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linux驅(qū)動(dòng)之內(nèi)核定時(shí)器驅(qū)動(dòng)設(shè)計(jì)

作者： 時(shí)間：2016-12-01 來源：網(wǎng)絡(luò) 收藏
驅(qū)動(dòng)程序：
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
/*采用宏定義設(shè)置設(shè)備的主設(shè)備號(hào)*/
#define SECOND_MAJOR 0
/*靜態(tài)的分別保存靜態(tài)主設(shè)備號(hào)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(gè)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(jì)*/
atomic_t counter;
/*添加內(nèi)核定時(shí)器結(jié)構(gòu)體變量*/
struct timer_list s_timer;
/*用于動(dòng)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(shí)時(shí)間到了，定時(shí)器的處理函數(shù)*/
static void second_timer_handler(unsigned long arg)
{
/*
修改定時(shí)器中的到期時(shí)間，增加時(shí)間為1s，
需要注意的是mod_timer函數(shù)是重新注冊定時(shí)器到內(nèi)核
而不管定時(shí)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(shí)器*/
init_timer(&second_devp->s_timer);
/*指定內(nèi)核定時(shí)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(shí)間隔是1s*/
second_devp->s_timer.expires = jiffies + HZ;
/*將定時(shí)器添加到內(nèi)核*/
add_timer(&second_devp->s_timer);
/*同時(shí)設(shè)備相關(guān)的統(tǒng)計(jì)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(shí)間就關(guān)閉設(shè)備，直接刪除定時(shí)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(duì)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?cái)?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(hào)的申請(qǐng)，創(chuàng)建*/
dev_t devno = MKDEV(second_major,0);
/*靜態(tài)申請(qǐng)?jiān)O(shè)備號(hào)*/
if(second_major)
{
ret = register_chrdev_region(devno,1,"second");
}
/*動(dòng)態(tài)申請(qǐng)?jiān)O(shè)備號(hào)*/
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(dòng)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(cuò)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(cuò)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(hào)*/
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
#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);
}
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(shí)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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