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