嵌入式第二次测试解答

具体操作流程参考上篇文章：
嵌入式实战—应用open调用内核open，应用close调用内核close通信程序
hello.c需要修改为：

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/cdev.h>
#include <linux/kdev_t.h>
#include <linux/fs.h>   //file_operations 
MODULE_LICENSE ("GPL");
int i = 10;
struct file_operations ops;
struct cdev mycdev;
int major = 254;
int minor = 5;
dev_t dev;
int j= 0;
int k= 0; 
int open(struct inode *pinode,struct file *pfile)
{
    j++;
    printk(KERN_INFO "liuhangyu myopen run j= %d\n",j);
    return 0;
} 
int close(struct inode *pinode,struct file *pfile)
{
    k++;
    printk(KERN_INFO "liuhangyu myclose run k= %d\n",k);
    return 0;
}
void myuart_init(void)
{
    int ret;
    mycdev.owner=THIS_MODULE;
    dev = MKDEV(major,minor);
    ret = register_chrdev_region(dev,5,"myuart");
    if(ret==-1)
    {
        printk(KERN_INFO "dev cant't use\n");
        ret = alloc_chrdev_region(&dev,5,1,"myuart");   //automatic allocation dev
        if(ret==0)
        {
            printk(KERN_INFO "alloc : major= %d\n",MAJOR(dev));
        }
        else
        {
            printk(KERN_INFO "alloc error\n");
            return ; 
        }
    }
    else
        {
        printk(KERN_INFO "dev can use\n");
        }
    ops.owner=THIS_MODULE;
    ops.open=open;
    ops.release=close;
    cdev_init(&mycdev,&ops);
    cdev_add(&mycdev,dev,5);  //mycdev send dev,equipment 1
    return ;
 }  
 static int  __init hello_init (void)
{
    i ++;
    myuart_init();    //init
    printk (KERN_INFO "driver init,i = %d\n",i);
    return 0;
}

static void  __exit hello_exit (void)
{
    i ++; 
    printk (KERN_INFO "driver exit,i = %d\n",i);
    unregister_chrdev_region(dev,5);
    cdev_del(&mycdev); 
}

module_init (hello_init);
module_exit (hello_exit);

app.c需要修改为

#include "stdio.h"
#include "fcntl.h"
#include "unistd.h"
#include "stdlib.h"
int main()
{
    int fd;
    int q = 0;
    while(1)
    {
        fd = open("./myuart",O_RDWR,0777) ;
        if(fd==-1)
        {
            printf("open error\n");
            return -1;
         }
         q ++;
         printf("liuhangyu open  run q = %d\n",q);
         sleep (3);
         close(fd);
         q ++;
         printf("liuhangyu close  run q = %d\n",q);
         sleep (3);
    }
    return 0;
}

直接在此输入下面这个命令，才能./app
mknod ./myuart c 254 5