linux驱动之内核定时器驱动设计

mod_timer(&second_devp->

atomic_inc(&second_devp->

init_timer(&second_devp->

second_devp->

second_devp->

add_timer(&second_devp->

atomic_set(&second_devp->

就关闭设备，直接删除定时器*/

del_timer(&second_devp->s_timer);

return 0;

}

/*read函数的实现*/

static ssize_t second_read(struct file *filp,char __user *buf,size_t count,loff_t *ppos)

{

int counter;

/*读当前的值*/

counter = atomic_read(&second_devp->counter);

/*

采用put_user实现数值的传送

put_user函数存在对指针变量的检查，

因此不需要检测指针是否正确

*/

if(put_user(counter,(int *)buf))

return -EFAULT;

else

/*返回数据大小*/

return sizeof(unsigned int);

}

/*具体的文件操作集合*/

static const struct file_operations second_fops =

{

/*这是拥有者*/

.owner = THIS_MODULE,

.open = second_open,

.release = second_release,

.read = second_read,

};

/*初始化函数*/

static int __init second_init(void)

{

int ret;

/*设备号的申请，创建*/

dev_t devno = MKDEV(second_major,0);

/*静态申请设备号*/

if(second_major)

{

ret = register_chrdev_region(devno,1,"second");

}

/*动态申请设备号*/

else

{

ret = alloc_chrdev_region(&devno,0,1,"second");

second_major = MAJOR(devno);

}

if(ret < 0)

{

return ret;

}

/*分配设备结构体的地址空间*/

second_devp = kmalloc(sizeof(struct second_dev),GFP_KERNEL);

/*检查是否分配正确*/

if(!second_devp)

{

ret = -ENOMEM;

goto fail_malloc;

}

/*清零分配的空间*/

memset(second_devp,0,sizeof(struct second_dev));

/*创建设备类，用于自动创建设备文件*/

second_devp->myclass = class_create(THIS_MODULE,"second_timer_class");

/*字符设备初始化，绑定相关操作到设备*/

cdev_init(&second_devp->cdev,&second_fops);

/*设备的拥有者*/

second_devp->cdev.owner = THIS_MODULE,

/*添加设备到内核*/

ret = cdev_add(&second_devp->cdev,devno,1);

/*错误处理*/

if(ret)

{

printk(KERN_NOTICE "ERROR %d",ret);

goto fail_malloc;

}

/*依据以前创建的设备类，创建设备*/

device_create(second_devp->myclass,NULL,devno,NULL,"second%d",0);

return 0;

/*错误操作*/

fail_malloc:

unregister_chrdev_region(devno,1);

return ret;

}

/*退出函数*/

static void __exit second_exit(void)

{

/*释放设备*/

device_destroy(second_devp->myclass,MKDEV(second_major,0));

/*删除字符设备*/

cdev_del(&second_devp->cdev);

/*释放设备类*/

class_destroy(second_devp->myclass);

/*释放分配的内存空间大小*/

kfree(second_devp);

/*释放设备号*/

unregister_chrdev_region(MKDEV(second_major,0),1);

}

/*卸载和加载*/

module_init(second_init);

module_exit(second_exit);

/*LICENSE和作者信息*/

MODULE_LICENSE("GPL");

MODULE_AUTHOR("GP-");

应用程序：

#include

#include

#include

#include

#include

#include

#include

int main()

{

int fd;

int counter = 0;

int old_counter = 0;

fd = open("/dev/second0",O_RDONLY);

if(fd != -1)

{

while(1)

{

read(fd,&counter,sizeof(unsigned int));

if(counter != old_counter)

{

printf("second after open /dev/second0 : %d",counter);

old_counter = counter;

}

}

}

else

{

printf("Device open failure");

exit(1);

}

exit(0);

}

实验效果：

[root@EmbedSky Test]# ./app-timer

Current jiffies is 2137721

second after open /dev/second0 : 1

Current jiffies is 2137921

second after open /dev/second0 : 2

Current jiffies is 2138121

second after open /dev/second0 : 3

Current jiffies is 2138321

second after open /dev/second0 : 4

Current ji