> > is it for (a few instances of) bounds_check_with_label?
> 
> Originally it's for drivers that allow raw access to disk (and memory)
> but don't have vnode/device references; if it fits for more stuff then
> yeah. For now it's just a place-holder (hence, no documentation update).

a place-holder?
do you mean you'll remove this "no vnode/device" case later?

YAMAMOTO Takashi