From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756859AbZEBNqc (ORCPT ); Sat, 2 May 2009 09:46:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753931AbZEBNqU (ORCPT ); Sat, 2 May 2009 09:46:20 -0400 Received: from fg-out-1718.google.com ([72.14.220.158]:14478 "EHLO fg-out-1718.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753920AbZEBNqT (ORCPT ); Sat, 2 May 2009 09:46:19 -0400 MIME-Version: 1.0 In-Reply-To: <20090502071939.GA14094@infradead.org> References: <1241097822.2516.3.camel@poy> <20090430222900.c13b63d5.akpm@linux-foundation.org> <20090501061701.GB19234@kroah.com> <20090430234312.a63fa5cf.akpm@linux-foundation.org> <20090501065527.GA19773@kroah.com> <20090501120359.05bacb48@lxorguk.ukuu.org.uk> <20090501141846.4b833700@lxorguk.ukuu.org.uk> <20090502071939.GA14094@infradead.org> From: Kay Sievers Date: Sat, 2 May 2009 15:46:03 +0200 Message-ID: Subject: Re: [PATCH] driver-core: devtmpfs - driver core maintained /dev tmpfs To: Christoph Hellwig Cc: 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 Sat, May 2, 2009 at 09:19, Christoph Hellwig wrote: > On Fri, May 01, 2009 at 03:24:01PM +0200, Kay Sievers wrote: >> I'm very sure, you can not fix it outside the kernel. Or do you have >> an idea how to create the missing device nodes for device without >> crawling sysfs, when the first userspace process is started? > > Just make sure to queue up your uevents in a ring buffer that udev > can read once it has started? Which does not really target any of the problems we try to solve, and is probably even larger than the 300 lines to create the proper /dev stuff right away. It's about fractions of a second, we are optimizing for, and we need to start as many things in parallel, as early as possible. And a working and populated /dev is mandatory for most of the stuff we need to bring up. I think the init=/bin/sh case alone would be justification enough to do that, it can save you a lot of trouble if things go wrong, which things do, and which is pretty hard to cope with today, with no access to your devices. We are not implementing anything crazy here like devfs did, including the later versions - there is no modprobe behind your back, no lookup hooks, no stupid new naming scheme, no new filesystem type to register. Udev uses the kernel provided names anyway today, there are no naming rules at all in current userspace for 98 of 100 devices. It's todays kernel which provides the naming already, and we will not change anything here, just add the few exceptions, which are only in udev rules today, and let the kernel create the node that udev will create anyway. Thanks, Kay