Reverse engineer PCI drivers for device with none

Is it possible to reverse engineer PCI drivers for a device which has none? The device in question was a PCI ESCON card that allowed you to connect a mainframe ESCON channel to a specialty unix computer. As far as I know, this device never had any drivers released publicly, but still uses a standard PCI bus. Would it be possible to put together drivers without having an existing set to reverse engineer? Any info would be appreciated.