4 * (c) Copyright 2008-2011 Alan Cox <alan@lxorguk.ukuu.org.uk>,
7 * (c) Copyright 2008-2011 Wim Van Sebroeck <wim@iguana.be>.
10 * This source code is part of the generic code that can be used
11 * by all the watchdog timer drivers.
13 * This part of the generic code takes care of the following
14 * misc device: /dev/watchdog.
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>
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.
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.
33 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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/... */
45 /* make sure we only register one /dev/watchdog device */
46 static unsigned long watchdog_dev_busy
;
47 /* the watchdog device behind /dev/watchdog */
48 static struct watchdog_device
*wdd
;
51 * watchdog_ping: ping the watchdog.
52 * @wddev: the watchdog device to ping
54 * If the watchdog has no own ping operation then it needs to be
55 * restarted via the start operation. This wrapper function does
59 static int watchdog_ping(struct watchdog_device
*wddev
)
62 return wddev
->ops
->ping(wddev
); /* ping the watchdog */
64 return wddev
->ops
->start(wddev
); /* restart the watchdog */
68 * watchdog_write: writes to the watchdog.
69 * @file: file from VFS
70 * @data: user address of data
71 * @len: length of data
72 * @ppos: pointer to the file offset
74 * A write to a watchdog device is defined as a keepalive ping.
77 static ssize_t
watchdog_write(struct file
*file
, const char __user
*data
,
78 size_t len
, loff_t
*ppos
)
86 for (i
= 0; i
!= len
; i
++) {
87 if (get_user(c
, data
+ i
))
91 /* someone wrote to us, so we send the watchdog a keepalive ping */
98 * watchdog_ioctl: handle the different ioctl's for the watchdog device.
99 * @file: file handle to the device
100 * @cmd: watchdog command
101 * @arg: argument pointer
103 * The watchdog API defines a common set of functions for all watchdogs
104 * according to their available features.
107 static long watchdog_ioctl(struct file
*file
, unsigned int cmd
,
110 void __user
*argp
= (void __user
*)arg
;
111 int __user
*p
= argp
;
115 case WDIOC_GETSUPPORT
:
116 return copy_to_user(argp
, wdd
->info
,
117 sizeof(struct watchdog_info
)) ? -EFAULT
: 0;
118 case WDIOC_GETSTATUS
:
119 val
= wdd
->ops
->status
? wdd
->ops
->status(wdd
) : 0;
120 return put_user(val
, p
);
121 case WDIOC_GETBOOTSTATUS
:
122 return put_user(wdd
->bootstatus
, p
);
123 case WDIOC_KEEPALIVE
:
124 if (!(wdd
->info
->options
& WDIOF_KEEPALIVEPING
))
134 * watchdog_open: open the /dev/watchdog device.
135 * @inode: inode of device
136 * @file: file handle to device
138 * When the /dev/watchdog device gets opened, we start the watchdog.
139 * Watch out: the /dev/watchdog device is single open, so we make sure
140 * it can only be opened once.
143 static int watchdog_open(struct inode
*inode
, struct file
*file
)
147 /* the watchdog is single open! */
148 if (test_and_set_bit(WDOG_DEV_OPEN
, &wdd
->status
))
152 * If the /dev/watchdog device is open, we don't want the module
155 if (!try_module_get(wdd
->ops
->owner
))
158 err
= wdd
->ops
->start(wdd
);
162 /* dev/watchdog is a virtual (and thus non-seekable) filesystem */
163 return nonseekable_open(inode
, file
);
166 module_put(wdd
->ops
->owner
);
168 clear_bit(WDOG_DEV_OPEN
, &wdd
->status
);
173 * watchdog_release: release the /dev/watchdog device.
174 * @inode: inode of device
175 * @file: file handle to device
177 * This is the code for when /dev/watchdog gets closed.
180 static int watchdog_release(struct inode
*inode
, struct file
*file
)
184 err
= wdd
->ops
->stop(wdd
);
186 pr_crit("%s: watchdog did not stop!\n", wdd
->info
->identity
);
190 /* Allow the owner module to be unloaded again */
191 module_put(wdd
->ops
->owner
);
193 /* make sure that /dev/watchdog can be re-opened */
194 clear_bit(WDOG_DEV_OPEN
, &wdd
->status
);
199 static const struct file_operations watchdog_fops
= {
200 .owner
= THIS_MODULE
,
201 .write
= watchdog_write
,
202 .unlocked_ioctl
= watchdog_ioctl
,
203 .open
= watchdog_open
,
204 .release
= watchdog_release
,
207 static struct miscdevice watchdog_miscdev
= {
208 .minor
= WATCHDOG_MINOR
,
210 .fops
= &watchdog_fops
,
214 * watchdog_dev_register:
215 * @watchdog: watchdog device
217 * Register a watchdog device as /dev/watchdog. /dev/watchdog
218 * is actually a miscdevice and thus we set it up like that.
221 int watchdog_dev_register(struct watchdog_device
*watchdog
)
225 /* Only one device can register for /dev/watchdog */
226 if (test_and_set_bit(0, &watchdog_dev_busy
)) {
227 pr_err("only one watchdog can use /dev/watchdog.\n");
233 err
= misc_register(&watchdog_miscdev
);
235 pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n",
236 watchdog
->info
->identity
, WATCHDOG_MINOR
, err
);
244 clear_bit(0, &watchdog_dev_busy
);
249 * watchdog_dev_unregister:
250 * @watchdog: watchdog device
252 * Deregister the /dev/watchdog device.
255 int watchdog_dev_unregister(struct watchdog_device
*watchdog
)
257 /* Check that a watchdog device was registered in the past */
258 if (!test_bit(0, &watchdog_dev_busy
) || !wdd
)
261 /* We can only unregister the watchdog device that was registered */
262 if (watchdog
!= wdd
) {
263 pr_err("%s: watchdog was not registered as /dev/watchdog.\n",
264 watchdog
->info
->identity
);
268 misc_deregister(&watchdog_miscdev
);
270 clear_bit(0, &watchdog_dev_busy
);