DMA_DES structure (cfgmgr32.h)

The DMA_DES structure is used for specifying either a resource list or a resource requirements list that describes direct memory access (DMA) channel usage for a device instance. For more information about resource lists and resource requirements lists, see Hardware Resources.

Syntax

typedef struct DMA_Des_s {
  DWORD DD_Count;
  DWORD DD_Type;
  DWORD DD_Flags;
  ULONG DD_Alloc_Chan;
} DMA_DES, *PDMA_DES;

Members

DD_Count

For a resource list:

Zero.

For a resource requirements list:

The number of elements in the DMA_RESOURCE structure.

DD_Type

Must be set to the constant value DType_Range.

DD_Flags

One bit flag from each of the flag sets described in the following table.

	Flag	Definition
Channel Width Flags
	fDD_BYTE	8-bit DMA channel.
	fDD_WORD	16-bit DMA channel.
	fDD_DWORD	32-bit DMA channel.
	fDD_BYTE_AND_WORD	8-bit and 16-bit DMA channel.
	mDD_Width	Bitmask for the bits within DD_Flags that specify the channel width value.
Bus Mastering Flags
	fDD_NoBusMaster	No bus mastering.
	fDD_BusMaster	Bus mastering.
	mDD_BusMaster	Bitmask for the bits within DD_Flags that specify the bus mastering value.
DMA Type Flags
	fDD_TypeStandard	Standard DMA.
	fDD_TypeA	Type A DMA.
	fDD_TypeB	Type B DMA.
	fDD_TypeF	Type F DMA.
	mDD_Type	Bitmask for the bits within DD_Flags that specify the DMA type value.

DD_Alloc_Chan

For a resource list:

The DMA channel allocated to the device.

For a resource requirements list:

Not used.

Requirements

Requirement	Value
Header	cfgmgr32.h (include Cfgmgr32.h)

See also

DMA_RANGE

DMA_RESOURCE