include/media/v4l2-event.h

   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
  66 struct v4l2_fh;
  67 struct v4l2_subdev;
  68 struct v4l2_subscribed_event;
  69 struct video_device;
  70
  71 /**
  72  * struct v4l2_kevent - Internal kernel event struct.
  73  * @list:       List node for the v4l2_fh->available list.
  74  * @sev:        Pointer to parent v4l2_subscribed_event.
  75  * @event:      The event itself.
  76  */
  77 struct v4l2_kevent {
  78         struct list_head        list;
  79         struct v4l2_subscribed_event *sev;
  80         struct v4l2_event       event;
  81 };
  82
  83 /**
  84  * struct v4l2_subscribed_event_ops - Subscribed event operations.
  85  *
  86  * @add:        Optional callback, called when a new listener is added
  87  * @del:        Optional callback, called when a listener stops listening
  88  * @replace:    Optional callback that can replace event 'old' with event 'new'.
  89  * @merge:      Optional callback that can merge event 'old' into event 'new'.
  90  */
  91 struct v4l2_subscribed_event_ops {
  92         int  (*add)(struct v4l2_subscribed_event *sev, unsigned int elems);
  93         void (*del)(struct v4l2_subscribed_event *sev);
  94         void (*replace)(struct v4l2_event *old, const struct v4l2_event *new);
  95         void (*merge)(const struct v4l2_event *old, struct v4l2_event *new);
  96 };
  97
  98 /**
  99  * struct v4l2_subscribed_event - Internal struct representing a subscribed
 100  *              event.
 101  *
 102  * @list:       List node for the v4l2_fh->subscribed list.
 103  * @type:       Event type.
 104  * @id: Associated object ID (e.g. control ID). 0 if there isn't any.
 105  * @flags:      Copy of v4l2_event_subscription->flags.
 106  * @fh: Filehandle that subscribed to this event.
 107  * @node:       List node that hooks into the object's event list
 108  *              (if there is one).
 109  * @ops:        v4l2_subscribed_event_ops
 110  * @elems:      The number of elements in the events array.
 111  * @first:      The index of the events containing the oldest available event.
 112  * @in_use:     The number of queued events.
 113  * @events:     An array of @elems events.
 114  */
 115 struct v4l2_subscribed_event {
 116         struct list_head        list;
 117         u32                     type;
 118         u32                     id;
 119         u32                     flags;
 120         struct v4l2_fh          *fh;
 121         struct list_head        node;
 122         const struct v4l2_subscribed_event_ops *ops;
 123         unsigned int            elems;
 124         unsigned int            first;
 125         unsigned int            in_use;
 126         struct v4l2_kevent      events[];
 127 };
 128
 129 /**
 130  * v4l2_event_dequeue - Dequeue events from video device.
 131  *
 132  * @fh: pointer to struct v4l2_fh
 133  * @event: pointer to struct v4l2_event
 134  * @nonblocking: if not zero, waits for an event to arrive
 135  */
 136 int v4l2_event_dequeue(struct v4l2_fh *fh, struct v4l2_event *event,
 137                        int nonblocking);
 138
 139 /**
 140  * v4l2_event_queue - Queue events to video device.
 141  *
 142  * @vdev: pointer to &struct video_device
 143  * @ev: pointer to &struct v4l2_event
 144  *
 145  * The event will be queued for all &struct v4l2_fh file handlers.
 146  *
 147  * .. note::
 148  *    The driver's only responsibility is to fill in the type and the data
 149  *    fields.The other fields will be filled in by  V4L2.
 150  */
 151 void v4l2_event_queue(struct video_device *vdev, const struct v4l2_event *ev);
 152
 153 /**
 154  * v4l2_event_queue_fh - Queue events to video device.
 155  *
 156  * @fh: pointer to &struct v4l2_fh
 157  * @ev: pointer to &struct v4l2_event
 158  *
 159  *
 160  * The event will be queued only for the specified &struct v4l2_fh file handler.
 161  *
 162  * .. note::
 163  *    The driver's only responsibility is to fill in the type and the data
 164  *    fields.The other fields will be filled in by  V4L2.
 165  */
 166 void v4l2_event_queue_fh(struct v4l2_fh *fh, const struct v4l2_event *ev);
 167
 168 /**
 169  * v4l2_event_pending - Check if an event is available
 170  *
 171  * @fh: pointer to &struct v4l2_fh
 172  *
 173  * Returns the number of pending events.
 174  */
 175 int v4l2_event_pending(struct v4l2_fh *fh);
 176
 177 /**
 178  * v4l2_event_subscribe - Subscribes to an event
 179  *
 180  * @fh: pointer to &struct v4l2_fh
 181  * @sub: pointer to &struct v4l2_event_subscription
 182  * @elems: size of the events queue
 183  * @ops: pointer to &v4l2_subscribed_event_ops
 184  *
 185  * .. note::
 186  *
 187  *    if @elems is zero, the framework will fill in a default value,
 188  *    with is currently 1 element.
 189  */
 190 int v4l2_event_subscribe(struct v4l2_fh *fh,
 191                          const struct v4l2_event_subscription *sub,
 192                          unsigned int elems,
 193                          const struct v4l2_subscribed_event_ops *ops);
 194 /**
 195  * v4l2_event_unsubscribe - Unsubscribes to an event
 196  *
 197  * @fh: pointer to &struct v4l2_fh
 198  * @sub: pointer to &struct v4l2_event_subscription
 199  */
 200 int v4l2_event_unsubscribe(struct v4l2_fh *fh,
 201                            const struct v4l2_event_subscription *sub);
 202 /**
 203  * v4l2_event_unsubscribe_all - Unsubscribes to all events
 204  *
 205  * @fh: pointer to &struct v4l2_fh
 206  */
 207 void v4l2_event_unsubscribe_all(struct v4l2_fh *fh);
 208
 209 /**
 210  * v4l2_event_subdev_unsubscribe - Subdev variant of v4l2_event_unsubscribe()
 211  *
 212  * @sd: pointer to &struct v4l2_subdev
 213  * @fh: pointer to &struct v4l2_fh
 214  * @sub: pointer to &struct v4l2_event_subscription
 215  *
 216  * .. note::
 217  *
 218  *      This function should be used for the &struct v4l2_subdev_core_ops
 219  *      %unsubscribe_event field.
 220  */
 221 int v4l2_event_subdev_unsubscribe(struct v4l2_subdev *sd,
 222                                   struct v4l2_fh *fh,
 223                                   struct v4l2_event_subscription *sub);
 224 /**
 225  * v4l2_src_change_event_subscribe - helper function that calls
 226  *      v4l2_event_subscribe() if the event is %V4L2_EVENT_SOURCE_CHANGE.
 227  *
 228  * @fh: pointer to struct v4l2_fh
 229  * @sub: pointer to &struct v4l2_event_subscription
 230  */
 231 int v4l2_src_change_event_subscribe(struct v4l2_fh *fh,
 232                                     const struct v4l2_event_subscription *sub);
 233 /**
 234  * v4l2_src_change_event_subdev_subscribe - Variant of v4l2_event_subscribe(),
 235  *      meant to subscribe only events of the type %V4L2_EVENT_SOURCE_CHANGE.
 236  *
 237  * @sd: pointer to &struct v4l2_subdev
 238  * @fh: pointer to &struct v4l2_fh
 239  * @sub: pointer to &struct v4l2_event_subscription
 240  */
 241 int v4l2_src_change_event_subdev_subscribe(struct v4l2_subdev *sd,
 242                                            struct v4l2_fh *fh,
 243                                            struct v4l2_event_subscription *sub);
 244 #endif /* V4L2_EVENT_H */