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Finding and Accessing Devices

This chapter assumes you have an application or other user-space code that needs to access one or more specific types of device and that you:

• Have determined that your application can’t satisfy its hardware needs with the higher-level APIs described in “Hardware-Access Options”

• Are familiar with the I/O Kit summary information in “Device Access and the I/O Kit”

• Want to know how to access hardware with an I/O Kit device interface or using the POSIX API

This chapter provides a generic blueprint for accessing devices with I/O Kit device interfaces and device files. It describes several ways to find devices in the I/O Registry and how to examine each device you find. It then describes how to access a device through a device interface or a device file.

Your code will implement many of the functions discussed in this chapter because some actions, such as getting a Mach port to communicate with the I/O Kit and looking up your devices in the I/O Registry, are common to all applications that use the I/O Kit API to access hardware.

This chapter describes how to use several I/O Kit and Core Foundation functions. You can view the header file describing the I/O Kit functions in /System/Library/Frameworks/IOKit.framework/Headers/IOKitLib.h and the Core Foundation functions in various files in /System/Library/Frameworks/CoreFoundation.framework/Headers. You can also view header documentation for these files on disk in /Developer/Documentation or on the web in the Device Drivers Reference Library. Complete sample projects are available in Sample Code > Hardware & Drivers and, when you install the Developer package, in /Developer/Examples/IOKit.

Contents:

Finding Devices in the I/O Registry
Examining Matching Objects
Putting It All Together: Accessing a Device

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