From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oliver Neukum Subject: Re: READ_CAPACITY_16 vs. READ_CAPACITY_10 Date: Mon, 16 Sep 2013 14:41:21 +0200 Message-ID: <1379335281.15916.38.camel@linux-fkkt.site> References: <52315559.3080708@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: Received: from cantor2.suse.de ([195.135.220.15]:38025 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753047Ab3IPMlX (ORCPT ); Mon, 16 Sep 2013 08:41:23 -0400 In-Reply-To: <52315559.3080708@suse.de> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Hannes Reinecke Cc: Alan Stern , linux-scsi@vger.kernel.org On Thu, 2013-09-12 at 07:47 +0200, Hannes Reinecke wrote: > On 09/11/2013 04:14 PM, Alan Stern wrote: > > On Tue, 10 Sep 2013, Oliver Neukum wrote: > >> I think we can be sure that no drive enclosure will crash > >> with READ_CAPACITY_16. > > > > I wouldn't count on it, but I don't know of any examples. > > > Me neither. The whole issue just smells of some firmware coders > messing up their stuff. So I would think that other firmwares > might not have this problem. Certainly. But does it matter? We would be happy to always use READ_CAPACITY_16 first, if it weren't for other buggy firmware. > (But as HS enclosures aren't that common chances are we've hit > the same firmware by chance on every test machine we've had.) > > I think it would warrant a quirk approach. Yes, it might be slightly > more coding, but at the same time it's more selective on where it > should trigger. Yes and we would for sure miss many cases. > Also looking at scsiglue.c it would make things quite tricky if > you'd want to _disable_ this feature for HS devices; other firmware Just another quirk. > from other vendors might not exhibit this issue after all. > And scsiglue.c already has tons of quirks set, adding one more > doesn't do any harm. It doesn't do harm if the number of devices to be added is small. The enclosure works under Windows. So we know that it uses READ_CAPACITY_16 under some circumstances. Unfortunately I haven't dug up a Windows box as yet. However we can realistically hope that the firmwares become fixed only if Windows _fails_ to use READ_CAPACITY_16 under some circumstances. Regards Oliver