1/*
2 * v4l2-event.h
3 *
4 * V4L2 events.
5 *
6 * Copyright (C) 2009--2010 Nokia Corporation.
7 *
8 * Contact: Sakari Ailus <sakari.ailus@iki.fi>
9 *
10 * This program is free software; you can redistribute it and/or
11 * modify it under the terms of the GNU General Public License
12 * version 2 as published by the Free Software Foundation.
13 *
14 * This program is distributed in the hope that it will be useful, but
15 * WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
17 * General Public License for more details.
18 *
19 * You should have received a copy of the GNU General Public License
20 * along with this program; if not, write to the Free Software
21 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
22 * 02110-1301 USA
23 */
24
25#ifndef V4L2_EVENT_H
26#define V4L2_EVENT_H
27
28#include <linux/types.h>
29#include <linux/videodev2.h>
30#include <linux/wait.h>
31
32/*
33 * Overview:
34 *
35 * Events are subscribed per-filehandle. An event specification consists of a
36 * type and is optionally associated with an object identified through the
37 * 'id' field. So an event is uniquely identified by the (type, id) tuple.
38 *
39 * The v4l2-fh struct has a list of subscribed events. The v4l2_subscribed_event
40 * struct is added to that list, one for every subscribed event.
41 *
42 * Each v4l2_subscribed_event struct ends with an array of v4l2_kevent structs.
43 * This array (ringbuffer, really) is used to store any events raised by the
44 * driver. The v4l2_kevent struct links into the 'available' list of the
45 * v4l2_fh struct so VIDIOC_DQEVENT will know which event to dequeue first.
46 *
47 * Finally, if the event subscription is associated with a particular object
48 * such as a V4L2 control, then that object needs to know about that as well
49 * so that an event can be raised by that object. So the 'node' field can
50 * be used to link the v4l2_subscribed_event struct into a list of that
51 * object.
52 *
53 * So to summarize:
54 *
55 * struct v4l2_fh has two lists: one of the subscribed events, and one of the
56 * pending events.
57 *
58 * struct v4l2_subscribed_event has a ringbuffer of raised (pending) events of
59 * that particular type.
60 *
61 * If struct v4l2_subscribed_event is associated with a specific object, then
62 * that object will have an internal list of struct v4l2_subscribed_event so
63 * it knows who subscribed an event to that object.
64 */
65
66struct v4l2_fh;
67struct v4l2_subdev;
68struct v4l2_subscribed_event;
69struct video_device;
70
71/** struct v4l2_kevent - Internal kernel event struct.
72  * @list:	List node for the v4l2_fh->available list.
73  * @sev:	Pointer to parent v4l2_subscribed_event.
74  * @event:	The event itself.
75  */
76struct v4l2_kevent {
77	struct list_head	list;
78	struct v4l2_subscribed_event *sev;
79	struct v4l2_event	event;
80};
81
82/** struct v4l2_subscribed_event_ops - Subscribed event operations.
83  * @add:	Optional callback, called when a new listener is added
84  * @del:	Optional callback, called when a listener stops listening
85  * @replace:	Optional callback that can replace event 'old' with event 'new'.
86  * @merge:	Optional callback that can merge event 'old' into event 'new'.
87  */
88struct v4l2_subscribed_event_ops {
89	int  (*add)(struct v4l2_subscribed_event *sev, unsigned elems);
90	void (*del)(struct v4l2_subscribed_event *sev);
91	void (*replace)(struct v4l2_event *old, const struct v4l2_event *new);
92	void (*merge)(const struct v4l2_event *old, struct v4l2_event *new);
93};
94
95/** struct v4l2_subscribed_event - Internal struct representing a subscribed event.
96  * @list:	List node for the v4l2_fh->subscribed list.
97  * @type:	Event type.
98  * @id:	Associated object ID (e.g. control ID). 0 if there isn't any.
99  * @flags:	Copy of v4l2_event_subscription->flags.
100  * @fh:	Filehandle that subscribed to this event.
101  * @node:	List node that hooks into the object's event list (if there is one).
102  * @ops:	v4l2_subscribed_event_ops
103  * @elems:	The number of elements in the events array.
104  * @first:	The index of the events containing the oldest available event.
105  * @in_use:	The number of queued events.
106  * @events:	An array of @elems events.
107  */
108struct v4l2_subscribed_event {
109	struct list_head	list;
110	u32			type;
111	u32			id;
112	u32			flags;
113	struct v4l2_fh		*fh;
114	struct list_head	node;
115	const struct v4l2_subscribed_event_ops *ops;
116	unsigned		elems;
117	unsigned		first;
118	unsigned		in_use;
119	struct v4l2_kevent	events[];
120};
121
122int v4l2_event_dequeue(struct v4l2_fh *fh, struct v4l2_event *event,
123		       int nonblocking);
124void v4l2_event_queue(struct video_device *vdev, const struct v4l2_event *ev);
125void v4l2_event_queue_fh(struct v4l2_fh *fh, const struct v4l2_event *ev);
126int v4l2_event_pending(struct v4l2_fh *fh);
127int v4l2_event_subscribe(struct v4l2_fh *fh,
128			 const struct v4l2_event_subscription *sub, unsigned elems,
129			 const struct v4l2_subscribed_event_ops *ops);
130int v4l2_event_unsubscribe(struct v4l2_fh *fh,
131			   const struct v4l2_event_subscription *sub);
132void v4l2_event_unsubscribe_all(struct v4l2_fh *fh);
133int v4l2_event_subdev_unsubscribe(struct v4l2_subdev *sd, struct v4l2_fh *fh,
134				  struct v4l2_event_subscription *sub);
135int v4l2_src_change_event_subscribe(struct v4l2_fh *fh,
136				const struct v4l2_event_subscription *sub);
137int v4l2_src_change_event_subdev_subscribe(struct v4l2_subdev *sd,
138		struct v4l2_fh *fh, struct v4l2_event_subscription *sub);
139#endif /* V4L2_EVENT_H */
140