/* * 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");