http://en.wikipedia.org/wiki/Flange_focal_distance
not going to happen. Canon lenses need to sit .5mm closer to the sensor to achieve infinity focus. Adapters are at least 2-3mm thick, so that is out. Additionally, you would need a special (aka expensive) electronic one to control the aperture (unless it has a ring, which very few ef lenses do). What lens are you trying to adapt? There may be a version that comes in the sony A mount.