virtio: split device_register into device_initialize and device_add

In order to make caller do a simple cleanup, we split device_register
into device_initialize and device_add. device_initialize always succeeds,
so the caller can always use put_device when register_virtio_device faild.
Signed-off-by: weiping zhang <zhangweiping@didichuxing.com>
Suggested-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>

drivers/virtio/virtio.c

@@ -303,11 +303,21 @@ void unregister_virtio_driver(struct virtio_driver *driver)
 }
 EXPORT_SYMBOL_GPL(unregister_virtio_driver);
 
+/**
+ * register_virtio_device - register virtio device
+ * @dev        : virtio device to be registered
+ *
+ * On error, the caller must call put_device on &@dev->dev (and not kfree),
+ * as another code path may have obtained a reference to @dev.
+ *
+ * Returns: 0 on suceess, -error on failure
+ */
 int register_virtio_device(struct virtio_device *dev)
 {
 	int err;
 
 	dev->dev.bus = &virtio_bus;
+	device_initialize(&dev->dev);
 
 	/* Assign a unique device index and hence name. */
 	err = ida_simple_get(&virtio_index_ida, 0, 0, GFP_KERNEL);
@@ -330,9 +340,11 @@ int register_virtio_device(struct virtio_device *dev)
 
 	INIT_LIST_HEAD(&dev->vqs);
 
-	/* device_register() causes the bus infrastructure to look for a
-	 * matching driver. */
-	err = device_register(&dev->dev);
+	/*
+	 * device_add() causes the bus infrastructure to look for a matching
+	 * driver.
+	 */
+	err = device_add(&dev->dev);
 	if (err)
 		ida_simple_remove(&virtio_index_ida, dev->index);
 out: