Four fixes, each a root cause verified on hardware (AX211 + Bose QC Ultra):
1. Link Key Request Reply TRUNCATED: the pending-command queue's params
buffer was 16 bytes; the reply is 22 (addr 6 + key 16). The controller
got 10 key bytes -> every stored-key reconnection failed authentication
(status 5) since 2026-06-03 (0f16785). Fresh pairings never touch this
path, which kept the bug perfectly disguised as a headset quirk.
2. Secure Connections host support (0x0C7A) now enabled: bonds are minted
as P-256 (Type=7), interoperable with BlueZ's, and SC-bonded peers can
actually authenticate us.
3. Never write the BD_ADDR override (0xFC31) with the factory address:
it desyncs the firmware's crypto address from the on-air one and ALL
SSP pairing fails with status 5. (The spoofing feature itself was
already known-cosmetic: the baseband answers pages on the factory
address regardless.) import-bluez-bond.sh now removes the override.
4. A2DP channel setup: wait for Encryption Change before dialing L2CAP
(post-SSP sinks ignore unencrypted CONN_REQ), and LISTEN 2.5s first --
on reconnection the sink dials AVDTP itself and ignores our dials while
doing so. Ends the historical connRsp=FFFF retry-then-give-up failures.
Plus: queued security replies now log delivery + controller status.
Co-Authored-By: Claude Fable 5 <[email protected]>
Deferring the Intel BT firmware download off the boot path made the AX211
bootloader stop answering after the first FC05; even the final synchronous
revert freezes boot, so one of the 'neutral' fixes kept in this diff breaks
the bring-up on its own (candidates: BT-TRACE logging inside TransferCallback,
unconditional interrupt-IN re-queue after error completions on a halted EP,
xHCI interrupt-IN ZLP len fix interacting with HID, InPollContext owner
check). Full history + next experiments in memory notes, 2026-07-05/06.
Co-Authored-By: Claude Fable 5 <[email protected]>
daniel
