Proc FS

/*
 * $Id: hello2.c,v 1.8 2001/07/18 22:28:18 rubini Exp $
 */
#include <linux/init.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/kernel.h>    /* printk() */
#include <linux/proc_fs.h>
#include <asm/uaccess.h>
 
#define MYNAME "driver/my_proc_file"
 
static struct proc_dir_entry *myproc = NULL;
 
static char msg[255] = "hello";
 
module_param_string(msg,msg,255,0);
 
int myreadtest(char *page,char **start,off_t off,int count,int *eof,void *data)
{
    printk("page=%x off=%d count=%d \n",page,off,count);
    int len=sprintf(page+off -1,"msg=%s\n",msg);
    printk("len after=%d\n",len);
    if(len <= off+count)
        *eof = 1;
 
    *start = page +off;
    len-=off;
    if(len > count) len=0;
    if(len < 0) len=0;  
    printk("len=%d\n",len);
    return len;
}
int myread(char *page,char **start,off_t off,int count,int *eof,void *data)
{
    int len =0;
    if(off <= 0){
        len=sprintf(page,"msg=%s\n",msg);
    }
    return len;
}
 
int mywrite(struct file *file, const char *buffer, unsigned long count,
           void *data)
{
    printk("buffer=%x\n",buffer);
    if ( copy_from_user(msg, buffer, count) ) {
        return -EFAULT;
    }
    strcpy(msg+count,data);
    msg[count] = 0;
    return count;
}
static int
hello_init (void)
{
 
  printk (KERN_INFO "Hello loaded sucessfuly.\n");
  myproc = create_proc_entry(MYNAME,0,NULL);
  myproc->read_proc = myreadtest;
  myproc->write_proc = mywrite;
  myproc->data = "custom data";
 
  return 0;
 
}
 
static void
hello_cleanup (void)
{
 
  printk (KERN_INFO "hello unloaded succefully.\n");
  remove_proc_entry(MYNAME, NULL);
 
}
 
module_init (hello_init);
module_exit (hello_cleanup);
MODULE_LICENSE("Dual BSD/GPL");