1 /* 2 * watchdog_dev.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 * 10 * This source code is part of the generic code that can be used 11 * by all the watchdog timer drivers. 12 * 13 * This part of the generic code takes care of the following 14 * misc device: /dev/watchdog. 15 * 16 * Based on source code of the following authors: 17 * Matt Domsch <Matt_Domsch@dell.com>, 18 * Rob Radez <rob@osinvestor.com>, 19 * Rusty Lynch <rusty@linux.co.intel.com> 20 * Satyam Sharma <satyam@infradead.org> 21 * Randy Dunlap <randy.dunlap@oracle.com> 22 * 23 * This program is free software; you can redistribute it and/or 24 * modify it under the terms of the GNU General Public License 25 * as published by the Free Software Foundation; either version 26 * 2 of the License, or (at your option) any later version. 27 * 28 * Neither Alan Cox, CymruNet Ltd., Wim Van Sebroeck nor Iguana vzw. 29 * admit liability nor provide warranty for any of this software. 30 * This material is provided "AS-IS" and at no charge. 31 */ 32 33 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 34 35 #include <linux/cdev.h> /* For character device */ 36 #include <linux/errno.h> /* For the -ENODEV/... values */ 37 #include <linux/fs.h> /* For file operations */ 38 #include <linux/init.h> /* For __init/__exit/... */ 39 #include <linux/jiffies.h> /* For timeout functions */ 40 #include <linux/kernel.h> /* For printk/panic/... */ 41 #include <linux/kref.h> /* For data references */ 42 #include <linux/miscdevice.h> /* For handling misc devices */ 43 #include <linux/module.h> /* For module stuff/... */ 44 #include <linux/mutex.h> /* For mutexes */ 45 #include <linux/slab.h> /* For memory functions */ 46 #include <linux/types.h> /* For standard types (like size_t) */ 47 #include <linux/watchdog.h> /* For watchdog specific items */ 48 #include <linux/workqueue.h> /* For workqueue */ 49 #include <linux/uaccess.h> /* For copy_to_user/put_user/... */ 50 51 #include "watchdog_core.h" 52 53 /* 54 * struct watchdog_core_data - watchdog core internal data 55 * @kref: Reference count. 56 * @cdev: The watchdog's Character device. 57 * @wdd: Pointer to watchdog device. 58 * @lock: Lock for watchdog core. 59 * @status: Watchdog core internal status bits. 60 */ 61 struct watchdog_core_data { 62 struct kref kref; 63 struct cdev cdev; 64 struct watchdog_device *wdd; 65 struct mutex lock; 66 unsigned long last_keepalive; 67 unsigned long last_hw_keepalive; 68 struct delayed_work work; 69 unsigned long status; /* Internal status bits */ 70 #define _WDOG_DEV_OPEN 0 /* Opened ? */ 71 #define _WDOG_ALLOW_RELEASE 1 /* Did we receive the magic char ? */ 72 }; 73 74 /* the dev_t structure to store the dynamically allocated watchdog devices */ 75 static dev_t watchdog_devt; 76 /* Reference to watchdog device behind /dev/watchdog */ 77 static struct watchdog_core_data *old_wd_data; 78 79 static struct workqueue_struct *watchdog_wq; 80 81 static inline bool watchdog_need_worker(struct watchdog_device *wdd) 82 { 83 /* All variables in milli-seconds */ 84 unsigned int hm = wdd->max_hw_heartbeat_ms; 85 unsigned int t = wdd->timeout * 1000; 86 87 /* 88 * A worker to generate heartbeat requests is needed if all of the 89 * following conditions are true. 90 * - Userspace activated the watchdog. 91 * - The driver provided a value for the maximum hardware timeout, and 92 * thus is aware that the framework supports generating heartbeat 93 * requests. 94 * - Userspace requests a longer timeout than the hardware can handle. 95 * 96 * Alternatively, if userspace has not opened the watchdog 97 * device, we take care of feeding the watchdog if it is 98 * running. 99 */ 100 return (hm && watchdog_active(wdd) && t > hm) || 101 (t && !watchdog_active(wdd) && watchdog_hw_running(wdd)); 102 } 103 104 static long watchdog_next_keepalive(struct watchdog_device *wdd) 105 { 106 struct watchdog_core_data *wd_data = wdd->wd_data; 107 unsigned int timeout_ms = wdd->timeout * 1000; 108 unsigned long keepalive_interval; 109 unsigned long last_heartbeat; 110 unsigned long virt_timeout; 111 unsigned int hw_heartbeat_ms; 112 113 virt_timeout = wd_data->last_keepalive + msecs_to_jiffies(timeout_ms); 114 hw_heartbeat_ms = min_not_zero(timeout_ms, wdd->max_hw_heartbeat_ms); 115 keepalive_interval = msecs_to_jiffies(hw_heartbeat_ms / 2); 116 117 if (!watchdog_active(wdd)) 118 return keepalive_interval; 119 120 /* 121 * To ensure that the watchdog times out wdd->timeout seconds 122 * after the most recent ping from userspace, the last 123 * worker ping has to come in hw_heartbeat_ms before this timeout. 124 */ 125 last_heartbeat = virt_timeout - msecs_to_jiffies(hw_heartbeat_ms); 126 return min_t(long, last_heartbeat - jiffies, 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 long t = watchdog_next_keepalive(wdd); 135 136 if (t > 0) 137 mod_delayed_work(watchdog_wq, &wd_data->work, t); 138 } else { 139 cancel_delayed_work(&wd_data->work); 140 } 141 } 142 143 static int __watchdog_ping(struct watchdog_device *wdd) 144 { 145 struct watchdog_core_data *wd_data = wdd->wd_data; 146 unsigned long earliest_keepalive = wd_data->last_hw_keepalive + 147 msecs_to_jiffies(wdd->min_hw_heartbeat_ms); 148 int err; 149 150 if (time_is_after_jiffies(earliest_keepalive)) { 151 mod_delayed_work(watchdog_wq, &wd_data->work, 152 earliest_keepalive - jiffies); 153 return 0; 154 } 155 156 wd_data->last_hw_keepalive = jiffies; 157 158 if (wdd->ops->ping) 159 err = wdd->ops->ping(wdd); /* ping the watchdog */ 160 else 161 err = wdd->ops->start(wdd); /* restart watchdog */ 162 163 watchdog_update_worker(wdd); 164 165 return err; 166 } 167 168 /* 169 * watchdog_ping: ping the watchdog. 170 * @wdd: the watchdog device to ping 171 * 172 * The caller must hold wd_data->lock. 173 * 174 * If the watchdog has no own ping operation then it needs to be 175 * restarted via the start operation. This wrapper function does 176 * exactly that. 177 * We only ping when the watchdog device is running. 178 */ 179 180 static int watchdog_ping(struct watchdog_device *wdd) 181 { 182 struct watchdog_core_data *wd_data = wdd->wd_data; 183 184 if (!watchdog_active(wdd) && !watchdog_hw_running(wdd)) 185 return 0; 186 187 wd_data->last_keepalive = jiffies; 188 return __watchdog_ping(wdd); 189 } 190 191 static void watchdog_ping_work(struct work_struct *work) 192 { 193 struct watchdog_core_data *wd_data; 194 struct watchdog_device *wdd; 195 196 wd_data = container_of(to_delayed_work(work), struct watchdog_core_data, 197 work); 198 199 mutex_lock(&wd_data->lock); 200 wdd = wd_data->wdd; 201 if (wdd && (watchdog_active(wdd) || watchdog_hw_running(wdd))) 202 __watchdog_ping(wdd); 203 mutex_unlock(&wd_data->lock); 204 } 205 206 /* 207 * watchdog_start: wrapper to start the watchdog. 208 * @wdd: the watchdog device to start 209 * 210 * The caller must hold wd_data->lock. 211 * 212 * Start the watchdog if it is not active and mark it active. 213 * This function returns zero on success or a negative errno code for 214 * failure. 215 */ 216 217 static int watchdog_start(struct watchdog_device *wdd) 218 { 219 struct watchdog_core_data *wd_data = wdd->wd_data; 220 unsigned long started_at; 221 int err; 222 223 if (watchdog_active(wdd)) 224 return 0; 225 226 started_at = jiffies; 227 if (watchdog_hw_running(wdd) && wdd->ops->ping) 228 err = wdd->ops->ping(wdd); 229 else 230 err = wdd->ops->start(wdd); 231 if (err == 0) { 232 set_bit(WDOG_ACTIVE, &wdd->status); 233 wd_data->last_keepalive = started_at; 234 watchdog_update_worker(wdd); 235 } 236 237 return err; 238 } 239 240 /* 241 * watchdog_stop: wrapper to stop the watchdog. 242 * @wdd: the watchdog device to stop 243 * 244 * The caller must hold wd_data->lock. 245 * 246 * Stop the watchdog if it is still active and unmark it active. 247 * This function returns zero on success or a negative errno code for 248 * failure. 249 * If the 'nowayout' feature was set, the watchdog cannot be stopped. 250 */ 251 252 static int watchdog_stop(struct watchdog_device *wdd) 253 { 254 int err = 0; 255 256 if (!watchdog_active(wdd)) 257 return 0; 258 259 if (test_bit(WDOG_NO_WAY_OUT, &wdd->status)) { 260 pr_info("watchdog%d: nowayout prevents watchdog being stopped!\n", 261 wdd->id); 262 return -EBUSY; 263 } 264 265 if (wdd->ops->stop) 266 err = wdd->ops->stop(wdd); 267 else 268 set_bit(WDOG_HW_RUNNING, &wdd->status); 269 270 if (err == 0) { 271 clear_bit(WDOG_ACTIVE, &wdd->status); 272 watchdog_update_worker(wdd); 273 } 274 275 return err; 276 } 277 278 /* 279 * watchdog_get_status: wrapper to get the watchdog status 280 * @wdd: the watchdog device to get the status from 281 * 282 * The caller must hold wd_data->lock. 283 * 284 * Get the watchdog's status flags. 285 */ 286 287 static unsigned int watchdog_get_status(struct watchdog_device *wdd) 288 { 289 if (!wdd->ops->status) 290 return 0; 291 292 return wdd->ops->status(wdd); 293 } 294 295 /* 296 * watchdog_set_timeout: set the watchdog timer timeout 297 * @wdd: the watchdog device to set the timeout for 298 * @timeout: timeout to set in seconds 299 * 300 * The caller must hold wd_data->lock. 301 */ 302 303 static int watchdog_set_timeout(struct watchdog_device *wdd, 304 unsigned int timeout) 305 { 306 int err = 0; 307 308 if (!(wdd->info->options & WDIOF_SETTIMEOUT)) 309 return -EOPNOTSUPP; 310 311 if (watchdog_timeout_invalid(wdd, timeout)) 312 return -EINVAL; 313 314 if (wdd->ops->set_timeout) 315 err = wdd->ops->set_timeout(wdd, timeout); 316 else 317 wdd->timeout = timeout; 318 319 watchdog_update_worker(wdd); 320 321 return err; 322 } 323 324 /* 325 * watchdog_get_timeleft: wrapper to get the time left before a reboot 326 * @wdd: the watchdog device to get the remaining time from 327 * @timeleft: the time that's left 328 * 329 * The caller must hold wd_data->lock. 330 * 331 * Get the time before a watchdog will reboot (if not pinged). 332 */ 333 334 static int watchdog_get_timeleft(struct watchdog_device *wdd, 335 unsigned int *timeleft) 336 { 337 *timeleft = 0; 338 339 if (!wdd->ops->get_timeleft) 340 return -EOPNOTSUPP; 341 342 *timeleft = wdd->ops->get_timeleft(wdd); 343 344 return 0; 345 } 346 347 #ifdef CONFIG_WATCHDOG_SYSFS 348 static ssize_t nowayout_show(struct device *dev, struct device_attribute *attr, 349 char *buf) 350 { 351 struct watchdog_device *wdd = dev_get_drvdata(dev); 352 353 return sprintf(buf, "%d\n", !!test_bit(WDOG_NO_WAY_OUT, &wdd->status)); 354 } 355 static DEVICE_ATTR_RO(nowayout); 356 357 static ssize_t status_show(struct device *dev, struct device_attribute *attr, 358 char *buf) 359 { 360 struct watchdog_device *wdd = dev_get_drvdata(dev); 361 struct watchdog_core_data *wd_data = wdd->wd_data; 362 unsigned int status; 363 364 mutex_lock(&wd_data->lock); 365 status = watchdog_get_status(wdd); 366 mutex_unlock(&wd_data->lock); 367 368 return sprintf(buf, "%u\n", status); 369 } 370 static DEVICE_ATTR_RO(status); 371 372 static ssize_t bootstatus_show(struct device *dev, 373 struct device_attribute *attr, char *buf) 374 { 375 struct watchdog_device *wdd = dev_get_drvdata(dev); 376 377 return sprintf(buf, "%u\n", wdd->bootstatus); 378 } 379 static DEVICE_ATTR_RO(bootstatus); 380 381 static ssize_t timeleft_show(struct device *dev, struct device_attribute *attr, 382 char *buf) 383 { 384 struct watchdog_device *wdd = dev_get_drvdata(dev); 385 struct watchdog_core_data *wd_data = wdd->wd_data; 386 ssize_t status; 387 unsigned int val; 388 389 mutex_lock(&wd_data->lock); 390 status = watchdog_get_timeleft(wdd, &val); 391 mutex_unlock(&wd_data->lock); 392 if (!status) 393 status = sprintf(buf, "%u\n", val); 394 395 return status; 396 } 397 static DEVICE_ATTR_RO(timeleft); 398 399 static ssize_t timeout_show(struct device *dev, struct device_attribute *attr, 400 char *buf) 401 { 402 struct watchdog_device *wdd = dev_get_drvdata(dev); 403 404 return sprintf(buf, "%u\n", wdd->timeout); 405 } 406 static DEVICE_ATTR_RO(timeout); 407 408 static ssize_t identity_show(struct device *dev, struct device_attribute *attr, 409 char *buf) 410 { 411 struct watchdog_device *wdd = dev_get_drvdata(dev); 412 413 return sprintf(buf, "%s\n", wdd->info->identity); 414 } 415 static DEVICE_ATTR_RO(identity); 416 417 static ssize_t state_show(struct device *dev, struct device_attribute *attr, 418 char *buf) 419 { 420 struct watchdog_device *wdd = dev_get_drvdata(dev); 421 422 if (watchdog_active(wdd)) 423 return sprintf(buf, "active\n"); 424 425 return sprintf(buf, "inactive\n"); 426 } 427 static DEVICE_ATTR_RO(state); 428 429 static umode_t wdt_is_visible(struct kobject *kobj, struct attribute *attr, 430 int n) 431 { 432 struct device *dev = container_of(kobj, struct device, kobj); 433 struct watchdog_device *wdd = dev_get_drvdata(dev); 434 umode_t mode = attr->mode; 435 436 if (attr == &dev_attr_status.attr && !wdd->ops->status) 437 mode = 0; 438 else if (attr == &dev_attr_timeleft.attr && !wdd->ops->get_timeleft) 439 mode = 0; 440 441 return mode; 442 } 443 static struct attribute *wdt_attrs[] = { 444 &dev_attr_state.attr, 445 &dev_attr_identity.attr, 446 &dev_attr_timeout.attr, 447 &dev_attr_timeleft.attr, 448 &dev_attr_bootstatus.attr, 449 &dev_attr_status.attr, 450 &dev_attr_nowayout.attr, 451 NULL, 452 }; 453 454 static const struct attribute_group wdt_group = { 455 .attrs = wdt_attrs, 456 .is_visible = wdt_is_visible, 457 }; 458 __ATTRIBUTE_GROUPS(wdt); 459 #else 460 #define wdt_groups NULL 461 #endif 462 463 /* 464 * watchdog_ioctl_op: call the watchdog drivers ioctl op if defined 465 * @wdd: the watchdog device to do the ioctl on 466 * @cmd: watchdog command 467 * @arg: argument pointer 468 * 469 * The caller must hold wd_data->lock. 470 */ 471 472 static int watchdog_ioctl_op(struct watchdog_device *wdd, unsigned int cmd, 473 unsigned long arg) 474 { 475 if (!wdd->ops->ioctl) 476 return -ENOIOCTLCMD; 477 478 return wdd->ops->ioctl(wdd, cmd, arg); 479 } 480 481 /* 482 * watchdog_write: writes to the watchdog. 483 * @file: file from VFS 484 * @data: user address of data 485 * @len: length of data 486 * @ppos: pointer to the file offset 487 * 488 * A write to a watchdog device is defined as a keepalive ping. 489 * Writing the magic 'V' sequence allows the next close to turn 490 * off the watchdog (if 'nowayout' is not set). 491 */ 492 493 static ssize_t watchdog_write(struct file *file, const char __user *data, 494 size_t len, loff_t *ppos) 495 { 496 struct watchdog_core_data *wd_data = file->private_data; 497 struct watchdog_device *wdd; 498 int err; 499 size_t i; 500 char c; 501 502 if (len == 0) 503 return 0; 504 505 /* 506 * Note: just in case someone wrote the magic character 507 * five months ago... 508 */ 509 clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status); 510 511 /* scan to see whether or not we got the magic character */ 512 for (i = 0; i != len; i++) { 513 if (get_user(c, data + i)) 514 return -EFAULT; 515 if (c == 'V') 516 set_bit(_WDOG_ALLOW_RELEASE, &wd_data->status); 517 } 518 519 /* someone wrote to us, so we send the watchdog a keepalive ping */ 520 521 err = -ENODEV; 522 mutex_lock(&wd_data->lock); 523 wdd = wd_data->wdd; 524 if (wdd) 525 err = watchdog_ping(wdd); 526 mutex_unlock(&wd_data->lock); 527 528 if (err < 0) 529 return err; 530 531 return len; 532 } 533 534 /* 535 * watchdog_ioctl: handle the different ioctl's for the watchdog device. 536 * @file: file handle to the device 537 * @cmd: watchdog command 538 * @arg: argument pointer 539 * 540 * The watchdog API defines a common set of functions for all watchdogs 541 * according to their available features. 542 */ 543 544 static long watchdog_ioctl(struct file *file, unsigned int cmd, 545 unsigned long arg) 546 { 547 struct watchdog_core_data *wd_data = file->private_data; 548 void __user *argp = (void __user *)arg; 549 struct watchdog_device *wdd; 550 int __user *p = argp; 551 unsigned int val; 552 int err; 553 554 mutex_lock(&wd_data->lock); 555 556 wdd = wd_data->wdd; 557 if (!wdd) { 558 err = -ENODEV; 559 goto out_ioctl; 560 } 561 562 err = watchdog_ioctl_op(wdd, cmd, arg); 563 if (err != -ENOIOCTLCMD) 564 goto out_ioctl; 565 566 switch (cmd) { 567 case WDIOC_GETSUPPORT: 568 err = copy_to_user(argp, wdd->info, 569 sizeof(struct watchdog_info)) ? -EFAULT : 0; 570 break; 571 case WDIOC_GETSTATUS: 572 val = watchdog_get_status(wdd); 573 err = put_user(val, p); 574 break; 575 case WDIOC_GETBOOTSTATUS: 576 err = put_user(wdd->bootstatus, p); 577 break; 578 case WDIOC_SETOPTIONS: 579 if (get_user(val, p)) { 580 err = -EFAULT; 581 break; 582 } 583 if (val & WDIOS_DISABLECARD) { 584 err = watchdog_stop(wdd); 585 if (err < 0) 586 break; 587 } 588 if (val & WDIOS_ENABLECARD) 589 err = watchdog_start(wdd); 590 break; 591 case WDIOC_KEEPALIVE: 592 if (!(wdd->info->options & WDIOF_KEEPALIVEPING)) { 593 err = -EOPNOTSUPP; 594 break; 595 } 596 err = watchdog_ping(wdd); 597 break; 598 case WDIOC_SETTIMEOUT: 599 if (get_user(val, p)) { 600 err = -EFAULT; 601 break; 602 } 603 err = watchdog_set_timeout(wdd, val); 604 if (err < 0) 605 break; 606 /* If the watchdog is active then we send a keepalive ping 607 * to make sure that the watchdog keep's running (and if 608 * possible that it takes the new timeout) */ 609 err = watchdog_ping(wdd); 610 if (err < 0) 611 break; 612 /* Fall */ 613 case WDIOC_GETTIMEOUT: 614 /* timeout == 0 means that we don't know the timeout */ 615 if (wdd->timeout == 0) { 616 err = -EOPNOTSUPP; 617 break; 618 } 619 err = put_user(wdd->timeout, p); 620 break; 621 case WDIOC_GETTIMELEFT: 622 err = watchdog_get_timeleft(wdd, &val); 623 if (err < 0) 624 break; 625 err = put_user(val, p); 626 break; 627 default: 628 err = -ENOTTY; 629 break; 630 } 631 632 out_ioctl: 633 mutex_unlock(&wd_data->lock); 634 return err; 635 } 636 637 /* 638 * watchdog_open: open the /dev/watchdog* devices. 639 * @inode: inode of device 640 * @file: file handle to device 641 * 642 * When the /dev/watchdog* device gets opened, we start the watchdog. 643 * Watch out: the /dev/watchdog device is single open, so we make sure 644 * it can only be opened once. 645 */ 646 647 static int watchdog_open(struct inode *inode, struct file *file) 648 { 649 struct watchdog_core_data *wd_data; 650 struct watchdog_device *wdd; 651 int err; 652 653 /* Get the corresponding watchdog device */ 654 if (imajor(inode) == MISC_MAJOR) 655 wd_data = old_wd_data; 656 else 657 wd_data = container_of(inode->i_cdev, struct watchdog_core_data, 658 cdev); 659 660 /* the watchdog is single open! */ 661 if (test_and_set_bit(_WDOG_DEV_OPEN, &wd_data->status)) 662 return -EBUSY; 663 664 wdd = wd_data->wdd; 665 666 /* 667 * If the /dev/watchdog device is open, we don't want the module 668 * to be unloaded. 669 */ 670 if (!watchdog_hw_running(wdd) && !try_module_get(wdd->ops->owner)) { 671 err = -EBUSY; 672 goto out_clear; 673 } 674 675 err = watchdog_start(wdd); 676 if (err < 0) 677 goto out_mod; 678 679 file->private_data = wd_data; 680 681 if (!watchdog_hw_running(wdd)) 682 kref_get(&wd_data->kref); 683 684 /* dev/watchdog is a virtual (and thus non-seekable) filesystem */ 685 return nonseekable_open(inode, file); 686 687 out_mod: 688 module_put(wd_data->wdd->ops->owner); 689 out_clear: 690 clear_bit(_WDOG_DEV_OPEN, &wd_data->status); 691 return err; 692 } 693 694 static void watchdog_core_data_release(struct kref *kref) 695 { 696 struct watchdog_core_data *wd_data; 697 698 wd_data = container_of(kref, struct watchdog_core_data, kref); 699 700 kfree(wd_data); 701 } 702 703 /* 704 * watchdog_release: release the watchdog device. 705 * @inode: inode of device 706 * @file: file handle to device 707 * 708 * This is the code for when /dev/watchdog gets closed. We will only 709 * stop the watchdog when we have received the magic char (and nowayout 710 * was not set), else the watchdog will keep running. 711 */ 712 713 static int watchdog_release(struct inode *inode, struct file *file) 714 { 715 struct watchdog_core_data *wd_data = file->private_data; 716 struct watchdog_device *wdd; 717 int err = -EBUSY; 718 bool running; 719 720 mutex_lock(&wd_data->lock); 721 722 wdd = wd_data->wdd; 723 if (!wdd) 724 goto done; 725 726 /* 727 * We only stop the watchdog if we received the magic character 728 * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then 729 * watchdog_stop will fail. 730 */ 731 if (!test_bit(WDOG_ACTIVE, &wdd->status)) 732 err = 0; 733 else if (test_and_clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status) || 734 !(wdd->info->options & WDIOF_MAGICCLOSE)) 735 err = watchdog_stop(wdd); 736 737 /* If the watchdog was not stopped, send a keepalive ping */ 738 if (err < 0) { 739 pr_crit("watchdog%d: watchdog did not stop!\n", wdd->id); 740 watchdog_ping(wdd); 741 } 742 743 watchdog_update_worker(wdd); 744 745 /* make sure that /dev/watchdog can be re-opened */ 746 clear_bit(_WDOG_DEV_OPEN, &wd_data->status); 747 748 done: 749 running = wdd && watchdog_hw_running(wdd); 750 mutex_unlock(&wd_data->lock); 751 /* 752 * Allow the owner module to be unloaded again unless the watchdog 753 * is still running. If the watchdog is still running, it can not 754 * be stopped, and its driver must not be unloaded. 755 */ 756 if (!running) { 757 module_put(wd_data->cdev.owner); 758 kref_put(&wd_data->kref, watchdog_core_data_release); 759 } 760 return 0; 761 } 762 763 static const struct file_operations watchdog_fops = { 764 .owner = THIS_MODULE, 765 .write = watchdog_write, 766 .unlocked_ioctl = watchdog_ioctl, 767 .open = watchdog_open, 768 .release = watchdog_release, 769 }; 770 771 static struct miscdevice watchdog_miscdev = { 772 .minor = WATCHDOG_MINOR, 773 .name = "watchdog", 774 .fops = &watchdog_fops, 775 }; 776 777 /* 778 * watchdog_cdev_register: register watchdog character device 779 * @wdd: watchdog device 780 * @devno: character device number 781 * 782 * Register a watchdog character device including handling the legacy 783 * /dev/watchdog node. /dev/watchdog is actually a miscdevice and 784 * thus we set it up like that. 785 */ 786 787 static int watchdog_cdev_register(struct watchdog_device *wdd, dev_t devno) 788 { 789 struct watchdog_core_data *wd_data; 790 int err; 791 792 wd_data = kzalloc(sizeof(struct watchdog_core_data), GFP_KERNEL); 793 if (!wd_data) 794 return -ENOMEM; 795 kref_init(&wd_data->kref); 796 mutex_init(&wd_data->lock); 797 798 wd_data->wdd = wdd; 799 wdd->wd_data = wd_data; 800 801 if (!watchdog_wq) 802 return -ENODEV; 803 804 INIT_DELAYED_WORK(&wd_data->work, watchdog_ping_work); 805 806 if (wdd->id == 0) { 807 old_wd_data = wd_data; 808 watchdog_miscdev.parent = wdd->parent; 809 err = misc_register(&watchdog_miscdev); 810 if (err != 0) { 811 pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n", 812 wdd->info->identity, WATCHDOG_MINOR, err); 813 if (err == -EBUSY) 814 pr_err("%s: a legacy watchdog module is probably present.\n", 815 wdd->info->identity); 816 old_wd_data = NULL; 817 kfree(wd_data); 818 return err; 819 } 820 } 821 822 /* Fill in the data structures */ 823 cdev_init(&wd_data->cdev, &watchdog_fops); 824 wd_data->cdev.owner = wdd->ops->owner; 825 826 /* Add the device */ 827 err = cdev_add(&wd_data->cdev, devno, 1); 828 if (err) { 829 pr_err("watchdog%d unable to add device %d:%d\n", 830 wdd->id, MAJOR(watchdog_devt), wdd->id); 831 if (wdd->id == 0) { 832 misc_deregister(&watchdog_miscdev); 833 old_wd_data = NULL; 834 kref_put(&wd_data->kref, watchdog_core_data_release); 835 } 836 return err; 837 } 838 839 /* Record time of most recent heartbeat as 'just before now'. */ 840 wd_data->last_hw_keepalive = jiffies - 1; 841 842 /* 843 * If the watchdog is running, prevent its driver from being unloaded, 844 * and schedule an immediate ping. 845 */ 846 if (watchdog_hw_running(wdd)) { 847 __module_get(wdd->ops->owner); 848 kref_get(&wd_data->kref); 849 queue_delayed_work(watchdog_wq, &wd_data->work, 0); 850 } 851 852 return 0; 853 } 854 855 /* 856 * watchdog_cdev_unregister: unregister watchdog character device 857 * @watchdog: watchdog device 858 * 859 * Unregister watchdog character device and if needed the legacy 860 * /dev/watchdog device. 861 */ 862 863 static void watchdog_cdev_unregister(struct watchdog_device *wdd) 864 { 865 struct watchdog_core_data *wd_data = wdd->wd_data; 866 867 cdev_del(&wd_data->cdev); 868 if (wdd->id == 0) { 869 misc_deregister(&watchdog_miscdev); 870 old_wd_data = NULL; 871 } 872 873 mutex_lock(&wd_data->lock); 874 wd_data->wdd = NULL; 875 wdd->wd_data = NULL; 876 mutex_unlock(&wd_data->lock); 877 878 cancel_delayed_work_sync(&wd_data->work); 879 880 kref_put(&wd_data->kref, watchdog_core_data_release); 881 } 882 883 static struct class watchdog_class = { 884 .name = "watchdog", 885 .owner = THIS_MODULE, 886 .dev_groups = wdt_groups, 887 }; 888 889 /* 890 * watchdog_dev_register: register a watchdog device 891 * @wdd: watchdog device 892 * 893 * Register a watchdog device including handling the legacy 894 * /dev/watchdog node. /dev/watchdog is actually a miscdevice and 895 * thus we set it up like that. 896 */ 897 898 int watchdog_dev_register(struct watchdog_device *wdd) 899 { 900 struct device *dev; 901 dev_t devno; 902 int ret; 903 904 devno = MKDEV(MAJOR(watchdog_devt), wdd->id); 905 906 ret = watchdog_cdev_register(wdd, devno); 907 if (ret) 908 return ret; 909 910 dev = device_create_with_groups(&watchdog_class, wdd->parent, 911 devno, wdd, wdd->groups, 912 "watchdog%d", wdd->id); 913 if (IS_ERR(dev)) { 914 watchdog_cdev_unregister(wdd); 915 return PTR_ERR(dev); 916 } 917 918 return ret; 919 } 920 921 /* 922 * watchdog_dev_unregister: unregister a watchdog device 923 * @watchdog: watchdog device 924 * 925 * Unregister watchdog device and if needed the legacy 926 * /dev/watchdog device. 927 */ 928 929 void watchdog_dev_unregister(struct watchdog_device *wdd) 930 { 931 device_destroy(&watchdog_class, wdd->wd_data->cdev.dev); 932 watchdog_cdev_unregister(wdd); 933 } 934 935 /* 936 * watchdog_dev_init: init dev part of watchdog core 937 * 938 * Allocate a range of chardev nodes to use for watchdog devices 939 */ 940 941 int __init watchdog_dev_init(void) 942 { 943 int err; 944 945 watchdog_wq = alloc_workqueue("watchdogd", 946 WQ_HIGHPRI | WQ_MEM_RECLAIM, 0); 947 if (!watchdog_wq) { 948 pr_err("Failed to create watchdog workqueue\n"); 949 return -ENOMEM; 950 } 951 952 err = class_register(&watchdog_class); 953 if (err < 0) { 954 pr_err("couldn't register class\n"); 955 return err; 956 } 957 958 err = alloc_chrdev_region(&watchdog_devt, 0, MAX_DOGS, "watchdog"); 959 if (err < 0) { 960 pr_err("watchdog: unable to allocate char dev region\n"); 961 class_unregister(&watchdog_class); 962 return err; 963 } 964 965 return 0; 966 } 967 968 /* 969 * watchdog_dev_exit: exit dev part of watchdog core 970 * 971 * Release the range of chardev nodes used for watchdog devices 972 */ 973 974 void __exit watchdog_dev_exit(void) 975 { 976 unregister_chrdev_region(watchdog_devt, MAX_DOGS); 977 class_unregister(&watchdog_class); 978 destroy_workqueue(watchdog_wq); 979 } 980