Re: [PATCH] powerpc/powernv/pci: remove dead code from !CONFIG_EEH

From: Daniel Axtens <dja@axtens.net>
To: Nick Desaulniers <ndesaulniers@google.com>,
	Michael Ellerman <mpe@ellerman.id.au>
Cc: Nick Desaulniers <ndesaulniers@google.com>,
	Nathan Chancellor <nathan@kernel.org>,
	Joe Perches <joe@perches.com>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Paul Mackerras <paulus@samba.org>,
	Oliver O'Halloran <oohall@gmail.com>,
	Alexey Kardashevskiy <aik@ozlabs.ru>,
	linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] powerpc/powernv/pci: remove dead code from !CONFIG_EEH
Date: Fri, 23 Apr 2021 09:09:12 +1000	[thread overview]
Message-ID: <87lf99zzl3.fsf@dja-thinkpad.axtens.net> (raw)
In-Reply-To: <20210422195405.4053917-1-ndesaulniers@google.com>

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