mainline user.

Link: https://lore.kernel.org/linux-pm/20200407211243.247362-1-badhri@google.com/T/
Bug: 161416774
Bug: 167486462
Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>
Change-Id: I6d9c52edb4472e73fc2d3c8eb32a41bec8bbde2a

drivers/power/supply/power_supply_core.c

@@ -32,6 +32,13 @@ EXPORT_SYMBOL_GPL(power_supply_notifier);
 
 static struct device_type power_supply_dev_type;
 
+struct match_device_node_array_param {
+	struct device_node *parent_of_node;
+	struct power_supply **psy;
+	ssize_t psy_size;
+	ssize_t psy_count;
+};
+
 #define POWER_SUPPLY_DEFERRED_REGISTER_TIME	msecs_to_jiffies(10)
 
 static bool __power_supply_is_supplied_by(struct power_supply *supplier,
@@ -522,6 +529,77 @@ struct power_supply *power_supply_get_by_phandle(struct device_node *np,
 }
 EXPORT_SYMBOL_GPL(power_supply_get_by_phandle);
 
+static int power_supply_match_device_node_array(struct device *dev,
+						void *data)
+{
+	struct match_device_node_array_param *param =
+		(struct match_device_node_array_param *)data;
+	struct power_supply **psy = param->psy;
+	ssize_t size = param->psy_size;
+	ssize_t *count = &param->psy_count;
+
+	if (!dev->parent || dev->parent->of_node != param->parent_of_node)
+		return 0;
+
+	if (*count >= size)
+		return -EOVERFLOW;
+
+	psy[*count] = dev_get_drvdata(dev);
+	atomic_inc(&psy[*count]->use_cnt);
+	(*count)++;
+
+	return 0;
+}
+
+/**
+ * power_supply_get_by_phandle_array() - Similar to
+ * power_supply_get_by_phandle but returns an array of power supply
+ * objects which are associated with the phandle.
+ * @np: Pointer to device node holding phandle property.
+ * @property: Name of property holding a power supply name.
+ * @psy: Array of power_supply pointers provided by the client which is
+ * filled by power_supply_get_by_phandle_array.
+ * @size: size of power_supply pointer array.
+ *
+ * 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 the number of power supply objects filled
+ * in the @psy array.
+ * -EOVERFLOW when size of @psy array is not suffice.
+ * -EINVAL when @psy is NULL or @size is 0.
+ * -ENODEV when matching device_node is not found.
+ */
+int power_supply_get_by_phandle_array(struct device_node *np,
+				      const char *property,
+				      struct power_supply **psy,
+				      ssize_t size)
+{
+	struct device_node *power_supply_np;
+	int ret;
+	struct match_device_node_array_param param;
+
+	if (!psy || !size)
+		return -EINVAL;
+
+	power_supply_np = of_parse_phandle(np, property, 0);
+	if (!power_supply_np)
+		return -ENODEV;
+
+	param.parent_of_node = power_supply_np;
+	param.psy = psy;
+	param.psy_size = size;
+	param.psy_count = 0;
+	ret = class_for_each_device(power_supply_class, NULL, &param,
+				    power_supply_match_device_node_array);
+
+	of_node_put(power_supply_np);
+
+	return param.psy_count;
+}
+EXPORT_SYMBOL_GPL(power_supply_get_by_phandle_array);
+
 static void devm_power_supply_put(struct device *dev, void *res)
 {
 	struct power_supply **psy = res;

include/linux/power_supply.h

@@ -379,12 +379,21 @@ extern void power_supply_put(struct power_supply *psy);
 #ifdef CONFIG_OF
 extern struct power_supply *power_supply_get_by_phandle(struct device_node *np,
 							const char *property);
+extern int power_supply_get_by_phandle_array(struct device_node *np,
+					     const char *property,
+					     struct power_supply **psy,
+					     ssize_t size);
 extern struct power_supply *devm_power_supply_get_by_phandle(
 				    struct device *dev, const char *property);
 #else /* !CONFIG_OF */
 static inline struct power_supply *
 power_supply_get_by_phandle(struct device_node *np, const char *property)
 { return NULL; }
+static int power_supply_get_by_phandle_array(struct device_node *np,
+					     const char *property,
+					     struct power_supply **psy,
+					     int size)
+{ return 0; }
 static inline struct power_supply *
 devm_power_supply_get_by_phandle(struct device *dev, const char *property)
 { return NULL; }