Subject: Re: Ideas about the cdevsw/bdevsw structs.
To: Hubert Feyrer <>
From: Bill Studenmund <>
List: tech-kern
Date: 05/17/1999 13:13:20
On Sun, 16 May 1999, Hubert Feyrer wrote:

> On Sun, 16 May 1999, Anders Magnusson wrote:
> > 	All major numbers are kept in an include file; machine/conf.h
> > 	for example. They are syntactically:
> Would it be possinle to have the major numbers uniform across all
> platforms? Would make it possible to share device nodes via NFS, for
> whatever good that may be. :>

I don't think we want to change _existing_ device numbers, for a couple of
reasons. 1) Doing so can REALLY mess up a system. All /dev backups become
invalid/dangerous, etc. 2) We often have existing major numbers aligned
with O/S's we emulate.

One of the things we were talking about doing with the move to using the
full 32 bits of dev_t's was moving to having more bits per unit. I think
64 was the decided number, though not much code has been written.

The main result though is that different device numbers will need
different unit/partition division. The most backwards compatable thing to
do is leave the old major numbers as-is, and play with new major numbers.
When we start playing w/ new major numbers, I vote we also make the device
numbers constant across ports.

Take care,