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

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Date:	Tue, 12 Feb 2013 22:36:37 +0000
From:	Arnd Bergmann <arnd@...db.de>
To:	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>
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

On Tuesday 12 February 2013, Thomas Petazzoni wrote:
> > 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.

That is correct.

> 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.

Yes, the pcim_ functions are useful in principle, but it falls back
to the __pci_ioport_map() for IORESOURCE_IO, and that needs to
return an error if CONFIG_HAS_IOPORT is not set.
I think it would be correct if you add this hunk:

diff --git a/lib/pci_iomap.c b/lib/pci_iomap.c
index 0d83ea8..f9b6387 100644
--- a/lib/pci_iomap.c
+++ b/lib/pci_iomap.c
@@ -33,7 +33,7 @@ void __iomem *pci_iomap(struct pci_dev *dev, int bar, unsigned long maxlen)
                return NULL;
        if (maxlen && len > maxlen)
                len = maxlen;
-       if (flags & IORESOURCE_IO)
+       if (IS_ENABLED(CONFIG_HAS_IOPORT) && (flags & IORESOURCE_IO))
                return __pci_ioport_map(dev, start, len);
        if (flags & IORESOURCE_MEM) {
                if (flags & IORESOURCE_CACHEABLE)

in order to prevent a link error when CONFIG_HAS_IOPORT is unset.

	Arnd
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