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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"); |