The issue is the distance from the rear of a FL or FD lens to the focal plane. Its 1mm less than a EF lens, so there is no room for a adapter.
You can adapt it to a camera that as a shorter lens to film / sensor like a micro 4/3 or Nex, but trying to adapt it to a Canon difital camera is a exercise in frustration.
Ed Mika makes adapters for the high end EF lenses and somehow finagles enough room to get infinity focus without modifying the lens. The adapters are hand made, and expensive, so they are only worthwhile on expensive glass.
