#include <linux/module.h> 
#include <linux/kernel.h> 
#include <linux/fs.h> 
#include <linux/cdev.h> 
 
static struct cdev chr_dev; 
static dev_t ndev; 
 
static int chr_open(struct inode* nd, struct file* filp) 
{ 
  int major ; 
  int minor; 
   
  major = MAJOR(nd->i_rdev); 
  minor = MINOR(nd->i_rdev); 
   
  printk("chr_open, major = %d, minor = %d\n", major, minor); 
  return 0; 
} 
 
static ssize_t chr_read(struct file* filp, char __user* u, size_t sz, loff_t* off) 
{ 
  printk("chr_read process!\n"); 
  return 0; 
} 
 
struct file_operations chr_ops = { 
  .owner = THIS_MODULE, 
  .open = chr_open, 
  .read = chr_read 
}; 
 
static int demo_init(void) 
{ 
  int ret; 
   
  cdev_init(&chr_dev, &chr_ops); 
  ret = alloc_chrdev_region(&ndev, 0, 1, "chr_dev"); 
  if(ret < 0 ) 
  { 
    return ret; 
  } 
   
  printk("demo_init(): major = %d, minor = %d\n", MAJOR(ndev), MINOR(ndev)); 
  ret = cdev_add(&chr_dev, ndev, 1); 
  if(ret < 0) 
  { 
    return ret; 
  } 
   
  return 0; 
} 
 
static void demo_exit(void) 
{ 
  printk("demo_exit process!\n"); 
  cdev_del(&chr_dev); 
  unregister_chrdev_region(ndev, 1); 
} 
 
module_init(demo_init); 
module_exit(demo_exit); 
 
MODULE_LICENSE("GPL"); 
MODULE_AUTHOR("feixiaoxing@163.com"); 
MODULE_DESCRIPTION("A simple device example!"); 

ifneq ($(KERNELRELEASE),) 
obj-m := char.o 
 
else 
PWD := $(shell pwd) 
KVER := $(shell uname -r) 
KDIR := /lib/modules/$(KVER)/build 
all: 
  $(MAKE) -C $(KDIR) M=$(PWD) modules 
clean: 
  rm -rf .*.cmd *.o *.mod.c *.ko .tmp_versions modules.* Module.* 
endif 

#include <stdio.h> 
#include <fcntl.h> 
#include <unistd.h> 
 
#define CHAR_DEV_NAME "/dev/chr_dev" 
 
int main() 
{ 
  int ret; 
  int fd; 
  char buf[32]; 
 
  fd = open(CHAR_DEV_NAME, O_RDONLY | O_NDELAY); 
  if(fd < 0) 
  { 
    printf("open failed!\n"); 
    return -1; 
  } 
   
  read(fd, buf, 32); 
  close(fd); 
   
  return 0; 
}