WdfFdoInitAllocAndQueryProperty function (wdffdo.h)

[Applies to KMDF and UMDF]

The WdfFdoInitAllocAndQueryProperty method allocates a buffer and retrieves a specified device property.

Syntax

NTSTATUS WdfFdoInitAllocAndQueryProperty(
  [in]           PWDFDEVICE_INIT          DeviceInit,
  [in]           DEVICE_REGISTRY_PROPERTY DeviceProperty,
  [in]           POOL_TYPE                PoolType,
  [in, optional] PWDF_OBJECT_ATTRIBUTES   PropertyMemoryAttributes,
  [out]          WDFMEMORY                *PropertyMemory
);

Parameters

[in] DeviceInit

A pointer to a WDFDEVICE_INIT structure that the driver obtained from its EvtDriverDeviceAdd callback function.

[in] DeviceProperty

A DEVICE_REGISTRY_PROPERTY-typed enumerator value that identifies the device property to be retrieved.

[in] PoolType

A POOL_TYPE-typed enumerator value that specifies the type of memory to be allocated.

[in, optional] PropertyMemoryAttributes

A pointer to a caller-allocated WDF_OBJECT_ATTRIBUTES structure that describes object attributes for the memory object that WdfFdoInitAllocAndQueryProperty will allocate. This parameter is optional and can be WDF_NO_OBJECT_ATTRIBUTES.

[out] PropertyMemory

A pointer to a WDFMEMORY-typed location that receives a handle to a framework memory object.

Return value

If the operation succeeds, the method returns STATUS_SUCCESS. Additional return values include:

The method might also return other NTSTATUS values.

Remarks

The driver must call WdfFdoInitAllocAndQueryProperty before calling WdfDeviceCreate. For more information about calling WdfDeviceCreate, see Creating a Framework Device Object.

After calling WdfDeviceCreate, a driver can obtain device property information by calling WdfDeviceAllocAndQueryProperty.

For more information about the WdfFdoInitAllocAndQueryProperty method, see Creating Device Objects in a Function Driver.

Alternatively, you can use WdfFdoInitAllocAndQueryPropertyEx to access device properties that are exposed through the Unified Property Model.

Examples

The following code example calls WdfFdoInitAllocAndQueryProperty to obtain a handle to a framework memory object that contains the name of a device's setup class. Then, the example calls WdfMemoryGetBuffer to obtain a pointer to the buffer that contains the setup class name's Unicode string.

NTSTATUS  status = STATUS_SUCCESS;
PVOID  pMemoryBuffer = NULL;
WDFMEMORY  memory = NULL;

status = WdfFdoInitAllocAndQueryProperty(
                                         DeviceInit,
                                         DevicePropertyClassName, 
                                         NonPagedPool,
                                         WDF_NO_OBJECT_ATTRIBUTES,
                                         &memory
                                         );
if(NT_SUCCESS(status)){
 pMemoryBuffer = WdfMemoryGetBuffer(
                                    memory,
                                    NULL
                                    );
}

Requirements

See also

WdfDeviceAllocAndQueryProperty

WdfFdoInitQueryProperty