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+/*
+ * v4l2-event.h
+ *
+ * V4L2 events.
+ *
+ * Copyright (C) 2009--2010 Nokia Corporation.
+ *
+ * Contact: Sakari Ailus <sakari.ailus@iki.fi>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
+ * 02110-1301 USA
+ */
+
+#ifndef V4L2_EVENT_H
+#define V4L2_EVENT_H
+
+#include <linux/types.h>
+#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_subdev;
+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_ops - Subscribed event operations.
+ * @add: Optional callback, called when a new listener is added
+ * @del: Optional callback, called when a listener stops listening
+ * @replace: Optional callback that can replace event 'old' with event 'new'.
+ * @merge: Optional callback that can merge event 'old' into event 'new'.
+ */
+struct v4l2_subscribed_event_ops {
+ int (*add)(struct v4l2_subscribed_event *sev, unsigned elems);
+ void (*del)(struct v4l2_subscribed_event *sev);
+ void (*replace)(struct v4l2_event *old, const struct v4l2_event *new);
+ void (*merge)(const struct v4l2_event *old, struct v4l2_event *new);
+};
+
+/** 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).
+ * @ops: v4l2_subscribed_event_ops
+ * @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;
+ const struct v4l2_subscribed_event_ops *ops;
+ unsigned elems;
+ unsigned first;
+ unsigned in_use;
+ struct v4l2_kevent events[];
+};
+
+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,
+ const struct v4l2_event_subscription *sub, unsigned elems,
+ const struct v4l2_subscribed_event_ops *ops);
+int v4l2_event_unsubscribe(struct v4l2_fh *fh,
+ const struct v4l2_event_subscription *sub);
+void v4l2_event_unsubscribe_all(struct v4l2_fh *fh);
+int v4l2_event_subdev_unsubscribe(struct v4l2_subdev *sd, struct v4l2_fh *fh,
+ struct v4l2_event_subscription *sub);
+int v4l2_src_change_event_subscribe(struct v4l2_fh *fh,
+ const struct v4l2_event_subscription *sub);
+int v4l2_src_change_event_subdev_subscribe(struct v4l2_subdev *sd,
+ struct v4l2_fh *fh, struct v4l2_event_subscription *sub);
+#endif /* V4L2_EVENT_H */