1 files changed, 70 insertions, 14 deletions

diff --git a/include/media/v4l2-event.h b/include/media/v4l2-event.h
index 3b86177..5f14e88 100644
--- a/include/media/v4l2-event.h
+++ b/include/media/v4l2-event.h
@@ -29,39 +29,95 @@
 #include <linux/videodev2.h>
 #include <linux/wait.h>
 
+/*
+ * Overview:
+ *
+ * Events are subscribed per-filehandle. An event specification consists of a
+ * type and is optionally associated with an object identified through the
+ * 'id' field. So an event is uniquely identified by the (type, id) tuple.
+ *
+ * The v4l2-fh struct has a list of subscribed events. The v4l2_subscribed_event
+ * struct is added to that list, one for every subscribed event.
+ *
+ * Each v4l2_subscribed_event struct ends with an array of v4l2_kevent structs.
+ * This array (ringbuffer, really) is used to store any events raised by the
+ * driver. The v4l2_kevent struct links into the 'available' list of the
+ * v4l2_fh struct so VIDIOC_DQEVENT will know which event to dequeue first.
+ *
+ * Finally, if the event subscription is associated with a particular object
+ * such as a V4L2 control, then that object needs to know about that as well
+ * so that an event can be raised by that object. So the 'node' field can
+ * be used to link the v4l2_subscribed_event struct into a list of that
+ * object.
+ *
+ * So to summarize:
+ *
+ * struct v4l2_fh has two lists: one of the subscribed events, and one of the
+ * pending events.
+ *
+ * struct v4l2_subscribed_event has a ringbuffer of raised (pending) events of
+ * that particular type.
+ *
+ * If struct v4l2_subscribed_event is associated with a specific object, then
+ * that object will have an internal list of struct v4l2_subscribed_event so
+ * it knows who subscribed an event to that object.
+ */
+
 struct v4l2_fh;
+struct v4l2_subscribed_event;
 struct video_device;
 
+/** struct v4l2_kevent - Internal kernel event struct.
+  * @list:	List node for the v4l2_fh->available list.
+  * @sev:	Pointer to parent v4l2_subscribed_event.
+  * @event:	The event itself.
+  */
 struct v4l2_kevent {
 	struct list_head	list;
+	struct v4l2_subscribed_event *sev;
 	struct v4l2_event	event;
 };
 
+/** struct v4l2_subscribed_event - Internal struct representing a subscribed event.
+  * @list:	List node for the v4l2_fh->subscribed list.
+  * @type:	Event type.
+  * @id:	Associated object ID (e.g. control ID). 0 if there isn't any.
+  * @flags:	Copy of v4l2_event_subscription->flags.
+  * @fh:	Filehandle that subscribed to this event.
+  * @node:	List node that hooks into the object's event list (if there is one).
+  * @replace:	Optional callback that can replace event 'old' with event 'new'.
+  * @merge:	Optional callback that can merge event 'old' into event 'new'.
+  * @elems:	The number of elements in the events array.
+  * @first:	The index of the events containing the oldest available event.
+  * @in_use:	The number of queued events.
+  * @events:	An array of @elems events.
+  */
 struct v4l2_subscribed_event {
 	struct list_head	list;
 	u32			type;
+	u32			id;
+	u32			flags;
+	struct v4l2_fh		*fh;
+	struct list_head	node;
+	void			(*replace)(struct v4l2_event *old,
+					   const struct v4l2_event *new);
+	void			(*merge)(const struct v4l2_event *old,
+					 struct v4l2_event *new);
+	unsigned		elems;
+	unsigned		first;
+	unsigned		in_use;
+	struct v4l2_kevent	events[];
 };
 
-struct v4l2_events {
-	wait_queue_head_t	wait;
-	struct list_head	subscribed; /* Subscribed events */
-	struct list_head	free; /* Events ready for use */
-	struct list_head	available; /* Dequeueable event */
-	unsigned int		navailable;
-	unsigned int		nallocated; /* Number of allocated events */
-	u32			sequence;
-};
-
-int v4l2_event_init(struct v4l2_fh *fh);
-int v4l2_event_alloc(struct v4l2_fh *fh, unsigned int n);
-void v4l2_event_free(struct v4l2_fh *fh);
 int v4l2_event_dequeue(struct v4l2_fh *fh, struct v4l2_event *event,
 		       int nonblocking);
 void v4l2_event_queue(struct video_device *vdev, const struct v4l2_event *ev);
+void v4l2_event_queue_fh(struct v4l2_fh *fh, const struct v4l2_event *ev);
 int v4l2_event_pending(struct v4l2_fh *fh);
 int v4l2_event_subscribe(struct v4l2_fh *fh,
-			 struct v4l2_event_subscription *sub);
+			 struct v4l2_event_subscription *sub, unsigned elems);
 int v4l2_event_unsubscribe(struct v4l2_fh *fh,
 			   struct v4l2_event_subscription *sub);
+void v4l2_event_unsubscribe_all(struct v4l2_fh *fh);
 
 #endif /* V4L2_EVENT_H */