A vendor-supplied driver (VSD) intercepts and processes I/O requests for a given block device. The VSD gives a vendor an efficient way to incorporate enhancements into an existing layered block device driver or to extend the capabilities of the driver to new but similar hardware. A VSD typically works with a given port driver or set of port drivers and therefore is retained in memory and used by Windows 95 only if the given adapter supported by the port driver is present in the system.
This part of the Windows 95 DDK Design and Implementation Guide describes the responsibilities and requirements of a VSD and explains how to build and test a VSD.