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) |