linux-kernel - Re: [PATCH] powerpc/powernv/pci: remove dead code from !CONFIG

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Message-ID: <87lf99zzl3.fsf@dja-thinkpad.axtens.net>
Date:   Fri, 23 Apr 2021 09:09:12 +1000
From:   Daniel Axtens <dja@...ens.net>
To:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Joe Perches <joe@...ches.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Oliver O'Halloran <oohall@...il.com>,
        Alexey Kardashevskiy <aik@...abs.ru>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc/powernv/pci: remove dead code from !CONFIG_EEH

Hi Nick,

> While looking at -Wundef warnings, the #if CONFIG_EEH stood out as a
> possible candidate to convert to #ifdef CONFIG_EEH, but it seems that
> based on Kconfig dependencies it's not possible to build this file
> without CONFIG_EEH enabled.

This seemed odd to me, but I think you're right:

arch/powerpc/platforms/Kconfig contains:

config EEH
	bool
	depends on (PPC_POWERNV || PPC_PSERIES) && PCI
	default y

It's not configurable from e.g. make menuconfig because there's no prompt.
You can attempt to explicitly disable it with e.g. `scripts/config -d EEH`
but then something like `make oldconfig` will silently re-enable it for
you.

It's been forced on since commit e49f7a9997c6 ("powerpc/pseries: Rivet
CONFIG_EEH for pSeries platform") in 2012 which fixed it for
pseries. That moved out from pseries to pseries + powernv later on.

There are other cleanups in the same vein that could be made, from the
Makefile (which has files only built with CONFIG_EEH) through to other
source files. It looks like there's one `#ifdef CONFIG_EEH` in
arch/powerpc/platforms/powernv/pci-ioda.c that could be pulled out, for
example.

I think it's probably worth trying to rip out all of those in one patch?

Kind regards,
Daniel