How to use the DMA Engine in FreeBSD?

[Rajesh Kumar]

Hi,

Is there any good documentation available to understand the existing
support, API's and how-to use the DMA Engine in FreeBSD?

I am trying to write a test driver which will use DMA Engine to do the data
transfer (rather than plain memcpy which involves cpu).  Can anyone point
to any driver implementation which has similar functions implemented?  I
see references to SYS_RES_DRQ to allocate DMA channels and play around. But
that seems to be specific to ISA. Can it be used for PCI drivers as well?

Thanks,
Rajesh.