headless: Add docs and more information am: b56f6db0 am: 91ab80b5 am: a708d307

##

## bluetooth headless

##

## A device-side executable that consists of a binary executable

## driving the Android libbluetooth libraries.

##

Requirements:

    1. Android installation,

    2. Root access to adb connected Android device.

Build: Source, lunch and build as typical Android target for selected device and architecture.

    cd $ANDROID_BUILD_TOP

    . build/envsetup.sh && lunch <target>

    make bt_headless

Install: Push the binary to an executable area on target device.

    adb push out/target/product/<device..arch>/bt_headless/bt_headless /data/data/.

Prepare: Ensure the system is queisced to prevent resource conflicts from the bluetooth process.

    adb shell stop

Run: Script or directly execute the target file.

    adb shell /data/data/bt_headless --flags=INIT_logging_debug_enabled_for_all=true,INIT_gd_acl=true nop

void HeadlessStack::SetUp() {

  LOG(INFO) << __func__ << " Entry";

  int status = bluetoothInterface.init(&bt_callbacks, false, false, 0,

                                       StackInitFlags(), false);

  const bool start_restricted = false;

  const bool is_common_criteria_mode = false;

  const int config_compare_result = 0;

  const bool is_atv = false;

  int status = bluetoothInterface.init(

      &bt_callbacks, start_restricted, is_common_criteria_mode,

      config_compare_result, StackInitFlags(), is_atv);

  (status == BT_STATUS_SUCCESS)

      ? LOG(INFO) << __func__ << " Initialized bluetooth callbacks"

      : LOG(FATAL) << "Failed to initialize Bluetooth stack";