Block Driver Development Concepts (Windows Embedded CE 6.0)
If you want your driver to interface with the FAT file system or FSD Manager, your block driver should expose the stream interface. For more information about the stream interface, see Stream Interface Driver Development Concepts.
The Device Manager manages drivers that expose the stream interface. For more information about the Device Manager, see Device Manager.
The stream interface exposes file I/O functions so it can interact with applications. The XXX_IOControl (Device Manager) function is the most important of the I/O functions for block device drivers. This function handles all I/O requests to block devices.