Re: [PATCH] print_dev_t for 2.6.0-test1-mm

From: Andries Brouwer <aebr@win.tue.nl>
To: Andrew Morton <akpm@osdl.org>
Cc: Joel Becker <Joel.Becker@oracle.com>,
	zippel@linux-m68k.org, aebr@win.tue.nl, greg@kroah.com,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] print_dev_t for 2.6.0-test1-mm
Date: Thu, 17 Jul 2003 13:46:47 +0200	[thread overview]
Message-ID: <20030717134647.A2347@pclin040.win.tue.nl> (raw)
In-Reply-To: <20030717022444.19c204ef.akpm@osdl.org>; from akpm@osdl.org on Thu, Jul 17, 2003 at 02:24:44AM -0700

On Thu, Jul 17, 2003 at 02:24:44AM -0700, Andrew Morton wrote:

> And surely the task of mangling whatever comes off the wire into a dev_t for
> init_special_inode() should be private to the Linux NFS client?
> 
> Still wondering why we need to support a 16:16 encoding in [k]dev_t.

I think I answered this already in earlier posts today. Again:
(i) We need support for 16/32/64-bit dev_t.
(ii) User space (glibc) has 64-bit dev_t.
(iii) The split into major/minor is hardwired in <sys/sysmacros.h>,
independent of filesystem. Thus, we must define major(),minor(),makedev().
(iv) For Linux the device number is a cookie - major and minor do not
really have a significance - we just select a driver given a *dev_t
interval. That means that there are no reasons for inventing more
complicated setups like 12:20.

And since you add "[k]": a kdev_t is internal to the kernel,
we do whatever we want. I wanted a pointer (say, to a struct gendisk or so),
but these days it seems we are heading for an arithmetic type, with 32:32.

Andries