I/O Flow and Dispatching in WDF Drivers

Updated: April 10, 2007

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I/O processing is the heart of any driver. To understand how to implement robust I/O handling code in your driver, you must understand how I/O requests flow from an application to your driver, how the Windows Driver Foundation (WDF) simplifies the driver's I/O processing tasks, and what your driver should do to complete an I/O request. This paper provides information about I/O flow in both the user-mode driver framework (UMDF) and the kernel-mode driver framework (KMDF) and provides guidelines for handling I/O requests in both UMDF and KMDF drivers.

This information applies for the following operating systems:
Windows Server 2008
Windows Vista
Microsoft Windows Server 2003
Microsoft Windows XP
Microsoft Windows 2000 (KMDF only)

Included in this white paper:

• Common I/O Request Types

• I/O Transfer Types

• I/O Request Flow

• I/O Request Objects

• I/O Queues

• I/O Event Callbacks

• Completing I/O Requests

• Canceled and Suspended Requests

• Adaptive Time-outs in UMDF