So to add such an "I am crap" flag my idea would be to add an 
.fb_handle_damage to struct fb_ops and then call that (if exists) 
whenever something was changed.

I was thinking much higher level - ie at the printk kind of level

My patch (for udlfb) follows as an reply to this message. If that patch 
is ok, it should be applied to smscufx too (I would make it). In regard 
to udl I don't know, I haven't had a deeper look at it nor used it up to 
now.

Looks pretty clean as a solution to me.