root/drivers/watchdog/watchdog_core.c

DEFINITIONS

1. watchdog_deferred_registration_add
2. watchdog_deferred_registration_del
3. watchdog_check_min_max_timeout
4. watchdog_init_timeout
5. watchdog_reboot_notifier
6. watchdog_restart_notifier
7. watchdog_set_restart_priority
8. __watchdog_register_device
9. watchdog_register_device
10. __watchdog_unregister_device
11. watchdog_unregister_device
12. devm_watchdog_unregister_device
13. devm_watchdog_register_device
14. watchdog_deferred_registration
15. watchdog_init
16. watchdog_exit

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  *      watchdog_core.c
   4  *
   5  *      (c) Copyright 2008-2011 Alan Cox <alan@lxorguk.ukuu.org.uk>,
   6  *                                              All Rights Reserved.
   7  *
   8  *      (c) Copyright 2008-2011 Wim Van Sebroeck <wim@iguana.be>.
   9  *
  10  *      This source code is part of the generic code that can be used
  11  *      by all the watchdog timer drivers.
  12  *
  13  *      Based on source code of the following authors:
  14  *        Matt Domsch <Matt_Domsch@dell.com>,
  15  *        Rob Radez <rob@osinvestor.com>,
  16  *        Rusty Lynch <rusty@linux.co.intel.com>
  17  *        Satyam Sharma <satyam@infradead.org>
  18  *        Randy Dunlap <randy.dunlap@oracle.com>
  19  *
  20  *      Neither Alan Cox, CymruNet Ltd., Wim Van Sebroeck nor Iguana vzw.
  21  *      admit liability nor provide warranty for any of this software.
  22  *      This material is provided "AS-IS" and at no charge.
  23  */
  24 
  25 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  26 
  27 #include <linux/module.h>       /* For EXPORT_SYMBOL/module stuff/... */
  28 #include <linux/types.h>        /* For standard types */
  29 #include <linux/errno.h>        /* For the -ENODEV/... values */
  30 #include <linux/kernel.h>       /* For printk/panic/... */
  31 #include <linux/reboot.h>       /* For restart handler */
  32 #include <linux/watchdog.h>     /* For watchdog specific items */
  33 #include <linux/init.h>         /* For __init/__exit/... */
  34 #include <linux/idr.h>          /* For ida_* macros */
  35 #include <linux/err.h>          /* For IS_ERR macros */
  36 #include <linux/of.h>           /* For of_get_timeout_sec */
  37 
  38 #include "watchdog_core.h"      /* For watchdog_dev_register/... */
  39 
  40 static DEFINE_IDA(watchdog_ida);
  41 
  42 /*
  43  * Deferred Registration infrastructure.
  44  *
  45  * Sometimes watchdog drivers needs to be loaded as soon as possible,
  46  * for example when it's impossible to disable it. To do so,
  47  * raising the initcall level of the watchdog driver is a solution.
  48  * But in such case, the miscdev is maybe not ready (subsys_initcall), and
  49  * watchdog_core need miscdev to register the watchdog as a char device.
  50  *
  51  * The deferred registration infrastructure offer a way for the watchdog
  52  * subsystem to register a watchdog properly, even before miscdev is ready.
  53  */
  54 
  55 static DEFINE_MUTEX(wtd_deferred_reg_mutex);
  56 static LIST_HEAD(wtd_deferred_reg_list);
  57 static bool wtd_deferred_reg_done;
  58 
  59 static void watchdog_deferred_registration_add(struct watchdog_device *wdd)
  60 {
  61         list_add_tail(&wdd->deferred,
  62                       &wtd_deferred_reg_list);
  63 }
  64 
  65 static void watchdog_deferred_registration_del(struct watchdog_device *wdd)
  66 {
  67         struct list_head *p, *n;
  68         struct watchdog_device *wdd_tmp;
  69 
  70         list_for_each_safe(p, n, &wtd_deferred_reg_list) {
  71                 wdd_tmp = list_entry(p, struct watchdog_device,
  72                                      deferred);
  73                 if (wdd_tmp == wdd) {
  74                         list_del(&wdd_tmp->deferred);
  75                         break;
  76                 }
  77         }
  78 }
  79 
  80 static void watchdog_check_min_max_timeout(struct watchdog_device *wdd)
  81 {
  82         /*
  83          * Check that we have valid min and max timeout values, if
  84          * not reset them both to 0 (=not used or unknown)
  85          */
  86         if (!wdd->max_hw_heartbeat_ms && wdd->min_timeout > wdd->max_timeout) {
  87                 pr_info("Invalid min and max timeout values, resetting to 0!\n");
  88                 wdd->min_timeout = 0;
  89                 wdd->max_timeout = 0;
  90         }
  91 }
  92 
  93 /**
  94  * watchdog_init_timeout() - initialize the timeout field
  95  * @wdd: watchdog device
  96  * @timeout_parm: timeout module parameter
  97  * @dev: Device that stores the timeout-sec property
  98  *
  99  * Initialize the timeout field of the watchdog_device struct with either the
 100  * timeout module parameter (if it is valid value) or the timeout-sec property
 101  * (only if it is a valid value and the timeout_parm is out of bounds).
 102  * If none of them are valid then we keep the old value (which should normally
 103  * be the default timeout value). Note that for the module parameter, '0' means
 104  * 'use default' while it is an invalid value for the timeout-sec property.
 105  * It should simply be dropped if you want to use the default value then.
 106  *
 107  * A zero is returned on success or -EINVAL if all provided values are out of
 108  * bounds.
 109  */
 110 int watchdog_init_timeout(struct watchdog_device *wdd,
 111                                 unsigned int timeout_parm, struct device *dev)
 112 {
 113         const char *dev_str = wdd->parent ? dev_name(wdd->parent) :
 114                               (const char *)wdd->info->identity;
 115         unsigned int t = 0;
 116         int ret = 0;
 117 
 118         watchdog_check_min_max_timeout(wdd);
 119 
 120         /* check the driver supplied value (likely a module parameter) first */
 121         if (timeout_parm) {
 122                 if (!watchdog_timeout_invalid(wdd, timeout_parm)) {
 123                         wdd->timeout = timeout_parm;
 124                         return 0;
 125                 }
 126                 pr_err("%s: driver supplied timeout (%u) out of range\n",
 127                         dev_str, timeout_parm);
 128                 ret = -EINVAL;
 129         }
 130 
 131         /* try to get the timeout_sec property */
 132         if (dev && dev->of_node &&
 133             of_property_read_u32(dev->of_node, "timeout-sec", &t) == 0) {
 134                 if (t && !watchdog_timeout_invalid(wdd, t)) {
 135                         wdd->timeout = t;
 136                         return 0;
 137                 }
 138                 pr_err("%s: DT supplied timeout (%u) out of range\n", dev_str, t);
 139                 ret = -EINVAL;
 140         }
 141 
 142         if (ret < 0 && wdd->timeout)
 143                 pr_warn("%s: falling back to default timeout (%u)\n", dev_str,
 144                         wdd->timeout);
 145 
 146         return ret;
 147 }
 148 EXPORT_SYMBOL_GPL(watchdog_init_timeout);
 149 
 150 static int watchdog_reboot_notifier(struct notifier_block *nb,
 151                                     unsigned long code, void *data)
 152 {
 153         struct watchdog_device *wdd;
 154 
 155         wdd = container_of(nb, struct watchdog_device, reboot_nb);
 156         if (code == SYS_DOWN || code == SYS_HALT) {
 157                 if (watchdog_active(wdd)) {
 158                         int ret;
 159 
 160                         ret = wdd->ops->stop(wdd);
 161                         if (ret)
 162                                 return NOTIFY_BAD;
 163                 }
 164         }
 165 
 166         return NOTIFY_DONE;
 167 }
 168 
 169 static int watchdog_restart_notifier(struct notifier_block *nb,
 170                                      unsigned long action, void *data)
 171 {
 172         struct watchdog_device *wdd = container_of(nb, struct watchdog_device,
 173                                                    restart_nb);
 174 
 175         int ret;
 176 
 177         ret = wdd->ops->restart(wdd, action, data);
 178         if (ret)
 179                 return NOTIFY_BAD;
 180 
 181         return NOTIFY_DONE;
 182 }
 183 
 184 /**
 185  * watchdog_set_restart_priority - Change priority of restart handler
 186  * @wdd: watchdog device
 187  * @priority: priority of the restart handler, should follow these guidelines:
 188  *   0:   use watchdog's restart function as last resort, has limited restart
 189  *        capabilies
 190  *   128: default restart handler, use if no other handler is expected to be
 191  *        available and/or if restart is sufficient to restart the entire system
 192  *   255: preempt all other handlers
 193  *
 194  * If a wdd->ops->restart function is provided when watchdog_register_device is
 195  * called, it will be registered as a restart handler with the priority given
 196  * here.
 197  */
 198 void watchdog_set_restart_priority(struct watchdog_device *wdd, int priority)
 199 {
 200         wdd->restart_nb.priority = priority;
 201 }
 202 EXPORT_SYMBOL_GPL(watchdog_set_restart_priority);
 203 
 204 static int __watchdog_register_device(struct watchdog_device *wdd)
 205 {
 206         int ret, id = -1;
 207 
 208         if (wdd == NULL || wdd->info == NULL || wdd->ops == NULL)
 209                 return -EINVAL;
 210 
 211         /* Mandatory operations need to be supported */
 212         if (!wdd->ops->start || (!wdd->ops->stop && !wdd->max_hw_heartbeat_ms))
 213                 return -EINVAL;
 214 
 215         watchdog_check_min_max_timeout(wdd);
 216 
 217         /*
 218          * Note: now that all watchdog_device data has been verified, we
 219          * will not check this anymore in other functions. If data gets
 220          * corrupted in a later stage then we expect a kernel panic!
 221          */
 222 
 223         /* Use alias for watchdog id if possible */
 224         if (wdd->parent) {
 225                 ret = of_alias_get_id(wdd->parent->of_node, "watchdog");
 226                 if (ret >= 0)
 227                         id = ida_simple_get(&watchdog_ida, ret,
 228                                             ret + 1, GFP_KERNEL);
 229         }
 230 
 231         if (id < 0)
 232                 id = ida_simple_get(&watchdog_ida, 0, MAX_DOGS, GFP_KERNEL);
 233 
 234         if (id < 0)
 235                 return id;
 236         wdd->id = id;
 237 
 238         ret = watchdog_dev_register(wdd);
 239         if (ret) {
 240                 ida_simple_remove(&watchdog_ida, id);
 241                 if (!(id == 0 && ret == -EBUSY))
 242                         return ret;
 243 
 244                 /* Retry in case a legacy watchdog module exists */
 245                 id = ida_simple_get(&watchdog_ida, 1, MAX_DOGS, GFP_KERNEL);
 246                 if (id < 0)
 247                         return id;
 248                 wdd->id = id;
 249 
 250                 ret = watchdog_dev_register(wdd);
 251                 if (ret) {
 252                         ida_simple_remove(&watchdog_ida, id);
 253                         return ret;
 254                 }
 255         }
 256 
 257         if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status)) {
 258                 wdd->reboot_nb.notifier_call = watchdog_reboot_notifier;
 259 
 260                 ret = register_reboot_notifier(&wdd->reboot_nb);
 261                 if (ret) {
 262                         pr_err("watchdog%d: Cannot register reboot notifier (%d)\n",
 263                                wdd->id, ret);
 264                         watchdog_dev_unregister(wdd);
 265                         ida_simple_remove(&watchdog_ida, id);
 266                         return ret;
 267                 }
 268         }
 269 
 270         if (wdd->ops->restart) {
 271                 wdd->restart_nb.notifier_call = watchdog_restart_notifier;
 272 
 273                 ret = register_restart_handler(&wdd->restart_nb);
 274                 if (ret)
 275                         pr_warn("watchdog%d: Cannot register restart handler (%d)\n",
 276                                 wdd->id, ret);
 277         }
 278 
 279         return 0;
 280 }
 281 
 282 /**
 283  * watchdog_register_device() - register a watchdog device
 284  * @wdd: watchdog device
 285  *
 286  * Register a watchdog device with the kernel so that the
 287  * watchdog timer can be accessed from userspace.
 288  *
 289  * A zero is returned on success and a negative errno code for
 290  * failure.
 291  */
 292 
 293 int watchdog_register_device(struct watchdog_device *wdd)
 294 {
 295         const char *dev_str;
 296         int ret = 0;
 297 
 298         mutex_lock(&wtd_deferred_reg_mutex);
 299         if (wtd_deferred_reg_done)
 300                 ret = __watchdog_register_device(wdd);
 301         else
 302                 watchdog_deferred_registration_add(wdd);
 303         mutex_unlock(&wtd_deferred_reg_mutex);
 304 
 305         if (ret) {
 306                 dev_str = wdd->parent ? dev_name(wdd->parent) :
 307                           (const char *)wdd->info->identity;
 308                 pr_err("%s: failed to register watchdog device (err = %d)\n",
 309                         dev_str, ret);
 310         }
 311 
 312         return ret;
 313 }
 314 EXPORT_SYMBOL_GPL(watchdog_register_device);
 315 
 316 static void __watchdog_unregister_device(struct watchdog_device *wdd)
 317 {
 318         if (wdd == NULL)
 319                 return;
 320 
 321         if (wdd->ops->restart)
 322                 unregister_restart_handler(&wdd->restart_nb);
 323 
 324         if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status))
 325                 unregister_reboot_notifier(&wdd->reboot_nb);
 326 
 327         watchdog_dev_unregister(wdd);
 328         ida_simple_remove(&watchdog_ida, wdd->id);
 329 }
 330 
 331 /**
 332  * watchdog_unregister_device() - unregister a watchdog device
 333  * @wdd: watchdog device to unregister
 334  *
 335  * Unregister a watchdog device that was previously successfully
 336  * registered with watchdog_register_device().
 337  */
 338 
 339 void watchdog_unregister_device(struct watchdog_device *wdd)
 340 {
 341         mutex_lock(&wtd_deferred_reg_mutex);
 342         if (wtd_deferred_reg_done)
 343                 __watchdog_unregister_device(wdd);
 344         else
 345                 watchdog_deferred_registration_del(wdd);
 346         mutex_unlock(&wtd_deferred_reg_mutex);
 347 }
 348 
 349 EXPORT_SYMBOL_GPL(watchdog_unregister_device);
 350 
 351 static void devm_watchdog_unregister_device(struct device *dev, void *res)
 352 {
 353         watchdog_unregister_device(*(struct watchdog_device **)res);
 354 }
 355 
 356 /**
 357  * devm_watchdog_register_device() - resource managed watchdog_register_device()
 358  * @dev: device that is registering this watchdog device
 359  * @wdd: watchdog device
 360  *
 361  * Managed watchdog_register_device(). For watchdog device registered by this
 362  * function,  watchdog_unregister_device() is automatically called on driver
 363  * detach. See watchdog_register_device() for more information.
 364  */
 365 int devm_watchdog_register_device(struct device *dev,
 366                                 struct watchdog_device *wdd)
 367 {
 368         struct watchdog_device **rcwdd;
 369         int ret;
 370 
 371         rcwdd = devres_alloc(devm_watchdog_unregister_device, sizeof(*rcwdd),
 372                              GFP_KERNEL);
 373         if (!rcwdd)
 374                 return -ENOMEM;
 375 
 376         ret = watchdog_register_device(wdd);
 377         if (!ret) {
 378                 *rcwdd = wdd;
 379                 devres_add(dev, rcwdd);
 380         } else {
 381                 devres_free(rcwdd);
 382         }
 383 
 384         return ret;
 385 }
 386 EXPORT_SYMBOL_GPL(devm_watchdog_register_device);
 387 
 388 static int __init watchdog_deferred_registration(void)
 389 {
 390         mutex_lock(&wtd_deferred_reg_mutex);
 391         wtd_deferred_reg_done = true;
 392         while (!list_empty(&wtd_deferred_reg_list)) {
 393                 struct watchdog_device *wdd;
 394 
 395                 wdd = list_first_entry(&wtd_deferred_reg_list,
 396                                        struct watchdog_device, deferred);
 397                 list_del(&wdd->deferred);
 398                 __watchdog_register_device(wdd);
 399         }
 400         mutex_unlock(&wtd_deferred_reg_mutex);
 401         return 0;
 402 }
 403 
 404 static int __init watchdog_init(void)
 405 {
 406         int err;
 407 
 408         err = watchdog_dev_init();
 409         if (err < 0)
 410                 return err;
 411 
 412         watchdog_deferred_registration();
 413         return 0;
 414 }
 415 
 416 static void __exit watchdog_exit(void)
 417 {
 418         watchdog_dev_exit();
 419         ida_destroy(&watchdog_ida);
 420 }
 421 
 422 subsys_initcall_sync(watchdog_init);
 423 module_exit(watchdog_exit);
 424 
 425 MODULE_AUTHOR("Alan Cox <alan@lxorguk.ukuu.org.uk>");
 426 MODULE_AUTHOR("Wim Van Sebroeck <wim@iguana.be>");
 427 MODULE_DESCRIPTION("WatchDog Timer Driver Core");
 428 MODULE_LICENSE("GPL");