Report diagnostics ownership¶

Status: implemented and software-tested, 2026-09-02. This is not a hardware latency measurement or a claim that every legacy report callee is nonblocking.

Boundary¶

All physical-controller/virtual-output combinations entering the canonical ControlService.On_Report path defer its direct device-error, lag-log, first-profile, startup-summary and tray-battery diagnostics. Mapping, virtual submission, synthetic input commit and lightbar state updates remain on the existing path. The primary path publishes diagnostics after those operations. A secondary joined controller publishes its own diagnostics before its early return, after any existing secondary gyro mapping.

The worker never queues or coalesces canonical input. Only optional diagnostics are latest-value observations. Error/lag/profile/startup updates within a facet can be coalesced while logging is slow; this is not a lossless diagnostic log. Startup details are one deferred summary, not inline per-stage formatted logs.

Identity and ownership¶

Cold registration creates one ReportDiagnosticsWorker.Source for an exact controller lifetime. Legacy report/removal delegates capture it. Typed legacy bindings also retain it for exact handler detachment and retirement. Switch 2's full-token authenticated reversible StageRecord owns it and passes it to the same canonical mapper; terminal publication and cleanup retire that exact handle. No report-time slot/device lookup grants a new source to an old callback.

Registering a successor revokes the old source, including same-device-object ABA reuse. Retiring an old source uses compare/exchange and cannot remove a successor. Pause revokes every handle; Resume permits new registrations but does not revive any old handle. Diagnostics availability is optional to Switch 2 canonical preparation/dispatch and registration failures are counted.

Each source has three preallocated value buffers. A serialized producer and single worker exchange buffer ownership. Neither reads the other's writable buffer. Snapshots retain immutable string references, scalar observations and exact source identity, not a borrowed mutable DS4State. Accidental concurrent producers are rejected/counted rather than serialized behind a monitor.

Producer-owned cumulative facet revisions and consumer delivery cursors ensure that an initial-profile observation survives later battery/startup coalescing without replaying on every subsequent publication. Initial battery and current battery are distinct; lag-event latency and startup latency are distinct. Unchanged battery observations do not wake the worker, but a tray-icon policy revision re-arms an unchanged percentage when returning to battery mode. Switch 2 uses its runtime's compatibility battery, not the unpopulated legacy state battery field; percentages remain the existing compatibility bands, not newly inferred charge measurements.

Teardown and UI¶

No report-side monitor, formatting, filesystem probe, logger or UI callback is used by this diagnostics lane. Cold lifecycle transitions use a short lock, but no callback runs under it. Pause, exact retirement and Dispose never wait for the worker's logging/UI callback. Dispose is idempotent and does not join itself. Active publisher accounting and worker exit jointly govern wake-event disposal. Dispatch and failure-logger exceptions cannot kill the consumer.

Already-admitted historical logs may finish after retirement; they cannot be recalled. Pending stale sources are rejected. Battery events carry the exact source through the UI queue, and the tray checks both its validity and current icon policy when the dispatcher executes the action.

Verification and limits¶

ReportDiagnosticsWorkerTests covers facet revisions, initial/current battery, independent latencies, source replacement/ABA, pause/resume, slot independence, blocked dispatch, shutdown and active-publisher races, failure recovery, dispose-from-dispatch, zero managed allocation in a warmed producer and coherent concurrent snapshots/final delivery. Integration tests exercise the actual secondary On_Report return, Switch 2 canonical host admission/terminal/cleanup, optional-observer refusal, runtime battery capture and stale tray callbacks.

The final full default-runtime suite passed 2,949 tests, with 3 opt-in live-audio skips (report-diagnostics-full-20260902.trx). This does not establish physical latency, Bluetooth reliability, game compatibility, haptic/LED onset or the unrun production matrix. Legacy touch-toggle/mapping-action notifications, other physical-device events, legacy DSU and OSC lifecycle paths remain separate audit boundaries; this change does not certify the complete transitive callback.