From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sat, 18 Jan 2003 10:54:44 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sat, 18 Jan 2003 10:54:43 -0500 Received: from keetweej.xs4all.nl ([213.84.46.114]:384 "EHLO muur.intranet.vanheusden.com") by vger.kernel.org with ESMTP id ; Sat, 18 Jan 2003 10:54:43 -0500 From: "Folkert van Heusden" To: "'John Bradford'" Cc: , Subject: RE: reading from devices in RAW mode Date: Sat, 18 Jan 2003 17:03:39 +0100 Message-ID: <003501c2bf0b$2ae93ff0$3640a8c0@boemboem> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook CWS, Build 9.0.2416 (9.0.2910.0) In-Reply-To: <200301181430.h0IEUK6D001055@darkstar.example.net> Importance: Normal X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > > Is it such a newby question? Your suggestion of using dd is totally NOT > > what I meant: I want to read from devices with the devices ignoring their > > CRC-checks and such. Like what the CDROMREADRAW ioctl does for CD-ROMs. > CD-ROMs, floppy disks, and hard disks work in completely different > ways: > All modern forms of storage use powerful error correction below the > sector level. Floppies are the exception here, they typically use MFM > encoding, which is relatively straightforward. > Audio Compact discs use powerful error correction anyway, but CD-ROMs > use some of the capacity which was previously used for audio data for > a second level of error correction, so there are two sector sizes, > (RAW, and COOKED). Reading RAW sectors, does not come close to > allowing you to read individual pits and flats on the disc, it just > lets you bypass the top level of error correction. The data is still > being error corrected by lower layers. oh, ok. But I will still get more data back then with reading through the regular, say, /dev/hdc-device wouldn't I? As far as I know, read will only give you data when no I/O error occured. > There is no floppy or hard disk equivillent to reading raw sectors > from CD-ROMs. Really? Are you really sure about that? Back in the old days, when I did assembly on my Atari ST, I would just say to the controller "gimme this and that track, in RAW" and it would do so. I thought that I could do that at least for floppy, not sure about harddisk (RLL through ACSI interface).