Various Usb Camera Chips Support (Sunplus, Etoms, Conexant, Z-star ~ Vimicro, Sonix, Zoran, IcMedia ~ TransVision based): Spca5xx Linux Kernel module. At the moment, manufacturers of usb bridge and camera sensor did not help them.
The driver is the result of reverse engineering the protocols and functionality provided by these chips(Sunplus, Z-star/Vimicro, Sonix, Etoms, Conexant, IcMedia/TransVision, Pixart).