10.5核心定時器
10.5.1核心定時器程式設計


1.timer_list
struct timer_list my_timer;


2.初始化定時器
void init_timer(struct timer_list *timer);


3.增加定時器
void add_timer(struct timer_list *timer);


4.刪除定時器
int del_timer(struct timer_list *timer);


5.修改定時器的expire
int mod_timer(struct timer_list *timer, unsigned long expires);


10.10 核心定時器使用模板
//xxx裝置結構體
struct xxx_dev
{
struct cdev cdev;
.....
timer_list xxx_timer;//裝置要使用的定時器
};
//xxx驅動中的某函式
xxx_funcl(...)
{
struct xxx_dev *dev = filp->private_data;
...
//初始化定時器
init_timer(&dev->xxx_timer);
dev->xxx_timer.function = &xxx_do_timer;
dev->xxx_timer.data = (unsigned long)dev;
//裝置結構體指標作為定時器處理函式引數
dev->xxx_timer.expires = jiffies + delay;
//新增(註冊)定時器
add_timer(&dev->xxx_timer);
}


//xxx驅動中的某函式
xxx_func2(...)
{
....
//刪除定時器
del_timer(&dev->xxx_timer);
....
}


//定時器處理函式
static void xxx_do_timer(unsigned long arg)
{
struct xxx_device *dev = (struct xxx_device *)(arg);
...
//排程定時器再執行
dev->xxx_timer.expires = jiffies + delay;
add_timer(&dev->xxx_timer);
...
}




hrtimer(high resolution timer)表示高精度定時器:
==============================================================================
API
ktime_t ktime_add_ns(const ktime_t kt, u64 nsec)
ktime_t ktime_sub_ns(const ktime_t kt, u64 nsec)
ktime_t ktime_add_safe(const ktime_t lhs, const ktime_t rhs)
void hrtimer_init_on_stack(struct hrtimer *timer, clockid_t clock_id,
  enum hrtimer_mode mode)
  
u64 hrtimer_forward(struct hrtimer *timer, ktime_t now, ktime_t interval)  
int hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
unsigned long delta_ns, const enum hrtimer_mode mode)


int
hrtimer_start(struct hrtimer *timer, ktime_t tim, const enum hrtimer_mode mode)
int hrtimer_try_to_cancel(struct hrtimer *timer)
int hrtimer_cancel(struct hrtimer *timer)
ktime_t hrtimer_get_remaining(const struct hrtimer *timer)
void hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
 enum hrtimer_mode mode)
int hrtimer_get_res(const clockid_t which_clock, struct timespec *tp)
int __sched schedule_hrtimeout(ktime_t *expires,
      const enum hrtimer_mode mode)






/*
 * Mode arguments of xxx_hrtimer functions:
 */
enum hrtimer_mode {
HRTIMER_MODE_ABS = 0x0,/* Time value is absolute */
HRTIMER_MODE_REL = 0x1,/* Time value is relative to now */
HRTIMER_MODE_PINNED = 0x02,/* Timer is bound to CPU */
HRTIMER_MODE_ABS_PINNED = 0x02,
HRTIMER_MODE_REL_PINNED = 0x03,
};




/*
 * Return values for the callback function
 */
enum hrtimer_restart {
HRTIMER_NORESTART,/* Timer is not restarted */
HRTIMER_RESTART,/* Timer must be restarted */
};      
       
#define HRTIMER_STATE_INACTIVE0x00
#define HRTIMER_STATE_ENQUEUED0x01
#define HRTIMER_STATE_CALLBACK0x02
#define HRTIMER_STATE_MIGRATE0x04


/* Parameters used to convert the timespec values: */
#define MSEC_PER_SEC1000L
#define USEC_PER_MSEC1000L
#define NSEC_PER_USEC1000L
#define NSEC_PER_MSEC1000000L
#define USEC_PER_SEC1000000L
#define NSEC_PER_SEC1000000000L
#define FSEC_PER_SEC1000000000000000LL

hrtimer用法：


struct hrtimer acc_timer; //定義hrtimer
ktime_t acc_poll_delay; //定義ktimer_t 型別 時間變數。


//hrtimer 呼叫函式
static enum hrtimer_restart stk_acc_timer_func(struct hrtimer *timer)
{
struct stk831x_data *stk = container_of(timer, struct stk831x_data, acc_timer);
queue_work(stk->stk_acc_wq, &stk->stk_acc_work);
hrtimer_forward_now(&acc_timer, acc_poll_delay); //
//hrtimer_forward_now(&gw_hrtimer,ktime_set(0, 62500));//直接設定為62500ns
return HRTIMER_RESTART;
}


int __init xxx_init(void)
{
....
hrtimer_init(&acc_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
acc_poll_delay = ns_to_ktime(2500 * USEC_PER_MSEC);
acc_timer.function = stk_acc_timer_func;
......
}


//啟動
int xxx_probe(void)
{
hrtimer_start(&stk->acc_timer, stk->acc_poll_delay, HRTIMER_MODE_REL);
}


void xxx_suspend(void)
{
hrtimer_cancel(&acc_timer);
}


void __exit xxx_exit(void)
{
hrtimer_try_to_cancel(&acc_timer);
}