• 高通 sensor 从native到HAL
• 高通HAL层之Sensor HAL
• 高通HAL层之bmp18x.cpp

问题现象：

当休眠后，再次打开preesure sensor的时候，会出现隔一段时候后，APK才会出现数据；（数据有时候会很难出现）

问题分析：

从上面几节中，我们可以知道，framework到HAL是通过调用sensors.msm8909.so调用到函数PressureSensor::readEvents中取出的；

int PressureSensor::readEvents(sensors_event_t* data, int count)
{
    int i = 0;
    if (count < 1)
        return -EINVAL;

    if (mHasPendingEvent) {
        mHasPendingEvent = false;
        mPendingEvent.timestamp = getTimestamp();
        *data = mPendingEvent;
        return mEnabled ? 1 : 0;
    }

    if (mHasPendingMetadata) {  
        mHasPendingMetadata--;
        meta_data.timestamp = getTimestamp();
        *data = meta_data;
        return mEnabled ? 1 : 0;
    }

    ssize_t n = mInputReader.fill(data_fd);
    if (n < 0)
        return n;

    int numEventReceived = 0;
    input_event const* event;

#if FETCH_FULL_EVENT_BEFORE_RETURN
again:
#endif
    while (count && mInputReader.readEvent(&event)) {
        int type = event->type;
        if (type == EV_ABS) {
            float value = event->value;
            mPendingEvent.pressure = value * CONVERT_PRESSURE;
            ALOGI("the pressure is %f\n", mPendingEvent.pressure);
        } else if (type == EV_SYN) {
            switch (event->code) {
                case SYN_TIME_SEC:
                    mUseAbsTimeStamp = true;
                    report_time = event->value*1000000000LL;
                    break;
                case SYN_TIME_NSEC:
                    mUseAbsTimeStamp = true;
                    mPendingEvent.timestamp = report_time+event->value;
                    break;
                case SYN_REPORT:
                    if(mUseAbsTimeStamp != true) {
                        mPendingEvent.timestamp = timeva lToNano(event->time);
                    }
                    if (mEnabled) {
//                      ALOGI("timestamp = %ld mEnabledTime = %ld mUseAbsTimeStamp = %d enable here\n", mPendingEvent.timestamp, mEnabledTime, mUseAbsTimeStamp);
//                      if (mPendingEvent.timestamp >= mEnabledTime)
                        {
                            *data = mPendingEvent;
                            ALOGI("data pressure is %f\n", data->pressure);
//                          data++;
                            numEventReceived++;
                        }
                        count--;
                    }
                    break;
            }
        } else {
            ALOGE("PressureSensor: unknown event (type=%d, code=%d)",
                    type, event->code);
        }
        
        mInputReader.next();
    }

#if FETCH_FULL_EVENT_BEFORE_RETURN
    /* if we didn't read a complete event, see if we can fill and
       try again instead of returning with nothing and redoing poll. */
    if (numEventReceived == 0 && mEnabled == 1) {
        n = mInputReader.fill(data_fd);
        if (n)
            goto again;
    }
#endif
    ALOGI("end the data the pressure is %f\n", mPendingEvent.pressure);

    return numEventReceived;
}

增加if (mPendingEvent.timestamp >= mEnabledTime)判断是为了判断SYN_REPORT不延迟的情况；

mPendingEvent.timestamp在这里被赋值：

input_event const* event;

//这个可以一直进来
if(mUseAbsTimeStamp != true) {
  mPendingEvent.timestamp = timeva lToNano(event->time);
}

event->time代表了按键时间；可以用struct timeva l获取系统时间。
其中input_event和timeva l结构体如下：

struct input_event {

struct timeva l time; //按键时间

__u16 type; //类型，在下面有定义

__u16 code; //要模拟成什么按键

__s32 value;//是按下还是释放

};

struct timeva l {
   __kernel_time_t        tv_sec;     /* seconds */
  __kernel_suseconds_t    tv_usec;    /* microseconds */
};

//将时间转换为ns
static int64_t timeva lToNano(timeva l const& t) {
      return t.tv_sec*1000000000LL + t.tv_usec*1000;
}

通过打印可以知道问题出现的时候mPendingEvent.timestamp是小于mEnabledTime的，进不了判断，所以上层也就无法获取相应的数据；

mEnabledTime是在int PressureSensor::enable(int32_t, int en)函数中实现：

....
    mEnabledTime = getTimestamp() + IGNORE_EVENT_TIME;
....

int64_t SensorBase::getTimestamp() {
    struct timespec t;
    t.tv_sec = t.tv_nsec = 0;
    clock_gettime(CLOCK_BO