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Fri, 31 Jul 2020 08:00:28 -0700 (PDT) MIME-Version: 1.0 From: Arnd Bergmann Date: Fri, 31 Jul 2020 17:00:12 +0200 X-Gmail-Original-Message-ID: Message-ID: To: ksummit , Mike Rapoport , linux-arch , Linux Kernel Mailing List X-Provags-ID: V03:K1:VrofbhoJLiHh/36/AtEluLcSahHhMpjZ1cyokYDo1MtpzwvOrPE kb0n8B8XkSTXLU/VT27Z3+CTzu3K2S3hdrevw0WhEDoSxlN4yr1bvzZ/MFOeJQeBlj22KRb qpMcPs2nIhCQesSDdGmjHpZZiQp+2rJrxrLxC7q/hvZ/p0fnc+3Uy+rl8+KN505kTNMOGMT MiHvL9zKYg0hTLK6unv1w== X-UI-Out-Filterresults: notjunk:1;V03:K0:gVtMiZ2fv88=:jh4hAwVocj/xJ0r0/Eaou7 M38M60Fc4Qf5mxxqW5JaTqENegumkP2liz4sfMfzOvDb5cyDHiZgqCGWVUzWeVMcJosf1ms/Z xDwf02yzAY3dFP6QWoT13lHaN0prH9cknljb7S2UeAtm6SoV/Cj9PxsJy6Aj6K4O2gTuLqstr cxHDaSErPbpMD9X2VjJ6vFYomskuXqgqMlsmlznY4y1kNeCMqk8Hz4w0BGuVfepCkhxViLc7h ZrL5R8l4aMdBheh4JhxyFX6r1VwxPS+QTAHL+jHfgh0kPotAlsR6wrWUqJ9FQNW2inXlqgnhT EaPZF94LNnWOEPDUI2e9QLtdddOmAsSLs1KPltqvQjvf+F2p6TihRhZ2ZG9hKHyc51g4QmwmI OV8Rc3OTbXq+/gHB8oP3XnhDYE0C93lM33yJLBgwZaPbsrinOdDUTwqSBqFeGOvAva4gmA6d7 BYTH5/74lE7tHd3I4tfQQK5Ju40Muk54kgtYRrOjHXKl09DVxcfndC0eJd1nC8Jdd8GVP1ruM B3gZt8O7xHjybt/+8sKKnz0PVEklL1Qzpa7QNEHqS5MDzW3ByHLHc+b2EOnpBZmLYgAS1feob 031vTpn/nWw1R4QfufguwgfQngr+R8dpyLyUOmlAAY21XmN4A2tHTpTU0GEq5Rv7kOXKza4y6 TW2ya79uz6kSWFtBkrKxyLGczYccbQqco/VrIn3xy9BZfuneBFFpP7XagatCVLrxolPkInB9/ g1DVde2+socSb+bxaw1sp0XlI1Q2RPy9acYSusOq+7YRTA4RtPYLg0f5aBV+/9q+/6IdMa8VW hRtNqE0Yc9mtEVrcQz8Va7lqzFpXb+pXX+4oKuJt/8VuCkcAD17L02AyGT1DTM9iQ4SJVcX Subject: [Ksummit-discuss] [TECH TOPIC] Planning code obsolescence X-BeenThere: ksummit-discuss@lists.linuxfoundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: ksummit-discuss-bounces@lists.linuxfoundation.org Sender: "Ksummit-discuss" I have submitted the below as a topic for the linux/arch/* MC that Mike and I run, but I suppose it also makes sense to discuss it on the ksummit-discuss mailing list (cross-posted to linux-arch and lkml) as well even if we don't discuss it at the main ksummit track. Arnd 8<--- 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 With that information, my hope is that it becomes easier to plan when some code can be removed after the last users have stopped upgrading their kernels, while also preventing code from being removed that is actually still in active use. In the discussion at the linux/arch/* MC, I would hope to answer these questions: * Do other developers find this useful to have? * Where should the information be kept (Documentation/*, Kconfig, MAINTAINERS, wiki.kernel.org, ...) * Which information should be part of an entry? * What granularity should this be applied to -- only high-level features like CPU architectures and subsystems, or individual drivers and machines? _______________________________________________ Ksummit-discuss mailing list Ksummit-discuss@lists.linuxfoundation.org https://lists.linuxfoundation.org/mailman/listinfo/ksummit-discuss