Reference platform

Through a new product named trout, Android Automotive (AAOS) now provides support for deployment as a guest virtual machine (VM) in environments compatible with the VirtIO standard. trout is based on the Cuttlefish virtual reference platform and is available as the trout device configuration. The userspace source code can be found at device/google/trout. The table below describes the technology used to virtualize each of the subsystems in trout.

Feature Technology
Audio Control HAL vsock/gRPC
Audio HAL virtio-snd
Bluetooth virtio-console
Dumpstate HAL vsock/gRPC
Extended View System (EVS) virtio-video
Garage mode vsock/gRPC
Graphics virtio-gpu
Global navigation satellite system (GNSS) virtio-console
Sensor HAL 2.0 virtio-scmi and IIO
Touchscreen input virtio-input
Vehicle HAL vsock/gRPC

Extend trout

trout can be used as a starting point to create new In-Vehicle Infotainment (IVI) Android targets. The build infrastructure is designed to be extended and customized. For example:

# Inherit trout-arm64 default values and settings
$(call inherit-product, device/google/trout/aosp_trout_arm64.mk)

# Customize HALs as needed
LOCAL_VHAL_PRODUCT_PACKAGE := vendor.oem.vhal@2.0-service
LOCAL_AUDIO_PRODUCT_PACKAGE := vendor.oem.audio@6.0-impl

# Configure SELinux policy
BOARD_SEPOLICY_DIRS += device/oem/car/sepolicy/vendor/oem

# Configure properties
LOCAL_DUMPSTATE_PROPERTIES := \
    ro.vendor.dumpstate.server.cid=22 \
    ro.vendor.dumpstate.server.port=406 \
    ro.vendor.helpersystem.log_loc=/data/dumpstate

[... and more as needed ...]

Several Android HALs can be individually replaced with custom implementations, or the default implementations maintained but certain configuration parameters adjusted to establish proper inter-VM communication in the target environment. These HALs (including Vehicle HAL, Audio Control HAL, and Dumpstate HAL) are implemented by means of a gRPC interface backed by a vsock connection between the AAOS guest and a host system providing the underlying feature implementation. These must be configured by means of supplying the proper vsock connection parameters as vendor properties. The source code acts as the ultimate ground truth on which properties are available for configuration and their semantics.

Build trout

Compile the userspace

To compile the userspace:

  1. Download the Android source tree: 
    repo init -u https://android.googlesource.com/platform/manifest -b main
repo sync -j8
  2. Build the environment: 
    source build/envsetup.sh
lunch aosp_trout_arm64-userdebug
make -j24

Build the kernel

For trout 1.1, the kernel codebase is provided in AOSP. The trout kernel is composed of the same code as the upstream ACK 5.10, with the addition of trout-specific modules for VirtIO subsystems.

  1. To clone the kernel, run: 
    repo init https://android.googlesource.com/kernel/manifest -b trout-android12-5.10 && repo sync
  2. To build the kernel run: 
    BUILD_CONFIG=common-modules/virtual-device/build.config.trout.coqos build/build.sh

Your hypervisor supplier might have a different kernel configuration required or additional modules that need to be compiled. Be sure to follow this specific guidance, if provided.

Compliance

When AAOS runs as a guest VM, our goal is to be a compatible Android deployment from the framework perspective. Host side issues are the purview of each implementation and outside the scope of trout 1.1.

We haven't performed additional xTS validation on trout 1.1. Continue to refer to the below discussion of CTS support in trout 1.0.

In trout 1.0, several CTS issues remain. The following CTS modules are known to include test failures:

CtsStagedInstallHostTestCases
CtsRollbackManagerHostTestCases
CtsVideoTestCases
CtsHostsideNetworkTests
CtsActivityManagerBackgroundActivityTestCases
CtsAdbHostTestCases
CtsNativeHardwareTestCases
CtsContentTestCases
CtsCarHostTestCases
CtsOsTestCases
CtsStatsdHostTestCases
CtsVoiceInteractionTestCases
CtsViewTestCases
CtsCameraTestCases
CtsLocationGnssTestCases
CtsGraphicsTestCases
CtsIncidentHostTestCases
CtsInstallHostTestCases
CtsNativeVerifiedBootTestCases
CtsNetTestCases 		CtsWindowManagerDeviceTestCases
CtsMediaStressTestCases
CtsAppTestCases
CtsUsbTests
CtsAutoFillServiceTestCases
CtsDisplayTestCases
CtsMediaTestCases
CtsDeqpTestCases
CtsDumpsysHostTestCases
CtsOpenGLTestCasesCtsLibcoreTestCases
CtsSecurityHostTestCases
CtsInputMethodTestCases
CtsStatsdAtomHostTestCases
CtsPermission4TestCases
CtsNNAPIBenchmarkTestCases
CtsSimpleperfTestCases
CtsAccessibilityTestCases
CtsAppSecurityHostTestCases
CtsKeystoreTestCases

The following CTS-V areas are known to include test failures:

Car Launcher test
Bluetooth Low Energy (BLE) Advertiser test
Streaming Video Quality Verifier
Bluetooth HID Device test
Hifi Ultrasound Microphone test
Hifi Ultrasound Speaker test 		Unlocked Device Required test
Dynamic Sensor Discovery test
Off Body Sensor test
Significant Motion test
Audio Output Routing Notification test
Network Request or Suggestion test

Release notes

trout 1.1 contains the following known issues:

  • User builds of trout aren't available. The system is built as -userdebug, which can affect some CTS tests.
  • Android Verified Boot (AVB) isn't supported.
  • Some Android subsystems might be unavailable, including secure world and NNHAL.
  • Guest network access is generally provided by means of a virtualized Wi-Fi adapter and a virtio-net tunnel. Host-side connectivity depends on your specific hypervisor deployment.
  • Some implementations might offer limited or no Bluetooth capability.
  • A VHAL event injection might not work for some sensors.
  • Some heavy workloads can cause audio playback glitches.
  • In some implementations, adb reboot of the AAOS guest might reboot the entire system.
  • STS can cause system instability and require a reboot.

For additional details, refer to the partner release notes for your specific deployment of trout.