“Ta H.” wrote in message news:xxxxx@ntdev…
>
> Hmm, now I feel it has nothing to do with the numbers of the DMA adapters
> but with the numbers of the map registers. As Max suggested earlier, I
> should ask for unlimited map registers. How does Windows implement the
>
I’m sorry to disagree with Max, but there’s no way to ask for any specific
number of map registers – except implicitly via the max size of transfer.
I realize that the DDK docs say that the NumberOfMapRegisters parameter can
be set to something on input. But I’ve been through this many times – it’s
never used.
This has been a fallacy since as far back as I can remember - NT V3.1 I
believe - and somehow it has crept into the DDK documentation. Yes, I know.
I should file a bug report.
Try it for yourself. Put a zero into this parameter on input, and them put
0xFFFFFFF or 0xFFFF or 0xdeadbeef or whatever value you most love into this
parameter on input. See if you get a different number back after calling
NumberOfMapRegisters.
I bet it doesn’t matter…
Peter