A port driver manages and controls the adapter for a given block device. The port driver detects and initializes the adapter, handles interrupts, transmits I/O requests to the device, and carries out adapter-level error recovery and logging. A port driver typically works with a specific, proprietary adapter and therefore is retained in memory and used by Windows 95 only if the given adapter is present in the system.
This part of the Windows 95 DDK Design and Implementation Guide describes the responsibilities and requirements of a port driver and explains how to build and test a port driver for your adapter.