Kernel Compile

This guide describes how to build and package the Bianbu kernel and the other BSP components — U-Boot and OpenSBI — which are distributed as standard debian packages (linux-riscv-spacemit-generic, u-boot-spacemit, opensbi-spacemit). The sources are hosted at gitee.com/spacemit-buildroot. This document describes how to build and package them, using Bianbu 4.0 (K3) as an example.

Component	Source repository	K3 branch	K1 branch
Kernel	`linux-6.18` (K3) / `linux-6.6` (K1)	`k3-br-v1.0.y` (board config `k3`)	`k1-bl-v2.2.y` (board config `k1`)
U-Boot	`uboot-2022.10`	`k3-br-v1.0.y`	`k1-bl-v2.2.y`
OpenSBI	`opensbi`	`k3-br-v1.0.y`	`k1-bl-v2.2.y`

Environment Requirements

Cross compilation (x86_64 host): use the official toolchain, download at http://archive.spacemit.com/toolchain/, e.g. spacemit-toolchain-linux-glibc-x86_64-v1.0.0.tar.xz:
```
sudo tar -Jxf /path/to/spacemit-toolchain-linux-glibc-x86_64-v1.0.0.tar.xz -C /opt
export PATH=/opt/spacemit-toolchain-linux-glibc-x86_64-v1.0.0/bin:$PATH
```
Native compilation (on a K3 board or a riscv64 container/machine): build directly, no cross toolchain needed.

Install build dependencies:

sudo apt-get -y install git bison flex bc cpio rsync libncurses-dev \
    debhelper devscripts libssl-dev libssl3 openssl u-boot-tools xmlto asciidoc \
    libelf-dev libdw-dev systemtap-sdt-dev libaudit-dev libslang2-dev libiberty-dev \
    liblzma-dev libcap-dev libnuma-dev python3-dev libbabeltrace-dev libunwind-dev \
    libtraceevent-dev libpfm4-dev pkg-config kmod

Quick Build (Script)

All three source repositories ship a cross-compilation packaging script (scripts/build_kernel.sh in linux-6.18; scripts/build.sh in uboot-2022.10 and opensbi) that configures, cross-compiles, and packages the deb in one command:

cd ~/linux-6.18
./scripts/build_kernel.sh -c -d    # clean build producing deb packages

cd ~/uboot-2022.10
./scripts/build.sh -c -d           # same for U-Boot; identical usage in the opensbi repository

Notes:

By default the build runs inside a Docker container (image harbor.spacemit.com/bianbu/k3-bsp-builder:latest, with the cross toolchain bundled), so the host needs no toolchain; set DIRECT_BUILD=1 to build directly on the host instead (toolchain required as above);
Common options: -c clean build, -d build deb packages, -j N parallel jobs (default nproc); commands: build (default) and shell (interactive container shell);
The packaging details match the manual flow below: the kernel uses k3_bianbu_defconfig with KERNELRELEASE derived from the kernel Makefile plus the -generic suffix (KDEB_SOURCENAME=linux-riscv-spacemit-generic); U-Boot/OpenSBI generate the changelog automatically and run dpkg-buildpackage -us -uc -b -a riscv64;
The deb packages land in the parent directory of the repository.

For custom kernel configurations or building modules/device trees separately, use the manual flow below.

Kernel

Using K3's linux-6.18 as an example (for K1 use linux-6.6, and replace the repository, branch, and defconfig with the K1 counterparts).

Fetch the Source

git clone -b k3-br-v1.0.y https://gitee.com/spacemit-buildroot/linux-6.18 ~/linux-6.18
cd ~/linux-6.18

Cross Compilation

Set up the build parameters:

export ARCH=riscv
export CROSS_COMPILE=riscv64-unknown-linux-gnu-

Generate the default configuration:

make k3_bianbu_defconfig

Modify the configuration (optional):

make menuconfig

To save the modified configuration:

make savedefconfig
mv defconfig arch/riscv/configs/k3_bianbu_defconfig

Build the debian packages:

KERNELRELEASE=6.18.3 LOCALVERSION=-generic \
KDEB_SOURCENAME=linux-riscv-spacemit-generic \
KDEB_PKGVERSION=6.18.3-$(date +%y%m%d) \
KDEB_CHANGELOG_DIST=stable \
make -j$(nproc) bindeb-pkg

LOCALVERSION: kernel version suffix; the official generic kernel uses -generic;
KDEB_SOURCENAME/KDEB_PKGVERSION: package name and version (follow the Bianbu release naming rules);
A build succeeds when dpkg-buildpackage: info: binary-only upload (no source included) is printed.

The packages land in the parent directory (..). Common packages:

linux-image-6.18.3-generic_*.deb: kernel image
linux-headers-6.18.3-generic_*.deb: kernel headers (for building modules)
linux-tools-*: perf etc.

Copy to the device, install, and reboot:

sudo dpkg -i linux-image-6.18.3-generic_*.deb
sudo reboot

Note: on UEFI-booted boards, the postinst runs update-grub, which generates entries with devicetree via /etc/grub.d/09_bianbu_uefi — no manual steps needed.

Native Compilation

On a K3 board or in a riscv64 container:

cd ~/linux-6.18
export ARCH=riscv
make k3_bianbu_defconfig
KERNELRELEASE=6.18.3 LOCALVERSION=-generic \
KDEB_SOURCENAME=linux-riscv-spacemit-generic \
KDEB_PKGVERSION=6.18.3-$(date +%y%m%d) \
KDEB_CHANGELOG_DIST=stable \
make -j$(nproc) bindeb-pkg

Modules and Device Trees

Build out-of-tree modules (rtl8852bs as an example):

make -j$(nproc) -C ~/linux-6.18 M=/path/to/rtl8852bs modules

Replace /path/to/rtl8852bs with your path.

To build modules locally without the kernel source, install linux-headers first:

sudo apt-get install linux-headers-`uname -r`
cd /path/to/rtl8852bs
make -j$(nproc) -C /lib/modules/`uname -r`/build M=/path/to/rtl8852bs modules

Build device trees separately:

make -j$(nproc) dtbs

U-Boot

Fetch the Source

git clone -b k3-br-v1.0.y https://gitee.com/spacemit-buildroot/uboot-2022.10 ~/uboot-2022.10
cd ~/uboot-2022.10

Build Directly

For cross compilation, set the environment variables first (skip for native compilation):

export ARCH=riscv
export CROSS_COMPILE=riscv64-unknown-linux-gnu-
make k3_defconfig
make -j$(nproc)

Debian Packaging (recommended, matches the official distribution)

The source repository ships a debian/ packaging directory. Note that apt-get build-dep requires enabled deb-src repository lines (commented out by default on Ubuntu — uncomment them and run apt-get update first):

rm -f debian/changelog
VERSION=1~$(git rev-parse --short HEAD)
dch --create --package u-boot-spacemit -v ${VERSION} --distribution stable --force-distribution "Bianbu ${VERSION}"
apt-get -o DPkg::Lock::Timeout=600 build-dep -y .
apt-get -o DPkg::Lock::Timeout=600 install -y device-tree-compiler git
dpkg-buildpackage -us -uc -b -a riscv64

Cross compilation (x86_64 host) must pass -a riscv64: debian/rules then sets CROSS_COMPILE=riscv64-unknown-linux-gnu- automatically (using the official toolchain installed above); without -a, the build uses the host gcc and fails.
For native compilation (on a K3 board or a riscv64 machine), drop -a riscv64.

The resulting u-boot-spacemit_${VERSION}_all.deb is in the parent directory. After installation the firmware files live in /usr/lib/u-boot/spacemit/ on the board system (bootinfo_block.bin, bootinfo_spinand.bin, bootinfo_spinor.bin, FSBL.bin, u-boot.itb, env.bin).

Note: when installing u-boot-spacemit, the postinst script locates the target medium automatically (SD card /dev/mmcblk0, eMMC /dev/mmcblk2, UFS /dev/sda, NAND/NOR /dev/mtdblock0, etc., determined from the boot_mode/root device) and dd-writes bootinfo_*.bin, FSBL.bin, env.bin, u-boot.itb to the corresponding firmware partitions; it takes effect after a reboot — no image rebuild needed. Under UEFI boot mode u-boot.itb is not written. Make sure the boot parameters point to the correct medium.

OpenSBI

Fetch the Source

git clone -b k3-br-v1.0.y https://gitee.com/spacemit-buildroot/opensbi ~/opensbi
cd ~/opensbi

Debian Packaging

rm -f debian/changelog
VERSION=1~$(git rev-parse --short HEAD)
dch --create --package opensbi-spacemit -v ${VERSION} --distribution stable --force-distribution "Bianbu ${VERSION}"
apt-get -o DPkg::Lock::Timeout=600 build-dep -y .
apt-get -o DPkg::Lock::Timeout=600 install -y git
dpkg-buildpackage -us -uc -b -a riscv64

The usage of -a riscv64 is the same as for U-Boot (required for cross compilation, dropped for native builds).

The resulting opensbi-spacemit_${VERSION}_all.deb is in the parent directory. After installation the firmware lives in /usr/lib/riscv64-linux-gnu/opensbi/generic/fw_dynamic.itb on the board system.

The opensbi-spacemit postinst also writes fw_dynamic.itb to the firmware partition at install time; it takes effect after a reboot.

K1 Platform (Bianbu 2.x)

K1 uses linux-6.6:

git clone -b k1-bl-v2.2.y https://gitee.com/spacemit-buildroot/linux-6.6 ~/linux-6.6
cd ~/linux-6.6
export ARCH=riscv
export CROSS_COMPILE=riscv64-unknown-linux-gnu-   # set for cross compilation; omit for native builds
make k1_defconfig

For the PREEMPT_RT real-time kernel, first update the source tree to the commit 3ac79a6dd update rt defconfig or any later version, then apply the RT patches and generate the configuration:

patch -p1 < rt-linux/*.patch
make k1_rt_defconfig

The remaining build and packaging steps are the same as for K3, with the version-number differences: the K1 kernel version is 6.6.x (e.g. KERNELRELEASE=6.6.63, KDEB_PKGVERSION=6.6.63-...), and the official kernel carries no -generic suffix (LOCALVERSION=""), so the packages are named like linux-image-6.6.63_6.6.63-*.deb. For U-Boot/OpenSBI, use the k1-bl-v2.2.y branch; everything else is identical.

Environment Requirements​

Quick Build (Script)​

Kernel​

Fetch the Source​

Cross Compilation​

Native Compilation​

Modules and Device Trees​

U-Boot​

Fetch the Source​

Build Directly​

Debian Packaging (recommended, matches the official distribution)​

OpenSBI​

Fetch the Source​

Debian Packaging​

K1 Platform (Bianbu 2.x)​

Environment Requirements

Quick Build (Script)

Kernel

Fetch the Source

Cross Compilation

Native Compilation

Modules and Device Trees

U-Boot

Fetch the Source

Build Directly

Debian Packaging (recommended, matches the official distribution)

OpenSBI

Fetch the Source

Debian Packaging

K1 Platform (Bianbu 2.x)