power_supply: Ignore -ENODATA errors when generating uevents

Sometimes a driver can not report a meaningful value for a certain property
and returns -ENODATA.

Currently when generating a uevent and a property return -ENODATA it is
treated as an error an no uevent is generated at all. This is not an
desirable behavior.

This patch adds a special case for -ENODATA and ignores properties which
return this error code when generating the uevent.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Tested-by: Grazvydas Ignotas <notasas@gmail.com>

drivers/power/power_supply_sysfs.c

@@ -270,7 +270,7 @@ int power_supply_uevent(struct device *dev, struct kobj_uevent_env *env)
 		attr = &power_supply_attrs[psy->properties[j]];
 
 		ret = power_supply_show_property(dev, attr, prop_buf);
-		if (ret == -ENODEV) {
+		if (ret == -ENODEV || ret == -ENODATA) {
 			/* When a battery is absent, we expect -ENODEV. Don't abort;
 			   send the uevent with at least the the PRESENT=0 property */
 			ret = 0;