media: v4l: subdev: Set sd->devnode before registering the subdev

The subdev's video device node was only assigned after registering the
device node in the system. While it is unlikely that a driver needed to
use this field in handling system calls to its file handle, there remains
a slim chance the devnode field remains NULL while the driver expects to
find a video node there.

Assign the devnode field before registering the device, and assign it back
to NULL if the registration failed.
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/v4l2-core/v4l2-device.c

@@ -218,13 +218,14 @@ int __v4l2_device_register_subdev_nodes(struct v4l2_device *v4l2_dev,
 		vdev->ctrl_handler = sd->ctrl_handler;
 		if (read_only)
 			set_bit(V4L2_FL_SUBDEV_RO_DEVNODE, &vdev->flags);
+		sd->devnode = vdev;
 		err = __video_register_device(vdev, VFL_TYPE_SUBDEV, -1, 1,
 					      sd->owner);
 		if (err < 0) {
+			sd->devnode = NULL;
 			kfree(vdev);
 			goto clean_up;
 		}
-		sd->devnode = vdev;
 #if defined(CONFIG_MEDIA_CONTROLLER)
 		sd->entity.info.dev.major = VIDEO_MAJOR;
 		sd->entity.info.dev.minor = vdev->minor;