summaryrefslogtreecommitdiffstats
path: root/drivers/watchdog/watchdog_dev.c
blob: 56a649e66eb2461e70a2e073fe85284bf46933aa (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
/*
 *	watchdog_dev.c
 *
 *	(c) Copyright 2008-2011 Alan Cox <alan@lxorguk.ukuu.org.uk>,
 *						All Rights Reserved.
 *
 *	(c) Copyright 2008-2011 Wim Van Sebroeck <wim@iguana.be>.
 *
 *
 *	This source code is part of the generic code that can be used
 *	by all the watchdog timer drivers.
 *
 *	This part of the generic code takes care of the following
 *	misc device: /dev/watchdog.
 *
 *	Based on source code of the following authors:
 *	  Matt Domsch <Matt_Domsch@dell.com>,
 *	  Rob Radez <rob@osinvestor.com>,
 *	  Rusty Lynch <rusty@linux.co.intel.com>
 *	  Satyam Sharma <satyam@infradead.org>
 *	  Randy Dunlap <randy.dunlap@oracle.com>
 *
 *	This program is free software; you can redistribute it and/or
 *	modify it under the terms of the GNU General Public License
 *	as published by the Free Software Foundation; either version
 *	2 of the License, or (at your option) any later version.
 *
 *	Neither Alan Cox, CymruNet Ltd., Wim Van Sebroeck nor Iguana vzw.
 *	admit liability nor provide warranty for any of this software.
 *	This material is provided "AS-IS" and at no charge.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>	/* For module stuff/... */
#include <linux/types.h>	/* For standard types (like size_t) */
#include <linux/errno.h>	/* For the -ENODEV/... values */
#include <linux/kernel.h>	/* For printk/panic/... */
#include <linux/fs.h>		/* For file operations */
#include <linux/watchdog.h>	/* For watchdog specific items */
#include <linux/miscdevice.h>	/* For handling misc devices */
#include <linux/init.h>		/* For __init/__exit/... */
#include <linux/uaccess.h>	/* For copy_to_user/put_user/... */

#include "watchdog_core.h"

/* the dev_t structure to store the dynamically allocated watchdog devices */
static dev_t watchdog_devt;
/* the watchdog device behind /dev/watchdog */
static struct watchdog_device *old_wdd;

/*
 *	watchdog_ping: ping the watchdog.
 *	@wdd: the watchdog device to ping
 *
 *	If the watchdog has no own ping operation then it needs to be
 *	restarted via the start operation. This wrapper function does
 *	exactly that.
 *	We only ping when the watchdog device is running.
 */

static int watchdog_ping(struct watchdog_device *wdd)
{
	int err = 0;

	mutex_lock(&wdd->lock);

	if (test_bit(WDOG_UNREGISTERED, &wdd->status)) {
		err = -ENODEV;
		goto out_ping;
	}

	if (!watchdog_active(wdd))
		goto out_ping;

	if (wdd->ops->ping)
		err = wdd->ops->ping(wdd);	/* ping the watchdog */
	else
		err = wdd->ops->start(wdd);	/* restart watchdog */

out_ping:
	mutex_unlock(&wdd->lock);
	return err;
}

/*
 *	watchdog_start: wrapper to start the watchdog.
 *	@wdd: the watchdog device to start
 *
 *	Start the watchdog if it is not active and mark it active.
 *	This function returns zero on success or a negative errno code for
 *	failure.
 */

static int watchdog_start(struct watchdog_device *wdd)
{
	int err = 0;

	mutex_lock(&wdd->lock);

	if (test_bit(WDOG_UNREGISTERED, &wdd->status)) {
		err = -ENODEV;
		goto out_start;
	}

	if (watchdog_active(wdd))
		goto out_start;

	err = wdd->ops->start(wdd);
	if (err == 0)
		set_bit(WDOG_ACTIVE, &wdd->status);

out_start:
	mutex_unlock(&wdd->lock);
	return err;
}

/*
 *	watchdog_stop: wrapper to stop the watchdog.
 *	@wdd: the watchdog device to stop
 *
 *	Stop the watchdog if it is still active and unmark it active.
 *	This function returns zero on success or a negative errno code for
 *	failure.
 *	If the 'nowayout' feature was set, the watchdog cannot be stopped.
 */

static int watchdog_stop(struct watchdog_device *wdd)
{
	int err = 0;

	mutex_lock(&wdd->lock);

	if (test_bit(WDOG_UNREGISTERED, &wdd->status)) {
		err = -ENODEV;
		goto out_stop;
	}

	if (!watchdog_active(wdd))
		goto out_stop;

	if (test_bit(WDOG_NO_WAY_OUT, &wdd->status)) {
		dev_info(wdd->dev, "nowayout prevents watchdog being stopped!\n");
		err = -EBUSY;
		goto out_stop;
	}

	err = wdd->ops->stop(wdd);
	if (err == 0)
		clear_bit(WDOG_ACTIVE, &wdd->status);

out_stop:
	mutex_unlock(&wdd->lock);
	return err;
}

/*
 *	watchdog_get_status: wrapper to get the watchdog status
 *	@wdd: the watchdog device to get the status from
 *	@status: the status of the watchdog device
 *
 *	Get the watchdog's status flags.
 */

static int watchdog_get_status(struct watchdog_device *wdd,
							unsigned int *status)
{
	int err = 0;

	*status = 0;
	if (!wdd->ops->status)
		return -EOPNOTSUPP;

	mutex_lock(&wdd->lock);

	if (test_bit(WDOG_UNREGISTERED, &wdd->status)) {
		err = -ENODEV;
		goto out_status;
	}

	*status = wdd->ops->status(wdd);

out_status:
	mutex_unlock(&wdd->lock);
	return err;
}

/*
 *	watchdog_set_timeout: set the watchdog timer timeout
 *	@wdd: the watchdog device to set the timeout for
 *	@timeout: timeout to set in seconds
 */

static int watchdog_set_timeout(struct watchdog_device *wdd,
							unsigned int timeout)
{
	int err;

	if (!wdd->ops->set_timeout || !(wdd->info->options & WDIOF_SETTIMEOUT))
		return -EOPNOTSUPP;

	if (watchdog_timeout_invalid(wdd, timeout))
		return -EINVAL;

	mutex_lock(&wdd->lock);

	if (test_bit(WDOG_UNREGISTERED, &wdd->status)) {
		err = -ENODEV;
		goto out_timeout;
	}

	err = wdd->ops->set_timeout(wdd, timeout);

out_timeout:
	mutex_unlock(&wdd->lock);
	return err;
}

/*
 *	watchdog_get_timeleft: wrapper to get the time left before a reboot
 *	@wdd: the watchdog device to get the remaining time from
 *	@timeleft: the time that's left
 *
 *	Get the time before a watchdog will reboot (if not pinged).
 */

static int watchdog_get_timeleft(struct watchdog_device *wdd,
							unsigned int *timeleft)
{
	int err = 0;

	*timeleft = 0;
	if (!wdd->ops->get_timeleft)
		return -EOPNOTSUPP;

	mutex_lock(&wdd->lock);

	if (test_bit(WDOG_UNREGISTERED, &wdd->status)) {
		err = -ENODEV;
		goto out_timeleft;
	}

	*timeleft = wdd->ops->get_timeleft(wdd);

out_timeleft:
	mutex_unlock(&wdd->lock);
	return err;
}

/*
 *	watchdog_ioctl_op: call the watchdog drivers ioctl op if defined
 *	@wdd: the watchdog device to do the ioctl on
 *	@cmd: watchdog command
 *	@arg: argument pointer
 */

static int watchdog_ioctl_op(struct watchdog_device *wdd, unsigned int cmd,
							unsigned long arg)
{
	int err;

	if (!wdd->ops->ioctl)
		return -ENOIOCTLCMD;

	mutex_lock(&wdd->lock);

	if (test_bit(WDOG_UNREGISTERED, &wdd->status)) {
		err = -ENODEV;
		goto out_ioctl;
	}

	err = wdd->ops->ioctl(wdd, cmd, arg);

out_ioctl:
	mutex_unlock(&wdd->lock);
	return err;
}

/*
 *	watchdog_write: writes to the watchdog.
 *	@file: file from VFS
 *	@data: user address of data
 *	@len: length of data
 *	@ppos: pointer to the file offset
 *
 *	A write to a watchdog device is defined as a keepalive ping.
 *	Writing the magic 'V' sequence allows the next close to turn
 *	off the watchdog (if 'nowayout' is not set).
 */

static ssize_t watchdog_write(struct file *file, const char __user *data,
						size_t len, loff_t *ppos)
{
	struct watchdog_device *wdd = file->private_data;
	size_t i;
	char c;
	int err;

	if (len == 0)
		return 0;

	/*
	 * Note: just in case someone wrote the magic character
	 * five months ago...
	 */
	clear_bit(WDOG_ALLOW_RELEASE, &wdd->status);

	/* scan to see whether or not we got the magic character */
	for (i = 0; i != len; i++) {
		if (get_user(c, data + i))
			return -EFAULT;
		if (c == 'V')
			set_bit(WDOG_ALLOW_RELEASE, &wdd->status);
	}

	/* someone wrote to us, so we send the watchdog a keepalive ping */
	err = watchdog_ping(wdd);
	if (err < 0)
		return err;

	return len;
}

/*
 *	watchdog_ioctl: handle the different ioctl's for the watchdog device.
 *	@file: file handle to the device
 *	@cmd: watchdog command
 *	@arg: argument pointer
 *
 *	The watchdog API defines a common set of functions for all watchdogs
 *	according to their available features.
 */

static long watchdog_ioctl(struct file *file, unsigned int cmd,
							unsigned long arg)
{
	struct watchdog_device *wdd = file->private_data;
	void __user *argp = (void __user *)arg;
	int __user *p = argp;
	unsigned int val;
	int err;

	err = watchdog_ioctl_op(wdd, cmd, arg);
	if (err != -ENOIOCTLCMD)
		return err;

	switch (cmd) {
	case WDIOC_GETSUPPORT:
		return copy_to_user(argp, wdd->info,
			sizeof(struct watchdog_info)) ? -EFAULT : 0;
	case WDIOC_GETSTATUS:
		err = watchdog_get_status(wdd, &val);
		if (err == -ENODEV)
			return err;
		return put_user(val, p);
	case WDIOC_GETBOOTSTATUS:
		return put_user(wdd->bootstatus, p);
	case WDIOC_SETOPTIONS:
		if (get_user(val, p))
			return -EFAULT;
		if (val & WDIOS_DISABLECARD) {
			err = watchdog_stop(wdd);
			if (err < 0)
				return err;
		}
		if (val & WDIOS_ENABLECARD) {
			err = watchdog_start(wdd);
			if (err < 0)
				return err;
		}
		return 0;
	case WDIOC_KEEPALIVE:
		if (!(wdd->info->options & WDIOF_KEEPALIVEPING))
			return -EOPNOTSUPP;
		return watchdog_ping(wdd);
	case WDIOC_SETTIMEOUT:
		if (get_user(val, p))
			return -EFAULT;
		err = watchdog_set_timeout(wdd, val);
		if (err < 0)
			return err;
		/* If the watchdog is active then we send a keepalive ping
		 * to make sure that the watchdog keep's running (and if
		 * possible that it takes the new timeout) */
		err = watchdog_ping(wdd);
		if (err < 0)
			return err;
		/* Fall */
	case WDIOC_GETTIMEOUT:
		/* timeout == 0 means that we don't know the timeout */
		if (wdd->timeout == 0)
			return -EOPNOTSUPP;
		return put_user(wdd->timeout, p);
	case WDIOC_GETTIMELEFT:
		err = watchdog_get_timeleft(wdd, &val);
		if (err)
			return err;
		return put_user(val, p);
	default:
		return -ENOTTY;
	}
}

/*
 *	watchdog_open: open the /dev/watchdog* devices.
 *	@inode: inode of device
 *	@file: file handle to device
 *
 *	When the /dev/watchdog* device gets opened, we start the watchdog.
 *	Watch out: the /dev/watchdog device is single open, so we make sure
 *	it can only be opened once.
 */

static int watchdog_open(struct inode *inode, struct file *file)
{
	int err = -EBUSY;
	struct watchdog_device *wdd;

	/* Get the corresponding watchdog device */
	if (imajor(inode) == MISC_MAJOR)
		wdd = old_wdd;
	else
		wdd = container_of(inode->i_cdev, struct watchdog_device, cdev);

	/* the watchdog is single open! */
	if (test_and_set_bit(WDOG_DEV_OPEN, &wdd->status))
		return -EBUSY;

	/*
	 * If the /dev/watchdog device is open, we don't want the module
	 * to be unloaded.
	 */
	if (!try_module_get(wdd->ops->owner))
		goto out;

	err = watchdog_start(wdd);
	if (err < 0)
		goto out_mod;

	file->private_data = wdd;

	if (wdd->ops->ref)
		wdd->ops->ref(wdd);

	/* dev/watchdog is a virtual (and thus non-seekable) filesystem */
	return nonseekable_open(inode, file);

out_mod:
	module_put(wdd->ops->owner);
out:
	clear_bit(WDOG_DEV_OPEN, &wdd->status);
	return err;
}

/*
 *	watchdog_release: release the watchdog device.
 *	@inode: inode of device
 *	@file: file handle to device
 *
 *	This is the code for when /dev/watchdog gets closed. We will only
 *	stop the watchdog when we have received the magic char (and nowayout
 *	was not set), else the watchdog will keep running.
 */

static int watchdog_release(struct inode *inode, struct file *file)
{
	struct watchdog_device *wdd = file->private_data;
	int err = -EBUSY;

	/*
	 * We only stop the watchdog if we received the magic character
	 * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then
	 * watchdog_stop will fail.
	 */
	if (!test_bit(WDOG_ACTIVE, &wdd->status))
		err = 0;
	else if (test_and_clear_bit(WDOG_ALLOW_RELEASE, &wdd->status) ||
		 !(wdd->info->options & WDIOF_MAGICCLOSE))
		err = watchdog_stop(wdd);

	/* If the watchdog was not stopped, send a keepalive ping */
	if (err < 0) {
		mutex_lock(&wdd->lock);
		if (!test_bit(WDOG_UNREGISTERED, &wdd->status))
			dev_crit(wdd->dev, "watchdog did not stop!\n");
		mutex_unlock(&wdd->lock);
		watchdog_ping(wdd);
	}

	/* Allow the owner module to be unloaded again */
	module_put(wdd->ops->owner);

	/* make sure that /dev/watchdog can be re-opened */
	clear_bit(WDOG_DEV_OPEN, &wdd->status);

	/* Note wdd may be gone after this, do not use after this! */
	if (wdd->ops->unref)
		wdd->ops->unref(wdd);

	return 0;
}

static const struct file_operations watchdog_fops = {
	.owner		= THIS_MODULE,
	.write		= watchdog_write,
	.unlocked_ioctl	= watchdog_ioctl,
	.open		= watchdog_open,
	.release	= watchdog_release,
};

static struct miscdevice watchdog_miscdev = {
	.minor		= WATCHDOG_MINOR,
	.name		= "watchdog",
	.fops		= &watchdog_fops,
};

/*
 *	watchdog_dev_register: register a watchdog device
 *	@wdd: watchdog device
 *
 *	Register a watchdog device including handling the legacy
 *	/dev/watchdog node. /dev/watchdog is actually a miscdevice and
 *	thus we set it up like that.
 */

int watchdog_dev_register(struct watchdog_device *wdd)
{
	int err, devno;

	if (wdd->id == 0) {
		old_wdd = wdd;
		watchdog_miscdev.parent = wdd->parent;
		err = misc_register(&watchdog_miscdev);
		if (err != 0) {
			pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n",
				wdd->info->identity, WATCHDOG_MINOR, err);
			if (err == -EBUSY)
				pr_err("%s: a legacy watchdog module is probably present.\n",
					wdd->info->identity);
			old_wdd = NULL;
			return err;
		}
	}

	/* Fill in the data structures */
	devno = MKDEV(MAJOR(watchdog_devt), wdd->id);
	cdev_init(&wdd->cdev, &watchdog_fops);
	wdd->cdev.owner = wdd->ops->owner;

	/* Add the device */
	err  = cdev_add(&wdd->cdev, devno, 1);
	if (err) {
		pr_err("watchdog%d unable to add device %d:%d\n",
			wdd->id,  MAJOR(watchdog_devt), wdd->id);
		if (wdd->id == 0) {
			misc_deregister(&watchdog_miscdev);
			old_wdd = NULL;
		}
	}
	return err;
}

/*
 *	watchdog_dev_unregister: unregister a watchdog device
 *	@watchdog: watchdog device
 *
 *	Unregister the watchdog and if needed the legacy /dev/watchdog device.
 */

int watchdog_dev_unregister(struct watchdog_device *wdd)
{
	mutex_lock(&wdd->lock);
	set_bit(WDOG_UNREGISTERED, &wdd->status);
	mutex_unlock(&wdd->lock);

	cdev_del(&wdd->cdev);
	if (wdd->id == 0) {
		misc_deregister(&watchdog_miscdev);
		old_wdd = NULL;
	}
	return 0;
}

/*
 *	watchdog_dev_init: init dev part of watchdog core
 *
 *	Allocate a range of chardev nodes to use for watchdog devices
 */

int __init watchdog_dev_init(void)
{
	int err = alloc_chrdev_region(&watchdog_devt, 0, MAX_DOGS, "watchdog");
	if (err < 0)
		pr_err("watchdog: unable to allocate char dev region\n");
	return err;
}

/*
 *	watchdog_dev_exit: exit dev part of watchdog core
 *
 *	Release the range of chardev nodes used for watchdog devices
 */

void __exit watchdog_dev_exit(void)
{
	unregister_chrdev_region(watchdog_devt, MAX_DOGS);
}