Works seamlessly on this way, but I do not know how to throw out DEF (some_flag_for_af_scan, 0x000281d4) from stubs_entry.S 
You'd have to DEF it again in stubs_min.S (but you'd need to come up with a RAM location that doesn't change its content).
However, I have a better idea (in development).
Movie AF scan (the CHDK feature) was invented for cameras that have no autofocus during video recording. Recently, more and more models (even my low end ixus150) feature continuous auto-focus during recording. The problem with these is the opposite of the old problem: they often don't allow locking the focus during recording.
What I'm proposing is:
Keeping the AF key entry in the video menu. The button chosen there would lock the focus on first press, unlock on second press, and so on.
Additionally, I'd offer two alternative ways for locking/unlocking focus:
- One based on DoAFLock/UnlockAF. DoAFLock always does an AF scan, then locks the focus.
- Another, based on the 'MovieAF.Suspend' and 'MovieAF.Resume' event procedures. These just freeze/unfreeze the AF process, without doing an AF scan.
Patch will follow shortly.
