SDK Layout and Responsibilities

A T527 Android 13 SDK normally combines the Android source tree with longan. Android builds the framework, HALs, applications, and system images. Longan builds the bootloader, Linux kernel, Allwinner BSP drivers, Device Tree, and firmware packaging inputs.

Top-Level Layout

<ANDROID_TOP>/
├── build/
├── device/
├── frameworks/
├── hardware/
├── packages/
├── system/
├── vendor/
├── out/
└── longan/
    ├── brandy/
    ├── bsp/
    ├── build/
    ├── buildroot/
    ├── device/
    ├── kernel/
    ├── out/
    ├── platform/
    ├── prebuilt/
    ├── tools/
    └── build.sh

Some branches omit optional directories or add private vendor repositories.

Android-Side Directories

Directory	Responsibility
build/	Android build system and envsetup.sh
device/	Android product, board, partition, property, overlay, and product-make configuration
frameworks/	Framework, system services, media, and graphics code
hardware/	HAL interfaces and vendor HAL implementations
packages/	System and common applications
system/	Core Android system components
vendor/	Allwinner and product-specific code and prebuilt files
out/	Generated Android output; do not edit it as source

Longan-Side Directories

Directory	Responsibility
longan/brandy/	boot0, U-Boot, and related startup code
longan/bsp/	Allwinner drivers, Kconfig, Makefile, SoC-level DTSI, and common configuration
longan/device/	Chip and board DTS, defconfig, partition, and packaging configuration
longan/kernel/	Upstream-style Linux 5.15 kernel code and links to the BSP repository
longan/build/	Configuration, build, and packaging scripts used by build.sh
longan/out/	Bootloader, kernel, DTB, module, and package output
longan/platform/	Allwinner private user-space components and tools
longan/buildroot/	Root file system and packages for Linux/Buildroot targets

The Three Most Important Repositories

device: board-specific differences
   +
bsp: Allwinner drivers and SoC configuration
   +
kernel: standard Linux kernel code and interfaces
   ↓
Longan produces the kernel, DTB, modules, and firmware inputs

With the independent BSP design, do not assume an Allwinner driver is under kernel/drivers/. It is often under longan/bsp/drivers/ or longan/bsp/modules/.

Quick Layout Check

cd <ANDROID_TOP>

find longan -maxdepth 2 -type d \
    \( -name bsp -o -name device -o -name kernel -o -name out \) \
    -print

find longan/device/config/chips/t527 -maxdepth 4 -type f \
    \( -name 'board.dts' -o -name '*defconfig' -o -name 'BoardConfig.mk' \) \
    -print

Confirm the active board before editing so that changes are not accidentally made in another product configuration.