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分类: LINUX

2011-05-11 18:03:26

linux内核定时器的用法(含有例子)
creator
sz111@126.com

今天参考linux驱动开发详解,照抄了一份second的程序,用到了timer。

总的来说,timer的用法还是很简单的。主要需要定义一个timer_list变量timer、
先初始化timer
init_timer(&timer);
then 对timer的相关参数赋值:
timer.function = fun;
timer.expires = jiffies + TIMER_DELAY;

add_timer(&timer);
在定时器时间到的时候,会执行fun,如果继续定时,可以通过
在fun中执行 
mod_timer(&timer, jiffies + TIMER_DELAY);

在不需要的时候通过调用
del_timer(&timer);
删除定时器。

简单吧。这样一个简单的定时器就完成了。
呵呵。

附程序:
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include

#define SECOND_MAJOR 0

static int second_major = SECOND_MAJOR;

struct second_dev
{
    struct cdev cdev;
    atomic_t counter;
    struct timer_list s_timer;
};

struct second_dev *second_devp;

static void second_timer_handle(unsigned long arg)
{
    mod_timer(&second_devp->s_timer, jiffies + HZ);
    atomic_inc(&second_devp->counter);
    
    printk(KERN_ERR "current jiffies is %ld\n",jiffies);
}

int second_open(struct inode *inode, struct file *filp)
{
  init_timer(&second_devp->s_timer);
  second_devp->s_timer.function = &second_timer_handle;
  second_devp->s_timer.expires = jiffies + HZ;
  
  add_timer(&second_devp->s_timer);
  atomic_set(&second_devp->counter, 0);
  return 0;    
}

int second_release(struct inode *inode, struct file *filp)
{
    del_timer(&second_devp->s_timer);
    
    return 0;
}
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);
    }
    
}

static const struct file_operations second_fops =
{
    .owner = THIS_MODULE,
    .open = second_open,
    .release = second_release,
    .read = second_read,
};
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;
    dev->cdev.ops = &second_fops;
    err = cdev_add(&dev->cdev, devno, 1);
    if (err)
    {
        printk(KERN_NOTICE "Error %d add second%d", err, index);
    }
}
int second_init(void)
{
    int ret;
    dev_t devno = MKDEV(second_major, 0);
    
    if (second_major)
    {
        ret = register_chrdev_region(devno, 1, "second");
    }else
    {
        ret = alloc_chrdev_region(&devno, 0, 1, "second");
        second_major = MAJOR(devno);
    }
    if (ret < 0)
    {
        return ret;
    }
    
    second_devp = kmalloc(sizeof(struct second_dev), GFP_KERNEL);
    if (!second_devp)
    {
        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);
}

void second_exit(void)
{
    cdev_del(&second_devp->cdev);
    kfree(second_devp);
    unregister_chrdev_region(MKDEV(second_major, 0), 1);
}

MODULE_AUTHOR("Song Baohua");
MODULE_LICENSE("Dual BSD/GPL");

module_param(second_major, int, S_IRUGO);

module_init(second_init);
module_exit(second_exit);

附上用户端的测试程序:
#include
#include
#include

int main(void)
{
    int fd, i;
    int data;
    fd = open("/dev/second",O_RDONLY);
    if (fd < 0)
    {
        printf("open /dev/second error\n");
    }
    for(i = 0; i < 20; i++)
    {
      read(fd, &data, sizeof(data));
      printf("read /dev/second is %d\n",data);
      sleep(1);
       }
    close(fd);
}
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