Subject: Re: devfs (was Re: Not updating device file inode change times)
To: John F. Woods <>
From: Martin Husemann <>
List: tech-kern
Date: 09/05/1998 18:22:07
John F. Woods wrote:

> There are, I think, two basic problems that a devfs filesystem can solve
> for you:  (1) having to remember to create device nodes before you can use
> brand-new hardware (and having to have an up-to-date MAKEDEV script before
> doing so), and (2) running with a root filesystem which either has no support
> for device nodes (MSDOS) or where said support is tricky (NFS where you'd like
> to share a root filesystem between computers with different /dev layouts).

There is an even more important problem solved by devfs (or, at least,
easily solveable by a descent devfs implementation): the strugle for
major number consistency.

For a third party driver writer this is a realy urgent problem. With devfs
you simply add a static "struct devfs_token" to your code, get a major assigned
and appropriate (consistent) entries in /dev via internal devfs magic. No
need to have an installation script edit /usr/src/sys/arch/*/conf.c for a
growing number of architectures and have same script (or the user) fiddle
with /dev entries.