power_supply: fix return value of get_property

power_supply_get_property() should ideally return -EAGAIN if it is
called while the power_supply is being registered. There was no way
previously to determine if use_cnt == 0 meant that the power_supply
wasn't fully registered yet, or if it had already been unregistered.

Add a new boolean to the power_supply struct to simply show if
registration is completed. Lastly, modify the check in
power_supply_show_property() to also ignore -EAGAIN when so it
doesn't complain about not returning the property.
Signed-off-by: Rhyland Klein <rklein@nvidia.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>

drivers/power/power_supply_core.c

@@ -491,8 +491,11 @@ int power_supply_get_property(struct power_supply *psy,
 			    enum power_supply_property psp,
 			    union power_supply_propval *val)
 {
-	if (atomic_read(&psy->use_cnt) <= 0)
+	if (atomic_read(&psy->use_cnt) <= 0) {
+		if (!psy->initialized)
+			return -EAGAIN;
 		return -ENODEV;
+	}
 
 	return psy->desc->get_property(psy, psp, val);
 }
@@ -780,6 +783,7 @@ __power_supply_register(struct device *parent,
 	 *    after calling power_supply_register()).
 	 */
 	atomic_inc(&psy->use_cnt);
+	psy->initialized = true;
 
 	queue_delayed_work(system_power_efficient_wq,
 			   &psy->deferred_register_work,

drivers/power/power_supply_sysfs.c

@@ -83,7 +83,7 @@ static ssize_t power_supply_show_property(struct device *dev,
 			if (ret == -ENODATA)
 				dev_dbg(dev, "driver has no data for `%s' property\n",
 					attr->attr.name);
-			else if (ret != -ENODEV)
+			else if (ret != -ENODEV && ret != -EAGAIN)
 				dev_err(dev, "driver failed to report `%s' property: %zd\n",
 					attr->attr.name, ret);
 			return ret;

include/linux/power_supply.h

@@ -248,6 +248,7 @@ struct power_supply {
 	struct delayed_work deferred_register_work;
 	spinlock_t changed_lock;
 	bool changed;
+	bool initialized;
 	atomic_t use_cnt;
 #ifdef CONFIG_THERMAL
 	struct thermal_zone_device *tzd;