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Thu, 08 Sep 2022 23:24:56 -0700 (PDT) X-Gm-Message-State: ACgBeo10s5JDoXC7RCX88/guQ+5AQrfZ6al+th4hs5bksuxtbt0ZaQC/ JsAoZW3FnO2c0eLAV9weOL2I4mZ9CXsDaqfBTdM= X-Google-Smtp-Source: AA6agR68HxJp7Gt5/W9hJjJn1oNwjlIoYy1BfzwQ+ek2/Aphzioca6ZO3YEOgn/MHLAPX31bHXbrpRG4YXb9tNqZENw= X-Received: by 2002:a05:6808:1b85:b0:34d:8ce1:d5b0 with SMTP id cj5-20020a0568081b8500b0034d8ce1d5b0mr1415326oib.194.1662704695320; Thu, 08 Sep 2022 23:24:55 -0700 (PDT) MIME-Version: 1.0 References: <20220908104337.11940-1-lukas.bulwahn@gmail.com> <20220908104337.11940-7-lukas.bulwahn@gmail.com> In-Reply-To: <20220908104337.11940-7-lukas.bulwahn@gmail.com> From: Masahiro Yamada Date: Fri, 9 Sep 2022 15:24:19 +0900 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 6/6] init/Kconfig: remove confusing config EMBEDDED To: Lukas Bulwahn Cc: Russell King , linux-arm-kernel , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , X86 ML , Mauro Carvalho Chehab , Linux Media Mailing List , Peter Chen , Greg Kroah-Hartman , linux-usb , Andrew Morton , Mike Rapoport , Linux Memory Management List , Linux Kbuild mailing list , kernel-janitors@vger.kernel.org, Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1662704708; a=rsa-sha256; cv=none; b=MOn2Kr0lHvJdEUooz7B02Qfujb750bPA2CwT5Mn2n0/ZX070iTNcgENUJQduKgsYjLq7I0 fpJtThiVK5YJ3hJi1aMmnLOmT9mGv5fIW4FRFPAtDRu5Mq5gL3uV4DYnvUmInSKuvpVd8n +cvi4e/JHyjIlLDbjus7e3kVdo0ACqg= ARC-Authentication-Results: i=1; imf04.hostedemail.com; dkim=pass header.d=nifty.com header.s=dec2015msa header.b=KaFtlN+j; spf=softfail (imf04.hostedemail.com: 210.131.2.81 is neither permitted nor denied by domain of masahiroy@kernel.org) smtp.mailfrom=masahiroy@kernel.org; dmarc=fail reason="No valid SPF, DKIM not aligned (relaxed)" header.from=kernel.org (policy=none) ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1662704708; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=7NjVtVy//nlbx9x3Pt5ijYazqoLxIT1B+J2u/cAaj5Q=; b=hYfAo3RPBfel7azwJCvJKaf1k28M6QagVWF/73QkQFHuMLkdjWD0cDfMvwZco27Q0qIhRU u9EHXFsWh+tz0BL5g+nUtHDc+GU6FeSMVG51rT6SgN/3ko/lCi0MjBh0cVahou3m8KgGhW PhRYYykcUtCnuGkLt1Z0oP0uoJkkE1Q= X-Rspamd-Queue-Id: 9E9B54007C Authentication-Results: imf04.hostedemail.com; dkim=pass header.d=nifty.com header.s=dec2015msa header.b=KaFtlN+j; spf=softfail (imf04.hostedemail.com: 210.131.2.81 is neither permitted nor denied by domain of masahiroy@kernel.org) smtp.mailfrom=masahiroy@kernel.org; dmarc=fail reason="No valid SPF, DKIM not aligned (relaxed)" header.from=kernel.org (policy=none) X-Rspam-User: X-Rspamd-Server: rspam06 X-Stat-Signature: 14ode7ighzrb7fqnfk6t4xbcdixqce9c X-HE-Tag: 1662704707-402670 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Sep 8, 2022 at 7:44 PM Lukas Bulwahn wrote: > > Commit 6a108a14fa35 ("kconfig: rename CONFIG_EMBEDDED to CONFIG_EXPERT") > introduces CONFIG_EXPERT to carry the previous intent of CONFIG_EMBEDDED > and just gives that intent a much better name. That has been clearly a good > and long overdue renaming, and it is clearly an improvement to the kernel > build configuration that has shown to help managing the kernel build > configuration in the last decade. > > However, rather than bravely and radically just deleting CONFIG_EMBEDDED, > this commit gives CONFIG_EMBEDDED a new intended semantics, but keeps it > open for future contributors to implement that intended semantics: > > A new CONFIG_EMBEDDED option is added that automatically selects > CONFIG_EXPERT when enabled and can be used in the future to isolate > options that should only be considered for embedded systems (RISC > architectures, SLOB, etc). > > Since then, this CONFIG_EMBEDDED implicitly had two purposes: > > - It can make even more options visible beyond what CONFIG_EXPERT makes > visible. In other words, it may introduce another level of enabling the > visibility of configuration options: always visible, visible with > CONFIG_EXPERT and visible with CONFIG_EMBEDDED. > > - Set certain default values of some configurations differently, > following the assumption that configuring a kernel build for an > embedded system generally starts with a different set of default values > compared to kernel builds for all other kind of systems. > > Considering the first purpose, at the point in time where CONFIG_EMBEDDED > was renamed to CONFIG_EXPERT, CONFIG_EXPERT already made 130 more options > become visible throughout all different menus for the kernel configuration. > Over the last decade, this has gradually increased, so that currently, with > CONFIG_EXPERT, roughly 170 more options become visible throughout all > different menus for the kernel configuration. In comparison, currently with > CONFIG_EMBEDDED enabled, just seven more options are visible, one in x86, > one in arm, and five for the ChipIdea Highspeed Dual Role Controller. > > As the numbers suggest, these two levels of enabling the visibility of even > more configuration options---beyond what CONFIG_EXPERT enables---never > evolved to a good solution in the last decade. In other words, this > additional level of visibility of configuration option with CONFIG_EMBEDDED > compared to CONFIG_EXPERT has since its introduction never become really > valuable. It requires quite some investigation to actually understand what > is additionally visible and it does not differ significantly in complexity > compared to just enabling CONFIG_EXPERT. This CONFIG_EMBEDDED---or any > other config to show more detailed options beyond CONFIG_EXPERT---is > unlikely to be valuable unless somebody puts significant effort in > identifying how such visibility options can be properly split and creating > clear criteria, when some config option is visible with CONFIG_EXPERT and > when some config option is visible only with some further option enabled > beyond CONFIG_EXPERT, such as CONFIG_EMBEDDED attempted to do. For now, it > is much more reasonable to simply make those additional seven options that > visible with CONFIG_EMBEDDED, visible with CONFIG_EXPERT, and then remove > CONFIG_EMBEDDED. If anyone spends significant effort in structuring the > visibility of config options, they may re-introduce suitable new config > options simply as they see fit. > > Hence, all uses of CONFIG_EMBEDDED have been replaced with CONFIG_EXPERT. > > Considering the second purpose, note that already probably arguing that a > kernel build for an embedded system would choose some values differently is > already tricky: the set of embedded systems with Linux kernels is already > quite diverse. Many embedded system have powerful CPUs and it would not be > clear that all embedded systems just optimize towards one specific aspect, > e.g., a smaller kernel image size. So, it is unclear if starting with "one > set of default configuration" that is induced by CONFIG_EMBEDDED is a good > offer for developers configuring their kernels. > > Also, the differences of needed user-space features in an embedded system > compared to a non-embedded system are probably difficult or even impossible > to name in some generic way. > > So it is not surprising that in the last decade hardly anyone has > contributed changes to make something default differently in case of > CONFIG_EMBEDDED=y. > > In v6.0-rc4, SECRETMEM is the only config switched off if > CONFIG_EMBEDDED=y. That one use was removed as well, SECRETMEM was made > configurable at build time by experts using menuconfig instead. > > As there are no further uses of CONFIG_EMBEDDED and CONFIG_EMBEDDED never > lived up to its intended purpose defined above, simply delete this > confusing CONFIG_EMBEDDED. > > Signed-off-by: Lukas Bulwahn > --- > init/Kconfig | 8 -------- > 1 file changed, 8 deletions(-) > > diff --git a/init/Kconfig b/init/Kconfig > index 9e3fd79b089c..d7429e0b8cae 100644 > --- a/init/Kconfig > +++ b/init/Kconfig > @@ -1818,14 +1818,6 @@ config DEBUG_RSEQ > > If unsure, say N. > > -config EMBEDDED > - bool "Embedded system" > - select EXPERT > - help > - This option should be enabled if compiling the kernel for > - an embedded system so certain expert options are available > - for configuration. > - > config HAVE_PERF_EVENTS > bool > help > -- > 2.17.1 > So, I am supposed to pick this up after 01-05 land. (please ping me if I forget about it). For now, Reviewed-by: Masahiro Yamada -- Best Regards Masahiro Yamada