From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S265931AbUHANNq (ORCPT ); Sun, 1 Aug 2004 09:13:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S265932AbUHANNp (ORCPT ); Sun, 1 Aug 2004 09:13:45 -0400 Received: from chaos.analogic.com ([204.178.40.224]:58757 "EHLO chaos.analogic.com") by vger.kernel.org with ESMTP id S265931AbUHANNn (ORCPT ); Sun, 1 Aug 2004 09:13:43 -0400 Date: Sun, 1 Aug 2004 09:10:23 -0400 (EDT) From: "Richard B. Johnson" X-X-Sender: root@chaos Reply-To: root@chaos.analogic.com To: "Thomas S. Iversen" cc: linux-kernel@vger.kernel.org Subject: Re: How to do IO across hardsector boundries In-Reply-To: <410C37B7.3010504@zensonic.dk> Message-ID: References: <410C37B7.3010504@zensonic.dk> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 1 Aug 2004, Thomas S. Iversen wrote: > Hi There > > As part of an assignment I am trying to port a piece of software from > FreeBSD to linux. Essentially this software (crypto) makes a virtual > blockdevice with "virtual" sectors on top. Under FreeBSD these virtual > sectors are just read/written using a simple command: > > buf=g_read(dev, offset, len) > error=g_write(dev,offset,buf,len) > > In linux however I have only seen the BIO layer which operates on IO on > hardsector boundaries. > > So my question really is, how do I go about updating for instance the > 512 bytes located for at byte 64 to 64+511 on the actual media without > getting in trouble regarding the data from offset 0-63 and 64+512->1023? > > Regards Thomas There are no hard-sector boundaries in Linux. The geometry of a drive is really ignored. It's just used to determine the size of a disk partition, etc. The stated Heads/cylinders/sectors is a throw-back to the old int 0x13, DOS days where stuff had to fit into registers for access. If your driver expects to write physical sectors, it's broken. Even physical sectors (on the media) don't really exist anymore. They are now "logical" sectors and they are never really accessed as a single unit (except in floppies). They are "extracted" from a sector-buffer that could contain nearly a whole track. Cheers, Dick Johnson Penguin : Linux version 2.4.26 on an i686 machine (5570.56 BogoMips). Note 96.31% of all statistics are fiction.