OpenVMS VAX Device Support Reference Manual

This document serves as a reference manual for system programmers developing device drivers for devices connected to VAX processors running OpenVMS VAX Version 6.1. It provides detailed information on the data structures, macros, and routines essential for device driver programming. Key areas covered include:

• Data Structures: Descriptions of critical I/O database components such as the adapter control block (ADP), channel control block (CCB), device data block (DDB), I/O request packet (IRP), and unit control block (UCB), along with multiprocessing synchronization structures like the spinlock data structure (SPL) and per-CPU database (CPU).
• System Macros: A comprehensive list of macros used by drivers for tasks such as dispatching based on adapter or CPU characteristics, managing device and fork locks, allocating/releasing map registers and data paths, handling SCSI commands, and performing byte swapping.
• Operating System Routines: Details on the context, synchronization, and I/O requirements of operating system routines invoked by drivers or driver macros, covering functions like memory allocation/deallocation, I/O postprocessing, error logging, and timer queue management.
• Device Driver Entry Points: Descriptions of standard driver routines for various operations, including alternate and main start-I/O, cancel-I/O, cloned UCB handling, controller and unit initialization, driver unloading, Function Decision Table (FDT) processing, interrupt service, register dumping, timeout handling, unit delivery, and unsolicited interrupt services.