Cairn

Cairn is the Kyanite baseboard management controller (BMC) software stack. It is a bare-metal BMC OS built with the TamaGo framework: pure Go, no OS, no libc, no CGo. It shares the microkernel substrate (src.kyanite.computer/core) with vein, the Kyanite switch OS.

Status: experimental — expect breaking changes.

This is early scaffolding: the first target is a structural stub that establishes the layering and patterns. It performs no hardware management yet — sensor, power and inventory drivers land during hardware enablement.

Hardware

Component	Detail
SoC	ASPEED AST2700 (dual Cortex-A35, ARMv8-A / arm64)
RAM	1 GB DRAM, CA35 view at 0x400000000
Board	AST2700 DC-SCM EVB (AST2750-A1 DDR4)

Layout

Three layers, strictly by sharing scope (no layer imports one above it) — the same split as vein:

target/ast2700-dcscm-evb/   AST2700 DC-SCM PLATFORM code. Everything hardware-specific.
  main.go                     entry point; assembles the microkernel via core/operator
  board/                      platform identity; imports the upstream TamaGo board
                              package for CA35 bring-up (no in-tree hardware code yet)
  chassis/                    baseboard-management driver (implements pkg/bmcdev.Chassis; stub)

pkg/                        SHAREABLE across cairn targets; hardware-agnostic (deps on interfaces).
  bmcdev/                     baseboard-management interface + shared value types
  config/                     typed configuration layer (Defaults + Normalize pattern)

.dagger/                    Dagger CI/build module

The microkernel substrate (service supervision, operator, telemetry, config store) is the shared src.kyanite.computer/core module, consumed by both cairn and vein. target/ast2700-dcscm-evb/main.go assembles it declaratively via core/operator (a plain operator.Config — no functional options — with a caller-owned service slice). A new platform adds a sibling target/<platform>/ implementing the pkg/bmcdev interface and reuses everything in pkg/ and core/ unchanged.

Patterns

Cairn follows the same embedded-friendly conventions as vein:

• Configuration is a default struct + normalize + inject, not functional options: config.DefaultDefaults() / operator.DefaultConfig(), overridden by value and normalized, with caller-owned storage. This keeps memory ownership explicit and avoids closure/slice allocation on memory-constrained targets.
• Platform identity lives with the target. pkg/ holds no hardware detail; the factory hostname/IP/MAC and the concrete chassis driver are supplied by target/ast2700-dcscm-evb.
• Everything is supervised. Services implement core/service.Service and run under core/operator, which recovers panics and restarts per policy.

Build

The AST2700 arm64 SoC/board support lives in a TamaGo fork that is not yet upstream. Until it lands, go.work redirects github.com/usbarmory/tamago to that fork (../tamago).

make build       # AST2700 DC-SCM EVB ELF → bin/cairn.elf
make test        # host unit tests (user_linux tag)

Requires the TamaGo compiler (TAMAGO=/path/to/tamago-go/bin/go) and llvm-readelf.

Module

src.kyanite.computer/cairn

No CGo, no external C libraries. Compiles with GOOS=tamago GOARCH=arm64.

Contributing

See the org-wide CONTRIBUTING guide. Contributions are dual-licensed.

Security

See the org-wide SECURITY policy.

License

Dual-licensed under either of Apache-2.0 (LICENSE-APACHE) or MIT (LICENSE-MIT) at your option.