五 定時器例程

#include <linux/module.h>
#include <linux/types.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/cdev.h>
#include <asm/io.h>

#include <linux/version.h>
#if LINUX_VERSION_CODE > KERNEL_VERSION(3, 3, 0)
	#include <asm/switch_to.h>
#else
	#include <asm/system.h>	//在2.6.x的核心版本中，檔案操作結構體中，才會有ioctl的欄位，高版本中使用unlocked_ioctl，
#endif

#include <asm/uaccess.h>
#include <linux/slab.h>

#define SECOND_MAJOR 248 /*預設的 second 的主裝置號*/

static int second_major = SECOND_MAJOR;

/*second 裝置結構體*/
struct second_dev {
   struct cdev cdev; /*cdev 結構體*/
   atomic_t counter; /* 一共經歷了多少秒?*/
   struct timer_list s_timer;  /*裝置要使用的定時器*/
};

struct second_dev *second_devp;

/*定時器處理函式*/
static void second_timer_handle (unsigned long arg)
{
   //修改定時的expire，重新設定定時時間
   mod_timer (&second_devp->s_timer, jiffies + HZ);

   //原子計數，對當前記錄時間更新
   atomic_inc (&second_devp->counter);
   printk(KERN_NOTICE "current jiffies is %lld\n", jiffies);
}

/*檔案開啟函式*/
int second_open (struct inode *inode, struct file *filp)
{
   /*初始化定時器*/
   init_timer (&second_devp->s_timer);
   second_devp->s_timer.function = &second_timer_handle; //當定時器達到時，執行定時處理函式。
   second_devp->s_timer.expires = jiffies + HZ; //定時時間，jiffies + HZ(HZ預設值為1000)
   add_timer (&second_devp->s_timer);/*新增(註冊)定時器*/
   atomic_set (&second_devp->counter, 0); //計數清零

   return 0;
}

/*檔案釋放函式*/
int second_release (struct inode *inode, struct file *filp)
{
   //刪除一個定時器
   del_timer (&second_devp->s_timer);
   return 0;
}

/*Second 讀函式*/
static ssize_t second_read (struct file *filp, char __user *buf, size_t count, loff_t *ppos)
{
   int counter;
   counter = atomic_read (&second_devp->counter);
   if (put_user (counter, (int *)buf))
      return -EFAULT;
   else
      return sizeof (unsigned int);
}

/*檔案操作結構體*/
static const struct file_operations second_fops = {
   .owner = THIS_MODULE,
   .open = second_open,
   .release = second_release,
   .read = second_read,
};

/*初始化並註冊 cdev*/
static void second_setup_cdev (struct second_dev *dev, int index)
{
   int err, devno = MKDEV (second_major, index);
   cdev_init (&dev->cdev, &second_fops);
   dev->cdev.owner = THIS_MODULE;
   err = cdev_add (&dev->cdev, devno, 1);
   if (err)
      printk (KERN_NOTICE "Error %d adding CDEV %d", err, index);
}

/*裝置驅動模組載入函式*/
int second_init (void)
{
   int ret;
   dev_t devno = MKDEV (second_major, 0);

   /* 申請裝置號*/
   if (second_major)
      ret = register_chrdev_region (devno, 1, "second");
   else {
      /* 動態申請裝置號 */
      return alloc_chrdev_region (&devno, 0, 1, "second");
      second_major = MAJOR (devno);
   }
   if (ret < 0)
      return ret;

   /* 動態申請裝置結構體的記憶體*/
   second_devp = kmalloc (sizeof (struct second_dev), GFP_KERNEL);
   if (!second_devp) { /*申請失敗*/
      ret = -ENOMEM;
      goto fail_malloc;
   }
   memset (second_devp, 0, sizeof (struct second_dev));
   second_setup_cdev (second_devp, 0);

   return 0;
   fail_malloc:
   unregister_chrdev_region (devno, 1);
   return ret;
}

/*模組解除安裝函式*/
void second_exit (void)
{
   cdev_del (&second_devp->cdev); /*登出 cdev*/
   kfree (second_devp);  /*釋放裝置結構體記憶體*/
   unregister_chrdev_region (MKDEV (second_major, 0), 1); /* 釋放裝置號 */
}

MODULE_AUTHOR ("zhongming");
MODULE_LICENSE ("Dual BSD/GPL");
module_param (second_major, int, S_IRUGO);
module_init (second_init);
module_exit (second_exit);

 

Makefile檔案

obj-m := Second.o

KERNEL_VERSION ?= $(shell uname -r)
PWD := $(shell pwd)

all:
	make -C /lib/modules/$(KERNEL_VERSION)/build M=$(PWD) modules  
clean:
	make -C /lib/modules/$(KERNEL_VERSION)/build M=$(PWD) clean  

測試程式碼

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>

int main (void)
{
   int fd;
   int counter = 0;
   int old_counter = 0;
   fd = open ("/dev/Second", O_RDONLY);
   if (fd != -1) {
      while (1) {
         read (fd, &counter, sizeof (unsigned int));
         if (counter != old_counter) {
            printf ("seconds after open /dev/second: %d\n", counter);
            old_counter = counter;
         }
      }
   } else {
      printf ("Device open failure\n");
   }
   return 0;
}