From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id F2E68C433DF for ; Fri, 31 Jul 2020 21:27:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C34B42087C for ; Fri, 31 Jul 2020 21:27:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729062AbgGaV1a (ORCPT ); Fri, 31 Jul 2020 17:27:30 -0400 Received: from relay5-d.mail.gandi.net ([217.70.183.197]:39629 "EHLO relay5-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727888AbgGaV1a (ORCPT ); Fri, 31 Jul 2020 17:27:30 -0400 X-Originating-IP: 50.39.163.217 Received: from localhost (50-39-163-217.bvtn.or.frontiernet.net [50.39.163.217]) (Authenticated sender: josh@joshtriplett.org) by relay5-d.mail.gandi.net (Postfix) with ESMTPSA id BAB531C0002; Fri, 31 Jul 2020 21:27:24 +0000 (UTC) Date: Fri, 31 Jul 2020 14:27:21 -0700 From: josh@joshtriplett.org To: Arnd Bergmann Cc: ksummit , Mike Rapoport , linux-arch , Linux Kernel Mailing List Subject: Re: [Ksummit-discuss] [TECH TOPIC] Planning code obsolescence Message-ID: <20200731212721.GC32670@localhost> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 31, 2020 at 05:00:12PM +0200, Arnd Bergmann wrote: > The majority of the code in the kernel deals with hardware that was made > a long time ago, and we are regularly discussing which of those bits are > still needed. In some cases (e.g. 20+ year old RISC workstation support), > there are hobbyists that take care of maintainership despite there being > no commercial interest. In other cases (e.g. x.25 networking) it turned > out that there are very long-lived products that are actively supported > on new kernels. > > When I removed support for eight instruction set architectures in 2018, > those were the ones that no longer had any users of mainline kernels, > and removing them allowed later cleanup of cross-architecture code that > would have been much harder before. > > I propose adding a Documentation file that keeps track of any notable > kernel feature that could be classified as "obsolete", and listing > e.g. following properties: > > * Kconfig symbol controlling the feature > > * How long we expect to keep it as a minimum > > * Known use cases, or other reasons this needs to stay > > * Latest kernel in which it was known to have worked > > * Contact information for known users (mailing list, personal email) > > * Other features that may depend on this > > * Possible benefits of eventually removing it We had this once, in the form of feature-removal-schedule.txt. It was, itself, removed in commit 9c0ece069b32e8e122aea71aa47181c10eb85ba7. I *do* think there'd be value in having policies and processes for "how do we carefully remove a driver/architecture/etc we think nobody cares about". That's separate from having an actual in-kernel list of "things we think we can remove".