Quoting Ashok Raj <ashokr2@attbi.com>:

> Is anyone aware of usb drivers for the XIRCOM usb->serial adapters...

You mean one of those?

USB Xircom / Entregra Single Port Serial Driver
CONFIG_USB_SERIAL_XIRCOM
  Say Y here if you want to use a Xircom or Entregra single port USB to
  serial converter device.  This driver makes use of firmware
  developed from scratch by Brian Warner.

  This code is also available as a module ( = code which can be
  inserted in and removed from the running kernel whenever you want).
  The module will be called keyspan_pda.o. If you want to compile it
  as a module, say M here and read <file:Documentation/modules.txt>.

Dmitri