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HIDL

The HAL Interface Description Language (HIDL) specifies the interface between a HAL and its users. It defines types and method calls, collected into interfaces and packages. HIDL is a system for communicating between codebases that may be compiled independently and is intended for inter-process communication. See the HIDL guides.
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Hardware Abstraction Layer (legacy)

A HAL defines a standard interface for hardware vendors to implement, which enables Android to be agnostic about lower-level driver implementations. Using a HAL allows you to implement functionality without affecting or modifying the higher level system. For an overview, see the HAL guide.
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Trade Federation

A continuous test framework designed for running tests on Android devices. It's a Java application which runs on a host computer, and communicates to one or more Android devices using ddmlib over adb. For details, see the Trade Federation Overview.