## Physical Device Driver Reference

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### Character Device Driver and Monitors

A character device driver and its monitors are interdependent. The implementation of the character device driver determines the ground rules for its monitors, including:

The definition of its data streams and monitor chains
The format of the data flowing through its monitor chains
The rules on consuming, modifying, and returning data

Because a monitor directly interacts with a data stream, there is a danger of severely affecting the data stream if a monitor is not well-behaved ( that is, if the monitor does not adhere to the rules of the character device driver). The interdependence of a character device driver and its monitors can be directly demonstrated by presenting a description of the sequence of events occurring in the character device driver and its monitors during:

Monitor registration and termination
Movement of data through a monitor chain