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1 | /* |
2 | * v4l2-event.h |
3 | * |
4 | * V4L2 events. |
5 | * |
6 | * Copyright (C) 2009--2010 Nokia Corporation. |
7 | * |
8 | * Contact: Sakari Ailus <sakari.ailus@maxwell.research.nokia.com> |
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 | |
66 | struct v4l2_fh; |
67 | struct v4l2_subscribed_event; |
68 | struct video_device; |
69 | |
70 | /** struct v4l2_kevent - Internal kernel event struct. |
71 | * @list: List node for the v4l2_fh->available list. |
72 | * @sev: Pointer to parent v4l2_subscribed_event. |
73 | * @event: The event itself. |
74 | */ |
75 | struct v4l2_kevent { |
76 | struct list_head list; |
77 | struct v4l2_subscribed_event *sev; |
78 | struct v4l2_event event; |
79 | }; |
80 | |
81 | /** struct v4l2_subscribed_event_ops - Subscribed event operations. |
82 | * @add: Optional callback, called when a new listener is added |
83 | * @del: Optional callback, called when a listener stops listening |
84 | * @replace: Optional callback that can replace event 'old' with event 'new'. |
85 | * @merge: Optional callback that can merge event 'old' into event 'new'. |
86 | */ |
87 | struct v4l2_subscribed_event_ops { |
88 | int (*add)(struct v4l2_subscribed_event *sev, unsigned elems); |
89 | void (*del)(struct v4l2_subscribed_event *sev); |
90 | void (*replace)(struct v4l2_event *old, const struct v4l2_event *new); |
91 | void (*merge)(const struct v4l2_event *old, struct v4l2_event *new); |
92 | }; |
93 | |
94 | /** struct v4l2_subscribed_event - Internal struct representing a subscribed event. |
95 | * @list: List node for the v4l2_fh->subscribed list. |
96 | * @type: Event type. |
97 | * @id: Associated object ID (e.g. control ID). 0 if there isn't any. |
98 | * @flags: Copy of v4l2_event_subscription->flags. |
99 | * @fh: Filehandle that subscribed to this event. |
100 | * @node: List node that hooks into the object's event list (if there is one). |
101 | * @ops: v4l2_subscribed_event_ops |
102 | * @elems: The number of elements in the events array. |
103 | * @first: The index of the events containing the oldest available event. |
104 | * @in_use: The number of queued events. |
105 | * @events: An array of @elems events. |
106 | */ |
107 | struct v4l2_subscribed_event { |
108 | struct list_head list; |
109 | u32 type; |
110 | u32 id; |
111 | u32 flags; |
112 | struct v4l2_fh *fh; |
113 | struct list_head node; |
114 | const struct v4l2_subscribed_event_ops *ops; |
115 | unsigned elems; |
116 | unsigned first; |
117 | unsigned in_use; |
118 | struct v4l2_kevent events[]; |
119 | }; |
120 | |
121 | int v4l2_event_dequeue(struct v4l2_fh *fh, struct v4l2_event *event, |
122 | int nonblocking); |
123 | void v4l2_event_queue(struct video_device *vdev, const struct v4l2_event *ev); |
124 | void v4l2_event_queue_fh(struct v4l2_fh *fh, const struct v4l2_event *ev); |
125 | int v4l2_event_pending(struct v4l2_fh *fh); |
126 | int v4l2_event_subscribe(struct v4l2_fh *fh, |
127 | struct v4l2_event_subscription *sub, unsigned elems, |
128 | const struct v4l2_subscribed_event_ops *ops); |
129 | int v4l2_event_unsubscribe(struct v4l2_fh *fh, |
130 | struct v4l2_event_subscription *sub); |
131 | void v4l2_event_unsubscribe_all(struct v4l2_fh *fh); |
132 | |
133 | #endif /* V4L2_EVENT_H */ |
134 |
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