RE: VDMA & PCI

[ingvar.berg.swe3650@oasis.icl.co.uk]

Chris Malcheski wrote:
>
>Here's one I'll be NOBODY can answer, but I'll give it a shot ...
>
>what happens to VDMA (virtual DMA) services on a bus mastering transfer?  My
>understanding was that the VDMA internals intercepted I/O to the DMA 
controller
>and converted logical addresses to physical.  On PCI bus mastering, 
there is no
>effective I/O to trap to the DMA controller.  I would imagine this 
would render
>VDMA useless in these cases.
>
>Anybody have any insight?

Sounds like this refers to an x86 PC system. If thats the case, then 
the answer is that the problem isn't unique to PCI bus mastering, but 
exists with any type of bus master HW (AT, EISA,...). The solution is 
to use OS specific services to translate linear address to physical and 
to lock buffer areas during transfer. From a BIOS, you can use Int 4B, 
function 81H and from drivers, well you have to consult the DDK documentation.

rgds,
NOBODY 

|i