Offloading to hardware

Hi!

I'm in the middle of building a PCI-card that is capable of 
encryption/decryption (using a Virtex-2 FPGA), and maybe a bit later it'll 
get ethernet abilities as well (Intel Dual Gbps chip under consideration).

Since several people on this list has handson experience with writing
tools/drivers for Linux for such cards, I thought I'd ask for some advice:
* How's a smart way to design such a card?  (ie. how much should the
  card be able to do on it's own?)
* Looking at the current TODO-list, Hardware-support is a bit down the
  road, is the TODO-list updated (I took it from the 2.5.59 kernel). If
  yes, where's a good place to start if I want such a thing now?
* Any other advice is also welcommed :)


When it's "done" the plan is to opensource the hardware design, as well
as the drivers written for it, and all the tools written for it. The
goal behind this is to create a relatively cheap PCI-card that can
do better as a VPN-card than most "black-boxes" today; Cisco sells 
som VPN-boxes for a huge load of USDs, for instance.

-- 
Thomas