Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1755236Ab1FPQPV (ORCPT <rfc822;w@1wt.eu>);
	Thu, 16 Jun 2011 12:15:21 -0400
Received: from out4.smtp.messagingengine.com ([66.111.4.28]:53347 "EHLO
	out4.smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK)
	by vger.kernel.org with ESMTP id S1754839Ab1FPQPU (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Thu, 16 Jun 2011 12:15:20 -0400
X-Sasl-enc: CndObrFUIBP7fz2kWsjBfRWfyY1XYVZLHn4ZmIpU90EF 1308240918
Date: Thu, 16 Jun 2011 09:14:42 -0700
From: Greg KH <greg@kroah.com>
To: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Nao Nishijima <nao.nishijima.xt@hitachi.com>, linux-scsi@vger.kernel.org,
        linux-kernel@vger.kernel.org, kay.sievers@vrfy.org, jcm@redhat.com,
        hare@suse.de, stefanr@s5r6.in-berlin.de, yrl.pp-manager.tt@hitachi.com
Subject: Re: [PATCH 1/3] [RFC] genhd: add a new attribute in device structure
Message-ID: <20110616161442.GA32113@kroah.com>
References: <20110615081610.2237.44767.stgit@ltc233.sdl.hitachi.co.jp>
 <20110615081627.2237.9620.stgit@ltc233.sdl.hitachi.co.jp>
 <20110615153337.GA10160@kroah.com>
 <4DF9F11F.705@hitachi.com>
 <20110616154129.GA31498@kroah.com>
 <1308239454.2436.34.camel@mulgrave>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1308239454.2436.34.camel@mulgrave>
User-Agent: Mutt/1.5.21 (2010-09-15)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 2262
Lines: 49

On Thu, Jun 16, 2011 at 11:50:54AM -0400, James Bottomley wrote:
> > And again, why not just fix the userspace tools?  That is trivial to do
> > so and again, could have been done by now in the years this has been
> > discussed.
> 
> So I can summarise where I think we are in these discussions:
> 
> We provide the ability to give all kernel devices a "preferred name".
> By default this will be the device name the kernel would have originally
> assigned.  the dev_printk's will use the preferred name, and it will be
> modifiable from user space.  All the kernel will do is print out
> whatever it is ... no guarantees of uniqueness or specific format will
> be made.  Since we're only providing one preferred_name file, the kernel
> can only have one preferred name for a device at any given time
> (although it is modifiable on the fly as many times as the user
> chooses).
> 
> The design is to use this preferred name to implement what Hitachi wants
> in terms of persistent name, but we don't really care.
> 
> All userspace naming will be taken care of by the usual udev rules, so
> for disks, something like /dev/disk/by-preferred/<fred> which would be
> the usual symbolic link.

No, udev can not create such a link after the preferred name is set, as
it has no way of knowing that the name was set.

> This will ensure that kernel output and udev input are consistent.  It
> will still require that user space utilities which derive a name for a
> device will need modifying to print out the preferred name.

It also doesn't solve the issue of userspace wanting to use such a
"preferred" name in the command line of tools, as there will not be a
link back to the "kernel" name directly in /dev/.

So as userspace tools will still need to be fixed, I don't see how
adding a kernel file for this is going to help any.  Well, a bit in that
the kernel log files will look "different", but again, that really isn't
a problem that userspace couldn't also solve with no kernel changes
needed.

thanks,

greg k-h
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/