#include <linux/proc_fs.h>

struct proc_dir_entry* create_proc_entry(const char* name, mode_t mode,
                                         struct proc_dir_entry* parent);

struct proc_dir_entry* proc_symlink(const char* name,
                        struct proc_dir_entry* parent, const char* dest);

struct proc_dir_entry* proc_mknod(const char* name, mode_t mode,
                                 struct proc_dir_entry* parent, kdev_t rdev);

struct proc_dir_entry* proc_mkdir(const char* name,
                                  struct proc_dir_entry* parent);

void remove_proc_entry(const char* name, struct proc_dir_entry* parent);

struct proc_dir_entry* entry;

entry->read_proc  = read_proc_foo;
entry->write_prpc = write_proc_foo;

int read_func(char* page, char **start, off_t off,
              int count, int* eof, void* data);

int write_func(struct file* file, const char* buffer,
               unsigned long count, void* data);

struct proc_dir_entry* entry;
struct my_file_data *file_data;

file_data = kmalloc(sizeof(struct my_file_data), GFP_KERNEL);
entry->data = file_data;

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

        if(data == file_data) {
                /* special case for this file */
        } else {
                /* normal processing */
        }

        return len;
}

struct proc_dir_entry* create_proc_read_entry(const char* name, mode_t mode,
          struct proc_dir_entry* parent, read_proc_t* read_proc, void* data);

struct proc_dir_entry* entry;

entry->owner = THIS_MODULE;

struct proc_dir_entry* entry;

entry->mode =  S_IWUSR |S_IRUSR | S_IRGRP | S_IROTH;
entry->uid = 0;
entry->gid = 100;

/*
 * 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/sched.h>
#include <asm/uaccess.h>


#define MODULE_VERSION "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, *tty_device, *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;

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

        MOD_DEC_USE_COUNT;

        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;

        MOD_INC_USE_COUNT;
        
        len = sprintf(page, "%s = '%s'\n",
                      fb_data->name, fb_data->value);

        MOD_DEC_USE_COUNT;

        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;

        MOD_INC_USE_COUNT;

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

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

        fb_data->value[len] = '\0';

        MOD_DEC_USE_COUNT;

        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 tty device */
        tty_device = proc_mknod("tty", S_IFCHR | 0666,
                                example_dir, MKDEV(5, 0));
        if(tty_device == NULL) {
                rv = -ENOMEM;
                goto no_tty;
        }
        
        tty_device->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_VERSION);
        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_VERSION);
}


module_init(init_procfs_example);
module_exit(cleanup_procfs_example);

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

EXPORT_NO_SYMBOLS;