PCPROPERTY_REQUEST

The PCPROPERTY_REQUEST structure specifies a property request.

typedef struct _PCPROPERTY_REQUEST
{
  PUNKNOWN  MajorTarget;
  PUNKNOWN  MinorTarget;
  ULONG  Node;
  const PCPROPERTY_ITEM  *PropertyItem;
  ULONG  Verb;
  ULONG  InstanceSize;
  PVOID  Instance;
  ULONG  ValueSize;
  PVOID  Value;
  PIRP  Irp;
} PCPROPERTY_REQUEST, *PPCPROPERTY_REQUEST;

Members

MajorTarget

IUnknown pointer to the main miniport object. This member contains the UnknownMiniport parameter value that the adapter driver previously passed to the IPort::Init method.

MinorTarget

IUnknown pointer to a stream object that is associated with the MajorTarget miniport object. If the target for the property request is a pin instance, this member contains the stream-object pointer that the IMiniportXxx::NewStream method previously output to the port driver (for example, the IMiniportWaveCyclic::NewStream method's Stream parameter). Otherwise (if the target for the property request is a filter instance), this member is NULL.

Node

Specifies a node ID. This member identifies the target node for the request. If the target is not a node, this member is set to ULONG(-1).

PropertyItem

Pointer to the property item, which is a structure of type PCPROPERTY_ITEM.

Verb

Specifies the type of property request. Verb is set to the bitwise OR of one or more of the following flag bits from header file ks.h:

• KSPROPERTY_TYPE_GET
• KSPROPERTY_TYPE_SET
• KSPROPERTY_TYPE_SETSUPPORT
• KSPROPERTY_TYPE_BASICSUPPORT
• KSPROPERTY_TYPE_RELATIONS
• KSPROPERTY_TYPE_SERIALIZESET
• KSPROPERTY_TYPE_UNSERIALIZESET
• KSPROPERTY_TYPE_SERIALIZERAW
• KSPROPERTY_TYPE_UNSERIALIZERAW
• KSPROPERTY_TYPE_SERIALIZESIZE
• KSPROPERTY_TYPE_DEFAULTVALUES
• KSPROPERTY_TYPE_TOPOLOGY

These flags are described in KSPROPERTY.

InstanceSize

Specifies the size in bytes of the property-instance buffer.

Instance

Pointer to the property-instance buffer

ValueSize

Specifies the size in bytes of the property-value buffer.

Value

Pointer to the property-value buffer

Irp

Pointer to the IRP containing the client's original property request

Comments

This is the structure that the port driver passes to the miniport driver's property-handler routine. The PCPROPERTY_ITEM structure contains a function pointer to a property handler that takes a PCPROPERTY_REQUEST pointer as its only call parameter. The port driver allocates a PCPROPERTY_REQUEST structure, extracts the relevant information from the original property request (which the Irp member points to), and loads the information into this structure before calling the handler.

In WDM audio, the target of a property request can be either a filter instance or a pin instance. The target can also include a node ID.

In the client's original property request, the property-instance data always begins with a KSPROPERTY or KSNODEPROPERTY structure, but can include additional information. The port driver adjusts the PCPROPERTY_REQUEST structure's Instance member to point to this additional information, if it exists. For details, see Audio Property Handlers.

The MajorTarget and MinorTarget members are IUnknown pointers to the main miniport object and an associated stream object, respectively. The property handler can query these objects for their miniport and stream interfaces. If the target for the property request is a filter instance, MajorTarget points to the miniport object for that filter instance, and MinorTarget is NULL. If the target is a pin instance, MinorTarget points to the stream object for that pin, and MajorTarget points to the miniport object for the filter that the pin is attached to.

For example, if the target for the property request is a pin instance on a WaveCyclic filter:

• The handler can call QueryInterface on the MajorTarget object's IUnknown interface to obtain a reference to the object's IMiniportWaveCyclic interface.
• The handler can call QueryInterface on the MinorTarget object's IUnknown interface to obtain a reference to the object's IMiniportWaveCyclicStream interface.

For background information on audio properties, see Properties of Audio Filters, Pins, and Nodes. For a list of the available audio-specific properties, see Audio Drivers Property Sets.

See Also

PCPROPERTY_ITEM, KSPROPERTY, KSNODEPROPERTY, KSNODEPROPERTY_AUDIO_CHANNEL