linux/drivers/media/video/v4l2-event.c
Hans Verkuil ee6869afc9 V4L/DVB: v4l2: add core serialization lock
Drivers can optionally set a pointer to a mutex in struct video_device.
The core will use that to lock before calling open, read, write, unlocked_ioctl,
poll, mmap or release.

Updated the documentation as well and ensure that v4l2-event knows about the
lock: it will unlock it before doing a blocking wait on an event and relock it
afterwards.

Ensure that the 'video_is_registered' check is done when the lock is held:
a typical disconnect will take the lock as well before unregistering the
device nodes, so to prevent race conditions the video_is_registered check
should also be done with the lock held.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
2010-10-21 01:06:14 -02:00

299 lines
6.7 KiB
C

/*
* v4l2-event.c
*
* 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
*/
#include <media/v4l2-dev.h>
#include <media/v4l2-fh.h>
#include <media/v4l2-event.h>
#include <linux/sched.h>
#include <linux/slab.h>
int v4l2_event_init(struct v4l2_fh *fh)
{
fh->events = kzalloc(sizeof(*fh->events), GFP_KERNEL);
if (fh->events == NULL)
return -ENOMEM;
init_waitqueue_head(&fh->events->wait);
INIT_LIST_HEAD(&fh->events->free);
INIT_LIST_HEAD(&fh->events->available);
INIT_LIST_HEAD(&fh->events->subscribed);
fh->events->sequence = -1;
return 0;
}
EXPORT_SYMBOL_GPL(v4l2_event_init);
int v4l2_event_alloc(struct v4l2_fh *fh, unsigned int n)
{
struct v4l2_events *events = fh->events;
unsigned long flags;
if (!events) {
WARN_ON(1);
return -ENOMEM;
}
while (events->nallocated < n) {
struct v4l2_kevent *kev;
kev = kzalloc(sizeof(*kev), GFP_KERNEL);
if (kev == NULL)
return -ENOMEM;
spin_lock_irqsave(&fh->vdev->fh_lock, flags);
list_add_tail(&kev->list, &events->free);
events->nallocated++;
spin_unlock_irqrestore(&fh->vdev->fh_lock, flags);
}
return 0;
}
EXPORT_SYMBOL_GPL(v4l2_event_alloc);
#define list_kfree(list, type, member) \
while (!list_empty(list)) { \
type *hi; \
hi = list_first_entry(list, type, member); \
list_del(&hi->member); \
kfree(hi); \
}
void v4l2_event_free(struct v4l2_fh *fh)
{
struct v4l2_events *events = fh->events;
if (!events)
return;
list_kfree(&events->free, struct v4l2_kevent, list);
list_kfree(&events->available, struct v4l2_kevent, list);
list_kfree(&events->subscribed, struct v4l2_subscribed_event, list);
kfree(events);
fh->events = NULL;
}
EXPORT_SYMBOL_GPL(v4l2_event_free);
static int __v4l2_event_dequeue(struct v4l2_fh *fh, struct v4l2_event *event)
{
struct v4l2_events *events = fh->events;
struct v4l2_kevent *kev;
unsigned long flags;
spin_lock_irqsave(&fh->vdev->fh_lock, flags);
if (list_empty(&events->available)) {
spin_unlock_irqrestore(&fh->vdev->fh_lock, flags);
return -ENOENT;
}
WARN_ON(events->navailable == 0);
kev = list_first_entry(&events->available, struct v4l2_kevent, list);
list_move(&kev->list, &events->free);
events->navailable--;
kev->event.pending = events->navailable;
*event = kev->event;
spin_unlock_irqrestore(&fh->vdev->fh_lock, flags);
return 0;
}
int v4l2_event_dequeue(struct v4l2_fh *fh, struct v4l2_event *event,
int nonblocking)
{
struct v4l2_events *events = fh->events;
int ret;
if (nonblocking)
return __v4l2_event_dequeue(fh, event);
/* Release the vdev lock while waiting */
if (fh->vdev->lock)
mutex_unlock(fh->vdev->lock);
do {
ret = wait_event_interruptible(events->wait,
events->navailable != 0);
if (ret < 0)
break;
ret = __v4l2_event_dequeue(fh, event);
} while (ret == -ENOENT);
if (fh->vdev->lock)
mutex_lock(fh->vdev->lock);
return ret;
}
EXPORT_SYMBOL_GPL(v4l2_event_dequeue);
/* Caller must hold fh->event->lock! */
static struct v4l2_subscribed_event *v4l2_event_subscribed(
struct v4l2_fh *fh, u32 type)
{
struct v4l2_events *events = fh->events;
struct v4l2_subscribed_event *sev;
assert_spin_locked(&fh->vdev->fh_lock);
list_for_each_entry(sev, &events->subscribed, list) {
if (sev->type == type)
return sev;
}
return NULL;
}
void v4l2_event_queue(struct video_device *vdev, const struct v4l2_event *ev)
{
struct v4l2_fh *fh;
unsigned long flags;
struct timespec timestamp;
ktime_get_ts(&timestamp);
spin_lock_irqsave(&vdev->fh_lock, flags);
list_for_each_entry(fh, &vdev->fh_list, list) {
struct v4l2_events *events = fh->events;
struct v4l2_kevent *kev;
/* Are we subscribed? */
if (!v4l2_event_subscribed(fh, ev->type))
continue;
/* Increase event sequence number on fh. */
events->sequence++;
/* Do we have any free events? */
if (list_empty(&events->free))
continue;
/* Take one and fill it. */
kev = list_first_entry(&events->free, struct v4l2_kevent, list);
kev->event.type = ev->type;
kev->event.u = ev->u;
kev->event.timestamp = timestamp;
kev->event.sequence = events->sequence;
list_move_tail(&kev->list, &events->available);
events->navailable++;
wake_up_all(&events->wait);
}
spin_unlock_irqrestore(&vdev->fh_lock, flags);
}
EXPORT_SYMBOL_GPL(v4l2_event_queue);
int v4l2_event_pending(struct v4l2_fh *fh)
{
return fh->events->navailable;
}
EXPORT_SYMBOL_GPL(v4l2_event_pending);
int v4l2_event_subscribe(struct v4l2_fh *fh,
struct v4l2_event_subscription *sub)
{
struct v4l2_events *events = fh->events;
struct v4l2_subscribed_event *sev;
unsigned long flags;
if (fh->events == NULL) {
WARN_ON(1);
return -ENOMEM;
}
sev = kmalloc(sizeof(*sev), GFP_KERNEL);
if (!sev)
return -ENOMEM;
spin_lock_irqsave(&fh->vdev->fh_lock, flags);
if (v4l2_event_subscribed(fh, sub->type) == NULL) {
INIT_LIST_HEAD(&sev->list);
sev->type = sub->type;
list_add(&sev->list, &events->subscribed);
sev = NULL;
}
spin_unlock_irqrestore(&fh->vdev->fh_lock, flags);
kfree(sev);
return 0;
}
EXPORT_SYMBOL_GPL(v4l2_event_subscribe);
static void v4l2_event_unsubscribe_all(struct v4l2_fh *fh)
{
struct v4l2_events *events = fh->events;
struct v4l2_subscribed_event *sev;
unsigned long flags;
do {
sev = NULL;
spin_lock_irqsave(&fh->vdev->fh_lock, flags);
if (!list_empty(&events->subscribed)) {
sev = list_first_entry(&events->subscribed,
struct v4l2_subscribed_event, list);
list_del(&sev->list);
}
spin_unlock_irqrestore(&fh->vdev->fh_lock, flags);
kfree(sev);
} while (sev);
}
int v4l2_event_unsubscribe(struct v4l2_fh *fh,
struct v4l2_event_subscription *sub)
{
struct v4l2_subscribed_event *sev;
unsigned long flags;
if (sub->type == V4L2_EVENT_ALL) {
v4l2_event_unsubscribe_all(fh);
return 0;
}
spin_lock_irqsave(&fh->vdev->fh_lock, flags);
sev = v4l2_event_subscribed(fh, sub->type);
if (sev != NULL)
list_del(&sev->list);
spin_unlock_irqrestore(&fh->vdev->fh_lock, flags);
kfree(sev);
return 0;
}
EXPORT_SYMBOL_GPL(v4l2_event_unsubscribe);