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Wim Van Sebroeck43316042011-07-22 18:55:18 +00001/*
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/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/... */
44
45/* make sure we only register one /dev/watchdog device */
46static unsigned long watchdog_dev_busy;
47/* the watchdog device behind /dev/watchdog */
48static struct watchdog_device *wdd;
49
50/*
51 * watchdog_ping: ping the watchdog.
52 * @wddev: the watchdog device to ping
53 *
54 * If the watchdog has no own ping operation then it needs to be
55 * restarted via the start operation. This wrapper function does
56 * exactly that.
Wim Van Sebroeck234445b2011-07-22 18:57:55 +000057 * We only ping when the watchdog device is running.
Wim Van Sebroeck43316042011-07-22 18:55:18 +000058 */
59
60static int watchdog_ping(struct watchdog_device *wddev)
61{
Wim Van Sebroeck234445b2011-07-22 18:57:55 +000062 if (test_bit(WDOG_ACTIVE, &wdd->status)) {
63 if (wddev->ops->ping)
64 return wddev->ops->ping(wddev); /* ping the watchdog */
65 else
66 return wddev->ops->start(wddev); /* restart watchdog */
67 }
68 return 0;
69}
70
71/*
72 * watchdog_start: wrapper to start the watchdog.
73 * @wddev: the watchdog device to start
74 *
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
77 * failure.
78 */
79
80static int watchdog_start(struct watchdog_device *wddev)
81{
82 int err;
83
84 if (!test_bit(WDOG_ACTIVE, &wdd->status)) {
85 err = wddev->ops->start(wddev);
86 if (err < 0)
87 return err;
88
89 set_bit(WDOG_ACTIVE, &wdd->status);
90 }
91 return 0;
92}
93
94/*
95 * watchdog_stop: wrapper to stop the watchdog.
96 * @wddev: the watchdog device to stop
97 *
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
100 * failure.
Wim Van Sebroeck7e192b92011-07-22 18:59:17 +0000101 * If the 'nowayout' feature was set, the watchdog cannot be stopped.
Wim Van Sebroeck234445b2011-07-22 18:57:55 +0000102 */
103
104static int watchdog_stop(struct watchdog_device *wddev)
105{
Wim Van Sebroeck7e192b92011-07-22 18:59:17 +0000106 int err = -EBUSY;
107
108 if (test_bit(WDOG_NO_WAY_OUT, &wdd->status)) {
109 pr_info("%s: nowayout prevents watchdog to be stopped!\n",
110 wdd->info->identity);
111 return err;
112 }
Wim Van Sebroeck234445b2011-07-22 18:57:55 +0000113
114 if (test_bit(WDOG_ACTIVE, &wdd->status)) {
115 err = wddev->ops->stop(wddev);
116 if (err < 0)
117 return err;
118
119 clear_bit(WDOG_ACTIVE, &wdd->status);
120 }
121 return 0;
Wim Van Sebroeck43316042011-07-22 18:55:18 +0000122}
123
124/*
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
130 *
131 * A write to a watchdog device is defined as a keepalive ping.
Wim Van Sebroeck017cf082011-07-22 18:58:54 +0000132 * Writing the magic 'V' sequence allows the next close to turn
Wim Van Sebroeck7e192b92011-07-22 18:59:17 +0000133 * off the watchdog (if 'nowayout' is not set).
Wim Van Sebroeck43316042011-07-22 18:55:18 +0000134 */
135
136static ssize_t watchdog_write(struct file *file, const char __user *data,
137 size_t len, loff_t *ppos)
138{
139 size_t i;
140 char c;
141
142 if (len == 0)
143 return 0;
144
Wim Van Sebroeck017cf082011-07-22 18:58:54 +0000145 /*
146 * Note: just in case someone wrote the magic character
147 * five months ago...
148 */
149 clear_bit(WDOG_ALLOW_RELEASE, &wdd->status);
150
151 /* scan to see whether or not we got the magic character */
Wim Van Sebroeck43316042011-07-22 18:55:18 +0000152 for (i = 0; i != len; i++) {
153 if (get_user(c, data + i))
154 return -EFAULT;
Wim Van Sebroeck017cf082011-07-22 18:58:54 +0000155 if (c == 'V')
156 set_bit(WDOG_ALLOW_RELEASE, &wdd->status);
Wim Van Sebroeck43316042011-07-22 18:55:18 +0000157 }
158
159 /* someone wrote to us, so we send the watchdog a keepalive ping */
160 watchdog_ping(wdd);
161
162 return len;
163}
164
165/*
Wim Van Sebroeck2fa03562011-07-22 18:56:38 +0000166 * 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
170 *
171 * The watchdog API defines a common set of functions for all watchdogs
172 * according to their available features.
173 */
174
175static long watchdog_ioctl(struct file *file, unsigned int cmd,
176 unsigned long arg)
177{
178 void __user *argp = (void __user *)arg;
179 int __user *p = argp;
180 unsigned int val;
Wim Van Sebroeck234445b2011-07-22 18:57:55 +0000181 int err;
Wim Van Sebroeck2fa03562011-07-22 18:56:38 +0000182
Wim Van Sebroeck78d88fc2011-07-22 18:59:49 +0000183 if (wdd->ops->ioctl) {
184 err = wdd->ops->ioctl(wdd, cmd, arg);
185 if (err != -ENOIOCTLCMD)
186 return err;
187 }
188
Wim Van Sebroeck2fa03562011-07-22 18:56:38 +0000189 switch (cmd) {
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);
Wim Van Sebroeck234445b2011-07-22 18:57:55 +0000198 case WDIOC_SETOPTIONS:
199 if (get_user(val, p))
200 return -EFAULT;
201 if (val & WDIOS_DISABLECARD) {
202 err = watchdog_stop(wdd);
203 if (err < 0)
204 return err;
205 }
206 if (val & WDIOS_ENABLECARD) {
207 err = watchdog_start(wdd);
208 if (err < 0)
209 return err;
210 }
211 return 0;
Wim Van Sebroeckc2dc00e2011-07-22 18:57:23 +0000212 case WDIOC_KEEPALIVE:
213 if (!(wdd->info->options & WDIOF_KEEPALIVEPING))
214 return -EOPNOTSUPP;
215 watchdog_ping(wdd);
216 return 0;
Wim Van Sebroeck014d6942011-07-22 18:58:21 +0000217 case WDIOC_SETTIMEOUT:
218 if ((wdd->ops->set_timeout == NULL) ||
219 !(wdd->info->options & WDIOF_SETTIMEOUT))
220 return -EOPNOTSUPP;
221 if (get_user(val, p))
222 return -EFAULT;
Wim Van Sebroeck3f43f682011-07-22 19:00:16 +0000223 if ((wdd->max_timeout != 0) &&
224 (val < wdd->min_timeout || val > wdd->max_timeout))
225 return -EINVAL;
Wim Van Sebroeck014d6942011-07-22 18:58:21 +0000226 err = wdd->ops->set_timeout(wdd, val);
227 if (err < 0)
228 return err;
229 wdd->timeout = val;
230 /* If the watchdog is active then we send a keepalive ping
231 * to make sure that the watchdog keep's running (and if
232 * possible that it takes the new timeout) */
233 watchdog_ping(wdd);
234 /* Fall */
235 case WDIOC_GETTIMEOUT:
236 /* timeout == 0 means that we don't know the timeout */
237 if (wdd->timeout == 0)
238 return -EOPNOTSUPP;
239 return put_user(wdd->timeout, p);
Wim Van Sebroeck2fa03562011-07-22 18:56:38 +0000240 default:
241 return -ENOTTY;
242 }
243}
244
245/*
Wim Van Sebroeck43316042011-07-22 18:55:18 +0000246 * watchdog_open: open the /dev/watchdog device.
247 * @inode: inode of device
248 * @file: file handle to device
249 *
250 * When the /dev/watchdog device gets opened, we start the watchdog.
251 * Watch out: the /dev/watchdog device is single open, so we make sure
252 * it can only be opened once.
253 */
254
255static int watchdog_open(struct inode *inode, struct file *file)
256{
257 int err = -EBUSY;
258
259 /* the watchdog is single open! */
260 if (test_and_set_bit(WDOG_DEV_OPEN, &wdd->status))
261 return -EBUSY;
262
263 /*
264 * If the /dev/watchdog device is open, we don't want the module
265 * to be unloaded.
266 */
267 if (!try_module_get(wdd->ops->owner))
268 goto out;
269
Wim Van Sebroeck234445b2011-07-22 18:57:55 +0000270 err = watchdog_start(wdd);
Wim Van Sebroeck43316042011-07-22 18:55:18 +0000271 if (err < 0)
272 goto out_mod;
273
274 /* dev/watchdog is a virtual (and thus non-seekable) filesystem */
275 return nonseekable_open(inode, file);
276
277out_mod:
278 module_put(wdd->ops->owner);
279out:
280 clear_bit(WDOG_DEV_OPEN, &wdd->status);
281 return err;
282}
283
284/*
285 * watchdog_release: release the /dev/watchdog device.
286 * @inode: inode of device
287 * @file: file handle to device
288 *
Wim Van Sebroeck017cf082011-07-22 18:58:54 +0000289 * This is the code for when /dev/watchdog gets closed. We will only
Wim Van Sebroeck7e192b92011-07-22 18:59:17 +0000290 * stop the watchdog when we have received the magic char (and nowayout
291 * was not set), else the watchdog will keep running.
Wim Van Sebroeck43316042011-07-22 18:55:18 +0000292 */
293
294static int watchdog_release(struct inode *inode, struct file *file)
295{
Wim Van Sebroeck017cf082011-07-22 18:58:54 +0000296 int err = -EBUSY;
Wim Van Sebroeck43316042011-07-22 18:55:18 +0000297
Wim Van Sebroeck017cf082011-07-22 18:58:54 +0000298 /*
299 * We only stop the watchdog if we received the magic character
Wim Van Sebroeck7e192b92011-07-22 18:59:17 +0000300 * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then
301 * watchdog_stop will fail.
Wim Van Sebroeck017cf082011-07-22 18:58:54 +0000302 */
303 if (test_and_clear_bit(WDOG_ALLOW_RELEASE, &wdd->status) ||
304 !(wdd->info->options & WDIOF_MAGICCLOSE))
305 err = watchdog_stop(wdd);
306
307 /* If the watchdog was not stopped, send a keepalive ping */
Wim Van Sebroeck234445b2011-07-22 18:57:55 +0000308 if (err < 0) {
Wim Van Sebroeck43316042011-07-22 18:55:18 +0000309 pr_crit("%s: watchdog did not stop!\n", wdd->info->identity);
310 watchdog_ping(wdd);
311 }
312
313 /* Allow the owner module to be unloaded again */
314 module_put(wdd->ops->owner);
315
316 /* make sure that /dev/watchdog can be re-opened */
317 clear_bit(WDOG_DEV_OPEN, &wdd->status);
318
319 return 0;
320}
321
322static const struct file_operations watchdog_fops = {
323 .owner = THIS_MODULE,
324 .write = watchdog_write,
Wim Van Sebroeck2fa03562011-07-22 18:56:38 +0000325 .unlocked_ioctl = watchdog_ioctl,
Wim Van Sebroeck43316042011-07-22 18:55:18 +0000326 .open = watchdog_open,
327 .release = watchdog_release,
328};
329
330static struct miscdevice watchdog_miscdev = {
331 .minor = WATCHDOG_MINOR,
332 .name = "watchdog",
333 .fops = &watchdog_fops,
334};
335
336/*
337 * watchdog_dev_register:
338 * @watchdog: watchdog device
339 *
340 * Register a watchdog device as /dev/watchdog. /dev/watchdog
341 * is actually a miscdevice and thus we set it up like that.
342 */
343
344int watchdog_dev_register(struct watchdog_device *watchdog)
345{
346 int err;
347
348 /* Only one device can register for /dev/watchdog */
349 if (test_and_set_bit(0, &watchdog_dev_busy)) {
350 pr_err("only one watchdog can use /dev/watchdog.\n");
351 return -EBUSY;
352 }
353
354 wdd = watchdog;
355
356 err = misc_register(&watchdog_miscdev);
357 if (err != 0) {
358 pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n",
359 watchdog->info->identity, WATCHDOG_MINOR, err);
360 goto out;
361 }
362
363 return 0;
364
365out:
366 wdd = NULL;
367 clear_bit(0, &watchdog_dev_busy);
368 return err;
369}
370
371/*
372 * watchdog_dev_unregister:
373 * @watchdog: watchdog device
374 *
375 * Deregister the /dev/watchdog device.
376 */
377
378int watchdog_dev_unregister(struct watchdog_device *watchdog)
379{
380 /* Check that a watchdog device was registered in the past */
381 if (!test_bit(0, &watchdog_dev_busy) || !wdd)
382 return -ENODEV;
383
384 /* We can only unregister the watchdog device that was registered */
385 if (watchdog != wdd) {
386 pr_err("%s: watchdog was not registered as /dev/watchdog.\n",
387 watchdog->info->identity);
388 return -ENODEV;
389 }
390
391 misc_deregister(&watchdog_miscdev);
392 wdd = NULL;
393 clear_bit(0, &watchdog_dev_busy);
394 return 0;
395}