The other chunk of info, "In use by," really is a free-form bit of info. 
   i.e. a string. :-) It's a property of the device, and so you can probably 
   guess what I'm going to suggest. :-)
   
   Since we're making use of property lists, let's add property lists to 
   devices and add an ioctl that sets the, "In use by," property. Also add a 
   "Get in use by" ioctl, and we're set for what you wanted to do.
   
   I realize this is a bit of feature creep, but I think it's a way to do 
   what you want in a scalable method. And scaling was your (valid) concern 
   with just using VOP_OPEN().


hmmm, my initial reaction was "great" but we only have one device
yet potentially many many partitions..  we need to solve that
conflict i believe.


.mrg.