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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 288C6C433E0 for ; Mon, 18 Jan 2021 10:55:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C09F722252 for ; Mon, 18 Jan 2021 10:55:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389425AbhARKzS (ORCPT ); Mon, 18 Jan 2021 05:55:18 -0500 Received: from mail.kernel.org ([198.145.29.99]:45666 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390169AbhARKdN (ORCPT ); Mon, 18 Jan 2021 05:33:13 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id A031620784; Mon, 18 Jan 2021 10:32:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1610965952; bh=O8rxHjohu5zf7IH0KL94YVasVxp2kmKJRdlQVrIOQwk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Ac4oQ0wFZSxiNkrxiliiEGGoz+brl+ws6TptiNTSFKQEOgSLDb7ZsTtybbLLx+6T9 awYyW9CVCZNYLILoEpTXfUOU1BC8Uwd+ArVVpeYqdO4JRXu2LM/xRQEbpJ9gfNRjJo H8oENSXZqN9NL6LIBKlD++FrO4lYzQsM7LRykBr4= Date: Mon, 18 Jan 2021 11:32:29 +0100 From: Greg KH To: Masahiro Yamada Cc: Sasha Levin , Michal Marek , Linus Torvalds , Linux Kbuild mailing list , Linux Kernel Mailing List , stable@kernel.org Subject: Re: [PATCH] kbuild: give SUBLEVEL more room in KERNEL_VERSION Message-ID: References: <20210118014951.250815-1-sashal@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 18, 2021 at 07:27:51PM +0900, Masahiro Yamada wrote: > On Mon, Jan 18, 2021 at 6:21 PM Greg KH wrote: > > > > On Sun, Jan 17, 2021 at 08:49:51PM -0500, Sasha Levin wrote: > > > SUBLEVEL only has 8 bits of space, which means that we'll overflow it > > > once it reaches 256. > > > > > > Few of the stable branches will imminently overflow SUBLEVEL while > > > there's no risk of overflowing VERSION. > > > > > > Thus, give SUBLEVEL 8 more bits which will be stolen from VERSION, this > > > should create a better balance between the different version numbers we > > > use. > > > > > > The downside here is that Linus will have 8 bits less to play with, but > > > given our current release cadence (~10 weeks), the number of Linus's > > > fingers & toes (20), and the current VERSION (5) we can calculate that > > > VERSION will overflow in just over 1,000 years, so I'm kicking this can > > > down the road. > > > > > > Cc: stable@kernel.org > > > Signed-off-by: Sasha Levin > > > --- > > > Makefile | 4 ++-- > > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > > > diff --git a/Makefile b/Makefile > > > index 9e73f82e0d863..dc2bad7a440d8 100644 > > > --- a/Makefile > > > +++ b/Makefile > > > @@ -1252,8 +1252,8 @@ endef > > > > > > define filechk_version.h > > > echo \#define LINUX_VERSION_CODE $(shell \ > > > - expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + 0$(SUBLEVEL)); \ > > > - echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))' > > > + expr $(VERSION) \* 16777216 + 0$(PATCHLEVEL) \* 65536 + 0$(SUBLEVEL)); \ > > > + echo '#define KERNEL_VERSION(a,b,c) (((a) << 24) + ((b) << 16) + (c))' > > > > As much as I agree, this will break in-tree users of LINUX_VERSION_CODE > > that try to suck out the version/patchlevel number of the kernel release > > into their own fields. Things like USB host controller strings, v4l > > ioctl reports, scsi driver ioctls, and other places do fun bit-movements > > to try to unreverse this bit packing. > > > I can see a checkpatch warning about LINUX_VERSION_CODE. > > See line 4528 of scripts/checkpatch.pl > > > WARN("LINUX_VERSION_CODE", > "LINUX_VERSION_CODE should be avoided, code should be for the > version to which it is merged\n" . $herecurr); > > > > It helps external modules to be compiled for multiple kernel versions. > > #if KERNEL_VERSION_CODE < KERNEL_VERSION(5, 4, 0) > code for the kernel versions older than 5.4.0 > #endif > > > The upstream code does not do this. > But, LINUX_VERSION_CODE is actually used in many places... Yes, it is used in a number of user/kernel apis for various reasons. And the above patch will break them :( thanks, greg k-h