Devices have device data, and this is often used to persist device information that needs to remain consistent across reloads.
You can explicitly set a particular devicedata as "Set By Device" so that it can not be edited by a user.
Accessing this device-data depends on:
* Whether you are accessing your own device data (accessors are provided for this), or Whether you are accessing someone else's device data (The General Info Plugin is used for this.)
* Whether you are doing this from a C++ device (using the accessors defined in Gen_Devices for your device), or from a Ruby/GSD device (using the DevData_[xxx] accessors (where xxx is the particular ID of device data you're trying to access.)