ADDRESS_AND_SIZE_TO_SPAN_PAGES macro (wdm.h)

The ADDRESS_AND_SIZE_TO_SPAN_PAGES macro returns the number of pages spanned by the virtual range defined by a virtual address and the size in bytes of a transfer request.

Syntax

void ADDRESS_AND_SIZE_TO_SPAN_PAGES(
  [in]  Va,
  [in]  Size
);

Parameters

[in] Va

Pointer to the virtual address that is the base of the range.

[in] Size

Specifies the size in bytes of the transfer request.

Return value

None

Remarks

ADDRESS_AND_SIZE_TO_SPAN_PAGES returns the number of pages spanned by the virtual range starting at Va.

Drivers that make DMA transfers call ADDRESS_AND_SIZE_TO_SPAN_PAGES to determine whether a transfer request must be split into a sequence of device DMA operations.

A driver can use the system-defined constant PAGE_SIZE to determine whether the number of bytes to be transferred is less than the virtual memory page size of the current platform.

Callers of ADDRESS_AND_SIZE_TO_SPAN_PAGES can be running at any IRQL. The caller must ensure that the specified parameters do not cause memory overflow.

Requirements