ACX_PROPERTY_ITEM structure (acxrequest.h)

Article
09/11/2024

The ACX_PROPERTY_ITEM structure describes a property item that is the target of an ACX request. A property represents a capability or control-state setting that belongs to an ACX object, such as a circuit, element, pin, stream, etc. For more information, see KS Properties.

Syntax

typedef struct _ACX_PROPERTY_ITEM {
  const GUID                     *Set;
  ULONG                          Id;
  ULONG                          Flags;
  PFN_ACX_OBJECT_PROCESS_REQUEST EvtAcxObjectProcessRequest;
  PVOID                          Reserved;
  ULONG                          ControlCb;
  ULONG                          ValueCb;
  ULONG                          ValueType;
} ACX_PROPERTY_ITEM, *PACX_PROPERTY_ITEM;

Members

Set

Specifies a GUID that identifies a KS (kernel streaming) property item set. For example, the KSPROPSETID_Topology set ID is the set of topology circuit properties For more information, see KSPROPERTY structure.

Id

Specifies the member of the property set. For example, KSPROPERTY_TOPOLOGY_NODES of the topology property set is used to retrieve the list of KS NODES (ACXELEMENTS).

Flags

The Flags field is used to set the following Flags defined in the AcxRequest header.


#define ACX_PROPERTY_ITEM_FLAG_NONE             0x00000000
#define ACX_PROPERTY_ITEM_FLAG_GET              0x00000001 // KSPROPERTY_TYPE_GET
#define ACX_PROPERTY_ITEM_FLAG_SET              0x00000002 // KSPROPERTY_TYPE_SET
#define ACX_PROPERTY_ITEM_FLAG_BASICSUPPORT     0x00000200 // KSPROPERTY_TYPE_BASICSUPPORT

ACX_PROPERTY_ITEM_FLAG_GET - Retrieves the value of the specified property item.

ACX_PROPERTY_ITEM_FLAG_SET - Sets the value of the specified property item.

ACX_PROPERTY_ITEM_FLAG_BASICSUPPORT - Queries the request types that the driver handles for this property item. Returns KSPROPERTY_TYPE_GET or KSPROPERTY_TYPE_SET or both. All property sets must support this flag. And some object may return more info, such as volume ranges etc.

EvtAcxObjectProcessRequest

The EVT_ACX_OBJECT_PROCESS_REQUEST callback property handler associated with this item.

Reserved

This field is reserved.

ControlCb

The minimum count in bytes (size) of the additional Control buffer. Set to zero if no minimum value.

ValueCb

The minimum count in bytes (size) of the Value buffer. Set to zero if there is no minimum value.

ValueType

The VARENUM type of the property. Set to 0, i.e., VT_EMPTY to use default behavior.

Remarks

Example

Example usage is shown below.


#define ACX_PROPERTY_ITEM_FLAG_NONE             0x00000000
#define ACX_PROPERTY_ITEM_FLAG_GET              0x00000001 // KSPROPERTY_TYPE_GET
#define ACX_PROPERTY_ITEM_FLAG_SET              0x00000002 // KSPROPERTY_TYPE_SET
#define ACX_PROPERTY_ITEM_FLAG_BASICSUPPORT     0x00000200 // KSPROPERTY_TYPE_BASICSUPPORT

// Pin properties.
static ACX_PROPERTY_ITEM PinProperties[] =
{
    {
        &KSPROPSETID_Pin,
        KSPROPERTY_PIN_DATAFLOW,
        ACX_PROPERTY_ITEM_FLAG_GET,
        &AfxPin::EvtPinDataflowCallback,
        NULL,                       // Reserved
        0,                          // ControlCb
        sizeof(KSPIN_DATAFLOW),     // ValueCb
    },
};

ACX requirements

Minimum ACX version: 1.0

For more information about ACX versions, see ACX version overview.

Requirements

Requirement	Value
Header	acxrequest.h

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