✨ feat(rpi): extend Pi support to Raspberry Pi 5 (BCM2712)

Wires up the rpi5 build target on top of the board-aware Pi
infrastructure. Pi-5-only logic in modules/rpi.nix (firmware-
partition contents, [pi5] config.txt block, NixOS-built kernel
as gzipped kernel_2712.img, NixOS-built initrd, explicit
toplevel cmdline) is reachable via stereos.rpi.series = "rpi5",
which the rpi5MixtapeSpecs set inline.

Why a NixOS-built kernel as kernel_2712.img instead of
raspberrypifw's prebuilt:

  • The firmware-shipped kernel_2712.img is a different version
    (e.g. 6.12.25-v8-16k+ in fw 1.20250430) than the kernel
    nixos-hardware configures (linux-rpi 6.12.75-1+rpt1). Booting
    the firmware kernel makes /lib/modules/<our-version>/ unusable
    — modprobe fails for everything kernel-module-dependent.
  • nixpkgs at our pinned rev has no ubootRaspberryPi5_64bit, so
    the standard sd-image-aarch64 U-Boot+extlinux flow is
    unavailable on Pi 5. We replace the prebuilt kernel directly
    and write our own cmdline.txt.
  • Pi 5 EEPROM detects the gzip magic on kernel_2712.img and
    decompresses on load; linuxPackages_rpi5 only installs the
    raw Image, so we gzip it during firmware-partition population.

D0 vs C1 silicon: the EEPROM auto-selects bcm2712d0-rpi-5-b.dtb
on D0 boards when both DTBs *and* overlays/bcm2712d0.dtbo are
present. Ship only the C1 dtb and a 2 GB / rev-1.1 board panics
during pinctrl-bcm2712 probe with an Asynchronous SError. We ship
the full bcm2712 dtb glob and the entire overlays/ tree.

GPIO 14/15 UART: enable_uart=1 by itself does not pinmux the
RP1's UART0 to the GPIO header on Pi 5. The dtoverlay=uart0-pi5
overlay does that routing; the device enumerates as ttyAMA0,
matching Pi 4's name (ttyAMA10 on Pi 5 is the dedicated
debug-header UART, not GPIO 14/15).

nixos-hardware pin: pinned to f1b7ff92cdd1 — the last commit
before nixos-hardware#1841 replaced the rpi-kernel postConfigure
sed with `LOCALVERSION = freeform ""`, which round-trips through
nixpkgs' kernel-config emitter as the literal two characters `""`
and breaks the modDirVersion sanity check. Tracked in
nixos-hardware#1859, fix in #1860 unmerged as of 2026-05.

Pi-5-only artifacts:

  • flake.nix          nixos-hardware flake input
  • modules/rpi5-kernel-overlay.nix
                       overlay defaulting makeModulesClosure to
                       allowMissing=true; needed because all-
                       hardware.nix lists modules that the
                       rpi-vendor 6.12.x kernel builds as =y
                       (dw_hdmi, …) so they're not present as
                       .ko files in /lib/modules and modprobe
                       errors during the modules-shrunk step.
                       Pattern from nvmd/nixos-raspberrypi.
  • flake/images.nix   rpi5MixtapeSpecs (sets series + imports
                       nixos-hardware module + the kernel-
                       overlay), rpi5Pkgs.
  • Makefile           build-rpi5 / flash-rpi5 targets.

Author: yeazelm

Makefile

@@ -40,7 +40,8 @@ build-kernel: ## Build kernel artifacts for kernel boot
 # -- Raspberry Pi image builds -----------------------------------------------
 #
 # RPi images are aarch64-only and ship as a single SD card image.
-# The attr name adds "-rpi4-sd" to the mixtape (e.g. coder → coder-rpi4-sd).
+# The attr name adds "-rpi4-sd" / "-rpi5-sd" to the mixtape
+# (e.g. coder → coder-rpi4-sd, coder → coder-rpi5-sd).
 
 .PHONY: build-rpi4
 build-rpi4: ## Build an SD card image for Raspberry Pi 4 (MIXTAPE=coder by default)
@@ -51,6 +52,15 @@ flash-rpi4: ## Flash RPi4 SD image to an SD card (SSH_KEY=~/.ssh/id_ed25519.pub
 	@./scripts/flash-rpi.sh --board rpi4 \
 		$(if $(SSH_KEY),--ssh-key $(SSH_KEY))
 
+.PHONY: build-rpi5
+build-rpi5: ## Build an SD card image for Raspberry Pi 5 (MIXTAPE=coder by default)
+	nix build .#packages.aarch64-linux.$(MIXTAPE)-rpi5-sd --impure -o result-rpi5
+
+.PHONY: flash-rpi5
+flash-rpi5: ## Flash RPi5 SD image to an SD card (SSH_KEY=~/.ssh/id_ed25519.pub optional)
+	@./scripts/flash-rpi.sh --board rpi5 \
+		$(if $(SSH_KEY),--ssh-key $(SSH_KEY))
+
 # -- VM development operations ------------------------------------------------
 
 .PHONY: run

flake.lock

@@ -5,6 +5,19 @@
     nixpkgs.url = "github:NixOS/nixpkgs/nixos-25.11";
     nixpkgs-unstable.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
     flake-parts.url = "github:hercules-ci/flake-parts";
+
+    # Raspberry Pi 4 / 5 configuration. The Pi 5 module sets
+    # boot.kernelPackages to the rpi-vendor 6.12.x kernel (built with
+    # bcm2712_defconfig and the RP1-southbridge initrd modules); without
+    # this input there is no Pi 5 kernel in nixpkgs at our pinned rev.
+    #
+    # Pinned to f1b7ff92cdd1 — the last commit before nixos-hardware#1841
+    # replaced the kernel's postConfigure sed with `LOCALVERSION = freeform ""`,
+    # which expands through nixpkgs' kernel-config emitter as the literal
+    # two characters `""`, breaking modDirVersion at build time. Tracked
+    # in nixos-hardware#1859; fix in #1860 is open but unmerged. Revisit
+    # the pin once #1860 (or any later fix) lands on master.
+    nixos-hardware.url = "github:NixOS/nixos-hardware/f1b7ff92cdd1";
     dagger.url = "github:dagger/nix";
     dagger.inputs.nixpkgs.follows = "nixpkgs";
 

flake.nix

@@ -9,13 +9,15 @@
 #   packages.<system>.<mixtape-name>-kernel-artifacts   (direct-kernel boot)
 #   packages.<system>.<mixtape-name>-dist               (all formats + mixtape.toml)
 #
-# RPi mixtapes only emit an SD card image:
+# RPi mixtapes only emit an SD card image, suffixed by board:
 #   packages.aarch64-linux.<mixtape-name>-rpi4-sd       (Pi 4 SD image)
+#   packages.aarch64-linux.<mixtape-name>-rpi5-sd       (Pi 5 SD image)
 #
 # Build with:
 #   nix build .#packages.aarch64-linux.coder --impure
 #   nix build .#packages.x86_64-linux.coder --impure
 #   nix build .#packages.aarch64-linux.coder-rpi4-sd --impure
+#   nix build .#packages.aarch64-linux.coder-rpi5-sd --impure
 
 { self, inputs, ... }:
 
@@ -45,6 +47,28 @@ let
     { name = "coder-rpi4-dev"; features = [ ../mixtapes/coder/package.nix ]; extraModules = [ ../profiles/rpi.nix ../profiles/dev.nix ]; }
   ];
 
+  # RPi 5 mixtape definitions — aarch64-only, SD image output.
+  # Each spec sets stereos.rpi.series = "rpi5" inline so modules/rpi.nix
+  # writes the Pi 5 firmware partition + [pi5] config.txt block, and pulls
+  # in nixos-hardware.raspberry-pi-5 for the rpi-vendor 6.12.x kernel
+  # (nixpkgs has no Pi 5 kernel package at our pinned rev).
+  rpi5MixtapeSpecs =
+    let
+      rpi5Modules = [
+        ../profiles/rpi.nix
+        { stereos.rpi.series = "rpi5"; }
+        inputs.nixos-hardware.nixosModules.raspberry-pi-5
+        # Skip modules that all-hardware.nix lists but the rpi-vendor
+        # kernel builds as =y. See modules/rpi5-kernel-overlay.nix.
+        ../modules/rpi5-kernel-overlay.nix
+      ];
+    in [
+      { name = "base-rpi5";      features = [ ../mixtapes/base/package.nix ];  extraModules = rpi5Modules; }
+      { name = "coder-rpi5";     features = [ ../mixtapes/coder/package.nix ]; extraModules = rpi5Modules; }
+      { name = "base-rpi5-dev";  features = [ ../mixtapes/base/package.nix ];  extraModules = rpi5Modules ++ [ ../profiles/dev.nix ]; }
+      { name = "coder-rpi5-dev"; features = [ ../mixtapes/coder/package.nix ]; extraModules = rpi5Modules ++ [ ../profiles/dev.nix ]; }
+    ];
+
   # Helper to build packages for a given system
   buildSystemImages = system:
     let
@@ -115,8 +139,9 @@ let
           )
         else {};
       rpi4Pkgs = mkSdImagePkgs rpi4MixtapeSpecs;
+      rpi5Pkgs = mkSdImagePkgs rpi5MixtapeSpecs;
     in
-      rawPkgs // qcow2Named // kernelArtifactsNamed // distPkgs // rpi4Pkgs;
+      rawPkgs // qcow2Named // kernelArtifactsNamed // distPkgs // rpi4Pkgs // rpi5Pkgs;
 
   # Build packages for all target systems
   allPackages = builtins.listToAttrs (

flake/images.nix

@@ -0,0 +1,42 @@
+# modules/rpi5-kernel-overlay.nix
+#
+# Pi-5-only overlay: tell makeModulesClosure to skip modules listed in
+# boot.initrd.availableKernelModules that are absent from the rpi-vendor
+# kernel's /lib/modules tree.
+#
+# Why this is needed: nixpkgs' installer/sd-card/sd-image-aarch64.nix
+# transitively imports profiles/all-hardware.nix, which sets a giant
+# boot.initrd.availableKernelModules list (dw_hdmi, drm_kms_helper,
+# pwm-bcm2835, …). The rpi-vendor 6.12.x kernel built with
+# bcm2712_defconfig compiles many of those as =y — they live in vmlinuz
+# rather than as separate .ko files, so modprobe errors out with
+#
+#   modprobe: FATAL: Module dw-hdmi not found in directory ...
+#
+# during the `modules-shrunk` (makeModulesClosure) derivation, killing
+# the SD-image build before it assembles the initrd.
+#
+# Skipping them in the closure is safe because they're already linked
+# into the kernel image and auto-loaded by the kernel; there is no
+# corresponding action for the initrd to take.
+#
+# This is the canonical pattern: nvmd/nixos-raspberrypi applies the same
+# overlay unconditionally for every Pi variant. We scope it to Pi 5
+# builds (Pi 4 still uses the standard sd-image-aarch64 kernel and works
+# without the override).
+#
+# Refs:
+#   https://github.com/NixOS/nixpkgs/issues/154163
+#   https://discourse.nixos.org/t/cannot-build-raspberry-pi-sdimage-module-dw-hdmi-not-found/71804
+#   https://github.com/nvmd/nixos-raspberrypi/blob/master/modules/raspberrypi.nix
+
+{ ... }:
+
+{
+  nixpkgs.overlays = [
+    (final: super: {
+      makeModulesClosure = args:
+        super.makeModulesClosure (args // { allowMissing = true; });
+    })
+  ];
+}