BLE协议栈中OnBoard_KeyCallback函数

请问 OnBoard_KeyCallback函数中为什么要加入这段代码，起到什么作用啊？

 /* If any key is currently pressed down and interrupt
     is still enabled, disable interrupt and switch to polling */
  if( keys != 0 )
  {
    if( OnboardKeyIntEnable == HAL_KEY_INTERRUPT_ENABLE )
    {
      OnboardKeyIntEnable = HAL_KEY_INTERRUPT_DISABLE;
      HalKeyConfig( OnboardKeyIntEnable, OnBoard_KeyCallback);
    }
  }
  /* If no key is currently pressed down and interrupt
     is disabled, enable interrupt and turn off polling */
  else
  {
    if( OnboardKeyIntEnable == HAL_KEY_INTERRUPT_DISABLE )
    {
      OnboardKeyIntEnable = HAL_KEY_INTERRUPT_ENABLE;
      HalKeyConfig( OnboardKeyIntEnable, OnBoard_KeyCallback);
    }
  }