drivers/watchdog/watchdog_dev.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  *      watchdog_dev.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  *      (c) Copyright 2021 Hewlett Packard Enterprise Development LP.
  11  *
  12  *      This source code is part of the generic code that can be used
  13  *      by all the watchdog timer drivers.
  14  *
  15  *      This part of the generic code takes care of the following
  16  *      misc device: /dev/watchdog.
  17  *
  18  *      Based on source code of the following authors:
  19  *        Matt Domsch <Matt_Domsch@dell.com>,
  20  *        Rob Radez <rob@osinvestor.com>,
  21  *        Rusty Lynch <rusty@linux.co.intel.com>
  22  *        Satyam Sharma <satyam@infradead.org>
  23  *        Randy Dunlap <randy.dunlap@oracle.com>
  24  *
  25  *      Neither Alan Cox, CymruNet Ltd., Wim Van Sebroeck nor Iguana vzw.
  26  *      admit liability nor provide warranty for any of this software.
  27  *      This material is provided "AS-IS" and at no charge.
  28  */
  29
  30 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  31
  32 #include <linux/cdev.h>         /* For character device */
  33 #include <linux/errno.h>        /* For the -ENODEV/... values */
  34 #include <linux/fs.h>           /* For file operations */
  35 #include <linux/init.h>         /* For __init/__exit/... */
  36 #include <linux/hrtimer.h>      /* For hrtimers */
  37 #include <linux/kernel.h>       /* For printk/panic/... */
  38 #include <linux/kstrtox.h>      /* For kstrto* */
  39 #include <linux/kthread.h>      /* For kthread_work */
  40 #include <linux/miscdevice.h>   /* For handling misc devices */
  41 #include <linux/module.h>       /* For module stuff/... */
  42 #include <linux/mutex.h>        /* For mutexes */
  43 #include <linux/slab.h>         /* For memory functions */
  44 #include <linux/types.h>        /* For standard types (like size_t) */
  45 #include <linux/watchdog.h>     /* For watchdog specific items */
  46 #include <linux/uaccess.h>      /* For copy_to_user/put_user/... */
  47
  48 #include "watchdog_core.h"
  49 #include "watchdog_pretimeout.h"
  50
  51 #include <trace/events/watchdog.h>
  52
  53 /* the dev_t structure to store the dynamically allocated watchdog devices */
  54 static dev_t watchdog_devt;
  55 /* Reference to watchdog device behind /dev/watchdog */
  56 static struct watchdog_core_data *old_wd_data;
  57
  58 static struct kthread_worker *watchdog_kworker;
  59
  60 static bool handle_boot_enabled =
  61         IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED);
  62
  63 static unsigned open_timeout = CONFIG_WATCHDOG_OPEN_TIMEOUT;
  64
  65 static bool watchdog_past_open_deadline(struct watchdog_core_data *data)
  66 {
  67         return ktime_after(ktime_get(), data->open_deadline);
  68 }
  69
  70 static void watchdog_set_open_deadline(struct watchdog_core_data *data)
  71 {
  72         data->open_deadline = open_timeout ?
  73                 ktime_get() + ktime_set(open_timeout, 0) : KTIME_MAX;
  74 }
  75
  76 static inline bool watchdog_need_worker(struct watchdog_device *wdd)
  77 {
  78         /* All variables in milli-seconds */
  79         unsigned int hm = wdd->max_hw_heartbeat_ms;
  80         unsigned int t = wdd->timeout * 1000;
  81
  82         /*
  83          * A worker to generate heartbeat requests is needed if all of the
  84          * following conditions are true.
  85          * - Userspace activated the watchdog.
  86          * - The driver provided a value for the maximum hardware timeout, and
  87          *   thus is aware that the framework supports generating heartbeat
  88          *   requests.
  89          * - Userspace requests a longer timeout than the hardware can handle.
  90          *
  91          * Alternatively, if userspace has not opened the watchdog
  92          * device, we take care of feeding the watchdog if it is
  93          * running.
  94          */
  95         return (hm && watchdog_active(wdd) && t > hm) ||
  96                 (t && !watchdog_active(wdd) && watchdog_hw_running(wdd));
  97 }
  98
  99 static ktime_t watchdog_next_keepalive(struct watchdog_device *wdd)
 100 {
 101         struct watchdog_core_data *wd_data = wdd->wd_data;
 102         unsigned int timeout_ms = wdd->timeout * 1000;
 103         ktime_t keepalive_interval;
 104         ktime_t last_heartbeat, latest_heartbeat;
 105         ktime_t virt_timeout;
 106         unsigned int hw_heartbeat_ms;
 107
 108         if (watchdog_active(wdd))
 109                 virt_timeout = ktime_add(wd_data->last_keepalive,
 110                                          ms_to_ktime(timeout_ms));
 111         else
 112                 virt_timeout = wd_data->open_deadline;
 113
 114         hw_heartbeat_ms = min_not_zero(timeout_ms, wdd->max_hw_heartbeat_ms);
 115         keepalive_interval = ms_to_ktime(hw_heartbeat_ms / 2);
 116
 117         /*
 118          * To ensure that the watchdog times out wdd->timeout seconds
 119          * after the most recent ping from userspace, the last
 120          * worker ping has to come in hw_heartbeat_ms before this timeout.
 121          */
 122         last_heartbeat = ktime_sub(virt_timeout, ms_to_ktime(hw_heartbeat_ms));
 123         latest_heartbeat = ktime_sub(last_heartbeat, ktime_get());
 124         if (ktime_before(latest_heartbeat, keepalive_interval))
 125                 return latest_heartbeat;
 126         return keepalive_interval;
 127 }
 128
 129 static inline void watchdog_update_worker(struct watchdog_device *wdd)
 130 {
 131         struct watchdog_core_data *wd_data = wdd->wd_data;
 132
 133         if (watchdog_need_worker(wdd)) {
 134                 ktime_t t = watchdog_next_keepalive(wdd);
 135
 136                 if (t > 0)
 137                         hrtimer_start(&wd_data->timer, t,
 138                                       HRTIMER_MODE_REL_HARD);
 139         } else {
 140                 hrtimer_cancel(&wd_data->timer);
 141         }
 142 }
 143
 144 static int __watchdog_ping(struct watchdog_device *wdd)
 145 {
 146         struct watchdog_core_data *wd_data = wdd->wd_data;
 147         ktime_t earliest_keepalive, now;
 148         int err;
 149
 150         earliest_keepalive = ktime_add(wd_data->last_hw_keepalive,
 151                                        ms_to_ktime(wdd->min_hw_heartbeat_ms));
 152         now = ktime_get();
 153
 154         if (ktime_after(earliest_keepalive, now)) {
 155                 hrtimer_start(&wd_data->timer,
 156                               ktime_sub(earliest_keepalive, now),
 157                               HRTIMER_MODE_REL_HARD);
 158                 return 0;
 159         }
 160
 161         wd_data->last_hw_keepalive = now;
 162
 163         if (wdd->ops->ping) {
 164                 err = wdd->ops->ping(wdd);  /* ping the watchdog */
 165                 trace_watchdog_ping(wdd, err);
 166         } else {
 167                 err = wdd->ops->start(wdd); /* restart watchdog */
 168                 trace_watchdog_start(wdd, err);
 169         }
 170
 171         if (err == 0)
 172                 watchdog_hrtimer_pretimeout_start(wdd);
 173
 174         watchdog_update_worker(wdd);
 175
 176         return err;
 177 }
 178
 179 /*
 180  * watchdog_ping - ping the watchdog
 181  * @wdd: The watchdog device to ping
 182  *
 183  * If the watchdog has no own ping operation then it needs to be
 184  * restarted via the start operation. This wrapper function does
 185  * exactly that.
 186  * We only ping when the watchdog device is running.
 187  * The caller must hold wd_data->lock.
 188  *
 189  * Return: 0 on success, error otherwise.
 190  */
 191 static int watchdog_ping(struct watchdog_device *wdd)
 192 {
 193         struct watchdog_core_data *wd_data = wdd->wd_data;
 194
 195         if (!watchdog_active(wdd) && !watchdog_hw_running(wdd))
 196                 return 0;
 197
 198         set_bit(_WDOG_KEEPALIVE, &wd_data->status);
 199
 200         wd_data->last_keepalive = ktime_get();
 201         return __watchdog_ping(wdd);
 202 }
 203
 204 static bool watchdog_worker_should_ping(struct watchdog_core_data *wd_data)
 205 {
 206         struct watchdog_device *wdd = wd_data->wdd;
 207
 208         if (!wdd)
 209                 return false;
 210
 211         if (watchdog_active(wdd))
 212                 return true;
 213
 214         return watchdog_hw_running(wdd) && !watchdog_past_open_deadline(wd_data);
 215 }
 216
 217 static void watchdog_ping_work(struct kthread_work *work)
 218 {
 219         struct watchdog_core_data *wd_data;
 220
 221         wd_data = container_of(work, struct watchdog_core_data, work);
 222
 223         mutex_lock(&wd_data->lock);
 224         if (watchdog_worker_should_ping(wd_data))
 225                 __watchdog_ping(wd_data->wdd);
 226         mutex_unlock(&wd_data->lock);
 227 }
 228
 229 static enum hrtimer_restart watchdog_timer_expired(struct hrtimer *timer)
 230 {
 231         struct watchdog_core_data *wd_data;
 232
 233         wd_data = container_of(timer, struct watchdog_core_data, timer);
 234
 235         kthread_queue_work(watchdog_kworker, &wd_data->work);
 236         return HRTIMER_NORESTART;
 237 }
 238
 239 /*
 240  * watchdog_start - wrapper to start the watchdog
 241  * @wdd: The watchdog device to start
 242  *
 243  * Start the watchdog if it is not active and mark it active.
 244  * The caller must hold wd_data->lock.
 245  *
 246  * Return: 0 on success or a negative errno code for failure.
 247  */
 248 static int watchdog_start(struct watchdog_device *wdd)
 249 {
 250         struct watchdog_core_data *wd_data = wdd->wd_data;
 251         ktime_t started_at;
 252         int err;
 253
 254         if (watchdog_active(wdd))
 255                 return 0;
 256
 257         set_bit(_WDOG_KEEPALIVE, &wd_data->status);
 258
 259         started_at = ktime_get();
 260         if (watchdog_hw_running(wdd) && wdd->ops->ping) {
 261                 err = __watchdog_ping(wdd);
 262                 if (err == 0) {
 263                         set_bit(WDOG_ACTIVE, &wdd->status);
 264                         watchdog_hrtimer_pretimeout_start(wdd);
 265                 }
 266         } else {
 267                 err = wdd->ops->start(wdd);
 268                 trace_watchdog_start(wdd, err);
 269                 if (err == 0) {
 270                         set_bit(WDOG_ACTIVE, &wdd->status);
 271                         wd_data->last_keepalive = started_at;
 272                         wd_data->last_hw_keepalive = started_at;
 273                         watchdog_update_worker(wdd);
 274                         watchdog_hrtimer_pretimeout_start(wdd);
 275                 }
 276         }
 277
 278         return err;
 279 }
 280
 281 /*
 282  * watchdog_stop - wrapper to stop the watchdog
 283  * @wdd: The watchdog device to stop
 284  *
 285  * Stop the watchdog if it is still active and unmark it active.
 286  * If the 'nowayout' feature was set, the watchdog cannot be stopped.
 287  * The caller must hold wd_data->lock.
 288  *
 289  * Return: 0 on success or a negative errno code for failure.
 290  */
 291 static int watchdog_stop(struct watchdog_device *wdd)
 292 {
 293         int err = 0;
 294
 295         if (!watchdog_active(wdd))
 296                 return 0;
 297
 298         if (test_bit(WDOG_NO_WAY_OUT, &wdd->status)) {
 299                 pr_info("watchdog%d: nowayout prevents watchdog being stopped!\n",
 300                         wdd->id);
 301                 return -EBUSY;
 302         }
 303
 304         if (wdd->ops->stop) {
 305                 clear_bit(WDOG_HW_RUNNING, &wdd->status);
 306                 err = wdd->ops->stop(wdd);
 307                 trace_watchdog_stop(wdd, err);
 308         } else {
 309                 set_bit(WDOG_HW_RUNNING, &wdd->status);
 310         }
 311
 312         if (err == 0) {
 313                 clear_bit(WDOG_ACTIVE, &wdd->status);
 314                 watchdog_update_worker(wdd);
 315                 watchdog_hrtimer_pretimeout_stop(wdd);
 316         }
 317
 318         return err;
 319 }
 320
 321 /*
 322  * watchdog_get_status - wrapper to get the watchdog status
 323  * @wdd: The watchdog device to get the status from
 324  *
 325  * Get the watchdog's status flags.
 326  * The caller must hold wd_data->lock.
 327  *
 328  * Return: watchdog's status flags.
 329  */
 330 static unsigned int watchdog_get_status(struct watchdog_device *wdd)
 331 {
 332         struct watchdog_core_data *wd_data = wdd->wd_data;
 333         unsigned int status;
 334
 335         if (wdd->ops->status)
 336                 status = wdd->ops->status(wdd);
 337         else
 338                 status = wdd->bootstatus & (WDIOF_CARDRESET |
 339                                             WDIOF_OVERHEAT |
 340                                             WDIOF_FANFAULT |
 341                                             WDIOF_EXTERN1 |
 342                                             WDIOF_EXTERN2 |
 343                                             WDIOF_POWERUNDER |
 344                                             WDIOF_POWEROVER);
 345
 346         if (test_bit(_WDOG_ALLOW_RELEASE, &wd_data->status))
 347                 status |= WDIOF_MAGICCLOSE;
 348
 349         if (test_and_clear_bit(_WDOG_KEEPALIVE, &wd_data->status))
 350                 status |= WDIOF_KEEPALIVEPING;
 351
 352         if (IS_ENABLED(CONFIG_WATCHDOG_HRTIMER_PRETIMEOUT))
 353                 status |= WDIOF_PRETIMEOUT;
 354
 355         return status;
 356 }
 357
 358 /*
 359  * watchdog_set_timeout - set the watchdog timer timeout
 360  * @wdd:        The watchdog device to set the timeout for
 361  * @timeout:    Timeout to set in seconds
 362  *
 363  * The caller must hold wd_data->lock.
 364  *
 365  * Return: 0 if successful, error otherwise.
 366  */
 367 static int watchdog_set_timeout(struct watchdog_device *wdd,
 368                                                         unsigned int timeout)
 369 {
 370         int err = 0;
 371
 372         if (!(wdd->info->options & WDIOF_SETTIMEOUT))
 373                 return -EOPNOTSUPP;
 374
 375         if (watchdog_timeout_invalid(wdd, timeout))
 376                 return -EINVAL;
 377
 378         if (wdd->ops->set_timeout) {
 379                 err = wdd->ops->set_timeout(wdd, timeout);
 380                 trace_watchdog_set_timeout(wdd, timeout, err);
 381         } else {
 382                 wdd->timeout = timeout;
 383                 /* Disable pretimeout if it doesn't fit the new timeout */
 384                 if (wdd->pretimeout >= wdd->timeout)
 385                         wdd->pretimeout = 0;
 386         }
 387
 388         watchdog_update_worker(wdd);
 389
 390         return err;
 391 }
 392
 393 /*
 394  * watchdog_set_pretimeout - set the watchdog timer pretimeout
 395  * @wdd:        The watchdog device to set the timeout for
 396  * @timeout:    pretimeout to set in seconds
 397  *
 398  * Return: 0 if successful, error otherwise.
 399  */
 400 static int watchdog_set_pretimeout(struct watchdog_device *wdd,
 401                                    unsigned int timeout)
 402 {
 403         int err = 0;
 404
 405         if (!watchdog_have_pretimeout(wdd))
 406                 return -EOPNOTSUPP;
 407
 408         if (watchdog_pretimeout_invalid(wdd, timeout))
 409                 return -EINVAL;
 410
 411         if (wdd->ops->set_pretimeout && (wdd->info->options & WDIOF_PRETIMEOUT))
 412                 err = wdd->ops->set_pretimeout(wdd, timeout);
 413         else
 414                 wdd->pretimeout = timeout;
 415
 416         return err;
 417 }
 418
 419 /*
 420  * watchdog_get_timeleft - wrapper to get the time left before a reboot
 421  * @wdd:        The watchdog device to get the remaining time from
 422  * @timeleft:   The time that's left
 423  *
 424  * Get the time before a watchdog will reboot (if not pinged).
 425  * The caller must hold wd_data->lock.
 426  *
 427  * Return: 0 if successful, error otherwise.
 428  */
 429 static int watchdog_get_timeleft(struct watchdog_device *wdd,
 430                                                         unsigned int *timeleft)
 431 {
 432         *timeleft = 0;
 433
 434         if (!wdd->ops->get_timeleft)
 435                 return -EOPNOTSUPP;
 436
 437         *timeleft = wdd->ops->get_timeleft(wdd);
 438
 439         return 0;
 440 }
 441
 442 #ifdef CONFIG_WATCHDOG_SYSFS
 443 static ssize_t nowayout_show(struct device *dev, struct device_attribute *attr,
 444                                 char *buf)
 445 {
 446         struct watchdog_device *wdd = dev_get_drvdata(dev);
 447
 448         return sysfs_emit(buf, "%d\n", !!test_bit(WDOG_NO_WAY_OUT,
 449                                                   &wdd->status));
 450 }
 451
 452 static ssize_t nowayout_store(struct device *dev, struct device_attribute *attr,
 453                                 const char *buf, size_t len)
 454 {
 455         struct watchdog_device *wdd = dev_get_drvdata(dev);
 456         unsigned int value;
 457         int ret;
 458
 459         ret = kstrtouint(buf, 0, &value);
 460         if (ret)
 461                 return ret;
 462         if (value > 1)
 463                 return -EINVAL;
 464         /* nowayout cannot be disabled once set */
 465         if (test_bit(WDOG_NO_WAY_OUT, &wdd->status) && !value)
 466                 return -EPERM;
 467         watchdog_set_nowayout(wdd, value);
 468         return len;
 469 }
 470 static DEVICE_ATTR_RW(nowayout);
 471
 472 static ssize_t status_show(struct device *dev, struct device_attribute *attr,
 473                                 char *buf)
 474 {
 475         struct watchdog_device *wdd = dev_get_drvdata(dev);
 476         struct watchdog_core_data *wd_data = wdd->wd_data;
 477         unsigned int status;
 478
 479         mutex_lock(&wd_data->lock);
 480         status = watchdog_get_status(wdd);
 481         mutex_unlock(&wd_data->lock);
 482
 483         return sysfs_emit(buf, "0x%x\n", status);
 484 }
 485 static DEVICE_ATTR_RO(status);
 486
 487 static ssize_t bootstatus_show(struct device *dev,
 488                                 struct device_attribute *attr, char *buf)
 489 {
 490         struct watchdog_device *wdd = dev_get_drvdata(dev);
 491
 492         return sysfs_emit(buf, "%u\n", wdd->bootstatus);
 493 }
 494 static DEVICE_ATTR_RO(bootstatus);
 495
 496 static ssize_t timeleft_show(struct device *dev, struct device_attribute *attr,
 497                                 char *buf)
 498 {
 499         struct watchdog_device *wdd = dev_get_drvdata(dev);
 500         struct watchdog_core_data *wd_data = wdd->wd_data;
 501         ssize_t status;
 502         unsigned int val;
 503
 504         mutex_lock(&wd_data->lock);
 505         status = watchdog_get_timeleft(wdd, &val);
 506         mutex_unlock(&wd_data->lock);
 507         if (!status)
 508                 status = sysfs_emit(buf, "%u\n", val);
 509
 510         return status;
 511 }
 512 static DEVICE_ATTR_RO(timeleft);
 513
 514 static ssize_t timeout_show(struct device *dev, struct device_attribute *attr,
 515                                 char *buf)
 516 {
 517         struct watchdog_device *wdd = dev_get_drvdata(dev);
 518
 519         return sysfs_emit(buf, "%u\n", wdd->timeout);
 520 }
 521 static DEVICE_ATTR_RO(timeout);
 522
 523 static ssize_t min_timeout_show(struct device *dev,
 524                                 struct device_attribute *attr, char *buf)
 525 {
 526         struct watchdog_device *wdd = dev_get_drvdata(dev);
 527
 528         return sysfs_emit(buf, "%u\n", wdd->min_timeout);
 529 }
 530 static DEVICE_ATTR_RO(min_timeout);
 531
 532 static ssize_t max_timeout_show(struct device *dev,
 533                                 struct device_attribute *attr, char *buf)
 534 {
 535         struct watchdog_device *wdd = dev_get_drvdata(dev);
 536
 537         return sysfs_emit(buf, "%u\n", wdd->max_timeout);
 538 }
 539 static DEVICE_ATTR_RO(max_timeout);
 540
 541 static ssize_t pretimeout_show(struct device *dev,
 542                                struct device_attribute *attr, char *buf)
 543 {
 544         struct watchdog_device *wdd = dev_get_drvdata(dev);
 545
 546         return sysfs_emit(buf, "%u\n", wdd->pretimeout);
 547 }
 548 static DEVICE_ATTR_RO(pretimeout);
 549
 550 static ssize_t options_show(struct device *dev, struct device_attribute *attr,
 551                             char *buf)
 552 {
 553         struct watchdog_device *wdd = dev_get_drvdata(dev);
 554
 555         return sysfs_emit(buf, "0x%x\n", wdd->info->options);
 556 }
 557 static DEVICE_ATTR_RO(options);
 558
 559 static ssize_t fw_version_show(struct device *dev, struct device_attribute *attr,
 560                                char *buf)
 561 {
 562         struct watchdog_device *wdd = dev_get_drvdata(dev);
 563
 564         return sysfs_emit(buf, "%d\n", wdd->info->firmware_version);
 565 }
 566 static DEVICE_ATTR_RO(fw_version);
 567
 568 static ssize_t identity_show(struct device *dev, struct device_attribute *attr,
 569                                 char *buf)
 570 {
 571         struct watchdog_device *wdd = dev_get_drvdata(dev);
 572
 573         return sysfs_emit(buf, "%s\n", wdd->info->identity);
 574 }
 575 static DEVICE_ATTR_RO(identity);
 576
 577 static ssize_t state_show(struct device *dev, struct device_attribute *attr,
 578                                 char *buf)
 579 {
 580         struct watchdog_device *wdd = dev_get_drvdata(dev);
 581
 582         if (watchdog_active(wdd))
 583                 return sysfs_emit(buf, "active\n");
 584
 585         return sysfs_emit(buf, "inactive\n");
 586 }
 587 static DEVICE_ATTR_RO(state);
 588
 589 static ssize_t pretimeout_available_governors_show(struct device *dev,
 590                                    struct device_attribute *attr, char *buf)
 591 {
 592         return watchdog_pretimeout_available_governors_get(buf);
 593 }
 594 static DEVICE_ATTR_RO(pretimeout_available_governors);
 595
 596 static ssize_t pretimeout_governor_show(struct device *dev,
 597                                         struct device_attribute *attr,
 598                                         char *buf)
 599 {
 600         struct watchdog_device *wdd = dev_get_drvdata(dev);
 601
 602         return watchdog_pretimeout_governor_get(wdd, buf);
 603 }
 604
 605 static ssize_t pretimeout_governor_store(struct device *dev,
 606                                          struct device_attribute *attr,
 607                                          const char *buf, size_t count)
 608 {
 609         struct watchdog_device *wdd = dev_get_drvdata(dev);
 610         int ret = watchdog_pretimeout_governor_set(wdd, buf);
 611
 612         if (!ret)
 613                 ret = count;
 614
 615         return ret;
 616 }
 617 static DEVICE_ATTR_RW(pretimeout_governor);
 618
 619 static umode_t wdt_is_visible(struct kobject *kobj, struct attribute *attr,
 620                                 int n)
 621 {
 622         struct device *dev = kobj_to_dev(kobj);
 623         struct watchdog_device *wdd = dev_get_drvdata(dev);
 624         umode_t mode = attr->mode;
 625
 626         if (attr == &dev_attr_timeleft.attr && !wdd->ops->get_timeleft)
 627                 mode = 0;
 628         else if (attr == &dev_attr_pretimeout.attr && !watchdog_have_pretimeout(wdd))
 629                 mode = 0;
 630         else if ((attr == &dev_attr_pretimeout_governor.attr ||
 631                   attr == &dev_attr_pretimeout_available_governors.attr) &&
 632                  (!watchdog_have_pretimeout(wdd) || !IS_ENABLED(CONFIG_WATCHDOG_PRETIMEOUT_GOV)))
 633                 mode = 0;
 634
 635         return mode;
 636 }
 637 static struct attribute *wdt_attrs[] = {
 638         &dev_attr_state.attr,
 639         &dev_attr_options.attr,
 640         &dev_attr_fw_version.attr,
 641         &dev_attr_identity.attr,
 642         &dev_attr_timeout.attr,
 643         &dev_attr_min_timeout.attr,
 644         &dev_attr_max_timeout.attr,
 645         &dev_attr_pretimeout.attr,
 646         &dev_attr_timeleft.attr,
 647         &dev_attr_bootstatus.attr,
 648         &dev_attr_status.attr,
 649         &dev_attr_nowayout.attr,
 650         &dev_attr_pretimeout_governor.attr,
 651         &dev_attr_pretimeout_available_governors.attr,
 652         NULL,
 653 };
 654
 655 static const struct attribute_group wdt_group = {
 656         .attrs = wdt_attrs,
 657         .is_visible = wdt_is_visible,
 658 };
 659 __ATTRIBUTE_GROUPS(wdt);
 660 #else
 661 #define wdt_groups      NULL
 662 #endif
 663
 664 /*
 665  * watchdog_ioctl_op - call the watchdog drivers ioctl op if defined
 666  * @wdd: The watchdog device to do the ioctl on
 667  * @cmd: Watchdog command
 668  * @arg: Argument pointer
 669  *
 670  * The caller must hold wd_data->lock.
 671  *
 672  * Return: 0 if successful, error otherwise.
 673  */
 674 static int watchdog_ioctl_op(struct watchdog_device *wdd, unsigned int cmd,
 675                                                         unsigned long arg)
 676 {
 677         if (!wdd->ops->ioctl)
 678                 return -ENOIOCTLCMD;
 679
 680         return wdd->ops->ioctl(wdd, cmd, arg);
 681 }
 682
 683 /*
 684  * watchdog_write - writes to the watchdog
 685  * @file:       File from VFS
 686  * @data:       User address of data
 687  * @len:        Length of data
 688  * @ppos:       Pointer to the file offset
 689  *
 690  * A write to a watchdog device is defined as a keepalive ping.
 691  * Writing the magic 'V' sequence allows the next close to turn
 692  * off the watchdog (if 'nowayout' is not set).
 693  *
 694  * Return: @len if successful, error otherwise.
 695  */
 696 static ssize_t watchdog_write(struct file *file, const char __user *data,
 697                                                 size_t len, loff_t *ppos)
 698 {
 699         struct watchdog_core_data *wd_data = file->private_data;
 700         struct watchdog_device *wdd;
 701         int err;
 702         size_t i;
 703         char c;
 704
 705         if (len == 0)
 706                 return 0;
 707
 708         /*
 709          * Note: just in case someone wrote the magic character
 710          * five months ago...
 711          */
 712         clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status);
 713
 714         /* scan to see whether or not we got the magic character */
 715         for (i = 0; i != len; i++) {
 716                 if (get_user(c, data + i))
 717                         return -EFAULT;
 718                 if (c == 'V')
 719                         set_bit(_WDOG_ALLOW_RELEASE, &wd_data->status);
 720         }
 721
 722         /* someone wrote to us, so we send the watchdog a keepalive ping */
 723
 724         err = -ENODEV;
 725         mutex_lock(&wd_data->lock);
 726         wdd = wd_data->wdd;
 727         if (wdd)
 728                 err = watchdog_ping(wdd);
 729         mutex_unlock(&wd_data->lock);
 730
 731         if (err < 0)
 732                 return err;
 733
 734         return len;
 735 }
 736
 737 /*
 738  * watchdog_ioctl - handle the different ioctl's for the watchdog device
 739  * @file:       File handle to the device
 740  * @cmd:        Watchdog command
 741  * @arg:        Argument pointer
 742  *
 743  * The watchdog API defines a common set of functions for all watchdogs
 744  * according to their available features.
 745  *
 746  * Return: 0 if successful, error otherwise.
 747  */
 748
 749 static long watchdog_ioctl(struct file *file, unsigned int cmd,
 750                                                         unsigned long arg)
 751 {
 752         struct watchdog_core_data *wd_data = file->private_data;
 753         void __user *argp = (void __user *)arg;
 754         struct watchdog_device *wdd;
 755         int __user *p = argp;
 756         unsigned int val;
 757         int err;
 758
 759         mutex_lock(&wd_data->lock);
 760
 761         wdd = wd_data->wdd;
 762         if (!wdd) {
 763                 err = -ENODEV;
 764                 goto out_ioctl;
 765         }
 766
 767         err = watchdog_ioctl_op(wdd, cmd, arg);
 768         if (err != -ENOIOCTLCMD)
 769                 goto out_ioctl;
 770
 771         switch (cmd) {
 772         case WDIOC_GETSUPPORT:
 773                 err = copy_to_user(argp, wdd->info,
 774                         sizeof(struct watchdog_info)) ? -EFAULT : 0;
 775                 break;
 776         case WDIOC_GETSTATUS:
 777                 val = watchdog_get_status(wdd);
 778                 err = put_user(val, p);
 779                 break;
 780         case WDIOC_GETBOOTSTATUS:
 781                 err = put_user(wdd->bootstatus, p);
 782                 break;
 783         case WDIOC_SETOPTIONS:
 784                 if (get_user(val, p)) {
 785                         err = -EFAULT;
 786                         break;
 787                 }
 788                 if (val & WDIOS_DISABLECARD) {
 789                         err = watchdog_stop(wdd);
 790                         if (err < 0)
 791                                 break;
 792                 }
 793                 if (val & WDIOS_ENABLECARD)
 794                         err = watchdog_start(wdd);
 795                 break;
 796         case WDIOC_KEEPALIVE:
 797                 if (!(wdd->info->options & WDIOF_KEEPALIVEPING)) {
 798                         err = -EOPNOTSUPP;
 799                         break;
 800                 }
 801                 err = watchdog_ping(wdd);
 802                 break;
 803         case WDIOC_SETTIMEOUT:
 804                 if (get_user(val, p)) {
 805                         err = -EFAULT;
 806                         break;
 807                 }
 808                 err = watchdog_set_timeout(wdd, val);
 809                 if (err < 0)
 810                         break;
 811                 /* If the watchdog is active then we send a keepalive ping
 812                  * to make sure that the watchdog keep's running (and if
 813                  * possible that it takes the new timeout) */
 814                 err = watchdog_ping(wdd);
 815                 if (err < 0)
 816                         break;
 817                 fallthrough;
 818         case WDIOC_GETTIMEOUT:
 819                 /* timeout == 0 means that we don't know the timeout */
 820                 if (wdd->timeout == 0) {
 821                         err = -EOPNOTSUPP;
 822                         break;
 823                 }
 824                 err = put_user(wdd->timeout, p);
 825                 break;
 826         case WDIOC_GETTIMELEFT:
 827                 err = watchdog_get_timeleft(wdd, &val);
 828                 if (err < 0)
 829                         break;
 830                 err = put_user(val, p);
 831                 break;
 832         case WDIOC_SETPRETIMEOUT:
 833                 if (get_user(val, p)) {
 834                         err = -EFAULT;
 835                         break;
 836                 }
 837                 err = watchdog_set_pretimeout(wdd, val);
 838                 break;
 839         case WDIOC_GETPRETIMEOUT:
 840                 err = put_user(wdd->pretimeout, p);
 841                 break;
 842         default:
 843                 err = -ENOTTY;
 844                 break;
 845         }
 846
 847 out_ioctl:
 848         mutex_unlock(&wd_data->lock);
 849         return err;
 850 }
 851
 852 /*
 853  * watchdog_open - open the /dev/watchdog* devices
 854  * @inode:      Inode of device
 855  * @file:       File handle to device
 856  *
 857  * When the /dev/watchdog* device gets opened, we start the watchdog.
 858  * Watch out: the /dev/watchdog device is single open, so we make sure
 859  * it can only be opened once.
 860  *
 861  * Return: 0 if successful, error otherwise.
 862  */
 863 static int watchdog_open(struct inode *inode, struct file *file)
 864 {
 865         struct watchdog_core_data *wd_data;
 866         struct watchdog_device *wdd;
 867         bool hw_running;
 868         int err;
 869
 870         /* Get the corresponding watchdog device */
 871         if (imajor(inode) == MISC_MAJOR)
 872                 wd_data = old_wd_data;
 873         else
 874                 wd_data = container_of(inode->i_cdev, struct watchdog_core_data,
 875                                        cdev);
 876
 877         /* the watchdog is single open! */
 878         if (test_and_set_bit(_WDOG_DEV_OPEN, &wd_data->status))
 879                 return -EBUSY;
 880
 881         wdd = wd_data->wdd;
 882
 883         /*
 884          * If the /dev/watchdog device is open, we don't want the module
 885          * to be unloaded.
 886          */
 887         hw_running = watchdog_hw_running(wdd);
 888         if (!hw_running && !try_module_get(wdd->ops->owner)) {
 889                 err = -EBUSY;
 890                 goto out_clear;
 891         }
 892
 893         err = watchdog_start(wdd);
 894         if (err < 0)
 895                 goto out_mod;
 896
 897         file->private_data = wd_data;
 898
 899         if (!hw_running)
 900                 get_device(&wd_data->dev);
 901
 902         /*
 903          * open_timeout only applies for the first open from
 904          * userspace. Set open_deadline to infinity so that the kernel
 905          * will take care of an always-running hardware watchdog in
 906          * case the device gets magic-closed or WDIOS_DISABLECARD is
 907          * applied.
 908          */
 909         wd_data->open_deadline = KTIME_MAX;
 910
 911         /* dev/watchdog is a virtual (and thus non-seekable) filesystem */
 912         return stream_open(inode, file);
 913
 914 out_mod:
 915         module_put(wd_data->wdd->ops->owner);
 916 out_clear:
 917         clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
 918         return err;
 919 }
 920
 921 static void watchdog_core_data_release(struct device *dev)
 922 {
 923         struct watchdog_core_data *wd_data;
 924
 925         wd_data = container_of(dev, struct watchdog_core_data, dev);
 926
 927         kfree(wd_data);
 928 }
 929
 930 /*
 931  * watchdog_release - release the watchdog device
 932  * @inode:      Inode of device
 933  * @file:       File handle to device
 934  *
 935  * This is the code for when /dev/watchdog gets closed. We will only
 936  * stop the watchdog when we have received the magic char (and nowayout
 937  * was not set), else the watchdog will keep running.
 938  *
 939  * Always returns 0.
 940  */
 941 static int watchdog_release(struct inode *inode, struct file *file)
 942 {
 943         struct watchdog_core_data *wd_data = file->private_data;
 944         struct watchdog_device *wdd;
 945         int err = -EBUSY;
 946         bool running;
 947
 948         mutex_lock(&wd_data->lock);
 949
 950         wdd = wd_data->wdd;
 951         if (!wdd)
 952                 goto done;
 953
 954         /*
 955          * We only stop the watchdog if we received the magic character
 956          * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then
 957          * watchdog_stop will fail.
 958          */
 959         if (!watchdog_active(wdd))
 960                 err = 0;
 961         else if (test_and_clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status) ||
 962                  !(wdd->info->options & WDIOF_MAGICCLOSE))
 963                 err = watchdog_stop(wdd);
 964
 965         /* If the watchdog was not stopped, send a keepalive ping */
 966         if (err < 0) {
 967                 pr_crit("watchdog%d: watchdog did not stop!\n", wdd->id);
 968                 watchdog_ping(wdd);
 969         }
 970
 971         watchdog_update_worker(wdd);
 972
 973         /* make sure that /dev/watchdog can be re-opened */
 974         clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
 975
 976 done:
 977         running = wdd && watchdog_hw_running(wdd);
 978         mutex_unlock(&wd_data->lock);
 979         /*
 980          * Allow the owner module to be unloaded again unless the watchdog
 981          * is still running. If the watchdog is still running, it can not
 982          * be stopped, and its driver must not be unloaded.
 983          */
 984         if (!running) {
 985                 module_put(wd_data->cdev.owner);
 986                 put_device(&wd_data->dev);
 987         }
 988         return 0;
 989 }
 990
 991 static const struct file_operations watchdog_fops = {
 992         .owner          = THIS_MODULE,
 993         .write          = watchdog_write,
 994         .unlocked_ioctl = watchdog_ioctl,
 995         .compat_ioctl   = compat_ptr_ioctl,
 996         .open           = watchdog_open,
 997         .release        = watchdog_release,
 998 };
 999
1000 static struct miscdevice watchdog_miscdev = {
1001         .minor          = WATCHDOG_MINOR,
1002         .name           = "watchdog",
1003         .fops           = &watchdog_fops,
1004 };
1005
1006 static struct class watchdog_class = {
1007         .name =         "watchdog",
1008         .owner =        THIS_MODULE,
1009         .dev_groups =   wdt_groups,
1010 };
1011
1012 /*
1013  * watchdog_cdev_register - register watchdog character device
1014  * @wdd: Watchdog device
1015  *
1016  * Register a watchdog character device including handling the legacy
1017  * /dev/watchdog node. /dev/watchdog is actually a miscdevice and
1018  * thus we set it up like that.
1019  *
1020  * Return: 0 if successful, error otherwise.
1021  */
1022 static int watchdog_cdev_register(struct watchdog_device *wdd)
1023 {
1024         struct watchdog_core_data *wd_data;
1025         int err;
1026
1027         wd_data = kzalloc(sizeof(struct watchdog_core_data), GFP_KERNEL);
1028         if (!wd_data)
1029                 return -ENOMEM;
1030         mutex_init(&wd_data->lock);
1031
1032         wd_data->wdd = wdd;
1033         wdd->wd_data = wd_data;
1034
1035         if (IS_ERR_OR_NULL(watchdog_kworker)) {
1036                 kfree(wd_data);
1037                 return -ENODEV;
1038         }
1039
1040         device_initialize(&wd_data->dev);
1041         wd_data->dev.devt = MKDEV(MAJOR(watchdog_devt), wdd->id);
1042         wd_data->dev.class = &watchdog_class;
1043         wd_data->dev.parent = wdd->parent;
1044         wd_data->dev.groups = wdd->groups;
1045         wd_data->dev.release = watchdog_core_data_release;
1046         dev_set_drvdata(&wd_data->dev, wdd);
1047         err = dev_set_name(&wd_data->dev, "watchdog%d", wdd->id);
1048         if (err) {
1049                 put_device(&wd_data->dev);
1050                 return err;
1051         }
1052
1053         kthread_init_work(&wd_data->work, watchdog_ping_work);
1054         hrtimer_init(&wd_data->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
1055         wd_data->timer.function = watchdog_timer_expired;
1056         watchdog_hrtimer_pretimeout_init(wdd);
1057
1058         if (wdd->id == 0) {
1059                 old_wd_data = wd_data;
1060                 watchdog_miscdev.parent = wdd->parent;
1061                 err = misc_register(&watchdog_miscdev);
1062                 if (err != 0) {
1063                         pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n",
1064                                 wdd->info->identity, WATCHDOG_MINOR, err);
1065                         if (err == -EBUSY)
1066                                 pr_err("%s: a legacy watchdog module is probably present.\n",
1067                                         wdd->info->identity);
1068                         old_wd_data = NULL;
1069                         put_device(&wd_data->dev);
1070                         return err;
1071                 }
1072         }
1073
1074         /* Fill in the data structures */
1075         cdev_init(&wd_data->cdev, &watchdog_fops);
1076
1077         /* Add the device */
1078         err = cdev_device_add(&wd_data->cdev, &wd_data->dev);
1079         if (err) {
1080                 pr_err("watchdog%d unable to add device %d:%d\n",
1081                         wdd->id,  MAJOR(watchdog_devt), wdd->id);
1082                 if (wdd->id == 0) {
1083                         misc_deregister(&watchdog_miscdev);
1084                         old_wd_data = NULL;
1085                 }
1086                 put_device(&wd_data->dev);
1087                 return err;
1088         }
1089
1090         wd_data->cdev.owner = wdd->ops->owner;
1091
1092         /* Record time of most recent heartbeat as 'just before now'. */
1093         wd_data->last_hw_keepalive = ktime_sub(ktime_get(), 1);
1094         watchdog_set_open_deadline(wd_data);
1095
1096         /*
1097          * If the watchdog is running, prevent its driver from being unloaded,
1098          * and schedule an immediate ping.
1099          */
1100         if (watchdog_hw_running(wdd)) {
1101                 __module_get(wdd->ops->owner);
1102                 get_device(&wd_data->dev);
1103                 if (handle_boot_enabled)
1104                         hrtimer_start(&wd_data->timer, 0,
1105                                       HRTIMER_MODE_REL_HARD);
1106                 else
1107                         pr_info("watchdog%d running and kernel based pre-userspace handler disabled\n",
1108                                 wdd->id);
1109         }
1110
1111         return 0;
1112 }
1113
1114 /*
1115  * watchdog_cdev_unregister - unregister watchdog character device
1116  * @wdd: Watchdog device
1117  *
1118  * Unregister watchdog character device and if needed the legacy
1119  * /dev/watchdog device.
1120  */
1121 static void watchdog_cdev_unregister(struct watchdog_device *wdd)
1122 {
1123         struct watchdog_core_data *wd_data = wdd->wd_data;
1124
1125         cdev_device_del(&wd_data->cdev, &wd_data->dev);
1126         if (wdd->id == 0) {
1127                 misc_deregister(&watchdog_miscdev);
1128                 old_wd_data = NULL;
1129         }
1130
1131         if (watchdog_active(wdd) &&
1132             test_bit(WDOG_STOP_ON_UNREGISTER, &wdd->status)) {
1133                 watchdog_stop(wdd);
1134         }
1135
1136         watchdog_hrtimer_pretimeout_stop(wdd);
1137
1138         mutex_lock(&wd_data->lock);
1139         wd_data->wdd = NULL;
1140         wdd->wd_data = NULL;
1141         mutex_unlock(&wd_data->lock);
1142
1143         hrtimer_cancel(&wd_data->timer);
1144         kthread_cancel_work_sync(&wd_data->work);
1145
1146         put_device(&wd_data->dev);
1147 }
1148
1149 /**
1150  * watchdog_dev_register - register a watchdog device
1151  * @wdd: Watchdog device
1152  *
1153  * Register a watchdog device including handling the legacy
1154  * /dev/watchdog node. /dev/watchdog is actually a miscdevice and
1155  * thus we set it up like that.
1156  *
1157  * Return: 0 if successful, error otherwise.
1158  */
1159 int watchdog_dev_register(struct watchdog_device *wdd)
1160 {
1161         int ret;
1162
1163         ret = watchdog_cdev_register(wdd);
1164         if (ret)
1165                 return ret;
1166
1167         ret = watchdog_register_pretimeout(wdd);
1168         if (ret)
1169                 watchdog_cdev_unregister(wdd);
1170
1171         return ret;
1172 }
1173
1174 /**
1175  * watchdog_dev_unregister - unregister a watchdog device
1176  * @wdd: watchdog device
1177  *
1178  * Unregister watchdog device and if needed the legacy
1179  * /dev/watchdog device.
1180  */
1181 void watchdog_dev_unregister(struct watchdog_device *wdd)
1182 {
1183         watchdog_unregister_pretimeout(wdd);
1184         watchdog_cdev_unregister(wdd);
1185 }
1186
1187 /**
1188  * watchdog_set_last_hw_keepalive - set last HW keepalive time for watchdog
1189  * @wdd:                Watchdog device
1190  * @last_ping_ms:       Time since last HW heartbeat
1191  *
1192  * Adjusts the last known HW keepalive time for a watchdog timer.
1193  * This is needed if the watchdog is already running when the probe
1194  * function is called, and it can't be pinged immediately. This
1195  * function must be called immediately after watchdog registration,
1196  * and min_hw_heartbeat_ms must be set for this to be useful.
1197  *
1198  * Return: 0 if successful, error otherwise.
1199  */
1200 int watchdog_set_last_hw_keepalive(struct watchdog_device *wdd,
1201                                    unsigned int last_ping_ms)
1202 {
1203         struct watchdog_core_data *wd_data;
1204         ktime_t now;
1205
1206         if (!wdd)
1207                 return -EINVAL;
1208
1209         wd_data = wdd->wd_data;
1210
1211         now = ktime_get();
1212
1213         wd_data->last_hw_keepalive = ktime_sub(now, ms_to_ktime(last_ping_ms));
1214
1215         if (watchdog_hw_running(wdd) && handle_boot_enabled)
1216                 return __watchdog_ping(wdd);
1217
1218         return 0;
1219 }
1220 EXPORT_SYMBOL_GPL(watchdog_set_last_hw_keepalive);
1221
1222 /**
1223  * watchdog_dev_init - init dev part of watchdog core
1224  *
1225  * Allocate a range of chardev nodes to use for watchdog devices.
1226  *
1227  * Return: 0 if successful, error otherwise.
1228  */
1229 int __init watchdog_dev_init(void)
1230 {
1231         int err;
1232
1233         watchdog_kworker = kthread_create_worker(0, "watchdogd");
1234         if (IS_ERR(watchdog_kworker)) {
1235                 pr_err("Failed to create watchdog kworker\n");
1236                 return PTR_ERR(watchdog_kworker);
1237         }
1238         sched_set_fifo(watchdog_kworker->task);
1239
1240         err = class_register(&watchdog_class);
1241         if (err < 0) {
1242                 pr_err("couldn't register class\n");
1243                 goto err_register;
1244         }
1245
1246         err = alloc_chrdev_region(&watchdog_devt, 0, MAX_DOGS, "watchdog");
1247         if (err < 0) {
1248                 pr_err("watchdog: unable to allocate char dev region\n");
1249                 goto err_alloc;
1250         }
1251
1252         return 0;
1253
1254 err_alloc:
1255         class_unregister(&watchdog_class);
1256 err_register:
1257         kthread_destroy_worker(watchdog_kworker);
1258         return err;
1259 }
1260
1261 /**
1262  * watchdog_dev_exit - exit dev part of watchdog core
1263  *
1264  * Release the range of chardev nodes used for watchdog devices.
1265  */
1266 void __exit watchdog_dev_exit(void)
1267 {
1268         unregister_chrdev_region(watchdog_devt, MAX_DOGS);
1269         class_unregister(&watchdog_class);
1270         kthread_destroy_worker(watchdog_kworker);
1271 }
1272
1273 int watchdog_dev_suspend(struct watchdog_device *wdd)
1274 {
1275         struct watchdog_core_data *wd_data = wdd->wd_data;
1276         int ret = 0;
1277
1278         if (!wdd->wd_data)
1279                 return -ENODEV;
1280
1281         /* ping for the last time before suspend */
1282         mutex_lock(&wd_data->lock);
1283         if (watchdog_worker_should_ping(wd_data))
1284                 ret = __watchdog_ping(wd_data->wdd);
1285         mutex_unlock(&wd_data->lock);
1286
1287         if (ret)
1288                 return ret;
1289
1290         /*
1291          * make sure that watchdog worker will not kick in when the wdog is
1292          * suspended
1293          */
1294         hrtimer_cancel(&wd_data->timer);
1295         kthread_cancel_work_sync(&wd_data->work);
1296
1297         return 0;
1298 }
1299
1300 int watchdog_dev_resume(struct watchdog_device *wdd)
1301 {
1302         struct watchdog_core_data *wd_data = wdd->wd_data;
1303         int ret = 0;
1304
1305         if (!wdd->wd_data)
1306                 return -ENODEV;
1307
1308         /*
1309          * __watchdog_ping will also retrigger hrtimer and therefore restore the
1310          * ping worker if needed.
1311          */
1312         mutex_lock(&wd_data->lock);
1313         if (watchdog_worker_should_ping(wd_data))
1314                 ret = __watchdog_ping(wd_data->wdd);
1315         mutex_unlock(&wd_data->lock);
1316
1317         return ret;
1318 }
1319
1320 module_param(handle_boot_enabled, bool, 0444);
1321 MODULE_PARM_DESC(handle_boot_enabled,
1322         "Watchdog core auto-updates boot enabled watchdogs before userspace takes over (default="
1323         __MODULE_STRING(IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED)) ")");
1324
1325 module_param(open_timeout, uint, 0644);
1326 MODULE_PARM_DESC(open_timeout,
1327         "Maximum time (in seconds, 0 means infinity) for userspace to take over a running watchdog (default="
1328         __MODULE_STRING(CONFIG_WATCHDOG_OPEN_TIMEOUT) ")");