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From: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
To: Jeff Garzik <jgarzik@pobox.com>, Tejun Heo <htejun@gmail.com>
Cc: linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: ata_tf_read_block() question
Date: Sat, 15 Aug 2009 22:48:43 +0900 (JST)	[thread overview]
Message-ID: <20090815.224843.240484147.anemo@mba.ocn.ne.jp> (raw)

I have a question on CHS calculation in ata_tf_read_block().

The calculation in ata_tf_read_block() is:
	block = (cyl * dev->heads + head) * dev->sectors + sect;

but ata_build_rw_tf() does:
	track = (u32)block / dev->sectors;
	cyl   = track / dev->heads;
	head  = track % dev->heads;
	sect  = (u32)block % dev->sectors + 1;

It seems inconsistent.  The correct calculation is:
	block = (cyl * dev->heads + head) * dev->sectors + sect - 1;
isn't it?

I don't have any real problem.  Just noticed by code reading.
---
Atsushi Nemoto

             reply	other threads:[~2009-08-15 13:48 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-08-15 13:48 Atsushi Nemoto [this message]
2009-08-16  2:15 ` Tejun Heo
2009-08-16  9:33   ` Atsushi Nemoto
2009-08-16 12:21     ` [PATCH #upstream-fixes] libata: fix off-by-one error in ata_tf_read_block() Tejun Heo
2009-09-09  1:19       ` Jeff Garzik

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