2019-2020 20175207- 20175235 实验四 外设驱动程序设计

20175207-20175235 实验四 外设驱动程序设计

20175207冷南
20175235泽仁拉措

目录:

外设驱动程序设计-1

外设驱动程序设计-2

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）

  

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）

• 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
");
}

• 命令行：

  • 在虚拟设备驱动源码目录下编译并加载驱动模块make clean;make;./test_drv_load
  • 编译并运行测试程序gcc –o test test.c;./test
  • 卸载驱动程序./test_drv_unload

• 测试结果
  

• 安装驱动后
  

• 卸载后
  

• 遇到的问题：

• 使用make命令编译代码时报错Makefile ...（行号） ... 遗漏分隔符...停止
  解决方法：命令行前缺少Tab
  反斜线后多了空格
  配置文件vimrc中有set expandtab（使用空格代替制表符）
  参考链接：makefile报错