timerdev.c

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/*
 *
 * general timer device for using in ISDN stacks
 *
 * Author   Karsten Keil <[email protected]>
 *
 * Copyright 2008  by Karsten Keil <[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.
 *
 */

#include <linux/poll.h>
#include <linux/vmalloc.h>
#include <linux/slab.h>
#include <linux/timer.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/mISDNif.h>
#include <linux/mutex.h>
#include "core.h"

static DEFINE_MUTEX(mISDN_mutex);
static u_int    *debug;


struct mISDNtimerdev {
    int         next_id;
    struct list_head    pending;
    struct list_head    expired;
    wait_queue_head_t   wait;
    u_int           work;
    spinlock_t      lock; /* protect lists */
};

struct mISDNtimer {
    struct list_head    list;
    struct  mISDNtimerdev   *dev;
    struct timer_list   tl;
    int         id;
};

static int
mISDN_open(struct inode *ino, struct file *filep)
{
    struct mISDNtimerdev    *dev;

    if (*debug & DEBUG_TIMER)
        printk(KERN_DEBUG "%s(%p,%p)\n", __func__, ino, filep);
    dev = kmalloc(sizeof(struct mISDNtimerdev) , GFP_KERNEL);
    if (!dev)
        return -ENOMEM;
    dev->next_id = 1;
    INIT_LIST_HEAD(&dev->pending);
    INIT_LIST_HEAD(&dev->expired);
    spin_lock_init(&dev->lock);
    dev->work = 0;
    init_waitqueue_head(&dev->wait);
    filep->private_data = dev;
    __module_get(THIS_MODULE);
    return nonseekable_open(ino, filep);
}

static int
mISDN_close(struct inode *ino, struct file *filep)
{
    struct mISDNtimerdev    *dev = filep->private_data;
    struct mISDNtimer   *timer, *next;

    if (*debug & DEBUG_TIMER)
        printk(KERN_DEBUG "%s(%p,%p)\n", __func__, ino, filep);
    list_for_each_entry_safe(timer, next, &dev->pending, list) {
        del_timer(&timer->tl);
        kfree(timer);
    }
    list_for_each_entry_safe(timer, next, &dev->expired, list) {
        kfree(timer);
    }
    kfree(dev);
    module_put(THIS_MODULE);
    return 0;
}

static ssize_t
mISDN_read(struct file *filep, char __user *buf, size_t count, loff_t *off)
{
    struct mISDNtimerdev    *dev = filep->private_data;
    struct mISDNtimer   *timer;
    u_long  flags;
    int ret = 0;

    if (*debug & DEBUG_TIMER)
        printk(KERN_DEBUG "%s(%p, %p, %d, %p)\n", __func__,
               filep, buf, (int)count, off);

    if (list_empty(&dev->expired) && (dev->work == 0)) {
        if (filep->f_flags & O_NONBLOCK)
            return -EAGAIN;
        wait_event_interruptible(dev->wait, (dev->work ||
                             !list_empty(&dev->expired)));
        if (signal_pending(current))
            return -ERESTARTSYS;
    }
    if (count < sizeof(int))
        return -ENOSPC;
    if (dev->work)
        dev->work = 0;
    if (!list_empty(&dev->expired)) {
        spin_lock_irqsave(&dev->lock, flags);
        timer = (struct mISDNtimer *)dev->expired.next;
        list_del(&timer->list);
        spin_unlock_irqrestore(&dev->lock, flags);
        if (put_user(timer->id, (int __user *)buf))
            ret = -EFAULT;
        else
            ret = sizeof(int);
        kfree(timer);
    }
    return ret;
}

static unsigned int
mISDN_poll(struct file *filep, poll_table *wait)
{
    struct mISDNtimerdev    *dev = filep->private_data;
    unsigned int        mask = POLLERR;

    if (*debug & DEBUG_TIMER)
        printk(KERN_DEBUG "%s(%p, %p)\n", __func__, filep, wait);
    if (dev) {
        poll_wait(filep, &dev->wait, wait);
        mask = 0;
        if (dev->work || !list_empty(&dev->expired))
            mask |= (POLLIN | POLLRDNORM);
        if (*debug & DEBUG_TIMER)
            printk(KERN_DEBUG "%s work(%d) empty(%d)\n", __func__,
                   dev->work, list_empty(&dev->expired));
    }
    return mask;
}

static void
dev_expire_timer(unsigned long data)
{
    struct mISDNtimer *timer = (void *)data;
    u_long          flags;

    spin_lock_irqsave(&timer->dev->lock, flags);
    list_move_tail(&timer->list, &timer->dev->expired);
    spin_unlock_irqrestore(&timer->dev->lock, flags);
    wake_up_interruptible(&timer->dev->wait);
}

static int
misdn_add_timer(struct mISDNtimerdev *dev, int timeout)
{
    int         id;
    u_long          flags;
    struct mISDNtimer   *timer;

    if (!timeout) {
        dev->work = 1;
        wake_up_interruptible(&dev->wait);
        id = 0;
    } else {
        timer = kzalloc(sizeof(struct mISDNtimer), GFP_KERNEL);
        if (!timer)
            return -ENOMEM;
        spin_lock_irqsave(&dev->lock, flags);
        timer->id = dev->next_id++;
        if (dev->next_id < 0)
            dev->next_id = 1;
        list_add_tail(&timer->list, &dev->pending);
        spin_unlock_irqrestore(&dev->lock, flags);
        timer->dev = dev;
        timer->tl.data = (long)timer;
        timer->tl.function = dev_expire_timer;
        init_timer(&timer->tl);
        timer->tl.expires = jiffies + ((HZ * (u_long)timeout) / 1000);
        add_timer(&timer->tl);
        id = timer->id;
    }
    return id;
}

static int
misdn_del_timer(struct mISDNtimerdev *dev, int id)
{
    u_long          flags;
    struct mISDNtimer   *timer;
    int         ret = 0;

    spin_lock_irqsave(&dev->lock, flags);
    list_for_each_entry(timer, &dev->pending, list) {
        if (timer->id == id) {
            list_del_init(&timer->list);
            /* RED-PEN AK: race -- timer can be still running on
             * other CPU. Needs reference count I think
             */
            del_timer(&timer->tl);
            ret = timer->id;
            kfree(timer);
            goto unlock;
        }
    }
unlock:
    spin_unlock_irqrestore(&dev->lock, flags);
    return ret;
}

static long
mISDN_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
{
    struct mISDNtimerdev    *dev = filep->private_data;
    int         id, tout, ret = 0;


    if (*debug & DEBUG_TIMER)
        printk(KERN_DEBUG "%s(%p, %x, %lx)\n", __func__,
               filep, cmd, arg);
    mutex_lock(&mISDN_mutex);
    switch (cmd) {
    case IMADDTIMER:
        if (get_user(tout, (int __user *)arg)) {
            ret = -EFAULT;
            break;
        }
        id = misdn_add_timer(dev, tout);
        if (*debug & DEBUG_TIMER)
            printk(KERN_DEBUG "%s add %d id %d\n", __func__,
                   tout, id);
        if (id < 0) {
            ret = id;
            break;
        }
        if (put_user(id, (int __user *)arg))
            ret = -EFAULT;
        break;
    case IMDELTIMER:
        if (get_user(id, (int __user *)arg)) {
            ret = -EFAULT;
            break;
        }
        if (*debug & DEBUG_TIMER)
            printk(KERN_DEBUG "%s del id %d\n", __func__, id);
        id = misdn_del_timer(dev, id);
        if (put_user(id, (int __user *)arg))
            ret = -EFAULT;
        break;
    default:
        ret = -EINVAL;
    }
    mutex_unlock(&mISDN_mutex);
    return ret;
}

static const struct file_operations mISDN_fops = {
    .read       = mISDN_read,
    .poll       = mISDN_poll,
    .unlocked_ioctl = mISDN_ioctl,
    .open       = mISDN_open,
    .release    = mISDN_close,
    .llseek     = no_llseek,
};

static struct miscdevice mISDNtimer = {
    .minor  = MISC_DYNAMIC_MINOR,
    .name   = "mISDNtimer",
    .fops   = &mISDN_fops,
};

int
mISDN_inittimer(u_int *deb)
{
    int err;

    debug = deb;
    err = misc_register(&mISDNtimer);
    if (err)
        printk(KERN_WARNING "mISDN: Could not register timer device\n");
    return err;
}

void mISDN_timer_cleanup(void)
{
    misc_deregister(&mISDNtimer);
}