/*
 * 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 <media/v4l2-ctrls.h>

#include <linux/sched.h>
#include <linux/slab.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;

        /* 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->replace) {
                                sev->replace(&kev->event, ev);
                                copy_payload = false;
                        }
                } else if (sev->merge) {
                        struct v4l2_kevent *second_oldest =
                                sev->events + sev_pos(sev, 0);
                        sev->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);

static void ctrls_replace(struct v4l2_event *old, const struct v4l2_event *new)
{
        u32 old_changes = old->u.ctrl.changes;

        old->u.ctrl = new->u.ctrl;
        old->u.ctrl.changes |= old_changes;
}

static void ctrls_merge(const struct v4l2_event *old, struct v4l2_event *new)
{
        new->u.ctrl.changes |= old->u.ctrl.changes;
}

int v4l2_event_subscribe(struct v4l2_fh *fh,
                         struct v4l2_event_subscription *sub, unsigned elems)
{
        struct v4l2_subscribed_event *sev, *found_ev;
        struct v4l2_ctrl *ctrl = NULL;
        unsigned long flags;
        unsigned i;

        if (elems < 1)
                elems = 1;
        if (sub->type == V4L2_EVENT_CTRL) {
                ctrl = v4l2_ctrl_find(fh->ctrl_handler, sub->id);
                if (ctrl == NULL)
                        return -EINVAL;
        }

        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->elems = elems;
        if (ctrl) {
                sev->replace = ctrls_replace;
                sev->merge = ctrls_merge;
        }

        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);

        /* v4l2_ctrl_add_event uses a mutex, so do this outside the spin lock */
        if (found_ev)
                kfree(sev);
        else if (ctrl)
                v4l2_ctrl_add_event(ctrl, sev);

        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,
                           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, sub->id);
        if (sev != NULL) {
                list_del(&sev->list);
                sev->fh = NULL;
        }

        spin_unlock_irqrestore(&fh->vdev->fh_lock, flags);
        if (sev && sev->type == V4L2_EVENT_CTRL) {
                struct v4l2_ctrl *ctrl = v4l2_ctrl_find(fh->ctrl_handler, sev->id);

                if (ctrl)
                        v4l2_ctrl_del_event(ctrl, sev);
        }

        kfree(sev);

        return 0;
}
EXPORT_SYMBOL_GPL(v4l2_event_unsubscribe);