以阻塞方式对IO文件进行读取(test.c读取，test2.c发送数据)

实验结果

执行test.c生成的pro1可执行文件，光标显示处于阻塞状态
执行test2.c生成的pro2可执行文件，test.c处打印 hello dhl

三级标题test.c

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


int main(int argc, char const *argv[])
{
    char buf[128] = {0};
    int fd = open("/dev/myled0", O_RDWR);
    if (fd < 0)
    {
        printf("打开设备文件失败\n");
        exit(-1);
    }
    while (1)
    {
        memset(buf,0,sizeof(buf));//清空
        read(fd,buf,sizeof(buf)); 	//读取数据
        printf("buf:%s\n",buf);
    }

    close(fd);

    return 0;
}

三级标题test2.c

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


int main(int argc, char const *argv[])
{
    char buf[128] = "hello dhl";
    int fd = open("/dev/myled0", O_RDWR);
    if (fd < 0)
    {
        printf("打开设备文件失败\n");
        exit(-1);
    }

    write(fd,buf,sizeof(buf)); 	//写数据.模拟传感器获取到数据
    close(fd);

    return 0;
}

三级标题myled0.c

#include <linux/init.h>
#include <linux/module.h>
#include<linux/fs.h>
#include<linux/device.h>
#include<linux/cdev.h>
#include<linux/slab.h>
#include<linux/io.h>
#include<linux/uaccess.h>

struct cdev *cdev; 		//字符设备空间首地址
unsigned int major=500; //静态申请设备号
unsigned int minor=0;//次设备号的起始值
dev_t devno; 		//动态申请设备号
struct class *cls;  //接收注册结构体的地址
struct device *dev; //设备号
char kbuf[128] = {0};  //硬件数据
//定义等待队头
wait_queue_head_t wq_head; 	//等待队列
unsigned int condition = 0; //硬件准备信号

int mycdev_open(struct inode *inode, struct file *file)
{
    printk("%s:%s:%d\n", __FILE__, __func__, __LINE__);
    return 0;
}

ssize_t mycdev_read(struct file *file, char *ubuf, size_t size, loff_t *lof)
{
    int ret;
    if(sizeof(kbuf) < size)
        size = sizeof(kbuf);
    wait_event_interruptible(wq_head, condition); //进程切换为休眠状态

    ret = copy_to_user(ubuf, kbuf, size);
    if(ret)
    {
        printk("copy_to_user failed\n");
        return -EIO;
    }
    printk("%s:%s:%d\n", __FILE__, __func__, __LINE__);
    condition = 0; //下次事件还没准备好
    return 0;
}
ssize_t mycdev_write(struct file *file, const char *ubuf, size_t size, loff_t *lof)
{
    int ret;
    if(sizeof(kbuf) < size)//判断用户空间的需求是否能被驱动满足，满足不了就给能给的最好的
        size = sizeof(kbuf);
    ret = copy_from_user(kbuf, ubuf, size);
    if(ret)
    {
        printk("copy_from_user filed\n");
        return -EIO;
    }

    condition = 1; //表示硬件数据准备就绪
    wake_up_interruptible(&wq_head);    //唤醒休眠的进程

    return 0;
}

int mycdev_close(struct inode *inode, struct file *file)
{
    printk("%s:%s:%d\n", __FILE__, __func__, __LINE__);
    return 0;
}

// 定义操作方法结构体变量并赋值
struct file_operations fops = {

    .open = mycdev_open,
    .read = mycdev_read,
    .write = mycdev_write,
    .release = mycdev_close,
};

static int __init mycdev_init(void)   //寄存器地址映射和初始化
{
    int ret; 				//ret返回错误码 
    //初始化等待队列头
    init_waitqueue_head(&wq_head);
/*
	// 映射物理地址
    vir_gpioe = ioremap(GPIOE, sizeof(gpio_t));
    if (vir_gpioe == NULL)
    {
        printk("MODER寄存器映射失败\n");
        return -EFAULT;
    }

    vir_rcc = ioremap(RCC, 4);
    if (vir_rcc == NULL)
    {
        printk("RCC寄存器映射失败\n");
        return -EFAULT;
    }

    vir_gpiof = ioremap(GPIOF, sizeof(gpio_t));
    if (vir_gpiof == NULL)
    {
        printk("MODER寄存器映射失败\n");
        return -EFAULT;
    }
    printk("寄存器映射成功\n");
*/
    //1.分配字符设备驱动对象空间  cdev_alloc
    cdev=cdev_alloc(); 		//字符设备空间首地址
    if(cdev==NULL)
    {
        printk("申请字符设备驱动对象空间失败\n");
        ret=-EFAULT;
        goto out1;
    }
    printk("字符设备驱动对象申请成功\n");

    //2.字符设备驱动对象部分初始化  cdev_init
    cdev_init(cdev,&fops);

    //3.申请设备号  register_chrdev_region/alloc_chrdev_region
    if(major>0)//静态申请设备号
    {
        ret=register_chrdev_region(MKDEV(major,minor),1,"myled0"); //设备号需要是组合出来的,次设备数量，设备文件名
        if(ret)
        {
            printk("静态指定设备号失败\n");
            goto out2;
        }
    }
    else//动态申请设备号
    {
        ret=alloc_chrdev_region(&devno,minor,1,"myled0");   //动态申请设备号，次设备号，设备数量，文件名
         if(ret)
        {
            printk("动态申请设备号失败\n");
            goto out2;
        }
        major=MAJOR(devno); 	//根据设备号得到主设备号
        minor=MINOR(devno); 	//根据设备号得到次设备号
    }
    printk("申请设备号成功\n");

    //4.注册字符设备驱动对象  cdev_add()
    ret=cdev_add(cdev,MKDEV(major,minor),1); //字符设备，设备号，设备数量
    if(ret)
    {
        printk("注册字符设备驱动对象失败\n");
        goto out3;
    }
    printk("注册字符设备驱动对象成功\n");

    //5.向上提交目录
    cls=class_create(THIS_MODULE,"myled0"); //指向自身的指针，文件名
    if(IS_ERR(cls))
    {
        printk("向上提交目录失败\n");
        ret=-PTR_ERR(cls);
        goto out4;
    }
    printk("向上提交目录成功\n");

    //6.向上提交设备节点
    dev=device_create(cls,NULL,MKDEV(major,0),NULL,"myled0"); //创建设备节点
    if(IS_ERR(dev))
    {
        printk("向上提交节点信息失败\n");
        ret=-PTR_ERR(dev);
        goto out5;
    }
    printk("向上提交设备节点信息成功\n");
/*
     (*vir_rcc) |= (0x3 << 4);
    // 寄存器初始化led1
    vir_gpioe->moder &= (~(0x3 << 20));
    vir_gpioe->moder |= (0x1 << 20);
    vir_gpioe->odr &= (~(0x1 << 10));
    printk("LED1硬件寄存器初始化成功\n");
    */
    return 0;

out5:
    //销毁上面提交的设备信息
    device_destroy(cls,MKDEV(major,0));
    class_destroy(cls);
out4:
    cdev_del(cdev);
out3:
    unregister_chrdev_region(MKDEV(major,minor),1);
out2:
    kfree(cdev);
out1:
    return ret;
}
static void __exit mycdev_exit(void)
{
    //1.销毁设备信息  device_destroy
    device_destroy(cls,MKDEV(major,0));
    //2.销毁目录  class_destroy
    class_destroy(cls);
    //3.注销对象  cdev_del()
    cdev_del(cdev);
    //4.释放设备号   unregister_chrdev_region()
    unregister_chrdev_region(MKDEV(major,minor),1);
    //5.释放对象空间  kfree()
    kfree(cdev);
/*
	// 取消寄存器地址映射
    iounmap(vir_gpioe);
    iounmap(vir_rcc);
    iounmap(vir_gpiof);
    // 销毁设备节点信息
	device_destroy(cls, MKDEV(major, 0));
	// 销毁字符设备驱动
    class_destroy(cls);
    // 字符设备驱动的注销
    unregister_chrdev(major, "led0");
*/
}
module_init(mycdev_init);
module_exit(mycdev_exit);
MODULE_LICENSE("GPL");