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2019-2020-1 20175205 20175234 20175217 实验四外设驱动程序设计

一、实验目的

编写最简单的字符驱动程序
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
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

二、实验内容及步骤

1、任务一

任务详情
- 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）
笔记

2、任务二

任务详情
- 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
- 在VMware虚拟机中创建文件夹
- 将第十一章中关于字符设备的test实验中代码：test_drv.c、test.c、Makefile、test_drv_load、test_drv_unload敲入并保存在文件夹内
- 要注意在Makefile中命令换行要用Tab键进行缩进
- 实验代码

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.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/stdout"
#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);
}

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;
/*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)) /* ?内核??的数????用户??*/
{
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
");
/* 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
");
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
", major);
return result;
}
test_setup_cdev(&test_dev, 0, &test_fops);
printk("The major of the test device is %d
", 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
");
}