Commit | Line | Data |
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43316044 WVS |
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/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 | ||
6cfb5aa8 | 45 | #include "watchdog_core.h" |
09a46e73 | 46 | |
43316044 WVS |
47 | /* make sure we only register one /dev/watchdog device */ |
48 | static unsigned long watchdog_dev_busy; | |
49 | /* the watchdog device behind /dev/watchdog */ | |
50 | static struct watchdog_device *wdd; | |
51 | ||
52 | /* | |
53 | * watchdog_ping: ping the watchdog. | |
54 | * @wddev: the watchdog device to ping | |
55 | * | |
56 | * If the watchdog has no own ping operation then it needs to be | |
57 | * restarted via the start operation. This wrapper function does | |
58 | * exactly that. | |
234445b4 | 59 | * We only ping when the watchdog device is running. |
43316044 WVS |
60 | */ |
61 | ||
62 | static int watchdog_ping(struct watchdog_device *wddev) | |
63 | { | |
257f8c4a | 64 | if (watchdog_active(wddev)) { |
234445b4 WVS |
65 | if (wddev->ops->ping) |
66 | return wddev->ops->ping(wddev); /* ping the watchdog */ | |
67 | else | |
68 | return wddev->ops->start(wddev); /* restart watchdog */ | |
69 | } | |
70 | return 0; | |
71 | } | |
72 | ||
73 | /* | |
74 | * watchdog_start: wrapper to start the watchdog. | |
75 | * @wddev: the watchdog device to start | |
76 | * | |
77 | * Start the watchdog if it is not active and mark it active. | |
78 | * This function returns zero on success or a negative errno code for | |
79 | * failure. | |
80 | */ | |
81 | ||
82 | static int watchdog_start(struct watchdog_device *wddev) | |
83 | { | |
84 | int err; | |
85 | ||
257f8c4a | 86 | if (!watchdog_active(wddev)) { |
234445b4 WVS |
87 | err = wddev->ops->start(wddev); |
88 | if (err < 0) | |
89 | return err; | |
90 | ||
cb7efc02 | 91 | set_bit(WDOG_ACTIVE, &wddev->status); |
234445b4 WVS |
92 | } |
93 | return 0; | |
94 | } | |
95 | ||
96 | /* | |
97 | * watchdog_stop: wrapper to stop the watchdog. | |
98 | * @wddev: the watchdog device to stop | |
99 | * | |
100 | * Stop the watchdog if it is still active and unmark it active. | |
101 | * This function returns zero on success or a negative errno code for | |
102 | * failure. | |
7e192b9c | 103 | * If the 'nowayout' feature was set, the watchdog cannot be stopped. |
234445b4 WVS |
104 | */ |
105 | ||
106 | static int watchdog_stop(struct watchdog_device *wddev) | |
107 | { | |
7e192b9c WVS |
108 | int err = -EBUSY; |
109 | ||
cb7efc02 | 110 | if (test_bit(WDOG_NO_WAY_OUT, &wddev->status)) { |
7e192b9c | 111 | pr_info("%s: nowayout prevents watchdog to be stopped!\n", |
cb7efc02 | 112 | wddev->info->identity); |
7e192b9c WVS |
113 | return err; |
114 | } | |
234445b4 | 115 | |
257f8c4a | 116 | if (watchdog_active(wddev)) { |
234445b4 WVS |
117 | err = wddev->ops->stop(wddev); |
118 | if (err < 0) | |
119 | return err; | |
120 | ||
cb7efc02 | 121 | clear_bit(WDOG_ACTIVE, &wddev->status); |
234445b4 WVS |
122 | } |
123 | return 0; | |
43316044 WVS |
124 | } |
125 | ||
126 | /* | |
127 | * watchdog_write: writes to the watchdog. | |
128 | * @file: file from VFS | |
129 | * @data: user address of data | |
130 | * @len: length of data | |
131 | * @ppos: pointer to the file offset | |
132 | * | |
133 | * A write to a watchdog device is defined as a keepalive ping. | |
017cf080 | 134 | * Writing the magic 'V' sequence allows the next close to turn |
7e192b9c | 135 | * off the watchdog (if 'nowayout' is not set). |
43316044 WVS |
136 | */ |
137 | ||
138 | static ssize_t watchdog_write(struct file *file, const char __user *data, | |
139 | size_t len, loff_t *ppos) | |
140 | { | |
141 | size_t i; | |
142 | char c; | |
143 | ||
144 | if (len == 0) | |
145 | return 0; | |
146 | ||
017cf080 WVS |
147 | /* |
148 | * Note: just in case someone wrote the magic character | |
149 | * five months ago... | |
150 | */ | |
151 | clear_bit(WDOG_ALLOW_RELEASE, &wdd->status); | |
152 | ||
153 | /* scan to see whether or not we got the magic character */ | |
43316044 WVS |
154 | for (i = 0; i != len; i++) { |
155 | if (get_user(c, data + i)) | |
156 | return -EFAULT; | |
017cf080 WVS |
157 | if (c == 'V') |
158 | set_bit(WDOG_ALLOW_RELEASE, &wdd->status); | |
43316044 WVS |
159 | } |
160 | ||
161 | /* someone wrote to us, so we send the watchdog a keepalive ping */ | |
162 | watchdog_ping(wdd); | |
163 | ||
164 | return len; | |
165 | } | |
166 | ||
2fa03560 WVS |
167 | /* |
168 | * watchdog_ioctl: handle the different ioctl's for the watchdog device. | |
169 | * @file: file handle to the device | |
170 | * @cmd: watchdog command | |
171 | * @arg: argument pointer | |
172 | * | |
173 | * The watchdog API defines a common set of functions for all watchdogs | |
174 | * according to their available features. | |
175 | */ | |
176 | ||
177 | static long watchdog_ioctl(struct file *file, unsigned int cmd, | |
178 | unsigned long arg) | |
179 | { | |
180 | void __user *argp = (void __user *)arg; | |
181 | int __user *p = argp; | |
182 | unsigned int val; | |
234445b4 | 183 | int err; |
2fa03560 | 184 | |
78d88fc0 WVS |
185 | if (wdd->ops->ioctl) { |
186 | err = wdd->ops->ioctl(wdd, cmd, arg); | |
187 | if (err != -ENOIOCTLCMD) | |
188 | return err; | |
189 | } | |
190 | ||
2fa03560 WVS |
191 | switch (cmd) { |
192 | case WDIOC_GETSUPPORT: | |
193 | return copy_to_user(argp, wdd->info, | |
194 | sizeof(struct watchdog_info)) ? -EFAULT : 0; | |
195 | case WDIOC_GETSTATUS: | |
196 | val = wdd->ops->status ? wdd->ops->status(wdd) : 0; | |
197 | return put_user(val, p); | |
198 | case WDIOC_GETBOOTSTATUS: | |
199 | return put_user(wdd->bootstatus, p); | |
234445b4 WVS |
200 | case WDIOC_SETOPTIONS: |
201 | if (get_user(val, p)) | |
202 | return -EFAULT; | |
203 | if (val & WDIOS_DISABLECARD) { | |
204 | err = watchdog_stop(wdd); | |
205 | if (err < 0) | |
206 | return err; | |
207 | } | |
208 | if (val & WDIOS_ENABLECARD) { | |
209 | err = watchdog_start(wdd); | |
210 | if (err < 0) | |
211 | return err; | |
212 | } | |
213 | return 0; | |
c2dc00e4 WVS |
214 | case WDIOC_KEEPALIVE: |
215 | if (!(wdd->info->options & WDIOF_KEEPALIVEPING)) | |
216 | return -EOPNOTSUPP; | |
217 | watchdog_ping(wdd); | |
218 | return 0; | |
014d694e WVS |
219 | case WDIOC_SETTIMEOUT: |
220 | if ((wdd->ops->set_timeout == NULL) || | |
221 | !(wdd->info->options & WDIOF_SETTIMEOUT)) | |
222 | return -EOPNOTSUPP; | |
223 | if (get_user(val, p)) | |
224 | return -EFAULT; | |
3f43f68e WVS |
225 | if ((wdd->max_timeout != 0) && |
226 | (val < wdd->min_timeout || val > wdd->max_timeout)) | |
227 | return -EINVAL; | |
014d694e WVS |
228 | err = wdd->ops->set_timeout(wdd, val); |
229 | if (err < 0) | |
230 | return err; | |
014d694e WVS |
231 | /* If the watchdog is active then we send a keepalive ping |
232 | * to make sure that the watchdog keep's running (and if | |
233 | * possible that it takes the new timeout) */ | |
234 | watchdog_ping(wdd); | |
235 | /* Fall */ | |
236 | case WDIOC_GETTIMEOUT: | |
237 | /* timeout == 0 means that we don't know the timeout */ | |
238 | if (wdd->timeout == 0) | |
239 | return -EOPNOTSUPP; | |
240 | return put_user(wdd->timeout, p); | |
fd7b673c VK |
241 | case WDIOC_GETTIMELEFT: |
242 | if (!wdd->ops->get_timeleft) | |
243 | return -EOPNOTSUPP; | |
244 | ||
245 | return put_user(wdd->ops->get_timeleft(wdd), p); | |
2fa03560 WVS |
246 | default: |
247 | return -ENOTTY; | |
248 | } | |
249 | } | |
250 | ||
43316044 WVS |
251 | /* |
252 | * watchdog_open: open the /dev/watchdog device. | |
253 | * @inode: inode of device | |
254 | * @file: file handle to device | |
255 | * | |
256 | * When the /dev/watchdog device gets opened, we start the watchdog. | |
257 | * Watch out: the /dev/watchdog device is single open, so we make sure | |
258 | * it can only be opened once. | |
259 | */ | |
260 | ||
261 | static int watchdog_open(struct inode *inode, struct file *file) | |
262 | { | |
263 | int err = -EBUSY; | |
264 | ||
265 | /* the watchdog is single open! */ | |
266 | if (test_and_set_bit(WDOG_DEV_OPEN, &wdd->status)) | |
267 | return -EBUSY; | |
268 | ||
269 | /* | |
270 | * If the /dev/watchdog device is open, we don't want the module | |
271 | * to be unloaded. | |
272 | */ | |
273 | if (!try_module_get(wdd->ops->owner)) | |
274 | goto out; | |
275 | ||
234445b4 | 276 | err = watchdog_start(wdd); |
43316044 WVS |
277 | if (err < 0) |
278 | goto out_mod; | |
279 | ||
280 | /* dev/watchdog is a virtual (and thus non-seekable) filesystem */ | |
281 | return nonseekable_open(inode, file); | |
282 | ||
283 | out_mod: | |
284 | module_put(wdd->ops->owner); | |
285 | out: | |
286 | clear_bit(WDOG_DEV_OPEN, &wdd->status); | |
287 | return err; | |
288 | } | |
289 | ||
290 | /* | |
291 | * watchdog_release: release the /dev/watchdog device. | |
292 | * @inode: inode of device | |
293 | * @file: file handle to device | |
294 | * | |
017cf080 | 295 | * This is the code for when /dev/watchdog gets closed. We will only |
7e192b9c WVS |
296 | * stop the watchdog when we have received the magic char (and nowayout |
297 | * was not set), else the watchdog will keep running. | |
43316044 WVS |
298 | */ |
299 | ||
300 | static int watchdog_release(struct inode *inode, struct file *file) | |
301 | { | |
017cf080 WVS |
302 | int err = -EBUSY; |
303 | ||
304 | /* | |
305 | * We only stop the watchdog if we received the magic character | |
7e192b9c WVS |
306 | * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then |
307 | * watchdog_stop will fail. | |
017cf080 WVS |
308 | */ |
309 | if (test_and_clear_bit(WDOG_ALLOW_RELEASE, &wdd->status) || | |
310 | !(wdd->info->options & WDIOF_MAGICCLOSE)) | |
311 | err = watchdog_stop(wdd); | |
43316044 | 312 | |
017cf080 | 313 | /* If the watchdog was not stopped, send a keepalive ping */ |
234445b4 | 314 | if (err < 0) { |
43316044 WVS |
315 | pr_crit("%s: watchdog did not stop!\n", wdd->info->identity); |
316 | watchdog_ping(wdd); | |
317 | } | |
318 | ||
319 | /* Allow the owner module to be unloaded again */ | |
320 | module_put(wdd->ops->owner); | |
321 | ||
322 | /* make sure that /dev/watchdog can be re-opened */ | |
323 | clear_bit(WDOG_DEV_OPEN, &wdd->status); | |
324 | ||
325 | return 0; | |
326 | } | |
327 | ||
328 | static const struct file_operations watchdog_fops = { | |
329 | .owner = THIS_MODULE, | |
330 | .write = watchdog_write, | |
2fa03560 | 331 | .unlocked_ioctl = watchdog_ioctl, |
43316044 WVS |
332 | .open = watchdog_open, |
333 | .release = watchdog_release, | |
334 | }; | |
335 | ||
336 | static struct miscdevice watchdog_miscdev = { | |
337 | .minor = WATCHDOG_MINOR, | |
338 | .name = "watchdog", | |
339 | .fops = &watchdog_fops, | |
340 | }; | |
341 | ||
342 | /* | |
343 | * watchdog_dev_register: | |
344 | * @watchdog: watchdog device | |
345 | * | |
346 | * Register a watchdog device as /dev/watchdog. /dev/watchdog | |
347 | * is actually a miscdevice and thus we set it up like that. | |
348 | */ | |
349 | ||
350 | int watchdog_dev_register(struct watchdog_device *watchdog) | |
351 | { | |
352 | int err; | |
353 | ||
354 | /* Only one device can register for /dev/watchdog */ | |
355 | if (test_and_set_bit(0, &watchdog_dev_busy)) { | |
27c766aa | 356 | pr_err("only one watchdog can use /dev/watchdog\n"); |
43316044 WVS |
357 | return -EBUSY; |
358 | } | |
359 | ||
360 | wdd = watchdog; | |
361 | ||
362 | err = misc_register(&watchdog_miscdev); | |
363 | if (err != 0) { | |
27c766aa JP |
364 | pr_err("%s: cannot register miscdev on minor=%d (err=%d)\n", |
365 | watchdog->info->identity, WATCHDOG_MINOR, err); | |
43316044 WVS |
366 | goto out; |
367 | } | |
368 | ||
369 | return 0; | |
370 | ||
371 | out: | |
372 | wdd = NULL; | |
373 | clear_bit(0, &watchdog_dev_busy); | |
374 | return err; | |
375 | } | |
376 | ||
377 | /* | |
378 | * watchdog_dev_unregister: | |
379 | * @watchdog: watchdog device | |
380 | * | |
381 | * Deregister the /dev/watchdog device. | |
382 | */ | |
383 | ||
384 | int watchdog_dev_unregister(struct watchdog_device *watchdog) | |
385 | { | |
386 | /* Check that a watchdog device was registered in the past */ | |
387 | if (!test_bit(0, &watchdog_dev_busy) || !wdd) | |
388 | return -ENODEV; | |
389 | ||
390 | /* We can only unregister the watchdog device that was registered */ | |
391 | if (watchdog != wdd) { | |
27c766aa JP |
392 | pr_err("%s: watchdog was not registered as /dev/watchdog\n", |
393 | watchdog->info->identity); | |
43316044 WVS |
394 | return -ENODEV; |
395 | } | |
396 | ||
397 | misc_deregister(&watchdog_miscdev); | |
398 | wdd = NULL; | |
399 | clear_bit(0, &watchdog_dev_busy); | |
400 | return 0; | |
401 | } |