From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754838AbZEDTOV (ORCPT ); Mon, 4 May 2009 15:14:21 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752774AbZEDTOK (ORCPT ); Mon, 4 May 2009 15:14:10 -0400 Received: from mail-bw0-f174.google.com ([209.85.218.174]:38686 "EHLO mail-bw0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751830AbZEDTOJ (ORCPT ); Mon, 4 May 2009 15:14:09 -0400 MIME-Version: 1.0 In-Reply-To: <49FF3A26.3030407@googlemail.com> References: <20090501061701.GB19234@kroah.com> <49FC8EE4.6040408@googlemail.com> <9b2b86520905021255t4a4812dcrcbcc32f36acd6039@mail.gmail.com> <20090504162011.GO17956@suse.de> <49FF2BD4.3070409@googlemail.com> <49FF3A26.3030407@googlemail.com> From: Kay Sievers Date: Mon, 4 May 2009 21:13:53 +0200 Message-ID: Subject: Re: [PATCH] driver-core: devtmpfs - driver core maintained /dev tmpfs To: Michael Riepe Cc: Lars Marowsky-Bree , Alan Jenkins , Alan Cox , Greg KH , Andrew Morton , linux-kernel , Jan Blunck Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 4, 2009 at 20:55, Michael Riepe wrote: >> Dynamic device numbers! A static /dev does not work at all for many >> subsystems, not to mention the risk you take by talking to the wrong >> device pointed to, by your incorrect static device nodes. It's not an >> option at all today, and it will get much worse in the future. > > Maybe it's just me, but my devices end up being numbered the same after > every reboot. Unless I add or remove devices to/from the system, of course. Sure, that works fine for most things, and will continue to do so. But there are entire subsystems in the kernel, mostly newer ones, which do not have any static number assignment and require dynamic /dev support. It's not about /dev/null and /dev/tty and such, that will not change, but there is already an option in the upstream kernel to assign dynamic numbers to sd* disks to allow more than 15 partitions, and the numbers of subsystem requiring dynamic numbers will likely grow. The thing today is that userspace on distro systems messes around in /dev and assigns access control lists to grant device-access to specific users, udev creates many symlinks there to identify your devices, because the kernel names get reordered, and nothing will ever revert /dev to the state where it came from at boot. So the wider support for a static /dev is kind of fading away, stuff that works today statically will likely continue to work, but all the new stuff will not work with a static /dev. That's one part of what devtmpfs addresses. Thanks, Kay