From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262848AbTLIFEg (ORCPT ); Tue, 9 Dec 2003 00:04:36 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262859AbTLIFEg (ORCPT ); Tue, 9 Dec 2003 00:04:36 -0500 Received: from dsl092-053-140.phl1.dsl.speakeasy.net ([66.92.53.140]:59337 "EHLO grelber.thyrsus.com") by vger.kernel.org with ESMTP id S262848AbTLIFEe (ORCPT ); Tue, 9 Dec 2003 00:04:34 -0500 From: Rob Landley Reply-To: rob@landley.net To: Andrew Walrond , linux-kernel@vger.kernel.org Subject: Re: State of devfs in 2.6? Date: Mon, 8 Dec 2003 23:04:33 -0600 User-Agent: KMail/1.5 References: <200312081536.26022.andrew@walrond.org> <20031208154256.GV19856@holomorphy.com> <200312081559.04771.andrew@walrond.org> In-Reply-To: <200312081559.04771.andrew@walrond.org> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200312082304.33891.rob@landley.net> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Monday 08 December 2003 09:59, Andrew Walrond wrote: > On Monday 08 Dec 2003 3:42 pm, William Lee Irwin III wrote: > > I would say it's deprecated at the very least. sysfs and udev are > > supposed to provide equivalent functionality, albeit by a somewhat > > different mechanism. > > Thanks for the pointer. > > So how good is the device coverage offered by sysfs/udev ? Do they provide > a viable/complete MAKEDEV replacement yet? My understanding is that udev takes the information exported by sysfs about what devices exist in the system, and creates device nodes in /dev (which can be a ramfs mount or part of a persistent filesystem, udev itself doesn't care). I'm guessing it traverses sysfs to see what the system's got on startup (some variant of "find /sys -name device", perhaps) and then receives hotplug events when new devices are added later. On the whole, this is generally cool, hotplug friendly, and small and simple. _and_ the result looks like a recognizable /dev directory, so end-user applications don't have to be "devfs aware" (which was a bad sign from day 1 if you ask me). Unfortunately, sysfs doesn't yet export device node information for everything in the system yet. (There aren't any under /sys/cdev, /sys/devices/legacy, or /sys/devices/system, for example). There are pending patches to add more, but they're not considered bug fixes, so Linus won't take them before 2.6.0 and we'll have to wait until after 2.6.0 for development on this subsystem to finish. Probably somewhere in the 2.6.4 to 2.6.6 timeframe, sysfs will have all the device exports udev needs. (Or at least all the ones anybody's complained about yet.) Until then... dunno. Maybe you can use a /dev directory on a persistent filesystem that you mknod any extra devices you need into yourself?) Rob