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
  20 #ifndef V4L2_EVENT_H
  21 #define V4L2_EVENT_H
  22
  23 #include <linux/types.h>
  24 #include <linux/videodev2.h>
  25 #include <linux/wait.h>
  26
  27 /*
  28  * Overview:
  29  *
  30  * Events are subscribed per-filehandle. An event specification consists of a
  31  * type and is optionally associated with an object identified through the
  32  * 'id' field. So an event is uniquely identified by the (type, id) tuple.
  33  *
  34  * The v4l2-fh struct has a list of subscribed events. The v4l2_subscribed_event
  35  * struct is added to that list, one for every subscribed event.
  36  *
  37  * Each v4l2_subscribed_event struct ends with an array of v4l2_kevent structs.
  38  * This array (ringbuffer, really) is used to store any events raised by the
  39  * driver. The v4l2_kevent struct links into the 'available' list of the
  40  * v4l2_fh struct so VIDIOC_DQEVENT will know which event to dequeue first.
  41  *
  42  * Finally, if the event subscription is associated with a particular object
  43  * such as a V4L2 control, then that object needs to know about that as well
  44  * so that an event can be raised by that object. So the 'node' field can
  45  * be used to link the v4l2_subscribed_event struct into a list of that
  46  * object.
  47  *
  48  * So to summarize:
  49  *
  50  * struct v4l2_fh has two lists: one of the subscribed events, and one of the
  51  * pending events.
  52  *
  53  * struct v4l2_subscribed_event has a ringbuffer of raised (pending) events of
  54  * that particular type.
  55  *
  56  * If struct v4l2_subscribed_event is associated with a specific object, then
  57  * that object will have an internal list of struct v4l2_subscribed_event so
  58  * it knows who subscribed an event to that object.
  59  */
  60
  61 struct v4l2_fh;
  62 struct v4l2_subdev;
  63 struct v4l2_subscribed_event;
  64 struct video_device;
  65
  66 /**
  67  * struct v4l2_kevent - Internal kernel event struct.
  68  * @list:       List node for the v4l2_fh->available list.
  69  * @sev:        Pointer to parent v4l2_subscribed_event.
  70  * @event:      The event itself.
  71  */
  72 struct v4l2_kevent {
  73         struct list_head        list;
  74         struct v4l2_subscribed_event *sev;
  75         struct v4l2_event       event;
  76 };
  77
  78 /**
  79  * struct v4l2_subscribed_event_ops - Subscribed event operations.
  80  *
  81  * @add:        Optional callback, called when a new listener is added
  82  * @del:        Optional callback, called when a listener stops listening
  83  * @replace:    Optional callback that can replace event 'old' with event 'new'.
  84  * @merge:      Optional callback that can merge event 'old' into event 'new'.
  85  */
  86 struct v4l2_subscribed_event_ops {
  87         int  (*add)(struct v4l2_subscribed_event *sev, unsigned int elems);
  88         void (*del)(struct v4l2_subscribed_event *sev);
  89         void (*replace)(struct v4l2_event *old, const struct v4l2_event *new);
  90         void (*merge)(const struct v4l2_event *old, struct v4l2_event *new);
  91 };
  92
  93 /**
  94  * struct v4l2_subscribed_event - Internal struct representing a subscribed
  95  *              event.
  96  *
  97  * @list:       List node for the v4l2_fh->subscribed list.
  98  * @type:       Event type.
  99  * @id: Associated object ID (e.g. control ID). 0 if there isn't any.
 100  * @flags:      Copy of v4l2_event_subscription->flags.
 101  * @fh: Filehandle that subscribed to this event.
 102  * @node:       List node that hooks into the object's event list
 103  *              (if there is one).
 104  * @ops:        v4l2_subscribed_event_ops
 105  * @elems:      The number of elements in the events array.
 106  * @first:      The index of the events containing the oldest available event.
 107  * @in_use:     The number of queued events.
 108  * @events:     An array of @elems events.
 109  */
 110 struct v4l2_subscribed_event {
 111         struct list_head        list;
 112         u32                     type;
 113         u32                     id;
 114         u32                     flags;
 115         struct v4l2_fh          *fh;
 116         struct list_head        node;
 117         const struct v4l2_subscribed_event_ops *ops;
 118         unsigned int            elems;
 119         unsigned int            first;
 120         unsigned int            in_use;
 121         struct v4l2_kevent      events[];
 122 };
 123
 124 /**
 125  * v4l2_event_dequeue - Dequeue events from video device.
 126  *
 127  * @fh: pointer to struct v4l2_fh
 128  * @event: pointer to struct v4l2_event
 129  * @nonblocking: if not zero, waits for an event to arrive
 130  */
 131 int v4l2_event_dequeue(struct v4l2_fh *fh, struct v4l2_event *event,
 132                        int nonblocking);
 133
 134 /**
 135  * v4l2_event_queue - Queue events to video device.
 136  *
 137  * @vdev: pointer to &struct video_device
 138  * @ev: pointer to &struct v4l2_event
 139  *
 140  * The event will be queued for all &struct v4l2_fh file handlers.
 141  *
 142  * .. note::
 143  *    The driver's only responsibility is to fill in the type and the data
 144  *    fields.The other fields will be filled in by  V4L2.
 145  */
 146 void v4l2_event_queue(struct video_device *vdev, const struct v4l2_event *ev);
 147
 148 /**
 149  * v4l2_event_queue_fh - Queue events to video device.
 150  *
 151  * @fh: pointer to &struct v4l2_fh
 152  * @ev: pointer to &struct v4l2_event
 153  *
 154  *
 155  * The event will be queued only for the specified &struct v4l2_fh file handler.
 156  *
 157  * .. note::
 158  *    The driver's only responsibility is to fill in the type and the data
 159  *    fields.The other fields will be filled in by  V4L2.
 160  */
 161 void v4l2_event_queue_fh(struct v4l2_fh *fh, const struct v4l2_event *ev);
 162
 163 /**
 164  * v4l2_event_pending - Check if an event is available
 165  *
 166  * @fh: pointer to &struct v4l2_fh
 167  *
 168  * Returns the number of pending events.
 169  */
 170 int v4l2_event_pending(struct v4l2_fh *fh);
 171
 172 /**
 173  * v4l2_event_subscribe - Subscribes to an event
 174  *
 175  * @fh: pointer to &struct v4l2_fh
 176  * @sub: pointer to &struct v4l2_event_subscription
 177  * @elems: size of the events queue
 178  * @ops: pointer to &v4l2_subscribed_event_ops
 179  *
 180  * .. note::
 181  *
 182  *    if @elems is zero, the framework will fill in a default value,
 183  *    with is currently 1 element.
 184  */
 185 int v4l2_event_subscribe(struct v4l2_fh *fh,
 186                          const struct v4l2_event_subscription *sub,
 187                          unsigned int elems,
 188                          const struct v4l2_subscribed_event_ops *ops);
 189 /**
 190  * v4l2_event_unsubscribe - Unsubscribes to an event
 191  *
 192  * @fh: pointer to &struct v4l2_fh
 193  * @sub: pointer to &struct v4l2_event_subscription
 194  */
 195 int v4l2_event_unsubscribe(struct v4l2_fh *fh,
 196                            const struct v4l2_event_subscription *sub);
 197 /**
 198  * v4l2_event_unsubscribe_all - Unsubscribes to all events
 199  *
 200  * @fh: pointer to &struct v4l2_fh
 201  */
 202 void v4l2_event_unsubscribe_all(struct v4l2_fh *fh);
 203
 204 /**
 205  * v4l2_event_subdev_unsubscribe - Subdev variant of v4l2_event_unsubscribe()
 206  *
 207  * @sd: pointer to &struct v4l2_subdev
 208  * @fh: pointer to &struct v4l2_fh
 209  * @sub: pointer to &struct v4l2_event_subscription
 210  *
 211  * .. note::
 212  *
 213  *      This function should be used for the &struct v4l2_subdev_core_ops
 214  *      %unsubscribe_event field.
 215  */
 216 int v4l2_event_subdev_unsubscribe(struct v4l2_subdev *sd,
 217                                   struct v4l2_fh *fh,
 218                                   struct v4l2_event_subscription *sub);
 219 /**
 220  * v4l2_src_change_event_subscribe - helper function that calls
 221  *      v4l2_event_subscribe() if the event is %V4L2_EVENT_SOURCE_CHANGE.
 222  *
 223  * @fh: pointer to struct v4l2_fh
 224  * @sub: pointer to &struct v4l2_event_subscription
 225  */
 226 int v4l2_src_change_event_subscribe(struct v4l2_fh *fh,
 227                                     const struct v4l2_event_subscription *sub);
 228 /**
 229  * v4l2_src_change_event_subdev_subscribe - Variant of v4l2_event_subscribe(),
 230  *      meant to subscribe only events of the type %V4L2_EVENT_SOURCE_CHANGE.
 231  *
 232  * @sd: pointer to &struct v4l2_subdev
 233  * @fh: pointer to &struct v4l2_fh
 234  * @sub: pointer to &struct v4l2_event_subscription
 235  */
 236 int v4l2_src_change_event_subdev_subscribe(struct v4l2_subdev *sd,
 237                                            struct v4l2_fh *fh,
 238                                            struct v4l2_event_subscription *sub);
 239 #endif /* V4L2_EVENT_H */