GetTxCaps + STBC-on-1T1R guard — stop airing malformed frames#197
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The adaptive-link recipes flag a real footgun: "LDPC/STBC forced on a card that
lacks them => link dies" (8811AU/8821AU/8821CU are 1T1R; STBC needs >=2 TX
chains). devourer set the STBC descriptor bit unconditionally from the radiotap
flag, even on 1T1R parts, producing a PPDU that never decodes.
Measured A/B on the 8821AU (MCS1/STBC): forcing STBC delivered 0 frames; with
the guard (STBC dropped to clean MCS1) it delivered 7000. Real correctness fix,
not just defensive.
- src/TxCaps.h — devourer::TxCaps {n_ss, stbc_ok, ldpc_ok, sgi_ok, bw_max_mhz}
+ tx_caps_for_chains() (the load-bearing rule: stbc_ok = chains >= 2).
- IRtlDevice::GetTxCaps() default; per-family override from the chip identity
devourer already resolves (Jaguar1 EepromManager numTotalRfPath; Jaguar2
ChipVariant C8821C=1T1R vs C8822B=2T2R; Jaguar3 8822C/E 2T2R).
- send_packet drops STBC + warns once when !stbc_ok (each family; a no-op on
2T2R/4T4R, byte-identical when STBC isn't requested).
Validated: TxCapsSelftest (ctest + mingw list) on the chains->caps rule;
tests/stbc_1t1r_check.sh 4/4 on-air — 8821AU + 8821CU (1T1R) drop STBC and
deliver (6500/6000 hits) with the warning; 8812AU + 8822BU (2T2R) honour STBC,
no warning, deliver. Full build + J1-only subset green.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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Why
From
/tmp/adaptive-link-recipes.md(§10 pitfalls): "LDPC/STBC forced on a card that lacks them → link dies" — the 8811AU/8821AU/8821CU are 1T1R, and STBC needs ≥2 TX chains. devourer set the STBC descriptor bit unconditionally from the radiotap flag, even on 1T1R parts, producing a PPDU that never decodes.Measured — it's a real delivery bug, not just spec-illegal
A/B on the 8821AU injecting
MCS1/STBC, second-adapter delivery count:The recipe's "link dies" is literal.
What
src/TxCaps.h—devourer::TxCaps {n_ss, stbc_ok, ldpc_ok, sgi_ok, bw_max_mhz}+tx_caps_for_chains()(the load-bearing rule:stbc_ok = chains >= 2).IRtlDevice::GetTxCaps()default + per-family override from the chip identity devourer already resolves: Jaguar1EepromManagernumTotalRfPath, Jaguar2ChipVariant(C8821C 1T1R vs C8822B 2T2R), Jaguar3 8822C/E 2T2R.send_packetdrops STBC + warns once when!stbc_ok(each family). A no-op on 2T2R/4T4R; byte-identical when STBC isn't requested.Validation
ctest+ mingw list):TxCapsSelftest— thechains → {n_ss, stbc_ok}rule (1T1R→no STBC, 2T2R/4T4R→STBC ok).tests/stbc_1t1r_check.sh): 4/4 — 8821AU + 8821CU (1T1R) drop STBC and deliver (6500/6000 hits) with the warning; 8812AU + 8822BU (2T2R) honour STBC, no warning, deliver.Full all-chips build + J1-only subset green.
GetTxCapsalso gives an adaptive controller a clean way to query STBC/LDPC/n_ss/bw before requesting a feature.🤖 Generated with Claude Code