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Subject: Re: [PATCH] 2.5 ide 48-bit usage
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Linus Torvalds <torvalds@transmeta.com>
Cc: Jens Axboe <axboe@suse.de>,
       Bartlomiej Zolnierkiewicz <B.Zolnierkiewicz@elka.pw.edu.pl>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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Date: 07 May 2003 19:29:08 +0100
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On Mer, 2003-05-07 at 17:28, Linus Torvalds wrote:
> At least if I read the patch correctly, theer's no way for upper layers to
> say "I want 48-bit addressing" - it's just turned on automatically for
> high sectors (or big transfers).

You read it incorrectly. The lower layers don't know about the issue at
all. The disk layer does mapping (conceptually like READ6/READ10/READ16
in SCSI) 

Raw I/O and other drivers can still issue CHS LBA28 and LBA48 taskfiles.

> Well, you can mark the drive itself as wanting 48-bit transfers, but you 
> can't do it on a per-request basis.

Its per request at the low level.