From owner-freebsd-scsi@FreeBSD.ORG Tue Dec 10 23:58:28 2013 Return-Path: Delivered-To: freebsd-scsi@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 7C865750 for ; Tue, 10 Dec 2013 23:58:28 +0000 (UTC) Received: from i3mail.icecube.wisc.edu (i3mail.icecube.wisc.edu [128.104.255.23]) by mx1.freebsd.org (Postfix) with ESMTP id 4C3091D26 for ; Tue, 10 Dec 2013 23:58:28 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by i3mail.icecube.wisc.edu (Postfix) with ESMTP id CF2B138249; Tue, 10 Dec 2013 17:58:27 -0600 (CST) X-Virus-Scanned: amavisd-new at icecube.wisc.edu Received: from i3mail.icecube.wisc.edu ([127.0.0.1]) by localhost (i3mail.icecube.wisc.edu [127.0.0.1]) (amavisd-new, port 10030) with ESMTP id JIBEeEnzReWK; Tue, 10 Dec 2013 17:58:27 -0600 (CST) Received: from terminus.icecube.wisc.edu (terminus.icecube.wisc.edu [172.16.223.97]) by i3mail.icecube.wisc.edu (Postfix) with ESMTPSA id BACF438246; Tue, 10 Dec 2013 17:58:27 -0600 (CST) Message-ID: <52A7AAA3.5050404@freebsd.org> Date: Tue, 10 Dec 2013 17:58:27 -0600 From: Nathan Whitehorn User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:24.0) Gecko/20100101 Thunderbird/24.1.0 MIME-Version: 1.0 To: dgilbert@interlog.com, FreeBSD SCSI Subject: Re: [CAM] Widening lun_id_t to 64-bits References: <52A7830B.2090803@freebsd.org> <52A7A69E.3030703@interlog.com> <52A7AA76.3060208@interlog.com> In-Reply-To: <52A7AA76.3060208@interlog.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Hannes Reinecke X-BeenThere: freebsd-scsi@freebsd.org X-Mailman-Version: 2.1.17 Precedence: list List-Id: SCSI subsystem List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 10 Dec 2013 23:58:28 -0000 On 12/10/13 17:57, Douglas Gilbert wrote: > On 13-12-11 12:41 AM, Douglas Gilbert wrote: >> On 13-12-10 10:09 PM, Nathan Whitehorn wrote: >>> Modern SCSI hardware often uses 64-bit logical units (LUNs). The >>> patch found at >>> http://people.freebsd.org/~nwhitehorn/lun64.diff widens the type of >>> lun_id_t to >>> 64 bits, bumps CAM_VERSION, and begins exposing these to drivers >>> that are marked >>> as supporting extended LUNs. No behavior is changed except that >>> peripheral with >>> very long LUNs that didn't work before will start working. Binary >>> compatibility >>> with old code is also kept. There is, however, a chance that some >>> 3rd party >>> software might be unhappy about the type widening, so I'd appreciate >>> any testing >>> results. Barring any issues, I will commit this on Friday. >> >> Interesting, Hannes Reinecke is trying to do something >> very similar in the Linux SCSI subsystem. His patch set >> today will be the third attempt in a year (by my count) >> and he might just get over the top this time. There is >> some support in my sg3_utils package for the way Linux >> is implementing "64 bit LUNs". The sg3_utils package >> also supports FreeBSD so I'm interested in what your >> mapping will be. >> >> Now, as you are no doubt aware, SCSI (www.t10.org and specifically >> sam5r15.pdf) does not have 64 bit LUNs, it has 8 byte LUNs in >> SCSI order (i.e. big endian). Given that major architectures >> like i386 and x86_64 are little endian, the mapping between >> a 64 bit integer in native form and an 8 byte SCSI LUN is >> a bit of a puzzle. That becomes a little harder when you try >> for low numbered integers representing the T10 3 bit LUNs >> (showing my age), 8 bit LUNs and 16 bit LUNs. >> >> Down to brass tacks: what exactly will a SCSI REPORT LUNS >> WELL KNOWN LOGICAL UNIT number [T10 (in hex): c1 01 00 00 >> 00 00 00 00] be in one of your 64 bits LUNs? Will that be >> the same in little endian and big endian architectures? >> There is also the representation of that LUN in logs; for >> example lun=13907397124296802304 is not very intuitive. >> >> More examples would be great, perhaps from the 4, 6 and 8 byte >> "extended logical unit addressing format". >> >> >> Robert Elliott who has been a T10 technical editor has written >> a paper on this subject but google fails me, perhaps someone >> else can supply the url. His advice was too late for Linux >> and perhaps it is already too late for FreeBSD. > > The document I was trying to find was a www.t10.org proposal: > 06-003r1, see its overview for a rationale. The Logical Unit > Representation Format section was accepted and can be found > in sam5r15.pdf section 4.7.2 > > Doug Gilbert > > Ah, OK. That we are following. -Nathan