Inside Macintosh: Devices /

Chapter 1 - Device Manager

This chapter describes how your application can use the Device Manager to transfer information into and out of a Macintosh computer. The Device Manager controls the exchange of information between applications and hardware devices.

This chapter provides a brief introduction to devices and device drivers (the programs that control devices) and then explains how you can use the Device Manager functions to

• open, close, and exchange information with device drivers
• write your own device driver that can communicate with the Device Manager
• provide a user interface for your device driver by making it a Chooser extension or desk accessory.

You should read the sections "About the Device Manager" and "Using the Device Manager" if your application needs to use the Device Manager to communicate with a device driver. Applications often communicate with the Device Manager indirectly, by calling functions of other managers (for example, the File Manager) that use the Device Manager. However, sometimes applications must call Device Manager functions directly.

The sections "Writing a Device Driver," "Writing a Chooser-Compatible Device Driver," and "Writing a Desk Accessory," provide information you'll need if you are writing your own device driver.

If you writing a device driver, you should understand how memory is organized and allocated in Macintosh computers. See Inside Macintosh: Memory, for this information. You should also be familiar with resources and how the system searches resource files. You can find this information in the chapter "Resource Manager" in Inside Macintosh: More Macintosh Toolbox. If your device driver is to perform background tasks, you'll need to understand how processes are scheduled. Inside Macintosh: Processes covers these topics. If your driver will control a hardware device, you should read Designing Cards and Drivers for the Macintosh Family, third edition.

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Chapter Contents

Introduction to Devices and Drivers

About the Device Manager

The Device Control Entry

The Unit Table

The Driver I/O Queue

Driver Routines

Driver Resources

Using the Device Manager

Opening and Closing Device Drivers

Communicating With Device Drivers

Controlling and Monitoring Device Drivers

Writing a Device Driver

Creating a Driver Resource

Responding to the Device Manager

Entering and Exiting From Driver Routines

Writing Open and Close Routines

Writing a Prime Routine

Writing Control and Status Routines

Handling Asynchronous I/O

Installing a Device Driver

Writing a Chooser-Compatible Device Driver

How the Chooser Works

Creating a Chooser Extension File

Creating a Device Package

Responding to the Chooser

Allocating Private Storage

Writing a Desk Accessory

How Desk Accessories Work

Creating a Driver Resource for a Desk Accessory

Opening and Closing a Desk Accessory

Responding to Events

Device Manager Reference

Data Structures

Device Manager Parameter Block

Device Control Entry

Device Manager Functions

Opening and Closing Device Drivers

Communicating With Device Drivers

Controlling and Monitoring Device Drivers

Writing and Installing Device Drivers

Resources

The Driver Resource

Summary of the Device Manager

C Summary

Constants

Data Types

Functions

Pascal Summary

Constants

Data Types

Routines

Assembly-Language Summary

Data Structures

Trap Macros

Result Codes