1. I open /dev/mem and get a file descriptor
2. I use mmap to reserve some physical addresses for my buffers in
user space.
3. I give that address to the FPGA for DMA use.
4. When I get the FPGA interrupt, I invalidate the data cache and
write the data to disk
=20
Does that sound like it would work?  Would the address I receive
from mmap() and pass to the FPGA be the actual physical address, or
would I need to send the physical address to the FPGA and use the
mmap() address to access and write to disk?

One more question about this approach: does the mmap() call prevent the ker=
nel from using this memory for other purposes?  Will the kernel be able to =
"move" this memory elsewhere?  I guess what I am asking is if this memory i=
s locked for all other purposes?