V4L/DVB: v4l2-dev: after a disconnect any ioctl call will be blocked

Until now all fops except release and (unlocked_)ioctl returned an error
after the device node was unregistered. Extend this as well to the ioctl
fops. There is nothing useful that an application can do here and it
complicates the driver code unnecessarily.
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Documentation/video4linux/v4l2-framework.txt

@@ -551,9 +551,8 @@ from /dev).
 
 After video_unregister_device() returns no new opens can be done. However,
 in the case of USB devices some application might still have one of these
-device nodes open. So after the unregister all file operations will return
-an error as well, except for the ioctl and unlocked_ioctl file operations:
-those will still be passed on since some buffer ioctls may still be needed.
+device nodes open. So after the unregister all file operations (except
+release, of course) will return an error as well.
 
 When the last user of the video device node exits, then the vdev->release()
 callback is called and you can do the final cleanup there.

drivers/media/video/v4l2-dev.c

@@ -221,8 +221,8 @@ static long v4l2_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 	struct video_device *vdev = video_devdata(filp);
 	int ret;
 
-	/* Allow ioctl to continue even if the device was unregistered.
-	   Things like dequeueing buffers might still be useful. */
+	if (!vdev->fops->ioctl)
+		return -ENOTTY;
 	if (vdev->fops->unlocked_ioctl) {
 		ret = vdev->fops->unlocked_ioctl(filp, cmd, arg);
 	} else if (vdev->fops->ioctl) {