File: /usr/src/linux/Documentation/DocBook/procfs_example.c
1 /*
2 * procfs_example.c: an example proc interface
3 *
4 * Copyright (C) 2001, Erik Mouw (J.A.K.Mouw@its.tudelft.nl)
5 *
6 * This file accompanies the procfs-guide in the Linux kernel
7 * source. Its main use is to demonstrate the concepts and
8 * functions described in the guide.
9 *
10 * This software has been developed while working on the LART
11 * computing board (http://www.lart.tudelft.nl/), which is
12 * sponsored by the Mobile Multi-media Communications
13 * (http://www.mmc.tudelft.nl/) and Ubiquitous Communications
14 * (http://www.ubicom.tudelft.nl/) projects.
15 *
16 * The author can be reached at:
17 *
18 * Erik Mouw
19 * Information and Communication Theory Group
20 * Faculty of Information Technology and Systems
21 * Delft University of Technology
22 * P.O. Box 5031
23 * 2600 GA Delft
24 * The Netherlands
25 *
26 *
27 * This program is free software; you can redistribute
28 * it and/or modify it under the terms of the GNU General
29 * Public License as published by the Free Software
30 * Foundation; either version 2 of the License, or (at your
31 * option) any later version.
32 *
33 * This program is distributed in the hope that it will be
34 * useful, but WITHOUT ANY WARRANTY; without even the implied
35 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
36 * PURPOSE. See the GNU General Public License for more
37 * details.
38 *
39 * You should have received a copy of the GNU General Public
40 * License along with this program; if not, write to the
41 * Free Software Foundation, Inc., 59 Temple Place,
42 * Suite 330, Boston, MA 02111-1307 USA
43 *
44 */
45
46 #include <linux/module.h>
47 #include <linux/kernel.h>
48 #include <linux/init.h>
49 #include <linux/proc_fs.h>
50 #include <linux/sched.h>
51 #include <asm/uaccess.h>
52
53
54 #define MODULE_VERSION "1.0"
55 #define MODULE_NAME "procfs_example"
56
57 #define FOOBAR_LEN 8
58
59 struct fb_data_t {
60 char name[FOOBAR_LEN + 1];
61 char value[FOOBAR_LEN + 1];
62 };
63
64
65 static struct proc_dir_entry *example_dir, *foo_file,
66 *bar_file, *jiffies_file, *tty_device, *symlink;
67
68
69 struct fb_data_t foo_data, bar_data;
70
71
72 static int proc_read_jiffies(char *page, char **start,
73 off_t off, int count,
74 int *eof, void *data)
75 {
76 int len;
77
78 MOD_INC_USE_COUNT;
79
80 len = sprintf(page, "jiffies = %ld\n",
81 jiffies);
82
83 MOD_DEC_USE_COUNT;
84
85 return len;
86 }
87
88
89 static int proc_read_foobar(char *page, char **start,
90 off_t off, int count,
91 int *eof, void *data)
92 {
93 int len;
94 struct fb_data_t *fb_data = (struct fb_data_t *)data;
95
96 MOD_INC_USE_COUNT;
97
98 len = sprintf(page, "%s = '%s'\n",
99 fb_data->name, fb_data->value);
100
101 MOD_DEC_USE_COUNT;
102
103 return len;
104 }
105
106
107 static int proc_write_foobar(struct file *file,
108 const char *buffer,
109 unsigned long count,
110 void *data)
111 {
112 int len;
113 struct fb_data_t *fb_data = (struct fb_data_t *)data;
114
115 MOD_INC_USE_COUNT;
116
117 if(count > FOOBAR_LEN)
118 len = FOOBAR_LEN;
119 else
120 len = count;
121
122 if(copy_from_user(fb_data->value, buffer, len)) {
123 MOD_DEC_USE_COUNT;
124 return -EFAULT;
125 }
126
127 fb_data->value[len] = '\0';
128
129 MOD_DEC_USE_COUNT;
130
131 return len;
132 }
133
134
135 static int __init init_procfs_example(void)
136 {
137 int rv = 0;
138
139 /* create directory */
140 example_dir = proc_mkdir(MODULE_NAME, NULL);
141 if(example_dir == NULL) {
142 rv = -ENOMEM;
143 goto out;
144 }
145
146 example_dir->owner = THIS_MODULE;
147
148 /* create jiffies using convenience function */
149 jiffies_file = create_proc_read_entry("jiffies",
150 0444, example_dir,
151 proc_read_jiffies,
152 NULL);
153 if(jiffies_file == NULL) {
154 rv = -ENOMEM;
155 goto no_jiffies;
156 }
157
158 jiffies_file->owner = THIS_MODULE;
159
160 /* create foo and bar files using same callback
161 * functions
162 */
163 foo_file = create_proc_entry("foo", 0644, example_dir);
164 if(foo_file == NULL) {
165 rv = -ENOMEM;
166 goto no_foo;
167 }
168
169 strcpy(foo_data.name, "foo");
170 strcpy(foo_data.value, "foo");
171 foo_file->data = &foo_data;
172 foo_file->read_proc = proc_read_foobar;
173 foo_file->write_proc = proc_write_foobar;
174 foo_file->owner = THIS_MODULE;
175
176 bar_file = create_proc_entry("bar", 0644, example_dir);
177 if(bar_file == NULL) {
178 rv = -ENOMEM;
179 goto no_bar;
180 }
181
182 strcpy(bar_data.name, "bar");
183 strcpy(bar_data.value, "bar");
184 bar_file->data = &bar_data;
185 bar_file->read_proc = proc_read_foobar;
186 bar_file->write_proc = proc_write_foobar;
187 bar_file->owner = THIS_MODULE;
188
189 /* create tty device */
190 tty_device = proc_mknod("tty", S_IFCHR | 0666,
191 example_dir, MKDEV(5, 0));
192 if(tty_device == NULL) {
193 rv = -ENOMEM;
194 goto no_tty;
195 }
196
197 tty_device->owner = THIS_MODULE;
198
199 /* create symlink */
200 symlink = proc_symlink("jiffies_too", example_dir,
201 "jiffies");
202 if(symlink == NULL) {
203 rv = -ENOMEM;
204 goto no_symlink;
205 }
206
207 symlink->owner = THIS_MODULE;
208
209 /* everything OK */
210 printk(KERN_INFO "%s %s initialised\n",
211 MODULE_NAME, MODULE_VERSION);
212 return 0;
213
214 no_symlink:
215 remove_proc_entry("tty", example_dir);
216 no_tty:
217 remove_proc_entry("bar", example_dir);
218 no_bar:
219 remove_proc_entry("foo", example_dir);
220 no_foo:
221 remove_proc_entry("jiffies", example_dir);
222 no_jiffies:
223 remove_proc_entry(MODULE_NAME, NULL);
224 out:
225 return rv;
226 }
227
228
229 static void __exit cleanup_procfs_example(void)
230 {
231 remove_proc_entry("jiffies_too", example_dir);
232 remove_proc_entry("tty", example_dir);
233 remove_proc_entry("bar", example_dir);
234 remove_proc_entry("foo", example_dir);
235 remove_proc_entry("jiffies", example_dir);
236 remove_proc_entry(MODULE_NAME, NULL);
237
238 printk(KERN_INFO "%s %s removed\n",
239 MODULE_NAME, MODULE_VERSION);
240 }
241
242
243 module_init(init_procfs_example);
244 module_exit(cleanup_procfs_example);
245
246 MODULE_AUTHOR("Erik Mouw");
247 MODULE_DESCRIPTION("procfs examples");
248
249 EXPORT_NO_SYMBOLS;
250