USB Host software

Hi
We're developing a Digital Video Surveillance system using DM642. We're
interfacing external PCI enabled USB controller (from Philips ISP1561)
to our board containing DM642. The application is to store the recorded
video to USB Flash Drive (The USB Key). The RTOS used is DSP/BIOS from
TI.

I'd like to know to develop this what all things that we need to take
care. We're getting the following from philips.
1. Host Controller Driver for ISP1561 on standard OS
2. Should we write USB Host stack and USB Driver or USBD (As per USB2.0
specs) on DSP/BIOS?
3. Are the mass storage class driver available as open source?


Let me know. Any help would be highly appreciated.

Thanx in advance
Gautham