It's a simple library with a set of classes to access hardware tunables and properties that tend to vary from platform to platform, or device to device, but are still useful to present functionality to the end user. Examples of these tunables are display color calibration, processor eco modes, vibration strength, sensor reset/recalibrate, etc.
The library should present a common interface and completely abstract implementation details so that the UI part of said functionality (the knobs and buttons users actually interact with) can be implemented at a single location on any shipped platform app (typically, Settings). No UI or layout elements should be included in here.
Classes present in this repository are dummies, and should fully implement the expected API that'll be used in Settings.
Each device should implement its own classes for supported hardware tunables, and signal their existence by adding a BOARD_HARDWARE_CLASS variable to its BoardConfig, pointing to the path where said classes can be found. The Nexus4, for instance, has
BOARD_HARDWARE_CLASS := device/lge/mako/cmhw/
Every class present in this framework addresses a single tunable; Devices don't need to implement all the classes, but for every one that is implemented, all methods existing in this dummy implementation must be present, since the client applications will expect them to be there.
There are reasons for this not to be implemented as an interface definition, or a set of superclasses. Fully overloading the reference class isn't pretty, but at this point it's the most flexible option we have, especially since we still haven't fully closed what we're going to put in here.