Kestrel per-packet TX power: radiotap DBM_TX_POWER via fixed-dBm rewrite

[josephnef]

What

Per-packet TX power for the Kestrel generation (RTL8852BU/8832BU + RTL8852CU/8832CU) — the last family without a per-packet or fast power lever.

The AX WD descriptor carries no per-frame power field (both wd_body layouts; the vendor mac_ax tree has none either), so the descriptor-LUT/bank approach of the 11ac families doesn't apply. Instead this uses the cheapest power write in the tree: the fixed-dBm BB target (0x09a4[16] arm + 0x4594[30:22] s(9,2)) is 2 register RMWs at 0.25 dB resolution. Since Kestrel submits one bulk transfer per frame, send_packet now honours a radiotap DBM_TX_POWER dB-delta by rewriting that target between frames when the requested level changes:

• free while the value stays constant (change-detect against the hal offset member); 2 RMWs on a change
• a field-less frame restores the SetTxPowerOffsetQdb session offset
• clamped to the same 0..23 dBm PA window as the session lever, around the DEVOURER_TX_PWR base (whole dBm on this family)
• sticky across SetMonitorChannel/FastRetune for free — the hal offset member is the single source of truth and both re-apply paths already fold it
• global, like the Jaguar1 BB-swing lever: a HW beacon airing between frames follows the last-written level (documented)

Plumbing:

• AdapterCaps: per_packet_txpower=true, per_pkt_txpwr_steps=0 (continuous), step_qdb=1 (0.25 dB), min/max from the PA window, measured=true
• DEVOURER_TX_PKT_OFSET fans out to Kestrel too (nominal LUT dB onto the session fixed-dBm offset; radiotap still overrides per frame) — the shared on-air harness drives Kestrel DUTs unchanged
• tests/txpkt_pwr_ofset_onair.sh gains a TX_PWR knob (Kestrel reads DEVOURER_TX_PWR as dBm — the Jaguar-index default 40 would clamp; TX_PWR=14 gives the ±sweep headroom)

Validation

On-air, ch36, MCS3, 14 dBm base, 8822BU chip-RSSI ground, windowed medians:

DUT	LUT-mapped cells	Radiotap per-packet cells	Tracking
8852BU	5/5	2/2	+3→+3, +6→+6 exact; deep cuts over-deliver ~3 raw at the uncalibrated low-dBm end
8832CU	5/5	2/2	near-exact: +3→+3, +6→+6, −3→−3, −7→−6, −11→−10

Headless: full ctest 27/27; kestrel-only subset config builds and passes 26/26.

With this, every supported generation has a validated per-packet or fast TX-power lever.

🤖 Generated with Claude Code