Edit File: v4l2-event.h
/* * 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 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 elems; unsigned first; unsigned in_use; struct v4l2_kevent events[]; }; int v4l2_event_dequeue(struct v4l2_fh *fh, struct v4l2_event *event, int nonblocking); void v4l2_event_queue(struct video_device *vdev, const struct v4l2_event *ev); void v4l2_event_queue_fh(struct v4l2_fh *fh, const struct v4l2_event *ev); int v4l2_event_pending(struct v4l2_fh *fh); int v4l2_event_subscribe(struct v4l2_fh *fh, const struct v4l2_event_subscription *sub, unsigned elems, const struct v4l2_subscribed_event_ops *ops); int v4l2_event_unsubscribe(struct v4l2_fh *fh, const struct v4l2_event_subscription *sub); void v4l2_event_unsubscribe_all(struct v4l2_fh *fh); int v4l2_event_subdev_unsubscribe(struct v4l2_subdev *sd, struct v4l2_fh *fh, struct v4l2_event_subscription *sub); #endif /* V4L2_EVENT_H */