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/module.h> /* For module stuff/... */
36 #include <linux/types.h> /* For standard types (like size_t) */
37 #include <linux/errno.h> /* For the -ENODEV/... values */
38 #include <linux/kernel.h> /* For printk/panic/... */
39 #include <linux/fs.h> /* For file operations */
40 #include <linux/watchdog.h> /* For watchdog specific items */
41 #include <linux/miscdevice.h> /* For handling misc devices */
42 #include <linux/init.h> /* For __init/__exit/... */
43 #include <linux/uaccess.h> /* For copy_to_user/put_user/... */
45 /* make sure we only register one /dev/watchdog device */
46 static unsigned long watchdog_dev_busy;
47 /* the watchdog device behind /dev/watchdog */
48 static struct watchdog_device *wdd;
51 * watchdog_ping: ping the watchdog.
52 * @wddev: the watchdog device to ping
54 * If the watchdog has no own ping operation then it needs to be
55 * restarted via the start operation. This wrapper function does
57 * We only ping when the watchdog device is running.
60 static int watchdog_ping(struct watchdog_device *wddev)
62 if (test_bit(WDOG_ACTIVE, &wddev->status)) {
64 return wddev->ops->ping(wddev); /* ping the watchdog */
66 return wddev->ops->start(wddev); /* restart watchdog */
72 * watchdog_start: wrapper to start the watchdog.
73 * @wddev: the watchdog device to start
75 * Start the watchdog if it is not active and mark it active.
76 * This function returns zero on success or a negative errno code for
80 static int watchdog_start(struct watchdog_device *wddev)
84 if (!test_bit(WDOG_ACTIVE, &wddev->status)) {
85 err = wddev->ops->start(wddev);
89 set_bit(WDOG_ACTIVE, &wddev->status);
95 * watchdog_stop: wrapper to stop the watchdog.
96 * @wddev: the watchdog device to stop
98 * Stop the watchdog if it is still active and unmark it active.
99 * This function returns zero on success or a negative errno code for
101 * If the 'nowayout' feature was set, the watchdog cannot be stopped.
104 static int watchdog_stop(struct watchdog_device *wddev)
108 if (test_bit(WDOG_NO_WAY_OUT, &wddev->status)) {
109 pr_info("%s: nowayout prevents watchdog to be stopped!\n",
110 wddev->info->identity);
114 if (test_bit(WDOG_ACTIVE, &wddev->status)) {
115 err = wddev->ops->stop(wddev);
119 clear_bit(WDOG_ACTIVE, &wddev->status);
125 * watchdog_write: writes to the watchdog.
126 * @file: file from VFS
127 * @data: user address of data
128 * @len: length of data
129 * @ppos: pointer to the file offset
131 * A write to a watchdog device is defined as a keepalive ping.
132 * Writing the magic 'V' sequence allows the next close to turn
133 * off the watchdog (if 'nowayout' is not set).
136 static ssize_t watchdog_write(struct file *file, const char __user *data,
137 size_t len, loff_t *ppos)
146 * Note: just in case someone wrote the magic character
149 clear_bit(WDOG_ALLOW_RELEASE, &wdd->status);
151 /* scan to see whether or not we got the magic character */
152 for (i = 0; i != len; i++) {
153 if (get_user(c, data + i))
156 set_bit(WDOG_ALLOW_RELEASE, &wdd->status);
159 /* someone wrote to us, so we send the watchdog a keepalive ping */
166 * watchdog_ioctl: handle the different ioctl's for the watchdog device.
167 * @file: file handle to the device
168 * @cmd: watchdog command
169 * @arg: argument pointer
171 * The watchdog API defines a common set of functions for all watchdogs
172 * according to their available features.
175 static long watchdog_ioctl(struct file *file, unsigned int cmd,
178 void __user *argp = (void __user *)arg;
179 int __user *p = argp;
183 if (wdd->ops->ioctl) {
184 err = wdd->ops->ioctl(wdd, cmd, arg);
185 if (err != -ENOIOCTLCMD)
190 case WDIOC_GETSUPPORT:
191 return copy_to_user(argp, wdd->info,
192 sizeof(struct watchdog_info)) ? -EFAULT : 0;
193 case WDIOC_GETSTATUS:
194 val = wdd->ops->status ? wdd->ops->status(wdd) : 0;
195 return put_user(val, p);
196 case WDIOC_GETBOOTSTATUS:
197 return put_user(wdd->bootstatus, p);
198 case WDIOC_SETOPTIONS:
199 if (get_user(val, p))
201 if (val & WDIOS_DISABLECARD) {
202 err = watchdog_stop(wdd);
206 if (val & WDIOS_ENABLECARD) {
207 err = watchdog_start(wdd);
212 case WDIOC_KEEPALIVE:
213 if (!(wdd->info->options & WDIOF_KEEPALIVEPING))
217 case WDIOC_SETTIMEOUT:
218 if ((wdd->ops->set_timeout == NULL) ||
219 !(wdd->info->options & WDIOF_SETTIMEOUT))
221 if (get_user(val, p))
223 if ((wdd->max_timeout != 0) &&
224 (val < wdd->min_timeout || val > wdd->max_timeout))
226 err = wdd->ops->set_timeout(wdd, val);
229 /* If the watchdog is active then we send a keepalive ping
230 * to make sure that the watchdog keep's running (and if
231 * possible that it takes the new timeout) */
234 case WDIOC_GETTIMEOUT:
235 /* timeout == 0 means that we don't know the timeout */
236 if (wdd->timeout == 0)
238 return put_user(wdd->timeout, p);
239 case WDIOC_GETTIMELEFT:
240 if (!wdd->ops->get_timeleft)
243 return put_user(wdd->ops->get_timeleft(wdd), p);
250 * watchdog_open: open the /dev/watchdog device.
251 * @inode: inode of device
252 * @file: file handle to device
254 * When the /dev/watchdog device gets opened, we start the watchdog.
255 * Watch out: the /dev/watchdog device is single open, so we make sure
256 * it can only be opened once.
259 static int watchdog_open(struct inode *inode, struct file *file)
263 /* the watchdog is single open! */
264 if (test_and_set_bit(WDOG_DEV_OPEN, &wdd->status))
268 * If the /dev/watchdog device is open, we don't want the module
271 if (!try_module_get(wdd->ops->owner))
274 err = watchdog_start(wdd);
278 /* dev/watchdog is a virtual (and thus non-seekable) filesystem */
279 return nonseekable_open(inode, file);
282 module_put(wdd->ops->owner);
284 clear_bit(WDOG_DEV_OPEN, &wdd->status);
289 * watchdog_release: release the /dev/watchdog device.
290 * @inode: inode of device
291 * @file: file handle to device
293 * This is the code for when /dev/watchdog gets closed. We will only
294 * stop the watchdog when we have received the magic char (and nowayout
295 * was not set), else the watchdog will keep running.
298 static int watchdog_release(struct inode *inode, struct file *file)
303 * We only stop the watchdog if we received the magic character
304 * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then
305 * watchdog_stop will fail.
307 if (test_and_clear_bit(WDOG_ALLOW_RELEASE, &wdd->status) ||
308 !(wdd->info->options & WDIOF_MAGICCLOSE))
309 err = watchdog_stop(wdd);
311 /* If the watchdog was not stopped, send a keepalive ping */
313 pr_crit("%s: watchdog did not stop!\n", wdd->info->identity);
317 /* Allow the owner module to be unloaded again */
318 module_put(wdd->ops->owner);
320 /* make sure that /dev/watchdog can be re-opened */
321 clear_bit(WDOG_DEV_OPEN, &wdd->status);
326 static const struct file_operations watchdog_fops = {
327 .owner = THIS_MODULE,
328 .write = watchdog_write,
329 .unlocked_ioctl = watchdog_ioctl,
330 .open = watchdog_open,
331 .release = watchdog_release,
334 static struct miscdevice watchdog_miscdev = {
335 .minor = WATCHDOG_MINOR,
337 .fops = &watchdog_fops,
341 * watchdog_dev_register:
342 * @watchdog: watchdog device
344 * Register a watchdog device as /dev/watchdog. /dev/watchdog
345 * is actually a miscdevice and thus we set it up like that.
348 int watchdog_dev_register(struct watchdog_device *watchdog)
352 /* Only one device can register for /dev/watchdog */
353 if (test_and_set_bit(0, &watchdog_dev_busy)) {
354 pr_err("only one watchdog can use /dev/watchdog\n");
360 err = misc_register(&watchdog_miscdev);
362 pr_err("%s: cannot register miscdev on minor=%d (err=%d)\n",
363 watchdog->info->identity, WATCHDOG_MINOR, err);
371 clear_bit(0, &watchdog_dev_busy);
376 * watchdog_dev_unregister:
377 * @watchdog: watchdog device
379 * Deregister the /dev/watchdog device.
382 int watchdog_dev_unregister(struct watchdog_device *watchdog)
384 /* Check that a watchdog device was registered in the past */
385 if (!test_bit(0, &watchdog_dev_busy) || !wdd)
388 /* We can only unregister the watchdog device that was registered */
389 if (watchdog != wdd) {
390 pr_err("%s: watchdog was not registered as /dev/watchdog\n",
391 watchdog->info->identity);
395 misc_deregister(&watchdog_miscdev);
397 clear_bit(0, &watchdog_dev_busy);