Layered device drivers split the code into an upper layer called the model device driver (MDD) and a lower layer called the platform dependent driver (PDD).

• 分层的设备驱动程序把代码分成一个模型设备驱动(MDD)层和平台相关驱动层(PDD)。MDD层驱动可以对一个类型的设备进行驱动。