linux-kernel - Re: [PATCH 05/32] lib: devres: don't enclose pcim_*() functions in CONFIG_HAS

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Message-ID: <20130212195816.6e34b3ce@skate>
Date:	Tue, 12 Feb 2013 19:58:16 +0100
From:	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Lior Amsalem <alior@...vell.com>, Andrew Lunn <andrew@...n.ch>,
	"Russell King - ARM Linux" <linux@....linux.org.uk>,
	Jason Cooper <jason@...edaemon.net>,
	Stephen Warren <swarren@...dotorg.org>,
	Thierry Reding <thierry.reding@...onic-design.de>,
	"Eran Ben-Avi" <benavi@...vell.com>,
	Nadav Haklai <nadavh@...vell.com>,
	Maen Suleiman <maen@...vell.com>,
	Shadi Ammouri <shadi@...vell.com>,
	Gregory Clement <gregory.clement@...e-electrons.com>,
	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	Tawfik Bayouk <tawfik@...vell.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Yinghai Lu <yinghai@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 05/32] lib: devres: don't enclose pcim_*() functions in
 CONFIG_HAS_IOPORT

Dear Arnd Bergmann,

On Tue, 12 Feb 2013 18:00:48 +0000, Arnd Bergmann wrote:
> On Tuesday 12 February 2013, Thomas Petazzoni wrote:
> > The pcim_*() functions are used by the libata-sff subsystem, and
> > this subsystem is used for many SATA drivers on ARM platforms that
> > do not necessarily have I/O ports.
> > 
> > Signed-off-by: Thomas Petazzoni
> > <thomas.petazzoni@...e-electrons.com> Cc: Paul Gortmaker
> > <paul.gortmaker@...driver.com> Cc: Jesse Barnes
> > <jbarnes@...tuousgeek.org> Cc: Yinghai Lu <yinghai@...nel.org>
> > Cc: linux-kernel@...r.kernel.org
> 
> Sorry, but this patch is still incorrect.

I know, but the discussion was so huge on the first posting that it was
basically impossible to draw a conclusion out of it.

> Any driver that requires a
> linear mapping of I/O ports to __iomem pointers must depend
> CONFIG_HAS_IOPORT with the current definition of that symbol (as
> mentioned before, we should really rename that to
> CONFIG_HAS_IOPORT_MAP). Having these functions not defined is a
> compile time check that is necessary to ensure that all drivers have
> the correct annotation.

I have the feeling that the problem is more complex than that. My
understanding is that the pcim_iomap_regions() function used by
drivers/ata/libata-sff.c can perfectly be used to map memory BARs, and
not necessarily I/O BARs. Therefore, this driver can perfectly be used
in an architecture where CONFIG_NO_IOPORT is selected.

The thing is that pcim_iomap_regions() transparently allows to remap an
I/O BAR is such a BAR is passed as argument, or a memory BAR if such a
BAR is passed as argument.

Therefore, I continue to believe that the pcim_*() functions are useful
even if the platform doesn't have CONFIG_HAS_IOPORT.

Best regards,

Thomas
-- 
Thomas Petazzoni, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com
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