드라이버 Read Write

simple.c

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <asm/uaccess.h>
 
int simple_open(struct inode* pinode, struct file* pfile)
{
    printk(KERN_INFO "Open Simple\n");
    return 0;
}
 
int simple_release(struct inode* pinode, struct file* pfile)
{
    printk(KERN_INFO "Release Simple\n");
    return 0;
}
 
ssize_t simple_read(struct file* pfile, char* ubuf, size_t length, loff_t* offset)
{
    int result;
    char message[20] = "Lee Ho Jun";
    result = copy_to_user(ubuf, message, length);
    if(result <0)
    {
        printk(KERN_ERR "Copy_to_user Error!\n");
        return result;    
    }
    return 0;
}
ssize_t simple_write(struct file* pfile, const char* ubuf, size_t length, loff_t* offset)
{
    char message[20];
    int result;
    result = copy_from_user(message,ubuf,length);
    if(result <0)
    {
        printk(KERN_ERR "Copy_to_user Error!\n");
        return result;    
    }
    printk(KERN_INFO "from user : %s\n",message);
    return 0;
}
struct file_operations simple_fops ={
    read : simple_read,    
    write : simple_write,
    open : simple_open,
    release : simple_release,
};
 
 
int simple_init(void)
{
    int result;
    result = register_chrdev(249,"simple_driver", &simple_fops);
 
    if(result<0)
    {
        printk(KERN_ERR "Registration Error\m");    
        return result;    
    }
    printk(KERN_INFO "Hello Simple\n");
 
    return 0;
}
 
int simple_exit(void)
{
    unregister_chrdev(249,"simple_driver");
    printk("Bye _ Simple\n");
    return 0;
}
module_init(simple_init);
module_exit(simple_exit);
MODULE_LICENSE("GPL");
 

simple 드라이버를 만드는 소스이다. 

Read() 함수는 호출되면 user 에게  message에 저장되어 있는 문자열을 넘겨준다.

Write() 함수는 user가 호출하면서 넘겨준 문자열을 넘겨 받게 되고 해당 문자열을 커널 에서 출력한다.

test.c

#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
 
int main(void)
{
    int fd;
    char buffer[20];
    char number[20] = "5172174";
 
    fd = open("/dev/simple",O_RDWR);
    if(fd<0)
    {
        perror("open");
        exit(1);    
    }
    write(fd,number,strlen(number)+1);
    read(fd,buffer,20);
    printf("from kernel : %s\n",buffer);
    close(fd);
    return 0;
}
 

실행 결과