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Re: [PATCH 1/3] lib: add NO_GENERIC_PCI_IOPORT_MAP

To: "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [PATCH 1/3] lib: add NO_GENERIC_PCI_IOPORT_MAP
From: Arnd Bergmann <arnd@arndb.de>
Date: Mon, 30 Jan 2012 20:04:32 +0000
Cc: Kevin Cernekee <cernekee@gmail.com>, Ralf Baechle <ralf@linux-mips.org>, Paul Mundt <lethal@linux-sh.org>, Jesse Barnes <jbarnes@virtuousgeek.org>, Myron Stowe <myron.stowe@redhat.com>, Paul Gortmaker <paul.gortmaker@windriver.com>, Lucas De Marchi <lucas.demarchi@profusion.mobi>, Dmitry Kasatkin <dmitry.kasatkin@intel.com>, James Morris <jmorris@namei.org>, "John W. Linville" <linville@tuxdriver.com>, Michael Witten <mfwitten@gmail.com>, linux-mips@linux-mips.org, linux-kernel@vger.kernel.org, linux-sh@vger.kernel.org, linux-arch@vger.kernel.org
In-reply-to: <20120130161818.GA9345@redhat.com>
References: <cover.1327877053.git.mst@redhat.com> <201201301551.46907.arnd@arndb.de> <20120130161818.GA9345@redhat.com>
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On Monday 30 January 2012, Michael S. Tsirkin wrote:
> > 
> > +/*
> > + * Create a virtual mapping cookie for a port on a given PCI device.
> > + * Do not call this directly, it exists to make it easier for architectures
> > + * to override.
> > + */
> > +#ifdef CONFIG_NO_GENERIC_PCI_IOPORT_MAP
> > +extern void __iomem *__pci_ioport_map(struct pci_dev *dev, unsigned long 
> > port,
> > +                                     unsigned int nr);
> > +#else
> > +static inline void __iomem *__pci_ioport_map(struct pci_dev *dev,
> > +                              unsigned long port, unsigned int nr)
> > +{
> > +       return ioport_map(port, nr);
> > +}
> > +#endif
> > 
> >       Arnd
> 
> It would be nicer in that it would
> make the kernel a bit smaller for generic architectures
> but this would need to go into a separate header:
> it depends on io.h and io.h depends on pci_iomap.h.

Adding extra dependencies is not good here, I agree.
Maybe  a better solution is to use a macro instead of an inline
function then:

#define  __pci_ioport_map(dev, port, nr) ioport_map(port, nr)

In general, macros should be avoided, but I think it's the
best tradeoff in this case.

        Arnd

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