On 15 Jan 1998, Charles M. Hannum wrote:

: > Wait. Why are we going to screw over users?
: 
: Dude, have you actually been reading what I wrote?  Pretend I'm a
: user.  I install a snapshot, or I rebuild everything and install it.
: I run MAKEDEV to add a new disk and newfs(8) it.  Oops; I trashed the
: wrong disk because I didn't reinstall MAKEDEV.

Um, you never rebuilt with 32 bit nodes, so you're still using 16 bit nodes.
These are translated with the compatibility code.  `Where's the breakage?'

As long as you use 16 bit nodes with the compatibility, you never lose a
thing, and can fall back anytime you want to.  It's only new devices without
16 bit eqivalents, or devices that use additional bits not originally used
(and not at the default of zero), that break.  And you still have to create
those nodes.

There is no breakage by having a minor number translated at vnode creation
time, and just used as a 32 bit node as-is.  And there's also zero
renumber handling required by the devices--they _are_ renumbered, but you
don't see it because you're using the same nodes you've used all along.
(With a split minor you have to selectively renumber 16 bit devices to 32
bit devices.)

As I said, I'm on a kernel right now with 16 bit device nodes and 32 bit
internal representation.  It didn't break.

: > The thing I don't like about the split-minor proposal is that it's bending
: > over backwards for compatability. Since we DO have a smooth upgrade path
: > w/o this trick, I'd rather we make a clean break with the past.
: 
: `Bending over backwards'? 

Yes, becuase it's unnecessary.  *16*bit*device*nodes*work*, and if you want
the ability to fall back you'll be using 16 bit nodes anyway, so what
breaks?

: Worrying about what the
: numbers look like in hex, when there are more serious factors at hand,
: is just plain silly.

I only made this point because it gives a clear advantage of contiguous vs.
split minor numbers.  There's no win with a split minor.

=====
===== Todd Vierling (Personal tv@pobox.com) =====
== "There's a myth that there is a scarcity of justice to go around, so
== that if we extend justice to 'those people,' it will somehow erode the
== quality of justice everyone else receives."  -- Maria Price