linux-kernel - Re: [PATCH v6 1/3] Fix ioport_map() for !CONFIG_GENERIC

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Date:	Fri, 14 Mar 2014 12:54:17 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	"Russell King - ARM Linux" <linux@....linux.org.uk>,
	"Uwe Kleine-König" 
	<u.kleine-koenig@...gutronix.de>
Cc:	Liviu Dudau <Liviu.Dudau@....com>,
	"linux-pci" <linux-pci@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....com>,
	"linaro-kernel" <linaro-kernel@...ts.linaro.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Tanmay Inamdar <tinamdar@....com>,
	LAKML <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v6 1/3] Fix ioport_map() for !CONFIG_GENERIC_IOMAP cases.

On Friday 07 March 2014, Russell King - ARM Linux wrote:
> On Fri, Mar 07, 2014 at 01:37:38AM +0100, Arnd Bergmann wrote:
> > On Thursday 06 March 2014, Russell King - ARM Linux wrote:

> > > arch/microblaze/include/asm/io.h:/* from asm-generic/io.h */
> > 
> > PCI_IOBASE=0, IO_SPACE_LIMIT=0xffffffff, so no change.
> 
> Seems to define _IO_BASE not PCI_IOBASE.

It gets the implicit PCI_IOBASE from asm-generic/io.h at the moment.

> > 
> > PCI_IOBASE=0, IO_SPACE_LIMIT=0xffffffff, so no change.
> 
> Doesn't appear to define PCI_IOBASE.

Same here.

> > For most of these, I assume we actually want to remove support
> > for inb/outb as they don't support I/O space accesses. The other
> > ones look correct to me.
> 
> Right, so:
> 
> #ifdef CONFIG_HAS_IOPORT
> #ifndef CONFIG_GENERIC_IOMAP
> static inline void __iomem *ioport_map(unsigned long port, unsigned int nr)
> {
>         return (void __iomem *) port;
> }
> 
> changing that to include PCI_IOBASE in there will result in a build
> failure if the C compiler sees that.  In other words, when HAS_IOPORT=y
> and GENERIC_IOMAP=n.
> 
> HAS_IOPORT is set when HAS_IOMEM is also set and NO_IOPORT unset.
> 
> It looks to me like blackfin doesn't set NO_IOPORT nor NO_IOMEM, so
> this would have HAS_IOPORT set, and from what I can see doesn't set
> GENERIC_IOMAP.  So, this change probably breaks blackfin.

I also see the same thing that Liviu mentioned, that PCI_IOBASE=0
is always provided by asm-generic/io.h if not set otherwise.

On a related topic, Uwe Kleine-König has submitted a patch to
rename CONFIG_HAS_IOPORT to CONFIG_HAS_IOPORT_MAP to clarify what
it does, and to allow us to add a new CONFIG_HAS_IOPORT option
that will let us remove all the I/O port handling code for
architectures that don't have any I/O access method.

	Arnd
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