[media] v4l2-ctrls.c: add support for V4L2_EVENT_SUB_FL_ALLOW_FEEDBACK

Normally no control events will go to the filehandle that called the
VIDIOC_S_CTRL/VIDIOC_S_EXT_CTRLS ioctls. This is to prevent a feedback
loop.

This can now be overridden by setting the new V4L2_EVENT_SUB_FL_ALLOW_FEEDBACK
flag.

Based on suggestions from Mauro Carvalho Chehab <mchehab@redhat.com> and
Laurent Pinchart <laurent.pinchart@ideasonboard.com>.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/include/linux/videodev2.h b/include/linux/videodev2.h
index baafe2f2e02a..2c4e83796301 100644
--- a/include/linux/videodev2.h
+++ b/include/linux/videodev2.h
@@ -1832,7 +1832,8 @@ struct v4l2_event {
         __u32                           reserved[8];
 };
 
-#define V4L2_EVENT_SUB_FL_SEND_INITIAL (1 << 0)
+#define V4L2_EVENT_SUB_FL_SEND_INITIAL          (1 << 0)
+#define V4L2_EVENT_SUB_FL_ALLOW_FEEDBACK        (1 << 1)
 
 struct v4l2_event_subscription {
         __u32                           type;