SimpleAudio/Driver/SimpleAudioDriver.cpp

/*
     File: SimpleAudioDriver.cpp 
 Abstract:  Part of SimpleAudioDriver Example  
  Version: 1.0.1 
  
 Disclaimer: IMPORTANT:  This Apple software is supplied to you by Apple 
 Inc. ("Apple") in consideration of your agreement to the following 
 terms, and your use, installation, modification or redistribution of 
 this Apple software constitutes acceptance of these terms.  If you do 
 not agree with these terms, please do not use, install, modify or 
 redistribute this Apple software. 
  
 In consideration of your agreement to abide by the following terms, and 
 subject to these terms, Apple grants you a personal, non-exclusive 
 license, under Apple's copyrights in this original Apple software (the 
 "Apple Software"), to use, reproduce, modify and redistribute the Apple 
 Software, with or without modifications, in source and/or binary forms; 
 provided that if you redistribute the Apple Software in its entirety and 
 without modifications, you must retain this notice and the following 
 text and disclaimers in all such redistributions of the Apple Software. 
 Neither the name, trademarks, service marks or logos of Apple Inc. may 
 be used to endorse or promote products derived from the Apple Software 
 without specific prior written permission from Apple.  Except as 
 expressly stated in this notice, no other rights or licenses, express or 
 implied, are granted by Apple herein, including but not limited to any 
 patent rights that may be infringed by your derivative works or by other 
 works in which the Apple Software may be incorporated. 
  
 The Apple Software is provided by Apple on an "AS IS" basis.  APPLE 
 MAKES NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION 
 THE IMPLIED WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY AND FITNESS 
 FOR A PARTICULAR PURPOSE, REGARDING THE APPLE SOFTWARE OR ITS USE AND 
 OPERATION ALONE OR IN COMBINATION WITH YOUR PRODUCTS. 
  
 IN NO EVENT SHALL APPLE BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL 
 OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 
 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
 INTERRUPTION) ARISING IN ANY WAY OUT OF THE USE, REPRODUCTION, 
 MODIFICATION AND/OR DISTRIBUTION OF THE APPLE SOFTWARE, HOWEVER CAUSED 
 AND WHETHER UNDER THEORY OF CONTRACT, TORT (INCLUDING NEGLIGENCE), 
 STRICT LIABILITY OR OTHERWISE, EVEN IF APPLE HAS BEEN ADVISED OF THE 
 POSSIBILITY OF SUCH DAMAGE. 
  
 Copyright (C) 2013 Apple Inc. All Rights Reserved. 
  
*/
/*==================================================================================================
    SimpleAudioDriver.cpp
==================================================================================================*/
 
//==================================================================================================
//  Includes
//==================================================================================================
 
//  Self Include
#include "SimpleAudioDriver.h"
 
//  System Includes
#include <IOKit/IOBufferMemoryDescriptor.h>
#include <IOKit/IOCommandGate.h>
#include <IOKit/IOTimerEventSource.h>
 
//==================================================================================================
//  SimpleAudioDriver
//==================================================================================================
 
OSDefineMetaClassAndStructors(com_apple_audio_SimpleAudioDriver, IOService)
 
bool    SimpleAudioDriver::start(IOService* inProvider)
{
    //  start the superclass
    bool theAnswer = IOService::start(inProvider);
    if(theAnswer)
    {
        //  create the work loop
        mWorkLoop = IOWorkLoop::workLoop();
        FailIfNULL(mWorkLoop, theAnswer = kIOReturnNoResources, Failure, "SimpleAudioDriver::start: couldn't allocate the work loop");
        
        //  create the command gate
        mCommandGate = IOCommandGate::commandGate(this);
        FailIfNULL(mWorkLoop, theAnswer = kIOReturnNoResources, Failure, "SimpleAudioDriver::start: couldn't allocate the command gate");
        
        //  attach it to the work loop
        mWorkLoop->addEventSource(mCommandGate);
        
        //  initialize the stuff tracked by the IORegistry
        mSampleRate = 44100;
        setProperty(kSimpleAudioDriver_RegistryKey_SampleRate, mSampleRate, sizeof(mSampleRate) * 8);
        
        mIOBufferFrameSize = 16384;
        setProperty(kSimpleAudioDriver_RegistryKey_RingBufferFrameSize, mIOBufferFrameSize, sizeof(mIOBufferFrameSize) * 8);
        
        char theDeviceUID[128];
        snprintf(theDeviceUID, 128, "SimpleAudioDevice-%d", static_cast<int>(random() % 100000));
        setProperty(kSimpleAudioDriver_RegistryKey_DeviceUID, theDeviceUID);
 
        //  allocate the IO buffers
        IOReturn theError = allocateBuffers();
        FailIfError(theError, theAnswer = false, Failure, "SimpleAudioDriver::start: allocating the buffers failed");
        
        //  initialize the timer that stands in for a real interrupt
        theError = initTimer();
        FailIfError(theError, freeBuffers(); theAnswer = false, Failure, "SimpleAudioDriver::start: initializing the timer failed");
        
        //  initialize the controls
        theError = initControls();
        FailIfError(theError, theAnswer = false, Failure, "SimpleAudioDriver::start: initializing the controls failed");
        
        //  publish ourselves
        registerService();
    }
 
    return theAnswer;
 
Failure:
    if(mCommandGate != NULL)
    {
        if(mWorkLoop != NULL)
        {
            mWorkLoop->removeEventSource(mCommandGate);
            mCommandGate->release();
            mCommandGate = NULL;
        }
    }
    
    if(mWorkLoop != NULL)
    {
        mWorkLoop->release();
        mWorkLoop = NULL;
    }
    
    freeBuffers();
    destroyTimer();
    
    return theAnswer;
}
 
void    SimpleAudioDriver::stop(IOService* inProvider)
{
    //  tear things down
    freeBuffers();
    destroyTimer();
    if(mCommandGate != NULL)
    {
        if(mWorkLoop != NULL)
        {
            mWorkLoop->removeEventSource(mCommandGate);
            mCommandGate->release();
            mCommandGate = NULL;
        }
    }
    if(mWorkLoop != NULL)
    {
        mWorkLoop->release();
        mWorkLoop = NULL;
    }
    IOService::stop(inProvider);
}
 
IOBufferMemoryDescriptor*   SimpleAudioDriver::getBuffer(int inBufferType)
{
    //  we gate the external methods onto the work loop for thread safety
    IOBufferMemoryDescriptor* theAnswer = NULL;
    if(mCommandGate != NULL)
    {
        mCommandGate->runAction(_getBuffer, &inBufferType, &theAnswer);
    }
    return theAnswer;
}
 
IOReturn SimpleAudioDriver::startHardware()
{
    //  we gate the external methods onto the work loop for thread safety
    IOReturn theAnswer = kIOReturnSuccess;
    if(mCommandGate != NULL)
    {
        theAnswer = mCommandGate->runAction(_startHardware);
    }
    else
    {
        theAnswer = kIOReturnNoResources;
    }
    return theAnswer;
}
 
void SimpleAudioDriver::stopHardware()
{
    //  we gate the external methods onto the work loop for thread safety
    if(mCommandGate != NULL)
    {
        mCommandGate->runAction(_stopHardware);
    }
}
 
IOReturn SimpleAudioDriver::setSampleRate(UInt64 inNewSampleRate)
{
    //  we gate the external methods onto the work loop for thread safety
    IOReturn theAnswer = kIOReturnSuccess;
    if(mCommandGate != NULL)
    {
        theAnswer = mCommandGate->runAction(_setSampleRate, &inNewSampleRate);
    }
    else
    {
        theAnswer = kIOReturnNoResources;
    }
    return theAnswer;
}
 
IOReturn SimpleAudioDriver::_getBuffer(OSObject* inTarget, void* inArg0, void* inArg1, void* inArg2, void* inArg3)
{
    #pragma unused(inArg2, inArg3)
    IOReturn theAnswer = kIOReturnSuccess;
    SimpleAudioDriver* theDriver = NULL;
    const int* theBufferType = NULL;
    IOBufferMemoryDescriptor** theBuffer = NULL;
    
    //  cast the arguments back to what they need to be
    theDriver = OSDynamicCast(SimpleAudioDriver, inTarget);
    FailIfNULL(theDriver, theAnswer = kIOReturnBadArgument, Done, "SimpleAudioDriver::_startHardware: this is not a SimpleAudioDriver");
    
    theBufferType = reinterpret_cast<const int*>(inArg0);
    FailIfNULL(theBufferType, theAnswer = kIOReturnBadArgument, Done, "SimpleAudioDriver::_startHardware: no buffer type");
 
    theBuffer = reinterpret_cast<IOBufferMemoryDescriptor**>(inArg1);
    FailIfNULL(theBuffer, theAnswer = kIOReturnBadArgument, Done, "SimpleAudioDriver::_startHardware: no buffer");
    
    switch(*theBufferType)
    {
        case kSimpleAudioDriver_Buffer_Status:
            *theBuffer = theDriver->mStatusBuffer;
            break;
            
        case kSimpleAudioDriver_Buffer_Input:
            *theBuffer = theDriver->mInputBuffer;
            break;
            
        case kSimpleAudioDriver_Buffer_Output:
            *theBuffer = theDriver->mOutputBuffer;
            break;
    };
 
Done:
    return theAnswer;
}
    
IOReturn SimpleAudioDriver::_startHardware(OSObject* inTarget, void* inArg0, void* inArg1, void* inArg2, void* inArg3)
{
    //  This driver uses a work loop timer to simulate an interrupt to driver the timing
    
    #pragma unused(inArg0, inArg1, inArg2, inArg3)
    IOReturn theAnswer = kIOReturnSuccess;
    
    //  cast the arguments back to what they need to be
    SimpleAudioDriver* theDriver = OSDynamicCast(SimpleAudioDriver, inTarget);
    FailIfNULL(theDriver, theAnswer = kIOReturnBadArgument, Done, "SimpleAudioDriver::_startHardware: this is not a SimpleAudioDriver");
    
    if(!theDriver->mIsRunning)
    {
        if((theDriver->mInputBuffer != NULL) && (theDriver->mOutputBuffer != NULL))
        {
            //  clear the buffers
            bzero(theDriver->mInputBuffer->getBytesNoCopy(), theDriver->mInputBuffer->getCapacity());
            bzero(theDriver->mOutputBuffer->getBytesNoCopy(), theDriver->mOutputBuffer->getCapacity());
            
            //  start the timer
            theAnswer = theDriver->startTimer();
            FailIfError(theAnswer, , Done, "SimpleAudioDriver::_startHardware: starting the timer failed");
            
            //  update the is running state
            theDriver->mIsRunning = true;
        }
        else
        {
            theAnswer = kIOReturnNoResources;
        }
    }
 
Done:
    return theAnswer;
}
 
IOReturn SimpleAudioDriver::_stopHardware(OSObject* inTarget, void* inArg0, void* inArg1, void* inArg2, void* inArg3)
{
    //  cast the arguments back to what they need to be
    #pragma unused(inArg0, inArg1, inArg2, inArg3)
    SimpleAudioDriver* theDriver = OSDynamicCast(SimpleAudioDriver, inTarget);
    if((theDriver != NULL) && theDriver->mIsRunning)
    {
        //  all we need to do is stop the timer
        theDriver->stopTimer();
        theDriver->mIsRunning = false;
    }
    return kIOReturnSuccess;
}
 
IOReturn    SimpleAudioDriver::_setSampleRate(OSObject* inTarget, void* inArg0, void* inArg1, void* inArg2, void* inArg3)
{
    #pragma unused(inArg1, inArg2, inArg3)
    IOReturn theAnswer = kIOReturnSuccess;
    SimpleAudioDriver* theDriver = NULL;
    const UInt64* theNewSampleRate = NULL;
    
    //  cast the arguments back to what they need to be
    theDriver = OSDynamicCast(SimpleAudioDriver, inTarget);
    FailIfNULL(theDriver, theAnswer = kIOReturnBadArgument, Done, "SimpleAudioDriver::_setSampleRate: this is not a SimpleAudioDriver");
    
    theNewSampleRate = reinterpret_cast<const UInt64*>(inArg0);
    FailIfNULL(theNewSampleRate, theAnswer = kIOReturnBadArgument, Done, "SimpleAudioDriver::_setSampleRate: no new sample rate");
    
    //  make sure that IO is stopped
    FailIf(theDriver->mIsRunning, theAnswer = kIOReturnNotPermitted, Done, "SimpleAudioDriver::_setSampleRate: can't change the sample rate while IO is running");
 
    //  make sure the sample rate is something we support
    if((*theNewSampleRate == 44100) || (*theNewSampleRate == 48000))
    {
        theDriver->mSampleRate = *theNewSampleRate;
        theDriver->setProperty(kSimpleAudioDriver_RegistryKey_SampleRate, theDriver->mSampleRate, sizeof(theDriver->mSampleRate) * 8);
        theDriver->updateTimer();
    }
    else
    {
        theAnswer = kIOReturnUnsupported;
    }
 
Done:
    return theAnswer;
}
 
IOReturn SimpleAudioDriver::getVolume(int inVolumeID, UInt32& outVolume)
{
    //  we gate the external methods onto the work loop for thread safety
    IOReturn theAnswer = 0;
    if(mCommandGate != NULL)
    {
        theAnswer = mCommandGate->runAction(_getVolume, &inVolumeID, &outVolume);
    }
    return theAnswer;
}
 
IOReturn SimpleAudioDriver::setVolume(int inVolumeID, UInt32 inNewVolume)
{
    //  we gate the external methods onto the work loop for thread safety
    IOReturn theAnswer = kIOReturnSuccess;
    if(mCommandGate != NULL)
    {
        theAnswer = mCommandGate->runAction(_setVolume, &inVolumeID, &inNewVolume);
    }
    else
    {
        theAnswer = kIOReturnNoResources;
    }
    return theAnswer;
}
 
IOReturn    SimpleAudioDriver::_getVolume(OSObject* inTarget, void* inArg0, void* inArg1, void* inArg2, void* inArg3)
{
    #pragma unused(inArg2, inArg3)
    IOReturn theAnswer = kIOReturnSuccess;
    SimpleAudioDriver* theDriver = NULL;
    const int* theControlID = NULL;
    UInt32* theControlValue = NULL;
    
    //  cast the arguments back to what they need to be
    theDriver = OSDynamicCast(SimpleAudioDriver, inTarget);
    FailIfNULL(theDriver, theAnswer = kIOReturnBadArgument, Done, "SimpleAudioDriver::_startHardware: this is not a SimpleAudioDriver");
    
    theControlID = reinterpret_cast<const int*>(inArg0);
    FailIfNULL(theControlID, theAnswer = kIOReturnBadArgument, Done, "SimpleAudioDriver::_startHardware: no control ID");
 
    theControlValue = reinterpret_cast<UInt32*>(inArg1);
    FailIfNULL(theControlValue, theAnswer = kIOReturnBadArgument, Done, "SimpleAudioDriver::_startHardware: no control value");
    
    switch(*theControlID)
    {
        case kSimpleAudioDriver_Control_MasterInputVolume:
            *theControlValue = theDriver->mMasterInputVolume;
            break;
            
        case kSimpleAudioDriver_Control_MasterOutputVolume:
            *theControlValue = theDriver->mMasterOutputVolume;
            break;
    };
 
Done:
    return theAnswer;
}
 
IOReturn    SimpleAudioDriver::_setVolume(OSObject* inTarget, void* inArg0, void* inArg1, void* inArg2, void* inArg3)
{
    #pragma unused(inArg2, inArg3)
    IOReturn theAnswer = kIOReturnSuccess;
    SimpleAudioDriver* theDriver = NULL;
    const int* theControlID = NULL;
    const UInt32* theNewControlValue = NULL;
    
    //  cast the arguments back to what they need to be
    theDriver = OSDynamicCast(SimpleAudioDriver, inTarget);
    FailIfNULL(theDriver, theAnswer = kIOReturnBadArgument, Done, "SimpleAudioDriver::_startHardware: this is not a SimpleAudioDriver");
    
    theControlID = reinterpret_cast<const int*>(inArg0);
    FailIfNULL(theControlID, theAnswer = kIOReturnBadArgument, Done, "SimpleAudioDriver::_startHardware: no control ID");
 
    theNewControlValue = reinterpret_cast<UInt32*>(inArg1);
    FailIfNULL(theNewControlValue, theAnswer = kIOReturnBadArgument, Done, "SimpleAudioDriver::_startHardware: no control value");
    
    switch(*theControlID)
    {
        case kSimpleAudioDriver_Control_MasterInputVolume:
            theDriver->mMasterInputVolume = *theNewControlValue;
            if(theDriver->mMasterInputVolume > kSimpleAudioDriver_Control_MaxRawVolumeValue)
            {
                theDriver->mMasterInputVolume = kSimpleAudioDriver_Control_MaxRawVolumeValue;
            }
            break;
            
        case kSimpleAudioDriver_Control_MasterOutputVolume:
            theDriver->mMasterOutputVolume = *theNewControlValue;
            if(theDriver->mMasterOutputVolume > kSimpleAudioDriver_Control_MaxRawVolumeValue)
            {
                theDriver->mMasterOutputVolume = kSimpleAudioDriver_Control_MaxRawVolumeValue;
            }
            break;
    };
 
Done:
    return theAnswer;
}
 
IOReturn SimpleAudioDriver::allocateBuffers()
{
    IOReturn theAnswer = kIOReturnSuccess;
    
    //  The status buffer holds the zero time stamp when IO is running
    mStatusBuffer = IOBufferMemoryDescriptor::withOptions(kIOMemoryKernelUserShared, sizeof(SimpleAudioDriverStatus));
    FailIfNULL(mStatusBuffer, theAnswer = kIOReturnNoMemory, Failure, "SimpleAudioDriver::allocateBuffers: failed to allocate the status buffer");
    bzero(mStatusBuffer->getBytesNoCopy(), mStatusBuffer->getCapacity());
 
    //  These are the ring buffers for transmitting the audio data
    
    //  Note that for this driver the samples are always 16 bit stereo  
    mInputBuffer = IOBufferMemoryDescriptor::withOptions(kIOMemoryKernelUserShared, mIOBufferFrameSize * 2 * 2);
    FailIfNULL(mInputBuffer, theAnswer = kIOReturnNoMemory, Failure, "SimpleAudioDriver::allocateBuffers: failed to allocate the input buffer");
    bzero(mInputBuffer->getBytesNoCopy(), mInputBuffer->getCapacity());
 
    mOutputBuffer = IOBufferMemoryDescriptor::withOptions(kIOMemoryKernelUserShared, mIOBufferFrameSize * 2 * 2);
    FailIfNULL(mOutputBuffer, theAnswer = kIOReturnNoMemory, Failure, "SimpleAudioDriver::allocateBuffers: failed to allocate the output buffer");
    bzero(mOutputBuffer->getBytesNoCopy(), mOutputBuffer->getCapacity());
    
    return kIOReturnSuccess;
 
Failure:
    if(mStatusBuffer != NULL)
    {
        mStatusBuffer->release();
        mStatusBuffer = NULL;
    }
    
    if(mInputBuffer != NULL)
    {
        mInputBuffer->release();
        mInputBuffer = NULL;
    }
    
    if(mOutputBuffer != NULL)
    {
        mOutputBuffer->release();
        mOutputBuffer = NULL;
    }
    
    return theAnswer;
}
 
void    SimpleAudioDriver::freeBuffers()
{
    if(mStatusBuffer != NULL)
    {
        mStatusBuffer->release();
        mStatusBuffer = NULL;
    }
    
    if(mInputBuffer != NULL)
    {
        mInputBuffer->release();
        mInputBuffer = NULL;
    }
    
    if(mOutputBuffer != NULL)
    {
        mOutputBuffer->release();
        mOutputBuffer = NULL;
    }
}
 
IOReturn SimpleAudioDriver::initTimer()
{
    IOReturn theAnswer = kIOReturnSuccess;
    
    //  create the timer event source that will be our fake interrupt
    mTimerEventSource = IOTimerEventSource::timerEventSource(this, timerFired);
    FailIfNULL(mTimerEventSource, theAnswer = kIOReturnNoResources, Failure, "SimpleAudioDriver::initTimer: couldn't allocate the timer event source");
    
    //  add the timer to the work loop
    mWorkLoop->addEventSource(mTimerEventSource);
 
    //  calculate how many ticks are in each buffer
    updateTimer();
    
    return kIOReturnSuccess;
 
Failure:
    if(mTimerEventSource != NULL)
    {
        if(mWorkLoop != NULL)
        {
            mWorkLoop->removeEventSource(mTimerEventSource);
        }
        mTimerEventSource->release();
        mTimerEventSource = NULL;
    }
 
    if(mWorkLoop != NULL)
    {
        mWorkLoop->release();
        mWorkLoop = NULL;
    }
    
    return theAnswer;
}
 
void    SimpleAudioDriver::destroyTimer()
{
    if(mTimerEventSource != NULL)
    {
        if(mWorkLoop != NULL)
        {
            mWorkLoop->removeEventSource(mTimerEventSource);
        }
        mTimerEventSource->release();
        mTimerEventSource = NULL;
    }
 
    if(mWorkLoop != NULL)
    {
        mWorkLoop->release();
        mWorkLoop = NULL;
    }
}
 
IOReturn SimpleAudioDriver::startTimer()
{
    IOReturn theAnswer = kIOReturnSuccess;
    
    if((mStatusBuffer != NULL) && (mTimerEventSource != NULL))
    {
        //  clear the status buffer
        SimpleAudioDriverStatus* theStatus = (SimpleAudioDriverStatus*)mStatusBuffer->getBytesNoCopy();
        theStatus->mSampleTime = 0;
        theStatus->mHostTime = 0;
        
        //  calculate how many ticks are in each buffer
        struct mach_timebase_info theTimeBaseInfo;
        clock_timebase_info(&theTimeBaseInfo);
        mHostTicksPerBuffer = (mIOBufferFrameSize * 1000000000ULL) / mSampleRate;
        mHostTicksPerBuffer = (mHostTicksPerBuffer * theTimeBaseInfo.denom) / theTimeBaseInfo.numer;
            
        //  start the timer, the first time stamp will be taken when it goes off
        union { UInt64 mUInt64; AbsoluteTime mAbsoluteTime; } theNextWakeTime;
        theNextWakeTime.mUInt64 = mHostTicksPerBuffer;
        mTimerEventSource->setTimeout(theNextWakeTime.mAbsoluteTime);
    }
    else
    {
        theAnswer = kIOReturnNoResources;
    }
    
    return theAnswer;
}
 
void    SimpleAudioDriver::stopTimer()
{
    if(mTimerEventSource != NULL)
    {
        mTimerEventSource->cancelTimeout();
    }
}
 
void    SimpleAudioDriver::updateTimer()
{
    struct mach_timebase_info theTimeBaseInfo;
    clock_timebase_info(&theTimeBaseInfo);
    mHostTicksPerBuffer = (mIOBufferFrameSize * 1000000000ULL) / mSampleRate;
    mHostTicksPerBuffer = (mHostTicksPerBuffer * theTimeBaseInfo.denom) / theTimeBaseInfo.numer;
}
 
void    SimpleAudioDriver::timerFired(OSObject* inTarget, IOTimerEventSource* inSender)
{
    //  validate the engine
    SimpleAudioDriver* theDriver = OSDynamicCast(SimpleAudioDriver, inTarget);
    if((theDriver != NULL) && (theDriver->mStatusBuffer != NULL))
    {
        //  get the status buffer
        SimpleAudioDriverStatus* theStatus = (SimpleAudioDriverStatus*)theDriver->mStatusBuffer->getBytesNoCopy();
        
        //  get the current time
        UInt64 theCurrentTime = 0;
        clock_get_uptime((AbsoluteTime*)&theCurrentTime);
        
        //  increment the time stamps
        if(theStatus->mHostTime != 0)
        {
            theStatus->mSampleTime += theDriver->mIOBufferFrameSize;
            theStatus->mHostTime += theDriver->mHostTicksPerBuffer;
        }
        else
        {
            //  but not if it's the first one
            theStatus->mSampleTime = 0;
            theStatus->mHostTime = theCurrentTime;
        }
        
        //  set the timer to go off in one buffer
        union { UInt64 mUInt64; AbsoluteTime mAbsoluteTime; } theNextWakeTime;
        theNextWakeTime.mUInt64 = theStatus->mHostTime + theDriver->mHostTicksPerBuffer;
        inSender->wakeAtTime(theNextWakeTime.mAbsoluteTime);
    }
}
 
IOReturn    SimpleAudioDriver::initControls()
{
    mMasterInputVolume = kSimpleAudioDriver_Control_MaxRawVolumeValue;
    mMasterOutputVolume = kSimpleAudioDriver_Control_MaxRawVolumeValue;
    return kIOReturnSuccess;
}