2019-2020-1 20175210 20175211 20175219 实验四 外设驱动程序设计

2019-2020-1 20175210 20175211 20175219 实验四 外设驱动程序设计

实验内容

(1)学习资源

• 实验要求
  • 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）
    
    
    
    

(2)test实验

• 实验要求

  • 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

  • 将下列实验代码保存进目标文件夹

  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
  ");
  }
  

  • make clean;make

  • 给脚本增加执行权限
    chmod 777 test_drv_load
chmod 777 test_drv_unload

  • 管理员权限运行脚本

  • 查看驱动程序编号cat /proc/devices
    

  • 编译运行测试程序
    

  • 卸载驱动程序
    

实验中遇到的问题

运行时报错找不到文件

一直没有解决，后来跟着同学将代码中文件路径改成/dev/stdout可以成功运行，但是没有根本上解决。