Figure 2-2 illustrates the general idea: whenever the system wants to carry out an operation on a device, it sends an IRP to the topmost filter driver in the stack.

• 图2-2阐明了这个大意：无论什么时候系统想要在一个设备上执行一个操作，它给在堆栈中最上层的过滤器发送一个IRP。