@[TOC](HAL known how)
What is HAL?
HAL is short for Hardware abstraction Layer. This is a concept designed by Google to avoid the short of open source which vendors or driver company wanna not open source.
What for?
HAL defines a standard APIs for hardware vendors to implement
Tow generations of HAL
- The old version : Android OS 7 and below.
- The newest version : Android OS 8 and higher.
The Newest HAL : Dynamically Available HALs
Android 9 supports the dynamic shutdown of Android hardware subsystems when they are not in use or not needed.
For example, when a user is not using Wi-Fi, the Wi-Fi subsystems should not be taking up memory, power, or other system resources. In earlier versions of Android, HALs/drivers were kept open on Android devices for the entire duration an Android phone was booted.
Change to HAL
# some init.rc script associated with the HAL
service vendor.some-service-name /vendor/bin/hw/some-binary-service
# init language extension, provides information of what service is served
# if multiple interfaces are served, they can be specified one on each line
interface android.hardware.light@2.0::ILight default
# restarted if hwservicemanager dies
# would also cause the hal to start early during boot if disabled wasn't set
class hal
# will not be restarted if it exits until it is requested to be restarted
oneshot
# will only be started when requested
disabled
# ... other properties
to be continued >>
