From: Arnd Bergmann <arnd@arndb.de>
To: Guan Xuetao <gxt@mprc.pku.edu.cn>
Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
'Greg KH' <greg@kroah.com>
Subject: Re: [PATCH 09/12] unicore32 machine related files: hardware registers
Date: Sat, 26 Feb 2011 14:16:09 +0100 [thread overview]
Message-ID: <201102261416.10050.arnd@arndb.de> (raw)
In-Reply-To: <010f01cbd5b0$09980830$1cc81890$@mprc.pku.edu.cn>
On Saturday 26 February 2011, Guan Xuetao wrote:
> > > #ifndef __ASSEMBLY__
> > >
> > > -# define __REG(x) (*((volatile unsigned long *)io_p2v(x)))
> > > -# define __PREG(x) (io_v2p((unsigned long)&(x)))
> > > +# define __REG(x) (void __iomem *)io_p2v(x)
> >
> > The patch looks correct, but if you make the the definition for
> > PKUNITY_MMIO_BASE contain the cast to (void __iomem *), you no
> > longer need another cast.
>
> Because the io_p2v(x) calculate x and PKUNITY_IOSPACE_BASE,
> all registers should be added with (void __iomem *).
> So I prefer to remain the previous patch.
The problem with the definition of io_p2v is that it gives you
an type that is impossible to use correctly, except in assembly
code. Linux assumes that MMIO registers in virtual space
are __iomem pointers, and we like that to be consistent.
If you have a function that returns a virtual address, it should
really have the same type as any other function that uses a virtual
address.
Arnd
next prev parent reply other threads:[~2011-02-26 13:16 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-16 7:51 [PATCH 09/12] unicore32 machine related files: hardware registers Guan Xuetao
2011-02-17 16:59 ` Arnd Bergmann
2011-02-18 9:52 ` Guan Xuetao
2011-02-18 10:42 ` Arnd Bergmann
2011-02-22 14:09 ` Guan Xuetao
2011-02-22 14:19 ` Arnd Bergmann
2011-02-22 14:19 ` Arnd Bergmann
2011-02-26 12:23 ` Guan Xuetao
2011-02-26 13:16 ` Arnd Bergmann [this message]
2011-02-27 3:35 ` Guan Xuetao
2011-02-27 17:15 ` Arnd Bergmann
2011-02-27 17:15 ` Arnd Bergmann
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