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Improve Bluetooth credit handling and Switch 2 connection timing

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Joey Yakimowich-Payne 2026-09-09 10:40:25 -06:00
commit 7c1c37a84e
13 changed files with 408 additions and 71 deletions
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HAPTICS_EXPERIMENT.md
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@ -307,6 +307,37 @@ profiles were compared with the pre-migration backup; the temporary editor
profile and name were restored. No configuration, bond, or wake-identity reset
was part of the transport work.
### Dedicated receive-credit buffer
`SWITCH_PICO_HCI_CREDIT_BUFFER` defaults to the credit-batching setting, so normal
AIO and automatic Switch/XInput builds enable it. Setting it to `OFF` retains
the original batched/shared-buffer path for A/B comparisons. Enabling it requires
credit batching; UART defaults remain unchanged.
The HCI patch uses a separate 24-byte, word-aligned buffer with the current
four-connection configuration, including CYW43's four-byte transport header.
Ready receive-credit commands precede pending ACL continuations without bypassing
transport readiness or an in-flight fragment. Their completion releases only
the credit buffer. Transfer ownership survives batching cancellation until
completion or transport close. A send returning after stack reinitialization
cannot release the new stack's buffer.
A native probe delivered three incoming packets while the outgoing buffer
remained reserved. At 20 ms, the shared path retained all three receive credits;
the dedicated path had returned all three in two commands without releasing
the outgoing buffer. Regressions cover mixed BLE input/Classic fragmentation,
synchronous, delayed and CYW43-style inline completion, buffer lifetime, sleep,
power-cycle recovery and the unchanged default/shared paths. AddressSanitizer
and UndefinedBehaviorSanitizer also passed.
The automatic-mode image was flashed and verified on hardware. Configuration
generation 21 / CRC `b58672ac`, all nine pairings, the profile catalog and active
profile selections were unchanged. Two controllers supplied input, but the
DualSense native stream hit its can-send timeout both with this change and with
the previous packaged firmware. The host-side blockage is fixed; no radio,
native-stream reliability or physical latency improvement is established by
that comparison.
### Historical mixed-controller cadence limit
Final testing with a Switch Pro plus a DualSense and continuous USB motion