en/devices/automotive/index.html - platform/docs/source.android.com - Git at Google

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 <img style="float: right; margin: 0px 15px 15px 15px;"
 src="../images/ape_fwk_hal_vehicle.png" alt="Android vehicle HAL icon"/>

 <p>Many car subsystems interconnect with each other and the in-vehicle
 infotainment (IVI) system via various bus topologies. The exact bus type and
 protocols vary widely between manufacturers (and even between different vehicle
 models of the same brand); examples include Controller Area Network (CAN) bus,
 Local Interconnect Network (LIN) bus, Media Oriented Systems Transport (MOST),
 as well as automotive-grade Ethernet and TCP/IP networks such as BroadR-Reach.
 </p>
 <p>the Android Automotive hardware abstraction layer (HAL) provides a
 consistent interface to the Android framework regardless of physical transport
 layer. This vehicle HAL is the interface for developing Android Automotive
 implementations.</p>
 <p>System integrators can implement a vehicle HAL module by connecting
 function-specific platform HAL interfaces (e.g. HVAC) with technology-specific
 network interfaces (e.g. CAN bus). Typical implementations may include a
 dedicated Microcontroller Unit (MCU) running a proprietary real-time operating
 system (RTOS) for CAN bus access or similar, which may be connected via a serial
 link to the CPU running Android Automotive. Instead of a dedicated MCU, it may
 also be possible to implement the bus access as a virtualized CPU. It is up to
 each partner to choose the architecture suitable for the hardware as long as the
 implementation fulfills the interface requirements for the vehicle HAL.</p>

 <h2 id=arch>Architecture</h2>
 <p>The vehicle HAL is the interface definition between the car and the vehicle
 network service:</p>

 <img src="../images/vehicle_hal_arch.png" alt="Android vehicle HAL architecture">
 <p class="img-caption"><strong>Figure 1</strong>. Vehicle HAL and Android
 automotive architecture</p>

 <ul>
 <li><strong>Car API</strong>. Contains the APIs such as CarHvacManager,
 CarSensorManager, and CarCameraManager. For details on supported APIs,
 refer to <code>/platform/packages/services/Car/car-lib</code>.</li>
 <li><strong>CarService</strong>. Located at
 <code>/platform/packages/services/Car/</code>.</li>
 <li><strong>VehicleNetworkService</strong>. Controls vehicle HAL with built-in
 security. Access restricted to system components only (non-system components
 such as third party apps should use car API instead). OEMs can control access
 using <code>vns_policy.xml</code> and <code>vendor_vns_policy.xml</code>.
 Located at <code>/platform/packages/services/Car/vehicle_network_service/</code>;
 for libraries to access the vehicle network, refer to
 <code>/platform/packages/services/Car/libvehiclenetwork/</code>.</li>
 <li><strong>Vehicle HAL</strong>. Interface that defines the vehicle properties
 OEMs can implement. Contains property metadata (for example, whether the vehicle
 property is an int and which change modes are allowed). Located at
 <code>hardware/libhardware/include/hardware/vehicle.h</code>. For a basic
 reference implementation, refer to
 <code>hardware/libhardware/modules/vehicle/</code>.</li>
 </ul>
 <p>For more details, see <a href="/devices/automotive/properties.html">Vehicle
 Properties</a>.

 <h2 id=security>Security</h2>
 <p>The vehicle HAL supports three levels of security for accessing data:</p>
 <ul>
 <li>System only (controlled by <code>vns_policy.xml</code>)</li>
 <li>Accessible to app with permission (through car service)</li>
 <li>Accessible without permission (through car service)</li>
 </ul>
 <p>Direct access to vehicle properties is allowed only to selected system
 components with vehicle network service acting as the gatekeeper. Most
 applications go through additional gatekeeping by car service (for example, only
 system applications can control HVAC as it requires system permission granted
 only to system apps).</p>

 <h2 id=validation>Validation</h2>
 <p>AOSP includes the following testing resources for use in development:</p>
 <ul>
 <li><code>hardware/libhardware/tests/vehicle/vehicle-hal-tool.c</code><br>
 Command-line native tool to load vehicle HAL and do simple operations. Useful
 for getting the system up and running in the early stages of development.</li>
 <li><code>packages/services/Car/tests/carservice_test/</code><br>Contains car
 service testing with mocked vehicle HAL properties. For each property, expected
 behavior is implemented in the test. This can be a good starting point to
 understand expected behavior.</li>
 <li><code>hardware/libhardware/modules/vehicle/</code><br>A basic reference
 implementation.</li>
 </ul>

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	<html devsite>
	<head>
	<title>Automotive</title>
	<meta name="project_path" value="/_project.yaml" />
	<meta name="book_path" value="/_book.yaml" />
	</head>
	<body>
	<!--
	Copyright 2017 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.
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	<img style="float: right; margin: 0px 15px 15px 15px;"
	src="../images/ape_fwk_hal_vehicle.png" alt="Android vehicle HAL icon"/>

	<p>Many car subsystems interconnect with each other and the in-vehicle
	infotainment (IVI) system via various bus topologies. The exact bus type and
	protocols vary widely between manufacturers (and even between different vehicle
	models of the same brand); examples include Controller Area Network (CAN) bus,
	Local Interconnect Network (LIN) bus, Media Oriented Systems Transport (MOST),
	as well as automotive-grade Ethernet and TCP/IP networks such as BroadR-Reach.
	</p>
	<p>the Android Automotive hardware abstraction layer (HAL) provides a
	consistent interface to the Android framework regardless of physical transport
	layer. This vehicle HAL is the interface for developing Android Automotive
	implementations.</p>
	<p>System integrators can implement a vehicle HAL module by connecting
	function-specific platform HAL interfaces (e.g. HVAC) with technology-specific
	network interfaces (e.g. CAN bus). Typical implementations may include a
	dedicated Microcontroller Unit (MCU) running a proprietary real-time operating
	system (RTOS) for CAN bus access or similar, which may be connected via a serial
	link to the CPU running Android Automotive. Instead of a dedicated MCU, it may
	also be possible to implement the bus access as a virtualized CPU. It is up to
	each partner to choose the architecture suitable for the hardware as long as the
	implementation fulfills the interface requirements for the vehicle HAL.</p>

	<h2 id=arch>Architecture</h2>
	<p>The vehicle HAL is the interface definition between the car and the vehicle
	network service:</p>

	<img src="../images/vehicle_hal_arch.png" alt="Android vehicle HAL architecture">
	<p class="img-caption"><strong>Figure 1</strong>. Vehicle HAL and Android
	automotive architecture</p>

	<ul>
	<li><strong>Car API</strong>. Contains the APIs such as CarHvacManager,
	CarSensorManager, and CarCameraManager. For details on supported APIs,
	refer to <code>/platform/packages/services/Car/car-lib</code>.</li>
	<li><strong>CarService</strong>. Located at
	<code>/platform/packages/services/Car/</code>.</li>
	<li><strong>VehicleNetworkService</strong>. Controls vehicle HAL with built-in
	security. Access restricted to system components only (non-system components
	such as third party apps should use car API instead). OEMs can control access
	using <code>vns_policy.xml</code> and <code>vendor_vns_policy.xml</code>.
	Located at <code>/platform/packages/services/Car/vehicle_network_service/</code>;
	for libraries to access the vehicle network, refer to
	<code>/platform/packages/services/Car/libvehiclenetwork/</code>.</li>
	<li><strong>Vehicle HAL</strong>. Interface that defines the vehicle properties
	OEMs can implement. Contains property metadata (for example, whether the vehicle
	property is an int and which change modes are allowed). Located at
	<code>hardware/libhardware/include/hardware/vehicle.h</code>. For a basic
	reference implementation, refer to
	<code>hardware/libhardware/modules/vehicle/</code>.</li>
	</ul>
	<p>For more details, see <a href="/devices/automotive/properties.html">Vehicle
	Properties</a>.

	<h2 id=security>Security</h2>
	<p>The vehicle HAL supports three levels of security for accessing data:</p>
	<ul>
	<li>System only (controlled by <code>vns_policy.xml</code>)</li>
	<li>Accessible to app with permission (through car service)</li>
	<li>Accessible without permission (through car service)</li>
	</ul>
	<p>Direct access to vehicle properties is allowed only to selected system
	components with vehicle network service acting as the gatekeeper. Most
	applications go through additional gatekeeping by car service (for example, only
	system applications can control HVAC as it requires system permission granted
	only to system apps).</p>

	<h2 id=validation>Validation</h2>
	<p>AOSP includes the following testing resources for use in development:</p>
	<ul>
	<li><code>hardware/libhardware/tests/vehicle/vehicle-hal-tool.c</code><br>
	Command-line native tool to load vehicle HAL and do simple operations. Useful
	for getting the system up and running in the early stages of development.</li>
	<li><code>packages/services/Car/tests/carservice_test/</code><br>Contains car
	service testing with mocked vehicle HAL properties. For each property, expected
	behavior is implemented in the test. This can be a good starting point to
	understand expected behavior.</li>
	<li><code>hardware/libhardware/modules/vehicle/</code><br>A basic reference
	implementation.</li>
	</ul>

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