Sending I/O Requests to Lower Drivers
[This topic applies to UMDF 1.x.]
When a driver receives an I/O request that it cannot fully process, the driver typically forwards the received request to the next lower driver in the stack. The driver calls the IWDFIoRequest::Send method to forward the request. To forward synchronously, the driver passes the WDF_REQUEST_SEND_OPTION_SYNCHRONOUS flag in the Flags parameter. Otherwise, the driver forwards the request asynchronously. Before the driver forwards the request, it should register a completion routine. For more information, see Completing I/O Requests.