v4l2-event.c

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/*
 * v4l2-event.c
 *
 * V4L2 events.
 *
 * Copyright (C) 2009--2010 Nokia Corporation.
 *
 * Contact: Sakari Ailus <[email protected]>
 *
 * 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>
#include <linux/export.h>

static unsigned sev_pos(const struct v4l2_subscribed_event *sev, unsigned idx)
{
    idx += sev->first;
    return idx >= sev->elems ? idx - sev->elems : idx;
}

static int __v4l2_event_dequeue(struct v4l2_fh *fh, struct v4l2_event *event)
{
    struct v4l2_kevent *kev;
    unsigned long flags;

    spin_lock_irqsave(&fh->vdev->fh_lock, flags);

    if (list_empty(&fh->available)) {
        spin_unlock_irqrestore(&fh->vdev->fh_lock, flags);
        return -ENOENT;
    }

    WARN_ON(fh->navailable == 0);

    kev = list_first_entry(&fh->available, struct v4l2_kevent, list);
    list_del(&kev->list);
    fh->navailable--;

    kev->event.pending = fh->navailable;
    *event = kev->event;
    kev->sev->first = sev_pos(kev->sev, 1);
    kev->sev->in_use--;

    spin_unlock_irqrestore(&fh->vdev->fh_lock, flags);

    return 0;
}

int v4l2_event_dequeue(struct v4l2_fh *fh, struct v4l2_event *event,
               int nonblocking)
{
    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(fh->wait,
                           fh->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->vdev->fh_lock! */
static struct v4l2_subscribed_event *v4l2_event_subscribed(
        struct v4l2_fh *fh, u32 type, u32 id)
{
    struct v4l2_subscribed_event *sev;

    assert_spin_locked(&fh->vdev->fh_lock);

    list_for_each_entry(sev, &fh->subscribed, list)
        if (sev->type == type && sev->id == id)
            return sev;

    return NULL;
}

static void __v4l2_event_queue_fh(struct v4l2_fh *fh, const struct v4l2_event *ev,
        const struct timespec *ts)
{
    struct v4l2_subscribed_event *sev;
    struct v4l2_kevent *kev;
    bool copy_payload = true;

    /* Are we subscribed? */
    sev = v4l2_event_subscribed(fh, ev->type, ev->id);
    if (sev == NULL)
        return;

    /*
     * If the event has been added to the fh->subscribed list, but its
     * add op has not completed yet elems will be 0, treat this as
     * not being subscribed.
     */
    if (!sev->elems)
        return;

    /* Increase event sequence number on fh. */
    fh->sequence++;

    /* Do we have any free events? */
    if (sev->in_use == sev->elems) {
        /* no, remove the oldest one */
        kev = sev->events + sev_pos(sev, 0);
        list_del(&kev->list);
        sev->in_use--;
        sev->first = sev_pos(sev, 1);
        fh->navailable--;
        if (sev->elems == 1) {
            if (sev->ops && sev->ops->replace) {
                sev->ops->replace(&kev->event, ev);
                copy_payload = false;
            }
        } else if (sev->ops && sev->ops->merge) {
            struct v4l2_kevent *second_oldest =
                sev->events + sev_pos(sev, 0);
            sev->ops->merge(&kev->event, &second_oldest->event);
        }
    }

    /* Take one and fill it. */
    kev = sev->events + sev_pos(sev, sev->in_use);
    kev->event.type = ev->type;
    if (copy_payload)
        kev->event.u = ev->u;
    kev->event.id = ev->id;
    kev->event.timestamp = *ts;
    kev->event.sequence = fh->sequence;
    sev->in_use++;
    list_add_tail(&kev->list, &fh->available);

    fh->navailable++;

    wake_up_all(&fh->wait);
}

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)
        __v4l2_event_queue_fh(fh, ev, &timestamp);

    spin_unlock_irqrestore(&vdev->fh_lock, flags);
}
EXPORT_SYMBOL_GPL(v4l2_event_queue);

void v4l2_event_queue_fh(struct v4l2_fh *fh, const struct v4l2_event *ev)
{
    unsigned long flags;
    struct timespec timestamp;

    ktime_get_ts(&timestamp);

    spin_lock_irqsave(&fh->vdev->fh_lock, flags);
    __v4l2_event_queue_fh(fh, ev, &timestamp);
    spin_unlock_irqrestore(&fh->vdev->fh_lock, flags);
}
EXPORT_SYMBOL_GPL(v4l2_event_queue_fh);

int v4l2_event_pending(struct v4l2_fh *fh)
{
    return fh->navailable;
}
EXPORT_SYMBOL_GPL(v4l2_event_pending);

int v4l2_event_subscribe(struct v4l2_fh *fh,
             const struct v4l2_event_subscription *sub, unsigned elems,
             const struct v4l2_subscribed_event_ops *ops)
{
    struct v4l2_subscribed_event *sev, *found_ev;
    unsigned long flags;
    unsigned i;

    if (sub->type == V4L2_EVENT_ALL)
        return -EINVAL;

    if (elems < 1)
        elems = 1;

    sev = kzalloc(sizeof(*sev) + sizeof(struct v4l2_kevent) * elems, GFP_KERNEL);
    if (!sev)
        return -ENOMEM;
    for (i = 0; i < elems; i++)
        sev->events[i].sev = sev;
    sev->type = sub->type;
    sev->id = sub->id;
    sev->flags = sub->flags;
    sev->fh = fh;
    sev->ops = ops;

    spin_lock_irqsave(&fh->vdev->fh_lock, flags);
    found_ev = v4l2_event_subscribed(fh, sub->type, sub->id);
    if (!found_ev)
        list_add(&sev->list, &fh->subscribed);
    spin_unlock_irqrestore(&fh->vdev->fh_lock, flags);

    if (found_ev) {
        kfree(sev);
        return 0; /* Already listening */
    }

    if (sev->ops && sev->ops->add) {
        int ret = sev->ops->add(sev, elems);
        if (ret) {
            sev->ops = NULL;
            v4l2_event_unsubscribe(fh, sub);
            return ret;
        }
    }

    /* Mark as ready for use */
    sev->elems = elems;

    return 0;
}
EXPORT_SYMBOL_GPL(v4l2_event_subscribe);

void v4l2_event_unsubscribe_all(struct v4l2_fh *fh)
{
    struct v4l2_event_subscription sub;
    struct v4l2_subscribed_event *sev;
    unsigned long flags;

    do {
        sev = NULL;

        spin_lock_irqsave(&fh->vdev->fh_lock, flags);
        if (!list_empty(&fh->subscribed)) {
            sev = list_first_entry(&fh->subscribed,
                    struct v4l2_subscribed_event, list);
            sub.type = sev->type;
            sub.id = sev->id;
        }
        spin_unlock_irqrestore(&fh->vdev->fh_lock, flags);
        if (sev)
            v4l2_event_unsubscribe(fh, &sub);
    } while (sev);
}
EXPORT_SYMBOL_GPL(v4l2_event_unsubscribe_all);

int v4l2_event_unsubscribe(struct v4l2_fh *fh,
               const struct v4l2_event_subscription *sub)
{
    struct v4l2_subscribed_event *sev;
    unsigned long flags;
    int i;

    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, sub->id);
    if (sev != NULL) {
        /* Remove any pending events for this subscription */
        for (i = 0; i < sev->in_use; i++) {
            list_del(&sev->events[sev_pos(sev, i)].list);
            fh->navailable--;
        }
        list_del(&sev->list);
    }

    spin_unlock_irqrestore(&fh->vdev->fh_lock, flags);

    if (sev && sev->ops && sev->ops->del)
        sev->ops->del(sev);

    kfree(sev);

    return 0;
}
EXPORT_SYMBOL_GPL(v4l2_event_unsubscribe);