By default, most car services are mandatory and are always enabled. However, you can designate a subset of car services to be optional because some features might not be supported in every car.
List of optional features
The optional car control features you can enable and disable are listed in the table below.
| Car control feature | String value |
|---|---|
| Car EVS service | car_evs_service |
| Car experimental keyguard service | experimental_car_keyguard_service |
| Car navigation service | car_navigation_service |
| Car occupant connection service | car_occupant_connection_service |
| Car remote access service | car_remote_access_service |
| Car remote device service | car_remote_device_service |
| Car telemetry service | car_telemetry_service |
| Car user notice service | com.android.car.user.CarUserNoticeService |
| Cluster home service | cluster_home_service |
| Diagnostic service | diagnostic |
| Occupant awareness wervice | occupant_awareness |
| Storage monitoring service | storage_monitoring |
| Vehicle map service | vehicle_map_service |
Enable and disable car control features
You can control support for features in your builds in one of two ways, either with runtime resource overlays (RROs) or through the Vehicle Hardware Abstraction Layer (VHAL).
Use RROs
Use the resource configuration named config_allowed_optional_car_features, which
lists all the optional features you can enable. When a car is first booted up, possible
optional car features are noted and are enabled if they're not blocklisted by the VHAL.
To learn more RROs, see
Change the value of an app's resources at runtime.
Use the VHAL
The Vehicle Hardware Abstraction Layer (VHAL) controls features by serving as a
blocklist to disable specific optional features. The VHAL property named
DISABLED_OPTIONAL_FEATURES lists the optional features in the overlay that
are to be disabled. If this property doesn't exist, then the list of optional features from
the RROs are all enabled. To learn more about the VHAL, see the
VHAL overview.
Use debug shell commands
A third way to control which optional features to enable or disable is through the use of a
pair of shell commands, which are available only in user-debug builds and are
provided for use by developers. The table in
List of optional features contains the values to use instead of
<FEATURE_STRING_VALUE>.
To enable a feature:
adb root; adb shell cmd car_service enable-feature <FEATURE_STRING_VALUE>; adb reboot
To disable a feature:
adb root; adb shell cmd car_service disable-feature <FEATURE_STRING_VALUE>; adb reboot
Determine which features are enabled
When debugging issues related to specific features, it can be helpful to know which features are
enabled and why. To dump feature-related information, run:
adb shell dumpsys car_service --services CarFeatureController
This command lists the types of information shown below.
| Value | Description |
|---|---|
mEnabledFeatures |
Currently enabled features. |
mDefaultEnabledFeaturesFromConfig |
Optional features listed in config_allowed_optional_car_features. |
mDisabledFeaturesFromVhal |
Features specified by the VHAL to be disabled in the VHAL property,
DISABLED_OPTIONAL_FEATURES. |
mPendingEnabledFeatures |
Features to be enabled upon a reboot. |
mPendingDisabledFeatures |
Features to be disabled after a reboot. |