Int 4B Fn 8103  - Virtual Dma Specification - Lock Dma Region              [d]

   AX = 8103h
   DX = flags (see #2891)
   ES:DI -> DMA descriptor structure (see #2892,#2893,#2894)

Return: CF clear if successful
       DDS physical address field filled in
       DDS buffer ID field filled (0000h if no buffer allocated)
   CF set on error
       AL = error code (see #2889)
       DDS region size field filled wth maximum contiguous length in bytes
BUGS:  Windows 3.0 does not correctly support automatic remapping or copying
     in enhanced mode
   Windows 3.0 in enhanced mode does not return a correct code on error

See Also: AX=8104h,AX=8105h

Bitfields for VDS flags:
Bit(s) Description (Table 2891)
 0 reserved (zero)
 1 data should be copied into buffer (ignored if 2 set)
 2 buffer should not be allocated if region noncontiguous or crosses
     physical alignment boundary specified by 4-5
 3 don't attempt automatic remap
 4 region must not cross 64K physical alignment boundary
 5 region must not cross 128K physical alignment boundary
 6-15  reserved (zero)

Format of DMA descriptor structure (DDS):
Offset Size    Description (Table 2892)
 00h   DWORD   region size
 04h   DWORD   offset
 08h   WORD    segment/selector
 0Ah   WORD    buffer ID
 0Ch   DWORD   physical address

Format of Extended DMA descriptor structure (EDDS):
Offset Size    Description (Table 2893)
 00h   DWORD   region size
 04h   DWORD   offset
 08h   WORD    segment/selector
 0Ah   WORD    reserved
 0Ch   WORD    number available
 0Eh   WORD    number used
 10h   DWORD   region 0 physical address
 14h   DWORD   region 0 size in bytes
 18h   DWORD   region 1 physical address
 1Ch   DWORD   region 1 size in bytes
   ...

Format of Extended DMA descriptor structure (EDDS) with page table entries:
Offset Size    Description (Table 2894)
 00h   DWORD   region size
 04h   DWORD   offset
 08h   WORD    segment/selector
 0Ah   WORD    reserved
 0Ch   WORD    number available
 0Eh   WORD    number used
 10h   DWORD   page table entry 0 (same as 80386 page table entry)
 14h   DWORD   page table entry 1
   ...

Note:  bits 1-11 of the page table entries should be zero; bit 0 set if page
     is present and locked