linux驅(qū)動之內(nèi)核定時器驅(qū)動設(shè)計

作者：時間：2016-12-01 來源：網(wǎng)絡(luò)

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驅(qū)動程序：

#include

/*采用宏定義設(shè)置設(shè)備的主設(shè)備號*/

#define SECOND_MAJOR 0

/*靜態(tài)的分別保存靜態(tài)主設(shè)備號的變量*/

static int second_major = SECOND_MAJOR;

/*設(shè)備結(jié)構(gòu)體，通常在設(shè)備中包含需要的設(shè)備，比如字符、塊等類型*/

struct second_dev{

/*添加設(shè)備類型，

我認(rèn)為可以采用一個聯(lián)合體，

包含塊設(shè)備或者字符設(shè)備,類似inode的實(shí)現(xiàn)方法，

這樣可以提高結(jié)構(gòu)體的通用性

struct cdev cdev;

/*原子變量，用來統(tǒng)計*/

atomic_t counter;

/*添加內(nèi)核定時器結(jié)構(gòu)體變量*/

struct timer_list s_timer;

/*用于動態(tài)創(chuàng)建設(shè)備文件的設(shè)備類*/

struct class *myclass;

};

/*結(jié)構(gòu)體指針或者采用全局變量直接定義結(jié)構(gòu)都可以*/

struct second_dev *second_devp;

/*如果定時時間到了，定時器的處理函數(shù)*/

static void second_timer_handler(unsigned long arg)

{

修改定時器中的到期時間，增加時間為1s，

需要注意的是mod_timer函數(shù)是重新注冊定時器到內(nèi)核

而不管定時器是否被運(yùn)行過

mod_timer(&second_devp->s_timer,jiffies + HZ);

/*原子變量的增加*/

atomic_inc(&second_devp->counter);

/*輸出jiffies值*/

printk(KERN_NOTICE "Current jiffies is %d",jiffies);

}

/*open函數(shù)實(shí)現(xiàn)*/

static int second_open(struct inode *inode,struct file *filp)

{

/*初始化定義的內(nèi)核定時器*/

init_timer(&second_devp->s_timer);

/*指定內(nèi)核定時器的處理函數(shù)是上面定義好的函數(shù)*/

second_devp->s_timer.function = second_timer_handler;

/*指定定時間隔是1s*/

second_devp->s_timer.expires = jiffies + HZ;

/*將定時器添加到內(nèi)核*/

add_timer(&second_devp->s_timer);

/*同時設(shè)備相關(guān)的統(tǒng)計值為0*/

atomic_set(&second_devp->counter,0);

return 0;

}

/*release函數(shù)的實(shí)現(xiàn)*/

static int second_release(struct inode *inode,struct file *filp)

{

/*如果沒有到時間就關(guān)閉設(shè)備，直接刪除定時器*/

del_timer(&second_devp->s_timer);

return 0;

}

/*read函數(shù)的實(shí)現(xiàn)*/

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

{

int counter;

/*讀當(dāng)前的值*/

counter = atomic_read(&second_devp->counter);

采用put_user實(shí)現(xiàn)數(shù)值的傳送

put_user函數(shù)存在對指針變量的檢查，

因此不需要檢測指針是否正確

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

return -EFAULT;

else

/*返回數(shù)據(jù)大小*/

return sizeof(unsigned int);

}

/*具體的文件操作集合*/

static const struct file_operations second_fops =

{

/*這是擁有者*/

.owner = THIS_MODULE,

.open = second_open,

.release = second_release,

.read = second_read,

};

/*初始化函數(shù)*/

static int __init second_init(void)

{

int ret;

/*設(shè)備號的申請，創(chuàng)建*/

dev_t devno = MKDEV(second_major,0);

/*靜態(tài)申請設(shè)備號*/

if(second_major)

{

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

}

/*動態(tài)申請設(shè)備號*/

else

{

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

second_major = MAJOR(devno);

}

if(ret < 0)

{

return ret;

}

/*分配設(shè)備結(jié)構(gòu)體的地址空間*/

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

/*檢查是否分配正確*/

if(!second_devp)

{

ret = -ENOMEM;

goto fail_malloc;

}

/*清零分配的空間*/

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

/*創(chuàng)建設(shè)備類，用于自動創(chuàng)建設(shè)備文件*/

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

/*字符設(shè)備初始化，綁定相關(guān)操作到設(shè)備*/

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

/*設(shè)備的擁有者*/

second_devp->cdev.owner = THIS_MODULE,

/*添加設(shè)備到內(nèi)核*/

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

/*錯誤處理*/

if(ret)

{

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

goto fail_malloc;

}

/*依據(jù)以前創(chuàng)建的設(shè)備類，創(chuàng)建設(shè)備*/

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

return 0;

/*錯誤操作*/

fail_malloc:

unregister_chrdev_region(devno,1);

return ret;

}

/*退出函數(shù)*/

static void __exit second_exit(void)

{

/*釋放設(shè)備*/

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

/*刪除字符設(shè)備*/

cdev_del(&second_devp->cdev);

/*釋放設(shè)備類*/

class_destroy(second_devp->myclass);

/*釋放分配的內(nèi)存空間大小*/

kfree(second_devp);

/*釋放設(shè)備號*/

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

}

/*卸載和加載*/

module_init(second_init);

module_exit(second_exit);

/*LICENSE和作者信息*/

MODULE_LICENSE("GPL");

MODULE_AUTHOR("GP-");

應(yīng)用程序：

#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);

}

實(shí)驗(yàn)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 jiffies is 2138521

second after open /dev/second0 : 5

Current jiffies is 2138721

second after open /dev/second0 : 6

以上的結(jié)果表明內(nèi)核定時器基本實(shí)現(xiàn)了效果，但從實(shí)驗(yàn)結(jié)果看好像為每兩秒實(shí)現(xiàn)一次顯示。具體的原因還有待于再次分析，因?yàn)閍rm中的HZ應(yīng)該為100，而不是200。

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