nt-lite/code/kernel/ke_audio.c

// Kernel audio core. This file owns endpoint identity, logical streams, mixing, and provider timing handoff.

#include <intrin.h>
#include <stdint.h>
#include <stddef.h>
#include <string.h>

#include <ntlite/ddi/io_driver.h>
#include <ntlite/ddk/audio.h>
#include <kernel/ke_audio.h>
#include <kernel/ke_id.h>
#include <kernel/ke_debug.h>
#include <kernel/ke_event.h>
#include <kernel/ke_list.h>
#include <kernel/ke_mutex.h>
#include <kernel/ke_sched.h>
#include <kernel/ke_spinlock.h>
#include <kernel/ke_thread.h>
#include <kernel/ke_time.h>
#include <kernel/mm_pool.h>
#include <kernel/mm_virt.h>
#include <kernel/ob_object.h>

#define KE_AUDIO_ENDPOINT_TAG MM_POOL_TAG('a', 'e', 'p', 't')
#define KE_AUDIO_RING_TAG     MM_POOL_TAG('a', 'r', 'n', 'g')

#define KE_AUDIO_PERIOD_STATE_FREE      0u
#define KE_AUDIO_PERIOD_STATE_FILLING   1u
#define KE_AUDIO_PERIOD_STATE_READY     2u
#define KE_AUDIO_PERIOD_STATE_COMPLETED 3u
#define KE_AUDIO_PERIOD_STATE_REAPING   4u

#define KE_AUDIO_TICKS_PER_MILLISECOND       1000ull

typedef struct KE_AUDIO_PERIOD_CONTRIBUTION {
    KE_AUDIO_STREAM* Stream;
    uint64_t StreamGeneration;
    uint32_t SourceFrames;
} KE_AUDIO_PERIOD_CONTRIBUTION;

typedef struct KE_AUDIO_PERIOD_STATE {
    uint64_t Generation;
    uint32_t ContributionCount;
    uint8_t State;
    KE_AUDIO_PERIOD_CONTRIBUTION Contributions[KE_AUDIO_MAX_STREAMS_PER_ENDPOINT];
} KE_AUDIO_PERIOD_STATE;

struct KE_AUDIO_STREAM {
    OBJECT Header;
    MUTEX* Lock;
    EVENT* WaitEvent;
    LIST_ENTRY EndpointLink;
    IO_AUDIO_ENDPOINT* Endpoint;
    KE_AUDIO_STREAM_STATE State;
    volatile long ProcessHandleCount;
    volatile long CloseRequested;
    IO_AUDIO_FORMAT Format;
    uint8_t* Ring;
    uint32_t FrameBytes;
    uint32_t ReadFrame;
    uint32_t WriteFrame;
    uint32_t BufferedFrames;
    uint64_t ResamplePositionQ32;
    uint64_t ResampleStepQ32;
    uint64_t FramesSubmitted;
    uint64_t FramesConsumed;
    uint64_t FramesPresented;
    uint64_t FramesDiscarded;
    uint64_t OutputFramesMixed;
    uint64_t SilenceFramesInserted;
    uint64_t Underruns;
    uint64_t ConsecutiveUnderrunPeriods;
    uint64_t DrainedGeneration;
    uint64_t DiscontinuityGeneration;
    uint64_t BufferGeneration;
    KSTATUS FailureStatus;
    uint32_t WaitMask;
    uint32_t WaitWritableFrames;
    uint64_t WaitConsumedFrames;
    uint64_t WaitPresentedFrames;
    uint64_t WaitDrainedGeneration;
    uint64_t WaitDiscontinuityGeneration;
    float Volume;
    float Pan;
    uint8_t Muted;
    float CurrentLeftGain;
    float CurrentRightGain;
    float TargetLeftGain;
    float TargetRightGain;
    float LeftGainStep;
    float RightGainStep;
    uint32_t GainRampRemaining;
};

struct IO_AUDIO_ENDPOINT {
    OBJECT Header;
    LIST_ENTRY RegistryLink;
    LIST_ENTRY StreamList;
    SPINLOCK StreamListLock;
    MUTEX* ControlLock;
    EVENT* WorkEvent;
    EVENT* MixerExitEvent;
    THREAD* MixerThread;
    SPINLOCK NotifyLock;
    uint32_t EndpointId;
    IO_AUDIO_ENDPOINT_KIND Kind;
    KE_AUDIO_ENDPOINT_STATE State;
    uint32_t Capabilities;
    uint8_t Available;
    uint8_t Registered;
    uint8_t HardwareRunning;
    uint8_t SkipProviderStop;
    IO_AUDIO_REMOVAL_MODE RemovalMode;
    DEVICE_OBJECT* Device;
    void* ProviderContext;
    IO_AUDIO_PROVIDER_OPERATIONS Operations;
    uint8_t* PeriodBuffer;
    size_t PeriodBufferBytes;
    uint32_t PeriodCount;
    uint32_t FramesPerPeriod;
    size_t PeriodStrideBytes;
    IO_AUDIO_FORMAT HardwareFormat;
    int32_t HardwareGainMinimumMilliDb;
    int32_t HardwareGainMaximumMilliDb;
    uint32_t HardwareGainStepMilliDb;
    KE_AUDIO_PERIOD_STATE Periods[KE_AUDIO_OUTPUT_PERIOD_COUNT];
    uint32_t ActiveStreamCount;
    uint64_t IdleDeadlineTicks;
    float MasterCurrentGain;
    float MasterTargetGain;
    float MasterRequestedVolume;
    int32_t MasterHardwareGainMilliDb;
    float MasterGainStep;
    uint32_t MasterRampRemaining;
    uint64_t MasterGainGeneration;
    uint8_t MasterMuted;
    KSTATUS FailureStatus;
    uint64_t PeriodsMixed;
    uint64_t PeriodsCompleted;
    uint64_t FramesPresented;
    uint64_t HardwarePositionFrames;
    uint64_t InterruptCount;
    uint64_t LastPresentationTimestampTicks;
    uint64_t SilenceFramesInserted;
    uint64_t Underruns;
    uint64_t DiscontinuityGeneration;
    uint64_t HardwareStarts;
    uint64_t HardwareStops;
    uint64_t SpuriousNotifications;
    uint64_t PendingDiscontinuities;
};

typedef struct KE_AUDIO_CORE_STATS {
    volatile long long EndpointsRegistered;
    volatile long long EndpointsUnregistered;
    volatile long long StreamsCreated;
    volatile long long StreamsDestroyed;
    volatile long long Starts;
    volatile long long Stops;
    volatile long long Pauses;
    volatile long long Resumes;
    volatile long long Drains;
    volatile long long Resets;
} KE_AUDIO_CORE_STATS;

typedef struct KE_AUDIO_LIFECYCLE_SNAPSHOT {
    KE_AUDIO_ENDPOINT_STATE State;
    KSTATUS FailureStatus;
    IO_AUDIO_REMOVAL_MODE RemovalMode;
    uint8_t SkipProviderStop;
} KE_AUDIO_LIFECYCLE_SNAPSHOT;

static SPINLOCK gAudioRegistryLock = SPINLOCK_INIT;
static LIST_ENTRY gAudioEndpointList;
static uint32_t gAudioEndpointCount;
static KE_ID_ALLOCATOR gAudioEndpointIds = KE_ID_ALLOCATOR_INIT(1u);
static uint32_t gAudioDefaultEndpointId;
static uint8_t gAudioInitialized;
static KE_AUDIO_CORE_STATS gAudioCoreStats;

// Stops on one violated internal audio invariant.
static void KiAudioBug(const char* where, const char* reason, uint64_t value) {
    KePanic(KE_PANIC_CODE_GENERIC,
            "audio invariant failed: %s: %s value=0x%016llX\n",
            where ? where : "?",
            reason ? reason : "?",
            (unsigned long long)value);
}

// Acquires an internal mutex and rejects abandoned ownership as kernel corruption.
static void KiAudioAcquireMutex(MUTEX* mutex, const char* where) {
    KSTATUS status = KeAcquireMutex(mutex, KE_WAIT_INFINITE);
    if (status != NTLSTATUS_SUCCESS)
        KiAudioBug(where, "internal mutex acquisition failed", status);
}

// Releases one internal mutex.
static void KiAudioReleaseMutex(MUTEX* mutex) {
    KeReleaseMutex(mutex);
}

// Returns the provider timer in microseconds when available.
static uint64_t KiAudioQueryTicks(void) {
    return KeQueryMonotonicTicks();
}

// Returns whether one float is finite without depending on a runtime math library.
static int KiAudioFloatIsFinite(float value) {
    union {
        float Float;
        uint32_t Bits;
    } bits;
    bits.Float = value;
    return (bits.Bits & 0x7F800000u) != 0x7F800000u;
}

// Clamps one mixer sample to the signed unit interval.
static float KiAudioClampSample(float value) {
    const float maximum = 0.99999988079071044921875f;
    if (value > maximum) return maximum;
    if (value < -1.0f) return -1.0f;
    return value;
}

// Converts one normalized mixer sample to signed 16-bit PCM.
static int16_t KiAudioFloatToOutputSample(float value) {
    float scaled = KiAudioClampSample(value) * 32768.0f;
    int32_t sample = scaled >= 0.0f ? (int32_t)(scaled + 0.5f)
                                    : (int32_t)(scaled - 0.5f);
    if (sample > 32767) sample = 32767;
    if (sample < -32768) sample = -32768;
    return (int16_t)sample;
}

// Approximates one linear gain as milli-decibels without a runtime math dependency.
static int32_t KiAudioMilliDbFromLinearGain(float gain) {
    if (gain <= 0.0f)
        return INT32_MIN;

    union {
        float Float;
        uint32_t Bits;
    } bits;
    bits.Float = gain;
    uint32_t encodedExponent = (bits.Bits >> 23) & 0xFFu;
    uint32_t fraction = bits.Bits & 0x007FFFFFu;
    int32_t exponent = 0;
    if (encodedExponent) {
        exponent = (int32_t)encodedExponent - 127;
    } else {
        exponent = -126;
        while ((fraction & 0x00800000u) == 0) {
            fraction <<= 1;
            exponent--;
        }
        fraction &= 0x007FFFFFu;
    }
    bits.Bits = fraction | 0x3F800000u;
    float mantissa = bits.Float;
    float y = (mantissa - 1.0f) / (mantissa + 1.0f);
    float y2 = y * y;
    float logarithm = 2.0f * y *
        (1.0f + y2 * (0.3333333333333333f +
        y2 * (0.2f + y2 * (0.1428571428571429f + y2 * 0.1111111111111111f))));
    float log2Gain = (float)exponent + logarithm * 1.4426950408889634f;
    float milliDb = log2Gain * 6020.599913279624f;
    return milliDb >= 0.0f ? (int32_t)(milliDb + 0.5f)
                           : (int32_t)(milliDb - 0.5f);
}

// Approximates one nonpositive milli-decibel residual as a linear gain.
static float KiAudioLinearGainFromMilliDb(int32_t milliDb) {
    if (milliDb >= 0)
        return 1.0f;
    float exponent = (float)milliDb * (1.0f / 6020.599913279624f);
    int32_t whole = (int32_t)exponent;
    if ((float)whole > exponent)
        whole--;
    float fraction = exponent - (float)whole;
    float z = fraction * 0.6931471805599453f;
    float z2 = z * z;
    float result = 1.0f + z + z2 * 0.5f + z2 * z * (1.0f / 6.0f) +
                   z2 * z2 * (1.0f / 24.0f) + z2 * z2 * z * (1.0f / 120.0f);
    while (whole < 0) {
        result *= 0.5f;
        whole++;
    }
    while (whole > 0) {
        result *= 2.0f;
        whole--;
    }
    return result;
}

// Chooses the highest supported nonpositive hardware gain.
static int32_t KiAudioHighestSafeHardwareGain(const IO_AUDIO_ENDPOINT* endpoint) {
    if (!(endpoint->Capabilities & IO_AUDIO_ENDPOINT_CAP_HARDWARE_GAIN) ||
        !endpoint->Operations.SetGain)
        return 0;

    int32_t minimum = endpoint->HardwareGainMinimumMilliDb;
    int32_t maximum = endpoint->HardwareGainMaximumMilliDb;
    int64_t step = endpoint->HardwareGainStepMilliDb;
    if (maximum <= 0)
        return maximum;
    int64_t steps = ((int64_t)0 - minimum) / step;
    return (int32_t)((int64_t)minimum + steps * step);
}

// Converts one requested master volume into software gain for the stable hardware gain.
static float KiAudioSoftwareGainForVolume(const IO_AUDIO_ENDPOINT* endpoint,
                                          float requestedVolume) {
    if (requestedVolume <= 0.0f)
        return 0.0f;
    if (!(endpoint->Capabilities & IO_AUDIO_ENDPOINT_CAP_HARDWARE_GAIN) ||
        !endpoint->Operations.SetGain)
        return requestedVolume;
    int32_t requestedMilliDb = KiAudioMilliDbFromLinearGain(requestedVolume);
    int64_t residualMilliDb = (int64_t)requestedMilliDb -
                              endpoint->MasterHardwareGainMilliDb;
    if (residualMilliDb > 0)
        residualMilliDb = 0;
    if (residualMilliDb < -IO_AUDIO_HARDWARE_GAIN_LIMIT_MILLIDB)
        return 0.0f;
    return KiAudioLinearGainFromMilliDb((int32_t)residualMilliDb);
}

// Returns the byte width of one source frame.
static uint32_t KiAudioFrameBytes(const IO_AUDIO_FORMAT* format) {
    if (!format) return 0;
    if (format->SampleFormat != IoAudioSampleS16) return 0;
    return 2u * format->ChannelCount;
}

// Validates one logical source format accepted by the first mixer contract.
static int KiAudioValidateSourceFormat(const IO_AUDIO_FORMAT* format) {
    if (!format) return 0;
    if (format->ChannelCount != 1 && format->ChannelCount != 2)
        return 0;
    if (format->SampleFormat != IoAudioSampleS16)
        return 0;
    return format->SampleRate == 11025u ||
           format->SampleRate == 22050u ||
           format->SampleRate == 44100u ||
           format->SampleRate == 48000u;
}

// Validates the fixed endpoint ring contract used by the HDA provider series.
static KSTATUS KiAudioValidateRegistration(
    const IO_AUDIO_ENDPOINT_REGISTRATION* registration) {
    if (!registration || !registration->PeriodBuffer)
        return NTLSTATUS_INVALID_PARAMETER;
    if (!registration->Device)
        return NTLSTATUS_INVALID_PARAMETER;
    if (registration->Kind < IoAudioEndpointLineOut ||
        registration->Kind > IoAudioEndpointOtherAnalog ||
        (registration->Capabilities & ~IO_AUDIO_ENDPOINT_CAP_VALID_MASK) != 0)
        return NTLSTATUS_INVALID_PARAMETER;
    if (!registration->Operations.Start || !registration->Operations.Stop)
        return NTLSTATUS_INVALID_PARAMETER;
    if (registration->HardwareFormat.SampleRate != KE_AUDIO_OUTPUT_SAMPLE_RATE ||
        registration->HardwareFormat.ChannelCount != KE_AUDIO_OUTPUT_CHANNELS ||
        registration->HardwareFormat.SampleFormat != IoAudioSampleS16)
        return NTLSTATUS_NOT_SUPPORTED;
    if (registration->PeriodCount != KE_AUDIO_OUTPUT_PERIOD_COUNT ||
        registration->FramesPerPeriod != KE_AUDIO_OUTPUT_FRAMES_PER_PERIOD ||
        registration->PeriodStrideBytes != KE_AUDIO_OUTPUT_PERIOD_BYTES)
        return NTLSTATUS_NOT_SUPPORTED;
    if (registration->PeriodBufferBytes <
        registration->PeriodStrideBytes * registration->PeriodCount)
        return NTLSTATUS_BUFFER_TOO_SMALL;
    if (((uintptr_t)registration->PeriodBuffer & (sizeof(uint32_t) - 1u)) != 0)
        return NTLSTATUS_INVALID_PARAMETER;
    if ((registration->Capabilities & IO_AUDIO_ENDPOINT_CAP_HARDWARE_GAIN) != 0) {
        if (!registration->Operations.SetGain || !registration->HardwareGainStepMilliDb ||
            registration->HardwareGainStepMilliDb > INT32_MAX ||
            registration->HardwareGainMinimumMilliDb > registration->HardwareGainMaximumMilliDb ||
            registration->HardwareGainMinimumMilliDb > 0 ||
            registration->HardwareGainMinimumMilliDb < -IO_AUDIO_HARDWARE_GAIN_LIMIT_MILLIDB ||
            registration->HardwareGainMaximumMilliDb > IO_AUDIO_HARDWARE_GAIN_LIMIT_MILLIDB ||
            ((int64_t)registration->HardwareGainMaximumMilliDb -
             registration->HardwareGainMinimumMilliDb) %
                registration->HardwareGainStepMilliDb != 0)
            return NTLSTATUS_INVALID_PARAMETER;
    } else if (registration->Operations.SetGain ||
               registration->HardwareGainMinimumMilliDb ||
               registration->HardwareGainMaximumMilliDb ||
               registration->HardwareGainStepMilliDb) {
        return NTLSTATUS_INVALID_PARAMETER;
    }
    return NTLSTATUS_SUCCESS;
}

// Returns whether one endpoint lifecycle transition is valid.
static int KiAudioEndpointTransitionAllowed(KE_AUDIO_ENDPOINT_STATE oldState,
                                            KE_AUDIO_ENDPOINT_STATE newState) {
    if (oldState == newState)
        return 1;
    switch (oldState) {
    case KeAudioEndpointStarting:
        return newState == KeAudioEndpointReady ||
               newState == KeAudioEndpointStopping;
    case KeAudioEndpointReady:
        return newState == KeAudioEndpointStopping ||
               newState == KeAudioEndpointFailed;
    case KeAudioEndpointFailed:
        return newState == KeAudioEndpointStopping;
    case KeAudioEndpointStopping:
        return newState == KeAudioEndpointRemoved;
    case KeAudioEndpointRemoved:
        return 0;
    default:
        return 0;
    }
}

// Changes one endpoint state while the registry lock serializes lifecycle ownership.
static void KiAudioSetEndpointStateLocked(IO_AUDIO_ENDPOINT* endpoint,
                                          KE_AUDIO_ENDPOINT_STATE newState) {
    if (!KiAudioEndpointTransitionAllowed(endpoint->State, newState))
        KiAudioBug("KiAudioSetEndpointStateLocked", "invalid endpoint transition",
                   ((uint64_t)endpoint->State << 32) | (uint32_t)newState);
    endpoint->State = newState;
}

// Returns the fixed endpoint preference rank used until policy moves to a service.
static uint32_t KiAudioEndpointRank(IO_AUDIO_ENDPOINT_KIND kind) {
    if (kind == IoAudioEndpointLineOut) return 0;
    if (kind == IoAudioEndpointSpeakerHeadphone) return 1;
    return 2;
}

// Recomputes the default endpoint while the registry lock is held.
static void KiAudioSelectDefaultEndpointLocked(void) {
    uint32_t selectedId = 0;
    uint32_t selectedRank = UINT32_MAX;
    for (LIST_ENTRY* link = gAudioEndpointList.Fwd;
         link != &gAudioEndpointList;
         link = link->Fwd) {
        IO_AUDIO_ENDPOINT* endpoint = CONTAINING_RECORD(link, IO_AUDIO_ENDPOINT, RegistryLink);
        if (endpoint->State != KeAudioEndpointReady || !endpoint->Available)
            continue;
        uint32_t rank = KiAudioEndpointRank(endpoint->Kind);
        if (!selectedId || rank < selectedRank ||
            (rank == selectedRank && endpoint->EndpointId < selectedId)) {
            selectedId = endpoint->EndpointId;
            selectedRank = rank;
        }
    }
    gAudioDefaultEndpointId = selectedId;
}

// References one ready endpoint by stable identifier.
static IO_AUDIO_ENDPOINT* KiAudioReferenceEndpointById(uint32_t endpointId) {
    IO_AUDIO_ENDPOINT* result = (IO_AUDIO_ENDPOINT*)0;
    uintptr_t flags = KeAcquireSpinlock(&gAudioRegistryLock);
    for (LIST_ENTRY* link = gAudioEndpointList.Fwd;
         link != &gAudioEndpointList;
         link = link->Fwd) {
        IO_AUDIO_ENDPOINT* endpoint = CONTAINING_RECORD(link, IO_AUDIO_ENDPOINT, RegistryLink);
        if (endpoint->EndpointId != endpointId)
            continue;
        if (endpoint->State == KeAudioEndpointReady && ObTryReferenceObject(&endpoint->Header))
            result = endpoint;
        break;
    }
    KeReleaseSpinlock(&gAudioRegistryLock, flags);
    return result;
}

// Signals one stream when an armed progress condition or terminal state is present.
static void KiAudioRefreshStreamEventLocked(KE_AUDIO_STREAM* stream) {
    uint32_t writableFrames = KE_AUDIO_STREAM_RING_FRAMES - stream->BufferedFrames;
    int signaled = stream->State == KeAudioStreamFailed ||
                   stream->State == KeAudioStreamClosed;
    if ((stream->WaitMask & KE_AUDIO_WAIT_WRITABLE) &&
        writableFrames >= stream->WaitWritableFrames)
        signaled = 1;
    if ((stream->WaitMask & KE_AUDIO_WAIT_CONSUMED) &&
        stream->FramesConsumed >= stream->WaitConsumedFrames)
        signaled = 1;
    if ((stream->WaitMask & KE_AUDIO_WAIT_PRESENTED) &&
        stream->FramesPresented >= stream->WaitPresentedFrames)
        signaled = 1;
    if ((stream->WaitMask & KE_AUDIO_WAIT_STOPPED) &&
        stream->State == KeAudioStreamStopped)
        signaled = 1;
    if ((stream->WaitMask & KE_AUDIO_WAIT_DRAINED) &&
        stream->DrainedGeneration != stream->WaitDrainedGeneration)
        signaled = 1;
    if ((stream->WaitMask & KE_AUDIO_WAIT_FAILED) &&
        stream->State == KeAudioStreamFailed)
        signaled = 1;
    if ((stream->WaitMask & KE_AUDIO_WAIT_DISCONTINUITY) &&
        stream->DiscontinuityGeneration != stream->WaitDiscontinuityGeneration)
        signaled = 1;
    if (signaled)
        KeSignalEvent(stream->WaitEvent);
    else
        KeClearEvent(stream->WaitEvent);
}

// Updates active-stream timing under the endpoint notification lock.
static void KiAudioAdjustActiveStreams(IO_AUDIO_ENDPOINT* endpoint, int delta) {
    uintptr_t flags = KeAcquireSpinlock(&endpoint->NotifyLock);
    uint32_t oldCount = endpoint->ActiveStreamCount;
    if (delta > 0) {
        endpoint->ActiveStreamCount += (uint32_t)delta;
        endpoint->IdleDeadlineTicks = 0;
    } else {
        uint32_t amount = (uint32_t)(-delta);
        if (oldCount < amount) {
            KeReleaseSpinlock(&endpoint->NotifyLock, flags);
            KiAudioBug("KiAudioAdjustActiveStreams", "active stream count underflow", oldCount);
        }
        endpoint->ActiveStreamCount -= amount;
        if (endpoint->ActiveStreamCount == 0) {
            uint64_t now = KiAudioQueryTicks();
            endpoint->IdleDeadlineTicks = now +
                (uint64_t)KE_AUDIO_IDLE_STOP_MILLISECONDS * KE_AUDIO_TICKS_PER_MILLISECOND;
        }
    }
    KeReleaseSpinlock(&endpoint->NotifyLock, flags);
    KeSignalEvent(endpoint->WorkEvent);
}

// Returns whether one stream state contributes to the active hardware clock.
static int KiAudioStreamStateIsActive(KE_AUDIO_STREAM_STATE state) {
    return state == KeAudioStreamRunning || state == KeAudioStreamDraining;
}

// Returns whether every frame targeted by one drain has reached a terminal disposition.
static int KiAudioDrainIsCompleteLocked(const KE_AUDIO_STREAM* stream) {
    return stream->BufferedFrames == 0 &&
           stream->FramesPresented + stream->FramesDiscarded >= stream->FramesSubmitted;
}

// Returns whether one logical stream transition is valid.
static int KiAudioStreamTransitionAllowed(KE_AUDIO_STREAM_STATE oldState,
                                          KE_AUDIO_STREAM_STATE newState) {
    if (oldState == newState)
        return 1;
    if (newState == KeAudioStreamFailed || newState == KeAudioStreamClosed)
        return oldState != KeAudioStreamClosed;
    switch (oldState) {
    case KeAudioStreamCreated:
        return newState == KeAudioStreamRunning ||
               newState == KeAudioStreamStopped;
    case KeAudioStreamRunning:
        return newState == KeAudioStreamPaused ||
               newState == KeAudioStreamDraining ||
               newState == KeAudioStreamStopped;
    case KeAudioStreamPaused:
        return newState == KeAudioStreamRunning ||
               newState == KeAudioStreamDraining ||
               newState == KeAudioStreamStopped;
    case KeAudioStreamDraining:
        return newState == KeAudioStreamStopped;
    case KeAudioStreamStopped:
        return newState == KeAudioStreamRunning;
    case KeAudioStreamFailed:
    case KeAudioStreamClosed:
    default:
        return 0;
    }
}

// Changes one stream state and updates endpoint activity in the same locked transaction.
static void KiAudioSetStreamStateLocked(KE_AUDIO_STREAM* stream,
                                        KE_AUDIO_STREAM_STATE newState) {
    if (!KiAudioStreamTransitionAllowed(stream->State, newState))
        KiAudioBug("KiAudioSetStreamStateLocked", "invalid stream transition",
                   ((uint64_t)stream->State << 32) | (uint32_t)newState);
    int oldActive = KiAudioStreamStateIsActive(stream->State);
    int newActive = KiAudioStreamStateIsActive(newState);
    stream->State = newState;
    if (oldActive != newActive)
        KiAudioAdjustActiveStreams(stream->Endpoint, newActive ? 1 : -1);
}

// Records one completed drain before publishing the stopped state.
static void KiAudioCompleteDrainLocked(KE_AUDIO_STREAM* stream) {
    if (stream->State != KeAudioStreamDraining || !KiAudioDrainIsCompleteLocked(stream))
        KiAudioBug("KiAudioCompleteDrainLocked", "incomplete drain reached completion", stream->State);
    stream->DrainedGeneration++;
    KiAudioSetStreamStateLocked(stream, KeAudioStreamStopped);
}

// Computes the target left and right gains for one volume, pan, and mute state.
static void KiAudioComputeStreamTargets(float volume,
                                        float pan,
                                        uint8_t muted,
                                        float* leftOut,
                                        float* rightOut) {
    float left = volume;
    float right = volume;
    if (pan > 0.0f)
        left *= 1.0f - pan;
    else if (pan < 0.0f)
        right *= 1.0f + pan;
    if (muted) {
        left = 0.0f;
        right = 0.0f;
    }
    *leftOut = left;
    *rightOut = right;
}

// Starts a ten-millisecond linear gain ramp while the stream mutex is held.
static void KiAudioBeginStreamGainRampLocked(KE_AUDIO_STREAM* stream) {
    KiAudioComputeStreamTargets(stream->Volume,
                                stream->Pan,
                                stream->Muted,
                                &stream->TargetLeftGain,
                                &stream->TargetRightGain);
    stream->GainRampRemaining = KE_AUDIO_GAIN_RAMP_FRAMES;
    stream->LeftGainStep =
        (stream->TargetLeftGain - stream->CurrentLeftGain) /
        (float)KE_AUDIO_GAIN_RAMP_FRAMES;
    stream->RightGainStep =
        (stream->TargetRightGain - stream->CurrentRightGain) /
        (float)KE_AUDIO_GAIN_RAMP_FRAMES;
}

// Advances one stream gain ramp by one output frame.
static void KiAudioAdvanceStreamGainLocked(KE_AUDIO_STREAM* stream) {
    if (!stream->GainRampRemaining)
        return;
    stream->CurrentLeftGain += stream->LeftGainStep;
    stream->CurrentRightGain += stream->RightGainStep;
    stream->GainRampRemaining--;
    if (!stream->GainRampRemaining) {
        stream->CurrentLeftGain = stream->TargetLeftGain;
        stream->CurrentRightGain = stream->TargetRightGain;
    }
}

// Decodes one interleaved source frame into normalized stereo samples.
static void KiAudioDecodeSourceFrame(const KE_AUDIO_STREAM* stream,
                                     uint32_t offset,
                                     float* leftOut,
                                     float* rightOut) {
    uint32_t index = (stream->ReadFrame + offset) % KE_AUDIO_STREAM_RING_FRAMES;
    const uint8_t* frame = stream->Ring + (size_t)index * stream->FrameBytes;
    float left = 0.0f;
    float right = 0.0f;

    const int16_t* samples = (const int16_t*)frame;
    left = (float)samples[0] * (1.0f / 32768.0f);
    right = stream->Format.ChannelCount == 2
          ? (float)samples[1] * (1.0f / 32768.0f)
          : left;

    *leftOut = left;
    *rightOut = right;
}

// Applies one final-handle close request while the stream mutex serializes state.
static int KiAudioApplyCloseRequestLocked(KE_AUDIO_STREAM* stream) {
    if (!_InterlockedCompareExchange(&stream->CloseRequested, 0, 0) ||
        stream->State == KeAudioStreamClosed)
        return stream->State == KeAudioStreamClosed;

    uint64_t terminalFrames = stream->FramesPresented + stream->FramesDiscarded;
    if (terminalFrames < stream->FramesSubmitted)
        stream->FramesDiscarded += stream->FramesSubmitted - terminalFrames;
    stream->BufferGeneration++;
    KiAudioSetStreamStateLocked(stream, KeAudioStreamClosed);
    stream->ReadFrame = 0;
    stream->WriteFrame = 0;
    stream->BufferedFrames = 0;
    stream->ResamplePositionQ32 = 0;
    stream->ConsecutiveUnderrunPeriods = 0;
    stream->DiscontinuityGeneration++;
    KiAudioRefreshStreamEventLocked(stream);
    return 1;
}

// Mixes one logical stream into one endpoint period.
static uint32_t KiAudioMixStreamPeriod(KE_AUDIO_STREAM* stream,
                                       float* mix,
                                       uint32_t frames,
                                       uint64_t* streamGenerationOut) {
    KiAudioAcquireMutex(stream->Lock, "KiAudioMixStreamPeriod");
    (void)KiAudioApplyCloseRequestLocked(stream);
    if (!KiAudioStreamStateIsActive(stream->State)) {
        KiAudioReleaseMutex(stream->Lock);
        return 0;
    }

    uint64_t position = stream->ResamplePositionQ32;
    uint32_t silentFrames = 0;
    for (uint32_t outputFrame = 0; outputFrame < frames; outputFrame++) {
        uint32_t sourceOffset = (uint32_t)(position >> 32);
        if (sourceOffset >= stream->BufferedFrames) {
            silentFrames += frames - outputFrame;
            for (; outputFrame < frames; outputFrame++)
                KiAudioAdvanceStreamGainLocked(stream);
            break;
        }

        float left0 = 0.0f;
        float right0 = 0.0f;
        float left1 = 0.0f;
        float right1 = 0.0f;
        KiAudioDecodeSourceFrame(stream, sourceOffset, &left0, &right0);
        if (sourceOffset + 1u < stream->BufferedFrames)
            KiAudioDecodeSourceFrame(stream, sourceOffset + 1u, &left1, &right1);
        else {
            left1 = left0;
            right1 = right0;
        }

        float fraction = (float)(uint32_t)position * (1.0f / 4294967296.0f);
        float left = left0 + (left1 - left0) * fraction;
        float right = right0 + (right1 - right0) * fraction;
        mix[outputFrame * 2u] += left * stream->CurrentLeftGain;
        mix[outputFrame * 2u + 1u] += right * stream->CurrentRightGain;
        KiAudioAdvanceStreamGainLocked(stream);
        position += stream->ResampleStepQ32;
    }

    uint32_t consumed = (uint32_t)(position >> 32);
    if (consumed > stream->BufferedFrames)
        consumed = stream->BufferedFrames;
    stream->ReadFrame = (stream->ReadFrame + consumed) % KE_AUDIO_STREAM_RING_FRAMES;
    stream->BufferedFrames -= consumed;
    stream->FramesConsumed += consumed;
    stream->ResamplePositionQ32 = position - ((uint64_t)consumed << 32);
    stream->OutputFramesMixed += frames - silentFrames;

    if (silentFrames && stream->State == KeAudioStreamRunning) {
        stream->SilenceFramesInserted += silentFrames;
        stream->Underruns++;
        stream->ConsecutiveUnderrunPeriods++;
    } else if (!silentFrames && stream->ConsecutiveUnderrunPeriods) {
        stream->ConsecutiveUnderrunPeriods = 0;
    }

    *streamGenerationOut = stream->BufferGeneration;
    KiAudioRefreshStreamEventLocked(stream);
    KiAudioReleaseMutex(stream->Lock);
    return consumed;
}

// Snapshots referenced streams under the nonblocking membership lock.
static uint32_t KiAudioSnapshotStreams(IO_AUDIO_ENDPOINT* endpoint,
                                       KE_AUDIO_STREAM** streams) {
    uint32_t count = 0;
    uintptr_t flags = KeAcquireSpinlock(&endpoint->StreamListLock);
    for (LIST_ENTRY* link = endpoint->StreamList.Fwd;
         link != &endpoint->StreamList && count < KE_AUDIO_MAX_STREAMS_PER_ENDPOINT;
         link = link->Fwd) {
        KE_AUDIO_STREAM* stream = CONTAINING_RECORD(link, KE_AUDIO_STREAM, EndpointLink);
        if (ObTryReferenceObject(&stream->Header))
            streams[count++] = stream;
    }
    KeReleaseSpinlock(&endpoint->StreamListLock, flags);
    return count;
}

// Applies the endpoint master ramp and writes one interleaved HDA period.
static void KiAudioWriteOutputPeriod(IO_AUDIO_ENDPOINT* endpoint,
                                     uint32_t periodIndex,
                                     float* mix) {
    KiAudioAcquireMutex(endpoint->ControlLock, "KiAudioWriteOutputPeriod");
    float current = 1.0f;
    float target = 1.0f;
    float step = 0.0f;
    uint32_t remaining = 0;
    uint64_t generation = 0;

    uintptr_t flags = KeAcquireSpinlock(&endpoint->NotifyLock);
    current = endpoint->MasterCurrentGain;
    target = endpoint->MasterTargetGain;
    step = endpoint->MasterGainStep;
    remaining = endpoint->MasterRampRemaining;
    generation = endpoint->MasterGainGeneration;
    KeReleaseSpinlock(&endpoint->NotifyLock, flags);

    int16_t* output = (int16_t*)(endpoint->PeriodBuffer +
        (size_t)periodIndex * endpoint->PeriodStrideBytes);
    for (uint32_t frame = 0; frame < endpoint->FramesPerPeriod; frame++) {
        if (remaining) {
            current += step;
            remaining--;
            if (!remaining)
                current = target;
        }
        output[frame * 2u] = KiAudioFloatToOutputSample(mix[frame * 2u] * current);
        output[frame * 2u + 1u] = KiAudioFloatToOutputSample(mix[frame * 2u + 1u] * current);
    }

    flags = KeAcquireSpinlock(&endpoint->NotifyLock);
    if (endpoint->MasterGainGeneration == generation) {
        endpoint->MasterCurrentGain = current;
        endpoint->MasterRampRemaining = remaining;
        if (!remaining)
            endpoint->MasterGainStep = 0.0f;
    }
    KeReleaseSpinlock(&endpoint->NotifyLock, flags);
    KiAudioReleaseMutex(endpoint->ControlLock);
}

// Reserves one free hardware period for passive-level mixing.
static int KiAudioReservePeriod(IO_AUDIO_ENDPOINT* endpoint,
                                uint32_t* periodIndexOut,
                                uint64_t* generationOut) {
    uintptr_t flags = KeAcquireSpinlock(&endpoint->NotifyLock);
    for (uint32_t i = 0; i < endpoint->PeriodCount; i++) {
        if (endpoint->Periods[i].State != KE_AUDIO_PERIOD_STATE_FREE)
            continue;
        if (endpoint->Periods[i].ContributionCount)
            KiAudioBug("KiAudioReservePeriod", "free period retains contributions", i);
        endpoint->Periods[i].State = KE_AUDIO_PERIOD_STATE_FILLING;
        *periodIndexOut = i;
        *generationOut = endpoint->Periods[i].Generation;
        KeReleaseSpinlock(&endpoint->NotifyLock, flags);
        return 1;
    }
    KeReleaseSpinlock(&endpoint->NotifyLock, flags);
    return 0;
}

// Discards one contribution array after its mixed source frames cannot be presented.
static void KiAudioDiscardContributions(KE_AUDIO_PERIOD_CONTRIBUTION* contributions,
                                        uint32_t contributionCount) {
    for (uint32_t i = 0; i < contributionCount; i++) {
        KE_AUDIO_PERIOD_CONTRIBUTION* contribution = &contributions[i];
        KE_AUDIO_STREAM* stream = contribution->Stream;
        KiAudioAcquireMutex(stream->Lock, "KiAudioDiscardContributions");
        if (stream->BufferGeneration == contribution->StreamGeneration) {
            stream->FramesDiscarded += contribution->SourceFrames;
            if (stream->State == KeAudioStreamDraining &&
                KiAudioDrainIsCompleteLocked(stream))
                KiAudioCompleteDrainLocked(stream);
            KiAudioRefreshStreamEventLocked(stream);
        }
        KiAudioReleaseMutex(stream->Lock);
        ObDereferenceObject(&stream->Header);
    }
}

// Commits one mixed period only if no missed deadline invalidated the reservation.
static int KiAudioCommitPeriod(IO_AUDIO_ENDPOINT* endpoint,
                               uint32_t periodIndex,
                               uint64_t generation,
                               KE_AUDIO_PERIOD_CONTRIBUTION* contributions,
                               uint32_t contributionCount) {
    uintptr_t flags = KeAcquireSpinlock(&endpoint->NotifyLock);
    KE_AUDIO_PERIOD_STATE* period = &endpoint->Periods[periodIndex];
    int committed = period->State == KE_AUDIO_PERIOD_STATE_FILLING &&
                    period->Generation == generation;
    if (committed) {
        if (period->ContributionCount)
            KiAudioBug("KiAudioCommitPeriod", "stale period contributions", periodIndex);
        for (uint32_t i = 0; i < contributionCount; i++)
            period->Contributions[i] = contributions[i];
        period->ContributionCount = contributionCount;
        period->State = KE_AUDIO_PERIOD_STATE_READY;
        endpoint->PeriodsMixed++;
    }
    KeReleaseSpinlock(&endpoint->NotifyLock, flags);
    if (!committed) {
        memset(endpoint->PeriodBuffer + (size_t)periodIndex * endpoint->PeriodStrideBytes,
               0,
               endpoint->PeriodStrideBytes);
        KiAudioDiscardContributions(contributions, contributionCount);
        flags = KeAcquireSpinlock(&endpoint->NotifyLock);
        if (period->State == KE_AUDIO_PERIOD_STATE_FILLING ||
            period->State == KE_AUDIO_PERIOD_STATE_COMPLETED)
            period->State = KE_AUDIO_PERIOD_STATE_FREE;
        KeReleaseSpinlock(&endpoint->NotifyLock, flags);
    }
    return committed;
}

// Mixes one free endpoint period from all currently referenced streams.
static int KiAudioMixOnePeriod(IO_AUDIO_ENDPOINT* endpoint) {
    uint32_t periodIndex = 0;
    uint64_t generation = 0;
    if (!KiAudioReservePeriod(endpoint, &periodIndex, &generation))
        return 0;

    float mix[KE_AUDIO_OUTPUT_FRAMES_PER_PERIOD * KE_AUDIO_OUTPUT_CHANNELS];
    memset(mix, 0, sizeof(mix));

    KE_AUDIO_PERIOD_CONTRIBUTION contributions[KE_AUDIO_MAX_STREAMS_PER_ENDPOINT];
    uint32_t contributionCount = 0;
    KE_AUDIO_STREAM* streams[KE_AUDIO_MAX_STREAMS_PER_ENDPOINT];
    uint32_t streamCount = KiAudioSnapshotStreams(endpoint, streams);
    for (uint32_t i = 0; i < streamCount; i++) {
        uint64_t streamGeneration = 0;
        uint32_t consumed = KiAudioMixStreamPeriod(streams[i],
                                                   mix,
                                                   endpoint->FramesPerPeriod,
                                                   &streamGeneration);
        if (consumed) {
            contributions[contributionCount].Stream = streams[i];
            contributions[contributionCount].StreamGeneration = streamGeneration;
            contributions[contributionCount].SourceFrames = consumed;
            contributionCount++;
        } else {
            ObDereferenceObject(&streams[i]->Header);
        }
    }

    KiAudioWriteOutputPeriod(endpoint, periodIndex, mix);
    return KiAudioCommitPeriod(endpoint,
                               periodIndex,
                               generation,
                               contributions,
                               contributionCount);
}

// Applies one hardware-completed period to per-stream presentation counters.
static int KiAudioReapOneCompletedPeriod(IO_AUDIO_ENDPOINT* endpoint) {
    uint32_t periodIndex = 0;
    KE_AUDIO_PERIOD_STATE* period = (KE_AUDIO_PERIOD_STATE*)0;
    uintptr_t flags = KeAcquireSpinlock(&endpoint->NotifyLock);
    for (uint32_t i = 0; i < endpoint->PeriodCount; i++) {
        if (endpoint->Periods[i].State == KE_AUDIO_PERIOD_STATE_COMPLETED) {
            periodIndex = i;
            period = &endpoint->Periods[i];
            period->State = KE_AUDIO_PERIOD_STATE_REAPING;
            break;
        }
    }
    KeReleaseSpinlock(&endpoint->NotifyLock, flags);
    if (!period)
        return 0;

    for (uint32_t i = 0; i < period->ContributionCount; i++) {
        KE_AUDIO_PERIOD_CONTRIBUTION* contribution = &period->Contributions[i];
        KE_AUDIO_STREAM* stream = contribution->Stream;
        KiAudioAcquireMutex(stream->Lock, "KiAudioReapOneCompletedPeriod");
        if (stream->BufferGeneration == contribution->StreamGeneration) {
            stream->FramesPresented += contribution->SourceFrames;
            if (stream->State == KeAudioStreamDraining &&
                KiAudioDrainIsCompleteLocked(stream))
                KiAudioCompleteDrainLocked(stream);
            KiAudioRefreshStreamEventLocked(stream);
        }
        KiAudioReleaseMutex(stream->Lock);
        ObDereferenceObject(&stream->Header);
    }

    memset(endpoint->PeriodBuffer + (size_t)periodIndex * endpoint->PeriodStrideBytes,
           0,
           endpoint->PeriodStrideBytes);
    flags = KeAcquireSpinlock(&endpoint->NotifyLock);
    period->ContributionCount = 0;
    period->State = KE_AUDIO_PERIOD_STATE_FREE;
    KeReleaseSpinlock(&endpoint->NotifyLock, flags);
    return 1;
}

// Counts periods ready for hardware consumption.
static uint32_t KiAudioReadyPeriodCount(IO_AUDIO_ENDPOINT* endpoint) {
    uint32_t ready = 0;
    uintptr_t flags = KeAcquireSpinlock(&endpoint->NotifyLock);
    for (uint32_t i = 0; i < endpoint->PeriodCount; i++) {
        if (endpoint->Periods[i].State == KE_AUDIO_PERIOD_STATE_READY)
            ready++;
    }
    KeReleaseSpinlock(&endpoint->NotifyLock, flags);
    return ready;
}

// Starts provider DMA after at least two periods are prepared.
static KSTATUS KiAudioStartHardware(IO_AUDIO_ENDPOINT* endpoint) {
    KiAudioAcquireMutex(endpoint->ControlLock, "KiAudioStartHardware");
    uintptr_t registryFlags = KeAcquireSpinlock(&gAudioRegistryLock);
    if (endpoint->State != KeAudioEndpointReady) {
        KSTATUS status = KFAILED(endpoint->FailureStatus)
                       ? endpoint->FailureStatus
                       : NTLSTATUS_DEVICE_REMOVED;
        KeReleaseSpinlock(&gAudioRegistryLock, registryFlags);
        KiAudioReleaseMutex(endpoint->ControlLock);
        return status;
    }
    KeReleaseSpinlock(&gAudioRegistryLock, registryFlags);

    uintptr_t flags = KeAcquireSpinlock(&endpoint->NotifyLock);
    if (endpoint->HardwareRunning || endpoint->ActiveStreamCount == 0) {
        KeReleaseSpinlock(&endpoint->NotifyLock, flags);
        KiAudioReleaseMutex(endpoint->ControlLock);
        return NTLSTATUS_SUCCESS;
    }
    endpoint->HardwareRunning = 1;
    endpoint->IdleDeadlineTicks = 0;
    KeReleaseSpinlock(&endpoint->NotifyLock, flags);

    KSTATUS status = NTLSTATUS_SUCCESS;
    int startAttempted = 0;
    if (endpoint->Capabilities & IO_AUDIO_ENDPOINT_CAP_HARDWARE_GAIN) {
        status = endpoint->Operations.SetGain(endpoint->ProviderContext,
                                              endpoint->MasterHardwareGainMilliDb,
                                              0);
    }
    if (KSUCCESS(status)) {
        startAttempted = 1;
        status = endpoint->Operations.Start(endpoint->ProviderContext);
    }
    if (!KSUCCESS(status) && startAttempted)
        endpoint->Operations.Stop(endpoint->ProviderContext);
    if (!KSUCCESS(status)) {
        flags = KeAcquireSpinlock(&endpoint->NotifyLock);
        endpoint->HardwareRunning = 0;
        KeReleaseSpinlock(&endpoint->NotifyLock, flags);
        KiAudioReleaseMutex(endpoint->ControlLock);
        return status;
    }

    flags = KeAcquireSpinlock(&endpoint->NotifyLock);
    endpoint->HardwareStarts++;
    KeReleaseSpinlock(&endpoint->NotifyLock, flags);
    KiAudioReleaseMutex(endpoint->ControlLock);
    return NTLSTATUS_SUCCESS;
}

// Discards one period's unpresented stream contributions during hardware teardown.
static void KiAudioDiscardPeriodContributions(KE_AUDIO_PERIOD_STATE* period) {
    KiAudioDiscardContributions(period->Contributions, period->ContributionCount);
    period->ContributionCount = 0;
}

// Stops provider DMA and returns every period to a zeroed free state.
static void KiAudioStopHardware(IO_AUDIO_ENDPOINT* endpoint, int hardwareAccessible) {
    KiAudioAcquireMutex(endpoint->ControlLock, "KiAudioStopHardware");
    uintptr_t flags = KeAcquireSpinlock(&endpoint->NotifyLock);
    int wasRunning = endpoint->HardwareRunning;
    endpoint->HardwareRunning = 0;
    endpoint->IdleDeadlineTicks = 0;
    KeReleaseSpinlock(&endpoint->NotifyLock, flags);

    if (wasRunning && hardwareAccessible) {
        if (endpoint->Capabilities & IO_AUDIO_ENDPOINT_CAP_HARDWARE_GAIN) {
            KSTATUS muteStatus = endpoint->Operations.SetGain(
                endpoint->ProviderContext,
                endpoint->MasterHardwareGainMilliDb,
                1);
            if (!KSUCCESS(muteStatus)) {
                DbgPrint("audio: endpoint %llu hardware mute failed status=0x%x\n",
                         (unsigned long long)endpoint->EndpointId,
                         muteStatus);
            }
        }
        endpoint->Operations.Stop(endpoint->ProviderContext);
    }

    while (KiAudioReapOneCompletedPeriod(endpoint)) {
    }
    for (uint32_t i = 0; i < endpoint->PeriodCount; i++)
        KiAudioDiscardPeriodContributions(&endpoint->Periods[i]);
    memset(endpoint->PeriodBuffer, 0, endpoint->PeriodBufferBytes);

    flags = KeAcquireSpinlock(&endpoint->NotifyLock);
    for (uint32_t i = 0; i < endpoint->PeriodCount; i++) {
        endpoint->Periods[i].State = KE_AUDIO_PERIOD_STATE_FREE;
        endpoint->Periods[i].Generation++;
    }
    endpoint->MasterCurrentGain = endpoint->MasterTargetGain;
    endpoint->MasterGainStep = 0.0f;
    endpoint->MasterRampRemaining = 0;
    endpoint->MasterGainGeneration++;
    if (wasRunning)
        endpoint->HardwareStops++;
    KeReleaseSpinlock(&endpoint->NotifyLock, flags);
    KiAudioReleaseMutex(endpoint->ControlLock);
}

// Fails every logical stream while preserving final counters for later queries.
static void KiAudioFailAllStreams(IO_AUDIO_ENDPOINT* endpoint, KSTATUS status) {
    KE_AUDIO_STREAM* streams[KE_AUDIO_MAX_STREAMS_PER_ENDPOINT];
    uint32_t streamCount = KiAudioSnapshotStreams(endpoint, streams);
    for (uint32_t i = 0; i < streamCount; i++) {
        KE_AUDIO_STREAM* stream = streams[i];
        KiAudioAcquireMutex(stream->Lock, "KiAudioFailAllStreams");
        if (stream->State != KeAudioStreamClosed) {
            stream->FramesDiscarded += stream->BufferedFrames;
            stream->BufferedFrames = 0;
            stream->ReadFrame = 0;
            stream->WriteFrame = 0;
            stream->ResamplePositionQ32 = 0;
            KiAudioSetStreamStateLocked(stream, KeAudioStreamFailed);
            stream->FailureStatus = status;
            stream->BufferGeneration++;
            stream->DiscontinuityGeneration++;
            KiAudioRefreshStreamEventLocked(stream);
        }
        KiAudioReleaseMutex(stream->Lock);
        ObDereferenceObject(&stream->Header);
    }

    uintptr_t flags = KeAcquireSpinlock(&endpoint->NotifyLock);
    if (endpoint->ActiveStreamCount != 0) {
        uint32_t active = endpoint->ActiveStreamCount;
        KeReleaseSpinlock(&endpoint->NotifyLock, flags);
        KiAudioBug("KiAudioFailAllStreams", "active streams remained after failure", active);
    }
    endpoint->IdleDeadlineTicks = 0;
    KeReleaseSpinlock(&endpoint->NotifyLock, flags);
}

// Applies hardware deadline discontinuities to every live logical stream at passive level.
static void KiAudioApplyPendingDiscontinuities(IO_AUDIO_ENDPOINT* endpoint) {
    uintptr_t flags = KeAcquireSpinlock(&endpoint->NotifyLock);
    uint64_t pending = endpoint->PendingDiscontinuities;
    endpoint->PendingDiscontinuities = 0;
    KeReleaseSpinlock(&endpoint->NotifyLock, flags);
    if (!pending)
        return;

    KE_AUDIO_STREAM* streams[KE_AUDIO_MAX_STREAMS_PER_ENDPOINT];
    uint32_t streamCount = KiAudioSnapshotStreams(endpoint, streams);
    for (uint32_t i = 0; i < streamCount; i++) {
        KE_AUDIO_STREAM* stream = streams[i];
        KiAudioAcquireMutex(stream->Lock, "KiAudioApplyPendingDiscontinuities");
        if (KiAudioStreamStateIsActive(stream->State)) {
            stream->Underruns += pending;
            stream->SilenceFramesInserted += pending * endpoint->FramesPerPeriod;
            stream->DiscontinuityGeneration += pending;
            KiAudioRefreshStreamEventLocked(stream);
        }
        KiAudioReleaseMutex(stream->Lock);
        ObDereferenceObject(&stream->Header);
    }
}

// Returns one coherent endpoint lifecycle snapshot.
static void KiAudioSnapshotLifecycle(IO_AUDIO_ENDPOINT* endpoint,
                                     KE_AUDIO_LIFECYCLE_SNAPSHOT* snapshot) {
    uintptr_t flags = KeAcquireSpinlock(&gAudioRegistryLock);
    snapshot->State = endpoint->State;
    snapshot->FailureStatus = endpoint->FailureStatus;
    snapshot->RemovalMode = endpoint->RemovalMode;
    snapshot->SkipProviderStop = endpoint->SkipProviderStop;
    KeReleaseSpinlock(&gAudioRegistryLock, flags);
}

// Processes all currently available period and lifecycle work.
static int KiAudioProcessEndpoint(IO_AUDIO_ENDPOINT* endpoint,
                                  uint64_t* waitMillisecondsOut) {
    *waitMillisecondsOut = (uint64_t)-1;
    while (KiAudioReapOneCompletedPeriod(endpoint)) {
    }
    KiAudioApplyPendingDiscontinuities(endpoint);
    KE_AUDIO_LIFECYCLE_SNAPSHOT lifecycle;
    KiAudioSnapshotLifecycle(endpoint, &lifecycle);
    KSTATUS failure = lifecycle.FailureStatus;
    if (lifecycle.State == KeAudioEndpointStopping ||
        lifecycle.State == KeAudioEndpointFailed ||
        lifecycle.State == KeAudioEndpointRemoved) {
        int accessible = !lifecycle.SkipProviderStop &&
                         lifecycle.RemovalMode != IoAudioSurpriseRemoval;
        KiAudioStopHardware(endpoint, accessible);
        if (lifecycle.State == KeAudioEndpointRemoved && KSUCCESS(failure))
            failure = NTLSTATUS_DEVICE_REMOVED;
        if (KSUCCESS(failure))
            failure = NTLSTATUS_DEVICE_ERROR;
        KiAudioFailAllStreams(endpoint, failure);
        return 0;
    }

    uintptr_t flags = KeAcquireSpinlock(&endpoint->NotifyLock);
    uint32_t active = endpoint->ActiveStreamCount;
    int running = endpoint->HardwareRunning;
    uint64_t idleDeadline = endpoint->IdleDeadlineTicks;
    KeReleaseSpinlock(&endpoint->NotifyLock, flags);

    if (active && !running) {
        while (KiAudioReadyPeriodCount(endpoint) < 2u &&
               KiAudioMixOnePeriod(endpoint)) {
        }
        if (KiAudioReadyPeriodCount(endpoint) >= 2u) {
            KSTATUS start = KiAudioStartHardware(endpoint);
            if (!KSUCCESS(start)) {
                uintptr_t registryFlags = KeAcquireSpinlock(&gAudioRegistryLock);
                KiAudioSetEndpointStateLocked(endpoint, KeAudioEndpointFailed);
                endpoint->FailureStatus = start;
                KiAudioSelectDefaultEndpointLocked();
                KeReleaseSpinlock(&gAudioRegistryLock, registryFlags);
                KeSignalEvent(endpoint->WorkEvent);
                return 1;
            }
        }
    }

    flags = KeAcquireSpinlock(&endpoint->NotifyLock);
    active = endpoint->ActiveStreamCount;
    running = endpoint->HardwareRunning;
    KeReleaseSpinlock(&endpoint->NotifyLock, flags);
    if (active || running) {
        while (KiAudioMixOnePeriod(endpoint)) {
        }
    }

    flags = KeAcquireSpinlock(&endpoint->NotifyLock);
    active = endpoint->ActiveStreamCount;
    running = endpoint->HardwareRunning;
    idleDeadline = endpoint->IdleDeadlineTicks;
    KeReleaseSpinlock(&endpoint->NotifyLock, flags);

    if (!active && running) {
        uint64_t now = KiAudioQueryTicks();
        if (!idleDeadline) {
            flags = KeAcquireSpinlock(&endpoint->NotifyLock);
            endpoint->IdleDeadlineTicks = now +
                (uint64_t)KE_AUDIO_IDLE_STOP_MILLISECONDS * KE_AUDIO_TICKS_PER_MILLISECOND;
            idleDeadline = endpoint->IdleDeadlineTicks;
            KeReleaseSpinlock(&endpoint->NotifyLock, flags);
        }
        if (now >= idleDeadline) {
            KiAudioStopHardware(endpoint, 1);
        } else {
            uint64_t remainingTicks = idleDeadline - now;
            *waitMillisecondsOut = (remainingTicks + KE_AUDIO_TICKS_PER_MILLISECOND - 1u) /
                                   KE_AUDIO_TICKS_PER_MILLISECOND;
            if (!*waitMillisecondsOut)
                *waitMillisecondsOut = 1;
        }
    }
    return 1;
}

// Runs one endpoint's real-time mixer and provider lifecycle loop.
static void KiAudioMixerThread(void* argument) {
    IO_AUDIO_ENDPOINT* endpoint = (IO_AUDIO_ENDPOINT*)argument;
    while (true) {
        KeClearEvent(endpoint->WorkEvent);
        uint64_t waitMilliseconds = (uint64_t)-1;
        if (!KiAudioProcessEndpoint(endpoint, &waitMilliseconds))
            break;

        KSTATUS waitStatus = NTLSTATUS_SUCCESS;
        if (waitMilliseconds == (uint64_t)-1) {
            waitStatus = KeWaitForEvent(endpoint->WorkEvent, 0);
        } else {
            EVENT* events[1] = { endpoint->WorkEvent };
            uint32_t selected = 0;
            waitStatus = KeWaitForMultipleEvents(events,
                                                 1,
                                                 0,
                                                 waitMilliseconds,
                                                 &selected);
        }
        if (waitStatus != NTLSTATUS_SUCCESS && waitStatus != NTLSTATUS_TIMEOUT)
            KiAudioBug("KiAudioMixerThread", "work wait failed", waitStatus);
    }

    KeSignalEvent(endpoint->MixerExitEvent);
    ObDereferenceObject(&endpoint->Header);
}

// Destroys one fully unregistered endpoint after its mixer and streams leave.
static void KiAudioEndpointDestroy(OBJECT* object) {
    IO_AUDIO_ENDPOINT* endpoint = CONTAINING_RECORD(object, IO_AUDIO_ENDPOINT, Header);
    if (endpoint->Registered || endpoint->MixerThread ||
        !LIST_IS_EMPTY(&endpoint->StreamList) || endpoint->HardwareRunning ||
        endpoint->ActiveStreamCount)
        KiAudioBug("KiAudioEndpointDestroy", "live endpoint reached destruction", endpoint->EndpointId);
    if (endpoint->Device)
        IoDereferenceDeviceObject(endpoint->Device);
    if (endpoint->ControlLock)
        ObDereferenceObject(&endpoint->ControlLock->Header);
    if (endpoint->WorkEvent)
        ObDereferenceObject(&endpoint->WorkEvent->Header);
    if (endpoint->MixerExitEvent)
        ObDereferenceObject(&endpoint->MixerExitEvent->Header);
}

// Records one process handle that owns the stream.
void KeAudioStreamHandleOpened(KE_AUDIO_STREAM* stream) {
    if (!stream)
        return;

    long handleCount = _InterlockedIncrement(&stream->ProcessHandleCount);
    if (handleCount <= 0)
        KiAudioBug("KeAudioStreamHandleOpened", "invalid process handle count", handleCount);
}

// Requests passive stream closure when the final process handle disappears.
void KeAudioStreamHandleClosed(KE_AUDIO_STREAM* stream) {
    if (!stream)
        return;

    long handleCount = _InterlockedDecrement(&stream->ProcessHandleCount);
    if (handleCount < 0)
        KiAudioBug("KeAudioStreamHandleClosed", "process handle underflow", handleCount);
    if (handleCount != 0)
        return;

    _InterlockedExchange(&stream->CloseRequested, 1);
    KeSignalEvent(stream->WaitEvent);
    if (stream->Endpoint)
        KeSignalEvent(stream->Endpoint->WorkEvent);
}

// Destroys one exclusively owned stream without entering blocking primitives.
static void KiAudioStreamDestroy(OBJECT* object) {
    KE_AUDIO_STREAM* stream = CONTAINING_RECORD(object, KE_AUDIO_STREAM, Header);
    IO_AUDIO_ENDPOINT* endpoint = stream->Endpoint;
    if (endpoint) {
        uintptr_t flags = KeAcquireSpinlock(&endpoint->StreamListLock);
        if (stream->EndpointLink.Fwd != &stream->EndpointLink ||
            stream->EndpointLink.Bwd != &stream->EndpointLink)
            KeListRemoveChecked(&stream->EndpointLink);
        KeReleaseSpinlock(&endpoint->StreamListLock, flags);
    }

    if (stream->Lock &&
        (stream->Lock->Owner || !LIST_IS_EMPTY(&stream->Lock->WaitList)))
        KiAudioBug("KiAudioStreamDestroy", "live stream mutex reached destruction",
                   (uint64_t)(uintptr_t)stream->Lock->Owner);
    if (!KiAudioStreamTransitionAllowed(stream->State, KeAudioStreamClosed))
        KiAudioBug("KiAudioStreamDestroy", "invalid terminal stream state", stream->State);
    int wasActive = KiAudioStreamStateIsActive(stream->State);
    stream->State = KeAudioStreamClosed;
    if (wasActive)
        KiAudioAdjustActiveStreams(endpoint, -1);

    if (stream->Ring)
        MmFreePool(stream->Ring);
    if (stream->WaitEvent)
        ObDereferenceObject(&stream->WaitEvent->Header);
    if (stream->Lock)
        ObDereferenceObject(&stream->Lock->Header);
    if (endpoint)
        ObDereferenceObject(&endpoint->Header);
    _InterlockedIncrement64(&gAudioCoreStats.StreamsDestroyed);
}

// Registers one hardware-provider endpoint.
static KSTATUS KiAudioRegisterEndpoint(const IO_AUDIO_ENDPOINT_REGISTRATION* registration,
                                       IO_AUDIO_ENDPOINT** outEndpoint) {
    if (!outEndpoint)
        return NTLSTATUS_INVALID_PARAMETER;
    *outEndpoint = (IO_AUDIO_ENDPOINT*)0;
    KSTATUS status = KiAudioValidateRegistration(registration);
    if (!KSUCCESS(status))
        return status;

    IO_AUDIO_ENDPOINT* endpoint = (IO_AUDIO_ENDPOINT*)ObAllocateObject(
        ObjectTypeAudioEndpoint,
        sizeof(IO_AUDIO_ENDPOINT));
    if (!endpoint)
        return NTLSTATUS_NO_MEMORY;
    endpoint->Header.Destroy = KiAudioEndpointDestroy;
    LIST_INIT(&endpoint->RegistryLink);
    LIST_INIT(&endpoint->StreamList);
    endpoint->StreamListLock = (SPINLOCK)SPINLOCK_INIT;
    endpoint->NotifyLock = (SPINLOCK)SPINLOCK_INIT;
    endpoint->Kind = registration->Kind;
    endpoint->State = KeAudioEndpointStarting;
    endpoint->Capabilities = registration->Capabilities;
    endpoint->Available = registration->InitiallyAvailable ? 1u : 0u;
    endpoint->Device = registration->Device;
    endpoint->ProviderContext = registration->ProviderContext;
    endpoint->Operations = registration->Operations;
    endpoint->PeriodBuffer = (uint8_t*)registration->PeriodBuffer;
    endpoint->PeriodBufferBytes = registration->PeriodBufferBytes;
    endpoint->PeriodCount = registration->PeriodCount;
    endpoint->FramesPerPeriod = registration->FramesPerPeriod;
    endpoint->PeriodStrideBytes = registration->PeriodStrideBytes;
    endpoint->HardwareFormat = registration->HardwareFormat;
    endpoint->HardwareGainMinimumMilliDb = registration->HardwareGainMinimumMilliDb;
    endpoint->HardwareGainMaximumMilliDb = registration->HardwareGainMaximumMilliDb;
    endpoint->HardwareGainStepMilliDb = registration->HardwareGainStepMilliDb;
    endpoint->MasterRequestedVolume = 1.0f;
    endpoint->MasterHardwareGainMilliDb = KiAudioHighestSafeHardwareGain(endpoint);
    endpoint->MasterCurrentGain = KiAudioSoftwareGainForVolume(endpoint, 1.0f);
    endpoint->MasterTargetGain = endpoint->MasterCurrentGain;
    endpoint->RemovalMode = IoAudioOrderlyRemoval;
    memset(endpoint->PeriodBuffer, 0, endpoint->PeriodBufferBytes);
    for (uint32_t i = 0; i < endpoint->PeriodCount; i++)
        endpoint->Periods[i].State = KE_AUDIO_PERIOD_STATE_FREE;

    if (endpoint->Device)
        IoReferenceDeviceObject(endpoint->Device);

    status = KeMutexCreate(&endpoint->ControlLock);
    if (!KSUCCESS(status)) {
        ObDereferenceObject(&endpoint->Header);
        return status;
    }
    status = KeEventCreate(EventManualReset, 0, &endpoint->WorkEvent);
    if (!KSUCCESS(status)) {
        ObDereferenceObject(&endpoint->Header);
        return status;
    }
    status = KeEventCreate(EventManualReset, 0, &endpoint->MixerExitEvent);
    if (!KSUCCESS(status)) {
        ObDereferenceObject(&endpoint->Header);
        return status;
    }

    ObReferenceObject(&endpoint->Header);
    const KE_THREAD_CREATE_PARAMETERS mixerParameters =
        KE_THREAD_CREATE_NAMED_REALTIME(KE_AUDIO_MIXER_REALTIME_PRIORITY, "audio.mixer");
    status = KeCreateKernelThread((uintptr_t)KiAudioMixerThread,
                                  (uintptr_t)endpoint,
                                  &mixerParameters,
                                  &endpoint->MixerThread);
    if (!KSUCCESS(status)) {
        ObDereferenceObject(&endpoint->Header);
        ObDereferenceObject(&endpoint->Header);
        return status;
    }

    uintptr_t flags = KeAcquireSpinlock(&gAudioRegistryLock);
    if (gAudioEndpointCount >= KE_AUDIO_MAX_ENDPOINTS) {
        KiAudioSetEndpointStateLocked(endpoint, KeAudioEndpointStopping);
        endpoint->FailureStatus = NTLSTATUS_NO_MEMORY;
        KeReleaseSpinlock(&gAudioRegistryLock, flags);
        KeSignalEvent(endpoint->WorkEvent);
        (void)KeWaitForEvent(endpoint->MixerExitEvent, 0);
        ObDereferenceObject(&endpoint->MixerThread->Header);
        endpoint->MixerThread = (THREAD*)0;
        ObDereferenceObject(&endpoint->Header);
        return NTLSTATUS_NO_MEMORY;
    }
    KSTATUS idStatus = KeAllocateId32(&gAudioEndpointIds, &endpoint->EndpointId);
    if (!KSUCCESS(idStatus)) {
        KiAudioSetEndpointStateLocked(endpoint, KeAudioEndpointStopping);
        endpoint->FailureStatus = idStatus;
        KeReleaseSpinlock(&gAudioRegistryLock, flags);
        KeSignalEvent(endpoint->WorkEvent);
        (void)KeWaitForEvent(endpoint->MixerExitEvent, 0);
        ObDereferenceObject(&endpoint->MixerThread->Header);
        endpoint->MixerThread = (THREAD*)0;
        ObDereferenceObject(&endpoint->Header);
        return idStatus;
    }
    KiAudioSetEndpointStateLocked(endpoint, KeAudioEndpointReady);
    endpoint->Registered = 1;
    ObReferenceObject(&endpoint->Header);
    KeListInsertTailChecked(&gAudioEndpointList, &endpoint->RegistryLink);
    gAudioEndpointCount++;
    KiAudioSelectDefaultEndpointLocked();
    KeReleaseSpinlock(&gAudioRegistryLock, flags);

    _InterlockedIncrement64(&gAudioCoreStats.EndpointsRegistered);
    *outEndpoint = endpoint;
    return NTLSTATUS_SUCCESS;
}

// Implements the provider-facing endpoint registration operation.
static KSTATUS KiAudioDdkRegisterEndpoint(const IO_AUDIO_ENDPOINT_REGISTRATION* registration,
                                          IO_AUDIO_ENDPOINT** outEndpoint) {
    return KiAudioRegisterEndpoint(registration, outEndpoint);
}

// Removes one endpoint and waits until no provider operation can run again.
static void KiAudioDdkUnregisterEndpoint(IO_AUDIO_ENDPOINT* endpoint,
                                         IO_AUDIO_REMOVAL_MODE mode) {
    if (!endpoint || (mode != IoAudioOrderlyRemoval && mode != IoAudioSurpriseRemoval))
        KiAudioBug("KiAudioDdkUnregisterEndpoint", "invalid unregister request", mode);

    uintptr_t flags = KeAcquireSpinlock(&gAudioRegistryLock);
    if (!endpoint->Registered) {
        KeReleaseSpinlock(&gAudioRegistryLock, flags);
        KiAudioBug("KiAudioDdkUnregisterEndpoint", "duplicate unregister", endpoint->EndpointId);
    }
    KeListRemoveChecked(&endpoint->RegistryLink);
    endpoint->Registered = 0;
    KiAudioSetEndpointStateLocked(endpoint, KeAudioEndpointStopping);
    if (KSUCCESS(endpoint->FailureStatus))
        endpoint->FailureStatus = NTLSTATUS_DEVICE_REMOVED;
    endpoint->RemovalMode = mode;
    endpoint->SkipProviderStop = mode == IoAudioSurpriseRemoval ? 1u : 0u;
    gAudioEndpointCount--;
    KiAudioSelectDefaultEndpointLocked();
    KeReleaseSpinlock(&gAudioRegistryLock, flags);

    KeSignalEvent(endpoint->WorkEvent);
    (void)KeWaitForEvent(endpoint->MixerExitEvent, 0);

    flags = KeAcquireSpinlock(&gAudioRegistryLock);
    KiAudioSetEndpointStateLocked(endpoint, KeAudioEndpointRemoved);
    KeReleaseSpinlock(&gAudioRegistryLock, flags);

    if (!endpoint->MixerThread)
        KiAudioBug("KiAudioDdkUnregisterEndpoint", "missing mixer thread", endpoint->EndpointId);
    ObDereferenceObject(&endpoint->MixerThread->Header);
    endpoint->MixerThread = (THREAD*)0;

    _InterlockedIncrement64(&gAudioCoreStats.EndpointsUnregistered);
    ObDereferenceObject(&endpoint->Header);
    ObDereferenceObject(&endpoint->Header);
}

// Advances one provider ring period and wakes the real-time mixer.
static void KiAudioDdkNotifyPeriod(IO_AUDIO_ENDPOINT* endpoint,
                                   uint32_t completedPeriodIndex,
                                   uint64_t presentedFrames,
                                   uint64_t hardwarePositionFrames,
                                   uint64_t interruptCount,
                                   uint64_t timestampTicks) {
    if (!endpoint || completedPeriodIndex >= endpoint->PeriodCount)
        KiAudioBug("KiAudioDdkNotifyPeriod", "invalid period notification", completedPeriodIndex);

    uintptr_t flags = KeAcquireSpinlock(&endpoint->NotifyLock);
    KE_AUDIO_PERIOD_STATE* period = &endpoint->Periods[completedPeriodIndex];
    if (!endpoint->HardwareRunning) {
        endpoint->SpuriousNotifications++;
        KeReleaseSpinlock(&endpoint->NotifyLock, flags);
        return;
    }

    int missedDeadline = period->State != KE_AUDIO_PERIOD_STATE_READY;
    if (missedDeadline) {
        endpoint->Underruns++;
        endpoint->DiscontinuityGeneration++;
        endpoint->SilenceFramesInserted += endpoint->FramesPerPeriod;
        endpoint->PendingDiscontinuities++;
    }
    if (period->State == KE_AUDIO_PERIOD_STATE_COMPLETED ||
        period->State == KE_AUDIO_PERIOD_STATE_REAPING) {
        endpoint->SpuriousNotifications++;
    } else {
        period->Generation++;
        period->State = KE_AUDIO_PERIOD_STATE_COMPLETED;
    }
    endpoint->PeriodsCompleted++;
    if (presentedFrames < endpoint->FramesPresented) {
        endpoint->DiscontinuityGeneration++;
        endpoint->PendingDiscontinuities++;
    } else {
        endpoint->FramesPresented = presentedFrames;
    }
    if (hardwarePositionFrames < endpoint->HardwarePositionFrames ||
        interruptCount < endpoint->InterruptCount) {
        endpoint->DiscontinuityGeneration++;
        endpoint->PendingDiscontinuities++;
    } else {
        endpoint->HardwarePositionFrames = hardwarePositionFrames;
        endpoint->InterruptCount = interruptCount;
    }
    endpoint->LastPresentationTimestampTicks = timestampTicks;
    KeReleaseSpinlock(&endpoint->NotifyLock, flags);

    KeSignalEvent(endpoint->WorkEvent);
}

// Updates one endpoint's jack-derived availability and default selection.
static void KiAudioDdkSetEndpointAvailable(IO_AUDIO_ENDPOINT* endpoint, uint8_t available) {
    if (!endpoint || !(endpoint->Capabilities & IO_AUDIO_ENDPOINT_CAP_JACK_SENSE))
        KiAudioBug("KiAudioDdkSetEndpointAvailable", "invalid availability update", 0);
    uintptr_t flags = KeAcquireSpinlock(&gAudioRegistryLock);
    if (endpoint->State == KeAudioEndpointReady) {
        endpoint->Available = available ? 1u : 0u;
        KiAudioSelectDefaultEndpointLocked();
    }
    KeReleaseSpinlock(&gAudioRegistryLock, flags);
}

// Fails one endpoint from provider completion or recovery code.
static void KiAudioDdkReportEndpointFailure(IO_AUDIO_ENDPOINT* endpoint,
                                            KSTATUS status,
                                            uint32_t flags) {
    if (!endpoint || !KFAILED(status) || (flags & ~IO_AUDIO_FAILURE_VALID_MASK) != 0)
        KiAudioBug("KiAudioDdkReportEndpointFailure", "invalid failure report", status);
    uintptr_t registryFlags = KeAcquireSpinlock(&gAudioRegistryLock);
    if (flags & IO_AUDIO_FAILURE_HARDWARE_INACCESSIBLE)
        endpoint->SkipProviderStop = 1;
    if (endpoint->State == KeAudioEndpointReady) {
        KiAudioSetEndpointStateLocked(endpoint, KeAudioEndpointFailed);
        endpoint->FailureStatus = status;
        endpoint->Available = 0;
        KiAudioSelectDefaultEndpointLocked();
    }
    KeReleaseSpinlock(&gAudioRegistryLock, registryFlags);
    DbgPrint("audio: endpoint %llu failed status=0x%x flags=0x%x\n",
             (unsigned long long)endpoint->EndpointId,
             status,
             flags);
    KeSignalEvent(endpoint->WorkEvent);
}

static const NTL_DDK_AUDIO gAudioDdk = {
    .RegisterEndpoint = KiAudioDdkRegisterEndpoint,
    .UnregisterEndpoint = KiAudioDdkUnregisterEndpoint,
    .NotifyPeriod = KiAudioDdkNotifyPeriod,
    .SetEndpointAvailable = KiAudioDdkSetEndpointAvailable,
    .ReportEndpointFailure = KiAudioDdkReportEndpointFailure,
};

// Initializes the one kernel audio registry.
void KeAudioInitialize(void) {
    if (gAudioInitialized)
        KiAudioBug("KeAudioInitialize", "duplicate initialization", 0);
    LIST_INIT(&gAudioEndpointList);
    gAudioInitialized = 1;
}

// Returns the immutable provider-facing audio table.
const NTL_DDK_AUDIO* KeAudioGetDdk(void) {
    return &gAudioDdk;
}

// Returns the current default endpoint identifier.
uint32_t KeAudioGetDefaultEndpointId(void) {
    uintptr_t flags = KeAcquireSpinlock(&gAudioRegistryLock);
    uint32_t endpointId = gAudioDefaultEndpointId;
    KeReleaseSpinlock(&gAudioRegistryLock, flags);
    return endpointId;
}

// Copies endpoint snapshots without retaining registry locks across passive operations.
KSTATUS KeAudioQueryEndpoints(KE_AUDIO_ENDPOINT_INFO* endpoints,
                              uint32_t capacity,
                              uint32_t* countOut) {
    if (!countOut || (capacity && !endpoints))
        return NTLSTATUS_INVALID_PARAMETER;

    IO_AUDIO_ENDPOINT* references[KE_AUDIO_MAX_ENDPOINTS];
    uint32_t count = 0;
    uint32_t defaultId = 0;
    uintptr_t flags = KeAcquireSpinlock(&gAudioRegistryLock);
    defaultId = gAudioDefaultEndpointId;
    for (LIST_ENTRY* link = gAudioEndpointList.Fwd;
         link != &gAudioEndpointList && count < KE_AUDIO_MAX_ENDPOINTS;
         link = link->Fwd) {
        IO_AUDIO_ENDPOINT* endpoint = CONTAINING_RECORD(link, IO_AUDIO_ENDPOINT, RegistryLink);
        if (ObTryReferenceObject(&endpoint->Header))
            references[count++] = endpoint;
    }
    KeReleaseSpinlock(&gAudioRegistryLock, flags);

    *countOut = count;
    uint32_t copyCount = capacity < count ? capacity : count;
    for (uint32_t i = 0; i < count; i++) {
        IO_AUDIO_ENDPOINT* endpoint = references[i];
        if (i < copyCount) {
            KE_AUDIO_ENDPOINT_INFO* info = &endpoints[i];
            memset(info, 0, sizeof(*info));
            flags = KeAcquireSpinlock(&gAudioRegistryLock);
            info->EndpointId = endpoint->EndpointId;
            info->Kind = endpoint->Kind;
            info->State = endpoint->State;
            info->Capabilities = endpoint->Capabilities;
            info->HardwareFormat = endpoint->HardwareFormat;
            info->PeriodCount = endpoint->PeriodCount;
            info->FramesPerPeriod = endpoint->FramesPerPeriod;
            info->Available = endpoint->Available;
            info->IsDefault = endpoint->EndpointId == defaultId;
            info->FailureStatus = endpoint->FailureStatus;
            KeReleaseSpinlock(&gAudioRegistryLock, flags);

            uintptr_t streamFlags = KeAcquireSpinlock(&endpoint->StreamListLock);
            for (LIST_ENTRY* link = endpoint->StreamList.Fwd;
                 link != &endpoint->StreamList;
                 link = link->Fwd)
                info->StreamCount++;
            KeReleaseSpinlock(&endpoint->StreamListLock, streamFlags);

            flags = KeAcquireSpinlock(&endpoint->NotifyLock);
            info->ActiveStreamCount = endpoint->ActiveStreamCount;
            info->HardwareRunning = endpoint->HardwareRunning;
            info->MasterMuted = endpoint->MasterMuted;
            info->MasterHardwareGainMilliDb = endpoint->MasterHardwareGainMilliDb;
            info->MasterRequestedVolume = endpoint->MasterRequestedVolume;
            info->PeriodsMixed = endpoint->PeriodsMixed;
            info->PeriodsCompleted = endpoint->PeriodsCompleted;
            info->FramesPresented = endpoint->FramesPresented;
            info->HardwarePositionFrames = endpoint->HardwarePositionFrames;
            info->InterruptCount = endpoint->InterruptCount;
            info->LastPresentationTimestampTicks = endpoint->LastPresentationTimestampTicks;
            info->SilenceFramesInserted = endpoint->SilenceFramesInserted;
            info->Underruns = endpoint->Underruns;
            info->DiscontinuityGeneration = endpoint->DiscontinuityGeneration;
            KeReleaseSpinlock(&endpoint->NotifyLock, flags);
        }
        ObDereferenceObject(&endpoint->Header);
    }
    return capacity < count ? NTLSTATUS_BUFFER_TOO_SMALL : NTLSTATUS_SUCCESS;
}

// Creates one logical render stream with a fixed-capacity source ring.
KSTATUS KeAudioCreateStream(uint32_t endpointId,
                            const IO_AUDIO_FORMAT* format,
                            KE_AUDIO_STREAM** outStream) {
    if (!outStream || !KiAudioValidateSourceFormat(format))
        return NTLSTATUS_INVALID_PARAMETER;
    *outStream = (KE_AUDIO_STREAM*)0;
    IO_AUDIO_ENDPOINT* endpoint = KiAudioReferenceEndpointById(endpointId);
    if (!endpoint)
        return NTLSTATUS_NOT_FOUND;

    KE_AUDIO_STREAM* stream = (KE_AUDIO_STREAM*)ObAllocateObject(
        ObjectTypeAudioStream,
        sizeof(KE_AUDIO_STREAM));
    if (!stream) {
        ObDereferenceObject(&endpoint->Header);
        return NTLSTATUS_NO_MEMORY;
    }
    stream->Header.Destroy = KiAudioStreamDestroy;
    LIST_INIT(&stream->EndpointLink);
    stream->Endpoint = endpoint;
    stream->State = KeAudioStreamCreated;
    stream->Format = *format;
    stream->FrameBytes = KiAudioFrameBytes(format);
    stream->ResampleStepQ32 = ((uint64_t)format->SampleRate << 32) /
                              KE_AUDIO_OUTPUT_SAMPLE_RATE;
    stream->WaitMask = KE_AUDIO_WAIT_WRITABLE;
    stream->WaitWritableFrames = 1;
    stream->Volume = 1.0f;
    stream->CurrentLeftGain = 1.0f;
    stream->CurrentRightGain = 1.0f;
    stream->TargetLeftGain = 1.0f;
    stream->TargetRightGain = 1.0f;

    KSTATUS status = KeMutexCreate(&stream->Lock);
    if (!KSUCCESS(status)) {
        ObDereferenceObject(&stream->Header);
        return status;
    }
    status = KeEventCreate(EventManualReset, 1, &stream->WaitEvent);
    if (!KSUCCESS(status)) {
        ObDereferenceObject(&stream->Header);
        return status;
    }
    stream->Ring = (uint8_t*)MmAllocatePoolTag(
        (size_t)KE_AUDIO_STREAM_RING_FRAMES * stream->FrameBytes,
        KE_AUDIO_RING_TAG);
    if (!stream->Ring) {
        ObDereferenceObject(&stream->Header);
        return NTLSTATUS_NO_MEMORY;
    }
    memset(stream->Ring,
           0,
           (size_t)KE_AUDIO_STREAM_RING_FRAMES * stream->FrameBytes);

    uintptr_t registryFlags = KeAcquireSpinlock(&gAudioRegistryLock);
    int endpointReady = endpoint->Registered && endpoint->State == KeAudioEndpointReady;
    uint32_t streamCount = 0;
    uintptr_t streamFlags = KeAcquireSpinlock(&endpoint->StreamListLock);
    if (endpointReady) {
        for (LIST_ENTRY* link = endpoint->StreamList.Fwd;
             link != &endpoint->StreamList;
             link = link->Fwd)
            streamCount++;
    }
    if (!endpointReady || streamCount >= KE_AUDIO_MAX_STREAMS_PER_ENDPOINT) {
        KSTATUS createStatus = !endpointReady
                             ? (KFAILED(endpoint->FailureStatus)
                                ? endpoint->FailureStatus
                                : NTLSTATUS_DEVICE_REMOVED)
                             : NTLSTATUS_NO_MEMORY;
        KeReleaseSpinlock(&endpoint->StreamListLock, streamFlags);
        KeReleaseSpinlock(&gAudioRegistryLock, registryFlags);
        ObDereferenceObject(&stream->Header);
        return createStatus;
    }
    KeListInsertTailChecked(&endpoint->StreamList, &stream->EndpointLink);
    KeReleaseSpinlock(&endpoint->StreamListLock, streamFlags);
    KeReleaseSpinlock(&gAudioRegistryLock, registryFlags);

    _InterlockedIncrement64(&gAudioCoreStats.StreamsCreated);
    *outStream = stream;
    return NTLSTATUS_SUCCESS;
}

// Returns the stream event used by future waitable handles.
EVENT* KeAudioStreamWaitEvent(KE_AUDIO_STREAM* stream) {
    return stream ? stream->WaitEvent : (EVENT*)0;
}

// Arms one wait condition while holding the stream state that drives its event.
KSTATUS KeAudioArmStreamWait(KE_AUDIO_STREAM* stream,
                             const KE_AUDIO_STREAM_WAIT_CONDITION* condition) {
    if (!stream || !condition || !condition->Mask ||
        (condition->Mask & ~KE_AUDIO_WAIT_VALID_MASK) != 0 ||
        ((condition->Mask & KE_AUDIO_WAIT_WRITABLE) &&
         (!condition->WritableFrames ||
          condition->WritableFrames > KE_AUDIO_STREAM_RING_FRAMES)))
        return NTLSTATUS_INVALID_PARAMETER;

    KiAudioAcquireMutex(stream->Lock, "KeAudioArmStreamWait");
    if (stream->State == KeAudioStreamClosed) {
        KiAudioReleaseMutex(stream->Lock);
        return NTLSTATUS_OBJECT_DEAD;
    }
    stream->WaitMask = condition->Mask;
    stream->WaitWritableFrames = condition->WritableFrames;
    stream->WaitConsumedFrames = condition->ConsumedFrames;
    stream->WaitPresentedFrames = condition->PresentedFrames;
    stream->WaitDrainedGeneration = condition->DrainedGeneration;
    stream->WaitDiscontinuityGeneration = condition->DiscontinuityGeneration;
    KiAudioRefreshStreamEventLocked(stream);
    KiAudioReleaseMutex(stream->Lock);
    return NTLSTATUS_SUCCESS;
}

// Copies a bounded source-frame run into one stream ring.
KSTATUS KeAudioWriteStream(KE_AUDIO_STREAM* stream,
                           const void* frames,
                           uint32_t requestedFrames,
                           uint32_t* writtenFramesOut) {
    if (!stream || !writtenFramesOut || (requestedFrames && !frames))
        return NTLSTATUS_INVALID_PARAMETER;
    *writtenFramesOut = 0;
    if (!requestedFrames)
        return NTLSTATUS_SUCCESS;

    KiAudioAcquireMutex(stream->Lock, "KeAudioWriteStream");
    if (stream->State == KeAudioStreamFailed || stream->State == KeAudioStreamClosed) {
        KSTATUS status = stream->FailureStatus ? stream->FailureStatus : NTLSTATUS_OBJECT_DEAD;
        KiAudioReleaseMutex(stream->Lock);
        return status;
    }
    if (stream->State == KeAudioStreamDraining) {
        KiAudioReleaseMutex(stream->Lock);
        return NTLSTATUS_INVALID_PARAMETER;
    }

    uint32_t writable = KE_AUDIO_STREAM_RING_FRAMES - stream->BufferedFrames;
    if (!writable) {
        KiAudioRefreshStreamEventLocked(stream);
        KiAudioReleaseMutex(stream->Lock);
        return NTLSTATUS_WOULD_BLOCK;
    }
    uint32_t toWrite = requestedFrames < writable ? requestedFrames : writable;
    uint32_t firstFrames = KE_AUDIO_STREAM_RING_FRAMES - stream->WriteFrame;
    if (firstFrames > toWrite) firstFrames = toWrite;
    size_t firstBytes = (size_t)firstFrames * stream->FrameBytes;
    memcpy(stream->Ring + (size_t)stream->WriteFrame * stream->FrameBytes,
           frames,
           firstBytes);
    uint32_t secondFrames = toWrite - firstFrames;
    if (secondFrames) {
        memcpy(stream->Ring,
               (const uint8_t*)frames + firstBytes,
               (size_t)secondFrames * stream->FrameBytes);
    }
    stream->WriteFrame = (stream->WriteFrame + toWrite) % KE_AUDIO_STREAM_RING_FRAMES;
    stream->BufferedFrames += toWrite;
    stream->FramesSubmitted += toWrite;
    *writtenFramesOut = toWrite;
    KiAudioRefreshStreamEventLocked(stream);
    int active = KiAudioStreamStateIsActive(stream->State);
    KiAudioReleaseMutex(stream->Lock);

    if (active)
        KeSignalEvent(stream->Endpoint->WorkEvent);
    return NTLSTATUS_SUCCESS;
}

// Starts one created or stopped stream.
KSTATUS KeAudioStartStream(KE_AUDIO_STREAM* stream) {
    if (!stream) return NTLSTATUS_INVALID_PARAMETER;
    KiAudioAcquireMutex(stream->Lock, "KeAudioStartStream");
    if (stream->State != KeAudioStreamCreated && stream->State != KeAudioStreamStopped) {
        KSTATUS status = stream->State == KeAudioStreamFailed
                       ? stream->FailureStatus
                       : NTLSTATUS_INVALID_PARAMETER;
        KiAudioReleaseMutex(stream->Lock);
        return status;
    }
    KiAudioSetStreamStateLocked(stream, KeAudioStreamRunning);
    stream->FailureStatus = NTLSTATUS_SUCCESS;
    KiAudioRefreshStreamEventLocked(stream);
    KiAudioReleaseMutex(stream->Lock);
    _InterlockedIncrement64(&gAudioCoreStats.Starts);
    return NTLSTATUS_SUCCESS;
}

// Pauses one running stream without discarding source frames.
KSTATUS KeAudioPauseStream(KE_AUDIO_STREAM* stream) {
    if (!stream) return NTLSTATUS_INVALID_PARAMETER;
    KiAudioAcquireMutex(stream->Lock, "KeAudioPauseStream");
    if (stream->State != KeAudioStreamRunning) {
        KSTATUS status = stream->State == KeAudioStreamFailed
                       ? stream->FailureStatus
                       : NTLSTATUS_INVALID_PARAMETER;
        KiAudioReleaseMutex(stream->Lock);
        return status;
    }
    KiAudioSetStreamStateLocked(stream, KeAudioStreamPaused);
    KiAudioRefreshStreamEventLocked(stream);
    KiAudioReleaseMutex(stream->Lock);
    _InterlockedIncrement64(&gAudioCoreStats.Pauses);
    return NTLSTATUS_SUCCESS;
}

// Resumes one paused stream.
KSTATUS KeAudioResumeStream(KE_AUDIO_STREAM* stream) {
    if (!stream) return NTLSTATUS_INVALID_PARAMETER;
    KiAudioAcquireMutex(stream->Lock, "KeAudioResumeStream");
    if (stream->State != KeAudioStreamPaused) {
        KSTATUS status = stream->State == KeAudioStreamFailed
                       ? stream->FailureStatus
                       : NTLSTATUS_INVALID_PARAMETER;
        KiAudioReleaseMutex(stream->Lock);
        return status;
    }
    KiAudioSetStreamStateLocked(stream, KeAudioStreamRunning);
    KiAudioRefreshStreamEventLocked(stream);
    KiAudioReleaseMutex(stream->Lock);
    _InterlockedIncrement64(&gAudioCoreStats.Resumes);
    return NTLSTATUS_SUCCESS;
}

// Stops accepting writes and plays all currently buffered frames.
KSTATUS KeAudioDrainStream(KE_AUDIO_STREAM* stream) {
    if (!stream) return NTLSTATUS_INVALID_PARAMETER;
    KiAudioAcquireMutex(stream->Lock, "KeAudioDrainStream");
    if (stream->State == KeAudioStreamRunning ||
        stream->State == KeAudioStreamPaused) {
        KiAudioSetStreamStateLocked(stream, KeAudioStreamDraining);
        if (KiAudioDrainIsCompleteLocked(stream))
            KiAudioCompleteDrainLocked(stream);
    } else {
        KSTATUS status = stream->State == KeAudioStreamFailed
                       ? stream->FailureStatus
                       : NTLSTATUS_INVALID_PARAMETER;
        KiAudioReleaseMutex(stream->Lock);
        return status;
    }
    KiAudioRefreshStreamEventLocked(stream);
    KiAudioReleaseMutex(stream->Lock);
    KeSignalEvent(stream->Endpoint->WorkEvent);
    _InterlockedIncrement64(&gAudioCoreStats.Drains);
    return NTLSTATUS_SUCCESS;
}

// Stops future mixing and discards source frames not yet committed to endpoint periods.
KSTATUS KeAudioStopStream(KE_AUDIO_STREAM* stream) {
    if (!stream) return NTLSTATUS_INVALID_PARAMETER;
    KiAudioAcquireMutex(stream->Lock, "KeAudioStopStream");
    if (stream->State == KeAudioStreamFailed || stream->State == KeAudioStreamClosed) {
        KSTATUS status = stream->FailureStatus ? stream->FailureStatus : NTLSTATUS_OBJECT_DEAD;
        KiAudioReleaseMutex(stream->Lock);
        return status;
    }
    stream->FramesDiscarded += stream->BufferedFrames;
    KiAudioSetStreamStateLocked(stream, KeAudioStreamStopped);
    stream->ReadFrame = 0;
    stream->WriteFrame = 0;
    stream->BufferedFrames = 0;
    stream->ResamplePositionQ32 = 0;
    stream->ConsecutiveUnderrunPeriods = 0;
    stream->DiscontinuityGeneration++;
    KiAudioRefreshStreamEventLocked(stream);
    KiAudioReleaseMutex(stream->Lock);
    KeSignalEvent(stream->Endpoint->WorkEvent);
    _InterlockedIncrement64(&gAudioCoreStats.Stops);
    return NTLSTATUS_SUCCESS;
}

// Resets one live stream and invalidates presentation accounting from earlier periods.
KSTATUS KeAudioResetStream(KE_AUDIO_STREAM* stream) {
    if (!stream) return NTLSTATUS_INVALID_PARAMETER;
    KiAudioAcquireMutex(stream->Lock, "KeAudioResetStream");
    if (stream->State == KeAudioStreamFailed || stream->State == KeAudioStreamClosed) {
        KSTATUS status = stream->FailureStatus ? stream->FailureStatus : NTLSTATUS_OBJECT_DEAD;
        KiAudioReleaseMutex(stream->Lock);
        return status;
    }
    stream->BufferGeneration++;
    KiAudioSetStreamStateLocked(stream, KeAudioStreamStopped);
    stream->ReadFrame = 0;
    stream->WriteFrame = 0;
    stream->BufferedFrames = 0;
    stream->ResamplePositionQ32 = 0;
    stream->FramesSubmitted = 0;
    stream->FramesConsumed = 0;
    stream->FramesPresented = 0;
    stream->FramesDiscarded = 0;
    stream->OutputFramesMixed = 0;
    stream->SilenceFramesInserted = 0;
    stream->Underruns = 0;
    stream->ConsecutiveUnderrunPeriods = 0;
    stream->DiscontinuityGeneration++;
    memset(stream->Ring,
           0,
           (size_t)KE_AUDIO_STREAM_RING_FRAMES * stream->FrameBytes);
    KiAudioRefreshStreamEventLocked(stream);
    KiAudioReleaseMutex(stream->Lock);
    KeSignalEvent(stream->Endpoint->WorkEvent);
    _InterlockedIncrement64(&gAudioCoreStats.Resets);
    return NTLSTATUS_SUCCESS;
}

// Updates per-stream volume, linear balance pan, and mute targets.
KSTATUS KeAudioSetStreamVolume(KE_AUDIO_STREAM* stream,
                               float volume,
                               float pan,
                               bool muted) {
    if (!stream || !KiAudioFloatIsFinite(volume) || !KiAudioFloatIsFinite(pan) ||
        volume < 0.0f || volume > 1.0f || pan < -1.0f || pan > 1.0f)
        return NTLSTATUS_INVALID_PARAMETER;
    KiAudioAcquireMutex(stream->Lock, "KeAudioSetStreamVolume");
    if (stream->State == KeAudioStreamFailed || stream->State == KeAudioStreamClosed) {
        KSTATUS status = stream->FailureStatus ? stream->FailureStatus : NTLSTATUS_OBJECT_DEAD;
        KiAudioReleaseMutex(stream->Lock);
        return status;
    }
    stream->Volume = volume;
    stream->Pan = pan;
    stream->Muted = muted ? 1u : 0u;
    if (stream->State == KeAudioStreamCreated || stream->State == KeAudioStreamStopped) {
        KiAudioComputeStreamTargets(stream->Volume,
                                    stream->Pan,
                                    stream->Muted,
                                    &stream->CurrentLeftGain,
                                    &stream->CurrentRightGain);
        stream->TargetLeftGain = stream->CurrentLeftGain;
        stream->TargetRightGain = stream->CurrentRightGain;
        stream->GainRampRemaining = 0;
        stream->LeftGainStep = 0.0f;
        stream->RightGainStep = 0.0f;
    } else {
        KiAudioBeginStreamGainRampLocked(stream);
    }
    KiAudioReleaseMutex(stream->Lock);
    KeSignalEvent(stream->Endpoint->WorkEvent);
    return NTLSTATUS_SUCCESS;
}

// Updates endpoint master software gain and separate logical mute state.
KSTATUS KeAudioSetMasterVolume(uint32_t endpointId, float volume, bool muted) {
    if (!KiAudioFloatIsFinite(volume) || volume < 0.0f || volume > 1.0f)
        return NTLSTATUS_INVALID_PARAMETER;
    IO_AUDIO_ENDPOINT* endpoint = KiAudioReferenceEndpointById(endpointId);
    if (!endpoint)
        return NTLSTATUS_NOT_FOUND;

    KiAudioAcquireMutex(endpoint->ControlLock, "KeAudioSetMasterVolume");
    float softwareGain = muted ? 0.0f
                               : KiAudioSoftwareGainForVolume(endpoint, volume);
    uintptr_t registryFlags = KeAcquireSpinlock(&gAudioRegistryLock);
    if (endpoint->State != KeAudioEndpointReady) {
        KSTATUS failure = endpoint->FailureStatus;
        KeReleaseSpinlock(&gAudioRegistryLock, registryFlags);
        KiAudioReleaseMutex(endpoint->ControlLock);
        ObDereferenceObject(&endpoint->Header);
        return KFAILED(failure) ? failure : NTLSTATUS_OBJECT_DEAD;
    }

    uintptr_t flags = KeAcquireSpinlock(&endpoint->NotifyLock);
    endpoint->MasterRequestedVolume = volume;
    endpoint->MasterTargetGain = softwareGain;
    if (endpoint->HardwareRunning) {
        endpoint->MasterGainStep =
            (endpoint->MasterTargetGain - endpoint->MasterCurrentGain) /
            (float)KE_AUDIO_GAIN_RAMP_FRAMES;
        endpoint->MasterRampRemaining = KE_AUDIO_GAIN_RAMP_FRAMES;
    } else {
        endpoint->MasterCurrentGain = endpoint->MasterTargetGain;
        endpoint->MasterGainStep = 0.0f;
        endpoint->MasterRampRemaining = 0;
    }
    endpoint->MasterGainGeneration++;
    endpoint->MasterMuted = muted ? 1u : 0u;
    KeReleaseSpinlock(&endpoint->NotifyLock, flags);
    KeReleaseSpinlock(&gAudioRegistryLock, registryFlags);
    KiAudioReleaseMutex(endpoint->ControlLock);

    KeSignalEvent(endpoint->WorkEvent);
    ObDereferenceObject(&endpoint->Header);
    return NTLSTATUS_SUCCESS;
}

// Copies one stream snapshot under its priority-inheriting mutex.
KSTATUS KeAudioQueryStream(KE_AUDIO_STREAM* stream, KE_AUDIO_STREAM_INFO* infoOut) {
    if (!stream || !infoOut)
        return NTLSTATUS_INVALID_PARAMETER;
    KiAudioAcquireMutex(stream->Lock, "KeAudioQueryStream");
    memset(infoOut, 0, sizeof(*infoOut));
    infoOut->State = stream->State;
    infoOut->Format = stream->Format;
    infoOut->CapacityFrames = KE_AUDIO_STREAM_RING_FRAMES;
    infoOut->BufferedFrames = stream->BufferedFrames;
    infoOut->WritableFrames = KE_AUDIO_STREAM_RING_FRAMES - stream->BufferedFrames;
    infoOut->FramesSubmitted = stream->FramesSubmitted;
    infoOut->FramesConsumed = stream->FramesConsumed;
    infoOut->FramesPresented = stream->FramesPresented;
    infoOut->FramesDiscarded = stream->FramesDiscarded;
    infoOut->OutputFramesMixed = stream->OutputFramesMixed;
    infoOut->SilenceFramesInserted = stream->SilenceFramesInserted;
    infoOut->Underruns = stream->Underruns;
    infoOut->DrainedGeneration = stream->DrainedGeneration;
    infoOut->DiscontinuityGeneration = stream->DiscontinuityGeneration;
    infoOut->FailureStatus = stream->FailureStatus;
    infoOut->Volume = stream->Volume;
    infoOut->Pan = stream->Pan;
    infoOut->Muted = stream->Muted;
    KiAudioReleaseMutex(stream->Lock);
    return NTLSTATUS_SUCCESS;
}