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    <title>Configuring a Shared Library</title>
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<p>After creating an
<a href="/devices/audio/implement-policy.html">audio policy
configuration</a>, you must package the HAL implementation into a shared library
and copy it to the appropriate location:</p>

<ol>
<li>Create a <code>device/&lt;company&gt;/&lt;device&gt;/audio</code>
directory to contain your library's source files.</li>
<li>Create an <code>Android.mk</code> file to build the shared library. Ensure
the Makefile contains the following line:
<br>
<pre class="devsite-click-to-copy">
LOCAL_MODULE := audio.primary.&lt;device&gt;
</pre>
<br>
<p>Your library must be named <code>audio.primary.&lt;device&gt;.so</code>
so Android can correctly load the library. The <code>primary</code> portion of
this filename indicates that this shared library is for the primary audio
hardware located on the device. The module names
<code>audio.a2dp.&lt;device&gt;</code> and
<code>audio.usb.&lt;device&gt;</code> are also available for Bluetooth and
USB audio interfaces. Here is an example of an <code>Android.mk</code> from the
Galaxy Nexus audio hardware:</p>

<pre class="devsite-click-to-copy">
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)
</pre>
</li>
<br>
<li>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 <code>device/&lt;company&gt;/&lt;device&gt;/device.mk</code>
Makefile:
<pre class="devsite-click-to-copy">
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 \
</pre>
</li>
<br>
<li>Copy the audio policy configuration file you created earlier to the
<code>system/etc/</code> directory in your product's
<code>device/&lt;company&gt;/&lt;device&gt;/device.mk</code> Makefile.
For example:
<pre class="devsite-click-to-copy">
PRODUCT_COPY_FILES += \
        device/samsung/tuna/audio/audio_policy.conf:system/etc/audio_policy.conf
</pre>
</li>
<br>
<li>Declare the shared modules of your audio HAL that are required by your
product in the product's
<code>device/&lt;company&gt;/&lt;device&gt;/device.mk</code> Makefile.
For example, the Galaxy Nexus requires the primary and Bluetooth audio HAL
modules:
<pre class="devsite-click-to-copy">
PRODUCT_PACKAGES += \
        audio.primary.tuna \
        audio.a2dp.default
</pre>
</li>
</ol>

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