media: mc: mark the media devnode as registered from the, start

First the media device node was created, and if successful it was
marked as 'registered'. This leaves a small race condition where
an application can open the device node and get an error back
because the 'registered' flag was not yet set.

Change the order: first set the 'registered' flag, then actually
register the media device node. If that fails, then clear the flag.

Signed-off-by: Hans Verkuil <[e-mail]>
Acked-by: Sakari Ailus <[e-mail]>
Reviewed-by: Laurent Pinchart <[e-mail]>
Fixes: cf4b9211b568 ("[media] media: Media device node support")
Cc: [e-mail]
Signed-off-by: Sakari Ailus <[e-mail]>

drivers/media/mc/mc-devnode.c

···
 	kobject_set_name(&devnode->cdev.kobj, "media%d", devnode->minor);
 
 	/* Part 3: Add the media and char device */
+	set_bit(MEDIA_FLAG_REGISTERED, &devnode->flags);
 	ret = cdev_device_add(&devnode->cdev, &devnode->dev);
 	if (ret < 0) {
+		clear_bit(MEDIA_FLAG_REGISTERED, &devnode->flags);
 		pr_err("%s: cdev_device_add failed\n", __func__);
 		goto cdev_add_error;
 	}
-
-	/* Part 4: Activate this minor. The char device can now be used. */
-	set_bit(MEDIA_FLAG_REGISTERED, &devnode->flags);
 
 	return 0;