# IOUserAudioDriver A DriverKit provider object that manages communications with an audio device. ``` class IOUserAudioDriver; ``` ## Overview For the Core Audio host to match against this driver, add the following keys to `IOKitPersonalities`, in the driver’s `Info.plist` file: ```swift IOUserAudioDriverUserClientProperties IOClass IOUserUserClient IOUserClass IOUserAudioDriverUserClient ``` After matching the host with the driver, the AudioDriverKit framework creates the connection to the Core Audio HAL as soon as the calls [`NewUserClient`](/documentation/AudioDriverKit/IOUserAudioDriver/NewUserClient). The driver extension must have the `com.apple.developer.driverkit.allow-any-userclient-access` entitlement. ## Topics ### Running the Driver Service [`virtual bool init();`](/documentation/AudioDriverKit/IOUserAudioDriver/init) Handles the basic initialization of the service. [`virtual kern_return_t Start(IOService *provider);`](/documentation/AudioDriverKit/IOUserAudioDriver/Start) Starts the current service and associates it with the specified provider. [`virtual kern_return_t Stop(IOService *provider);`](/documentation/AudioDriverKit/IOUserAudioDriver/Stop) Stops the service associated with the specified provider. [`virtual void free();`](/documentation/AudioDriverKit/IOUserAudioDriver/free) Performs any final cleanup for the service. ### Getting Information About the Class [`IOUserAudioClassID GetClassID();`](/documentation/AudioDriverKit/IOUserAudioDriver/GetClassID) Gets the audio class identifier of the object. [`IOUserAudioClassID GetBaseClassID();`](/documentation/AudioDriverKit/IOUserAudioDriver/GetBaseClassID) Gets the audio class identifier of the base class object. [`enum IOUserAudioClassID : uint32_t;`](/documentation/AudioDriverKit/AudioDriverKit/IOUserAudioClassID) An identifier for the type of audio object. [`OSSharedPtr GetWorkQueue();`](/documentation/AudioDriverKit/IOUserAudioDriver/GetWorkQueue) Gets the work queue created by the audio object, as a pointer to a dispatch queue. [`OSSharedPtr GetName();`](/documentation/AudioDriverKit/IOUserAudioDriver/GetName) Gets the name of the driver. [`kern_return_t SetName(OSString *in_name);`](/documentation/AudioDriverKit/IOUserAudioDriver/SetName) Sets the name of the driver. ### Getting the Driver’s Audio Object Identifier [`constexpr const IOUserAudioObjectID kIOUserAudioObjectIDDriver;`](/documentation/AudioDriverKit/AudioDriverKit/kIOUserAudioObjectIDDriver) The audio object ID of the driver. ### Starting and Stopping the Driver [`virtual kern_return_t StartDevice(IOUserAudioObjectID in_object_id, IOUserAudioStartStopFlags in_flags);`](/documentation/AudioDriverKit/IOUserAudioDriver/StartDevice) Tells the driver to start I/O on an audio device or audio clock device. [`virtual kern_return_t StopDevice(IOUserAudioObjectID in_object_id, IOUserAudioStartStopFlags in_flags);`](/documentation/AudioDriverKit/IOUserAudioDriver/StopDevice) Tells the driver to stop I/O on an audio device or audio clock device. [`typedef uint32_t IOUserAudioObjectID;`](/documentation/AudioDriverKit/AudioDriverKit/IOUserAudioObjectID) An identifier that provides a handle on a specific audio object. [`enum IOUserAudioStartStopFlags : uint64_t;`](/documentation/AudioDriverKit/AudioDriverKit/IOUserAudioStartStopFlags) Values that indicate I/O starts or stops. ### Creating a New Client [`virtual kern_return_t NewUserClient(uint32_t in_type, IOUserClient **out_user_client);`](/documentation/AudioDriverKit/IOUserAudioDriver/NewUserClient) Requests the creation of a new user client for the service. ### Working with Transport Type [`IOUserAudioTransportType GetTransportType();`](/documentation/AudioDriverKit/IOUserAudioDriver/GetTransportType) Gets the transport type of the driver. [`kern_return_t SetTransportType(IOUserAudioTransportType in_transport_type);`](/documentation/AudioDriverKit/IOUserAudioDriver/SetTransportType) Set the transport type of the driver. [`enum IOUserAudioTransportType : uint32_t;`](/documentation/AudioDriverKit/AudioDriverKit/IOUserAudioTransportType) The type of transport to deliver audio. ### Working with Audio Objects [`kern_return_t AddObject(IOUserAudioObject *in_object);`](/documentation/AudioDriverKit/IOUserAudioDriver/AddObject) Adds an audio object to the driver. [`kern_return_t RemoveObject(IOUserAudioObject *in_object);`](/documentation/AudioDriverKit/IOUserAudioDriver/RemoveObject) Removes an audio object from the driver. [`OSSharedPtr GetAudioObjectForObjectID(IOUserAudioObjectID in_object_id);`](/documentation/AudioDriverKit/IOUserAudioDriver/GetAudioObjectForObjectID) Gets a pointer to an audio object, given the object’s identifier. ### Communicating with the Host [`kern_return_t PropertiesChanged(IOUserAudioObjectID in_object_id, IOUserAudioObjectPropertySelector *in_properties, uint32_t in_num_properties);`](/documentation/AudioDriverKit/IOUserAudioDriver/PropertiesChanged) Informs the host when the state of an object in the driver changes. [`typedef uint32_t IOUserAudioObjectPropertySelector;`](/documentation/AudioDriverKit/AudioDriverKit/IOUserAudioObjectPropertySelector) A four character code which, along with the scope and element, specific piece of information about an audio object. ### Working with Custom Properties [`kern_return_t AddCustomProperty(IOUserAudioCustomProperty *in_custom_property);`](/documentation/AudioDriverKit/IOUserAudioDriver/AddCustomProperty) Adds a custom property object to the driver. [`kern_return_t RemoveCustomProperty(IOUserAudioCustomProperty *in_custom_property);`](/documentation/AudioDriverKit/IOUserAudioDriver/RemoveCustomProperty) Removes a previously-added custom property object from the driver. [`class IOUserAudioCustomProperty;`](/documentation/AudioDriverKit/IOUserAudioCustomProperty) A custom property to associate with audio objects. ## Relationships ### Inherits From [`IOService`](/documentation/DriverKit/IOService) --- Copyright © 2026 Apple Inc. 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