Building a kernel for Mobian

Prerequisites

As super user :

dpkg --add-architecture arm64
apt-get update
apt-get dist-upgrade
apt-get install g++-aarch64-linux-gnu build-essential crossbuild-essential-arm64 git debootstrap u-boot-tools device-tree-compiler libncurses-dev flex bison libssl-dev rsync kmod

Get sources

git clone https://salsa.debian.org/Mobian-team/devices/sunxi64-linux.git pinephone-linux
cd pinephone-linux/

Apply patches in debian/patches

gbp pq import

applies those patches listed in debian/patches/series to a patch-queue/BRANCH branch (man page). (quilt push is an alternative means to achive this)

Generate .config from known working config

ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- make pine64_defconfig

Customization

make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- menuconfig

Compilation

ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- make -j4 bindeb-pkg KERNELRELEASE="5.9-sunxi64-test" KDEB_PKGVERSION="1"

KERNELRELEASE should include the string sunxi64 (in case of ?PineTab/PinePhone)

Backup .config file

ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- make savedefconfig

Testing debian package

You can mount with NFS your host folder or copy the debian package over ssh using scp.

On the target, you might be able to install the package with

sudo dpkg -i /path_to/linux-image-5.9-sunxi64-test_1_arm64.deb

And then use a hard reboot to test it.

Troubleshooting

In the case of a boot failure, you can follow this tutorial to re-enable the previous kernel by editing /boot/extlinux/extlinux.conf and change the default label to boot to the previous kernel.

Update Process

Rebasing is used over merging so we have all our commits on top of upstream and we're less likely to forget anything when rebasing over a newer kernel branch.

The following steps are used:

Pull the latest mobian-5.x branch and fetch from upstream
Create a new branch: git checkout -b mobian-5.x.y
Create the patch branch: gbp pq import
Switch back to the main branch: gbp pq switch
Rebase the main branch on latest upstream tag: git rebase v5.x.y
- For major kernel versions: git rebase --onto <latest upstream tag> <old upstream tag> <your working branch> See https://git-scm.com/book/ms/v2/Git-Branching-Rebasing (figure 39).
Create the new Debian-formatted upstream tag (needed for CI): git tag upstream/5.x.y+<platform> v5.x.y^{}
- <platform> can be sunxi64, librem5, sdm845, rockchip depending on the device(s) this kernel is targeting
- Don't forget to push the new tag: git push origin upstream/5.x.y+<platform>
Rebase our patches on top of the main branch: gbp pq rebase
- For major kernel versions: git rebase --onto <your working branch> <last commit of previous mobian version> patch-queue/<your working branch>
Update patch files: gbp pq export
Check the changes and make sure it still builds; Discard cosmetic-only changes (commit hashes, line numbers...) as long as the patches still apply cleanly without fuzz, that brings only noise for future reviews
If some patches were dropped in the process, renumber patch files: gbp pq export --renumber
Tag the upstream release with git tag -f upstream/<version>+sunxi64 v<version>^{} and push the tag. This allows CI to extract the source before building.

TeamsMobianKernelBuild