Comment 15 for bug 185634

No something is still broken. I don't know that it is the kernel's fault though. Once you get it all working, you have to load the firmware manually after each reboot. (It worked through a reboot once for me, but since then I had to reload firmware.) It may be a problem with the udev rule in the firmware tools package, or the timing of loading the firmware vs. loading uvcvideo. All I know is that after bootup, you load the firmware, then everything works.

The command is something like:
sudo ./ift-load -f /lib/firmware/isight.fw -b 005 -d 003
being sure to specify the bus and device IDs correctly (found via lsusb).

Oh, the usbfs needs to be mounted as instructed above for this too work too.