/*
 *      watchdog_dev.c
 *
 *      (c) Copyright 2008-2011 Alan Cox <alan@lxorguk.ukuu.org.uk>,
 *                                              All Rights Reserved.
 *
 *      (c) Copyright 2008-2011 Wim Van Sebroeck <wim@iguana.be>.
 *
 *
 *      This source code is part of the generic code that can be used
 *      by all the watchdog timer drivers.
 *
 *      This part of the generic code takes care of the following
 *      misc device: /dev/watchdog.
 *
 *      Based on source code of the following authors:
 *        Matt Domsch <Matt_Domsch@dell.com>,
 *        Rob Radez <rob@osinvestor.com>,
 *        Rusty Lynch <rusty@linux.co.intel.com>
 *        Satyam Sharma <satyam@infradead.org>
 *        Randy Dunlap <randy.dunlap@oracle.com>
 *
 *      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.
 *
 *      Neither Alan Cox, CymruNet Ltd., Wim Van Sebroeck nor Iguana vzw.
 *      admit liability nor provide warranty for any of this software.
 *      This material is provided "AS-IS" and at no charge.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>       /* For module stuff/... */
#include <linux/types.h>        /* For standard types (like size_t) */
#include <linux/errno.h>        /* For the -ENODEV/... values */
#include <linux/kernel.h>       /* For printk/panic/... */
#include <linux/fs.h>           /* For file operations */
#include <linux/watchdog.h>     /* For watchdog specific items */
#include <linux/miscdevice.h>   /* For handling misc devices */
#include <linux/init.h>         /* For __init/__exit/... */
#include <linux/uaccess.h>      /* For copy_to_user/put_user/... */

#include "watchdog_core.h"

/* the dev_t structure to store the dynamically allocated watchdog devices */
static dev_t watchdog_devt;
/* the watchdog device behind /dev/watchdog */
static struct watchdog_device *old_wdd;

/*
 *      watchdog_ping: ping the watchdog.
 *      @wddev: the watchdog device to ping
 *
 *      If the watchdog has no own ping operation then it needs to be
 *      restarted via the start operation. This wrapper function does
 *      exactly that.
 *      We only ping when the watchdog device is running.
 */

static int watchdog_ping(struct watchdog_device *wddev)
{
        int err = 0;

        mutex_lock(&wddev->lock);

        if (test_bit(WDOG_UNREGISTERED, &wddev->status)) {
                err = -ENODEV;
                goto out_ping;
        }

        if (!watchdog_active(wddev))
                goto out_ping;

        if (wddev->ops->ping)
                err = wddev->ops->ping(wddev);  /* ping the watchdog */
        else
                err = wddev->ops->start(wddev); /* restart watchdog */

out_ping:
        mutex_unlock(&wddev->lock);
        return err;
}

/*
 *      watchdog_start: wrapper to start the watchdog.
 *      @wddev: the watchdog device to start
 *
 *      Start the watchdog if it is not active and mark it active.
 *      This function returns zero on success or a negative errno code for
 *      failure.
 */

static int watchdog_start(struct watchdog_device *wddev)
{
        int err = 0;

        mutex_lock(&wddev->lock);

        if (test_bit(WDOG_UNREGISTERED, &wddev->status)) {
                err = -ENODEV;
                goto out_start;
        }

        if (watchdog_active(wddev))
                goto out_start;

        err = wddev->ops->start(wddev);
        if (err == 0)
                set_bit(WDOG_ACTIVE, &wddev->status);

out_start:
        mutex_unlock(&wddev->lock);
        return err;
}

/*
 *      watchdog_stop: wrapper to stop the watchdog.
 *      @wddev: the watchdog device to stop
 *
 *      Stop the watchdog if it is still active and unmark it active.
 *      This function returns zero on success or a negative errno code for
 *      failure.
 *      If the 'nowayout' feature was set, the watchdog cannot be stopped.
 */

static int watchdog_stop(struct watchdog_device *wddev)
{
        int err = 0;

        mutex_lock(&wddev->lock);

        if (test_bit(WDOG_UNREGISTERED, &wddev->status)) {
                err = -ENODEV;
                goto out_stop;
        }

        if (!watchdog_active(wddev))
                goto out_stop;

        if (test_bit(WDOG_NO_WAY_OUT, &wddev->status)) {
                dev_info(wddev->dev, "nowayout prevents watchdog being stopped!\n");
                err = -EBUSY;
                goto out_stop;
        }

        err = wddev->ops->stop(wddev);
        if (err == 0)
                clear_bit(WDOG_ACTIVE, &wddev->status);

out_stop:
        mutex_unlock(&wddev->lock);
        return err;
}

/*
 *      watchdog_get_status: wrapper to get the watchdog status
 *      @wddev: the watchdog device to get the status from
 *      @status: the status of the watchdog device
 *
 *      Get the watchdog's status flags.
 */

static int watchdog_get_status(struct watchdog_device *wddev,
                                                        unsigned int *status)
{
        int err = 0;

        *status = 0;
        if (!wddev->ops->status)
                return -EOPNOTSUPP;

        mutex_lock(&wddev->lock);

        if (test_bit(WDOG_UNREGISTERED, &wddev->status)) {
                err = -ENODEV;
                goto out_status;
        }

        *status = wddev->ops->status(wddev);

out_status:
        mutex_unlock(&wddev->lock);
        return err;
}

/*
 *      watchdog_set_timeout: set the watchdog timer timeout
 *      @wddev: the watchdog device to set the timeout for
 *      @timeout: timeout to set in seconds
 */

static int watchdog_set_timeout(struct watchdog_device *wddev,
                                                        unsigned int timeout)
{
        int err;

        if ((wddev->ops->set_timeout == NULL) ||
            !(wddev->info->options & WDIOF_SETTIMEOUT))
                return -EOPNOTSUPP;

        if ((wddev->max_timeout != 0) &&
            (timeout < wddev->min_timeout || timeout > wddev->max_timeout))
                return -EINVAL;

        mutex_lock(&wddev->lock);

        if (test_bit(WDOG_UNREGISTERED, &wddev->status)) {
                err = -ENODEV;
                goto out_timeout;
        }

        err = wddev->ops->set_timeout(wddev, timeout);

out_timeout:
        mutex_unlock(&wddev->lock);
        return err;
}

/*
 *      watchdog_get_timeleft: wrapper to get the time left before a reboot
 *      @wddev: the watchdog device to get the remaining time from
 *      @timeleft: the time that's left
 *
 *      Get the time before a watchdog will reboot (if not pinged).
 */

static int watchdog_get_timeleft(struct watchdog_device *wddev,
                                                        unsigned int *timeleft)
{
        int err = 0;

        *timeleft = 0;
        if (!wddev->ops->get_timeleft)
                return -EOPNOTSUPP;

        mutex_lock(&wddev->lock);

        if (test_bit(WDOG_UNREGISTERED, &wddev->status)) {
                err = -ENODEV;
                goto out_timeleft;
        }

        *timeleft = wddev->ops->get_timeleft(wddev);

out_timeleft:
        mutex_unlock(&wddev->lock);
        return err;
}

/*
 *      watchdog_ioctl_op: call the watchdog drivers ioctl op if defined
 *      @wddev: the watchdog device to do the ioctl on
 *      @cmd: watchdog command
 *      @arg: argument pointer
 */

static int watchdog_ioctl_op(struct watchdog_device *wddev, unsigned int cmd,
                                                        unsigned long arg)
{
        int err;

        if (!wddev->ops->ioctl)
                return -ENOIOCTLCMD;

        mutex_lock(&wddev->lock);

        if (test_bit(WDOG_UNREGISTERED, &wddev->status)) {
                err = -ENODEV;
                goto out_ioctl;
        }

        err = wddev->ops->ioctl(wddev, cmd, arg);

out_ioctl:
        mutex_unlock(&wddev->lock);
        return err;
}

/*
 *      watchdog_write: writes to the watchdog.
 *      @file: file from VFS
 *      @data: user address of data
 *      @len: length of data
 *      @ppos: pointer to the file offset
 *
 *      A write to a watchdog device is defined as a keepalive ping.
 *      Writing the magic 'V' sequence allows the next close to turn
 *      off the watchdog (if 'nowayout' is not set).
 */

static ssize_t watchdog_write(struct file *file, const char __user *data,
                                                size_t len, loff_t *ppos)
{
        struct watchdog_device *wdd = file->private_data;
        size_t i;
        char c;

        if (len == 0)
                return 0;

        /*
         * Note: just in case someone wrote the magic character
         * five months ago...
         */
        clear_bit(WDOG_ALLOW_RELEASE, &wdd->status);

        /* scan to see whether or not we got the magic character */
        for (i = 0; i != len; i++) {
                if (get_user(c, data + i))
                        return -EFAULT;
                if (c == 'V')
                        set_bit(WDOG_ALLOW_RELEASE, &wdd->status);
        }

        /* someone wrote to us, so we send the watchdog a keepalive ping */
        watchdog_ping(wdd);

        return len;
}

/*
 *      watchdog_ioctl: handle the different ioctl's for the watchdog device.
 *      @file: file handle to the device
 *      @cmd: watchdog command
 *      @arg: argument pointer
 *
 *      The watchdog API defines a common set of functions for all watchdogs
 *      according to their available features.
 */

static long watchdog_ioctl(struct file *file, unsigned int cmd,
                                                        unsigned long arg)
{
        struct watchdog_device *wdd = file->private_data;
        void __user *argp = (void __user *)arg;
        int __user *p = argp;
        unsigned int val;
        int err;

        err = watchdog_ioctl_op(wdd, cmd, arg);
        if (err != -ENOIOCTLCMD)
                return err;

        switch (cmd) {
        case WDIOC_GETSUPPORT:
                return copy_to_user(argp, wdd->info,
                        sizeof(struct watchdog_info)) ? -EFAULT : 0;
        case WDIOC_GETSTATUS:
                err = watchdog_get_status(wdd, &val);
                if (err == -ENODEV)
                        return err;
                return put_user(val, p);
        case WDIOC_GETBOOTSTATUS:
                return put_user(wdd->bootstatus, p);
        case WDIOC_SETOPTIONS:
                if (get_user(val, p))
                        return -EFAULT;
                if (val & WDIOS_DISABLECARD) {
                        err = watchdog_stop(wdd);
                        if (err < 0)
                                return err;
                }
                if (val & WDIOS_ENABLECARD) {
                        err = watchdog_start(wdd);
                        if (err < 0)
                                return err;
                }
                return 0;
        case WDIOC_KEEPALIVE:
                if (!(wdd->info->options & WDIOF_KEEPALIVEPING))
                        return -EOPNOTSUPP;
                watchdog_ping(wdd);
                return 0;
        case WDIOC_SETTIMEOUT:
                if (get_user(val, p))
                        return -EFAULT;
                err = watchdog_set_timeout(wdd, val);
                if (err < 0)
                        return err;
                /* If the watchdog is active then we send a keepalive ping
                 * to make sure that the watchdog keep's running (and if
                 * possible that it takes the new timeout) */
                watchdog_ping(wdd);
                /* Fall */
        case WDIOC_GETTIMEOUT:
                /* timeout == 0 means that we don't know the timeout */
                if (wdd->timeout == 0)
                        return -EOPNOTSUPP;
                return put_user(wdd->timeout, p);
        case WDIOC_GETTIMELEFT:
                err = watchdog_get_timeleft(wdd, &val);
                if (err)
                        return err;
                return put_user(val, p);
        default:
                return -ENOTTY;
        }
}

/*
 *      watchdog_open: open the /dev/watchdog* devices.
 *      @inode: inode of device
 *      @file: file handle to device
 *
 *      When the /dev/watchdog* device gets opened, we start the watchdog.
 *      Watch out: the /dev/watchdog device is single open, so we make sure
 *      it can only be opened once.
 */

static int watchdog_open(struct inode *inode, struct file *file)
{
        int err = -EBUSY;
        struct watchdog_device *wdd;

        /* Get the corresponding watchdog device */
        if (imajor(inode) == MISC_MAJOR)
                wdd = old_wdd;
        else
                wdd = container_of(inode->i_cdev, struct watchdog_device, cdev);

        /* the watchdog is single open! */
        if (test_and_set_bit(WDOG_DEV_OPEN, &wdd->status))
                return -EBUSY;

        /*
         * If the /dev/watchdog device is open, we don't want the module
         * to be unloaded.
         */
        if (!try_module_get(wdd->ops->owner))
                goto out;

        err = watchdog_start(wdd);
        if (err < 0)
                goto out_mod;

        file->private_data = wdd;

        if (wdd->ops->ref)
                wdd->ops->ref(wdd);

        /* dev/watchdog is a virtual (and thus non-seekable) filesystem */
        return nonseekable_open(inode, file);

out_mod:
        module_put(wdd->ops->owner);
out:
        clear_bit(WDOG_DEV_OPEN, &wdd->status);
        return err;
}

/*
 *      watchdog_release: release the watchdog device.
 *      @inode: inode of device
 *      @file: file handle to device
 *
 *      This is the code for when /dev/watchdog gets closed. We will only
 *      stop the watchdog when we have received the magic char (and nowayout
 *      was not set), else the watchdog will keep running.
 */

static int watchdog_release(struct inode *inode, struct file *file)
{
        struct watchdog_device *wdd = file->private_data;
        int err = -EBUSY;

        /*
         * We only stop the watchdog if we received the magic character
         * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then
         * watchdog_stop will fail.
         */
        if (test_and_clear_bit(WDOG_ALLOW_RELEASE, &wdd->status) ||
            !(wdd->info->options & WDIOF_MAGICCLOSE))
                err = watchdog_stop(wdd);

        /* If the watchdog was not stopped, send a keepalive ping */
        if (err < 0) {
                mutex_lock(&wdd->lock);
                if (!test_bit(WDOG_UNREGISTERED, &wdd->status))
                        dev_crit(wdd->dev, "watchdog did not stop!\n");
                mutex_unlock(&wdd->lock);
                watchdog_ping(wdd);
        }

        /* Allow the owner module to be unloaded again */
        module_put(wdd->ops->owner);

        /* make sure that /dev/watchdog can be re-opened */
        clear_bit(WDOG_DEV_OPEN, &wdd->status);

        /* Note wdd may be gone after this, do not use after this! */
        if (wdd->ops->unref)
                wdd->ops->unref(wdd);

        return 0;
}

static const struct file_operations watchdog_fops = {
        .owner          = THIS_MODULE,
        .write          = watchdog_write,
        .unlocked_ioctl = watchdog_ioctl,
        .open           = watchdog_open,
        .release        = watchdog_release,
};

static struct miscdevice watchdog_miscdev = {
        .minor          = WATCHDOG_MINOR,
        .name           = "watchdog",
        .fops           = &watchdog_fops,
};

/*
 *      watchdog_dev_register: register a watchdog device
 *      @watchdog: watchdog device
 *
 *      Register a watchdog device including handling the legacy
 *      /dev/watchdog node. /dev/watchdog is actually a miscdevice and
 *      thus we set it up like that.
 */

int watchdog_dev_register(struct watchdog_device *watchdog)
{
        int err, devno;

        if (watchdog->id == 0) {
                watchdog_miscdev.parent = watchdog->parent;
                err = misc_register(&watchdog_miscdev);
                if (err != 0) {
                        pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n",
                                watchdog->info->identity, WATCHDOG_MINOR, err);
                        if (err == -EBUSY)
                                pr_err("%s: a legacy watchdog module is probably present.\n",
                                        watchdog->info->identity);
                        return err;
                }
                old_wdd = watchdog;
        }

        /* Fill in the data structures */
        devno = MKDEV(MAJOR(watchdog_devt), watchdog->id);
        cdev_init(&watchdog->cdev, &watchdog_fops);
        watchdog->cdev.owner = watchdog->ops->owner;

        /* Add the device */
        err  = cdev_add(&watchdog->cdev, devno, 1);
        if (err) {
                pr_err("watchdog%d unable to add device %d:%d\n",
                        watchdog->id,  MAJOR(watchdog_devt), watchdog->id);
                if (watchdog->id == 0) {
                        misc_deregister(&watchdog_miscdev);
                        old_wdd = NULL;
                }
        }
        return err;
}

/*
 *      watchdog_dev_unregister: unregister a watchdog device
 *      @watchdog: watchdog device
 *
 *      Unregister the watchdog and if needed the legacy /dev/watchdog device.
 */

int watchdog_dev_unregister(struct watchdog_device *watchdog)
{
        mutex_lock(&watchdog->lock);
        set_bit(WDOG_UNREGISTERED, &watchdog->status);
        mutex_unlock(&watchdog->lock);

        cdev_del(&watchdog->cdev);
        if (watchdog->id == 0) {
                misc_deregister(&watchdog_miscdev);
                old_wdd = NULL;
        }
        return 0;
}

/*
 *      watchdog_dev_init: init dev part of watchdog core
 *
 *      Allocate a range of chardev nodes to use for watchdog devices
 */

int __init watchdog_dev_init(void)
{
        int err = alloc_chrdev_region(&watchdog_devt, 0, MAX_DOGS, "watchdog");
        if (err < 0)
                pr_err("watchdog: unable to allocate char dev region\n");
        return err;
}

/*
 *      watchdog_dev_exit: exit dev part of watchdog core
 *
 *      Release the range of chardev nodes used for watchdog devices
 */

void __exit watchdog_dev_exit(void)
{
        unregister_chrdev_region(watchdog_devt, MAX_DOGS);
}