/* procfile.c 
 *   Variation of Ch 5.1 proc file module from
 *   Linux Kernel Module Programmer's Guide for 2.4 Kernel
 */

/* kernel module programming */
#ifndef MODULE
#define MODULE
#endif

#ifndef LINUX
#define LINUX
#endif

#ifndef __KERNEL__
#define __KERNEL__
#endif

#include <linux/module.h>    /* needed by all modules */
#include <linux/kernel.h>    /* needed for KERN_ALERT */
#include <linux/proc_fs.h>   /* working with the proc fs */


/* prototypes */
int my_get_info(char *sys_buf,
                char **user_buf,
                off_t file_pos,      /* position in user_buf */
                int buf_len);        /* for system buf_len ?? */
int my_read_proc(char *sys_buffer,   /* system supplied buffer */
                 char **user_buffer, /* user provided buffer */
		 off_t file_pos,     /* position in proc file read */
		 int buflen,         /* for system buf_len ?? */
		 int *eof,           /* I could guess */
		 void *data);        /* no clue */
int init_module(void);
void cleanup_module(void);


/* What is this old one for, then? */
int my_get_info(char *sys_buf,
                char **user_buf,
                off_t file_pos,      /* position in user_buf */
                int buf_len)         /* for system buf_len ?? */
{ printk(KERN_ALERT "my_get_info of proc module: entering.\n");
  printk(KERN_ALERT "my_get_info of proc module: leaving.\n");
  return 0;
}

/* My function to supply the proc file read information */
int my_read_proc(char *sys_buffer,   /* system supplied buffer */
                 char **user_buffer, /* user provided buffer */
		 off_t file_pos,     /* position in proc file read */
		 int buflen,         /* buffer size (system buffer?) */
		 int *eof,           /* I could guess */
		 void *data)         /* no clue */
{ printk(KERN_ALERT "my_read_proc of proc module: entering.\n");
  printk(KERN_ALERT "my_read_proc of proc module: leaving.\n");
  return 0;
}


/* Directory structure for proc files (a psuedo inode?) 
 * This is created dynamically in kernel 2.4, see init_module below */
struct proc_dir_entry *my_proc_file;

/*
struct proc_dir_entry my_proc_file =
{ 0,            * inode number - 0 means system will auto-generate *
  4,            * length of file name *
  "test",       * file name *
  S_IFREG | S_IRUGO, * file mod - regular file with ugo read permission *
  1,            * number of links *
  0,0,          * uid, gid - make both root *
  0,            * size of file as reported by ls (most proc files report 0) *
  NULL,         * inode operations - none *
  NULL,         * file operations - none *
  my_get_info,  * I supply the get_info function defined below *
  NULL,         * no module owner - I hope this works *
  NULL, NULL, NULL, * struct proc_dir_entry *next, *parent, *subdir; *
  NULL,         * void *data; *
  my_read_proc, * read_proc - do I supply the read_proc function? What for? *
  NULL          * write_proc *
  * 0,          * atomic_t count; use count (what value? Where is atomic_t?) *
  * 0,          * int deleted; delete flag (what value?) *
  * {0,0}       * kdev_t rdev;  see kdev_t.h the type is a struct of two short int *
};
*/


/* create_proc_read_entry registers the read function. See proc_fs.h */
int init_module(void)
{ printk(KERN_ALERT "procfile module loaded\n");
  my_proc_file = create_proc_read_entry( "test",  /* proc file name */
                                          0444,   /* uid gid mode */
                                          NULL,   /* dir entry base */
					  my_read_proc, /* read function */
					  NULL);  /* data for function ?? */

  /* A non-zero return means init_module failed; module can't be loaded */
  if (my_proc_file == NULL)
    return -ENOMEM;
  return 0;
}

void cleanup_module(void)
{ printk(KERN_ALERT "procfile module unloaded\n");
  remove_proc_entry("test", NULL); /* file name and parent */
}

MODULE_LICENSE("GPL");