1/* UML hardware watchdog, shamelessly stolen from:
2 *
3 *	SoftDog	0.05:	A Software Watchdog Device
4 *
5 *	(c) Copyright 1996 Alan Cox <alan@redhat.com>, All Rights Reserved.
6 *				http://www.redhat.com
7 *
8 *	This program is free software; you can redistribute it and/or
9 *	modify it under the terms of the GNU General Public License
10 *	as published by the Free Software Foundation; either version
11 *	2 of the License, or (at your option) any later version.
12 *
13 *	Neither Alan Cox nor CymruNet Ltd. admit liability nor provide
14 *	warranty for any of this software. This material is provided
15 *	"AS-IS" and at no charge.
16 *
17 *	(c) Copyright 1995    Alan Cox <alan@lxorguk.ukuu.org.uk>
18 *
19 *	Software only watchdog driver. Unlike its big brother the WDT501P
20 *	driver this won't always recover a failed machine.
21 *
22 *  03/96: Angelo Haritsis <ah@doc.ic.ac.uk> :
23 *	Modularised.
24 *	Added soft_margin; use upon insmod to change the timer delay.
25 *	NB: uses same minor as wdt (WATCHDOG_MINOR); we could use separate
26 *	    minors.
27 *
28 *  19980911 Alan Cox
29 *	Made SMP safe for 2.3.x
30 *
31 *  20011127 Joel Becker (jlbec@evilplan.org>
32 *	Added soft_noboot; Allows testing the softdog trigger without
33 *	requiring a recompile.
34 *	Added WDIOC_GETTIMEOUT and WDIOC_SETTIMOUT.
35 */
36
37#include <linux/module.h>
38#include <linux/types.h>
39#include <linux/kernel.h>
40#include <linux/fs.h>
41#include <linux/mm.h>
42#include <linux/miscdevice.h>
43#include <linux/watchdog.h>
44#include <linux/reboot.h>
45#include <linux/mutex.h>
46#include <linux/init.h>
47#include <linux/spinlock.h>
48#include <linux/uaccess.h>
49#include "mconsole.h"
50#include "harddog.h"
51
52MODULE_LICENSE("GPL");
53
54static DEFINE_MUTEX(harddog_mutex);
55static DEFINE_SPINLOCK(lock);
56static int timer_alive;
57static int harddog_in_fd = -1;
58static int harddog_out_fd = -1;
59
60/*
61 *	Allow only one person to hold it open
62 */
63
64static int harddog_open(struct inode *inode, struct file *file)
65{
66	int err = -EBUSY;
67	char *sock = NULL;
68
69	mutex_lock(&harddog_mutex);
70	spin_lock(&lock);
71	if(timer_alive)
72		goto err;
73#ifdef CONFIG_WATCHDOG_NOWAYOUT
74	__module_get(THIS_MODULE);
75#endif
76
77#ifdef CONFIG_MCONSOLE
78	sock = mconsole_notify_socket();
79#endif
80	err = start_watchdog(&harddog_in_fd, &harddog_out_fd, sock);
81	if(err)
82		goto err;
83
84	timer_alive = 1;
85	spin_unlock(&lock);
86	mutex_unlock(&harddog_mutex);
87	return stream_open(inode, file);
88err:
89	spin_unlock(&lock);
90	mutex_unlock(&harddog_mutex);
91	return err;
92}
93
94static int harddog_release(struct inode *inode, struct file *file)
95{
96	/*
97	 *	Shut off the timer.
98	 */
99
100	spin_lock(&lock);
101
102	stop_watchdog(harddog_in_fd, harddog_out_fd);
103	harddog_in_fd = -1;
104	harddog_out_fd = -1;
105
106	timer_alive=0;
107	spin_unlock(&lock);
108
109	return 0;
110}
111
112static ssize_t harddog_write(struct file *file, const char __user *data, size_t len,
113			     loff_t *ppos)
114{
115	/*
116	 *	Refresh the timer.
117	 */
118	if(len)
119		return ping_watchdog(harddog_out_fd);
120	return 0;
121}
122
123static int harddog_ioctl_unlocked(struct file *file,
124				  unsigned int cmd, unsigned long arg)
125{
126	void __user *argp= (void __user *)arg;
127	static struct watchdog_info ident = {
128		WDIOC_SETTIMEOUT,
129		0,
130		"UML Hardware Watchdog"
131	};
132	switch (cmd) {
133		default:
134			return -ENOTTY;
135		case WDIOC_GETSUPPORT:
136			if(copy_to_user(argp, &ident, sizeof(ident)))
137				return -EFAULT;
138			return 0;
139		case WDIOC_GETSTATUS:
140		case WDIOC_GETBOOTSTATUS:
141			return put_user(0,(int __user *)argp);
142		case WDIOC_KEEPALIVE:
143			return ping_watchdog(harddog_out_fd);
144	}
145}
146
147static long harddog_ioctl(struct file *file,
148			  unsigned int cmd, unsigned long arg)
149{
150	long ret;
151
152	mutex_lock(&harddog_mutex);
153	ret = harddog_ioctl_unlocked(file, cmd, arg);
154	mutex_unlock(&harddog_mutex);
155
156	return ret;
157}
158
159static const struct file_operations harddog_fops = {
160	.owner		= THIS_MODULE,
161	.write		= harddog_write,
162	.unlocked_ioctl	= harddog_ioctl,
163	.compat_ioctl	= compat_ptr_ioctl,
164	.open		= harddog_open,
165	.release	= harddog_release,
166	.llseek		= no_llseek,
167};
168
169static struct miscdevice harddog_miscdev = {
170	.minor		= WATCHDOG_MINOR,
171	.name		= "watchdog",
172	.fops		= &harddog_fops,
173};
174module_misc_device(harddog_miscdev);
175