/*
   * 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 int 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 int		elems;
  	unsigned int		first;
  	unsigned int		in_use;

  	struct v4l2_kevent	events[];

  };

  /**
   * v4l2_event_dequeue - Dequeue events from video device.
   *
   * @fh: pointer to struct v4l2_fh
   * @event: pointer to struct v4l2_event
   * @nonblocking: if not zero, waits for an event to arrive
   */

  int v4l2_event_dequeue(struct v4l2_fh *fh, struct v4l2_event *event,
  		       int nonblocking);

  
  /**
   * v4l2_event_queue - Queue events to video device.
   *
   * @vdev: pointer to &struct video_device
   * @ev: pointer to &struct v4l2_event
   *
   * The event will be queued for all &struct v4l2_fh file handlers.
   *
   * .. note::
   *    The driver's only responsibility is to fill in the type and the data
   *    fields.The other fields will be filled in by  V4L2.
   */

  void v4l2_event_queue(struct video_device *vdev, const struct v4l2_event *ev);

  
  /**
   * v4l2_event_queue_fh - Queue events to video device.
   *
   * @fh: pointer to &struct v4l2_fh
   * @ev: pointer to &struct v4l2_event
   *
   *
   * The event will be queued only for the specified &struct v4l2_fh file handler.
   *
   * .. note::
   *    The driver's only responsibility is to fill in the type and the data
   *    fields.The other fields will be filled in by  V4L2.
   */

  void v4l2_event_queue_fh(struct v4l2_fh *fh, const struct v4l2_event *ev);

  
  /**
   * v4l2_event_pending - Check if an event is available
   *
   * @fh: pointer to &struct v4l2_fh
   *
   * Returns the number of pending events.
   */

  int v4l2_event_pending(struct v4l2_fh *fh);

  
  /**
   * v4l2_event_subscribe - Subscribes to an event
   *
   * @fh: pointer to &struct v4l2_fh
   * @sub: pointer to &struct v4l2_event_subscription
   * @elems: size of the events queue
   * @ops: pointer to &v4l2_subscribed_event_ops
   *
   * .. note::
   *
   *    if @elems is zero, the framework will fill in a default value,
   *    with is currently 1 element.
   */

  int v4l2_event_subscribe(struct v4l2_fh *fh,

  			 const struct v4l2_event_subscription *sub,
  			 unsigned int elems,

  			 const struct v4l2_subscribed_event_ops *ops);

  /**
   * v4l2_event_unsubscribe - Unsubscribes to an event
   *
   * @fh: pointer to &struct v4l2_fh
   * @sub: pointer to &struct v4l2_event_subscription
   */

  int v4l2_event_unsubscribe(struct v4l2_fh *fh,

  			   const struct v4l2_event_subscription *sub);

  /**
   * v4l2_event_unsubscribe_all - Unsubscribes to all events
   *
   * @fh: pointer to &struct v4l2_fh
   */

  void v4l2_event_unsubscribe_all(struct v4l2_fh *fh);

  
  /**
   * v4l2_event_subdev_unsubscribe - Subdev variant of v4l2_event_unsubscribe()
   *
   * @sd: pointer to &struct v4l2_subdev
   * @fh: pointer to &struct v4l2_fh
   * @sub: pointer to &struct v4l2_event_subscription
   *
   * .. note::
   *
   *	This function should be used for the &struct v4l2_subdev_core_ops
   *	%unsubscribe_event field.
   */
  int v4l2_event_subdev_unsubscribe(struct v4l2_subdev *sd,
  				  struct v4l2_fh *fh,

  				  struct v4l2_event_subscription *sub);

  /**

   * v4l2_src_change_event_subscribe - helper function that calls
   * 	v4l2_event_subscribe() if the event is %V4L2_EVENT_SOURCE_CHANGE.

   *
   * @fh: pointer to struct v4l2_fh
   * @sub: pointer to &struct v4l2_event_subscription
   */

  int v4l2_src_change_event_subscribe(struct v4l2_fh *fh,

  				    const struct v4l2_event_subscription *sub);
  /**
   * v4l2_src_change_event_subdev_subscribe - Variant of v4l2_event_subscribe(),
   *	meant to subscribe only events of the type %V4L2_EVENT_SOURCE_CHANGE.
   *
   * @sd: pointer to &struct v4l2_subdev
   * @fh: pointer to &struct v4l2_fh
   * @sub: pointer to &struct v4l2_event_subscription
   */

  int v4l2_src_change_event_subdev_subscribe(struct v4l2_subdev *sd,

  					   struct v4l2_fh *fh,
  					   struct v4l2_event_subscription *sub);

  #endif /* V4L2_EVENT_H */