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

[Olof Johansson]

On Mon, Feb 03, 2020 at 12:52:45PM +0100, Krzysztof Kozlowski wrote:
> On Thu, 30 Jan 2020 at 23:06, Joe Perches <joe@xxxxxxxxxxx> 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