4 * (c) Copyright 2008-2011 Alan Cox <alan@lxorguk.ukuu.org.uk>,
7 * (c) Copyright 2008-2011 Wim Van Sebroeck <wim@iguana.be>.
10 * This source code is part of the generic code that can be used
11 * by all the watchdog timer drivers.
13 * This part of the generic code takes care of the following
14 * misc device: /dev/watchdog.
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>
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.
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.
33 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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/... */
49 #include "watchdog_core.h"
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.
59 struct watchdog_core_data {
62 struct watchdog_device *wdd;
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 ? */
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;
75 * watchdog_ping: ping the watchdog.
76 * @wdd: the watchdog device to ping
78 * The caller must hold wd_data->lock.
80 * If the watchdog has no own ping operation then it needs to be
81 * restarted via the start operation. This wrapper function does
83 * We only ping when the watchdog device is running.
86 static int watchdog_ping(struct watchdog_device *wdd)
90 if (!watchdog_active(wdd))
94 err = wdd->ops->ping(wdd); /* ping the watchdog */
96 err = wdd->ops->start(wdd); /* restart watchdog */
102 * watchdog_start: wrapper to start the watchdog.
103 * @wdd: the watchdog device to start
105 * The caller must hold wd_data->lock.
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
112 static int watchdog_start(struct watchdog_device *wdd)
116 if (watchdog_active(wdd))
119 err = wdd->ops->start(wdd);
121 set_bit(WDOG_ACTIVE, &wdd->status);
127 * watchdog_stop: wrapper to stop the watchdog.
128 * @wdd: the watchdog device to stop
130 * The caller must hold wd_data->lock.
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
135 * If the 'nowayout' feature was set, the watchdog cannot be stopped.
138 static int watchdog_stop(struct watchdog_device *wdd)
142 if (!watchdog_active(wdd))
145 if (test_bit(WDOG_NO_WAY_OUT, &wdd->status)) {
146 dev_info(wdd->dev, "nowayout prevents watchdog being stopped!\n");
150 err = wdd->ops->stop(wdd);
152 clear_bit(WDOG_ACTIVE, &wdd->status);
158 * watchdog_get_status: wrapper to get the watchdog status
159 * @wdd: the watchdog device to get the status from
161 * The caller must hold wd_data->lock.
163 * Get the watchdog's status flags.
166 static unsigned int watchdog_get_status(struct watchdog_device *wdd)
168 if (!wdd->ops->status)
171 return wdd->ops->status(wdd);
175 * watchdog_set_timeout: set the watchdog timer timeout
176 * @wdd: the watchdog device to set the timeout for
177 * @timeout: timeout to set in seconds
179 * The caller must hold wd_data->lock.
182 static int watchdog_set_timeout(struct watchdog_device *wdd,
183 unsigned int timeout)
185 if (!wdd->ops->set_timeout || !(wdd->info->options & WDIOF_SETTIMEOUT))
188 if (watchdog_timeout_invalid(wdd, timeout))
191 return wdd->ops->set_timeout(wdd, timeout);
195 * watchdog_get_timeleft: wrapper to get the time left before a reboot
196 * @wdd: the watchdog device to get the remaining time from
197 * @timeleft: the time that's left
199 * The caller must hold wd_data->lock.
201 * Get the time before a watchdog will reboot (if not pinged).
204 static int watchdog_get_timeleft(struct watchdog_device *wdd,
205 unsigned int *timeleft)
209 if (!wdd->ops->get_timeleft)
212 *timeleft = wdd->ops->get_timeleft(wdd);
217 #ifdef CONFIG_WATCHDOG_SYSFS
218 static ssize_t nowayout_show(struct device *dev, struct device_attribute *attr,
221 struct watchdog_device *wdd = dev_get_drvdata(dev);
223 return sprintf(buf, "%d\n", !!test_bit(WDOG_NO_WAY_OUT, &wdd->status));
225 static DEVICE_ATTR_RO(nowayout);
227 static ssize_t status_show(struct device *dev, struct device_attribute *attr,
230 struct watchdog_device *wdd = dev_get_drvdata(dev);
231 struct watchdog_core_data *wd_data = wdd->wd_data;
234 mutex_lock(&wd_data->lock);
235 status = watchdog_get_status(wdd);
236 mutex_unlock(&wd_data->lock);
238 return sprintf(buf, "%u\n", status);
240 static DEVICE_ATTR_RO(status);
242 static ssize_t bootstatus_show(struct device *dev,
243 struct device_attribute *attr, char *buf)
245 struct watchdog_device *wdd = dev_get_drvdata(dev);
247 return sprintf(buf, "%u\n", wdd->bootstatus);
249 static DEVICE_ATTR_RO(bootstatus);
251 static ssize_t timeleft_show(struct device *dev, struct device_attribute *attr,
254 struct watchdog_device *wdd = dev_get_drvdata(dev);
255 struct watchdog_core_data *wd_data = wdd->wd_data;
259 mutex_lock(&wd_data->lock);
260 status = watchdog_get_timeleft(wdd, &val);
261 mutex_unlock(&wd_data->lock);
263 status = sprintf(buf, "%u\n", val);
267 static DEVICE_ATTR_RO(timeleft);
269 static ssize_t timeout_show(struct device *dev, struct device_attribute *attr,
272 struct watchdog_device *wdd = dev_get_drvdata(dev);
274 return sprintf(buf, "%u\n", wdd->timeout);
276 static DEVICE_ATTR_RO(timeout);
278 static ssize_t identity_show(struct device *dev, struct device_attribute *attr,
281 struct watchdog_device *wdd = dev_get_drvdata(dev);
283 return sprintf(buf, "%s\n", wdd->info->identity);
285 static DEVICE_ATTR_RO(identity);
287 static ssize_t state_show(struct device *dev, struct device_attribute *attr,
290 struct watchdog_device *wdd = dev_get_drvdata(dev);
292 if (watchdog_active(wdd))
293 return sprintf(buf, "active\n");
295 return sprintf(buf, "inactive\n");
297 static DEVICE_ATTR_RO(state);
299 static umode_t wdt_is_visible(struct kobject *kobj, struct attribute *attr,
302 struct device *dev = container_of(kobj, struct device, kobj);
303 struct watchdog_device *wdd = dev_get_drvdata(dev);
304 umode_t mode = attr->mode;
306 if (attr == &dev_attr_status.attr && !wdd->ops->status)
308 else if (attr == &dev_attr_timeleft.attr && !wdd->ops->get_timeleft)
313 static struct attribute *wdt_attrs[] = {
314 &dev_attr_state.attr,
315 &dev_attr_identity.attr,
316 &dev_attr_timeout.attr,
317 &dev_attr_timeleft.attr,
318 &dev_attr_bootstatus.attr,
319 &dev_attr_status.attr,
320 &dev_attr_nowayout.attr,
324 static const struct attribute_group wdt_group = {
326 .is_visible = wdt_is_visible,
328 __ATTRIBUTE_GROUPS(wdt);
330 #define wdt_groups NULL
334 * watchdog_ioctl_op: call the watchdog drivers ioctl op if defined
335 * @wdd: the watchdog device to do the ioctl on
336 * @cmd: watchdog command
337 * @arg: argument pointer
339 * The caller must hold wd_data->lock.
342 static int watchdog_ioctl_op(struct watchdog_device *wdd, unsigned int cmd,
345 if (!wdd->ops->ioctl)
348 return wdd->ops->ioctl(wdd, cmd, arg);
352 * watchdog_write: writes to the watchdog.
353 * @file: file from VFS
354 * @data: user address of data
355 * @len: length of data
356 * @ppos: pointer to the file offset
358 * A write to a watchdog device is defined as a keepalive ping.
359 * Writing the magic 'V' sequence allows the next close to turn
360 * off the watchdog (if 'nowayout' is not set).
363 static ssize_t watchdog_write(struct file *file, const char __user *data,
364 size_t len, loff_t *ppos)
366 struct watchdog_core_data *wd_data = file->private_data;
367 struct watchdog_device *wdd;
376 * Note: just in case someone wrote the magic character
379 clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status);
381 /* scan to see whether or not we got the magic character */
382 for (i = 0; i != len; i++) {
383 if (get_user(c, data + i))
386 set_bit(_WDOG_ALLOW_RELEASE, &wd_data->status);
389 /* someone wrote to us, so we send the watchdog a keepalive ping */
392 mutex_lock(&wd_data->lock);
395 err = watchdog_ping(wdd);
396 mutex_unlock(&wd_data->lock);
405 * watchdog_ioctl: handle the different ioctl's for the watchdog device.
406 * @file: file handle to the device
407 * @cmd: watchdog command
408 * @arg: argument pointer
410 * The watchdog API defines a common set of functions for all watchdogs
411 * according to their available features.
414 static long watchdog_ioctl(struct file *file, unsigned int cmd,
417 struct watchdog_core_data *wd_data = file->private_data;
418 void __user *argp = (void __user *)arg;
419 struct watchdog_device *wdd;
420 int __user *p = argp;
424 mutex_lock(&wd_data->lock);
432 err = watchdog_ioctl_op(wdd, cmd, arg);
433 if (err != -ENOIOCTLCMD)
437 case WDIOC_GETSUPPORT:
438 err = copy_to_user(argp, wdd->info,
439 sizeof(struct watchdog_info)) ? -EFAULT : 0;
441 case WDIOC_GETSTATUS:
442 val = watchdog_get_status(wdd);
443 err = put_user(val, p);
445 case WDIOC_GETBOOTSTATUS:
446 err = put_user(wdd->bootstatus, p);
448 case WDIOC_SETOPTIONS:
449 if (get_user(val, p)) {
453 if (val & WDIOS_DISABLECARD) {
454 err = watchdog_stop(wdd);
458 if (val & WDIOS_ENABLECARD)
459 err = watchdog_start(wdd);
461 case WDIOC_KEEPALIVE:
462 if (!(wdd->info->options & WDIOF_KEEPALIVEPING)) {
466 err = watchdog_ping(wdd);
468 case WDIOC_SETTIMEOUT:
469 if (get_user(val, p)) {
473 err = watchdog_set_timeout(wdd, val);
476 /* If the watchdog is active then we send a keepalive ping
477 * to make sure that the watchdog keep's running (and if
478 * possible that it takes the new timeout) */
479 err = watchdog_ping(wdd);
483 case WDIOC_GETTIMEOUT:
484 /* timeout == 0 means that we don't know the timeout */
485 if (wdd->timeout == 0) {
489 err = put_user(wdd->timeout, p);
491 case WDIOC_GETTIMELEFT:
492 err = watchdog_get_timeleft(wdd, &val);
495 err = put_user(val, p);
503 mutex_unlock(&wd_data->lock);
508 * watchdog_open: open the /dev/watchdog* devices.
509 * @inode: inode of device
510 * @file: file handle to device
512 * When the /dev/watchdog* device gets opened, we start the watchdog.
513 * Watch out: the /dev/watchdog device is single open, so we make sure
514 * it can only be opened once.
517 static int watchdog_open(struct inode *inode, struct file *file)
519 struct watchdog_core_data *wd_data;
520 struct watchdog_device *wdd;
523 /* Get the corresponding watchdog device */
524 if (imajor(inode) == MISC_MAJOR)
525 wd_data = old_wd_data;
527 wd_data = container_of(inode->i_cdev, struct watchdog_core_data,
530 /* the watchdog is single open! */
531 if (test_and_set_bit(_WDOG_DEV_OPEN, &wd_data->status))
537 * If the /dev/watchdog device is open, we don't want the module
540 if (!try_module_get(wdd->ops->owner)) {
545 err = watchdog_start(wdd);
549 file->private_data = wd_data;
551 kref_get(&wd_data->kref);
553 /* dev/watchdog is a virtual (and thus non-seekable) filesystem */
554 return nonseekable_open(inode, file);
557 module_put(wd_data->wdd->ops->owner);
559 clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
563 static void watchdog_core_data_release(struct kref *kref)
565 struct watchdog_core_data *wd_data;
567 wd_data = container_of(kref, struct watchdog_core_data, kref);
573 * watchdog_release: release the watchdog device.
574 * @inode: inode of device
575 * @file: file handle to device
577 * This is the code for when /dev/watchdog gets closed. We will only
578 * stop the watchdog when we have received the magic char (and nowayout
579 * was not set), else the watchdog will keep running.
582 static int watchdog_release(struct inode *inode, struct file *file)
584 struct watchdog_core_data *wd_data = file->private_data;
585 struct watchdog_device *wdd;
588 mutex_lock(&wd_data->lock);
595 * We only stop the watchdog if we received the magic character
596 * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then
597 * watchdog_stop will fail.
599 if (!test_bit(WDOG_ACTIVE, &wdd->status))
601 else if (test_and_clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status) ||
602 !(wdd->info->options & WDIOF_MAGICCLOSE))
603 err = watchdog_stop(wdd);
605 /* If the watchdog was not stopped, send a keepalive ping */
607 dev_crit(wdd->dev, "watchdog did not stop!\n");
611 /* make sure that /dev/watchdog can be re-opened */
612 clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
615 mutex_unlock(&wd_data->lock);
616 /* Allow the owner module to be unloaded again */
617 module_put(wd_data->cdev.owner);
618 kref_put(&wd_data->kref, watchdog_core_data_release);
622 static const struct file_operations watchdog_fops = {
623 .owner = THIS_MODULE,
624 .write = watchdog_write,
625 .unlocked_ioctl = watchdog_ioctl,
626 .open = watchdog_open,
627 .release = watchdog_release,
630 static struct miscdevice watchdog_miscdev = {
631 .minor = WATCHDOG_MINOR,
633 .fops = &watchdog_fops,
637 * watchdog_cdev_register: register watchdog character device
638 * @wdd: watchdog device
639 * @devno: character device number
641 * Register a watchdog character device including handling the legacy
642 * /dev/watchdog node. /dev/watchdog is actually a miscdevice and
643 * thus we set it up like that.
646 static int watchdog_cdev_register(struct watchdog_device *wdd, dev_t devno)
648 struct watchdog_core_data *wd_data;
651 wd_data = kzalloc(sizeof(struct watchdog_core_data), GFP_KERNEL);
654 kref_init(&wd_data->kref);
655 mutex_init(&wd_data->lock);
658 wdd->wd_data = wd_data;
661 old_wd_data = wd_data;
662 watchdog_miscdev.parent = wdd->parent;
663 err = misc_register(&watchdog_miscdev);
665 pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n",
666 wdd->info->identity, WATCHDOG_MINOR, err);
668 pr_err("%s: a legacy watchdog module is probably present.\n",
669 wdd->info->identity);
676 /* Fill in the data structures */
677 cdev_init(&wd_data->cdev, &watchdog_fops);
678 wd_data->cdev.owner = wdd->ops->owner;
681 err = cdev_add(&wd_data->cdev, devno, 1);
683 pr_err("watchdog%d unable to add device %d:%d\n",
684 wdd->id, MAJOR(watchdog_devt), wdd->id);
686 misc_deregister(&watchdog_miscdev);
688 kref_put(&wd_data->kref, watchdog_core_data_release);
695 * watchdog_cdev_unregister: unregister watchdog character device
696 * @watchdog: watchdog device
698 * Unregister watchdog character device and if needed the legacy
699 * /dev/watchdog device.
702 static void watchdog_cdev_unregister(struct watchdog_device *wdd)
704 struct watchdog_core_data *wd_data = wdd->wd_data;
706 cdev_del(&wd_data->cdev);
708 misc_deregister(&watchdog_miscdev);
712 mutex_lock(&wd_data->lock);
715 mutex_unlock(&wd_data->lock);
717 kref_put(&wd_data->kref, watchdog_core_data_release);
720 static struct class watchdog_class = {
722 .owner = THIS_MODULE,
723 .dev_groups = wdt_groups,
727 * watchdog_dev_register: register a watchdog device
728 * @wdd: watchdog device
730 * Register a watchdog device including handling the legacy
731 * /dev/watchdog node. /dev/watchdog is actually a miscdevice and
732 * thus we set it up like that.
735 int watchdog_dev_register(struct watchdog_device *wdd)
741 devno = MKDEV(MAJOR(watchdog_devt), wdd->id);
743 ret = watchdog_cdev_register(wdd, devno);
747 dev = device_create(&watchdog_class, wdd->parent, devno, wdd,
748 "watchdog%d", wdd->id);
750 watchdog_cdev_unregister(wdd);
759 * watchdog_dev_unregister: unregister a watchdog device
760 * @watchdog: watchdog device
762 * Unregister watchdog device and if needed the legacy
763 * /dev/watchdog device.
766 void watchdog_dev_unregister(struct watchdog_device *wdd)
768 device_destroy(&watchdog_class, wdd->dev->devt);
770 watchdog_cdev_unregister(wdd);
774 * watchdog_dev_init: init dev part of watchdog core
776 * Allocate a range of chardev nodes to use for watchdog devices
779 int __init watchdog_dev_init(void)
783 err = class_register(&watchdog_class);
785 pr_err("couldn't register class\n");
789 err = alloc_chrdev_region(&watchdog_devt, 0, MAX_DOGS, "watchdog");
791 pr_err("watchdog: unable to allocate char dev region\n");
792 class_unregister(&watchdog_class);
800 * watchdog_dev_exit: exit dev part of watchdog core
802 * Release the range of chardev nodes used for watchdog devices
805 void __exit watchdog_dev_exit(void)
807 unregister_chrdev_region(watchdog_devt, MAX_DOGS);
808 class_unregister(&watchdog_class);