Project: /_project.yaml Book: /_book.yaml
{% include “_versions.html” %}
All healthd
code has been refactored into health@2.0-impl and libhealthservice
, then modified to implement health@2.0 HAL. These two libraries are linked statically by health@2.0-service, enabling it to do the work previously done by healthd
(i.e. run the healthd_mainloop
and do polling). In init, the health@2.0-service registers an implementation of the interface IHealth
to hwservicemanager
. When upgrading devices with an Android 8.x vendor image and an Android {{ androidPVersionNumber }} framework, health@2.0 service might not be provided by the vendor image. This is enforced by the deprecation schedule.
To resolve this issue:
healthd
registers IHealth
to hwservicemanager
(despite being a system daemon). IHealth
is added to the system manifest, with instance name “backup”.storaged
communicate with healthd
via hwbinder
instead of binder
.storaged
are changed to fetch the instance “default” if available, then “backup”.libhealthhalutils
.HealthServiceWrapper
.healthd
can be deprecated. For more details, see Deprecating health@1.0.BOARD_PERIODIC_CHORES_INTERVAL_*
are board-specific variables used to build healthd
. As part of system/vendor build split, board-specific values cannot be defined for system modules. In health@2.0, vendors can override these two values in healthd_mode_ops->init
(by dropping libhealthservice
dependency in health@2.0-service.<device>
and re-implementing this function).
Unlike other HAL implementation libraries, the implementation library health@2.0-impl is a static library to which health@2.0-service, charger, recovery, and legacy healthd link.
health@2.0.impl implements IHealth
as described above and is meant to wrap around libbatterymonitor
and libhealthd.BOARD. These users of health@2.0-impl must not use BatteryMonitor
or the functions in libhealthd
directly; instead, these calls should be replaced with calls into the Health
class, an implementation of theIHealth
interface. To generalize further, healthd_common
code is also included in health@2.0-impl. The new healthd_common
contains the rest of common code between health@2.0-service, charger, and healthd
and calls into IHealth methods instead of BatteryMonitor.
When implementing health@2.0 service for a device, if the default implementation is:
Sufficient for the device, use android.hardware.health@2.0-service
directly.
Not sufficient for the device, create the android.hardware.health@2.0-service.(device)
executable and include:
#include <health2/service.h> int main() { return health_service_main(); }
Then:
If board-specific libhealthd:
healthd_board_init
and healthd_board_battery_update
functions.If board-specific BOARD_PERIODIC_CHORES_INTERVAL_*
variables:
HealthServiceCommon.cpp
(copied from hardware/interfaces/health/2.0/utils/libhealthservice
) and customize it in healthd_mode_service_2_0_init
.libhealthservice
statically.If device:
getStorageInfo
and getDiskStats
APIs, provide the implementation in get_storage_info
and get_disk_stats
functions.libstoragehealthdefault
statically.For details, refer to hardware/interfaces/health/2.0/README.md{: .external}.
health@2.0 has the following clients:
charger. The usage of libbatterymonitor
and healthd_common
code is wrapped in health@2.0-impl.
recovery. The linkage to libbatterymonitor
is wrapped in health@2.0-impl. All calls to BatteryMonitor
are replaced by calls into Health
implementation class.
BatteryManager. BatteryManager.queryProperty(int id)
was the only client of IBatteryPropertiesRegistrar.getProperty
which was provided by healthd
and directly reads /sys/class/power_supply
.
As a security consideration, apps are not allowed to call into health HAL directly. In Android {{ androidPVersionNumber }}, the binder service IBatteryPropertiesRegistrar
is provided by BatteryService
instead of healthd
and BatteryService
delegates the call to health HAL to retrieve the requested information.
BatteryService. In Android {{ androidPVersionNumber }}, BatteryService
uses HealthServiceWrapper
to determine the health service instance to use (“default” instance from vendor or “backup” instance from healthd). It then listens for health events via IHealth.registerCallback
.
Storaged. In Android {{ androidPVersionNumber }}, storaged
uses libhealthhalutils
to determine the health service instance to use (“default” instance from vendor or “backup” instance from healthd). It then listens for health events via IHealth.registerCallback
and retrieves storage information.
The new health@2.0 HAL includes the following SELinux changes:
file_contexts
.system_server
and storaged
to use hal_health
.system_server
(BatteryService
) to register batteryproperties_service
(IBatteryPropertiesRegistrar
).healthd
to provide hal_health
.system_server
/ storaged
to call into healthd
via binder.healthd
to register batteryproperties_service
(IBatteryPropertiesRegistrar
).For devices with their own implementation, some vendor SELinux changes may be necessary. Example:
# device/<manufacturer>/<device>/sepolicy/vendor/file_contexts /vendor/bin/hw/android\.hardware\.health@2\.0-service.<device> u:object_r:hal_health_default_exec:s0 # device/<manufacturer>/<device>/sepolicy/vendor/hal_health_default.te # Add device specific permissions to hal_health_default domain, especially # if it links to board-specific libhealthd or implements storage APIs.
The healthd
daemon and the default implementation android.hardware.health@2.0-service
access the following kernel interfaces to retrieve battery information:
/sys/class/power_supply/*/capacity
/sys/class/power_supply/*/charge_counter
/sys/class/power_supply/*/charge_full
/sys/class/power_supply/*/current_avg
/sys/class/power_supply/*/current_max
/sys/class/power_supply/*/current_now
/sys/class/power_supply/*/cycle_count
/sys/class/power_supply/*/health
/sys/class/power_supply/*/online
/sys/class/power_supply/*/present
/sys/class/power_supply/*/status
/sys/class/power_supply/*/technology
/sys/class/power_supply/*/temp
/sys/class/power_supply/*/type
/sys/class/power_supply/*/voltage_max
/sys/class/power_supply/*/voltage_now
Any device-specific health HAL implementation that uses libbatterymonitor
accesses these kernel interfaces by default, unless overridden in healthd_board_init(struct healthd_config*)
.
If these files are missing or are inaccessible from healthd
or from the default service (e.g. the file is a symlink to a vendor-specific folder that denies access because of misconfigured SELinux policy), they may not function correctly. Hence, additional vendor-specific SELinux changes may be necessary even though the default implementation is used.
Android {{ androidPVersionNumber }} includes new VTS tests written specifically for the health@2.0 HAL. If a device declares to provide health@2.0 HAL in the device manifest, it must pass the corresponding VTS tests. Tests are written for both the default instance (to ensure that the device implements the HAL correctly) and the backup instance (to ensure that healthd
continues to function correctly before it is removed).