Linux操作方法集接口（read，write）

<asm-generic/uaccess.h>
应用层调用 read —>>> 应用层想读取数据 —>>> 这件事情是内核中驱动完成
—>>> copy_to_user
应用层调用 write —>>> 应用层想写取数据 —>>> 这件事情是内核中驱动完成
—>>> copy_from_user

//驱动中的read、write接口实现
ssize_t demo_read(struct file *filp, char __user *buf, size_t size, loff_t *off){ 
if(size > kbufcount)
{   
size = kbufcount; 
} if(copy_to_user(buf, k_buf, size)){   
printk(KERN_ERR "copy_to_user failed...\n");    
return -EAGAIN; 
} 
kbufcount = 0;  
printk(KERN_DEBUG "---%s---%s---%d---\n",__FILE__,__func__,__LINE__); 
return size;}ssize_t demo_write(struct file *filp, const char __user *buf, size_t size, loff_t *off){ 
if(size > KBUFSIZE-1){    
size = KBUFSIZE-1;  
} 
if(copy_from_user(k_buf,buf, size)){    
printk(KERN_ERR "copy_from_user failed...\n");    
return -EAGAIN; 
}
kbufcount = size; 
printk(KERN_INFO "demo_write->copy_from_user:%s\n",k_buf);    
printk(KERN_DEBUG "---%s---%s---%d---\n",__FILE__,__func__,__LINE__); 
return size;
}
//应用层测试代码char buf[] = "aaaaaaaaaaaaa";
char r_buf[32];
int main(int argc, const char *argv[]){    int fd = open("/dev/cdev_demo2",O_RDWR);    
if(fd < 0){       
perror("open");        
return -1;    
}
write(fd,buf,strlen(buf));                                                                                                                              close(fd);
    return 0;}