What does this document tell?

This document details how to use the vehicle service if you are implementhing
HAL. It lists the various places to look for code and how to build and test the
code on your own dev device.

This code also provides a simple command line utility for the target to test the
vehicle HAL.

What is the code?

The code is split into folowing logical components:
a) hardware/libhardware/include/hardware/vehicle.h - this is the main HAL
interface that will be required to be implemented by the OEMs. It includes all
documentation necessary to understand what vehicle subsystems are exposed,
various units, capabilities and any other relevant details about the HAL design
itself.

b) hardware/libhardware/modules/vehicle/vehicle.c
This is a reference implementation for the OEMs to have a peek into getting
started with a barebones structure. There are implementation for each of the
critical HAL functions such as, get(), set() and subscribe().

c) hardware/libhardware/tests/vehicle/vehicle_test.cpp & vehicle_test_fixtures.h
These are native tests that can be run on the target to validate basic
features of HAL implementation. Things such as loading of HAL and
basic functions are implemented (by check if the returned functions are not NULL
pointers) can be asserted. It also checks if the subscribe function is doing its
job by spitting out data at continuous intervals and printed on the stdout.

d) hardware/libhardware/tests/vehicle/vehicle-hal-tool.c
This tool will provide you with a simple utility which can set commands to the
HAL such as:
i) Getting a property (and printing its value).
ii) Setting a property (and the HAL will take some setting action).
iii) Subscribe to a property (and the HAL should send you values at some certain
intevals).

See the usage() function in vehicle-hal-tool.c for details on how to use the
binary.

How to build and run?

You can build everything by issuing the following from the top of directory. It
is assumed that you have done a first run of make from the top level so that
intermediates are generated.

$ croot
$ mmm hardware/libhardware

This will generate the following binaries that we care about:
i) out/target/product/XXX/vendor/lib/hw/vehicle.default.so
ii) out/target/product/XXX/data/nativetest/vehicle_tests
iii) out/target/product/XXX/system/bin/vehicle-hal-tool

The location for the first shared library would be:
$ adb push out/target/product/XXX/vendor/lib/hw/vehicle.default.so
/vendor/lib/hw
You can also use 'adb sync' if you like, although this is the easiest least
hassle way of putting it in place.

The second binary is a native test - which is nothing but an executable for the
target device. You can load it anywhere in your /data directory and run it as:
$ adb push out/target/product/XXX/data/nativetest/vehicle_tests
/data/tmp/vehicle_tests
$ adb shell
$ ./data/tmp/vehicle_tests
<...output should be spitted with passing tests for atleast the reference
implementation ...>

The last binary is the command line tool, to push the binary on your target do:
$ adb push out/target/product/XXX/system/bin/vehicle-hal-tool
/data/tmp/vehicle-hal-tool