From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Reinecke Subject: Re: [PATCH] st: Do not rewind for SG_IO Date: Thu, 06 Feb 2014 14:10:01 +0100 Message-ID: <52F389A9.808@suse.de> References: <1391157974-17512-1-git-send-email-hare@suse.de> <52EBD2BB.8020705@tributary.com> <52ECFF7B.7000401@suse.de> <60EE5D9C-A799-4C8D-8962-DB9D7C1C8414@kolumbus.fi> <52EE2F2D.1010300@suse.de> <52EFACA4.6060001@tributary.com> <52EFB06C.8010101@suse.de> <52EFB0E7.3000504@tributary.com> <52F010F9.5090305@tributary.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from cantor2.suse.de ([195.135.220.15]:41732 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756322AbaBFNKD (ORCPT ); Thu, 6 Feb 2014 08:10:03 -0500 In-Reply-To: <52F010F9.5090305@tributary.com> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Jeremy Linton , Kay Sievers Cc: =?UTF-8?B?IkthaSBNw6RraXNhcmEgKEtvbHVtYnVzKSI=?= , James Bottomley , "linux-scsi@vger.kernel.org" , Doug Gilbert On 02/03/2014 10:58 PM, Jeremy Linton wrote: > On 2/3/2014 2:51 PM, Kay Sievers wrote: >> This is not simple and not going to happen. Sibling devices in /sys = cannot >> have a relationship in udev, there are only parent/child dependencie= s. >=20 > Ok.. so if we can't ignore all the "spare" device nodes in a given /= sys entry > for a given device. Why open the device to scan it? >=20 > I've often wondered why the serial number isn't part of the data in = /sys > along with the manufacture/model. The last tape drive I saw that fail= ed to > respond to inquiry page 0x80 was over a decade ago (probably manufact= ured in > the early 90s). So enabling it just for tape is pretty safe. >=20 >=20 > Matching Manufacturer/model/serial is going to be better than anythi= ng your > going to get out of 0x83 anyway. That data is guaranteed to be there,= but its > also guaranteed to be unreliable (every device, and every port has a = slightly > different set of descriptors they choose to support). >=20 > Plus, your not going to have issues accidentally rewinding a device,= or > resetting a tape density, or accidentally turning compression off if = you don't > open the device. >=20 And indeed, I have been wondering about this, too. And (again) it is something which has been on my To-Do list for a long time. Moving EVPD page 0x83 (and maybe 0x80, too) into sysfs will save quite a lot of headache we have currently; udev won't have to call 'sg_inq', information will be present even though the device itself might be temporarily unavailable yadda yadda. So I've decided to bite the bullet and sent out a patch, check for 'Add EVPD page 0x83 entries to sysfs'. Reviews are welcome. Cheers, Hannes --=20 Dr. Hannes Reinecke zSeries & Storage hare@suse.de +49 911 74053 688 SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 N=C3=BCrnberg GF: J. Hawn, J. Guild, F. Imend=C3=B6rffer, HRB 16746 (AG N=C3=BCrnberg= ) -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html