linux-kernel - Re: [PATCH 1/2] asm-generic: add MMU variants of io.h functions

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Date:	Sat, 02 Jul 2011 18:47:30 +0200
From:	Jonas Bonn <jonas@...thpole.se>
To:	Mike Frysinger <vapier@...too.org>
Cc:	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	liqin.chen@...plusct.com, gxt@...c.pku.edu.cn
Subject: Re: [PATCH 1/2] asm-generic: add MMU variants of io.h functions


On Sat, 2011-07-02 at 12:38 -0400, Mike Frysinger wrote:
> On Sat, Jul 2, 2011 at 11:53, Jonas Bonn wrote:
> > Some of the implementations, in particular the ioremap variants, in
> > asm-generic/io.h are for systems with an MMU.
> 
> do you mean "without an MMU" ?

Yes, of course... that's supposed to be _without_ an MMU.

> 
> > +#ifdef CONFIG_MMU
> > +#define xlate_dev_mem_ptr(p)   __va(p)
> > +#else
> >  #define xlate_dev_mem_ptr(p)   ((void *) (p))
> > +#endif
> 
> i wonder if we could do:
> #ifndef __va
> #define __va(p) ((void *)(p))
> #endif
> #define xlate_dev_mem_ptr(p)   __va(p)
> -mike

This seems to introduce an artificial definition of a "virtual" address
for systems without an MMU, which strikes me as a bit odd.  If this is
what people prefer, that's fine... I think I prefer the former variant,
though.

/Jonas

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