2019-2020 1 20175230 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

实验内容与要求

• 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
• 提交康奈尔笔记

实验结果

任务二

实验内容与要求

• 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）

实验步骤

• 1.写好代码并将代码test_drv.c、test.c、Makefile、test_drv_load、test_drv_unload保存在文件夹内
• 2.在虚拟设备驱动源码目录下编译并加载驱动模块
  make clean;make
  给脚本文件增加可执行权限：chmod +x ./test_drv_load
  以管理员身份运行加载脚本:sudo ./test_drv_load
• 3.编译并运行测试程序
  gcc –o test test.c
chmod +x ./test
sudo ./test
• 4.卸载驱动程序
  给脚本文件增加可执行权限：chmod +x ./test_drv_unload
  以管理员身份运行加载脚本：sudo ./test_drv_unload
• 5.通过dmesg命令查看内核打印的信息
• 6.实验代码
  test_drv.c

/* 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
");
    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
");
    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
", major);
        return result;
    }
    test_setup_cdev(&test_dev, 0, &test_fops);
    printk("The major of the test device is %d
", major);
    return 0;
}
void cleanup_module(void) 
{
    cdev_del(&test_dev);
    unregister_chrdev_region(MKDEV(major, 0), 1);
    printk("Test device uninstalled
");
}

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] = '';
        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
", buff);
        }
    } while(strncmp(buff, "quit", 4));
    close(fd);
    exit(0);
}

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
endif

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
sudo /sbin/rmmod $module $* || exit 1

# remove nodes
rm -f /dev/${device}

exit 0

实验结果

实验中遇到的问题

• 问题1:运行make clean;make时，显示如下
  
  问题1解决方法：在makefile中，在命令行之前加tab键
  

• 问题2：make时，出现如下错误
  

  解决方法：按照提示进行修改

• 问题3：运行load脚本提示无效的组
  解决方法:：在load脚本中的group="david"david不是当前虚拟机的组用户，可通过cat /etc/passwd查看所有的用户信息,cat /etc/group查看所有组信息`，然后将脚本中的组名改成系统中有的组名即可