2017-2018-1 20155219 实验四 外设驱动程序设计

任务一

实验要求

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

2）提交康奈尔笔记的照片

完成情况:

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）

实验目的

该实验是编写最简单的字符驱动程序，这里的设备也就是一段内存，实现简单的读写功能，并列出常用格式的Makefile以及驱动的加载和卸载脚本。读者可以熟悉字符设备驱动的整个编写流程

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。

完成情况

1.编写驱动程序源代码

/* 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");
}

2.编译代码

KERNELDIR=/usr/src/4.4.0-101-generic

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

3.加载模块

/*test_drv_load*/
#!/bin/sh
# 驱动模块名称
module="test_drv"    
# 设备名称。在/proc/devices中出现
device="test_dev"    
# 设备文件的属性
mode="664"            
group="david"        
 
# 删除已存在的设备节点
rm -f /dev/${device} 
# 加载驱动模块
/sbin/insmod -f ./$module.ko $* || exit 1
# 查到创建设备的主设备号
major=`cat /proc/devices | awk "\\$2==\"$device\" {print \\$1}"

mknod /dev/${device} c $major 0
chgrp $group /dev/${device}
chmod $mode  /dev/${device}

4.test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);
}