V4L/DVB: v4l2: add core serialization lock
Drivers can optionally set a pointer to a mutex in struct video_device.
The core will use that to lock before calling open, read, write, unlocked_ioctl,
poll, mmap or release.
Updated the documentation as well and ensure that v4l2-event knows about the
lock: it will unlock it before doing a blocking wait on an event and relock it
afterwards.
Ensure that the 'video_is_registered' check is done when the lock is held:
a typical disconnect will take the lock as well before unregistering the
device nodes, so to prevent race conditions the video_is_registered check
should also be done with the lock held.
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/include/media/v4l2-dev.h b/include/media/v4l2-dev.h
index ba236ff..15802a0 100644
--- a/include/media/v4l2-dev.h
+++ b/include/media/v4l2-dev.h
@@ -94,6 +94,9 @@
/* ioctl callbacks */
const struct v4l2_ioctl_ops *ioctl_ops;
+
+ /* serialization lock */
+ struct mutex *lock;
};
/* dev to video-device */