All of lore.kernel.org
 help / color / mirror / Atom feed
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

  reply	other threads:[~2011-02-26 13:16 UTC|newest]

Thread overview: 15+ 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
2011-02-16  7:51 ` Guan Xuetao
2011-02-17 16:59 ` Arnd Bergmann
2011-02-18  9:52   ` Guan Xuetao
2011-02-18  9:52     ` Guan Xuetao
2011-02-18 10:42     ` Arnd Bergmann
2011-02-22 14:09       ` Guan Xuetao
2011-02-22 14:09         ` Guan Xuetao
2011-02-22 14:19         ` Arnd Bergmann
2011-02-26 12:23           ` Guan Xuetao
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  3:35                 ` Guan Xuetao
2011-02-27 17:15                 ` Arnd Bergmann

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=201102261416.10050.arnd@arndb.de \
    --to=arnd@arndb.de \
    --cc=greg@kroah.com \
    --cc=gxt@mprc.pku.edu.cn \
    --cc=linux-arch@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.