VDMAD_Request

include vdmad.inc

mov esi, OFFSET32 DMA_Region
mov ecx, RegionSize
VxDcall VDMAD_Request_Buffer
jc ErrorHandler

Reserves the DMA buffer for a DMA transfer. Uses EAX, EBX, ESI, flags

Clears the carry flag if the service is successful. The EBX register contains the buffer identifier, and the EDX register contains the physical address of the buffer.
Otherwise, the carry flag is set and the AL register contains one of the following error values:

5	DMA_Buffer_Too_Small: Region request is too large for buffer.
6	DMA_Buffer_In_Use: Buffer already in use.

DMA_Region

Address of the actual DMA region.

RegionSize

Size of the DMA region in bytes.