VAX/VMS Device Driver Driver Tables

This document, "Driver Tables," is part of the VAX/VMS Educational Services training for device drivers. It outlines the fundamental data structures and tables required for developing device drivers on the VAX/VMS operating system.

The core of the document focuses on three essential tables:

1. Driver Prologue Table (DPT): Defined at the beginning of a driver, the DPT contains general driver information (e.g., name, size, adapter type) and crucial initialization data for other data structures like the Device Data Block (DDB), Unit Control Block (UCB), and Channel Request Block (CRB). It specifies initial values for device characteristics, interrupt levels, and routine addresses.
2. Driver Dispatch Table (DDT): This table lists the addresses of various driver routines, including the start I/O routine, unsolicited interrupt routine, cancel I/O routine, and unit initialization routine. It also specifies the sizes of diagnostic and error log buffers.
3. Function Decision Table (FDT): The FDT defines the legal function codes that a driver can process, mapping them to specific preprocessing routines responsible for handling those functions.

The document details the various fields within the DDB, CRB, and UCB that a driver needs to initialize. It also provides comprehensive explanations of the system macros—DPTAB, DPT_STORE, DDTAB, and FUNCTAB—used to create and populate these tables. These macros ensure proper initialization of data structures and definition of driver entry points, which are critical for integrating new devices and their drivers into the VAX/VMS system. The goal is to enable developers to correctly define and utilize these tables for robust device driver implementation.