As you can see on that link, there are many lens adapters for the Sony E-Mount used by the Nex series. We'll cover specifically the Canon ones.
The Canon FD Adapter
The adapter is of very good build quality, note that COMA doesn't simply resell cheap chinese stuff, they manufacture the adapters in Italy in their lab, and it shows!
The iris control is the one on your FD Lens! The adapter simply enables a mechanical switch that unlocks the iris on the lens to work normally as it would on a Canon FD camera. Except the "A" automatic aperture position doesn't work, you will have to always adjust the aperture manually. However, I haven't found this to be a problem at all, in fact, since there's no autofocus anyway, I prefer using FD lenses with the Sony Nex-7, because setting the aperture on an EF (Eos) lens with the adapter is quite cumbersome and have side effects, like strong vignetting. See my post on the EF Adapter here for more informations.