en/devices/architecture/vndk/snapshot-generate.html - platform/docs/source.android.com - Git at Google

 <html devsite>
   <head>
     <title>Generating VNDK Snapshots</title>
     <meta name="project_path" value="/_project.yaml" />
     <meta name="book_path" value="/_book.yaml" />
   </head>
   {% include "_versions.html" %}
   <body>
   <!--
       Copyright 2018 The Android Open Source Project

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       distributed under the License is distributed on an "AS IS" BASIS,
       WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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 <p>
   A VNDK snapshot is a set of VNDK-core and VNDK-SP libs for an Android release.
   You can upgrade only the system partition if the system.img includes the
   corresponding VNDK snapshot needed by the vendor.img.
 </p>

 <aside class="note"><strong>Note:</strong> This page provides design details for
   building and updating a VNDK snapshot. For details on the background,
   definition, and use cases of VNDK snapshots, refer to
   <a href="/devices/architecture/vndk/snapshot-design">VNDK Snapshot Design</a>.
 </aside>

 <p>
   Official VNDK snapshots are built automatically on the Android build server
   and checked into <code>/prebuilts/vndk</code> of the Android source tree. For
   development purposes, you can build VNDK snapshots locally. VNDK snapshots are
   supported for arm, arm64, x86, and x86_64 TARGET_ARCH flavors.
 </p>

 <h2 id="snapshot-build-artifacts">Snapshot build artifacts</h2>

 <p>
   The Android build server generates build artifacts for VNDK snapshots using
   the following build parameters and build commands.
 </p>

 <h3 id="build-parameters">Build parameters</h3>

 <p>
   The build target name is <code>vndk</code> and the build target configuration
   is as follows:
 </p>

 <ul>
   <li>TARGET_PRODUCT=aosp_{TARGET_ARCH}_ab</li>
   <li>TARGET_BUILD_VARIANT=user</li>
   <li>TARGET_ARCH. Same as Generic System Image (GSI) target archs (arm, arm64,
   x86, x86_64).</li>
   <li>TARGET_ARCH_VARIANT. For snapshot v27 (Android 8.1), includes popular
   configurations (listed below); future releases may include other arch/cpu
   variants.</li>
 </ul>

 <table>
 <thead>
 <tr>
 <th>TARGET_PRODUCT</th>
 <th>TARGET_ARCH</th>
 <th>TARGET_ARCH_VARIANT</th>
 </tr>
 </thead>
 <tbody>
 <tr>
 <td>aosp_arm_ab</td>
 <td>arm</td>
 <td>armv7-a-neon</td>
 </tr>
 <tr>
 <td>aosp_arm64_ab</td>
 <td>arm64</td>
 <td>armv8-a</td>
 </tr>
 <tr>
 <td>aosp_x86_ab</td>
 <td>x86</td>
 <td>x86</td>
 </tr>
 <tr>
 <td>aosp_x86_64_ab</td>
 <td>x86_64</td>
 <td>x86_64</td>
 </tr>
 </tbody>
 </table>

 <h3 id="build-commands">Build commands</h3>

 <p>
   For official snapshots, Android {{ androidPVersionNumber }} includes a new
   dummy target (<code>vndk</code>) in
   <a href="https://android.googlesource.com/platform/build/+/master/core/tasks/vndk.mk">vndk.mk</a>
   that builds and outputs a VNDK snapshot to <code>$DIST_DIR</code>. The
   snapshot zip file uses the format <code>android-vndk-{TARGET_ARCH}.zip</code>.
   For example:
 </p>

 <pre class="prettyprint">
 $ lunch aosp_&lt;ARCH&gt;_ab-user
 $ make -j vndk dist [BOARD_VNDK_VERSION=current]
 </pre>

 <p>
   The Android build server uses the
   <a href="https://android.googlesource.com/platform/development/+/master/vndk/snapshot/build.sh">build.sh</a>
   script to build all supported arch flavors with the following command:
 </p>

 <pre class="prettyprint">
 $ DIST_DIR=%dist_dir% development/vndk/snapshot/build.sh
 </pre>

 <p>
   VNDK snapshots for an Android Version are generated from the
   <code>&lt;Android Version&gt;-release</code> branch.
 </p>

 <h3 id="build-locally">Building locally</h3>

 <p>
   During development, you can build VNDK snapshots from a local source tree with
   the following commands:
 </p>

 <ul>
   <li>To build all supported archs at once, execute the build script
   (<code>build.sh</code>):
 <pre class="prettyprint">
 $ cd $ANDROID_BUILD_TOP
 $ development/vndk/snapshot/build.sh
 </pre>
   </li>
   <li>To build one specific TARGET_ARCH:

 <pre class="prettyprint">
 $ lunch aosp_&lt;ARCH&gt;_ab-user
 $ m -j vndk dist
 </pre>
   </li>
 </ul>

 <p>
   The corresponding <code>android-vndk-&lt;ARCH&gt;.zip</code> file is created
   under <code>$DIST_DIR</code>.
 </p>

 <h2 id="snapshot-files">Snapshot files</h2>

 <p>
   A VNDK snapshot includes the following files:
 </p>

 <ul>
   <li>Vendor variant of VNDK-core and VNDK-SP shared libraries.
     <ul>
     <li>LL-NDK shared libs are not needed as they are backward compatible.</li>
     <li>For 64bit targets, both TARGET_ARCH and TARGET_2ND_ARCH libraries are
     built and included.</li>
     </ul>
   </li>
   <li>List of VNDK-core, VNDK-SP, LL-NDK, and VNDK-private libraries is at
   <code>[vndkcore|vndksp|llndk|vndkprivate].libraries.txt</code>.</li>
   <li>Linker config file is <code>ld.config.txt</code>.</li>
   <li>License files. </li>
   <li><code>module_paths.txt</code>. Records the module paths for all VNDK
   libraries, which is needed for checking that GPL projects have sources
   released in a given Android source tree.</li>
 </ul>

 <p>
   For a given VNDK snapshot zip file,
   <code>android-vndk-{TARGET_ARCH}.zip</code>, the VNDK prebuilt libraries are
   grouped in separate directories named
   <code>arch-{TARGET_ARCH}-{TARGET_ARCH_VARIANT}</code> according to ABI
   bitness. For example, for <code>android-vndk-arm64.zip</code>, the 64-bit libs
   are placed under <code>arch-arm64-armv8-a</code> and the 32-bit libs are
   placed under <code>arch-arm-armv8-a</code>.
 </p>

 <h3 id="example-snapshot-dir-structure">Example: VNDK snapshot directory
 structure</h3>

 <p>
   The example below shows the directory structure for an arm64
   (<code>TARGET_ARCH=arm64</code>) VNDK snapshot zip file
   (<code>android-vndk-arm64.zip</code>).
 </p>

 <img src="/devices/architecture/images/vndk_snapshot_directory.png">
 <figcaption><strong>Figure 1. </strong>VNDK snapshot directory structure
 (example)</figcaption>

 <h2 id='upload-vndk-snapshots'>Uploading VNDK snapshots</h2>

 <p>
   VNDK snapshots are checked in the source tree under
   <code>/prebuilts/vndk/v&lt;VER&gt;</code>, where <code>&lt;VER&gt;</code> is
   equal to the version of the VNDK snapshot (which follows the SDK version of
   the corresponding Android release). For example, the O MR1 VNDK snapshot has
   version 27.
 </p>

 <h3 id="using-update-py">Using the update.py script</h3>

 <p>
   The <code>update.py</code> script
   (<code>/development/vndk/snapshot/update.py)</code> automates the process of
   adding a pre-built VNDK snapshot to the source tree. This script performs the
   following tasks:
 </p>

 <ol>
   <li>In <code>/prebuilts/vndk/v&lt;VER&gt;</code>, uses <code>repo start</code>
   to create new git branch.</li>
   <li>Fetches and unzips VNDK snapshot build artifacts.</li>
   <li>Runs <code>gen_buildfiles.py</code> to auto generate the build files
   (<code>Android.mk</code>, <code>Android.bp</code>).</li>
   <li>Runs <code>check_gpl_license.py</code> to verify the prebuilt libraries
   licensed under the General Public License (GPL) have sources released in
   current source tree.</li>
   <li>Uses <code>git commit</code> to commit new changes.</li>
 </ol>

 <h3 id="using-local-snapshots">Using locally-built VNDK snapshots</h3>

 <p>
   During development, you can use locally-built VNDK snapshots for testing. When
   the <code>--local</code> option is specified, <code>update.py</code> fetches
   VNDK snapshot build artifacts from local <code>$DIST_DIR</code> instead of the
   Android build server. Usage:
 </p>

 <pre class="prettyprint">
 $ python update.py &lt;VER&gt; --local
 </pre>

 <p>
   For example, to update the O MR1 VNDK snapshot with local build artifacts,
   run:
 </p>

 <pre class="prettyprint">
 $ python update.py 27 --local
 </pre>

 <p>
   Because local mode is designed for testing only, the script skips the GPL
   license checking and git commit steps.
 </p>

 <h3 id="dir-structure-prebuilts">Directory structure for prebuilts/vndk</h3>

 <img src="/devices/architecture/images/vndk_snapshot_prebuilt.png">
 <figcaption><strong>Figure 2. </strong>Prebuilts/vndk directory
 structure</figcaption>

 <h2 id="install-vndk-snapshot">Installing VNDK snapshots</h2>

 <p>
   The system image installs VNDK snapshot libraries at build time using the
   information in <code>BOARD_VNDK_VERSION</code>,
   <code>PRODUCT_EXTRA_VNDK_VERSIONS</code>, and <code>ro.vndk.version</code>.
   You can control which VNDK snapshots get installed from
   <code>/prebuilts/vndk/v&lt;VER&gt;</code> using one of the following options:
 </p>

 <ul>
   <li><strong>Option 1:</strong> <code>BOARD_VNDK_VERSION</code>. Use the
   snapshot modules for building the current vendor modules and install only the
   snapshot modules that are required for the vendor modules.</li>
   <li><strong>Option 2:</strong> <code>PRODUCT_EXTRA_VNDK_VERSIONS</code>.
   Install the VNDK snapshot modules regardless of the current vendor modules.
   This installs the prebuilt VNDK snapshots listed in
   <code>PRODUCT_EXTRA_VNDK_VERSIONS</code> without linking them to any other
   modules at build time.</li>
 </ul>

 <h3 id="set-board-vndk">Setting BOARD_VNDK_VERSION</h3>

 <p>
   <code>BOARD_VNDK_VERSION</code> shows the VNDK version that current vendor
   modules are required to build. If <code>BOARD_VNDK_VERSION</code> has an
   available VNDK snapshot version in <code>/prebuilts/vndk</code> directory, the
   VNDK snapshot indicated in <code>BOARD_VNDK_VERSION</code> is installed. If
   the VNDK snapshot is not available in the directory, a build error occurs.
 </p>

 <p>
   Defining <code>BOARD_VNDK_VERSION</code> also enables the VNDK modules to be
   installed. Vendor modules link with the VNDK snapshot version defined in
   <code>BOARD_VNDK_VERSION</code> at build time (this does not build current
   VNDK modules in the system source). When downloading the full source tree from
   a repository, both system and vendor sources are based on the same Android
   release.
 </p>

 <aside class="note"><strong>Note:</strong> Vendor modules use the current VNDK
   version of the system source tree, so you must set
   <code>BOARD_VNDK_VERSION</code> to <code>current</code>.
 </aside>

 <h3 id="set-product-extra">Setting PRODUCT_EXTRA_VNDK_VERSIONS</h3>

 <p>
   <code>PRODUCT_EXTRA_VNDK_VERSIONS</code> lists the extra VNDK versions to be
   installed. Normally it is enough to have one VNDK snapshot for the current
   vendor partition. However, in some cases you might need to include multiple
   snapshots in one system image. For example, Generic System Image (GSI) has
   multiple snapshots to support multiple vendor versions with one system image.
   By setting <code>PRODUCT_EXTRA_VNDK_VERSIONS</code>, you can install the VNDK
   snapshot modules in addition to the VNDK version in
   <code>BOARD_VNDK_VERSION</code>.
 </p>

 <p>
   If <code>PRODUCT_EXTRA_VNDK_VERSIONS</code> has a specific list of versions,
   the build system looks for pre-built snapshots of the version list in the
   <code>prebuilts/vndk</code> directory. If the build system locates all listed
   snapshots, it installs those snapshot files to each
   <code>out/target/product/&lt;board&gt;/system/lib[64]/vndk[-sp]-${VER}</code>.
   Missing versions generate a build error.
 </p>

 <p>
   The VNDK modules will not link with the vendor modules at build time but may
   be used at runtime if the vendor modules in vendor partition require one of
   the installed VNDK versions. <code>PRODUCT_EXTRA_VNDK_VERSIONS</code> is valid
   only if <code>BOARD_VNDK_VERSION</code> is defined. For example, to install
   the O MR1 VNDK snapshot to system.img:
 </p>

 <pre class="prettyprint">
 $ m -j PRODUCT_EXTRA_VNDK_VERSIONS=27
 </pre>

 <h3 id="platform-vndk">PLATFORM_VNDK_VERSION</h3>

 <p>
   <code>PLATFORM_VNDK_VERSION</code> defines the VNDK version for current VNDK
   modules in the system source. The value is set automatically:
 </p>

 <ul>
   <li>Prior to release, the <code>PLATFORM_VNDK_VERSION</code> is set as
   <code>PLATFORM_VERSION_CODENAME</code>.</li>
   <li>At release, <code>PLATFORM_SDK_VERSION</code> is copied to
   <code>PLATFORM_VNDK_VERSION</code>.</li>
 </ul>

 <p>
   After the Android version is released, the current VNDK libraries are
   installed to <code>/system/lib[64]/vndk-$SDK_VER</code> and
   <code>/system/lib[64]/vndk-sp-$SDK_VER</code>, where <code>$SDK_VER</code> is
   the version stored in <code>PLATFORM_VNDK_VERSION</code>.
 </p>

 <h3 id="namespace-config">Namespace configuration</h3>

 <p>
   The vendor modules search the required shared libraries using the namespace
   configuration in <code>/etc/ld.config.${VER}.txt</code> (where
   <code>${VER}</code> is obtained from the <code>ro.vndk.version</code>
   property). The namespace configuration has a versioned VNDK directory that
   uses the following syntax:
 </p>

 <ul>
   <li><code>/system/${LIB}/vndk-%VNDK_VER%</code></li>
   <li><code>/system/${LIB}/vndk-sp-%VNDK_VER%</code></li>
 </ul>

 <p>
   <code>%VNDK_VER%</code> is replaced with <code>PLATFORM_VNDK_VERSION</code>
   at build time, enabling a system image to provide multiple snapshots for each
   VNDK version.
 </p>

 <p>
   When <code>BOARD_VNDK_VERSION</code> is set to <code>current</code>, the
   <code>PLATFORM_VNDK_VERSION</code> is stored in <code>ro.vndk.version</code>,
   otherwise <code>BOARD_VNDK_VERSION </code>is stored in
   <code>ro.vndk.version</code>. <code>PLATFORM_VNDK_VERSION</code> is set to the
   SDK version when Android releases; prior to release, the alphanumeric Android
   code name is used for <code>PLATFORM_VNDK_VERSION</code>.
 </p>

 <h3 id="summary-vndk-version-settings">Summary of VNDK version settings</h3>

 <p>
   The table below summarizes the VNDK version settings.
 </p>

 <table>
 <thead>
 <tr>
 <th width="15%">Vendor<br>Build</th>
 <th>Board<br>Version</th>
 <th>SDK<br>Release</th>
 <th>Platform<br>Version</th>
 <th>Version<br>Property</th>
 <th>Install Directory</th>
 </tr>
 </thead>
 <tbody>
 <tr>
 <td rowspan=2>Current VNDK modules</td>
 <td rowspan=2><code>current</code></td>
 <td>Before</td>
 <td>&lt;CODE_NAME&gt;</td>
 <td>&lt;CODE_NAME&gt;</td>
 <td>/system/lib[64]/vndk[-sp]-&lt;CODE_NAME&gt;</td>
 </tr>
 <tr>
 <td>After</td>
 <td>&lt;SDK_ver&gt;</td>
 <td>&lt;SDK_ver&gt;</td>
 <td>/system/lib[64]/vndk[-sp]-&lt;SDK_ver&gt;</td>
 </tr>
 <tr>
 <td>Prebuilt snapshot modules</td>
 <td>&lt;VNDK_ver&gt;<br>for snapshot</td>
 <td>Before or After</td>
 <td>&lt;CODE_NAME&gt;<br>or &lt;SDK_ver&gt;</td>
 <td>&lt;VNDK_ver&gt;</td>
 <td>/system/lib[64]/vndk[-sp]-&lt;VNDK_ver&gt;</td>
 </tr>
 </tbody>
 </table>

 <ul>
   <li><strong>Board Version</strong> (<code>BOARD_VNDK_VERSION</code>). VNDK
   version that vendor modules require to build. Set to <code>current</code> if
   vendor modules can link with current system modules.</li>
   <li><strong>Platform Version</strong> (<code>PLATFORM_VNDK_VERSION</code>).
   VNDK version that current system modules are building. Built only when
   <code>BOARD_VNDK_VERSION</code> equals current.</li>
   <li><strong>Version Property</strong> (<code>ro.vndk.version</code>). Property
   that specifies the VNDK version the binaries and libs in vendor.img require to
   run. Stored in the vendor.img at<code> /vendor/default.prop</code>.</li>
 </ul>

 </body>
 </html>
	<html devsite>
	<head>
	<title>Generating VNDK Snapshots</title>
	<meta name="project_path" value="/_project.yaml" />
	<meta name="book_path" value="/_book.yaml" />
	</head>
	{% include "_versions.html" %}
	<body>
	<!--
	Copyright 2018 The Android Open Source Project

	Licensed under the Apache License, Version 2.0 (the "License");
	you may not use this file except in compliance with the License.
	You may obtain a copy of the License at

	http://www.apache.org/licenses/LICENSE-2.0

	Unless required by applicable law or agreed to in writing, software
	distributed under the License is distributed on an "AS IS" BASIS,
	WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	See the License for the specific language governing permissions and
	limitations under the License.
	-->

	<p>
	A VNDK snapshot is a set of VNDK-core and VNDK-SP libs for an Android release.
	You can upgrade only the system partition if the system.img includes the
	corresponding VNDK snapshot needed by the vendor.img.
	</p>

	<aside class="note"><strong>Note:</strong> This page provides design details for
	building and updating a VNDK snapshot. For details on the background,
	definition, and use cases of VNDK snapshots, refer to
	<a href="/devices/architecture/vndk/snapshot-design">VNDK Snapshot Design</a>.
	</aside>

	<p>
	Official VNDK snapshots are built automatically on the Android build server
	and checked into <code>/prebuilts/vndk</code> of the Android source tree. For
	development purposes, you can build VNDK snapshots locally. VNDK snapshots are
	supported for arm, arm64, x86, and x86_64 TARGET_ARCH flavors.
	</p>

	<h2 id="snapshot-build-artifacts">Snapshot build artifacts</h2>

	<p>
	The Android build server generates build artifacts for VNDK snapshots using
	the following build parameters and build commands.
	</p>

	<h3 id="build-parameters">Build parameters</h3>

	<p>
	The build target name is <code>vndk</code> and the build target configuration
	is as follows:
	</p>

	<ul>
	<li>TARGET_PRODUCT=aosp_{TARGET_ARCH}_ab</li>
	<li>TARGET_BUILD_VARIANT=user</li>
	<li>TARGET_ARCH. Same as Generic System Image (GSI) target archs (arm, arm64,
	x86, x86_64).</li>
	<li>TARGET_ARCH_VARIANT. For snapshot v27 (Android 8.1), includes popular
	configurations (listed below); future releases may include other arch/cpu
	variants.</li>
	</ul>

	<table>
	<thead>
	<tr>
	<th>TARGET_PRODUCT</th>
	<th>TARGET_ARCH</th>
	<th>TARGET_ARCH_VARIANT</th>
	</tr>
	</thead>
	<tbody>
	<tr>
	<td>aosp_arm_ab</td>
	<td>arm</td>
	<td>armv7-a-neon</td>
	</tr>
	<tr>
	<td>aosp_arm64_ab</td>
	<td>arm64</td>
	<td>armv8-a</td>
	</tr>
	<tr>
	<td>aosp_x86_ab</td>
	<td>x86</td>
	<td>x86</td>
	</tr>
	<tr>
	<td>aosp_x86_64_ab</td>
	<td>x86_64</td>
	<td>x86_64</td>
	</tr>
	</tbody>
	</table>

	<h3 id="build-commands">Build commands</h3>

	<p>
	For official snapshots, Android {{ androidPVersionNumber }} includes a new
	dummy target (<code>vndk</code>) in
	<a href="https://android.googlesource.com/platform/build/+/master/core/tasks/vndk.mk">vndk.mk</a>
	that builds and outputs a VNDK snapshot to <code>$DIST_DIR</code>. The
	snapshot zip file uses the format <code>android-vndk-{TARGET_ARCH}.zip</code>.
	For example:
	</p>

	<pre class="prettyprint">
	$ lunch aosp_<ARCH>_ab-user
	$ make -j vndk dist [BOARD_VNDK_VERSION=current]
	</pre>

	<p>
	The Android build server uses the
	<a href="https://android.googlesource.com/platform/development/+/master/vndk/snapshot/build.sh">build.sh</a>
	script to build all supported arch flavors with the following command:
	</p>

	<pre class="prettyprint">
	$ DIST_DIR=%dist_dir% development/vndk/snapshot/build.sh
	</pre>

	<p>
	VNDK snapshots for an Android Version are generated from the
	<code><Android Version>-release</code> branch.
	</p>

	<h3 id="build-locally">Building locally</h3>

	<p>
	During development, you can build VNDK snapshots from a local source tree with
	the following commands:
	</p>

	<ul>
	<li>To build all supported archs at once, execute the build script
	(<code>build.sh</code>):
	<pre class="prettyprint">
	$ cd $ANDROID_BUILD_TOP
	$ development/vndk/snapshot/build.sh
	</pre>
	</li>
	<li>To build one specific TARGET_ARCH:

	<pre class="prettyprint">
	$ lunch aosp_<ARCH>_ab-user
	$ m -j vndk dist
	</pre>
	</li>
	</ul>

	<p>
	The corresponding <code>android-vndk-<ARCH>.zip</code> file is created
	under <code>$DIST_DIR</code>.
	</p>

	<h2 id="snapshot-files">Snapshot files</h2>

	<p>
	A VNDK snapshot includes the following files:
	</p>

	<ul>
	<li>Vendor variant of VNDK-core and VNDK-SP shared libraries.
	<ul>
	<li>LL-NDK shared libs are not needed as they are backward compatible.</li>
	<li>For 64bit targets, both TARGET_ARCH and TARGET_2ND_ARCH libraries are
	built and included.</li>
	</ul>
	</li>
	<li>List of VNDK-core, VNDK-SP, LL-NDK, and VNDK-private libraries is at
	<code>[vndkcore\|vndksp\|llndk\|vndkprivate].libraries.txt</code>.</li>
	<li>Linker config file is <code>ld.config.txt</code>.</li>
	<li>License files. </li>
	<li><code>module_paths.txt</code>. Records the module paths for all VNDK
	libraries, which is needed for checking that GPL projects have sources
	released in a given Android source tree.</li>
	</ul>

	<p>
	For a given VNDK snapshot zip file,
	<code>android-vndk-{TARGET_ARCH}.zip</code>, the VNDK prebuilt libraries are
	grouped in separate directories named
	<code>arch-{TARGET_ARCH}-{TARGET_ARCH_VARIANT}</code> according to ABI
	bitness. For example, for <code>android-vndk-arm64.zip</code>, the 64-bit libs
	are placed under <code>arch-arm64-armv8-a</code> and the 32-bit libs are
	placed under <code>arch-arm-armv8-a</code>.
	</p>

	<h3 id="example-snapshot-dir-structure">Example: VNDK snapshot directory
	structure</h3>

	<p>
	The example below shows the directory structure for an arm64
	(<code>TARGET_ARCH=arm64</code>) VNDK snapshot zip file
	(<code>android-vndk-arm64.zip</code>).
	</p>

	<img src="/devices/architecture/images/vndk_snapshot_directory.png">
	<figcaption><strong>Figure 1. </strong>VNDK snapshot directory structure
	(example)</figcaption>

	<h2 id='upload-vndk-snapshots'>Uploading VNDK snapshots</h2>

	<p>
	VNDK snapshots are checked in the source tree under
	<code>/prebuilts/vndk/v<VER></code>, where <code><VER></code> is
	equal to the version of the VNDK snapshot (which follows the SDK version of
	the corresponding Android release). For example, the O MR1 VNDK snapshot has
	version 27.
	</p>

	<h3 id="using-update-py">Using the update.py script</h3>

	<p>
	The <code>update.py</code> script
	(<code>/development/vndk/snapshot/update.py)</code> automates the process of
	adding a pre-built VNDK snapshot to the source tree. This script performs the
	following tasks:
	</p>

	<ol>
	<li>In <code>/prebuilts/vndk/v<VER></code>, uses <code>repo start</code>
	to create new git branch.</li>
	<li>Fetches and unzips VNDK snapshot build artifacts.</li>
	<li>Runs <code>gen_buildfiles.py</code> to auto generate the build files
	(<code>Android.mk</code>, <code>Android.bp</code>).</li>
	<li>Runs <code>check_gpl_license.py</code> to verify the prebuilt libraries
	licensed under the General Public License (GPL) have sources released in
	current source tree.</li>
	<li>Uses <code>git commit</code> to commit new changes.</li>
	</ol>

	<h3 id="using-local-snapshots">Using locally-built VNDK snapshots</h3>

	<p>
	During development, you can use locally-built VNDK snapshots for testing. When
	the <code>--local</code> option is specified, <code>update.py</code> fetches
	VNDK snapshot build artifacts from local <code>$DIST_DIR</code> instead of the
	Android build server. Usage:
	</p>

	<pre class="prettyprint">
	$ python update.py <VER> --local
	</pre>

	<p>
	For example, to update the O MR1 VNDK snapshot with local build artifacts,
	run:
	</p>

	<pre class="prettyprint">
	$ python update.py 27 --local
	</pre>

	<p>
	Because local mode is designed for testing only, the script skips the GPL
	license checking and git commit steps.
	</p>

	<h3 id="dir-structure-prebuilts">Directory structure for prebuilts/vndk</h3>

	<img src="/devices/architecture/images/vndk_snapshot_prebuilt.png">
	<figcaption><strong>Figure 2. </strong>Prebuilts/vndk directory
	structure</figcaption>

	<h2 id="install-vndk-snapshot">Installing VNDK snapshots</h2>

	<p>
	The system image installs VNDK snapshot libraries at build time using the
	information in <code>BOARD_VNDK_VERSION</code>,
	<code>PRODUCT_EXTRA_VNDK_VERSIONS</code>, and <code>ro.vndk.version</code>.
	You can control which VNDK snapshots get installed from
	<code>/prebuilts/vndk/v<VER></code> using one of the following options:
	</p>

	<ul>
	<li><strong>Option 1:</strong> <code>BOARD_VNDK_VERSION</code>. Use the
	snapshot modules for building the current vendor modules and install only the
	snapshot modules that are required for the vendor modules.</li>
	<li><strong>Option 2:</strong> <code>PRODUCT_EXTRA_VNDK_VERSIONS</code>.
	Install the VNDK snapshot modules regardless of the current vendor modules.
	This installs the prebuilt VNDK snapshots listed in
	<code>PRODUCT_EXTRA_VNDK_VERSIONS</code> without linking them to any other
	modules at build time.</li>
	</ul>

	<h3 id="set-board-vndk">Setting BOARD_VNDK_VERSION</h3>

	<p>
	<code>BOARD_VNDK_VERSION</code> shows the VNDK version that current vendor
	modules are required to build. If <code>BOARD_VNDK_VERSION</code> has an
	available VNDK snapshot version in <code>/prebuilts/vndk</code> directory, the
	VNDK snapshot indicated in <code>BOARD_VNDK_VERSION</code> is installed. If
	the VNDK snapshot is not available in the directory, a build error occurs.
	</p>

	<p>
	Defining <code>BOARD_VNDK_VERSION</code> also enables the VNDK modules to be
	installed. Vendor modules link with the VNDK snapshot version defined in
	<code>BOARD_VNDK_VERSION</code> at build time (this does not build current
	VNDK modules in the system source). When downloading the full source tree from
	a repository, both system and vendor sources are based on the same Android
	release.
	</p>

	<aside class="note"><strong>Note:</strong> Vendor modules use the current VNDK
	version of the system source tree, so you must set
	<code>BOARD_VNDK_VERSION</code> to <code>current</code>.
	</aside>

	<h3 id="set-product-extra">Setting PRODUCT_EXTRA_VNDK_VERSIONS</h3>

	<p>
	<code>PRODUCT_EXTRA_VNDK_VERSIONS</code> lists the extra VNDK versions to be
	installed. Normally it is enough to have one VNDK snapshot for the current
	vendor partition. However, in some cases you might need to include multiple
	snapshots in one system image. For example, Generic System Image (GSI) has
	multiple snapshots to support multiple vendor versions with one system image.
	By setting <code>PRODUCT_EXTRA_VNDK_VERSIONS</code>, you can install the VNDK
	snapshot modules in addition to the VNDK version in
	<code>BOARD_VNDK_VERSION</code>.
	</p>

	<p>
	If <code>PRODUCT_EXTRA_VNDK_VERSIONS</code> has a specific list of versions,
	the build system looks for pre-built snapshots of the version list in the
	<code>prebuilts/vndk</code> directory. If the build system locates all listed
	snapshots, it installs those snapshot files to each
	<code>out/target/product/<board>/system/lib[64]/vndk[-sp]-${VER}</code>.
	Missing versions generate a build error.
	</p>

	<p>
	The VNDK modules will not link with the vendor modules at build time but may
	be used at runtime if the vendor modules in vendor partition require one of
	the installed VNDK versions. <code>PRODUCT_EXTRA_VNDK_VERSIONS</code> is valid
	only if <code>BOARD_VNDK_VERSION</code> is defined. For example, to install
	the O MR1 VNDK snapshot to system.img:
	</p>

	<pre class="prettyprint">
	$ m -j PRODUCT_EXTRA_VNDK_VERSIONS=27
	</pre>

	<h3 id="platform-vndk">PLATFORM_VNDK_VERSION</h3>

	<p>
	<code>PLATFORM_VNDK_VERSION</code> defines the VNDK version for current VNDK
	modules in the system source. The value is set automatically:
	</p>

	<ul>
	<li>Prior to release, the <code>PLATFORM_VNDK_VERSION</code> is set as
	<code>PLATFORM_VERSION_CODENAME</code>.</li>
	<li>At release, <code>PLATFORM_SDK_VERSION</code> is copied to
	<code>PLATFORM_VNDK_VERSION</code>.</li>
	</ul>

	<p>
	After the Android version is released, the current VNDK libraries are
	installed to <code>/system/lib[64]/vndk-$SDK_VER</code> and
	<code>/system/lib[64]/vndk-sp-$SDK_VER</code>, where <code>$SDK_VER</code> is
	the version stored in <code>PLATFORM_VNDK_VERSION</code>.
	</p>

	<h3 id="namespace-config">Namespace configuration</h3>

	<p>
	The vendor modules search the required shared libraries using the namespace
	configuration in <code>/etc/ld.config.${VER}.txt</code> (where
	<code>${VER}</code> is obtained from the <code>ro.vndk.version</code>
	property). The namespace configuration has a versioned VNDK directory that
	uses the following syntax:
	</p>

	<ul>
	<li><code>/system/${LIB}/vndk-%VNDK_VER%</code></li>
	<li><code>/system/${LIB}/vndk-sp-%VNDK_VER%</code></li>
	</ul>

	<p>
	<code>%VNDK_VER%</code> is replaced with <code>PLATFORM_VNDK_VERSION</code>
	at build time, enabling a system image to provide multiple snapshots for each
	VNDK version.
	</p>

	<p>
	When <code>BOARD_VNDK_VERSION</code> is set to <code>current</code>, the
	<code>PLATFORM_VNDK_VERSION</code> is stored in <code>ro.vndk.version</code>,
	otherwise <code>BOARD_VNDK_VERSION </code>is stored in
	<code>ro.vndk.version</code>. <code>PLATFORM_VNDK_VERSION</code> is set to the
	SDK version when Android releases; prior to release, the alphanumeric Android
	code name is used for <code>PLATFORM_VNDK_VERSION</code>.
	</p>

	<h3 id="summary-vndk-version-settings">Summary of VNDK version settings</h3>

	<p>
	The table below summarizes the VNDK version settings.
	</p>

	<table>
	<thead>
	<tr>
	<th width="15%">Vendor<br>Build</th>
	<th>Board<br>Version</th>
	<th>SDK<br>Release</th>
	<th>Platform<br>Version</th>
	<th>Version<br>Property</th>
	<th>Install Directory</th>
	</tr>
	</thead>
	<tbody>
	<tr>
	<td rowspan=2>Current VNDK modules</td>
	<td rowspan=2><code>current</code></td>
	<td>Before</td>
	<td><CODE_NAME></td>
	<td><CODE_NAME></td>
	<td>/system/lib[64]/vndk[-sp]-<CODE_NAME></td>
	</tr>
	<tr>
	<td>After</td>
	<td><SDK_ver></td>
	<td><SDK_ver></td>
	<td>/system/lib[64]/vndk[-sp]-<SDK_ver></td>
	</tr>
	<tr>
	<td>Prebuilt snapshot modules</td>
	<td><VNDK_ver><br>for snapshot</td>
	<td>Before or After</td>
	<td><CODE_NAME><br>or <SDK_ver></td>
	<td><VNDK_ver></td>
	<td>/system/lib[64]/vndk[-sp]-<VNDK_ver></td>
	</tr>
	</tbody>
	</table>

	<ul>
	<li><strong>Board Version</strong> (<code>BOARD_VNDK_VERSION</code>). VNDK
	version that vendor modules require to build. Set to <code>current</code> if
	vendor modules can link with current system modules.</li>
	<li><strong>Platform Version</strong> (<code>PLATFORM_VNDK_VERSION</code>).
	VNDK version that current system modules are building. Built only when
	<code>BOARD_VNDK_VERSION</code> equals current.</li>
	<li><strong>Version Property</strong> (<code>ro.vndk.version</code>). Property
	that specifies the VNDK version the binaries and libs in vendor.img require to
	run. Stored in the vendor.img at<code> /vendor/default.prop</code>.</li>
	</ul>

	</body>
	</html>