In some mail I received from Todd Vierling, sie wrote
> 
> : Yes.  I think it's reasonable to do this the way BSDI did, i.e. use a
> : dv_unit and dv_subunit.
> 
> Why, really?  I can see different numbers of bits needed for different
> things in various devices in the future (perhaps 16/4/4 here, but maybe
> 8/12/4 elsewhere?), and I'd think that just a binary encoded number is
> adequate to hold everything.  The only reason I'd see need for three pieces
> is if we actually had two layers of abstraction in the devsw--that is, each
> entry is a pointer to a table of devsw entry _arrays_.  Otherwise, we only
> need one value for minor and splitting it could make it numerically
> confusing.

One thing I've always wondered is how lun's get allocated for SCSI devices.
Say I have a multi-CD-ROM device, which holds 6 CD'ssome of which are UFS
and have multiple partitions and others are iso9660.  Shouldn't they also
be in the dev_t somewhere ?

Darren