BlueZ for Android ***************** Since Android 4.2 there exists a well standardized HAL interface that the Bluetooth stack is expected to provide and which enables the easy replacement of the stack of choice on Android. Android BlueZ is intended as a drop-in replacement to Android provided Bluetooth stack. More details about BlueZ for Android architecture and components can be found in android/hal-ipc-api.txt file. Supported Android version: 4.4 Building and running on Android =============================== Steps needed to build and run Android Open Source Project 4.4.2 with integrated BlueZ. Build requirements ------------------ - GLib - Android 4.2 or later don't provide GLib and one must provide it in 'external/bluetooth/glib' folder of Android tree. Sample Android GLib port is available at https://code.google.com/p/aosp-bluez.glib/ - SBC - A2DP code requires SBC library (version 1.2 or higher) present in 'external/bluetooth/sbc' directory. Library is build from Android.mk provided by BlueZ. SBC code is available at git://git.kernel.org/pub/scm/bluetooth/sbc - Bionic support - Currently only 'master' branch available at https://android.googlesource.com/platform/bionic provides all required functionality and running BlueZ on release branch requires backporting missing features (currently epoll_create1 and ppoll calls for Android 4.4.2). Sample Bionic for Android 4.4.2 with all required features backported is available at https://code.google.com/p/aosp-bluez.platform-bionic/ Runtime requirements -------------------- BlueZ HAL library requires 'bluetoothd' and 'bluetoothd-snoop' services to be available on Android system. Some permissions settings are also required. This can be done by importing init.bluetooth.rc file in init.rc file of targeted board: import init.bluetooth.rc For convenience examples are provided at: https://code.google.com/p/aosp-bluez.device-lge-mako/ (Nexus 4) https://code.google.com/p/aosp-bluez.device-asus-flo/ (Nexus 7 2013) Downloading and building ------------------------ Building for Android requires full Android AOSP source tree. Sample Android 4.4.2 tree with all required components present is available at http://code.google.com/p/aosp-bluez/ This tree provides support for Nexus4 (target aosp_mako-userdebug) and Nexus 7 2013 (target aosp_flo-userdebug). Tree does not provide binary blobs needed to run Android on supported devices. Those can be obtained from https://developers.google.com/android/nexus/drivers. Binary blobs needs to be unpacked (EULA acceptance required) into 'vendor' directory of Android tree. Downloading: repo init -u https://code.google.com/p/aosp-bluez.platform-manifest -b kitkat repo sync Building: source build/envsetup.sh lunch aosp_mako-userdebug or lunch aosp_flo-userdebug make -j8 Flashing: adb reboot bootloader fastboot flashall -w After full build is done it is possible to rebuild only BlueZ: 'cd external/bluetooth/bluez/android/' 'mm' (or 'mm -B' to force rebuilding of all files) 'adb sync' to update target device. Linux Kernel requirements ------------------------- BlueZ for Android uses Linux Bluetooth subsystem and it must be enabled in kernel. Minimal required version of management interface is 1.3. This corresponds to Linux 3.9 but latest available version is recommended. Other requirements include UHID and network bridge support. Following kernel options should be enabled: CONFIG_BT CONFIG_BT_RFCOMM CONFIG_BT_RFCOMM_TTY CONFIG_BT_BNEP CONFIG_BT_BNEP_MC_FILTER CONFIG_BT_BNEP_PROTO_FILTER CONFIG_BRIDGE CONFIG_UHID Also BT chip driver needs to be enabled e.g: CONFIG_BT_HCIBTUSB If it is not possible to use new enough Linux kernel one can use updated bluetooth subsytem from Backports project. More information about Backports can be found at https://backports.wiki.kernel.org. Sample kernels using backports for running BlueZ on Android are available at https://code.google.com/p/aosp-bluez. Running with Valgrind --------------------- BlueZ for Android is preconfigured to be easily run under Valgrind memcheck. Appropriate configuration and required modules are automatically included when building either userdebug or eng variant of Android platform. Valgrind can be enabled in runtime by setting "persist.sys.bluetooth.valgrind" property to either literal "true" or any numeric value >0. For example: adb root adb shell setprop persist.sys.bluetooth.valgrind true After changing property value Bluetooth need to be restarted to apply changes (this can be done using UI, just disable and enable it again). Property is persistent, i.e. there's no need to enable Valgrind again after reboot. It's recommended to have unstripped libglib.so installed which will enable complete backtraces in Valgrind output. Otherwise, in many cases backtrace will break at e.g. g_free() function without prior callers. It's possible to have proper library installed automatically by appropriate entry in Android.mk, see https://code.google.com/p/aosp-bluez.glib/ for an example. Enabling BlueZ debugs --------------------- BlueZ debug logs can be enabled in runtime by setting "persist.sys.bluetooth.debug" property to either literal "true" or any numeric value >0. For example: adb root adb shell setprop persist.sys.bluetooth.debug 1 After changing property value Bluetooth needs to be restarted to apply changes. There is also a possibility to enable mgmt debug logs which also enables debugs as above. To enable it procced in the same way as described above but use system properties called: persist.sys.bluetooth.mgmtdbg Note: Debugs are only available on NON USER build variants Customization ------------- It is possible to customize BlueZ for Android through Android system properties. This may include enabling extra profiles or features inside HALs implementation These properties are read on Bluetooth stack startup only and require stack restart if changed. All customization properties names start with "persist.sys.bluetooth." followed by specific HAL name e.g. "persist.sys.bluetooth.handsfree". This section list available customization options. Property Value Description ------------------------------------------- mode bredr Enable BlueZ in BR/EDR mode le Enable BlueZ in LE mode Enable BlueZ in default mode - enable BR/EDR/LE if available. handsfree hfp Enable Handsfree Profile (HFP) with narrowband speech only hfp_wbs Enable Handsfree Profile (HFP) with narrowband and wideband speech support Don't enable Handsfree Profile (HFP) Building and running on Linux ----------------------------- It is possible to build and test BlueZ for Android daemon on Linux (eg. PC). Simply follow instructions available at README file in BlueZ top directory. Android daemon binary is located at android/bluetoothd. See next section on how to test Android daemon on Linux. Testing tool ------------ BT HAL test tools located in android/haltest is provided for HAL level testing of both Android daemon and HAL library. Start it with '-n' parameter and type 'bluetooth init' in prompt to initialize HAL library. Running without parameter will make haltest try to initialize all services after start. On Android required bluetoothd service will be started automatically. On Linux it is required to start android/bluetoothd manually before init command timeout or use provided android/system-emulator, which takes care of launching daemon automatically on HAL library initialization. To deinitialize HAL library and stop daemon type 'bluetooth cleanup'. Type 'help' for more information. Tab completion is also supported. Implementation status ===================== Summary of HALs implementation status. complete - implementation is feature complete and Android Framework is able to use it normally partial - implementation is in progress and not all required features are present, Android Framework is able to use some of features initial - only initial implementations is present, Android Framework is able to initialize but most likely not able to use it not started - no implementation, Android Framework is not able to initialize it Profile ID HAL header Status --------------------------------------- core bluetooth.h complete a2dp bt_av.h complete gatt bt_gatt.h partial bt_gatt_client.h partial bt_gatt_server.h initial handsfree bt_hf.h complete hidhost bt_hh.h complete health bt_hl.h initial pan bt_pan.h complete avrcp bt_rc.h complete socket bt_sock.h complete Implementation shortcomings =========================== It is possible that some of HAL functionality (although being marked as complete) is missing implementation due to reasons like feature feasibility or necessity for latest Android Framework. This sections provides list of such deficiencies. Note that HAL library is always expected to fully implement HAL API so missing implementation might happen only in daemon. HAL Bluetooth ------------- methods: dut_mode_send never called from Android Framework le_test_mode never called from Android Framework get_remote_service_record never called from Android Framework callbacks: dut_mode_recv_cb empty JNI implementation le_test_mode_cb empty JNI implementation properties: BT_PROPERTY_SERVICE_RECORD not supported for adapter and device, for device this property is to be returned as response to get_remote_service_record, not sure what to return on get_property calls (records of all services?) BT_PROPERTY_REMOTE_VERSION_INFO information required by this property (LMP information) are not accessible from mgmt interface, also marking this property as settable is probably a typo in HAL header HAL Socket ---------- Support only for BTSOCK_RFCOMM socket type. HAL AVRCP --------- methods: list_player_app_attr_rsp never called from Android Framework list_player_app_value_rsp never called from Android Framework get_player_app_value_rsp never called from Android Framework get_player_app_attr_text_rsp never called from Android Framework get_player_app_value_text_rsp never called from Android Framework set_player_app_value_rsp never called from Android Framework callbacks: list_player_app_attr_cb NULL JNI implementation list_player_app_values_cb NULL JNI implementation get_player_app_value_cb NULL JNI implementation get_player_app_attrs_text_cb NULL JNI implementation get_player_app_values_text_cb NULL JNI implementation set_player_app_value_cb NULL JNI implementation Known Android issues ==================== It is possible that BlueZ is triggering bugs on Android Framework that could affect qualification or user experience. This section provides list of recommended Android fixes that are not part of latest AOSP release supported by BlueZ. https://android-review.googlesource.com/82757 https://android-review.googlesource.com/87670 https://android-review.googlesource.com/88384 Unimplemented Bluetooth features ================================ Some Bluetooth functionality require support from outside of BT stack eg. telephony stack. This sections describes profiles optional features not implemented due to lack of support in other Android subsystems or missing API in respective BT HALs. Profile Feature Comments -------------------------------------------------------- HFP Attach a phone number to AT+BINP=1 a voice tag HFP Enhanced Call Control AT+CHLD={1x,2x} HFP Explicit Call Transfer AT+CHLD=4 HFP Response and Hold AT+BTRH, +BTRH HFP In-band Ring Tone +BSIR AVRCP Player Settings HAL API present but not used AVRCP Browsing No HAL API