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 #include <linux/idr.h>          /* For ida_* macros */
  38 #include <linux/err.h>          /* For IS_ERR macros */
  39
  40 #include "watchdog_core.h"      /* For watchdog_dev_register/... */
  41
  42 static DEFINE_IDA(watchdog_ida);
  43 static struct class *watchdog_class;
  44
  45 /**
  46  * watchdog_register_device() - register a watchdog device
  47  * @wdd: watchdog device
  48  *
  49  * Register a watchdog device with the kernel so that the
  50  * watchdog timer can be accessed from userspace.
  51  *
  52  * A zero is returned on success and a negative errno code for
  53  * failure.
  54  */
  55 int watchdog_register_device(struct watchdog_device *wdd)
  56 {
  57         int ret, id, devno;
  58
  59         if (wdd == NULL || wdd->info == NULL || wdd->ops == NULL)
  60                 return -EINVAL;
  61
  62         /* Mandatory operations need to be supported */
  63         if (wdd->ops->start == NULL || wdd->ops->stop == NULL)
  64                 return -EINVAL;
  65
  66         /*
  67          * Check that we have valid min and max timeout values, if
  68          * not reset them both to 0 (=not used or unknown)
  69          */
  70         if (wdd->min_timeout > wdd->max_timeout) {
  71                 pr_info("Invalid min and max timeout values, resetting to 0!\n");
  72                 wdd->min_timeout = 0;
  73                 wdd->max_timeout = 0;
  74         }
  75
  76         /*
  77          * Note: now that all watchdog_device data has been verified, we
  78          * will not check this anymore in other functions. If data gets
  79          * corrupted in a later stage then we expect a kernel panic!
  80          */
  81
  82         mutex_init(&wdd->lock);
  83         id = ida_simple_get(&watchdog_ida, 0, MAX_DOGS, GFP_KERNEL);
  84         if (id < 0)
  85                 return id;
  86         wdd->id = id;
  87
  88         ret = watchdog_dev_register(wdd);
  89         if (ret) {
  90                 ida_simple_remove(&watchdog_ida, id);
  91                 if (!(id == 0 && ret == -EBUSY))
  92                         return ret;
  93
  94                 /* Retry in case a legacy watchdog module exists */
  95                 id = ida_simple_get(&watchdog_ida, 1, MAX_DOGS, GFP_KERNEL);
  96                 if (id < 0)
  97                         return id;
  98                 wdd->id = id;
  99
 100                 ret = watchdog_dev_register(wdd);
 101                 if (ret) {
 102                         ida_simple_remove(&watchdog_ida, id);
 103                         return ret;
 104                 }
 105         }
 106
 107         devno = wdd->cdev.dev;
 108         wdd->dev = device_create(watchdog_class, wdd->parent, devno,
 109                                         NULL, "watchdog%d", wdd->id);
 110         if (IS_ERR(wdd->dev)) {
 111                 watchdog_dev_unregister(wdd);
 112                 ida_simple_remove(&watchdog_ida, id);
 113                 ret = PTR_ERR(wdd->dev);
 114                 return ret;
 115         }
 116
 117         return 0;
 118 }
 119 EXPORT_SYMBOL_GPL(watchdog_register_device);
 120
 121 /**
 122  * watchdog_unregister_device() - unregister a watchdog device
 123  * @wdd: watchdog device to unregister
 124  *
 125  * Unregister a watchdog device that was previously successfully
 126  * registered with watchdog_register_device().
 127  */
 128 void watchdog_unregister_device(struct watchdog_device *wdd)
 129 {
 130         int ret;
 131         int devno;
 132
 133         if (wdd == NULL)
 134                 return;
 135
 136         devno = wdd->cdev.dev;
 137         ret = watchdog_dev_unregister(wdd);
 138         if (ret)
 139                 pr_err("error unregistering /dev/watchdog (err=%d)\n", ret);
 140         device_destroy(watchdog_class, devno);
 141         ida_simple_remove(&watchdog_ida, wdd->id);
 142         wdd->dev = NULL;
 143 }
 144 EXPORT_SYMBOL_GPL(watchdog_unregister_device);
 145
 146 static int __init watchdog_init(void)
 147 {
 148         int err;
 149
 150         watchdog_class = class_create(THIS_MODULE, "watchdog");
 151         if (IS_ERR(watchdog_class)) {
 152                 pr_err("couldn't create class\n");
 153                 return PTR_ERR(watchdog_class);
 154         }
 155
 156         err = watchdog_dev_init();
 157         if (err < 0) {
 158                 class_destroy(watchdog_class);
 159                 return err;
 160         }
 161
 162         return 0;
 163 }
 164
 165 static void __exit watchdog_exit(void)
 166 {
 167         watchdog_dev_exit();
 168         class_destroy(watchdog_class);
 169         ida_destroy(&watchdog_ida);
 170 }
 171
 172 subsys_initcall(watchdog_init);
 173 module_exit(watchdog_exit);
 174
 175 MODULE_AUTHOR("Alan Cox <alan@lxorguk.ukuu.org.uk>");
 176 MODULE_AUTHOR("Wim Van Sebroeck <wim@iguana.be>");
 177 MODULE_DESCRIPTION("WatchDog Timer Driver Core");
 178 MODULE_LICENSE("GPL");