The XUSB `packet` publish and the XUSB `rumble_seq` / DualSense `out_seq` reads
used plain unaligned accesses with no fence, so a driver could observe a bumped
change-detect field over a torn body on a weakly-ordered core (ARM64). Publish
`packet` via a Release AtomicU32 store behind a Release fence, and Acquire-load
the seq fields, mirroring the gamepad_raii PadChannel seq-fence precedent. The
DualSense input report embeds its seq mid-report with no driver-gated
change-detect field, so it gets a Release fence after the copy and a documented
residual (a per-frame input generation is deferred). No-op on x86-TSO.
Verified: Windows .173 `cargo clippy -p punktfunk-host --all-targets -- -D warnings` (green).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
enricobuehler
1af11cc64d