harmony(鸿蒙)Before You Start

2022-08-09
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Before You Start

This document provides basic guidance for OpenHarmony developers and system on a chip (SoC) or module vendors to port OpenHarmony to typical chip architectures, such as the Cortex-M and RISC-V series. Currently, the Bluetooth service is not supported. Due to the complexity of the OpenHarmony project, this document is subject to update as the version and APIs change.

This guide is intended for readers who have experience in developing embedded systems. Therefore, it mainly describes operations and key points during platform porting instead of basic introduction to the OS.

Porting Directory

The implementation of the OpenHarmony project directories and functions relies on the OS itself. If no enhancement for a complex feature is involved, you only need to focus on the directories described in the following table.

Table 1 Key directories in the porting process

Directory	Description
/build/lite	OpenHarmony basic compilation and building framework.
/kernel/liteos_m	Basic kernel. The implementation related to the chip architecture is in the arch directory.
/device	Board-level implementation, which complies with the OpenHarmony specifications. For details about the directory structure and porting process, see Overview.
/vendor	Product-level implementation, which is contributed by product vendors.

The device directory is in the internal structure of device/{Chip solution vendor}/{Development board}. The following uses HiSilicon hispark_taurus as an example:

device
└── hisilicon                      # Name of the chip solution vendor
    ├── common                     # Common part of the chip solution development board
    └── hispark_taurus             # Name of the development board
        ├── BUILD.gn               # Entry to building the development board
        ├── hals                   # OS hardware adaptation of the chip solution vendor
        ├── linux                  # Linux version
        │   └── config.gni         # Configurations of the building toolchain and building options for the Linux version
        └── liteos_a               # LiteOS Cortex-A version
            └── config.gni         # Configurations of the building toolchain and building options for the LiteOS Cortex-A version

The vendor directory is in the internal structure of vendor/{Product solution vendor}/{Product name}. The following uses the Wi-Fi IoT product as an example:

vendor                       # Product solution vendor
└── example                  # Name of the product solution vendor
    └── wifiiot              # Product name
          ├── hals           # OS adaptation of the product solution vendor
          ├── BUILD.gn       # Product building script
          └── config.json    # Product configuration file

Porting Process

The device directory of OpenHarmony is the adaptation directory for the basic SoC. You can skip the porting process and directly develop system applications if complete SoC adaptation code is already available in the directory. If there is no corresponding SoC porting implementation in the directory, complete the porting process by following the instructions provided in this document. The following figure shows the process of porting OpenHarmony to a third-party SoC.

Figure 1 Key steps for SoC porting

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Porting Specifications

The porting must comply with the basic principles described in How to Contribute.
The code required for third-party SoC adaptation is stored in the device, vendor, and arch directories. Naming and usage of these directories must comply with specified naming and usage specifications. For details, see Overview and Board-Level Directory Specifications.