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Power Management; Policy Maker vs. Power Controller

Q: What are the differences between a Power Management Policy Maker and a Power Management Power Controller on Mac OS X?

A: A Policy Maker does just that, it decides how your Macintosh computer will manage power. A Power Controller refers usually to an IOKit driver for a device that wants to participate in Power Management.

For instance, there are presently three Policy Makers for Mac OS X. They are located in the Energy Saver Preferences and they control the settings for "sleep", the "display" and the "disk". You set these preference as you wish.

A Power Controller registers with Power Management via IOKit APIs and is send power events when and if they occur. The Power Controller will respond as needed to an event.

For instance, your IOKit driver may choose to put its device to sleep when a sleep event arrives or return a "no not now" result if I/O is still pending. See IOKit Fundamentals Chapter 10 for details. The URL is:

http://developer.apple.com/documentation/Darwin/kernel.html

[Feb 13 2002]

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