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Configuring a Shared Library

After creating an audio policy configuration, you must package the HAL implementation into a shared library and copy it to the appropriate location:

  1. Create a device/<company>/<device>/audio directory to contain your library's source files.
  2. Create an Android.mk file to build the shared library. Ensure the Makefile contains the following line:
    LOCAL_MODULE := audio.primary.<device>
    

    Your library must be named audio.primary.<device>.so so Android can correctly load the library. The primary portion of this filename indicates that this shared library is for the primary audio hardware located on the device. The module names audio.a2dp.<device> and audio.usb.<device> are also available for Bluetooth and USB audio interfaces. Here is an example of an Android.mk from the Galaxy Nexus audio hardware:

    LOCAL_PATH := $(call my-dir)
    
    include $(CLEAR_VARS)
    
    LOCAL_MODULE := audio.primary.tuna
    LOCAL_MODULE_RELATIVE_PATH := hw
    LOCAL_SRC_FILES := audio_hw.c ril_interface.c
    LOCAL_C_INCLUDES += \
            external/tinyalsa/include \
            $(call include-path-for, audio-utils) \
            $(call include-path-for, audio-effects)
    LOCAL_SHARED_LIBRARIES := liblog libcutils libtinyalsa libaudioutils libdl
    LOCAL_MODULE_TAGS := optional
    
    include $(BUILD_SHARED_LIBRARY)
    


  3. If your product supports low latency audio as specified by the Android CDD, copy the corresponding XML feature file into your product. For example, in your product's device/<company>/<device>/device.mk Makefile:

    PRODUCT_COPY_FILES := ...
    
    PRODUCT_COPY_FILES += \
    frameworks/native/data/etc/android.hardware.audio.low_latency.xml:system/etc/permissions/android.hardware.audio.low_latency.xml \
    


  4. Copy the audio policy configuration file you created earlier to the system/etc/ directory in your product's device/<company>/<device>/device.mk Makefile. For example:

    PRODUCT_COPY_FILES += \
            device/samsung/tuna/audio/audio_policy.conf:system/etc/audio_policy.conf
    


  5. Declare the shared modules of your audio HAL that are required by your product in the product's device/<company>/<device>/device.mk Makefile. For example, the Galaxy Nexus requires the primary and Bluetooth audio HAL modules:
    PRODUCT_PACKAGES += \
            audio.primary.tuna \
            audio.a2dp.default