linux-kernel - Re: [PATCH 2/2] ARM: configs: Cleanup old Kconfig options

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Date:   Sun, 9 Feb 2020 03:44:22 -0800
From:   Olof Johansson <olof@...om.net>
To:     Krzysztof Kozlowski <krzk@...nel.org>
Cc:     Joe Perches <joe@...ches.com>,
        Russell King <linux@...linux.org.uk>,
        Alexander Shiyan <shc_work@...l.ru>,
        Uwe Kleine-K??nig <u.kleine-koenig@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Vladimir Zapolskiy <vz@...ia.com>,
        Aaro Koskinen <aaro.koskinen@....fi>,
        Tony Lindgren <tony@...mide.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Liviu Dudau <liviu.dudau@....com>,
        Sudeep Holla <sudeep.holla@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Avi Fishman <avifishman70@...il.com>,
        Tomer Maimon <tmaimon77@...il.com>,
        Tali Perry <tali.perry1@...il.com>,
        Patrick Venture <venture@...gle.com>,
        Nancy Yuen <yuenn@...gle.com>,
        Benjamin Fair <benjaminfair@...gle.com>,
        Arnd Bergmann <arnd@...db.de>,
        linux-arm-kernel@...ts.infradead.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-omap@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com, openbmc@...ts.ozlabs.org,
        arm@...nel.org, soc@...nel.org
Subject: Re: [PATCH 2/2] ARM: configs: Cleanup old Kconfig options

On Mon, Feb 03, 2020 at 12:52:45PM +0100, Krzysztof Kozlowski wrote:
> On Thu, 30 Jan 2020 at 23:06, Joe Perches <joe@...ches.com> wrote:
> >
> > On Thu, 2020-01-30 at 20:55 +0100, Krzysztof Kozlowski wrote:
> > > CONFIG_MMC_BLOCK_BOUNCE is gone since commit c3dccb74be28 ("mmc: core:
> > > Delete bounce buffer Kconfig option").
> > >
> > > CONFIG_LBDAF is gone since commit 72deb455b5ec ("block: remove
> > > CONFIG_LBDAF").
> > >
> > > CONFIG_IOSCHED_DEADLINE and CONFIG_IOSCHED_CFQ are gone since
> > > commit f382fb0bcef4 ("block: remove legacy IO schedulers").
> > >
> > > The IOSCHED_DEADLINE was replaced by MQ_IOSCHED_DEADLINE and it will be
> > > now enabled by default (along with MQ_IOSCHED_KYBER).
> > >
> > > The IOSCHED_BFQ seems to replace IOSCHED_CFQ so select it in configs
> > > previously choosing the latter.
> > >
> > > CONFIG_CROSS_COMPILE is gone since commit f1089c92da79 ("kbuild: remove
> > > CONFIG_CROSS_COMPILE support").
> >
> > Hi Krzysztof.
> >
> > There seems there are a lot more of these unused CONFIG_<foo>
> > symbols in various defconfigs. (just for arm and treewide below)
> >
> > ARM defconfigs:
> 
> Hi Joe,
> 
> Nice finding! The trickier point is to nicely remove them because:
> 1. The easiest is 'savedefconfig' but then some valuable options might
> disappear (like recently happened with DEBUG_FS),

Note that while they disappear from the defconfig, they were already not part
of the build. So kernels have been built without them for a while. It's a good
way to surface the problem, but it's pretty clear that trees fall in the forest
here all the time and nobody is noticing.

> 2. They could be removed in automated way with a script. However in
> such case what about replacements? If some symbol was replaced with
> other (or just renamed), maybe we should enable the other one to
> restore the desired functionality?
> 3. Or maybe let's don't care about keeping defconfigs stable and just
> clean them up automatically.

Churning defconfigs is just noise, and a source of annoying needless
conflicts when people do it at the same time. If an option is no longer
in-tree, it doesn't do any harm. But it makes sense to clean up every
now and then like the original patch here.


-Olof