pcwd_usb.c

Go to the documentation of this file.

/*
 *  Berkshire USB-PC Watchdog Card Driver
 *
 *  (c) Copyright 2004-2007 Wim Van Sebroeck <[email protected]>.
 *
 *  Based on source code of the following authors:
 *    Ken Hollis <[email protected]>,
 *    Alan Cox <[email protected]>,
 *    Matt Domsch <[email protected]>,
 *    Rob Radez <[email protected]>,
 *    Greg Kroah-Hartman <[email protected]>
 *
 *  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 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.
 *
 *  Thanks also to Simon Machell at Berkshire Products Inc. for
 *  providing the test hardware. More info is available at
 *  http://www.berkprod.com/ or http://www.pcwatchdog.com/
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>   /* For module specific items */
#include <linux/moduleparam.h>  /* For new moduleparam's */
#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/delay.h>    /* For mdelay function */
#include <linux/miscdevice.h>   /* For MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR) */
#include <linux/watchdog.h> /* For the watchdog specific items */
#include <linux/notifier.h> /* For notifier support */
#include <linux/reboot.h>   /* For reboot_notifier stuff */
#include <linux/init.h>     /* For __init/__exit/... */
#include <linux/fs.h>       /* For file operations */
#include <linux/usb.h>      /* For USB functions */
#include <linux/slab.h>     /* For kmalloc, ... */
#include <linux/mutex.h>    /* For mutex locking */
#include <linux/hid.h>      /* For HID_REQ_SET_REPORT & HID_DT_REPORT */
#include <linux/uaccess.h>  /* For copy_to_user/put_user/... */

#ifdef CONFIG_USB_DEBUG
static int debug = 1;
#else
static int debug;
#endif

/* Use our own dbg macro */

#undef dbg
#ifndef DEBUG
#define DEBUG
#endif
#define dbg(format, ...)                \
do {                            \
    if (debug)                  \
        pr_debug(format "\n", ##__VA_ARGS__);   \
} while (0)

/* Module and Version Information */
#define DRIVER_VERSION "1.02"
#define DRIVER_AUTHOR "Wim Van Sebroeck <[email protected]>"
#define DRIVER_DESC "Berkshire USB-PC Watchdog driver"
#define DRIVER_LICENSE "GPL"
#define DRIVER_NAME "pcwd_usb"

MODULE_AUTHOR(DRIVER_AUTHOR);
MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_LICENSE(DRIVER_LICENSE);
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
MODULE_ALIAS_MISCDEV(TEMP_MINOR);

/* Module Parameters */
module_param(debug, int, 0);
MODULE_PARM_DESC(debug, "Debug enabled or not");

#define WATCHDOG_HEARTBEAT 0    /* default heartbeat =
                        delay-time from dip-switches */
static int heartbeat = WATCHDOG_HEARTBEAT;
module_param(heartbeat, int, 0);
MODULE_PARM_DESC(heartbeat, "Watchdog heartbeat in seconds. "
    "(0<heartbeat<65536 or 0=delay-time from dip-switches, default="
                __MODULE_STRING(WATCHDOG_HEARTBEAT) ")");

static bool nowayout = WATCHDOG_NOWAYOUT;
module_param(nowayout, bool, 0);
MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
                __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");

/* The vendor and product id's for the USB-PC Watchdog card */
#define USB_PCWD_VENDOR_ID  0x0c98
#define USB_PCWD_PRODUCT_ID 0x1140

/* table of devices that work with this driver */
static struct usb_device_id usb_pcwd_table[] = {
    { USB_DEVICE(USB_PCWD_VENDOR_ID, USB_PCWD_PRODUCT_ID) },
    { }                 /* Terminating entry */
};
MODULE_DEVICE_TABLE(usb, usb_pcwd_table);

/* according to documentation max. time to process a command for the USB
 * watchdog card is 100 or 200 ms, so we give it 250 ms to do it's job */
#define USB_COMMAND_TIMEOUT 250

/* Watchdog's internal commands */
#define CMD_READ_TEMP           0x02    /* Read Temperature;
                            Re-trigger Watchdog */
#define CMD_TRIGGER         CMD_READ_TEMP
#define CMD_GET_STATUS          0x04    /* Get Status Information */
#define CMD_GET_FIRMWARE_VERSION    0x08    /* Get Firmware Version */
#define CMD_GET_DIP_SWITCH_SETTINGS 0x0c    /* Get Dip Switch Settings */
#define CMD_READ_WATCHDOG_TIMEOUT   0x18    /* Read Current Watchdog Time */
#define CMD_WRITE_WATCHDOG_TIMEOUT  0x19    /* Write Current WatchdogTime */
#define CMD_ENABLE_WATCHDOG     0x30    /* Enable / Disable Watchdog */
#define CMD_DISABLE_WATCHDOG        CMD_ENABLE_WATCHDOG

/* Watchdog's Dip Switch heartbeat values */
static const int heartbeat_tbl[] = {
    5,  /* OFF-OFF-OFF  =  5 Sec  */
    10, /* OFF-OFF-ON   = 10 Sec  */
    30, /* OFF-ON-OFF   = 30 Sec  */
    60, /* OFF-ON-ON    =  1 Min  */
    300,    /* ON-OFF-OFF   =  5 Min  */
    600,    /* ON-OFF-ON    = 10 Min  */
    1800,   /* ON-ON-OFF    = 30 Min  */
    3600,   /* ON-ON-ON =  1 hour */
};

/* We can only use 1 card due to the /dev/watchdog restriction */
static int cards_found;

/* some internal variables */
static unsigned long is_active;
static char expect_release;

/* Structure to hold all of our device specific stuff */
struct usb_pcwd_private {
    /* save off the usb device pointer */
    struct usb_device   *udev;
    /* the interface for this device */
    struct usb_interface    *interface;

    /* the interface number used for cmd's */
    unsigned int        interface_number;

    /* the buffer to intr data */
    unsigned char       *intr_buffer;
    /* the dma address for the intr buffer */
    dma_addr_t      intr_dma;
    /* the size of the intr buffer */
    size_t          intr_size;
    /* the urb used for the intr pipe */
    struct urb      *intr_urb;

    /* The command that is reported back */
    unsigned char       cmd_command;
    /* The data MSB that is reported back */
    unsigned char       cmd_data_msb;
    /* The data LSB that is reported back */
    unsigned char       cmd_data_lsb;
    /* true if we received a report after a command */
    atomic_t        cmd_received;

    /* Wether or not the device exists */
    int         exists;
    /* locks this structure */
    struct mutex        mtx;
};
static struct usb_pcwd_private *usb_pcwd_device;

/* prevent races between open() and disconnect() */
static DEFINE_MUTEX(disconnect_mutex);

/* local function prototypes */
static int usb_pcwd_probe(struct usb_interface *interface,
                        const struct usb_device_id *id);
static void usb_pcwd_disconnect(struct usb_interface *interface);

/* usb specific object needed to register this driver with the usb subsystem */
static struct usb_driver usb_pcwd_driver = {
    .name =     DRIVER_NAME,
    .probe =    usb_pcwd_probe,
    .disconnect =   usb_pcwd_disconnect,
    .id_table = usb_pcwd_table,
};


static void usb_pcwd_intr_done(struct urb *urb)
{
    struct usb_pcwd_private *usb_pcwd =
                (struct usb_pcwd_private *)urb->context;
    unsigned char *data = usb_pcwd->intr_buffer;
    int retval;

    switch (urb->status) {
    case 0:         /* success */
        break;
    case -ECONNRESET:   /* unlink */
    case -ENOENT:
    case -ESHUTDOWN:
        /* this urb is terminated, clean up */
        dbg("%s - urb shutting down with status: %d", __func__,
                                urb->status);
        return;
    /* -EPIPE:  should clear the halt */
    default:        /* error */
        dbg("%s - nonzero urb status received: %d", __func__,
                                urb->status);
        goto resubmit;
    }

    dbg("received following data cmd=0x%02x msb=0x%02x lsb=0x%02x",
        data[0], data[1], data[2]);

    usb_pcwd->cmd_command  = data[0];
    usb_pcwd->cmd_data_msb = data[1];
    usb_pcwd->cmd_data_lsb = data[2];

    /* notify anyone waiting that the cmd has finished */
    atomic_set(&usb_pcwd->cmd_received, 1);

resubmit:
    retval = usb_submit_urb(urb, GFP_ATOMIC);
    if (retval)
        pr_err("can't resubmit intr, usb_submit_urb failed with result %d\n",
               retval);
}

static int usb_pcwd_send_command(struct usb_pcwd_private *usb_pcwd,
        unsigned char cmd, unsigned char *msb, unsigned char *lsb)
{
    int got_response, count;
    unsigned char buf[6];

    /* We will not send any commands if the USB PCWD device does
     * not exist */
    if ((!usb_pcwd) || (!usb_pcwd->exists))
        return -1;

    /* The USB PC Watchdog uses a 6 byte report format.
     * The board currently uses only 3 of the six bytes of the report. */
    buf[0] = cmd;           /* Byte 0 = CMD */
    buf[1] = *msb;          /* Byte 1 = Data MSB */
    buf[2] = *lsb;          /* Byte 2 = Data LSB */
    buf[3] = buf[4] = buf[5] = 0;   /* All other bytes not used */

    dbg("sending following data cmd=0x%02x msb=0x%02x lsb=0x%02x",
        buf[0], buf[1], buf[2]);

    atomic_set(&usb_pcwd->cmd_received, 0);

    if (usb_control_msg(usb_pcwd->udev, usb_sndctrlpipe(usb_pcwd->udev, 0),
            HID_REQ_SET_REPORT, HID_DT_REPORT,
            0x0200, usb_pcwd->interface_number, buf, sizeof(buf),
            USB_COMMAND_TIMEOUT) != sizeof(buf)) {
        dbg("usb_pcwd_send_command: error in usb_control_msg for "
                "cmd 0x%x 0x%x 0x%x\n", cmd, *msb, *lsb);
    }
    /* wait till the usb card processed the command,
     * with a max. timeout of USB_COMMAND_TIMEOUT */
    got_response = 0;
    for (count = 0; (count < USB_COMMAND_TIMEOUT) && (!got_response);
                                count++) {
        mdelay(1);
        if (atomic_read(&usb_pcwd->cmd_received))
            got_response = 1;
    }

    if ((got_response) && (cmd == usb_pcwd->cmd_command)) {
        /* read back response */
        *msb = usb_pcwd->cmd_data_msb;
        *lsb = usb_pcwd->cmd_data_lsb;
    }

    return got_response;
}

static int usb_pcwd_start(struct usb_pcwd_private *usb_pcwd)
{
    unsigned char msb = 0x00;
    unsigned char lsb = 0x00;
    int retval;

    /* Enable Watchdog */
    retval = usb_pcwd_send_command(usb_pcwd, CMD_ENABLE_WATCHDOG,
                                &msb, &lsb);

    if ((retval == 0) || (lsb == 0)) {
        pr_err("Card did not acknowledge enable attempt\n");
        return -1;
    }

    return 0;
}

static int usb_pcwd_stop(struct usb_pcwd_private *usb_pcwd)
{
    unsigned char msb = 0xA5;
    unsigned char lsb = 0xC3;
    int retval;

    /* Disable Watchdog */
    retval = usb_pcwd_send_command(usb_pcwd, CMD_DISABLE_WATCHDOG,
                                &msb, &lsb);

    if ((retval == 0) || (lsb != 0)) {
        pr_err("Card did not acknowledge disable attempt\n");
        return -1;
    }

    return 0;
}

static int usb_pcwd_keepalive(struct usb_pcwd_private *usb_pcwd)
{
    unsigned char dummy;

    /* Re-trigger Watchdog */
    usb_pcwd_send_command(usb_pcwd, CMD_TRIGGER, &dummy, &dummy);

    return 0;
}

static int usb_pcwd_set_heartbeat(struct usb_pcwd_private *usb_pcwd, int t)
{
    unsigned char msb = t / 256;
    unsigned char lsb = t % 256;

    if ((t < 0x0001) || (t > 0xFFFF))
        return -EINVAL;

    /* Write new heartbeat to watchdog */
    usb_pcwd_send_command(usb_pcwd, CMD_WRITE_WATCHDOG_TIMEOUT, &msb, &lsb);

    heartbeat = t;
    return 0;
}

static int usb_pcwd_get_temperature(struct usb_pcwd_private *usb_pcwd,
                            int *temperature)
{
    unsigned char msb, lsb;

    usb_pcwd_send_command(usb_pcwd, CMD_READ_TEMP, &msb, &lsb);

    /*
     * Convert celsius to fahrenheit, since this was
     * the decided 'standard' for this return value.
     */
    *temperature = (lsb * 9 / 5) + 32;

    return 0;
}

static int usb_pcwd_get_timeleft(struct usb_pcwd_private *usb_pcwd,
                                int *time_left)
{
    unsigned char msb, lsb;

    /* Read the time that's left before rebooting */
    /* Note: if the board is not yet armed then we will read 0xFFFF */
    usb_pcwd_send_command(usb_pcwd, CMD_READ_WATCHDOG_TIMEOUT, &msb, &lsb);

    *time_left = (msb << 8) + lsb;

    return 0;
}

/*
 *  /dev/watchdog handling
 */

static ssize_t usb_pcwd_write(struct file *file, const char __user *data,
                        size_t len, loff_t *ppos)
{
    /* See if we got the magic character 'V' and reload the timer */
    if (len) {
        if (!nowayout) {
            size_t i;

            /* note: just in case someone wrote the magic character
             * five months ago... */
            expect_release = 0;

            /* scan to see whether or not we got the
             * magic character */
            for (i = 0; i != len; i++) {
                char c;
                if (get_user(c, data + i))
                    return -EFAULT;
                if (c == 'V')
                    expect_release = 42;
            }
        }

        /* someone wrote to us, we should reload the timer */
        usb_pcwd_keepalive(usb_pcwd_device);
    }
    return len;
}

static long usb_pcwd_ioctl(struct file *file, unsigned int cmd,
                        unsigned long arg)
{
    void __user *argp = (void __user *)arg;
    int __user *p = argp;
    static const struct watchdog_info ident = {
        .options =      WDIOF_KEEPALIVEPING |
                    WDIOF_SETTIMEOUT |
                    WDIOF_MAGICCLOSE,
        .firmware_version = 1,
        .identity =     DRIVER_NAME,
    };

    switch (cmd) {
    case WDIOC_GETSUPPORT:
        return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;

    case WDIOC_GETSTATUS:
    case WDIOC_GETBOOTSTATUS:
        return put_user(0, p);

    case WDIOC_GETTEMP:
    {
        int temperature;

        if (usb_pcwd_get_temperature(usb_pcwd_device, &temperature))
            return -EFAULT;

        return put_user(temperature, p);
    }

    case WDIOC_SETOPTIONS:
    {
        int new_options, retval = -EINVAL;

        if (get_user(new_options, p))
            return -EFAULT;

        if (new_options & WDIOS_DISABLECARD) {
            usb_pcwd_stop(usb_pcwd_device);
            retval = 0;
        }

        if (new_options & WDIOS_ENABLECARD) {
            usb_pcwd_start(usb_pcwd_device);
            retval = 0;
        }

        return retval;
    }

    case WDIOC_KEEPALIVE:
        usb_pcwd_keepalive(usb_pcwd_device);
        return 0;

    case WDIOC_SETTIMEOUT:
    {
        int new_heartbeat;

        if (get_user(new_heartbeat, p))
            return -EFAULT;

        if (usb_pcwd_set_heartbeat(usb_pcwd_device, new_heartbeat))
            return -EINVAL;

        usb_pcwd_keepalive(usb_pcwd_device);
        /* Fall */
    }

    case WDIOC_GETTIMEOUT:
        return put_user(heartbeat, p);

    case WDIOC_GETTIMELEFT:
    {
        int time_left;

        if (usb_pcwd_get_timeleft(usb_pcwd_device, &time_left))
            return -EFAULT;

        return put_user(time_left, p);
    }

    default:
        return -ENOTTY;
    }
}

static int usb_pcwd_open(struct inode *inode, struct file *file)
{
    /* /dev/watchdog can only be opened once */
    if (test_and_set_bit(0, &is_active))
        return -EBUSY;

    /* Activate */
    usb_pcwd_start(usb_pcwd_device);
    usb_pcwd_keepalive(usb_pcwd_device);
    return nonseekable_open(inode, file);
}

static int usb_pcwd_release(struct inode *inode, struct file *file)
{
    /*
     *      Shut off the timer.
     */
    if (expect_release == 42) {
        usb_pcwd_stop(usb_pcwd_device);
    } else {
        pr_crit("Unexpected close, not stopping watchdog!\n");
        usb_pcwd_keepalive(usb_pcwd_device);
    }
    expect_release = 0;
    clear_bit(0, &is_active);
    return 0;
}

/*
 *  /dev/temperature handling
 */

static ssize_t usb_pcwd_temperature_read(struct file *file, char __user *data,
                size_t len, loff_t *ppos)
{
    int temperature;

    if (usb_pcwd_get_temperature(usb_pcwd_device, &temperature))
        return -EFAULT;

    if (copy_to_user(data, &temperature, 1))
        return -EFAULT;

    return 1;
}

static int usb_pcwd_temperature_open(struct inode *inode, struct file *file)
{
    return nonseekable_open(inode, file);
}

static int usb_pcwd_temperature_release(struct inode *inode, struct file *file)
{
    return 0;
}

/*
 *  Notify system
 */

static int usb_pcwd_notify_sys(struct notifier_block *this, unsigned long code,
                                void *unused)
{
    if (code == SYS_DOWN || code == SYS_HALT)
        usb_pcwd_stop(usb_pcwd_device); /* Turn the WDT off */

    return NOTIFY_DONE;
}

/*
 *  Kernel Interfaces
 */

static const struct file_operations usb_pcwd_fops = {
    .owner =    THIS_MODULE,
    .llseek =   no_llseek,
    .write =    usb_pcwd_write,
    .unlocked_ioctl = usb_pcwd_ioctl,
    .open =     usb_pcwd_open,
    .release =  usb_pcwd_release,
};

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

static const struct file_operations usb_pcwd_temperature_fops = {
    .owner =    THIS_MODULE,
    .llseek =   no_llseek,
    .read =     usb_pcwd_temperature_read,
    .open =     usb_pcwd_temperature_open,
    .release =  usb_pcwd_temperature_release,
};

static struct miscdevice usb_pcwd_temperature_miscdev = {
    .minor =    TEMP_MINOR,
    .name =     "temperature",
    .fops =     &usb_pcwd_temperature_fops,
};

static struct notifier_block usb_pcwd_notifier = {
    .notifier_call =    usb_pcwd_notify_sys,
};

static inline void usb_pcwd_delete(struct usb_pcwd_private *usb_pcwd)
{
    usb_free_urb(usb_pcwd->intr_urb);
    if (usb_pcwd->intr_buffer != NULL)
        usb_free_coherent(usb_pcwd->udev, usb_pcwd->intr_size,
                  usb_pcwd->intr_buffer, usb_pcwd->intr_dma);
    kfree(usb_pcwd);
}

static int usb_pcwd_probe(struct usb_interface *interface,
                        const struct usb_device_id *id)
{
    struct usb_device *udev = interface_to_usbdev(interface);
    struct usb_host_interface *iface_desc;
    struct usb_endpoint_descriptor *endpoint;
    struct usb_pcwd_private *usb_pcwd = NULL;
    int pipe, maxp;
    int retval = -ENOMEM;
    int got_fw_rev;
    unsigned char fw_rev_major, fw_rev_minor;
    char fw_ver_str[20];
    unsigned char option_switches, dummy;

    cards_found++;
    if (cards_found > 1) {
        pr_err("This driver only supports 1 device\n");
        return -ENODEV;
    }

    /* get the active interface descriptor */
    iface_desc = interface->cur_altsetting;

    /* check out that we have a HID device */
    if (!(iface_desc->desc.bInterfaceClass == USB_CLASS_HID)) {
        pr_err("The device isn't a Human Interface Device\n");
        return -ENODEV;
    }

    /* check out the endpoint: it has to be Interrupt & IN */
    endpoint = &iface_desc->endpoint[0].desc;

    if (!usb_endpoint_is_int_in(endpoint)) {
        /* we didn't find a Interrupt endpoint with direction IN */
        pr_err("Couldn't find an INTR & IN endpoint\n");
        return -ENODEV;
    }

    /* get a handle to the interrupt data pipe */
    pipe = usb_rcvintpipe(udev, endpoint->bEndpointAddress);
    maxp = usb_maxpacket(udev, pipe, usb_pipeout(pipe));

    /* allocate memory for our device and initialize it */
    usb_pcwd = kzalloc(sizeof(struct usb_pcwd_private), GFP_KERNEL);
    if (usb_pcwd == NULL) {
        pr_err("Out of memory\n");
        goto error;
    }

    usb_pcwd_device = usb_pcwd;

    mutex_init(&usb_pcwd->mtx);
    usb_pcwd->udev = udev;
    usb_pcwd->interface = interface;
    usb_pcwd->interface_number = iface_desc->desc.bInterfaceNumber;
    usb_pcwd->intr_size = (le16_to_cpu(endpoint->wMaxPacketSize) > 8 ?
                le16_to_cpu(endpoint->wMaxPacketSize) : 8);

    /* set up the memory buffer's */
    usb_pcwd->intr_buffer = usb_alloc_coherent(udev, usb_pcwd->intr_size,
                    GFP_ATOMIC, &usb_pcwd->intr_dma);
    if (!usb_pcwd->intr_buffer) {
        pr_err("Out of memory\n");
        goto error;
    }

    /* allocate the urb's */
    usb_pcwd->intr_urb = usb_alloc_urb(0, GFP_KERNEL);
    if (!usb_pcwd->intr_urb) {
        pr_err("Out of memory\n");
        goto error;
    }

    /* initialise the intr urb's */
    usb_fill_int_urb(usb_pcwd->intr_urb, udev, pipe,
            usb_pcwd->intr_buffer, usb_pcwd->intr_size,
            usb_pcwd_intr_done, usb_pcwd, endpoint->bInterval);
    usb_pcwd->intr_urb->transfer_dma = usb_pcwd->intr_dma;
    usb_pcwd->intr_urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;

    /* register our interrupt URB with the USB system */
    if (usb_submit_urb(usb_pcwd->intr_urb, GFP_KERNEL)) {
        pr_err("Problem registering interrupt URB\n");
        retval = -EIO; /* failure */
        goto error;
    }

    /* The device exists and can be communicated with */
    usb_pcwd->exists = 1;

    /* disable card */
    usb_pcwd_stop(usb_pcwd);

    /* Get the Firmware Version */
    got_fw_rev = usb_pcwd_send_command(usb_pcwd, CMD_GET_FIRMWARE_VERSION,
                        &fw_rev_major, &fw_rev_minor);
    if (got_fw_rev)
        sprintf(fw_ver_str, "%u.%02u", fw_rev_major, fw_rev_minor);
    else
        sprintf(fw_ver_str, "<card no answer>");

    pr_info("Found card (Firmware: %s) with temp option\n", fw_ver_str);

    /* Get switch settings */
    usb_pcwd_send_command(usb_pcwd, CMD_GET_DIP_SWITCH_SETTINGS, &dummy,
                            &option_switches);

    pr_info("Option switches (0x%02x): Temperature Reset Enable=%s, Power On Delay=%s\n",
        option_switches,
        ((option_switches & 0x10) ? "ON" : "OFF"),
        ((option_switches & 0x08) ? "ON" : "OFF"));

    /* If heartbeat = 0 then we use the heartbeat from the dip-switches */
    if (heartbeat == 0)
        heartbeat = heartbeat_tbl[(option_switches & 0x07)];

    /* Check that the heartbeat value is within it's range ;
     * if not reset to the default */
    if (usb_pcwd_set_heartbeat(usb_pcwd, heartbeat)) {
        usb_pcwd_set_heartbeat(usb_pcwd, WATCHDOG_HEARTBEAT);
        pr_info("heartbeat value must be 0<heartbeat<65536, using %d\n",
            WATCHDOG_HEARTBEAT);
    }

    retval = register_reboot_notifier(&usb_pcwd_notifier);
    if (retval != 0) {
        pr_err("cannot register reboot notifier (err=%d)\n", retval);
        goto error;
    }

    retval = misc_register(&usb_pcwd_temperature_miscdev);
    if (retval != 0) {
        pr_err("cannot register miscdev on minor=%d (err=%d)\n",
               TEMP_MINOR, retval);
        goto err_out_unregister_reboot;
    }

    retval = misc_register(&usb_pcwd_miscdev);
    if (retval != 0) {
        pr_err("cannot register miscdev on minor=%d (err=%d)\n",
               WATCHDOG_MINOR, retval);
        goto err_out_misc_deregister;
    }

    /* we can register the device now, as it is ready */
    usb_set_intfdata(interface, usb_pcwd);

    pr_info("initialized. heartbeat=%d sec (nowayout=%d)\n",
        heartbeat, nowayout);

    return 0;

err_out_misc_deregister:
    misc_deregister(&usb_pcwd_temperature_miscdev);
err_out_unregister_reboot:
    unregister_reboot_notifier(&usb_pcwd_notifier);
error:
    if (usb_pcwd)
        usb_pcwd_delete(usb_pcwd);
    usb_pcwd_device = NULL;
    return retval;
}


static void usb_pcwd_disconnect(struct usb_interface *interface)
{
    struct usb_pcwd_private *usb_pcwd;

    /* prevent races with open() */
    mutex_lock(&disconnect_mutex);

    usb_pcwd = usb_get_intfdata(interface);
    usb_set_intfdata(interface, NULL);

    mutex_lock(&usb_pcwd->mtx);

    /* Stop the timer before we leave */
    if (!nowayout)
        usb_pcwd_stop(usb_pcwd);

    /* We should now stop communicating with the USB PCWD device */
    usb_pcwd->exists = 0;

    /* Deregister */
    misc_deregister(&usb_pcwd_miscdev);
    misc_deregister(&usb_pcwd_temperature_miscdev);
    unregister_reboot_notifier(&usb_pcwd_notifier);

    mutex_unlock(&usb_pcwd->mtx);

    /* Delete the USB PCWD device */
    usb_pcwd_delete(usb_pcwd);

    cards_found--;

    mutex_unlock(&disconnect_mutex);

    pr_info("USB PC Watchdog disconnected\n");
}

module_usb_driver(usb_pcwd_driver);