ACPI: battery: create alarm sysfs attribute atomically

Let the power supply core register the attribute.
This ensures that the attribute is created before the device is
announced to userspace, avoid a race condition.
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/battery.c

@@ -678,12 +678,18 @@ static ssize_t acpi_battery_alarm_store(struct device *dev,
 	return count;
 }
 
-static const struct device_attribute alarm_attr = {
+static struct device_attribute alarm_attr = {
 	.attr = {.name = "alarm", .mode = 0644},
 	.show = acpi_battery_alarm_show,
 	.store = acpi_battery_alarm_store,
 };
 
+static struct attribute *acpi_battery_attrs[] = {
+	&alarm_attr.attr,
+	NULL
+};
+ATTRIBUTE_GROUPS(acpi_battery);
+
 /*
  * The Battery Hooking API
  *
@@ -823,7 +829,10 @@ static void __exit battery_hook_exit(void)
 
 static int sysfs_add_battery(struct acpi_battery *battery)
 {
-	struct power_supply_config psy_cfg = { .drv_data = battery, };
+	struct power_supply_config psy_cfg = {
+		.drv_data = battery,
+		.attr_grp = acpi_battery_groups,
+	};
 	bool full_cap_broken = false;
 
 	if (!ACPI_BATTERY_CAPACITY_VALID(battery->full_charge_capacity) &&
@@ -868,7 +877,7 @@ static int sysfs_add_battery(struct acpi_battery *battery)
 		return result;
 	}
 	battery_hook_add_battery(battery);
-	return device_create_file(&battery->bat->dev, &alarm_attr);
+	return 0;
 }
 
 static void sysfs_remove_battery(struct acpi_battery *battery)
@@ -879,7 +888,6 @@ static void sysfs_remove_battery(struct acpi_battery *battery)
 		return;
 	}
 	battery_hook_remove_battery(battery);
-	device_remove_file(&battery->bat->dev, &alarm_attr);
 	power_supply_unregister(battery->bat);
 	battery->bat = NULL;
 	mutex_unlock(&battery->sysfs_lock);