2017-2018-1 20155333 《信息安全系统设计基础》实验四外设驱动程序设计

实验四外设驱动程序设计-1

• 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）

实验四外设驱动程序设计-2

• 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）
• 驱动程序代码：
  ```
  /* test_drv.c */

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;

/函数声明/
static ssize_t test_read(struct file file, char buf, size_t count, loff_t f_pos);
static ssize_t test_write(struct file file,const char buffer, size_t count,loff_t f_pos);
static int test_open(struct inode inode, struct file file);
static int test_release(struct inode inode,struct file file);

/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))
{
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))
{
return -EFAULT;
}
return count;
}

/打开函数/
static int test_open(struct inode inode, struct file file)
{
printk("This is open operation\n");
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);
data = NULL;
}
return 0;
}

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);
}

}

/* tests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)
{
    result = register_chrdev_region(dev, 1, TEST_DEVICE_NAME);
}
else 
{
    result = alloc_chrdev_region(&dev, 0, 1, TEST_DEVICE_NAME);
    major = MAJOR(dev);
}

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

include

include

include <sys/stat.h>

include <sys/types.h>

include

include

define TEST_DEVICE_FILENAME "/dev/test_dev"

define BUFF_SZ 1024

int main()
{
int fd, nwrite, nread;
char buff[BUFF_SZ];

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)
    {
        perror("write");
        break;
    }
    
    if (read(fd, buff, BUFF_SZ) < 0)
    {
        perror("read");
        break;
    }
    else
    {
        printf("The read string is from kernel:%s\n", buff);
    }
    
} while(strncmp(buff, "quit", 4));

close(fd);
exit(0);

}
```
运行截图：

实验中遇到的问题及解决方法

• 问题1：在执行./test_drv_load时提示权限不够。
• 解决方法：
  使用chmod+x ./test_drv_load
  加权限，在命令前面加上sudo执行。
• 问题2：Error :Removing 'test_drv':Device or resource busy
• 解决方法：未解决！