drivers/watchdog/watchdog_core.c

   1 /*
   2  *      watchdog_core.c
   3  *
   4  *      (c) Copyright 2008-2011 Alan Cox <alan@lxorguk.ukuu.org.uk>,
   5  *                                              All Rights Reserved.
   6  *
   7  *      (c) Copyright 2008-2011 Wim Van Sebroeck <wim@iguana.be>.
   8  *
   9  *      This source code is part of the generic code that can be used
  10  *      by all the watchdog timer drivers.
  11  *
  12  *      Based on source code of the following authors:
  13  *        Matt Domsch <Matt_Domsch@dell.com>,
  14  *        Rob Radez <rob@osinvestor.com>,
  15  *        Rusty Lynch <rusty@linux.co.intel.com>
  16  *        Satyam Sharma <satyam@infradead.org>
  17  *        Randy Dunlap <randy.dunlap@oracle.com>
  18  *
  19  *      This program is free software; you can redistribute it and/or
  20  *      modify it under the terms of the GNU General Public License
  21  *      as published by the Free Software Foundation; either version
  22  *      2 of the License, or (at your option) any later version.
  23  *
  24  *      Neither Alan Cox, CymruNet Ltd., Wim Van Sebroeck nor Iguana vzw.
  25  *      admit liability nor provide warranty for any of this software.
  26  *      This material is provided "AS-IS" and at no charge.
  27  */
  28
  29 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  30
  31 #include <linux/module.h>       /* For EXPORT_SYMBOL/module stuff/... */
  32 #include <linux/types.h>        /* For standard types */
  33 #include <linux/errno.h>        /* For the -ENODEV/... values */
  34 #include <linux/kernel.h>       /* For printk/panic/... */
  35 #include <linux/watchdog.h>     /* For watchdog specific items */
  36 #include <linux/init.h>         /* For __init/__exit/... */
  37
  38 #include "watchdog_dev.h"       /* For watchdog_dev_register/... */
  39
  40 /**
  41  * watchdog_register_device() - register a watchdog device
  42  * @wdd: watchdog device
  43  *
  44  * Register a watchdog device with the kernel so that the
  45  * watchdog timer can be accessed from userspace.
  46  *
  47  * A zero is returned on success and a negative errno code for
  48  * failure.
  49  */
  50 int watchdog_register_device(struct watchdog_device *wdd)
  51 {
  52         int ret;
  53
  54         if (wdd == NULL || wdd->info == NULL || wdd->ops == NULL)
  55                 return -EINVAL;
  56
  57         /* Mandatory operations need to be supported */
  58         if (wdd->ops->start == NULL || wdd->ops->stop == NULL)
  59                 return -EINVAL;
  60
  61         /*
  62          * Check that we have valid min and max timeout values, if
  63          * not reset them both to 0 (=not used or unknown)
  64          */
  65         if (wdd->min_timeout > wdd->max_timeout) {
  66                 pr_info("Invalid min and max timeout values, resetting to 0!\n");
  67                 wdd->min_timeout = 0;
  68                 wdd->max_timeout = 0;
  69         }
  70
  71         /*
  72          * Note: now that all watchdog_device data has been verified, we
  73          * will not check this anymore in other functions. If data gets
  74          * corrupted in a later stage then we expect a kernel panic!
  75          */
  76
  77         /* We only support 1 watchdog device via the /dev/watchdog interface */
  78         ret = watchdog_dev_register(wdd);
  79         if (ret) {
  80                 pr_err("error registering /dev/watchdog (err=%d).\n", ret);
  81                 return ret;
  82         }
  83
  84         return 0;
  85 }
  86 EXPORT_SYMBOL_GPL(watchdog_register_device);
  87
  88 /**
  89  * watchdog_unregister_device() - unregister a watchdog device
  90  * @wdd: watchdog device to unregister
  91  *
  92  * Unregister a watchdog device that was previously successfully
  93  * registered with watchdog_register_device().
  94  */
  95 void watchdog_unregister_device(struct watchdog_device *wdd)
  96 {
  97         int ret;
  98
  99         if (wdd == NULL)
 100                 return;
 101
 102         ret = watchdog_dev_unregister(wdd);
 103         if (ret)
 104                 pr_err("error unregistering /dev/watchdog (err=%d).\n", ret);
 105 }
 106 EXPORT_SYMBOL_GPL(watchdog_unregister_device);
 107
 108 MODULE_AUTHOR("Alan Cox <alan@lxorguk.ukuu.org.uk>");
 109 MODULE_AUTHOR("Wim Van Sebroeck <wim@iguana.be>");
 110 MODULE_DESCRIPTION("WatchDog Timer Driver Core");
 111 MODULE_LICENSE("GPL");