Mark Kettenis <mark.kettenis@xs4all.nl> wrote:

> > That is my thought also.  If this is impossible to use without setting
> > an option, then noone will use it.  If noone is using it, then why have
> > the code at all?  I think we want it, because we know we need it (soon).
> 
> Actually xcall isn't an option; it is an attribute.  Drivers that need
> the functionality ask for it by adding it as a dependency.  It is no
> different than framebuffer drivers depending on rasops for example.

> So the question really is whether we intend to use this functionality
> in generic code or not.  For now all the places where we intend to use
> this are MD drivers.

That is surprising.

I was pretty sure the uses would either be in MD code only, or in
MI /sys/kern /sys/net*, and /sys/uvm

I would be very surprised to see it used in MI drivers.