PGET_DMA_ALIGNMENT callback function (wdm.h)

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

Syntax

PGET_DMA_ALIGNMENT PgetDmaAlignment;

ULONG PgetDmaAlignment(
  [in] PDMA_ADAPTER DmaAdapter
)
{...}

Parameters

[in] 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

See also

DEVICE_OBJECT

DMA_ADAPTER

DMA_OPERATIONS

IoGetDmaAdapter