BFE Engineering
c756622c96
The repo's documentation framed it as a support repo for one product (WardenOS). Since going public the real audience is anyone with a Luckfox Pico 86 Panel: a maintained 6.18 kernel, an off-device development loop, and a device simulator that exist nowhere else for this board. Reframe the README and top-level docs board-first, with WardenOS documented as the downstream consumer it is (ADR-0008). Also an editorial pass over the whole doc set: - every H1/H2 is now a short title, not a sentence (ADRs, qemu/, patches/, drivers/, architecture, NPU feasibility, config-lint, payload); workflow flowchart titles fixed at the source in tools/flowgen.py and regenerated with fresh bench numbers - README Quick Start commands verified against the scripts; requirements corrected (curl, bare python, gcc >= 14) and the MC/DC gate added as a step (run green locally on gcc 14.2) - dropped the 'needs python (not python3)' vendor dig: build-kernel.sh inherited the same requirement (filed #10 to remove it) - glossed MC/DC and HPMCU on first use; marked the tests/uboot-ab reference as flare-edge; deduplicated the three-simulator list into the root README table
34 lines
1.8 KiB
Markdown
34 lines
1.8 KiB
Markdown
# ADR 0002 — Tiered MC/DC
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**Status:** Accepted (2026-08-25).
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## Context
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The goal "port + harden 100% of drivers to 100% MC/DC" is infeasible as literally
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stated: ~97% of driver LOC is vendor blobs (the AIC8800 wifi driver alone is 88.5K
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lines) that we cannot meaningfully unit-test to MC/DC on the host. Forcing MC/DC on
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that code would be theatre, not assurance.
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## Decision
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A **two-tier** policy, measured against the Hardware Abstraction Seam:
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- **Tier 1 — our own hardware-facing code → real 100% MC/DC.** `modbus_engine.c`,
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`relays.c`, `warden_rga.c` (wrapper), `hpmcu.rs`, `devmem.rs`, `freshness.c`, plus
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the two smallest near-mainline drivers where feasible. Enforced in CI
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(`gcc-14 -fcondition-coverage` + `gcov-14 --conditions`). Rust uses
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`cargo-llvm-cov` line/region coverage for now — true `--mcdc` needs a nightly
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toolchain (`-Z coverage-options=condition`) and is deferred on that tooling skew;
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the C drivers carry the literal MC/DC gate.
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- **Tier 2 — ported/vendor drivers → fault-injection + branch coverage + benchmarks**
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against the simulator, behind a stable seam. Explicitly NOT literal MC/DC.
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## Consequences
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- Matches the user's framing: "as many drivers as possible at 100% MC/DC; for the
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rest, a very serious testing and benchmarking system."
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- The seam is the shared object: the same thing MC/DC is measured against and the
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simulator implements — the two goals reinforce, not duplicate.
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- Every Tier-1 file gets a `drivers/<name>/test/` host harness (a `Makefile` +
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`test_<name>.c`) that calls the one shared `drivers/enforce-mcdc.sh` — which derives
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the driver name from the `.gcov` file, so there is a single gate to maintain, not a
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per-driver copy. The CI `mcdc` job auto-discovers any `drivers/*/test/Makefile` and
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fails below 100%.
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