From: Andries.Brouwer@cwi.nl
Date: Thu, 20 Mar 2003 23:24:33 +0100 (MET)
Message-Id: <UTC200303202224.h2KMOXC01107.aeb@smtp.cwi.nl>
To: Andries.Brouwer@cwi.nl, zippel@linux-m68k.org
Subject: Re: major/minor split
Cc: Joel.Becker@oracle.com, akpm@digeo.com, andrey@eccentric.mae.cornell.edu,
       linux-kernel@vger.kernel.org, torvalds@transmeta.com
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1024
Lines: 28

> There is a point I'd like to get clear: where should the
> 16bit<->32bit dev_t conversion happen?

I am not sure I understand the question, but if I do
the answer is "nowhere", there is no conversion
(other than the lengthening that happens when one
casts an unsigned short to an unsigned int).

For dev_t (8,1) is 0x00000801, but (8,256) is 0x00080100.
(In case of a 16+16 split. Not that I advocate that,
it is just easy talking.)

For kdev_t (8,1) is 0x00080001 and (8,256) is 0x00080100.
So kdev_t allows simple fast composition and decomposition,
but is restricted to the kernel.
While dev_t requires a conditional, since it has to remain
compatible with the old 8+8 userspace.

> how can software create nodes for a specific device?

You do not mean using mknod?

Andries
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