PGET_DMA_ALIGNMENT callback function

The GetDmaAlignment routine returns the alignment requirements of the DMA system.

Syntax

PGET_DMA_ALIGNMENT PgetDmaAlignment;

ULONG PgetDmaAlignment(
  PDMA_ADAPTER DmaAdapter
)
{...}

Parameters

DmaAdapter

A pointer to the DMA_ADAPTER structure returned by IoGetDmaAdapter that represents the bus-master adapter or DMA controller.

Return Value

GetDmaAlignment returns the alignment requirements, in bytes, of the DMA system. The starting address and length of DMA buffers must be a multiple of this value.

Remarks

GetDmaAlignment is not a system routine that can be called directly by name. This routine is callable only by pointer from the address returned in a DMA_OPERATIONS structure. Drivers obtain the address of this routine by calling IoGetDmaAdapter.

A driver can call this routine to determine alignment requirements for DMA buffers it allocates. The returned value should be used to set the AlignmentRequirement field in the device object. A driver may need to increase this value because of additional hardware device restrictions. For more information, see Initializing a Device Object.

Requirements

   
Windows version Available starting with Windows 2000.
Target Platform Desktop
Header wdm.h (include Wdm.h, Ntddk.h, Ntifs.h)
IRQL PASSIVE_LEVEL
DDI compliance rules IrqlDispatch

See Also

DEVICE_OBJECT

DMA_ADAPTER

DMA_OPERATIONS

IoGetDmaAdapter