2018-2019-1 20165205 20165233 实验四 外设驱动程序设计

实验四 外设驱动程序设计

任务一

实验要求

1. 学习资源中中全课中的“hqyj.嵌入式Linux应用程序开发标准教程.pdf”中的第十一章
2. 提交康奈尔笔记
   
   

任务二

实验要求

1. 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
2. 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）

• 实验内容

  • 该实验要求实现对虚拟设备（一段内存）的打开、关闭、读写的操作，并要通过编写测试程序来测试虚拟设备及其驱动运行是否正常。

• 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
  
    static struct cdev test_dev;
    unsigned int major =0;
    static char *data = NULL;
    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);
    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;
    }
    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;
    }
    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;
    }
    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);
        }
    }
    static struct file_operations test_fops = 
    {
        .owner   = THIS_MODULE,
        .read    = test_read,
        .write   = test_write,
        .open    = test_open,
        .release = test_release,
    };
    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;
    }
    void cleanup_module(void) 
    {
        cdev_del(&test_dev);
        unregister_chrdev_region(MKDEV(major, 0), 1);
        printk("Test device uninstalled\n");
    }
  

• Makefile

   	ifeq ($(KERNELRELEASE),)
   	KERNELDIR ?= /lib/modules/$(shell uname -r)/build
   	PWD := $(shell pwd)
   	modules:
   		$(MAKE) -C $(KERNELDIR) M=$(PWD) modules
   	modules_install:
   		$(MAKE) -C $(KERNELDIR) M=$(PWD) modules_install
   	clean:
   		rm -rf *.o *~ core .depend .*.cmd *.ko *.mod.c .tmp_versions
   	.PHONY: modules modules_install clean
   	else
   	obj-m := test_drv.o /* 将生成的模块为 test_drv.ko*/
   	endif
  

• test.c

    /* 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"
    #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);
    }
  

• test_drv_load

    #!/bin/sh
    module="test_drv"
    device="test_dev"
    mode="664"
    group="david"
    # remove stale nodes
    rm -f /dev/${device} 
    # invoke insmod with all arguments we got
    # and use a pathname, as newer modutils don't look in . by default
    /sbin/insmod -f ./$module.ko $* || exit 1
    major=`cat /proc/devices | awk "\\$2==\"$device\" {print \\$1}"`
    mknod /dev/${device} c $major 0
    # give appropriate group/permissions
    chgrp $group /dev/${device}
    chmod $mode  /dev/${device}
  

• test_drv_unload

    #!/bin/sh
    module="test_drv"
    device="test_dev"
  
    #invoke rmmod with all arguments we got
    /sbin/rmmod $module $* || exit 1
    # remove nodes
    rm -f /dev/${device}
    exit 0
  

利用Makefile编译test_drv.c

• 编译：make clean；make
  

加载模块

• 先给脚本文件增加可执行权限：chmod +x ./test_drv_load
• 再以管理员身份运行脚本：sudo ./test_drv_load
• 加载成功
  

编译运行test.c

• 编译：gcc -o test.c test
• 运行：./test
• 根据提示输入信息
  

卸载模块

• 先给脚本文件增加可执行权限：chmod +x ./test_drv_unload
• 再以管理员身份运行卸载脚本：sudo ./test_drv_unload

实验中的问题

• 运行脚本时"open:Permisson denied"
• 解决：chmod +x ...(脚本名称)