How to build LineageOS for a device without official support? [closed]

Question

I have a Mi 8 Lite (platina), for which there is no official LineageOS support. But LineageOS custom ROM for the device is available on XDA. On further research, I can see that vendor files, device tree and kernel source code is available for my device:

1. Kernel Source
2. Device Tree
3. Vendor Files

How do I build a LineageOS ROM for my device without official support?

Answer 1

Firstly you need to setup the build environment. You should be running Ubuntu 18.04. LineageOS build guide for a random device can be used as a reference. Reproducing the steps here:

Install the build packages:

sudo apt install bc bison build-essential ccache curl flex g++-multilib gcc-multilib git gnupg gperf imagemagick lib32ncurses5-dev lib32readline-dev lib32z1-dev liblz4-tool libncurses5-dev libsdl1.2-dev libssl-dev libwxgtk3.0-dev libxml2 libxml2-utils lzop pngcrush rsync schedtool squashfs-tools xsltproc zip zlib1g-dev adb fastboot

Create the directories:

mkdir -p ~/bin
mkdir -p ~/android/lineage

Install the repo command:

curl https://storage.googleapis.com/git-repo-downloads/repo > ~/bin/repo
chmod a+x ~/bin/repo

Put the ~/bin directory in your path of execution by adding the following to your ~/.profile if it's missing:

# set PATH so it includes user's private bin if it exists
if [ -d "$HOME/bin" ] ; then
    PATH="$HOME/bin:$PATH"
fi

Then, run source ~/.profile to update your environment. After that, initialize the LineageOS source repository and start downloading:

cd ~/android/lineage
repo init -u https://github.com/LineageOS/android.git -b lineage-16.0
repo sync

Downloading LineageOS source will take some time. After that we will deviate from the official build guide. Create a local manifest file telling the repo tool where to pick up the kernel source, device tree and vendor files. The corresponding file for platina can be downloaded from here. If you are building for a different device, use this manifest file as a reference and edit it accordingly. Save the file as

.repo/local_manifests/platina.xml 

Rerun repo tool to fetch them:

repo sync

Initialise your build environment:

source build/envsetup.sh

Enable caching to speed up the build:

export USE_CCACHE=1

You should add the above line to your .bashrc file. Then set the max cache size:

ccache -M 50G

Configure jack:

export ANDROID_JACK_VM_ARGS="-Dfile.encoding=UTF-8 -XX:+TieredCompilation -Xmx4G"

Edit device/xiaomi/platina/BoardConfig.mk and set the parameter TARGET_KERNEL_CONFIG to platina_user_defconfig:

TARGET_KERNEL_SOURCE points to the kernel code that is to be used during the build. TARGET_KERNEL_CONFIG specifies which configuration is to be used. By looking in arch/arm64/configs/ in the kernel source, I set the value to platina_user_defconfig

Finally start the build:

lunch 16
mka bacon -j8

This should lake a few hours to complete. I usually leave it running overnight. Here is where things get challenging. It’s possible that the build can fail due to errors, in which case you will have to fix it. Once the build has completed, you will find the zip file, ready to flash: