PcAddAdapterDevice function

The PcAddAdapterDevice function adds an adapter device to the WDM device stack.


NTSTATUS PcAddAdapterDevice(
  _In_ PDRIVER_OBJECT   DriverObject,
  _In_ PDEVICE_OBJECT   PhysicalDeviceObject,
  _In_ ULONG            MaxObjects,
  _In_ ULONG            DeviceExtensionSize


DriverObject [in]

Pointer to the driver object. This pointer is passed as a parameter to the adapter's AddDevice handler. The driver object is a system structure of type DRIVER_OBJECT.

PhysicalDeviceObject [in]

Pointer to the device's physical device object (PDO). PortCls passes this pointer as a call parameter to the adapter's AddDevice handler. The PDO is a system structure of type DEVICE_OBJECT.

StartDevice [in]

Pointer to the function that the operating system calls in order to start the device. For more information, see the following Remarks section.

MaxObjects [in]

Specifies the maximum number of subdevices to be registered by calls to PcRegisterSubdevice. This count sets the upper limit to the total number of miniport objects that the adapter driver can instantiate.

DeviceExtensionSize [in]

Specifies the device extension size. Use zero for default size. See the following Remarks section for user-supplied extension sizes.

Return value

PcAddAdapterDevice returns STATUS_SUCCESS if the call was successful. Otherwise, it returns an appropriate error code.


This function does most of the work that the audio adapter driver's AddDevice handler needs to perform. PcAddAdapterDevice creates the device object, initializes the device context, and attaches the device object to the device stack.

An adapter driver calls PcAddAdapterDevice when it receives a call to its AddDevice handler. The adapter driver typically installs the AddDevice handler by calling PcInitializeAdapterDriver, although the driver can also install the handler by other means. PcAddAdapterDevice creates the functional device object (FDO) for the PDO that was passed to the AddDevice handler.

DeviceExtensionSize is typically zero. Some adapter drivers might need to reserve additional space in the device extension, in which case they should specify a DeviceExtensionSize greater than PORT_CLASS_DEVICE_EXTENSION_SIZE, which is the default size. Any value greater than zero and less than PORT_CLASS_DEVICE_EXTENSION_SIZE is illegal. Adapter drivers are free to use any part of the device extension after offset PORT_CLASS_DEVICE_EXTENSION_SIZE. They are also free to use bytes in the offset range of 16 to 31 inclusive in a system with 32-bit addressing and bytes in the offset range 32 to 63 in a system with 64-bit addressing. If the extension is regarded as an array of ULONG_PTR, array elements four through seven are available for use by the adapter driver.

The StartDevice parameter points to a function of type PCPFNSTARTDEVICE, which header file portcls.h defines as:

      IN PDEVICE_OBJECT  DeviceObject,
      IN PIRP  Irp,
      IN PRESOURCELIST  ResourceList

For more information about PcAddAdapterDevice and the adapter driver's device-startup and AddDevice routines, see Startup Sequence.

The following example code shows how an adapter driver can use the DeviceExtensionSize parameter to append 64 bytes of device-specific extension data to the end of the storage block that PortCls allocates for the device context:

  #define MY_EXTENSION_SIZE  64
  NTSTATUS  ntstatus = PcAddAdapterDevice(DriverObject, PhysicalDeviceObject,
                                          MyStartDevice, MAX_MINIPORTS,
                                          MY_EXTENSION_SIZE + PORT_CLASS_DEVICE_EXTENSION_SIZE);

The PcAddAdapterDevice call above is similar to the example in Startup Sequence, except that the last parameter that is passed to PcAddAdapterDevice is nonzero.

The adapter driver can then access the device-specific extension data, as shown in the following code fragment:

  PVOID  pMyExtensionData = (PVOID)((PCHAR)FunctionalDeviceObject->DeviceExtension +

Variable FunctionalDeviceObject is a pointer to the audio adapter's FDO, and pMyExtensionData is a temporary pointer to the extension data. Avoid confusing the FDO with the PDO, which belongs to the PCI bus driver. The adapter driver must not modify data in the PDO because doing so corrupts memory owned by the PCI bus driver and can cause the system to crash.


Target platform


Minimum support

Available starting in Windows 2000. 


Portcls.h (include Portcls.h)





See also




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