驱动——ioctl数组及结构体传递

news2024/12/30 0:33:07

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<linux/init.h>
#include<linux/module.h>
#include<linux/fs.h>
#include<linux/uaccess.h>
#include<linux/io.h>
#include"./led.h"
#include<linux/device.h>

#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 <stdio.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<fcntl.h>
#include<unistd.h>
#include<stdlib.h>
#include<string.h>
#include<sys/ioctl.h>
#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