From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752859AbZHLOkE (ORCPT ); Wed, 12 Aug 2009 10:40:04 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752177AbZHLOkD (ORCPT ); Wed, 12 Aug 2009 10:40:03 -0400 Received: from smtp.knology.net ([24.214.63.101]:48837 "EHLO smtp.knology.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751116AbZHLOkB (ORCPT ); Wed, 12 Aug 2009 10:40:01 -0400 Subject: Re: [PATCH] Driver Core: devtmpfs - kernel-maintained tmpfs-based /dev From: David Dillow To: Greg KH Cc: Andi Kleen , Greg KH , Alan Cox , linux-kernel@vger.kernel.org, Kay Sievers , Jan Blunck , Harald Hoyer , Scott James Remnant , Arjan van de Ven In-Reply-To: <20090812134440.GA28839@kroah.com> References: <87ljlxhrnr.fsf@basil.nowhere.org> <1249575658.19886.8.camel@lap75545.ornl.gov> <20090806183147.GA28409@suse.de> <1249772876.22248.34.camel@obelisk.thedillows.org> <20090810153943.GB7652@kroah.com> <1250001374.22248.65.camel@obelisk.thedillows.org> <20090811145523.GD14368@basil.fritz.box> <1250036727.26788.7.camel@obelisk.thedillows.org> <20090812003433.GA25392@kroah.com> <1250081813.26788.13.camel@obelisk.thedillows.org> <20090812134440.GA28839@kroah.com> Content-Type: text/plain Date: Wed, 12 Aug 2009 10:39:57 -0400 Message-Id: <1250087997.8566.9.camel@obelisk.thedillows.org> Mime-Version: 1.0 X-Mailer: Evolution 2.24.5 (2.24.5-2.fc10) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2009-08-12 at 06:44 -0700, Greg KH wrote: > On Wed, Aug 12, 2009 at 08:56:53AM -0400, David Dillow wrote: > > On Tue, 2009-08-11 at 17:34 -0700, Greg KH wrote: > > > On Tue, Aug 11, 2009 at 08:25:27PM -0400, David Dillow wrote: > > > > So use Eric/Arjan's program that does it in 60ms -- you get a > > > > dynamic /dev, no initrd, fast boot, and no kernel changes required. > > > > > > Their program only handles it for a reconstruction of /dev based on > > > sysfs one time at boot. It does not handle things that are added or > > > discovered by the system after that, you need udev for that. > > > > > > So it's a great hack for boot time stuff, but not a complete /dev > > > management replacement like this code can be for numerous systems. > > > > What systems would those be? > > Rescue disks, Embedded systems with no local users, servers with no > local users, etc. Basically anything that you are only root on, and > don't care about group permissions. We've discussed those, though, and I think most of those fall under either having full control of their static environment, or would have something to watch for hotplug events -- udev or a replacement -- and so would have the ability to create the node from user space. Rescue disks may be an exception, but they only need a minimal static /dev and then run a tool to get the initial setup. If you are expecting an expert to use them, then either running the tool by hand or as a post-modprobe rule should catch updates. They can also run udev (or a replacement) with stripped rules if you want to make it friendlier to non-expert users.