linux-kernel - Re: [PATCH] Ghost EDD devices in /sys again

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Message-ID: <48DF9EDA.1060809@zytor.com>
Date:	Sun, 28 Sep 2008 08:12:26 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Andrey Borzenkov <arvidjaar@...mail.ru>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH] Ghost EDD devices in /sys again

Andrey Borzenkov wrote:
> On Sunday 07 September 2008, H. Peter Anvin wrote:
>> I think this is closer to what we really want; after all, memory being written is the "first principles" test that applies here.
>>
> 
> OK I have been using this for some time. I do not actually insist on
> returning "failure" for zero signature; my main concern was duplicated
> signature resulted from not clearing read buffer. Still I assume that
> zero signature is the same as no signature; i.e. even if disk is physically
> present but zeroed out there is no point in presenting mbr_signature in
> sysfs either.
> 

Right, I think that's a much better patch.

The really Right Thing[TM] to do is probably to pre-clear the buffer and 
then look for the 0xaa55 signature at offset 510; it is required for 
sector 0 to be a valid MBR-format partition table and hence for the MBR 
*signature* to be valid.

I'll write that up tomorrow (I'm travelling today), or you can send me a 
patch.

	-hpa

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