platform_hardware_interfaces/audio/README.md

Audio HAL

Directory structure of the audio HAL related code.

Directory Structure for AIDL audio HAL

The AIDL version is located inside aidl directory. The tree below explains the role of each subdirectory:

• aidl_api — snapshots of the API created each Android release. Every release, the current version of the API becomes "frozen" and gets assigned the next version number. If the API needs further modifications, they are made on the "current" version. After making modifications, run m <package name>-update-api to update the snapshot of the "current" version.
• android/hardware/audio/common — data structures and interfaces shared between various HALs: BT HAL, core and effects audio HALs.
• android/hardware/audio/core — data structures and interfaces of the core audio HAL.
• default — the default, reference implementation of the audio HAL service.
• vts — VTS tests for the AIDL HAL.

Directory Structure for HIDL audio HAL

Run common/all-versions/copyHAL.sh to create a new version of the HIDL audio HAL based on an existing one. Note that this isn't possible since Android T release. Android U and above uses AIDL audio HAL.

• 2.0 — version 2.0 of the core HIDL API. Note that .hal files can not be moved into the core directory because that would change its namespace and include path.
  • config — the XSD schema for the Audio Policy Manager configuration file.
• 4.0 — version 4.0 of the core HIDL API.
• ...
• common — common types for audio core and effect HIDL API.
  • 2.0 — version 2.0 of the common types HIDL API.
  • 4.0 — version 4.0.
  • ...
  • 7.0 — version 7.0.
    • example — example implementation of the core and effect V7.0 API. It represents a "fake" audio HAL that doesn't actually communicate with hardware.
  • all-versions — code common to all version of both core and effect API.
    • default — shared code of the default implementation.
      • service — vendor HAL service for hosting the default implementation.
    • test — utilities used by tests.
    • util — utilities used by both implementation and tests.
• core — VTS tests and the default implementation of the core API (not HIDL API, it's in audio/N.M).
  • 7.0 — code specific to version V7.0 of the core HIDL API
  • all-versions — the code is common between all versions, version-specific parts are enclosed into conditional directives of preprocessor or reside in dedicated files.
    • default — code that wraps the legacy API (from hardware/libhardware).
      • util — utilities for the default implementation.
    • vts VTS tests for the core HIDL API.
• effect — same for the effect HIDL API.
  • 2.0
    • config — the XSD schema for the Audio Effects configuration file.
  • 4.0
  • ...
  • all-versions
    • default — code that wraps the legacy API (from hardware/libhardware).
      • util — utilities for the default implementation.
    • vts VTS tests for the effect HIDL API.
• policy — Configurable Audio Policy schemes.
  • 1.0 — note that versions of CAP are not linked to the versions of audio HAL.
    • vts — VTS tests for validating actual configuration files.
    • xml — XSD schemas for CAP configuration files.