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PiperOrigin-RevId: 202498507
Change-Id: I3cf1b347a519ecff7960a159cdc57b35306435cf

1 files changed, 163 insertions, 45 deletions

diff --git a/en/devices/architecture/index.html b/en/devices/architecture/index.html
index 592198ff..da16afb1 100644
--- a/en/devices/architecture/index.html
+++ b/en/devices/architecture/index.html
@@ -28,54 +28,172 @@ Android system architecture contains the following components:
 </p>
 
 <img src="../images/ape_fwk_all.png">
+<figcaption><strong>Figure 1.</strong> Android system architecture</figcaption>
+
+<ul>
+<li>
+    <strong>Application framework</strong>. The application framework is used
+    most often by application developers. As a hardware developer, you should be
+    aware of developer APIs as many map directly to the underlying HAL
+    interfaces and can provide helpful information about implementing drivers.
+</li>
+<li>
+    <strong>Binder IPC</strong>. The Binder Inter-Process Communication (IPC)
+    mechanism allows the application framework to cross process boundaries and
+    call into the Android system services code. This enables high level
+    framework APIs to interact with Android system services. At the application
+    framework level, this communication is hidden from the developer and things
+    appear to "just work".
+</li>
+<li>
+    <strong>System services</strong>. System services are modular, focused
+    components such as Window Manager, Search Service, or Notification Manager.
+    Functionality exposed by application framework APIs communicates with system
+    services to access the underlying hardware. Android includes two groups of
+    services: <em>system</em> (such as Window Manager and Notification Manager)
+    and <em>media</em> (services involved in playing and recording media).
+</li>
+<li>
+    <strong>Hardware abstraction layer (HAL)</strong>. A HAL defines a standard
+    interface for hardware vendors to implement, which enables Android to be
+    agnostic about lower-level driver implementations. Using a HAL allows you to
+    implement functionality without affecting or modifying the higher level
+    system. HAL implementations are packaged into modules and loaded by the
+    Android system at the appropriate time. For details, see
+    <a href="/devices/architecture/hal.html">Hardware Abstraction Layer
+    (HAL)</a>.
+</li>
+<li>
+    <strong>Linux kernel</strong>. Developing your device drivers is similar to
+    developing a typical Linux device driver. Android uses a version of the
+    Linux kernel with a few special additions such as Low Memory Killer (a
+    memory management system that is more aggressive in preserving memory), wake
+    locks (a
+    <a href="https://developer.android.com/reference/android/os/PowerManager.html" class="external"><code>PowerManager</code></a>
+    system service), the Binder IPC driver, and other features important for a
+    mobile embedded platform. These additions are primarily for system
+    functionality and do not affect driver development. You can use any version
+    of the kernel as long as it supports the required features (such as the
+    binder driver). However, we recommend using the latest version of the
+    Android kernel. For details, see
+    <a href="/setup/building-kernels.html">Building Kernels</a>.
+</li>
+</ul>
+
+<h2 id="hidl">HAL interface definition language (HIDL)</h2>
 
-<p class="img-caption"><strong>Figure 1.</strong> Android system architecture</p>
-
-<h2 id="application-framework">Application framework</h2>
-
-<p>The application framework is used most often by application developers. As a
-hardware developer, you should be aware of developer APIs as many map directly
-to the underlying HAL interfaces and can provide helpful information about
-implementing drivers.</p>
-
-<h2 id="binder-ipc">Binder IPC</h2>
-<p>The Binder Inter-Process Communication (IPC) mechanism allows the application
-framework to cross process boundaries and call into the Android system services
-code. This enables high level framework APIs to interact with Android system
-services. At the application framework level, this communication is hidden from
-the developer and things appear to "just work".</p>
-
-<h2 id="system-services">System services</h2>
-<p>System services are modular, focused components such as Window Manager,
-Search Service, or Notification Manager. Functionality exposed by application
-framework APIs communicates with system services to access the underlying
-hardware. Android includes two groups of services: <em>system</em> (such as
-Window Manager and Notification Manager) and <em>media</em> (services involved
-in playing and recording media).</p>
-
-<h2 id="hal">Hardware abstraction layer (HAL)</h2>
-<p>A HAL defines a standard interface for hardware vendors to implement,
-which enables Android to be agnostic about lower-level driver implementations.
-Using a HAL allows you to implement functionality without affecting or modifying
-the higher level system. HAL implementations are packaged into modules and
-loaded by the Android system at the appropriate time. For details, see
-<a href="/devices/architecture/hal.html">Hardware Abstraction Layer (HAL)</a>.
+<p>
+    Android 8.0 re-architected the Android OS framework (in a project known as
+    <em>Treble</em>) to make it easier, faster, and less costly for
+    manufacturers to update devices to a new version of Android. In this new
+    architecture, the HAL interface definition language (HIDL, pronounced
+    "hide-l") specifies the interface between a HAL and its users, enabling the
+    Android framework to be replaced without rebuilding the HALs.
+</p>
+
+<aside class="note">
+    <strong>Note:</strong> For more details on Project Treble, refer to the
+    developer blog posts
+    <a href="https://android-developers.googleblog.com/2017/05/here-comes-treble-modular-base-for.html" class="external">Here
+    comes Treble: A modular base for Android</a> and
+    <a href="https://android-developers.googleblog.com/2018/05/faster-adoption-with-project-treble.html" class="external">Faster
+    Adoption with Project Treble</a>.
+</aside>
+
+<p>
+    HIDL separates the vendor implementation (device-specific, lower-level
+    software written by silicon manufacturers) from the Android OS framework via
+    a new vendor interface. Vendors or SOC makers build HALs once and place them
+    in a <code>/vendor</code> partition on the device; the framework, in its own
+    partition, can then be replaced with an
+    <a href="/devices/tech/ota/">over-the-air (OTA) update</a> without
+    recompiling the HALs.
+</p>
+<p>
+    The difference between the legacy Android architecture and the current,
+    HIDL-based architecture is in the use of the vendor interface:
+</p>
+
+<ul>
+<li>
+    In Android 7.x and earlier, no formal vendor interface exists, so device
+    makers must update large portions of the Android code to move a device to a
+    newer version of Android:<br><br>
+
+<img src="images/treble_blog_before.png">
+<figcaption><strong>Figure 2.</strong> Legacy Android update
+environment</figcaption>
+</li>
+<li>
+    In Android 8.0 and higher, a new stable vendor interface provides access to
+    the hardware-specific parts of Android, so device makers can deliver
+    new Android releases simply by updating the Android OS
+    framework&mdash;without additional work required from the silicon
+    manufacturers:<br><br>
+
+<img src="images/treble_blog_after.png">
+<figcaption><strong>Figure 3.</strong> Current Android update
+environment</figcaption>
+</li>
+</ul>
+
+<p>
+    All new devices launching with Android 8.0 and higher can take advantage of
+    the new architecture. To ensure forward compatibility of vendor
+    implementations, the vendor interface is validated by the
+    <a href="/devices/tech/vts/index.html">Vendor Test Suite (VTS)</a>, which is
+    analogous to the <a href="/compatibility/cts/">Compatibility Test Suite
+    (CTS)</a>. You can use VTS to automate HAL and OS kernel testing in both
+    legacy and current Android architectures.
+</p>
+
+<h2 id="resources">Architecture resources</h2>
+
+<p>
+    For details on the Android architecture, see the following sections:
 </p>
 
-<h2 id="Linux-kernel">Linux kernel</h2>
-<p>Developing your device drivers is similar to developing a typical Linux
-device driver. Android uses a version of the Linux kernel with a few special
-additions such as Low Memory Killer (a memory management system that is more
-aggressive in preserving memory), wake locks (a
-<a href="https://developer.android.com/reference/android/os/PowerManager.html">
-<code>PowerManager</code></a> system service), the Binder IPC driver, and
-other features important for a mobile embedded platform. These additions are
-primarily for system functionality and do not affect driver development.</p>
-
-<p>You can use any version of the kernel as long as it supports the required
-features (such as the binder driver). However, we recommend using the latest
-version of the Android kernel. For details, see
-<a href="/setup/building-kernels.html">Building Kernels</a>.</p>
+<ul>
+<li>
+    <a href="/devices/architecture/hal-types.html">HAL Types</a>. Describes
+    binderized, passthrough, Same-Process (SP), and legacy HALs.
+</li>
+<li>
+    <a href="/devices/architecture/hidl/index.html">HIDL (General)</a>. Contains
+    general information about the interface between a HAL and its users.
+</li>
+<li>
+    <a href="/devices/architecture/hidl-cpp/index.html">HIDL (C++)</a>. Contains
+    details for creating C++ implementations of HIDL interfaces.
+</li>
+<li>
+    <a href="/devices/architecture/hidl-java/index.html">HIDL (Java)</a>.
+    Contains details about the Java frontend for HIDL interfaces.
+</li>
+<li>
+    <a href="/devices/architecture/configstore/index.html">ConfigStore HAL</a>.
+    Describes APIs for accessing read-only configuration items used to configure
+    the Android framework.
+</li>
+<li>
+    <a href="/devices/architecture/dto/index.html">Device Tree Overlays</a>.
+    Provides details on using device tree overlays (DTOs) in Android.
+</li>
+<li>
+    <a href="/devices/architecture/vndk/index.html">Vendor Native Development
+    Kit (VNDK)</a>. Describes the set of vendor-exclusive libraries for
+    implementing vendor HALs.
+</li>
+<li>
+    <a href="/devices/architecture/vintf/index.html">Vendor Interface Object
+    (VINTF)</a>. Describes the objects that aggregate relevant information about
+    a device and make that information available through a queryable API.
+</li>
+<li>
+    <a href="/security/selinux/images/SELinux_Treble.pdf">SELinux for Android
+    8.0</a>. Details SELinux changes and customizations.
+</li>
+</ul>
 
   </body>
 </html>