idle thread

.. code-block:: c

#if !CH_NO_IDLE_THREAD || defined(__DOXYGEN__)
/**
* @brief   Idle thread working area.
*/
WORKING_AREA(_idle_thread_wa, PORT_IDLE_THREAD_STACK_SIZE);

/**
* @brief   This function implements the idle thread infinite loop.
* @details The function puts the processor in the lowest power mode capable
*          to serve interrupts.<br>
*          The priority is internally set to the minimum system value so
*          that this thread is executed only if there are no other ready
*          threads in the system.
*
* @param[in] p the thread parameter, unused in this scenario
*/
void _idle_thread(void *p) {
  (void)p;
  chRegSetThreadName("idle");
  while (TRUE) {
    port_wait_for_interrupt(); //空函式
    IDLE_LOOP_HOOK();
  }
}

.. code-block:: c

#if !CH_NO_IDLE_THREAD
/* This thread has the lowest priority in the system, its role is just to
 serve interrupts in its context while keeping the lowest energy saving
 mode compatible with the system status.*/
    chThdCreateStatic(_idle_thread_wa, sizeof(_idle_thread_wa), IDLEPRIO,
                      (tfunc_t)_idle_thread, NULL);
#endif