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/kernel.h> /* For printk/panic/... */ 40 #include <linux/kref.h> /* For data references */ 41 #include <linux/miscdevice.h> /* For handling misc devices */ 42 #include <linux/module.h> /* For module stuff/... */ 43 #include <linux/mutex.h> /* For mutexes */ 44 #include <linux/slab.h> /* For memory functions */ 45 #include <linux/types.h> /* For standard types (like size_t) */ 46 #include <linux/watchdog.h> /* For watchdog specific items */ 47 #include <linux/uaccess.h> /* For copy_to_user/put_user/... */ 48 49 #include "watchdog_core.h" 50 51 /* 52 * struct watchdog_core_data - watchdog core internal data 53 * @kref: Reference count. 54 * @cdev: The watchdog's Character device. 55 * @wdd: Pointer to watchdog device. 56 * @lock: Lock for watchdog core. 57 * @status: Watchdog core internal status bits. 58 */ 59 struct watchdog_core_data { 60 struct kref kref; 61 struct cdev cdev; 62 struct watchdog_device *wdd; 63 struct mutex lock; 64 unsigned long status; /* Internal status bits */ 65 #define _WDOG_DEV_OPEN 0 /* Opened ? */ 66 #define _WDOG_ALLOW_RELEASE 1 /* Did we receive the magic char ? */ 67 }; 68 69 /* the dev_t structure to store the dynamically allocated watchdog devices */ 70 static dev_t watchdog_devt; 71 /* Reference to watchdog device behind /dev/watchdog */ 72 static struct watchdog_core_data *old_wd_data; 73 74 /* 75 * watchdog_ping: ping the watchdog. 76 * @wdd: the watchdog device to ping 77 * 78 * The caller must hold wd_data->lock. 79 * 80 * If the watchdog has no own ping operation then it needs to be 81 * restarted via the start operation. This wrapper function does 82 * exactly that. 83 * We only ping when the watchdog device is running. 84 */ 85 86 static int watchdog_ping(struct watchdog_device *wdd) 87 { 88 int err; 89 90 if (!watchdog_active(wdd)) 91 return 0; 92 93 if (wdd->ops->ping) 94 err = wdd->ops->ping(wdd); /* ping the watchdog */ 95 else 96 err = wdd->ops->start(wdd); /* restart watchdog */ 97 98 return err; 99 } 100 101 /* 102 * watchdog_start: wrapper to start the watchdog. 103 * @wdd: the watchdog device to start 104 * 105 * The caller must hold wd_data->lock. 106 * 107 * Start the watchdog if it is not active and mark it active. 108 * This function returns zero on success or a negative errno code for 109 * failure. 110 */ 111 112 static int watchdog_start(struct watchdog_device *wdd) 113 { 114 int err; 115 116 if (watchdog_active(wdd)) 117 return 0; 118 119 err = wdd->ops->start(wdd); 120 if (err == 0) 121 set_bit(WDOG_ACTIVE, &wdd->status); 122 123 return err; 124 } 125 126 /* 127 * watchdog_stop: wrapper to stop the watchdog. 128 * @wdd: the watchdog device to stop 129 * 130 * The caller must hold wd_data->lock. 131 * 132 * Stop the watchdog if it is still active and unmark it active. 133 * This function returns zero on success or a negative errno code for 134 * failure. 135 * If the 'nowayout' feature was set, the watchdog cannot be stopped. 136 */ 137 138 static int watchdog_stop(struct watchdog_device *wdd) 139 { 140 int err; 141 142 if (!watchdog_active(wdd)) 143 return 0; 144 145 if (test_bit(WDOG_NO_WAY_OUT, &wdd->status)) { 146 pr_info("watchdog%d: nowayout prevents watchdog being stopped!\n", 147 wdd->id); 148 return -EBUSY; 149 } 150 151 err = wdd->ops->stop(wdd); 152 if (err == 0) 153 clear_bit(WDOG_ACTIVE, &wdd->status); 154 155 return err; 156 } 157 158 /* 159 * watchdog_get_status: wrapper to get the watchdog status 160 * @wdd: the watchdog device to get the status from 161 * 162 * The caller must hold wd_data->lock. 163 * 164 * Get the watchdog's status flags. 165 */ 166 167 static unsigned int watchdog_get_status(struct watchdog_device *wdd) 168 { 169 if (!wdd->ops->status) 170 return 0; 171 172 return wdd->ops->status(wdd); 173 } 174 175 /* 176 * watchdog_set_timeout: set the watchdog timer timeout 177 * @wdd: the watchdog device to set the timeout for 178 * @timeout: timeout to set in seconds 179 * 180 * The caller must hold wd_data->lock. 181 */ 182 183 static int watchdog_set_timeout(struct watchdog_device *wdd, 184 unsigned int timeout) 185 { 186 if (!wdd->ops->set_timeout || !(wdd->info->options & WDIOF_SETTIMEOUT)) 187 return -EOPNOTSUPP; 188 189 if (watchdog_timeout_invalid(wdd, timeout)) 190 return -EINVAL; 191 192 return wdd->ops->set_timeout(wdd, timeout); 193 } 194 195 /* 196 * watchdog_get_timeleft: wrapper to get the time left before a reboot 197 * @wdd: the watchdog device to get the remaining time from 198 * @timeleft: the time that's left 199 * 200 * The caller must hold wd_data->lock. 201 * 202 * Get the time before a watchdog will reboot (if not pinged). 203 */ 204 205 static int watchdog_get_timeleft(struct watchdog_device *wdd, 206 unsigned int *timeleft) 207 { 208 *timeleft = 0; 209 210 if (!wdd->ops->get_timeleft) 211 return -EOPNOTSUPP; 212 213 *timeleft = wdd->ops->get_timeleft(wdd); 214 215 return 0; 216 } 217 218 #ifdef CONFIG_WATCHDOG_SYSFS 219 static ssize_t nowayout_show(struct device *dev, struct device_attribute *attr, 220 char *buf) 221 { 222 struct watchdog_device *wdd = dev_get_drvdata(dev); 223 224 return sprintf(buf, "%d\n", !!test_bit(WDOG_NO_WAY_OUT, &wdd->status)); 225 } 226 static DEVICE_ATTR_RO(nowayout); 227 228 static ssize_t status_show(struct device *dev, struct device_attribute *attr, 229 char *buf) 230 { 231 struct watchdog_device *wdd = dev_get_drvdata(dev); 232 struct watchdog_core_data *wd_data = wdd->wd_data; 233 unsigned int status; 234 235 mutex_lock(&wd_data->lock); 236 status = watchdog_get_status(wdd); 237 mutex_unlock(&wd_data->lock); 238 239 return sprintf(buf, "%u\n", status); 240 } 241 static DEVICE_ATTR_RO(status); 242 243 static ssize_t bootstatus_show(struct device *dev, 244 struct device_attribute *attr, char *buf) 245 { 246 struct watchdog_device *wdd = dev_get_drvdata(dev); 247 248 return sprintf(buf, "%u\n", wdd->bootstatus); 249 } 250 static DEVICE_ATTR_RO(bootstatus); 251 252 static ssize_t timeleft_show(struct device *dev, struct device_attribute *attr, 253 char *buf) 254 { 255 struct watchdog_device *wdd = dev_get_drvdata(dev); 256 struct watchdog_core_data *wd_data = wdd->wd_data; 257 ssize_t status; 258 unsigned int val; 259 260 mutex_lock(&wd_data->lock); 261 status = watchdog_get_timeleft(wdd, &val); 262 mutex_unlock(&wd_data->lock); 263 if (!status) 264 status = sprintf(buf, "%u\n", val); 265 266 return status; 267 } 268 static DEVICE_ATTR_RO(timeleft); 269 270 static ssize_t timeout_show(struct device *dev, struct device_attribute *attr, 271 char *buf) 272 { 273 struct watchdog_device *wdd = dev_get_drvdata(dev); 274 275 return sprintf(buf, "%u\n", wdd->timeout); 276 } 277 static DEVICE_ATTR_RO(timeout); 278 279 static ssize_t identity_show(struct device *dev, struct device_attribute *attr, 280 char *buf) 281 { 282 struct watchdog_device *wdd = dev_get_drvdata(dev); 283 284 return sprintf(buf, "%s\n", wdd->info->identity); 285 } 286 static DEVICE_ATTR_RO(identity); 287 288 static ssize_t state_show(struct device *dev, struct device_attribute *attr, 289 char *buf) 290 { 291 struct watchdog_device *wdd = dev_get_drvdata(dev); 292 293 if (watchdog_active(wdd)) 294 return sprintf(buf, "active\n"); 295 296 return sprintf(buf, "inactive\n"); 297 } 298 static DEVICE_ATTR_RO(state); 299 300 static umode_t wdt_is_visible(struct kobject *kobj, struct attribute *attr, 301 int n) 302 { 303 struct device *dev = container_of(kobj, struct device, kobj); 304 struct watchdog_device *wdd = dev_get_drvdata(dev); 305 umode_t mode = attr->mode; 306 307 if (attr == &dev_attr_status.attr && !wdd->ops->status) 308 mode = 0; 309 else if (attr == &dev_attr_timeleft.attr && !wdd->ops->get_timeleft) 310 mode = 0; 311 312 return mode; 313 } 314 static struct attribute *wdt_attrs[] = { 315 &dev_attr_state.attr, 316 &dev_attr_identity.attr, 317 &dev_attr_timeout.attr, 318 &dev_attr_timeleft.attr, 319 &dev_attr_bootstatus.attr, 320 &dev_attr_status.attr, 321 &dev_attr_nowayout.attr, 322 NULL, 323 }; 324 325 static const struct attribute_group wdt_group = { 326 .attrs = wdt_attrs, 327 .is_visible = wdt_is_visible, 328 }; 329 __ATTRIBUTE_GROUPS(wdt); 330 #else 331 #define wdt_groups NULL 332 #endif 333 334 /* 335 * watchdog_ioctl_op: call the watchdog drivers ioctl op if defined 336 * @wdd: the watchdog device to do the ioctl on 337 * @cmd: watchdog command 338 * @arg: argument pointer 339 * 340 * The caller must hold wd_data->lock. 341 */ 342 343 static int watchdog_ioctl_op(struct watchdog_device *wdd, unsigned int cmd, 344 unsigned long arg) 345 { 346 if (!wdd->ops->ioctl) 347 return -ENOIOCTLCMD; 348 349 return wdd->ops->ioctl(wdd, cmd, arg); 350 } 351 352 /* 353 * watchdog_write: writes to the watchdog. 354 * @file: file from VFS 355 * @data: user address of data 356 * @len: length of data 357 * @ppos: pointer to the file offset 358 * 359 * A write to a watchdog device is defined as a keepalive ping. 360 * Writing the magic 'V' sequence allows the next close to turn 361 * off the watchdog (if 'nowayout' is not set). 362 */ 363 364 static ssize_t watchdog_write(struct file *file, const char __user *data, 365 size_t len, loff_t *ppos) 366 { 367 struct watchdog_core_data *wd_data = file->private_data; 368 struct watchdog_device *wdd; 369 int err; 370 size_t i; 371 char c; 372 373 if (len == 0) 374 return 0; 375 376 /* 377 * Note: just in case someone wrote the magic character 378 * five months ago... 379 */ 380 clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status); 381 382 /* scan to see whether or not we got the magic character */ 383 for (i = 0; i != len; i++) { 384 if (get_user(c, data + i)) 385 return -EFAULT; 386 if (c == 'V') 387 set_bit(_WDOG_ALLOW_RELEASE, &wd_data->status); 388 } 389 390 /* someone wrote to us, so we send the watchdog a keepalive ping */ 391 392 err = -ENODEV; 393 mutex_lock(&wd_data->lock); 394 wdd = wd_data->wdd; 395 if (wdd) 396 err = watchdog_ping(wdd); 397 mutex_unlock(&wd_data->lock); 398 399 if (err < 0) 400 return err; 401 402 return len; 403 } 404 405 /* 406 * watchdog_ioctl: handle the different ioctl's for the watchdog device. 407 * @file: file handle to the device 408 * @cmd: watchdog command 409 * @arg: argument pointer 410 * 411 * The watchdog API defines a common set of functions for all watchdogs 412 * according to their available features. 413 */ 414 415 static long watchdog_ioctl(struct file *file, unsigned int cmd, 416 unsigned long arg) 417 { 418 struct watchdog_core_data *wd_data = file->private_data; 419 void __user *argp = (void __user *)arg; 420 struct watchdog_device *wdd; 421 int __user *p = argp; 422 unsigned int val; 423 int err; 424 425 mutex_lock(&wd_data->lock); 426 427 wdd = wd_data->wdd; 428 if (!wdd) { 429 err = -ENODEV; 430 goto out_ioctl; 431 } 432 433 err = watchdog_ioctl_op(wdd, cmd, arg); 434 if (err != -ENOIOCTLCMD) 435 goto out_ioctl; 436 437 switch (cmd) { 438 case WDIOC_GETSUPPORT: 439 err = copy_to_user(argp, wdd->info, 440 sizeof(struct watchdog_info)) ? -EFAULT : 0; 441 break; 442 case WDIOC_GETSTATUS: 443 val = watchdog_get_status(wdd); 444 err = put_user(val, p); 445 break; 446 case WDIOC_GETBOOTSTATUS: 447 err = put_user(wdd->bootstatus, p); 448 break; 449 case WDIOC_SETOPTIONS: 450 if (get_user(val, p)) { 451 err = -EFAULT; 452 break; 453 } 454 if (val & WDIOS_DISABLECARD) { 455 err = watchdog_stop(wdd); 456 if (err < 0) 457 break; 458 } 459 if (val & WDIOS_ENABLECARD) 460 err = watchdog_start(wdd); 461 break; 462 case WDIOC_KEEPALIVE: 463 if (!(wdd->info->options & WDIOF_KEEPALIVEPING)) { 464 err = -EOPNOTSUPP; 465 break; 466 } 467 err = watchdog_ping(wdd); 468 break; 469 case WDIOC_SETTIMEOUT: 470 if (get_user(val, p)) { 471 err = -EFAULT; 472 break; 473 } 474 err = watchdog_set_timeout(wdd, val); 475 if (err < 0) 476 break; 477 /* If the watchdog is active then we send a keepalive ping 478 * to make sure that the watchdog keep's running (and if 479 * possible that it takes the new timeout) */ 480 err = watchdog_ping(wdd); 481 if (err < 0) 482 break; 483 /* Fall */ 484 case WDIOC_GETTIMEOUT: 485 /* timeout == 0 means that we don't know the timeout */ 486 if (wdd->timeout == 0) { 487 err = -EOPNOTSUPP; 488 break; 489 } 490 err = put_user(wdd->timeout, p); 491 break; 492 case WDIOC_GETTIMELEFT: 493 err = watchdog_get_timeleft(wdd, &val); 494 if (err < 0) 495 break; 496 err = put_user(val, p); 497 break; 498 default: 499 err = -ENOTTY; 500 break; 501 } 502 503 out_ioctl: 504 mutex_unlock(&wd_data->lock); 505 return err; 506 } 507 508 /* 509 * watchdog_open: open the /dev/watchdog* devices. 510 * @inode: inode of device 511 * @file: file handle to device 512 * 513 * When the /dev/watchdog* device gets opened, we start the watchdog. 514 * Watch out: the /dev/watchdog device is single open, so we make sure 515 * it can only be opened once. 516 */ 517 518 static int watchdog_open(struct inode *inode, struct file *file) 519 { 520 struct watchdog_core_data *wd_data; 521 struct watchdog_device *wdd; 522 int err; 523 524 /* Get the corresponding watchdog device */ 525 if (imajor(inode) == MISC_MAJOR) 526 wd_data = old_wd_data; 527 else 528 wd_data = container_of(inode->i_cdev, struct watchdog_core_data, 529 cdev); 530 531 /* the watchdog is single open! */ 532 if (test_and_set_bit(_WDOG_DEV_OPEN, &wd_data->status)) 533 return -EBUSY; 534 535 wdd = wd_data->wdd; 536 537 /* 538 * If the /dev/watchdog device is open, we don't want the module 539 * to be unloaded. 540 */ 541 if (!try_module_get(wdd->ops->owner)) { 542 err = -EBUSY; 543 goto out_clear; 544 } 545 546 err = watchdog_start(wdd); 547 if (err < 0) 548 goto out_mod; 549 550 file->private_data = wd_data; 551 552 kref_get(&wd_data->kref); 553 554 /* dev/watchdog is a virtual (and thus non-seekable) filesystem */ 555 return nonseekable_open(inode, file); 556 557 out_mod: 558 module_put(wd_data->wdd->ops->owner); 559 out_clear: 560 clear_bit(_WDOG_DEV_OPEN, &wd_data->status); 561 return err; 562 } 563 564 static void watchdog_core_data_release(struct kref *kref) 565 { 566 struct watchdog_core_data *wd_data; 567 568 wd_data = container_of(kref, struct watchdog_core_data, kref); 569 570 kfree(wd_data); 571 } 572 573 /* 574 * watchdog_release: release the watchdog device. 575 * @inode: inode of device 576 * @file: file handle to device 577 * 578 * This is the code for when /dev/watchdog gets closed. We will only 579 * stop the watchdog when we have received the magic char (and nowayout 580 * was not set), else the watchdog will keep running. 581 */ 582 583 static int watchdog_release(struct inode *inode, struct file *file) 584 { 585 struct watchdog_core_data *wd_data = file->private_data; 586 struct watchdog_device *wdd; 587 int err = -EBUSY; 588 589 mutex_lock(&wd_data->lock); 590 591 wdd = wd_data->wdd; 592 if (!wdd) 593 goto done; 594 595 /* 596 * We only stop the watchdog if we received the magic character 597 * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then 598 * watchdog_stop will fail. 599 */ 600 if (!test_bit(WDOG_ACTIVE, &wdd->status)) 601 err = 0; 602 else if (test_and_clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status) || 603 !(wdd->info->options & WDIOF_MAGICCLOSE)) 604 err = watchdog_stop(wdd); 605 606 /* If the watchdog was not stopped, send a keepalive ping */ 607 if (err < 0) { 608 pr_crit("watchdog%d: watchdog did not stop!\n", wdd->id); 609 watchdog_ping(wdd); 610 } 611 612 /* make sure that /dev/watchdog can be re-opened */ 613 clear_bit(_WDOG_DEV_OPEN, &wd_data->status); 614 615 done: 616 mutex_unlock(&wd_data->lock); 617 /* Allow the owner module to be unloaded again */ 618 module_put(wd_data->cdev.owner); 619 kref_put(&wd_data->kref, watchdog_core_data_release); 620 return 0; 621 } 622 623 static const struct file_operations watchdog_fops = { 624 .owner = THIS_MODULE, 625 .write = watchdog_write, 626 .unlocked_ioctl = watchdog_ioctl, 627 .open = watchdog_open, 628 .release = watchdog_release, 629 }; 630 631 static struct miscdevice watchdog_miscdev = { 632 .minor = WATCHDOG_MINOR, 633 .name = "watchdog", 634 .fops = &watchdog_fops, 635 }; 636 637 /* 638 * watchdog_cdev_register: register watchdog character device 639 * @wdd: watchdog device 640 * @devno: character device number 641 * 642 * Register a watchdog character device including handling the legacy 643 * /dev/watchdog node. /dev/watchdog is actually a miscdevice and 644 * thus we set it up like that. 645 */ 646 647 static int watchdog_cdev_register(struct watchdog_device *wdd, dev_t devno) 648 { 649 struct watchdog_core_data *wd_data; 650 int err; 651 652 wd_data = kzalloc(sizeof(struct watchdog_core_data), GFP_KERNEL); 653 if (!wd_data) 654 return -ENOMEM; 655 kref_init(&wd_data->kref); 656 mutex_init(&wd_data->lock); 657 658 wd_data->wdd = wdd; 659 wdd->wd_data = wd_data; 660 661 if (wdd->id == 0) { 662 old_wd_data = wd_data; 663 watchdog_miscdev.parent = wdd->parent; 664 err = misc_register(&watchdog_miscdev); 665 if (err != 0) { 666 pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n", 667 wdd->info->identity, WATCHDOG_MINOR, err); 668 if (err == -EBUSY) 669 pr_err("%s: a legacy watchdog module is probably present.\n", 670 wdd->info->identity); 671 old_wd_data = NULL; 672 kfree(wd_data); 673 return err; 674 } 675 } 676 677 /* Fill in the data structures */ 678 cdev_init(&wd_data->cdev, &watchdog_fops); 679 wd_data->cdev.owner = wdd->ops->owner; 680 681 /* Add the device */ 682 err = cdev_add(&wd_data->cdev, devno, 1); 683 if (err) { 684 pr_err("watchdog%d unable to add device %d:%d\n", 685 wdd->id, MAJOR(watchdog_devt), wdd->id); 686 if (wdd->id == 0) { 687 misc_deregister(&watchdog_miscdev); 688 old_wd_data = NULL; 689 kref_put(&wd_data->kref, watchdog_core_data_release); 690 } 691 } 692 return err; 693 } 694 695 /* 696 * watchdog_cdev_unregister: unregister watchdog character device 697 * @watchdog: watchdog device 698 * 699 * Unregister watchdog character device and if needed the legacy 700 * /dev/watchdog device. 701 */ 702 703 static void watchdog_cdev_unregister(struct watchdog_device *wdd) 704 { 705 struct watchdog_core_data *wd_data = wdd->wd_data; 706 707 cdev_del(&wd_data->cdev); 708 if (wdd->id == 0) { 709 misc_deregister(&watchdog_miscdev); 710 old_wd_data = NULL; 711 } 712 713 mutex_lock(&wd_data->lock); 714 wd_data->wdd = NULL; 715 wdd->wd_data = NULL; 716 mutex_unlock(&wd_data->lock); 717 718 kref_put(&wd_data->kref, watchdog_core_data_release); 719 } 720 721 static struct class watchdog_class = { 722 .name = "watchdog", 723 .owner = THIS_MODULE, 724 .dev_groups = wdt_groups, 725 }; 726 727 /* 728 * watchdog_dev_register: register a watchdog device 729 * @wdd: watchdog device 730 * 731 * Register a watchdog device including handling the legacy 732 * /dev/watchdog node. /dev/watchdog is actually a miscdevice and 733 * thus we set it up like that. 734 */ 735 736 int watchdog_dev_register(struct watchdog_device *wdd) 737 { 738 struct device *dev; 739 dev_t devno; 740 int ret; 741 742 devno = MKDEV(MAJOR(watchdog_devt), wdd->id); 743 744 ret = watchdog_cdev_register(wdd, devno); 745 if (ret) 746 return ret; 747 748 dev = device_create_with_groups(&watchdog_class, wdd->parent, 749 devno, wdd, wdd->groups, 750 "watchdog%d", wdd->id); 751 if (IS_ERR(dev)) { 752 watchdog_cdev_unregister(wdd); 753 return PTR_ERR(dev); 754 } 755 756 return ret; 757 } 758 759 /* 760 * watchdog_dev_unregister: unregister a watchdog device 761 * @watchdog: watchdog device 762 * 763 * Unregister watchdog device and if needed the legacy 764 * /dev/watchdog device. 765 */ 766 767 void watchdog_dev_unregister(struct watchdog_device *wdd) 768 { 769 device_destroy(&watchdog_class, wdd->wd_data->cdev.dev); 770 watchdog_cdev_unregister(wdd); 771 } 772 773 /* 774 * watchdog_dev_init: init dev part of watchdog core 775 * 776 * Allocate a range of chardev nodes to use for watchdog devices 777 */ 778 779 int __init watchdog_dev_init(void) 780 { 781 int err; 782 783 err = class_register(&watchdog_class); 784 if (err < 0) { 785 pr_err("couldn't register class\n"); 786 return err; 787 } 788 789 err = alloc_chrdev_region(&watchdog_devt, 0, MAX_DOGS, "watchdog"); 790 if (err < 0) { 791 pr_err("watchdog: unable to allocate char dev region\n"); 792 class_unregister(&watchdog_class); 793 return err; 794 } 795 796 return 0; 797 } 798 799 /* 800 * watchdog_dev_exit: exit dev part of watchdog core 801 * 802 * Release the range of chardev nodes used for watchdog devices 803 */ 804 805 void __exit watchdog_dev_exit(void) 806 { 807 unregister_chrdev_region(watchdog_devt, MAX_DOGS); 808 class_unregister(&watchdog_class); 809 } 810