aboutsummaryrefslogtreecommitdiff
path: root/drivers/watchdog/watchdog_core.c
blob: 3796434991faa83466c85c8779a072db1278ef33 (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
/*
 *	watchdog_core.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.
 *
 *	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 EXPORT_SYMBOL/module stuff/... */
#include <linux/types.h>	/* For standard types */
#include <linux/errno.h>	/* For the -ENODEV/... values */
#include <linux/kernel.h>	/* For printk/panic/... */
#include <linux/watchdog.h>	/* For watchdog specific items */
#include <linux/init.h>		/* For __init/__exit/... */
#include <linux/idr.h>		/* For ida_* macros */
#include <linux/err.h>		/* For IS_ERR macros */

#include "watchdog_core.h"	/* For watchdog_dev_register/... */

static DEFINE_IDA(watchdog_ida);
static struct class *watchdog_class;

/**
 * watchdog_register_device() - register a watchdog device
 * @wdd: watchdog device
 *
 * Register a watchdog device with the kernel so that the
 * watchdog timer can be accessed from userspace.
 *
 * A zero is returned on success and a negative errno code for
 * failure.
 */
int watchdog_register_device(struct watchdog_device *wdd)
{
	int ret, id, devno;

	if (wdd == NULL || wdd->info == NULL || wdd->ops == NULL)
		return -EINVAL;

	/* Mandatory operations need to be supported */
	if (wdd->ops->start == NULL || wdd->ops->stop == NULL)
		return -EINVAL;

	/*
	 * Check that we have valid min and max timeout values, if
	 * not reset them both to 0 (=not used or unknown)
	 */
	if (wdd->min_timeout > wdd->max_timeout) {
		pr_info("Invalid min and max timeout values, resetting to 0!\n");
		wdd->min_timeout = 0;
		wdd->max_timeout = 0;
	}

	/*
	 * Note: now that all watchdog_device data has been verified, we
	 * will not check this anymore in other functions. If data gets
	 * corrupted in a later stage then we expect a kernel panic!
	 */

	mutex_init(&wdd->lock);
	id = ida_simple_get(&watchdog_ida, 0, MAX_DOGS, GFP_KERNEL);
	if (id < 0)
		return id;
	wdd->id = id;

	ret = watchdog_dev_register(wdd);
	if (ret) {
		ida_simple_remove(&watchdog_ida, id);
		if (!(id == 0 && ret == -EBUSY))
			return ret;

		/* Retry in case a legacy watchdog module exists */
		id = ida_simple_get(&watchdog_ida, 1, MAX_DOGS, GFP_KERNEL);
		if (id < 0)
			return id;
		wdd->id = id;

		ret = watchdog_dev_register(wdd);
		if (ret) {
			ida_simple_remove(&watchdog_ida, id);
			return ret;
		}
	}

	devno = wdd->cdev.dev;
	wdd->dev = device_create(watchdog_class, wdd->parent, devno,
					NULL, "watchdog%d", wdd->id);
	if (IS_ERR(wdd->dev)) {
		watchdog_dev_unregister(wdd);
		ida_simple_remove(&watchdog_ida, id);
		ret = PTR_ERR(wdd->dev);
		return ret;
	}

	return 0;
}
EXPORT_SYMBOL_GPL(watchdog_register_device);

/**
 * watchdog_unregister_device() - unregister a watchdog device
 * @wdd: watchdog device to unregister
 *
 * Unregister a watchdog device that was previously successfully
 * registered with watchdog_register_device().
 */
void watchdog_unregister_device(struct watchdog_device *wdd)
{
	int ret;
	int devno;

	if (wdd == NULL)
		return;

	devno = wdd->cdev.dev;
	ret = watchdog_dev_unregister(wdd);
	if (ret)
		pr_err("error unregistering /dev/watchdog (err=%d)\n", ret);
	device_destroy(watchdog_class, devno);
	ida_simple_remove(&watchdog_ida, wdd->id);
	wdd->dev = NULL;
}
EXPORT_SYMBOL_GPL(watchdog_unregister_device);

static int __init watchdog_init(void)
{
	int err;

	watchdog_class = class_create(THIS_MODULE, "watchdog");
	if (IS_ERR(watchdog_class)) {
		pr_err("couldn't create class\n");
		return PTR_ERR(watchdog_class);
	}

	err = watchdog_dev_init();
	if (err < 0) {
		class_destroy(watchdog_class);
		return err;
	}

	return 0;
}

static void __exit watchdog_exit(void)
{
	watchdog_dev_exit();
	class_destroy(watchdog_class);
	ida_destroy(&watchdog_ida);
}

subsys_initcall(watchdog_init);
module_exit(watchdog_exit);

MODULE_AUTHOR("Alan Cox <alan@lxorguk.ukuu.org.uk>");
MODULE_AUTHOR("Wim Van Sebroeck <wim@iguana.be>");
MODULE_DESCRIPTION("WatchDog Timer Driver Core");
MODULE_LICENSE("GPL");