dev.c 代碼
#ifndef __KERNEL__
#define __KERNEL__
#endif
#ifndef MODULE
#define MODULE
#endif
//#include <linux/config.h>
#include <linux/proc_fs.h>
#include <linux/moduleparam.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/seq_file.h>
#include <linux/ioctl.h>
#include <linux/fcntl.h>
#include <linux/poll.h>
#include <asm/uaccess.h>
#include <asm/system.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <asm/uaccess.h>
#include <linux/kernel.h>
#include <linux/slab.h>

MODULE_LICENSE("GPL");
// 常量定義
#define BUFFERLENS 1024*1024;
// 函數申明
ssize_t chuan_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos);
ssize_t chuan_write(struct file *filp, const char __user *buf, size_t count, loff_t *f_pos);
int chuan_open(struct inode *inode, struct file *filp);
int chuan_release(struct inode *inode, struct file *filp);

// 初始化字符設備驅動的file_operations結構體
// 很奇怪的語法……
struct file_operations chuan_fops = {
  .owner =    THIS_MODULE,
  .read =     chuan_read,
  .write =    chuan_write,
  .open =     chuan_open,
  .release =  chuan_release,
};

// 主力結構————表示設備結構
struct chuan_dev {
  char * rer;
  unsigned int buffersize;// 緩沖區大小
  unsigned int len;// 緩沖區已有長度
  unsigned int start;// 起始數據偏移量
  struct semaphore sem;// 信號量,用于互斥訪問
  struct cdev cdev;// 字符型設備結構
};


// 全局變量
struct chuan_dev chuan_device;
dev_t dev_no = 0;


// 初始化
int chuan_init(void)
{ 
  int err=0;
  // 初始化cdev
  cdev_init(&chuan_device.cdev, &chuan_fops);
  chuan_device.cdev.owner = THIS_MODULE;
  chuan_device.cdev.ops = &chuan_fops;
  // 動態分配一個設備號
  alloc_chrdev_region(&dev_no, 0, 1, "Rer'sPersonalDevices v1.11");
  // 字符設備注冊
  err = cdev_add(&chuan_device.cdev, dev_no, 1);
  if (err){
    printk(KERN_NOTICE "Error %d adding device\n", err);
    return -1;
  }
  else{
    // 初始化互斥信號量
    init_MUTEX(&chuan_device.sem);
    //printk("互斥信號量初始化成功\n");

    printk(KERN_NOTICE "Device Initilize success.\n");
    return 0; /* succeed */
  }
}

// 注銷
void chuan_exit(void)
{
  unregister_chrdev_region(dev_no, 1);
  cdev_del(&chuan_device.cdev);
}

// 打開
int chuan_open(struct inode *inode, struct file *filp)
{
  struct chuan_dev *mydev;
  // 高級技巧，,我不是很明白
  mydev = container_of(inode->i_cdev,struct chuan_dev,cdev);
  // 將private_data保存chuan_dev指針
  filp->private_data = mydev;

  // 信號量,如果已經無資源了，就不打開
  if (down_interruptible(&mydev->sem))
    return -ERESTARTSYS;
  up(&mydev->sem);

  if(!mydev->rer){
    // 如果緩沖區是空的,那么分配1k的內容給它
    //printk("緩沖區還是空的.\n");
    mydev->rer = (char *)kmalloc(1024, GFP_KERNEL);
    memset(mydev->rer, 0, 1024);
    // 初始化參數
    mydev->buffersize = 1024;
    mydev->len = mydev->start = 0;
  }
  else{
    //printk("緩沖區已經有東西了.現將其初始化\n");
  }
  return 0;
}
// 關閉
int chuan_release(struct inode *inode, struct file *filp)
{
  return 0;
}

// 讀取
ssize_t chuan_read(struct file *filp, char __user *buf, size_t count,
                   loff_t *f_pos)
{  
  //  int i;
  struct chuan_dev *mydev; 
  //printk("讀取\n");
  // 讀取數據  
  mydev = filp->private_data;

  // 信號量,如果已經無資源了，就不打開
  if (down_interruptible(&mydev->sem))
    return -ERESTARTSYS;
  /*  printk("緩沖區數據量長度: %d\n",mydev->len);
      printk("緩沖區起始位置: %d\n",mydev->start);  
      for(i=0;i<mydev->len+mydev->start;++i)
      printk("緩沖區: %d values %c\n",i,*(mydev->rer+i));
  */
  if(mydev->len>0){
    if(count > mydev->len-mydev->start)
      count = mydev->len-mydev->start;
    if(copy_to_user(buf,mydev->rer+mydev->start,count)){
      printk("拷貝失敗.\n");
    }
    else{
      mydev->start += count;
      if(mydev->start>=mydev->buffersize){
    mydev->start = 0;
    mydev->len = 0;
      }
      printk("拷貝成功.\n");
      printk("start =  %d\n",mydev->start);
      printk("len =  %d\n",mydev->len);
    }
  }
  else{
    printk("緩沖區還沒有東西，,無法進行讀取.\n");
    goto end;
  }
 end:
  // 將訪問信號釋放
  up(&mydev->sem);
  return 0;
}

// 寫入
ssize_t chuan_write(struct file *filp, const char __user *buf, size_t count,
                    loff_t *f_pos)
{  
  struct chuan_dev *mydev; 
  // 寫入數據  
  mydev = filp->private_data;

  // 信號量,如果已經無資源了，就不打開
  if (down_interruptible(&mydev->sem))
    return -ERESTARTSYS;

  if(!mydev->rer){
    //printk(KERN_NOTICE "寫入過程，《， 空的。.\n");
  }
  else{
    //printk(KERN_NOTICE "寫入過程， 已經有東西了。.\n");
    // 向緩沖區中寫數據
    if(mydev->start+mydev->len+count > mydev->buffersize){
      // 如果預感到要溢出,那么就從頭寫 并且舍棄已有數據(這樣很不好)
      memset(mydev->rer, 0, mydev->buffersize);
      if(count > mydev->buffersize)
    count = mydev->buffersize;
      mydev->start = mydev->len = 0;
    }
    if(copy_from_user(mydev->rer+mydev->len,buf,count)){
      printk(KERN_NOTICE "寫入失敗.\n");
    }
    else{
      mydev->len += count;
      printk(KERN_NOTICE "寫入成功,當前緩沖區的大小為: %d.\n",mydev->len);
    }
  }

  up(&mydev->sem);
  return 0;
}

module_init(chuan_init);
module_exit(chuan_exit);use.c 測試驅動代碼
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
main()
{
  int testdev;
  int i;
  char buf[10];
  char redbuf[10];
  // 先打開/dev/lala(從設備號為0),進行寫入操作
  testdev = open("/dev/lala",O_RDWR);
  if ( testdev == -1 ){
    printf("Cann't open file \n");
  }else{
    printf("Open file Success.\n");
    for(i=0;i<10;++i)
      buf[i] = i+'a';
    write(testdev,buf,10);
    write(testdev,buf,10);
    printf("寫入設備成功/dev/lala\n");

    memset(buf,0,10);
    read(testdev,redbuf,5);
    printf("讀取設備成功/dev/lala\n");
    for (i = 0; i < 5;i++)
      printf("收到數據: %c\n",redbuf[i]);
    printf("\n");
    memset(buf,0,10);
    read(testdev,redbuf,5);
    printf("讀取設備成功/dev/lala\n");
    for (i = 0; i < 5;i++)
      printf("收到數據: %c\n",redbuf[i]);
    printf("\n");
    close(testdev); 
  }
}
ac.sh 和 wa.sh，掛載和卸載驅動的shell
#!/bin/bash
insmod dev.ko
mknod /dev/lala c 253 0
chmod 777 /dev/lala
mknod /dev/lala2 c 253 1
chmod 777 /dev/lala2
#!/bin/bash
rm /dev/lala
rm /dev/lala2
rmmod dev