Kernel

Building Android Kernel

Android is built around a Linux kernel. By default, Android’s boot.img is build from a binary kernel Image located in:

~/src/khadas-aosp-14/device/amlogic/yukawa-kernel/6.1

This guide describes how to rebuild and customize a Linux kernel for Android.

Fetching the kernel code

Fetch the code using repo:

mkdir ~/src/khadas-kernel/ && cd $_
repo init -u https://gitlab.baylibre.com/baylibre/amlogic/atv/aosp/kernel/manifest.git -b yukawa-android14-6.1
repo sync

Note

To save same disk space, pass the --clone-depth=1 option to repo init:

repo init -u https://gitlab.baylibre.com/baylibre/amlogic/atv/aosp/kernel/manifest.git -b yukawa-android14-6.1 --clone-depth=1

Building the kernel

In this section, we will assume that we already have an Android source tree which has been fully build and is located in:

~/src/khadas-aosp-14/

Build everything from scratch

For the 6.1 kernel, use:

cd ~/src/khadas-kernel/
export DIST_DIR=~/src/khadas-aosp-14/device/amlogic/yukawa-kernel/6.1
tools/bazel run //yukawa-device:yukawa_dist -- --dist_dir=$DIST_DIR

Re-running this command will rebuild incrementally

Defconfig/menuconfig changes

The usual (make menuconfig) is done by editing the arch/arm64/configs/amlogic_gki.fragment manually.

Rebuilding all involved Android images

To test the kernel changes, we have to re-generate the relevant Android images:

boot.img: contains the kernel binary and the main device tree
vendor.img: contains the kernel modules

To rebuild the Android images, do:

cd ~/src/khadas-aosp-14/
source build/envsetup.sh
lunch yukawa-userdebug
make bootimage vendorimage

Flashing the kernel

cd $ANDROID_PRODUCT_OUT
adb reboot fastboot
fastboot flash boot boot.img
fastboot flash vendor vendor.img
fastboot reboot