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 #include <linux/of.h>           /* For of_get_timeout_sec */
  40
  41 #include "watchdog_core.h"      /* For watchdog_dev_register/... */
  42
  43 static DEFINE_IDA(watchdog_ida);
  44 static struct class *watchdog_class;
  45
  46 static void watchdog_check_min_max_timeout(struct watchdog_device *wdd)
  47 {
  48         /*
  49          * Check that we have valid min and max timeout values, if
  50          * not reset them both to 0 (=not used or unknown)
  51          */
  52         if (wdd->min_timeout > wdd->max_timeout) {
  53                 pr_info("Invalid min and max timeout values, resetting to 0!\n");
  54                 wdd->min_timeout = 0;
  55                 wdd->max_timeout = 0;
  56         }
  57 }
  58
  59 /**
  60  * watchdog_init_timeout() - initialize the timeout field
  61  * @timeout_parm: timeout module parameter
  62  * @dev: Device that stores the timeout-sec property
  63  *
  64  * Initialize the timeout field of the watchdog_device struct with either the
  65  * timeout module parameter (if it is valid value) or the timeout-sec property
  66  * (only if it is a valid value and the timeout_parm is out of bounds).
  67  * If none of them are valid then we keep the old value (which should normally
  68  * be the default timeout value.
  69  *
  70  * A zero is returned on success and -EINVAL for failure.
  71  */
  72 int watchdog_init_timeout(struct watchdog_device *wdd,
  73                                 unsigned int timeout_parm, struct device *dev)
  74 {
  75         unsigned int t = 0;
  76         int ret = 0;
  77
  78         watchdog_check_min_max_timeout(wdd);
  79
  80         /* try to get the timeout module parameter first */
  81         if (!watchdog_timeout_invalid(wdd, timeout_parm) && timeout_parm) {
  82                 wdd->timeout = timeout_parm;
  83                 return ret;
  84         }
  85         if (timeout_parm)
  86                 ret = -EINVAL;
  87
  88         /* try to get the timeout_sec property */
  89         if (dev == NULL || dev->of_node == NULL)
  90                 return ret;
  91         of_property_read_u32(dev->of_node, "timeout-sec", &t);
  92         if (!watchdog_timeout_invalid(wdd, t) && t)
  93                 wdd->timeout = t;
  94         else
  95                 ret = -EINVAL;
  96
  97         return ret;
  98 }
  99 EXPORT_SYMBOL_GPL(watchdog_init_timeout);
 100
 101 /**
 102  * watchdog_register_device() - register a watchdog device
 103  * @wdd: watchdog device
 104  *
 105  * Register a watchdog device with the kernel so that the
 106  * watchdog timer can be accessed from userspace.
 107  *
 108  * A zero is returned on success and a negative errno code for
 109  * failure.
 110  */
 111 int watchdog_register_device(struct watchdog_device *wdd)
 112 {
 113         int ret, id, devno;
 114
 115         if (wdd == NULL || wdd->info == NULL || wdd->ops == NULL)
 116                 return -EINVAL;
 117
 118         /* Mandatory operations need to be supported */
 119         if (wdd->ops->start == NULL || wdd->ops->stop == NULL)
 120                 return -EINVAL;
 121
 122         watchdog_check_min_max_timeout(wdd);
 123
 124         /*
 125          * Note: now that all watchdog_device data has been verified, we
 126          * will not check this anymore in other functions. If data gets
 127          * corrupted in a later stage then we expect a kernel panic!
 128          */
 129
 130         mutex_init(&wdd->lock);
 131         id = ida_simple_get(&watchdog_ida, 0, MAX_DOGS, GFP_KERNEL);
 132         if (id < 0)
 133                 return id;
 134         wdd->id = id;
 135
 136         ret = watchdog_dev_register(wdd);
 137         if (ret) {
 138                 ida_simple_remove(&watchdog_ida, id);
 139                 if (!(id == 0 && ret == -EBUSY))
 140                         return ret;
 141
 142                 /* Retry in case a legacy watchdog module exists */
 143                 id = ida_simple_get(&watchdog_ida, 1, MAX_DOGS, GFP_KERNEL);
 144                 if (id < 0)
 145                         return id;
 146                 wdd->id = id;
 147
 148                 ret = watchdog_dev_register(wdd);
 149                 if (ret) {
 150                         ida_simple_remove(&watchdog_ida, id);
 151                         return ret;
 152                 }
 153         }
 154
 155         devno = wdd->cdev.dev;
 156         wdd->dev = device_create(watchdog_class, wdd->parent, devno,
 157                                         NULL, "watchdog%d", wdd->id);
 158         if (IS_ERR(wdd->dev)) {
 159                 watchdog_dev_unregister(wdd);
 160                 ida_simple_remove(&watchdog_ida, id);
 161                 ret = PTR_ERR(wdd->dev);
 162                 return ret;
 163         }
 164
 165         return 0;
 166 }
 167 EXPORT_SYMBOL_GPL(watchdog_register_device);
 168
 169 /**
 170  * watchdog_unregister_device() - unregister a watchdog device
 171  * @wdd: watchdog device to unregister
 172  *
 173  * Unregister a watchdog device that was previously successfully
 174  * registered with watchdog_register_device().
 175  */
 176 void watchdog_unregister_device(struct watchdog_device *wdd)
 177 {
 178         int ret;
 179         int devno;
 180
 181         if (wdd == NULL)
 182                 return;
 183
 184         devno = wdd->cdev.dev;
 185         ret = watchdog_dev_unregister(wdd);
 186         if (ret)
 187                 pr_err("error unregistering /dev/watchdog (err=%d)\n", ret);
 188         device_destroy(watchdog_class, devno);
 189         ida_simple_remove(&watchdog_ida, wdd->id);
 190         wdd->dev = NULL;
 191 }
 192 EXPORT_SYMBOL_GPL(watchdog_unregister_device);
 193
 194 static int __init watchdog_init(void)
 195 {
 196         int err;
 197
 198         watchdog_class = class_create(THIS_MODULE, "watchdog");
 199         if (IS_ERR(watchdog_class)) {
 200                 pr_err("couldn't create class\n");
 201                 return PTR_ERR(watchdog_class);
 202         }
 203
 204         err = watchdog_dev_init();
 205         if (err < 0) {
 206                 class_destroy(watchdog_class);
 207                 return err;
 208         }
 209
 210         return 0;
 211 }
 212
 213 static void __exit watchdog_exit(void)
 214 {
 215         watchdog_dev_exit();
 216         class_destroy(watchdog_class);
 217         ida_destroy(&watchdog_ida);
 218 }
 219
 220 subsys_initcall(watchdog_init);
 221 module_exit(watchdog_exit);
 222
 223 MODULE_AUTHOR("Alan Cox <alan@lxorguk.ukuu.org.uk>");
 224 MODULE_AUTHOR("Wim Van Sebroeck <wim@iguana.be>");
 225 MODULE_DESCRIPTION("WatchDog Timer Driver Core");
 226 MODULE_LICENSE("GPL");