FltEnumerateInstanceInformationByDeviceObject function (fltkernel.h)

Article
10/21/2021

The FltEnumerateInstanceInformationByDeviceObject routine provides information about minifilter driver instances and legacy filter drivers that are attached to the volume related to a specified device object.

Syntax

NTSTATUS FLTAPI FltEnumerateInstanceInformationByDeviceObject(
  [in]  PDEVICE_OBJECT             DeviceObject,
  [in]  ULONG                      Index,
  [in]  INSTANCE_INFORMATION_CLASS InformationClass,
  [out] PVOID                      Buffer,
  [in]  ULONG                      BufferSize,
  [out] PULONG                     BytesReturned
);

Parameters

[in] DeviceObject

The device object for the related file object or volume.

[in] Index

Zero-based index of the minifilter driver instance or legacy filter driver for which the information is requested.

[in] InformationClass

Type of information to be returned for the minifilter driver instance or legacy filter driver. This parameter can have one of the following values.

Value	Meaning
InstanceBasicInformation	The buffer pointed to by the Buffer parameter receives an INSTANCE_BASIC_INFORMATION structure for a minifilter instance. Legacy filter drivers are ignored.
InstanceFullInformation	The buffer pointed to by the Buffer parameter receives an INSTANCE_FULL_INFORMATION structure for a minifilter instance. Legacy filter drivers are ignored.
InstancePartialInformation	The buffer pointed to by the Buffer parameter receives an INSTANCE_PARTIAL_INFORMATION structure for a minifilter instance. Legacy filter drivers are ignored.
InstanceAggregateStandardInformation	The buffer pointed to by the Buffer parameter receives an INSTANCE_AGGREGATE_STANDARD_INFORMATION structure for a minifilter driver instance or legacy filter driver.

[out] Buffer

Pointer to a caller-allocated buffer that receives the requested information. The type of the information returned in the buffer is defined by the InformationClass parameter.

[in] BufferSize

Size, in bytes, of the buffer that the Buffer parameter points to. The caller should set this parameter according to the given InformationClass value.

[out] BytesReturned

Pointer to a caller-allocated variable that receives the number of bytes returned in the buffer that Buffer points to. If the input value of BufferSize is too small, FltEnumerateInstanceInformationByDeviceObject returns STATUS_BUFFER_TOO_SMALL and sets this variable to the number of bytes required to store the requested information. This parameter is required and cannot be NULL.

Return value

FltEnumerateInstanceInformationByDeviceObject returns STATUS_SUCCESS or an appropriate NTSTATUS value, such as one of the following:

Return code	Description
STATUS_BUFFER_TOO_SMALL	The buffer that the Buffer parameter points to is not large enough to store the requested information.
STATUS_FLT_DELETING_OBJECT	A matching minifilter instance was found, but it is being torn down. Note that this return value does not apply to legacy filter drivers because legacy filter drivers cannot be unloaded.
STATUS_INVALID_PARAMETER	An invalid value was specified for the InformationClass parameter.
STATUS_NO_MORE_ENTRIES	There are no more entries in the volume's instance/filter list.
STATUS_FLT_VOLUME_NOT_FOUND	No related volume was found for DeviceObject.
STATUS_FLT_INTERNAL_ERROR	DeviceObject is not a valid volume device object. -or- The volume related to DeviceObject was registered but does not have any filter instances attached.

Remarks

Using the Index parameter is simply a way for FltEnumerateInstanceInformationByDeviceObject to select among minifilter driver instances and legacy filter drivers in the instance/filter list for the volume that is related to DeviceObject. Because the minifilter driver instances in the instance/filter list can change at any time, two calls to FltEnumerateInstanceInformationByDeviceObject with the same Index and DeviceObject values are not guaranteed to return the same result.

This routine will return both legacy filter driver information and minifilter driver instance information when the value of the InformationClass parameter is InstanceAggregateStandardInformation.

Requirements

Requirement	Value
Minimum supported client	Available starting with Windows 8.
Target Platform	Universal
Header	fltkernel.h (include Fltkernel.h)
Library	FltMgr.lib
IRQL	<= APC_LEVEL