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 /*
  47  * Deferred Registration infrastructure.
  48  *
  49  * Sometimes watchdog drivers needs to be loaded as soon as possible,
  50  * for example when it's impossible to disable it. To do so,
  51  * raising the initcall level of the watchdog driver is a solution.
  52  * But in such case, the miscdev is maybe not ready (subsys_initcall), and
  53  * watchdog_core need miscdev to register the watchdog as a char device.
  54  *
  55  * The deferred registration infrastructure offer a way for the watchdog
  56  * subsystem to register a watchdog properly, even before miscdev is ready.
  57  */
  58
  59 static DEFINE_MUTEX(wtd_deferred_reg_mutex);
  60 static LIST_HEAD(wtd_deferred_reg_list);
  61 static bool wtd_deferred_reg_done;
  62
  63 static int watchdog_deferred_registration_add(struct watchdog_device *wdd)
  64 {
  65         list_add_tail(&wdd->deferred,
  66                       &wtd_deferred_reg_list);
  67         return 0;
  68 }
  69
  70 static void watchdog_deferred_registration_del(struct watchdog_device *wdd)
  71 {
  72         struct list_head *p, *n;
  73         struct watchdog_device *wdd_tmp;
  74
  75         list_for_each_safe(p, n, &wtd_deferred_reg_list) {
  76                 wdd_tmp = list_entry(p, struct watchdog_device,
  77                                      deferred);
  78                 if (wdd_tmp == wdd) {
  79                         list_del(&wdd_tmp->deferred);
  80                         break;
  81                 }
  82         }
  83 }
  84
  85 static void watchdog_check_min_max_timeout(struct watchdog_device *wdd)
  86 {
  87         /*
  88          * Check that we have valid min and max timeout values, if
  89          * not reset them both to 0 (=not used or unknown)
  90          */
  91         if (wdd->min_timeout > wdd->max_timeout) {
  92                 pr_info("Invalid min and max timeout values, resetting to 0!\n");
  93                 wdd->min_timeout = 0;
  94                 wdd->max_timeout = 0;
  95         }
  96 }
  97
  98 /**
  99  * watchdog_init_timeout() - initialize the timeout field
 100  * @timeout_parm: timeout module parameter
 101  * @dev: Device that stores the timeout-sec property
 102  *
 103  * Initialize the timeout field of the watchdog_device struct with either the
 104  * timeout module parameter (if it is valid value) or the timeout-sec property
 105  * (only if it is a valid value and the timeout_parm is out of bounds).
 106  * If none of them are valid then we keep the old value (which should normally
 107  * be the default timeout value.
 108  *
 109  * A zero is returned on success and -EINVAL for failure.
 110  */
 111 int watchdog_init_timeout(struct watchdog_device *wdd,
 112                                 unsigned int timeout_parm, struct device *dev)
 113 {
 114         unsigned int t = 0;
 115         int ret = 0;
 116
 117         watchdog_check_min_max_timeout(wdd);
 118
 119         /* try to get the timeout module parameter first */
 120         if (!watchdog_timeout_invalid(wdd, timeout_parm) && timeout_parm) {
 121                 wdd->timeout = timeout_parm;
 122                 return ret;
 123         }
 124         if (timeout_parm)
 125                 ret = -EINVAL;
 126
 127         /* try to get the timeout_sec property */
 128         if (dev == NULL || dev->of_node == NULL)
 129                 return ret;
 130         of_property_read_u32(dev->of_node, "timeout-sec", &t);
 131         if (!watchdog_timeout_invalid(wdd, t) && t)
 132                 wdd->timeout = t;
 133         else
 134                 ret = -EINVAL;
 135
 136         return ret;
 137 }
 138 EXPORT_SYMBOL_GPL(watchdog_init_timeout);
 139
 140 static int __watchdog_register_device(struct watchdog_device *wdd)
 141 {
 142         int ret, id, devno;
 143
 144         if (wdd == NULL || wdd->info == NULL || wdd->ops == NULL)
 145                 return -EINVAL;
 146
 147         /* Mandatory operations need to be supported */
 148         if (wdd->ops->start == NULL || wdd->ops->stop == NULL)
 149                 return -EINVAL;
 150
 151         watchdog_check_min_max_timeout(wdd);
 152
 153         /*
 154          * Note: now that all watchdog_device data has been verified, we
 155          * will not check this anymore in other functions. If data gets
 156          * corrupted in a later stage then we expect a kernel panic!
 157          */
 158
 159         mutex_init(&wdd->lock);
 160         id = ida_simple_get(&watchdog_ida, 0, MAX_DOGS, GFP_KERNEL);
 161         if (id < 0)
 162                 return id;
 163         wdd->id = id;
 164
 165         ret = watchdog_dev_register(wdd);
 166         if (ret) {
 167                 ida_simple_remove(&watchdog_ida, id);
 168                 if (!(id == 0 && ret == -EBUSY))
 169                         return ret;
 170
 171                 /* Retry in case a legacy watchdog module exists */
 172                 id = ida_simple_get(&watchdog_ida, 1, MAX_DOGS, GFP_KERNEL);
 173                 if (id < 0)
 174                         return id;
 175                 wdd->id = id;
 176
 177                 ret = watchdog_dev_register(wdd);
 178                 if (ret) {
 179                         ida_simple_remove(&watchdog_ida, id);
 180                         return ret;
 181                 }
 182         }
 183
 184         devno = wdd->cdev.dev;
 185         wdd->dev = device_create(watchdog_class, wdd->parent, devno,
 186                                         NULL, "watchdog%d", wdd->id);
 187         if (IS_ERR(wdd->dev)) {
 188                 watchdog_dev_unregister(wdd);
 189                 ida_simple_remove(&watchdog_ida, id);
 190                 ret = PTR_ERR(wdd->dev);
 191                 return ret;
 192         }
 193
 194         return 0;
 195 }
 196
 197 /**
 198  * watchdog_register_device() - register a watchdog device
 199  * @wdd: watchdog device
 200  *
 201  * Register a watchdog device with the kernel so that the
 202  * watchdog timer can be accessed from userspace.
 203  *
 204  * A zero is returned on success and a negative errno code for
 205  * failure.
 206  */
 207
 208 int watchdog_register_device(struct watchdog_device *wdd)
 209 {
 210         int ret;
 211
 212         mutex_lock(&wtd_deferred_reg_mutex);
 213         if (wtd_deferred_reg_done)
 214                 ret = __watchdog_register_device(wdd);
 215         else
 216                 ret = watchdog_deferred_registration_add(wdd);
 217         mutex_unlock(&wtd_deferred_reg_mutex);
 218         return ret;
 219 }
 220 EXPORT_SYMBOL_GPL(watchdog_register_device);
 221
 222 static void __watchdog_unregister_device(struct watchdog_device *wdd)
 223 {
 224         int ret;
 225         int devno;
 226
 227         if (wdd == NULL)
 228                 return;
 229
 230         devno = wdd->cdev.dev;
 231         ret = watchdog_dev_unregister(wdd);
 232         if (ret)
 233                 pr_err("error unregistering /dev/watchdog (err=%d)\n", ret);
 234         device_destroy(watchdog_class, devno);
 235         ida_simple_remove(&watchdog_ida, wdd->id);
 236         wdd->dev = NULL;
 237 }
 238
 239 /**
 240  * watchdog_unregister_device() - unregister a watchdog device
 241  * @wdd: watchdog device to unregister
 242  *
 243  * Unregister a watchdog device that was previously successfully
 244  * registered with watchdog_register_device().
 245  */
 246
 247 void watchdog_unregister_device(struct watchdog_device *wdd)
 248 {
 249         mutex_lock(&wtd_deferred_reg_mutex);
 250         if (wtd_deferred_reg_done)
 251                 __watchdog_unregister_device(wdd);
 252         else
 253                 watchdog_deferred_registration_del(wdd);
 254         mutex_unlock(&wtd_deferred_reg_mutex);
 255 }
 256
 257 EXPORT_SYMBOL_GPL(watchdog_unregister_device);
 258
 259 static int __init watchdog_deferred_registration(void)
 260 {
 261         mutex_lock(&wtd_deferred_reg_mutex);
 262         wtd_deferred_reg_done = true;
 263         while (!list_empty(&wtd_deferred_reg_list)) {
 264                 struct watchdog_device *wdd;
 265
 266                 wdd = list_first_entry(&wtd_deferred_reg_list,
 267                                        struct watchdog_device, deferred);
 268                 list_del(&wdd->deferred);
 269                 __watchdog_register_device(wdd);
 270         }
 271         mutex_unlock(&wtd_deferred_reg_mutex);
 272         return 0;
 273 }
 274
 275 static int __init watchdog_init(void)
 276 {
 277         int err;
 278
 279         watchdog_class = class_create(THIS_MODULE, "watchdog");
 280         if (IS_ERR(watchdog_class)) {
 281                 pr_err("couldn't create class\n");
 282                 return PTR_ERR(watchdog_class);
 283         }
 284
 285         err = watchdog_dev_init();
 286         if (err < 0) {
 287                 class_destroy(watchdog_class);
 288                 return err;
 289         }
 290
 291         watchdog_deferred_registration();
 292         return 0;
 293 }
 294
 295 static void __exit watchdog_exit(void)
 296 {
 297         watchdog_dev_exit();
 298         class_destroy(watchdog_class);
 299         ida_destroy(&watchdog_ida);
 300 }
 301
 302 subsys_initcall_sync(watchdog_init);
 303 module_exit(watchdog_exit);
 304
 305 MODULE_AUTHOR("Alan Cox <alan@lxorguk.ukuu.org.uk>");
 306 MODULE_AUTHOR("Wim Van Sebroeck <wim@iguana.be>");
 307 MODULE_DESCRIPTION("WatchDog Timer Driver Core");
 308 MODULE_LICENSE("GPL");