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Date: Tue, 14 Jan 2003 11:48:58 +0000 (GMT)
From: Tigran Aivazian <tigran@veritas.com>
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To: Christoph Hellwig <hch@lst.de>
cc: Hugh Dickins <hugh@veritas.com>, <torvalds@transmeta.com>,
       <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] don't create regular files in devfs (fwd)
In-Reply-To: <20030114113135.A14279@lst.de>
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On Tue, 14 Jan 2003, Christoph Hellwig wrote:

> On Tue, Jan 14, 2003 at 09:34:52AM +0000, Tigran Aivazian wrote:
> > Hi Christoph,
> >
> > I don't know about mtrr (probably does it for the same reason) but the
> > reason why microcode driver uses a regular file is because it needs
> > something that only regular files can provide --- the file size.
> >
> > This is an easy external "signifier" as to whether a successfull microcode
> > update has occurred or not.
>
> It seems to work without that feature on systems that don't have devfs..

Of course it works without it. I never said it is a required feature, only
a very nice to have. Namely:

a) if devfs is available it provides a regular file whose size can be
examined by applications and content read/written without much "fuss". In
particular it is very convenient to say "vi microcode" and examine the
content directly. If it was a device node then this would have been
impossible.

b) if devfs is not available then a limited basic functionality is
provided --- i.e. just update the microcode on CPU(s) and write the log
messages in the kernel log.

Btw, having a size of mtrr is also useful for a similar reason.

Regards
Tigran

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