Prebuilt Raspberry Pi 5 kernel for BigFred hub OS.

This repository owns the kernel source pin and kconfig fragments. CI cross-compiles Image, DTBs, overlays, and modules, then publishes a tarball on GitHub Releases. bigfred-os should consume that tarball by version + SHA-256 (same pattern as Grafana), not rebuild Linux inside Buildroot.

The scripts in this repo are MIT. The kernel binary and modules are GPLv2 (raspberrypi/linux).

Target is Pi 5 / BCM2712 only. Pi 3 (64-bit kernel8) is hub-kernel-rpi3.

Build

On Ubuntu 24.04:

sudo ./scripts/install-deps.sh
make check
make package

make package writes dist/bigfred-kernel-rpi5-<version>.tar.xz and a matching .sha256. Untagged builds use g<shortsha> as the version.

Patches

patches/linux/*.patch are applied with patch -p1 after extract (see scripts/apply-patches.sh). The tree is a tarball, not a git checkout, so git am is not used.

Current carry (macb / Cadence GEM on RP1):

1. 0001-… — IMR MMIO read after re-enabling TCOMP (macb_tx_poll). PCIe read barrier without consuming ISR bits. raspberrypi/linux#7340 used a destructive ISR read; #7472 dropped it because RP1 GEM is clear-on-read.
2. 0002-… — 1 s TX-stall delayed_work calling macb_tx_restart(). Recovers a silent TX hang in ~1 s instead of the 5 s netdev watchdog. Restores #7340 patch 3, which #7472 also dropped.

The NCR posted-write flush from #7340 patch 1 is already in this pin (MACB_CAPS_PCIE_POSTED_WRITES on raspberrypi,rp1-gem).

When bumping LINUX_COMMIT, re-apply the series on the new tree. If upstream restores an equivalent fix, delete the local patches.

Release

1. Bump LINUX_COMMIT in VERSIONS and the SHA in configs/linux.hash if moving the upstream pin (recompute with sha256sum dl/linux-<commit>.tar.gz).

2. Change fragments under configs/ for hub CONFIG_* options, or add patches under patches/linux/.

3. Merge to main and wait for CI to finish (kernel build + artifact upload).

4. Tag v6.18.0-rN on that commit and push. release.yml does not rebuild; it downloads the CI artifact from the matching main run, relabels it, and publishes:

   • bigfred-kernel-rpi5-v6.18.0-rN.tar.xz
   • bigfred-kernel-rpi5-v6.18.0-rN.tar.xz.sha256

   Tagging before CI succeeds will fail with “no successful CI run on main”.

   To republish without moving a tag (e.g. after a workflow fix), use Actions → Release → Run workflow with tag and optional commit (short or full SHA of the green main CI run).

Artifact layout

Image
bcm2712-rpi-5-b.dtb
bcm2712d0-rpi-5-b.dtb
overlays/*.dtbo          # includes bcm2712d0.dtbo
lib/modules/<krel>/
config                   # kernel .config
manifest

Modules are uncompressed (CONFIG_MODULE_COMPRESS is off) because musl kmod on the hub image has failed to load XZ modules.

Compiler is Ubuntu aarch64-linux-gnu-gcc, not the Buildroot musl toolchain. The kernel is freestanding; libc does not matter. Rebuilds are reproducible against Ubuntu 24.04 + this pin.

Consuming from bigfred-os

Pin a release tag and the SHA-256 of the tarball (Buildroot .hash). If the committed hash matches the file in dl/, skip the download. A kernel CONFIG_* change is a PR here, then a tag, then a hash bump in bigfred-os.