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Date: Mon, 1 Jul 2002 12:19:52 -0700 (PDT)
From: Andre Hedrick <andre@linux-ide.org>
To: Martin Schwidefsky <schwidefsky@de.ibm.com>
cc: linux-kernel@vger.kernel.org
Subject: Re: hd_geometry question.
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Martin,

Are you looking at how the IDEMA proposal will be addressed in Linux ?
This beign 4096byte physical with 512byte logical and failure to do a full
8 sector logical write wil cause a read-write-modify to the physical.

Cheers,

On Mon, 1 Jul 2002, Martin Schwidefsky wrote:

> Hi,
> I have a question about the start field in the hd_geometry structure. We used
> 
> 	geo->start = device->major_info->gendisk.part[MINOR(kdev)].start_sect
> 		>> device->sizes.s2b_shift;
> 
> in the old dasd driver but now we use
> 
> 	geo.start = get_start_sect(kdev);
> 
> to set the start field. One variant is wrong because the start sector differ if
> the block size is not 512 byte. The first variant calculates the start sector
> based on physical blocks (e.g. with 4096 bytes instead of 512 bytes). The
> second variant calulcates a "soft" start sector based on logical 512 byte
> blocks. Whats correct, first or second variant ?? I tend to favor the first
> variant because struct hd_geometry describes the physical geometry
> (number of heads, sectors, cylinders and start sector) but I am not 100%
> sure about it.
> 
> blue skies,
>   Martin.
> 
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Andre Hedrick
LAD Storage Consulting Group

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