3ad57c3384
It's getting confusing who is linking to what, so add an overview at the start of the header. Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
124 lines
4.4 KiB
C
124 lines
4.4 KiB
C
/*
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* v4l2-event.h
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*
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* V4L2 events.
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*
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* Copyright (C) 2009--2010 Nokia Corporation.
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*
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* Contact: Sakari Ailus <sakari.ailus@maxwell.research.nokia.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* version 2 as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
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* 02110-1301 USA
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*/
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#ifndef V4L2_EVENT_H
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#define V4L2_EVENT_H
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#include <linux/types.h>
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#include <linux/videodev2.h>
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#include <linux/wait.h>
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/*
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* Overview:
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*
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* Events are subscribed per-filehandle. An event specification consists of a
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* type and is optionally associated with an object identified through the
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* 'id' field. So an event is uniquely identified by the (type, id) tuple.
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*
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* The v4l2-fh struct has a list of subscribed events. The v4l2_subscribed_event
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* struct is added to that list, one for every subscribed event.
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*
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* Each v4l2_subscribed_event struct ends with an array of v4l2_kevent structs.
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* This array (ringbuffer, really) is used to store any events raised by the
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* driver. The v4l2_kevent struct links into the 'available' list of the
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* v4l2_fh struct so VIDIOC_DQEVENT will know which event to dequeue first.
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*
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* Finally, if the event subscription is associated with a particular object
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* such as a V4L2 control, then that object needs to know about that as well
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* so that an event can be raised by that object. So the 'node' field can
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* be used to link the v4l2_subscribed_event struct into a list of that
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* object.
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*
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* So to summarize:
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*
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* struct v4l2_fh has two lists: one of the subscribed events, and one of the
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* pending events.
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*
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* struct v4l2_subscribed_event has a ringbuffer of raised (pending) events of
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* that particular type.
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*
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* If struct v4l2_subscribed_event is associated with a specific object, then
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* that object will have an internal list of struct v4l2_subscribed_event so
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* it knows who subscribed an event to that object.
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*/
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struct v4l2_fh;
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struct v4l2_subscribed_event;
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struct video_device;
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/** struct v4l2_kevent - Internal kernel event struct.
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* @list: List node for the v4l2_fh->available list.
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* @sev: Pointer to parent v4l2_subscribed_event.
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* @event: The event itself.
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*/
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struct v4l2_kevent {
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struct list_head list;
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struct v4l2_subscribed_event *sev;
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struct v4l2_event event;
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};
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/** struct v4l2_subscribed_event - Internal struct representing a subscribed event.
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* @list: List node for the v4l2_fh->subscribed list.
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* @type: Event type.
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* @id: Associated object ID (e.g. control ID). 0 if there isn't any.
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* @flags: Copy of v4l2_event_subscription->flags.
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* @fh: Filehandle that subscribed to this event.
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* @node: List node that hooks into the object's event list (if there is one).
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* @replace: Optional callback that can replace event 'old' with event 'new'.
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* @merge: Optional callback that can merge event 'old' into event 'new'.
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* @elems: The number of elements in the events array.
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* @first: The index of the events containing the oldest available event.
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* @in_use: The number of queued events.
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* @events: An array of @elems events.
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*/
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struct v4l2_subscribed_event {
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struct list_head list;
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u32 type;
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u32 id;
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u32 flags;
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struct v4l2_fh *fh;
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struct list_head node;
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void (*replace)(struct v4l2_event *old,
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const struct v4l2_event *new);
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void (*merge)(const struct v4l2_event *old,
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struct v4l2_event *new);
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unsigned elems;
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unsigned first;
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unsigned in_use;
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struct v4l2_kevent events[];
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};
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int v4l2_event_dequeue(struct v4l2_fh *fh, struct v4l2_event *event,
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int nonblocking);
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void v4l2_event_queue(struct video_device *vdev, const struct v4l2_event *ev);
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void v4l2_event_queue_fh(struct v4l2_fh *fh, const struct v4l2_event *ev);
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int v4l2_event_pending(struct v4l2_fh *fh);
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int v4l2_event_subscribe(struct v4l2_fh *fh,
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struct v4l2_event_subscription *sub, unsigned elems);
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int v4l2_event_unsubscribe(struct v4l2_fh *fh,
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struct v4l2_event_subscription *sub);
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void v4l2_event_unsubscribe_all(struct v4l2_fh *fh);
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#endif /* V4L2_EVENT_H */
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