Note  The NetDMA interface is not supported in Windows 8 and later.
The NET_DMA_CHANNEL_PARAMETERS structure specifies the configuration parameters that a DMA provider driver should use to configure a DMA channel.


  USHORT           Revision;
  USHORT           Size;
  ULONG            Flags;
  PVOID            CompletionVirtualAddress;
  PHYSICAL_ADDRESS CompletionPhysicalAddress;
  ULONG            ProcessorAffinityMask;
  ULONG            ChannelPriority;
  ULONG            CpuNumber;
  GROUP_AFFINITY   ProcessorAffinityMaskEx;



The revision number of this structure.

For Windows 7 and Windows Server 2008 R2 and later, set this member to NET_DMA_CHANNEL_PARAMETERS_REVISION_2.

For Windows Vista and Windows Server 2008, set this member to NET_DMA_CHANNEL_PARAMETERS_REVISION_1.


The size, in bytes, of this structure. Set this member to sizeof(NET_DMA_CHANNEL_PARAMETERS).


A set of bits for flags that define DMA channel attributes. Set this member to zero. There are currently no flags defined.


The virtual address of the memory location where the DMA engine can write the DMA transfer completion status. This virtual address is associated with the physical address that is specified in the
CompletionPhysicalAddress member.


The physical address of the memory location where the DMA engine can write the DMA transfer completion status. If the NET_DMA_STATUS_UPDATE_ON_COMPLETION flag is not set in the ControlFlags member of the NET_DMA_DESCRIPTOR structure, CompletionPhysicalAddress is not used. Otherwise, the completion status value at the specified address is a 64-bit wide combination of the physical address of the most recent DMA descriptor that the DMA engine processed and additional status information.

The physical address of the DMA descriptor must be aligned to 64-bit boundaries. Therefore, the lower six bits of the address are available for other information. The DMA engine combines the following status values with the descriptor address by using a bitwise OR operation:

Value Meaning
The DMA transfer for the most recent DMA descriptor completed without errors, and the DMA engine has more descriptors to process.
The DMA transfer for the last DMA descriptor in the linked list of descriptors completed without errors.
The DMA transfer for the most recent DMA descriptor completed without errors, and DMA transfers are suspended because the NetDMA interface called the ProviderSuspendDma function. The DMA engine will restart the transfer after the NetDMA interface calls the ProviderResumeDma function.
The DMA transfer for the most recent DMA transfer was aborted because of errors or because the NetDMA interface called the ProviderAbortDma function.
The DMA transfer for the first descriptor has not completed and the completed descriptor address is not valid.


A bitmap that indicates CPUs that are available for use with this DMA channel. Each bit in ProcessorAffinityMask identifies a CPU. For example, setting bit 0 indicates CPU 0 can be used, setting bit 1 indicates CPU 1 can be used, and so on.


A DMA channel priority value that represents the priority for the DMA channel relative to other DMA channels on the same DMA engine. A lower priority setting indicates a lower priority DMA channel. If this value indicates a higher priority than the hardware supports, the highest value that the hardware supports should be used. The Windows Vista NetDMA interface sets this member to zero.


The CPU number that is associated with the DMA channel. The DMA provider driver sets the value before it returns from the
ProviderAllocateDmaChannel function. The DMA engine uses this CPU for interrupt DPCs that are associated with the DMA channel. If the DMA engine and computer configuration support MSI-X, the interrupt should also be associated with the indicated CPU number, unless there was no MSI-X interrupt available for the indicated CPU.


The group number and a bitmap of the CPUs that this DMA channel could be associated with.


Before using a DMA channel, the NetDMA interface calls the
ProviderAllocateDmaChannel function of the DMA provider driver to allocate and initialize the DMA channel.

The NetDMA interface supplies a NET_DMA_CHANNEL_PARAMETERS structure at the ChannelParameters parameter of ProviderAllocateDmaChannel.


Minimum supported client Windows Vista
Minimum supported server Windows Server 2008
Header netdma.h (include Netdma.h)

See Also