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/jiffies.h>
51 #include <asm/uaccess.h>
52
53
54 #define MODULE_VERS "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, *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 len = sprintf(page, "jiffies = %ld\n",
79 jiffies);
80
81 return len;
82 }
83
84
85 static int proc_read_foobar(char *page, char **start,
86 off_t off, int count,
87 int *eof, void *data)
88 {
89 int len;
90 struct fb_data_t *fb_data = (struct fb_data_t *)data;
91
92 /* DON'T DO THAT - buffer overruns are bad */
93 len = sprintf(page, "%s = '%s'\n",
94 fb_data->name, fb_data->value);
95
96 return len;
97 }
98
99
100 static int proc_write_foobar(struct file *file,
101 const char *buffer,
102 unsigned long count,
103 void *data)
104 {
105 int len;
106 struct fb_data_t *fb_data = (struct fb_data_t *)data;
107
108 if(count > FOOBAR_LEN)
109 len = FOOBAR_LEN;
110 else
111 len = count;
112
113 if(copy_from_user(fb_data->value, buffer, len))
114 return -EFAULT;
115
116 fb_data->value[len] = '\0';
117
118 return len;
119 }
120
121
122 static int __init init_procfs_example(void)
123 {
124 int rv = 0;
125
126 /* create directory */
127 example_dir = proc_mkdir(MODULE_NAME, NULL);
128 if(example_dir == NULL) {
129 rv = -ENOMEM;
130 goto out;
131 }
132
133 example_dir->owner = THIS_MODULE;
134
135 /* create jiffies using convenience function */
136 jiffies_file = create_proc_read_entry("jiffies",
137 0444, example_dir,
138 proc_read_jiffies,
139 NULL);
140 if(jiffies_file == NULL) {
141 rv = -ENOMEM;
142 goto no_jiffies;
143 }
144
145 jiffies_file->owner = THIS_MODULE;
146
147 /* create foo and bar files using same callback
148 * functions
149 */
150 foo_file = create_proc_entry("foo", 0644, example_dir);
151 if(foo_file == NULL) {
152 rv = -ENOMEM;
153 goto no_foo;
154 }
155
156 strcpy(foo_data.name, "foo");
157 strcpy(foo_data.value, "foo");
158 foo_file->data = &foo_data;
159 foo_file->read_proc = proc_read_foobar;
160 foo_file->write_proc = proc_write_foobar;
161 foo_file->owner = THIS_MODULE;
162
163 bar_file = create_proc_entry("bar", 0644, example_dir);
164 if(bar_file == NULL) {
165 rv = -ENOMEM;
166 goto no_bar;
167 }
168
169 strcpy(bar_data.name, "bar");
170 strcpy(bar_data.value, "bar");
171 bar_file->data = &bar_data;
172 bar_file->read_proc = proc_read_foobar;
173 bar_file->write_proc = proc_write_foobar;
174 bar_file->owner = THIS_MODULE;
175
176 /* create symlink */
177 symlink = proc_symlink("jiffies_too", example_dir,
178 "jiffies");
179 if(symlink == NULL) {
180 rv = -ENOMEM;
181 goto no_symlink;
182 }
183
184 symlink->owner = THIS_MODULE;
185
186 /* everything OK */
187 printk(KERN_INFO "%s %s initialised\n",
188 MODULE_NAME, MODULE_VERS);
189 return 0;
190
191 no_symlink:
192 remove_proc_entry("tty", example_dir);
193 no_tty:
194 remove_proc_entry("bar", example_dir);
195 no_bar:
196 remove_proc_entry("foo", example_dir);
197 no_foo:
198 remove_proc_entry("jiffies", example_dir);
199 no_jiffies:
200 remove_proc_entry(MODULE_NAME, NULL);
201 out:
202 return rv;
203 }
204
205
206 static void __exit cleanup_procfs_example(void)
207 {
208 remove_proc_entry("jiffies_too", example_dir);
209 remove_proc_entry("tty", example_dir);
210 remove_proc_entry("bar", example_dir);
211 remove_proc_entry("foo", example_dir);
212 remove_proc_entry("jiffies", example_dir);
213 remove_proc_entry(MODULE_NAME, NULL);
214
215 printk(KERN_INFO "%s %s removed\n",
216 MODULE_NAME, MODULE_VERS);
217 }
218
219
220 module_init(init_procfs_example);
221 module_exit(cleanup_procfs_example);
222
223 MODULE_AUTHOR("Erik Mouw");
224 MODULE_DESCRIPTION("procfs examples");
225
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