Documentation/DocBook/procfs_example.c

/*
 * procfs_example.c: an example proc interface
 *
 * Copyright (C) 2001, Erik Mouw (J.A.K.Mouw@its.tudelft.nl)
 *
 * This file accompanies the procfs-guide in the Linux kernel
 * source. Its main use is to demonstrate the concepts and
 * functions described in the guide.
 *
 * This software has been developed while working on the LART
 * computing board (http://www.lart.tudelft.nl/), which is
 * sponsored by the Mobile Multi-media Communications
 * (http://www.mmc.tudelft.nl/) and Ubiquitous Communications 
 * (http://www.ubicom.tudelft.nl/) projects.
 *
 * The author can be reached at:
 *
 *  Erik Mouw
 *  Information and Communication Theory Group
 *  Faculty of Information Technology and Systems
 *  Delft University of Technology
 *  P.O. Box 5031
 *  2600 GA Delft
 *  The Netherlands
 *
 *
 * This program is free software; you can redistribute
 * it and/or modify it under the terms of the GNU General
 * Public License as published by the Free Software
 * Foundation; either version 2 of the License, or (at your
 * option) any later version.
 *
 * This program is distributed in the hope that it will be
 * useful, but WITHOUT ANY WARRANTY; without even the implied
 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
 * PURPOSE.  See the GNU General Public License for more
 * details.
 * 
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place,
 * Suite 330, Boston, MA  02111-1307  USA
 *
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/proc_fs.h>
#include <linux/jiffies.h>
#include <asm/uaccess.h>


#define MODULE_VERS "1.0"
#define MODULE_NAME "procfs_example"

#define FOOBAR_LEN 8

struct fb_data_t {
	char name[FOOBAR_LEN + 1];
	char value[FOOBAR_LEN + 1];
};


static struct proc_dir_entry *example_dir, *foo_file,
	*bar_file, *jiffies_file, *symlink;


struct fb_data_t foo_data, bar_data;


static int proc_read_jiffies(char *page, char **start,
			     off_t off, int count,
			     int *eof, void *data)
{
	int len;

	len = sprintf(page, "jiffies = %ld\n",
                      jiffies);

	return len;
}


static int proc_read_foobar(char *page, char **start,
			    off_t off, int count, 
			    int *eof, void *data)
{
	int len;
	struct fb_data_t *fb_data = (struct fb_data_t *)data;

	/* DON'T DO THAT - buffer overruns are bad */
	len = sprintf(page, "%s = '%s'\n", 
		      fb_data->name, fb_data->value);

	return len;
}


static int proc_write_foobar(struct file *file,
			     const char *buffer,
			     unsigned long count, 
			     void *data)
{
	int len;
	struct fb_data_t *fb_data = (struct fb_data_t *)data;

	if(count > FOOBAR_LEN)
		len = FOOBAR_LEN;
	else
		len = count;

	if(copy_from_user(fb_data->value, buffer, len))
		return -EFAULT;

	fb_data->value[len] = '\0';

	return len;
}


static int __init init_procfs_example(void)
{
	int rv = 0;

	/* create directory */
	example_dir = proc_mkdir(MODULE_NAME, NULL);
	if(example_dir == NULL) {
		rv = -ENOMEM;
		goto out;
	}
	
	example_dir->owner = THIS_MODULE;
	
	/* create jiffies using convenience function */
	jiffies_file = create_proc_read_entry("jiffies", 
					      0444, example_dir, 
					      proc_read_jiffies,
					      NULL);
	if(jiffies_file == NULL) {
		rv  = -ENOMEM;
		goto no_jiffies;
	}

	jiffies_file->owner = THIS_MODULE;

	/* create foo and bar files using same callback
	 * functions 
	 */
	foo_file = create_proc_entry("foo", 0644, example_dir);
	if(foo_file == NULL) {
		rv = -ENOMEM;
		goto no_foo;
	}

	strcpy(foo_data.name, "foo");
	strcpy(foo_data.value, "foo");
	foo_file->data = &foo_data;
	foo_file->read_proc = proc_read_foobar;
	foo_file->write_proc = proc_write_foobar;
	foo_file->owner = THIS_MODULE;
		
	bar_file = create_proc_entry("bar", 0644, example_dir);
	if(bar_file == NULL) {
		rv = -ENOMEM;
		goto no_bar;
	}

	strcpy(bar_data.name, "bar");
	strcpy(bar_data.value, "bar");
	bar_file->data = &bar_data;
	bar_file->read_proc = proc_read_foobar;
	bar_file->write_proc = proc_write_foobar;
	bar_file->owner = THIS_MODULE;
		
	/* create symlink */
	symlink = proc_symlink("jiffies_too", example_dir, 
			       "jiffies");
	if(symlink == NULL) {
		rv = -ENOMEM;
		goto no_symlink;
	}

	symlink->owner = THIS_MODULE;

	/* everything OK */
	printk(KERN_INFO "%s %s initialised\n",
	       MODULE_NAME, MODULE_VERS);
	return 0;

no_symlink:
	remove_proc_entry("tty", example_dir);
no_tty:
	remove_proc_entry("bar", example_dir);
no_bar:
	remove_proc_entry("foo", example_dir);
no_foo:
	remove_proc_entry("jiffies", example_dir);
no_jiffies:			      
	remove_proc_entry(MODULE_NAME, NULL);
out:
	return rv;
}


static void __exit cleanup_procfs_example(void)
{
	remove_proc_entry("jiffies_too", example_dir);
	remove_proc_entry("tty", example_dir);
	remove_proc_entry("bar", example_dir);
	remove_proc_entry("foo", example_dir);
	remove_proc_entry("jiffies", example_dir);
	remove_proc_entry(MODULE_NAME, NULL);

	printk(KERN_INFO "%s %s removed\n",
	       MODULE_NAME, MODULE_VERS);
}


module_init(init_procfs_example);
module_exit(cleanup_procfs_example);

MODULE_AUTHOR("Erik Mouw");
MODULE_DESCRIPTION("procfs examples");
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");