Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750890AbWB1GcR (ORCPT ); Tue, 28 Feb 2006 01:32:17 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751905AbWB1GcR (ORCPT ); Tue, 28 Feb 2006 01:32:17 -0500 Received: from thunk.org ([69.25.196.29]:34007 "EHLO thunker.thunk.org") by vger.kernel.org with ESMTP id S1750890AbWB1GcQ (ORCPT ); Tue, 28 Feb 2006 01:32:16 -0500 Date: Tue, 28 Feb 2006 01:32:07 -0500 From: "Theodore Ts'o" To: Greg KH Cc: Linus Torvalds , Greg KH , Benjamin LaHaise , linux-kernel@vger.kernel.org, Andrew Morton , davej@redhat.com, perex@suse.cz, Kay Sievers Subject: Re: [RFC] Add kernel<->userspace ABI stability documentation Message-ID: <20060228063207.GA12502@thunk.org> Mail-Followup-To: Theodore Ts'o , Greg KH , Linus Torvalds , Greg KH , Benjamin LaHaise , linux-kernel@vger.kernel.org, Andrew Morton , davej@redhat.com, perex@suse.cz, Kay Sievers References: <20060227190150.GA9121@kroah.com> <20060227193654.GA12788@kvack.org> <20060227194623.GC9991@suse.de> <20060227234525.GA21694@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20060227234525.GA21694@suse.de> User-Agent: Mutt/1.5.11+cvs20060126 X-SA-Exim-Connect-IP: X-SA-Exim-Mail-From: tytso@thunk.org X-SA-Exim-Scanned: No (on thunker.thunk.org); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2209 Lines: 45 On Mon, Feb 27, 2006 at 03:45:25PM -0800, Greg KH wrote: > > So I just don't see any upsides to documenting anything private or > > unstable. I see only downsides: it's an excuse to hide behind for > > developers. > > So should we just not even document anything we consider "unstable"? > The first trys at things are usually really wrong, and that only can be > detected after we've tried it out for a while and have a few serious > users. Should we brand anything new as "testing" if the developer feels > it is ready to go? How about "we don't let anything into mainline that we consider 'unstable' from an interface point of view"? There seems to be a fetish going on today that everything possible should be mindlessly pushed out into userspace regardless of whether or not it makes sense. What folks don't seem to understand is that there is a tradeoff between implementational complexity (in terms of lines of code in /usr/src/linux) and interface complexity (see Rusty's talk about designing good interfaces and how hard that can be). If we're not sure we can get the interface right, then maybe it's a sign it needs to stay in -mm longer, or maybe we were trying to push the wrong thing out into userspace. If the interface isn't easy to understand, and we aren't confident that we can promise to never change it once we put it out there (although of course we can always add additional interfaces as we add new features), then maybe the mistake was in trying to create the interface in the first place. Don't get me wrong; I'm a big fan of pushing policy out of the kernel; but only if the interface that we use to expose the kernel functionality has been very carefully designed. Another alternative, as a few people including myself have noted, is to shipping that part of the userspace with the kernel sources, so that it is part of the kernel sources from a release management point of view, even if it lives in userspace. - Ted - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/