/*
 *      cn_queue.c
 *
 * 2004+ Copyright (c) Evgeniy Polyakov <zbr@ioremap.net>
 * All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/list.h>
#include <linux/workqueue.h>
#include <linux/spinlock.h>
#include <linux/slab.h>
#include <linux/skbuff.h>
#include <linux/suspend.h>
#include <linux/connector.h>
#include <linux/delay.h>


/*
 * This job is sent to the kevent workqueue.
 * While no event is once sent to any callback, the connector workqueue
 * is not created to avoid a useless waiting kernel task.
 * Once the first event is received, we create this dedicated workqueue which
 * is necessary because the flow of data can be high and we don't want
 * to encumber keventd with that.
 */
static void cn_queue_create(struct work_struct *work)
{
        struct cn_queue_dev *dev;

        dev = container_of(work, struct cn_queue_dev, wq_creation);

        dev->cn_queue = create_singlethread_workqueue(dev->name);
        /* If we fail, we will use keventd for all following connector jobs */
        WARN_ON(!dev->cn_queue);
}

/*
 * Queue a data sent to a callback.
 * If the connector workqueue is already created, we queue the job on it.
 * Otherwise, we queue the job to kevent and queue the connector workqueue
 * creation too.
 */
int queue_cn_work(struct cn_callback_entry *cbq, struct work_struct *work)
{
        struct cn_queue_dev *pdev = cbq->pdev;

        if (likely(pdev->cn_queue))
                return queue_work(pdev->cn_queue, work);

        /* Don't create the connector workqueue twice */
        if (atomic_inc_return(&pdev->wq_requested) == 1)
                schedule_work(&pdev->wq_creation);
        else
                atomic_dec(&pdev->wq_requested);

        return schedule_work(work);
}

void cn_queue_wrapper(struct work_struct *work)
{
        struct cn_callback_entry *cbq =
                container_of(work, struct cn_callback_entry, work);
        struct cn_callback_data *d = &cbq->data;
        struct cn_msg *msg = NLMSG_DATA(nlmsg_hdr(d->skb));
        struct netlink_skb_parms *nsp = &NETLINK_CB(d->skb);

        d->callback(msg, nsp);

        kfree_skb(d->skb);
        d->skb = NULL;

        kfree(d->free);
}

static struct cn_callback_entry *
cn_queue_alloc_callback_entry(char *name, struct cb_id *id,
                              void (*callback)(struct cn_msg *, struct netlink_skb_parms *))
{
        struct cn_callback_entry *cbq;

        cbq = kzalloc(sizeof(*cbq), GFP_KERNEL);
        if (!cbq) {
                printk(KERN_ERR "Failed to create new callback queue.\n");
                return NULL;
        }

        snprintf(cbq->id.name, sizeof(cbq->id.name), "%s", name);
        memcpy(&cbq->id.id, id, sizeof(struct cb_id));
        cbq->data.callback = callback;

        INIT_WORK(&cbq->work, &cn_queue_wrapper);
        return cbq;
}

static void cn_queue_free_callback(struct cn_callback_entry *cbq)
{
        /* The first jobs have been sent to kevent, flush them too */
        flush_scheduled_work();
        if (cbq->pdev->cn_queue)
                flush_workqueue(cbq->pdev->cn_queue);

        kfree(cbq);
}

int cn_cb_equal(struct cb_id *i1, struct cb_id *i2)
{
        return ((i1->idx == i2->idx) && (i1->val == i2->val));
}

int cn_queue_add_callback(struct cn_queue_dev *dev, char *name, struct cb_id *id,
                          void (*callback)(struct cn_msg *, struct netlink_skb_parms *))
{
        struct cn_callback_entry *cbq, *__cbq;
        int found = 0;

        cbq = cn_queue_alloc_callback_entry(name, id, callback);
        if (!cbq)
                return -ENOMEM;

        atomic_inc(&dev->refcnt);
        cbq->pdev = dev;

        spin_lock_bh(&dev->queue_lock);
        list_for_each_entry(__cbq, &dev->queue_list, callback_entry) {
                if (cn_cb_equal(&__cbq->id.id, id)) {
                        found = 1;
                        break;
                }
        }
        if (!found)
                list_add_tail(&cbq->callback_entry, &dev->queue_list);
        spin_unlock_bh(&dev->queue_lock);

        if (found) {
                cn_queue_free_callback(cbq);
                atomic_dec(&dev->refcnt);
                return -EINVAL;
        }

        cbq->seq = 0;
        cbq->group = cbq->id.id.idx;

        return 0;
}

void cn_queue_del_callback(struct cn_queue_dev *dev, struct cb_id *id)
{
        struct cn_callback_entry *cbq, *n;
        int found = 0;

        spin_lock_bh(&dev->queue_lock);
        list_for_each_entry_safe(cbq, n, &dev->queue_list, callback_entry) {
                if (cn_cb_equal(&cbq->id.id, id)) {
                        list_del(&cbq->callback_entry);
                        found = 1;
                        break;
                }
        }
        spin_unlock_bh(&dev->queue_lock);

        if (found) {
                cn_queue_free_callback(cbq);
                atomic_dec(&dev->refcnt);
        }
}

struct cn_queue_dev *cn_queue_alloc_dev(char *name, struct sock *nls)
{
        struct cn_queue_dev *dev;

        dev = kzalloc(sizeof(*dev), GFP_KERNEL);
        if (!dev)
                return NULL;

        snprintf(dev->name, sizeof(dev->name), "%s", name);
        atomic_set(&dev->refcnt, 0);
        INIT_LIST_HEAD(&dev->queue_list);
        spin_lock_init(&dev->queue_lock);
        init_waitqueue_head(&dev->wq_created);

        dev->nls = nls;

        INIT_WORK(&dev->wq_creation, cn_queue_create);

        return dev;
}

void cn_queue_free_dev(struct cn_queue_dev *dev)
{
        struct cn_callback_entry *cbq, *n;
        long timeout;
        DEFINE_WAIT(wait);

        /* Flush the first pending jobs queued on kevent */
        flush_scheduled_work();

        /* If the connector workqueue creation is still pending, wait for it */
        prepare_to_wait(&dev->wq_created, &wait, TASK_UNINTERRUPTIBLE);
        if (atomic_read(&dev->wq_requested) && !dev->cn_queue) {
                timeout = schedule_timeout(HZ * 2);
                if (!timeout && !dev->cn_queue)
                        WARN_ON(1);
        }
        finish_wait(&dev->wq_created, &wait);

        if (dev->cn_queue) {
                flush_workqueue(dev->cn_queue);
                destroy_workqueue(dev->cn_queue);
        }

        spin_lock_bh(&dev->queue_lock);
        list_for_each_entry_safe(cbq, n, &dev->queue_list, callback_entry)
                list_del(&cbq->callback_entry);
        spin_unlock_bh(&dev->queue_lock);

        while (atomic_read(&dev->refcnt)) {
                printk(KERN_INFO "Waiting for %s to become free: refcnt=%d.\n",
                       dev->name, atomic_read(&dev->refcnt));
                msleep(1000);
        }

        kfree(dev);
        dev = NULL;
}