DMA (WDM Interface)

NTDEV
1

Hi,
I am developing a driver on ix86 for a bus master PCI device having 4
blocks capable of transferring data to and from PC independently. I
wanted to use multiple channels of the DMAC( IP_9007)
simultaneously(i.e. in alternate time interval) so that I can get better
performance as a whole. How shall I use WDM interface to achieve that?

  1. Should I call IoGetDmaAdapter once for each block? Otherwise, maximum

number of usable Map registers will be very limited.

  1. While programming DMAC, I need to place 32 bit source and destination

addreesses in registers. I guess, I have to extract address in PC
from the return
value of MapTransfer call which is a PHYSICAL_ADDRESS structure.
How
should I extract it? Is it that, I need to assign the Lowpart field
of the structure
to the register?

Regards,
Girish

2

> 1. Should I call IoGetDmaAdapter once for each block? Otherwise, maximum

number of usable Map registers will be very limited.

No, call IoGetDmaAdapter once per device, and request unlimited number of map registers - (ULONG)(-1).

Max