lfocus doesn't force a focus it only applies it through v4l2-ctl, but for the stop autofocus function it uses the stop-focus.py script which intercepts a "True" half-press button signal and returns "False" instead. as for the mechanical noise I think it is caused by remember led state function which is being sent by lfocus after pressing on the camera button [edit] and tries to turn on the led while the camera is in stand by state which causes the camera to turn on and off hence the lense going into action position and idle position. I think I'll apply a fix for this plus keep the remember led state button turned off and the user turns it on only when he has to take a video since keeping led on after taking a picture doesn't make any sense.