From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Wed, 16 May 2001 08:45:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Wed, 16 May 2001 08:45:48 -0400 Received: from burdell.cc.gatech.edu ([130.207.3.207]:28932 "EHLO burdell.cc.gatech.edu") by vger.kernel.org with ESMTP id ; Wed, 16 May 2001 08:45:39 -0400 Message-ID: <3B02766E.8F6A040B@cc.gatech.edu> Date: Wed, 16 May 2001 08:45:34 -0400 From: Josh Fryman Organization: CoC, GaTech X-Mailer: Mozilla 4.77 [en] (X11; U; SunOS 5.7 sun4u) X-Accept-Language: en MIME-Version: 1.0 To: Oystein Viggen CC: Helge Hafting , "Chemolli Francesco (USI)" , linux-kernel@vger.kernel.org Subject: Re: LANANA: To Pending Device Number Registrants In-Reply-To: <3B0261EC.23BE5EF0@idb.hist.no> <031ypp1oi2.fsf@colargol.tihlde.org> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Oystein Viggen wrote: > What happens if I insert a hard drive from another computer which also > has partitions named "home", "usr", and soforth? not to belabor the obvious, but there are a lot of issues with this particular approach. for those who advocate writing some form of signature into an NVM space on each device that can support it (and using this signature to appropriately configure the right device), there are obvious solutions: (1) use a "motherboard serial number" or (2) the infamous CPU serial number pre-pended to whatever tag for disk/cdrw/etc. thus, it's easy to know when a device has just been moved within the same machine, or has been relocated to a new machine. no conflict will be found. for those who are willing to take a step back and look at the big picture, (a) not every device on the planet has a unique key associated with it as many people keep pointing out; (b) not every device has some area of "user" (eg, not hardware manufacturer) space that can be programmed that is NVM. if you have a situation of BOTH (a) and (b) then you are screwed, period. use an arbitrary ordering, as there's no other possible choice - and no way to preserve anything. note that "arbitrary" can just be "sequential scan of bus + assign based on sequence # found" to get pseudo-logical ordering *just as easily* as doing "scan bus + randomly assign" if however you can do either (a) or (b), then the problem is solved. the more interesting question is: for what class of devices does neither unique-key or storage-NVM exist? and are they important? serial ports, for example, are important. if i am monitoring a UPS on ttyS0 and it suddenly gets remapped on the next boot to ttyS9, that would be bad. likewise printers and such. but is there any kind of unique key or trigger that can be found for them?