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
| Requirement | Value |
|---|---|
| Minimum supported client | 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(wdm) |