2017-2018-1 20155327 实验四 外设驱动程序设计

题目一

学习资源中全课中的“hqyj.嵌入式Linux应用程序开发标准教程.pdf”中的第十一章
提交康奈尔笔记的照片（可以多张）

题目二

在Ubuntu完成资源中全课中的“hqyj.嵌入式Linux应用程序开发标准教程.pdf”中的第十一章的test试验
提交编译，加载模块，卸载模块，测试运行的截图（要多张，全屏，体现学号信息）

实验过程

• 驱动程序代码：

#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/cdev.h>
#include <asm/uaccess.h>
#define     TEST_DEVICE_NAME    "test_dev"
#define        BUFF_SZ                1024/*全局变量*/
static struct cdev test_dev;
unsigned int major =0;
static char *data = NULL;/*读函数*/
static ssize_t test_read(struct file *file,
char *buf, size_t count, loff_t *f_pos)
{int len;if (count < 0 ){return -EINVAL;}len = strlen(data);count = (len > count)?count:len;if (copy_to_user(buf, data, count)) /* 将内核缓冲的数据拷贝到用户空间*/{return -EFAULT;}return count;
}/*写函数*/
static ssize_t test_write(struct file *file, const char *buffer,
size_t count, loff_t *f_pos)
{if(count < 0){return -EINVAL;}memset(data, 0, BUFF_SZ);count = (BUFF_SZ > count)?count:BUFF_SZ;if (copy_from_user(data, buffer, count)) /* 将用户缓冲的数据复制到内核空间*/{return -EFAULT;}return count;
}/*打开函数*/
static int test_open(struct inode *inode, struct file *file)
{printk("This is open operation\n");/* 分配并初始化缓冲区*/data = (char*)kmalloc(sizeof(char) * BUFF_SZ, GFP_KERNEL);if (!data){return -ENOMEM;}memset(data, 0, BUFF_SZ); return 0;
}/*关闭函数*/
static int test_release(struct inode *inode,struct file *file){printk("This is release operation\n");if (data){kfree(data); /* 释放缓冲区*/data = NULL; /* 防止出现野指针 */}return 0;
}/* 创建、初始化字符设备，并且注册到系统*/
static void test_setup_cdev(struct cdev *dev, int minor,struct file_operations *fops)
{int err, devno = MKDEV(major, minor);cdev_init(dev, fops);dev->owner = THIS_MODULE;dev->ops = fops;err = cdev_add (dev, devno, 1);if (err){printk (KERN_NOTICE "Error %d adding test %d", err, minor);}
}/* 虚拟设备的file_operations结构 */
static struct file_operations test_fops =
{.owner   = THIS_MODULE,.read    = test_read,.write   = test_write,.open    = test_open,.release = test_release,
};/*模块注册入口*/
int init_module(void)
{int result;dev_t dev = MKDEV(major, 0);if (major){/* 静态注册一个设备，设备号先前指定好，并设定设备名，用cat /proc/devices来查看 */result = register_chrdev_region(dev, 1, TEST_DEVICE_NAME);}else {result = alloc_chrdev_region(&dev, 0, 1, TEST_DEVICE_NAME);}if (result < 0) {printk(KERN_WARNING "Test device: unable to get major %d\n", major);return result;}test_setup_cdev(&test_dev, 0, &test_fops);printk("The major of the test device is %d\n", major);return 0;
}/*卸载模块*/
void cleanup_module(void)
{cdev_del(&test_dev);unregister_chrdev_region(MKDEV(major, 0), 1);printk("Test device uninstalled\n");
}

• 测试代码：

 /* test.c */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>
#define TEST_DEVICE_FILENAME        "/dev/test_dev"        /* 设备文件名*/
#define BUFF_SZ 1024                /* 缓冲大小 */int main()
{int fd, nwrite, nread;char buff[BUFF_SZ];        /*缓冲区*//* 打开设备文件 */fd = open(TEST_DEVICE_FILENAME, O_RDWR);if (fd < 0){perror("open");exit(1);}do{printf("Input some words to kernel(enter 'quit' to exit):");memset(buff, 0, BUFF_SZ);if (fgets(buff, BUFF_SZ, stdin) == NULL){perror("fgets");break;}buff[strlen(buff) - 1] = '\0';if (write(fd, buff, strlen(buff)) < 0) /* 向设备写入数据 */{perror("write");break;}if (read(fd, buff, BUFF_SZ) < 0)        /* 从设备读取数据 */{perror("read");break;}else{printf("The read string is from kernel:%s\n", buff);}} while(strncmp(buff, "quit", 4));close(fd);exit(0);}

实验截图

实验中遇到的问题及解决方法

• 实验时遇到权限不够时输入sudo来以管理员身份运行