1、ioctl函数是用户程序来控制设备的函数

int ioctl(int fd, unsigned long request, ...);

函数功能：设备控制

参数：

@fd:文件描述符

@request：请求码

@...:可变参数 需要传递地址

返回值：成功返回0，失败返回-1，并且置位错误码

2、内核层与ioctl对应的接口函数：

long (*unlocked_ioctl) (struct file *file, unsigned int cmd, unsigned long arg)

3、代码实现：ioctl传递字符数组与结构体

1>对数组和结构体命令码进行封装：

#ifndef __LED_H__
#define __LED_H__typedef struct{int width;int high;
}image_t;#define UACCESS_BUF _IOW('a',1,char[128])
#define UACCESS_STRUCT _IOWR('b',0,image_t)#endif

 2>在long mydev_ioctl (struct file *file, unsigned int cmd, unsigned long arg)接口函数内，使用copy_from_user接收用户空间拷贝过来的信息，并进行打印，再使用copy_to_user函数将修改后的结构体信息拷贝到用户空间

#include
#include
#include
#include
#include
#include"./led.h"
#include#define GNAME "mydev"
int major;
char kbuf[128]={0};
struct class *cls=NULL;
struct device *dev=NULL;int mydev_open(struct inode *inode, struct file *file)
{//printk("%s:%s:%d\n",__FILE__,__func__,__LINE__);return 0;
}
long mydev_ioctl(struct file *file,unsigned int cmd,unsigned long arg)
{int ret;image_t image;switch(cmd){case UACCESS_BUF:ret = copy_from_user(kbuf,(void*)arg,sizeof(char)*128);if(ret){printk("copy from user char error\n");return -EIO;}printk("kbuf=%s\n",kbuf);break;case UACCESS_STRUCT:ret = copy_from_user(&image,(void*)arg,sizeof(image_t));if(ret){printk("copy from user image_t error\n");return -EIO;}printk("image_t.width=%d  image_t.high=%d\n",image.width,image.high);image.width+=10;image.high+=10;ret = copy_to_user((void*)arg,&image,sizeof(image_t));if(ret){printk("copy to user image_t error\n");return -EIO;}break;}return 0;
}
int mydev_close(struct inode *inode, struct file *file)
{//printk("%s:%s:%d\n",__FILE__,__func__,__LINE__);return 0;
}
struct file_operations fops={.open=mydev_open,.unlocked_ioctl=mydev_ioctl,.release=mydev_close,
};static int __init mydev_init(void)
{major=register_chrdev(0,GNAME,&fops);if(major<0){printk("register file\n");return major;}printk("major=%d\n",major);cls = class_create(THIS_MODULE,GNAME);if(IS_ERR(cls)){return PTR_ERR(cls);}dev = device_create(cls,NULL,MKDEV(major,0),NULL,GNAME);if(IS_ERR(dev)){return PTR_ERR(dev);}return 0;
}static void __exit mydev_exit(void)
{device_destroy(cls,MKDEV(major,0));class_destroy(cls);unregister_chrdev(major,GNAME);
}module_init(mydev_init);
module_exit(mydev_exit);MODULE_LICENSE("GPL");

 3>编写用户程序，通过ioctl函数传递信息给内核空间，从而达到想要的操作结果，并进行打印

#include 
#include
#include
#include
#include
#include
#include
#include
#include"led.h"
char buf[128] = "问灵十三年";int main(int argc, const char *argv[])
{int fd = -1;int i=0;int witch;image_t image={20,1024};fd = open("/dev/mydev",O_RDWR);if(-1 == fd){perror("open is error");exit(1);}ioctl(fd,UACCESS_BUF,buf);ioctl(fd,UACCESS_STRUCT,&image);printf("image_t.width=%d  image_t.high=%d\n",image.width,image.high);close(fd);return 0;
}

 4>通过dmesg查看内核层的打印信息，结果如下所示，应用层传递的数组信息以及结构体信息成功传递到内核层

5>执行应用层程序，终端打印结构体信息+10后的信息