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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 | ||
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; | |
49 | ||
50 | /* | |
51 | * watchdog_ping: ping the watchdog. | |
52 | * @wddev: the watchdog device to ping | |
53 | * | |
54 | * If the watchdog has no own ping operation then it needs to be | |
55 | * restarted via the start operation. This wrapper function does | |
56 | * exactly that. | |
57 | */ | |
58 | ||
59 | static int watchdog_ping(struct watchdog_device *wddev) | |
60 | { | |
61 | if (wddev->ops->ping) | |
62 | return wddev->ops->ping(wddev); /* ping the watchdog */ | |
63 | else | |
64 | return wddev->ops->start(wddev); /* restart the watchdog */ | |
65 | } | |
66 | ||
67 | /* | |
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 | |
73 | * | |
74 | * A write to a watchdog device is defined as a keepalive ping. | |
75 | */ | |
76 | ||
77 | static ssize_t watchdog_write(struct file *file, const char __user *data, | |
78 | size_t len, loff_t *ppos) | |
79 | { | |
80 | size_t i; | |
81 | char c; | |
82 | ||
83 | if (len == 0) | |
84 | return 0; | |
85 | ||
86 | for (i = 0; i != len; i++) { | |
87 | if (get_user(c, data + i)) | |
88 | return -EFAULT; | |
89 | } | |
90 | ||
91 | /* someone wrote to us, so we send the watchdog a keepalive ping */ | |
92 | watchdog_ping(wdd); | |
93 | ||
94 | return len; | |
95 | } | |
96 | ||
2fa03560 WVS |
97 | /* |
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 | |
102 | * | |
103 | * The watchdog API defines a common set of functions for all watchdogs | |
104 | * according to their available features. | |
105 | */ | |
106 | ||
107 | static long watchdog_ioctl(struct file *file, unsigned int cmd, | |
108 | unsigned long arg) | |
109 | { | |
110 | void __user *argp = (void __user *)arg; | |
111 | int __user *p = argp; | |
112 | unsigned int val; | |
113 | ||
114 | switch (cmd) { | |
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); | |
c2dc00e4 WVS |
123 | case WDIOC_KEEPALIVE: |
124 | if (!(wdd->info->options & WDIOF_KEEPALIVEPING)) | |
125 | return -EOPNOTSUPP; | |
126 | watchdog_ping(wdd); | |
127 | return 0; | |
2fa03560 WVS |
128 | default: |
129 | return -ENOTTY; | |
130 | } | |
131 | } | |
132 | ||
43316044 WVS |
133 | /* |
134 | * watchdog_open: open the /dev/watchdog device. | |
135 | * @inode: inode of device | |
136 | * @file: file handle to device | |
137 | * | |
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. | |
141 | */ | |
142 | ||
143 | static int watchdog_open(struct inode *inode, struct file *file) | |
144 | { | |
145 | int err = -EBUSY; | |
146 | ||
147 | /* the watchdog is single open! */ | |
148 | if (test_and_set_bit(WDOG_DEV_OPEN, &wdd->status)) | |
149 | return -EBUSY; | |
150 | ||
151 | /* | |
152 | * If the /dev/watchdog device is open, we don't want the module | |
153 | * to be unloaded. | |
154 | */ | |
155 | if (!try_module_get(wdd->ops->owner)) | |
156 | goto out; | |
157 | ||
158 | err = wdd->ops->start(wdd); | |
159 | if (err < 0) | |
160 | goto out_mod; | |
161 | ||
162 | /* dev/watchdog is a virtual (and thus non-seekable) filesystem */ | |
163 | return nonseekable_open(inode, file); | |
164 | ||
165 | out_mod: | |
166 | module_put(wdd->ops->owner); | |
167 | out: | |
168 | clear_bit(WDOG_DEV_OPEN, &wdd->status); | |
169 | return err; | |
170 | } | |
171 | ||
172 | /* | |
173 | * watchdog_release: release the /dev/watchdog device. | |
174 | * @inode: inode of device | |
175 | * @file: file handle to device | |
176 | * | |
177 | * This is the code for when /dev/watchdog gets closed. | |
178 | */ | |
179 | ||
180 | static int watchdog_release(struct inode *inode, struct file *file) | |
181 | { | |
182 | int err; | |
183 | ||
184 | err = wdd->ops->stop(wdd); | |
185 | if (err != 0) { | |
186 | pr_crit("%s: watchdog did not stop!\n", wdd->info->identity); | |
187 | watchdog_ping(wdd); | |
188 | } | |
189 | ||
190 | /* Allow the owner module to be unloaded again */ | |
191 | module_put(wdd->ops->owner); | |
192 | ||
193 | /* make sure that /dev/watchdog can be re-opened */ | |
194 | clear_bit(WDOG_DEV_OPEN, &wdd->status); | |
195 | ||
196 | return 0; | |
197 | } | |
198 | ||
199 | static const struct file_operations watchdog_fops = { | |
200 | .owner = THIS_MODULE, | |
201 | .write = watchdog_write, | |
2fa03560 | 202 | .unlocked_ioctl = watchdog_ioctl, |
43316044 WVS |
203 | .open = watchdog_open, |
204 | .release = watchdog_release, | |
205 | }; | |
206 | ||
207 | static struct miscdevice watchdog_miscdev = { | |
208 | .minor = WATCHDOG_MINOR, | |
209 | .name = "watchdog", | |
210 | .fops = &watchdog_fops, | |
211 | }; | |
212 | ||
213 | /* | |
214 | * watchdog_dev_register: | |
215 | * @watchdog: watchdog device | |
216 | * | |
217 | * Register a watchdog device as /dev/watchdog. /dev/watchdog | |
218 | * is actually a miscdevice and thus we set it up like that. | |
219 | */ | |
220 | ||
221 | int watchdog_dev_register(struct watchdog_device *watchdog) | |
222 | { | |
223 | int err; | |
224 | ||
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"); | |
228 | return -EBUSY; | |
229 | } | |
230 | ||
231 | wdd = watchdog; | |
232 | ||
233 | err = misc_register(&watchdog_miscdev); | |
234 | if (err != 0) { | |
235 | pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n", | |
236 | watchdog->info->identity, WATCHDOG_MINOR, err); | |
237 | goto out; | |
238 | } | |
239 | ||
240 | return 0; | |
241 | ||
242 | out: | |
243 | wdd = NULL; | |
244 | clear_bit(0, &watchdog_dev_busy); | |
245 | return err; | |
246 | } | |
247 | ||
248 | /* | |
249 | * watchdog_dev_unregister: | |
250 | * @watchdog: watchdog device | |
251 | * | |
252 | * Deregister the /dev/watchdog device. | |
253 | */ | |
254 | ||
255 | int watchdog_dev_unregister(struct watchdog_device *watchdog) | |
256 | { | |
257 | /* Check that a watchdog device was registered in the past */ | |
258 | if (!test_bit(0, &watchdog_dev_busy) || !wdd) | |
259 | return -ENODEV; | |
260 | ||
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); | |
265 | return -ENODEV; | |
266 | } | |
267 | ||
268 | misc_deregister(&watchdog_miscdev); | |
269 | wdd = NULL; | |
270 | clear_bit(0, &watchdog_dev_busy); | |
271 | return 0; | |
272 | } |