linux-kernel - Re: [PATCH 1/2] asm-generic/io.h: provide default ioremap/iounmap for !HAS

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Date:	Wed, 30 Mar 2016 15:51:19 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Rob Herring <robh@...nel.org>
Cc:	Richard Weinberger <richard@....at>,
	Lee Jones <lee.jones@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
	user-mode-linux-devel@...ts.sourceforge.net
Subject: Re: [PATCH 1/2] asm-generic/io.h: provide default ioremap/iounmap for !HAS_IOMEM

On Wednesday 30 March 2016 08:29:45 Rob Herring wrote:
> On Wed, Mar 30, 2016 at 5:03 AM, Arnd Bergmann <arnd@...db.de> wrote:
> > On Wednesday 30 March 2016 10:13:53 Richard Weinberger wrote:
> >>
> >> I fully understand your point of view. COMPILE_TEST is a monster that
> >> can do the heavy lifting for you, but monsters also have claws and fangs.
> >>
> >> Having COMPILE_TEST having depend on !UML works for me. But don't
> >> we have other archs without io mem? At least a few years ago while
> >> porting nandsim to UML I found s390 that lacks of io mem too.
> >
> > s390 gained IOMEM support when they started having PCI attachments.
> 
> I'm confused how s390 defines HAS_IOMEM and includes it from lib/Kconfig though.

Kconfig can define the same symbol multiple times, which is really
confusing. I only checked for NO_IOMEM, which s390 no longer defines,
but I have not checked what actually happens in case of two conflicting
definitions, where the one lib/Kconfig defaults to 'y' and the one in
arch/s390 defaults to CONFIG_PCI.

	Arnd