Linux 添加设备驱动程序

　　1.创建驱动文件my_drive.c

#include "linux/kernel.h"
#include "linux/module.h"
#include "linux/fs.h"
#include "linux/init.h"
#include "linux/types.h"
#include "linux/errno.h"
#include "linux/uaccess.h"
#include "linux/kdev_t.h"
 
#define MAX_SIZE 1024
 
int my_open(struct inode *inode, struct file *file);
int my_release(struct inode *inode, struct file *file);
ssize_t my_read(struct file *file, char __user *user, size_t t, loff_t *f);
ssize_t my_write(struct file *file, const char __user *user, size_t t, loff_t *f);
 
char message[MAX_SIZE] = "my drive start to work";  //打开设备时会显示的消息
int device_num;//设备号
char* devName = "my_drive";//设备名
 
struct file_operations pStruct =
{ 
    open:my_open, 
    release:my_release, 
    read:my_read, 
    write:my_write, 
};
 
/* 注册 */
int init_module()
{
    int ret;
 
    ret = register_chrdev(0, devName, &pStruct);
    if (ret < 0)
    {
        printk("failed to register my drive.
");
        return -1;
    }
    else
    {
        printk("my drive has been registered!
");
        printk("id: %d
", ret);
        device_num = ret;
 
        return 0;
    }
}
 
//注销
void cleanup_module()
{
    unregister_chrdev(device_num, devName);
    printk("unregister successful.
");
}
 
 
//打开
int my_open(struct inode *inode, struct file *file)
{
    printk("open my_drive OK!
");
    try_module_get(THIS_MODULE);
    return 0;
}
 
//关闭
int my_release(struct inode *inode, struct file *file)
{
    printk("Device released!
");
    module_put(THIS_MODULE);
 
    return 0;
}
 
 
//读设备里的信息
ssize_t my_read(struct file *file, char __user *user, size_t t, loff_t *f)
{
    if(copy_to_user(user,message,sizeof(message)))
    {
        return -2;
    }
    return sizeof(message);
}
 
//向设备里写信息
ssize_t my_write(struct file *file, const char __user *user, size_t t, loff_t *f)
{
    if(copy_from_user(message,user,sizeof(message)))
    {
        return -3;
    }
    return sizeof(message);
}

　　2.同目录下创建Makefile

obj-m := my_drive.o    #这里是上面所创建的c文件名.o
    PWD := $(shell pwd)
    KERNELDIR := /usr/src/linux-4.14    #你要安装mod的内核版本 
all:
    make -C $(KERNELDIR) M=$(PWD) modules
 
 
.PHONY: clean
clean:
    rm -rf *.o *~ core *.ko *.mod.c modules.order Module.symvers

　　3.使用make生成驱动程序

　　4.插入内核模块insmod my_drive.ko

　　5.查看内核输出日志dmesg，获取设备号

　　6.根据输出的设备号，创建设备mknod /dev/my_drive c 245 0　(245为设备号)

　　7.编写测试程序

test.c

　　8.效果　

　　

　　9.卸载设备和模块

　　rm /dev/my_drive

　　rmmod my_drive