WDF_MEMORY_DESCRIPTOR structure (wdfmemory.h)

[Applies to KMDF and UMDF]

The WDF_MEMORY_DESCRIPTOR structure describes a memory buffer.

Syntax

typedef struct _WDF_MEMORY_DESCRIPTOR {
  WDF_MEMORY_DESCRIPTOR_TYPE Type;
  union {
    struct {
      PVOID Buffer;
      ULONG Length;
    } BufferType;
    struct {
      PMDL  Mdl;
      ULONG BufferLength;
    } MdlType;
    struct {
      WDFMEMORY         Memory;
      PWDFMEMORY_OFFSET Offsets;
    } HandleType;
  } u;
} WDF_MEMORY_DESCRIPTOR, *PWDF_MEMORY_DESCRIPTOR;

Members

Type

A WDF_MEMORY_DESCRIPTOR_TYPE-typed value that identifies the type of buffer description that this WDF_MEMORY_DESCRIPTOR structure contains.

u

A union of three structures, one of which describes a buffer.

u.BufferType

If the Type member is WdfMemoryDescriptorTypeBuffer, the members of the BufferType structure describe a buffer. This structure contains the following two members:

u.BufferType.Buffer

A pointer to a buffer.

u.BufferType.Length

The length, in bytes, of the buffer.

u.MdlType

If the Type member is WdfMemoryDescriptorTypeMdl, the members of the MdlType structure describe a buffer. This structure contains the following two members:

u.MdlType.Mdl

A pointer to a memory descriptor list (MDL).

u.MdlType.BufferLength

The length, in bytes, of the buffer.

u.HandleType

If the Type member is WdfMemoryDescriptorTypeHandle, the members of the HandleType structure describe a buffer. This structure contains the following two members:

u.HandleType.Memory

A handle to a framework memory object.

u.HandleType.Offsets

A pointer to a WDFMEMORY_OFFSET structure that describes a subsection of the buffer that is represented by the memory object.

Remarks

The WDF_MEMORY_DESCRIPTOR structure is used as input to several of the framework's I/O target object methods and USB device object methods.

To initialize a WDF_MEMORY_DESCRIPTOR structure, your driver should call WDF_MEMORY_DESCRIPTOR_INIT_BUFFER, or WDF_MEMORY_DESCRIPTOR_INIT_MDL, or WDF_MEMORY_DESCRIPTOR_INIT_HANDLE.

Requirements

See also

WDFMEMORY_OFFSET

WDF_MEMORY_DESCRIPTOR_TYPE