BFE Engineering
42fb386f60
Replace every em dash with real punctuation (rewrites, not hyphen swaps) in docs, code comments, scripts, configs, and the port records; convert en dashes, curly quotes, ellipsis glyphs, arrows, and section signs to ASCII; drop machine-writing tell phrases from living docs. ADR titles now use a colon. The M2 bring-up DTS model string carried an em dash into the patch series and its record echoes; fixed at both, and the full series re-verified to apply cleanly onto pristine 6.18.46. One comment in freshness.h deliberately names the em dash glyph the UI renders as the unknown mark; that is data, kept as prose naming it. Verified: cargo tests (sim, config-lint, rs485-bridge), shellcheck, both driver MC/DC harnesses, patches-apply.
1.7 KiB
1.7 KiB
ADR 0002: Tiered MC/DC
Status: Accepted (2026-08-25).
Context
The goal "port + harden 100% of drivers to 100% MC/DC" is infeasible as literally stated: ~97% of driver LOC is vendor blobs (the AIC8800 wifi driver alone is 88.5K lines) that we cannot meaningfully unit-test to MC/DC on the host. Forcing MC/DC on that code would be theatre, not assurance.
Decision
A two-tier policy, measured against the Hardware Abstraction Seam:
- Tier 1, our own hardware-facing code -> real 100% MC/DC.
modbus_engine.c,relays.c,warden_rga.c(wrapper),hpmcu.rs,devmem.rs,freshness.c, plus the two smallest near-mainline drivers where feasible. Enforced in CI (gcc-14 -fcondition-coverage+gcov-14 --conditions). Rust usescargo-llvm-covline/region coverage for now; true--mcdcneeds a nightly toolchain (-Z coverage-options=condition) and is deferred on that tooling skew; the C drivers carry the literal MC/DC gate. - Tier 2, ported/vendor drivers -> fault-injection + branch coverage + benchmarks against the simulator, behind a stable seam. Explicitly NOT literal MC/DC.
Consequences
- Matches the user's framing: "as many drivers as possible at 100% MC/DC; for the rest, a very serious testing and benchmarking system."
- The seam is the shared object: the same thing MC/DC is measured against and the simulator implements; the two goals reinforce, not duplicate.
- Every Tier-1 file gets a
drivers/<name>/test/host harness (aMakefile+test_<name>.c) that calls the one shareddrivers/enforce-mcdc.sh, which derives the driver name from the.gcovfile, so there is a single gate to maintain, not a per-driver copy. The CImcdcjob auto-discovers anydrivers/*/test/Makefileand fails below 100%.