#ifndef __KERNEL__
#define __KERNEL__
#endif
#ifndef MODULE
#define MODULE
#endif
#define __NO_VERSION__
#include <linux/kernel.h>
#include <linux/module.h>
#if CONFIG_MODVERSIONS == 1
#define MODVERSIONS
#include <linux/modversions.h>
#endif
#include <linux/fs.h>
#ifndef KERNEL_VERSION
#define KERNEL_VERSION(a,b,c) ((a)*65536+(b)*256+(c))
#endif
/* Conditional compilation. LINUX_VERSION_CODE is
* the code (as per KERNEL_VERSION) of this version. */
#if LINUX_VERSION_CODE > KERNEL_VERSION(2,2,0)
#include <asm/uaccess.h> /* for put_user */
#endif
#define SUCCESS 0
#define DEVICE_NAME "kueng_char_dev"
#define BUF_LEN 50
static int Device_Open =0;
static char Message[BUF_LEN];
static int Major;
static int mydev_open(struct inode *inode,struct file *file)
{
static int counter = 0;
if(Device_Open)
return -EBUSY;
Device_Open=1;
MOD_INC_USE_COUNT;
return 0;
}
static int mydev_release(struct inode *inode,struct file *file)
{
Device_Open=0;
MOD_DEC_USE_COUNT;
return 0;
}
static ssize_t mydev_read(struct file *file,char *buffer, size_t length ,loff_t *f_pos)
{
int bytes_read=0;
if(verify_area(VERIFY_WRITE,buffer,length)==-EFAULT)
return -EFAULT;
copy_to_user(buffer,Message,length);
return bytes_read;
}
static ssize_t mydev_write(struct file *file, const char *buffer,size_t length,loff_t *f_pos)
{
int i = BUF_LEN>length?BUF_LEN:length;
if(verify_area(VERIFY_READ,buffer,length)==-EFAULT)
return -EFAULT;
copy_from_user(Message,buffer,i);
return length;
}
struct file_operations Fops = {
release: mydev_release,
open: mydev_open,
read: mydev_read,
write:mydev_write
};
int init_module(void)
{
Major = register_chrdev(0,DEVICE_NAME,&Fops);
if(Major<0){
printk("%s device failed with %d\n","Sorry, registering the character",Major);
return Major;
}
printk("%s The major device number is %d\n","Registeration is a success.",Major);
return 0;
}
void cleanup_module(void)
{
int ret;
ret = unregister_chrdev(Major,DEVICE_NAME);
if(ret<0)
printk("Error in unregister_chrdev: %d\n",ret);
}
MODULE_LICENSE("GPL");
MODULE_AUTHOR("KUENG");
