HAL Interface Generation

This document describes how to generate Hardware Abstraction Layer (HAL) interface definitions using the Android Interface Definition Language (AIDL).

Prerequisites

Building this repository requires the AIDL compiler (aidl). This can be obtained by building the linux_binder_idl project, available on GitHub: github.com/rdkcentral/linux_binder_idl.git. Alternatively, you can use a Docker image that includes aidl, such as rdk-dunfell or the recommended rdk-kirkstone.

Building `aidl` from `linux_binder_idl`

Minimum Required GCC Version: 9.4.0

Using the rdk-kirkstone Docker image is highly recommended.

Clone the linux_binder_idl repository:

git clone git@github.com:rdkcentral/linux_binder_idl.git
cd linux_binder_idl

Build aidl:

# Optional: Run inside the Docker container
sc docker run rdk-kirkstone /bin/bash

Then build the aidl tool.

./build-aidl-generator-tool.sh

Locate the aidl binary:

The compiled aidl binary will be located in the local/bin directory within the linux_binder_idl project. The full path might resemble:

linux_binder_idl/local/bin/aidl

For more detailed information, refer to the github.com/rdkcentral/linux_binder_idl.git repository.

Generating AIDL Proxy and Native Interfaces

Clone the hal repository:

git clone git@github.com:rdkcentral/rdk-halif-aidl.git

Generate the AIDL proxy and native interfaces:

The following example demonstrates generating interfaces for the audiodecoder module. Adapt the AIDL_TARGET CMake variable for other modules.

cd hal

# Optional: Run inside the Docker container
sc docker run rdk-kirkstone /bin/bash

# Optional: Set AIDL binary path if not in system PATH.  Replace with the actual path from the previous step.
export PATH=$PATH:/path/to/linux_binder_idl/local/bin

cmake -DAIDL_TARGET=audiodecoder .

Warning

CMake must be run from the root directory of the hal repository, not within a specific module directory.

Locate the generated files:

The generated proxy and interface files will be placed under audiodecoder/gen/<version>. For example:

hal/audiodecoder/gen/current/cpp/com/rdk/hal/audiodecoder/...  (C++ files)
hal/audiodecoder/gen/current/h/com/rdk/hal/audiodecoder/...   (Header files)
hal/audiodecoder/current/com/rdk/hal/audiodecoder/...        (AIDL files)

Example CMake Commands

# Use a custom path to the `aidl` binary
cmake -DAIDL_TARGET=audiodecoder -DAIDL_BIN=/home/example/bin/aidl .

# Specify a specific AIDL interface version (e.g., version 2)
cmake -DAIDL_TARGET=audiodecoder -DAIDL_SRC_VERSION=2 .

# Specify a custom output directory for generated files
cmake -DAIDL_TARGET=audiodecoder -DAIDL_GEN_DIR=/home/example/example_out .

CMake Variables

Variable	Description
`AIDL_BIN`	Optional. Path to the `aidl` executable. If not set, CMake will attempt to locate it.
`AIDL_GEN_DIR`	Optional. Output directory for generated files. Default: `<module>/gen/<version>`.
`AIDL_SRC_VERSION`	Optional. Version of the AIDL interface to generate. Default: `current`.
`AIDL_TARGET`	Mandatory. Name of the module for which to generate interfaces.

Notes

The Broadcast module is currently disabled because its demux submodule depends on the Android framework.