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Diffstat (limited to 'include/media/v4l2-event.h')
| -rw-r--r-- | include/media/v4l2-event.h | 123 |
1 files changed, 123 insertions, 0 deletions
diff --git a/include/media/v4l2-event.h b/include/media/v4l2-event.h new file mode 100644 index 00000000..5f14e889 --- /dev/null +++ b/include/media/v4l2-event.h @@ -0,0 +1,123 @@ +/* + * v4l2-event.h + * + * V4L2 events. + * + * Copyright (C) 2009--2010 Nokia Corporation. + * + * Contact: Sakari Ailus <sakari.ailus@maxwell.research.nokia.com> + * + * 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_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 - 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). + * @replace: Optional callback that can replace event 'old' with event 'new'. + * @merge: Optional callback that can merge event 'old' into event 'new'. + * @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; + void (*replace)(struct v4l2_event *old, + const struct v4l2_event *new); + void (*merge)(const struct v4l2_event *old, + struct v4l2_event *new); + 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, + struct v4l2_event_subscription *sub, unsigned elems); +int v4l2_event_unsubscribe(struct v4l2_fh *fh, + struct v4l2_event_subscription *sub); +void v4l2_event_unsubscribe_all(struct v4l2_fh *fh); + +#endif /* V4L2_EVENT_H */ |