linux-kernel - Re: [PATCH 1/2] NOMMU: Set BDI capabilities for /dev/mem and /dev/kmem

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Message-Id: <20060829122851.690e5219.akpm@osdl.org>
Date:	Tue, 29 Aug 2006 12:28:51 -0700
From:	Andrew Morton <akpm@...l.org>
To:	David Howells <dhowells@...hat.com>
Cc:	torvalds@...l.org, linux-kernel@...r.kernel.org,
	uclinux-dev@...inux.org
Subject: Re: [PATCH 1/2] NOMMU: Set BDI capabilities for /dev/mem and
 /dev/kmem

On Tue, 29 Aug 2006 19:39:54 +0100
David Howells <dhowells@...hat.com> wrote:

> Andrew Morton <akpm@...l.org> wrote:
> 
> > #else
> > #define get_unmapped_area_mem NULL
> > #endif
> 
> Blech.
> 
> Of course, I could just declare the new symbols weak, and stick
> get_unmapped_area_mem() and mem_bdi in their own file which would be
> conditional on !CONFIG_MMU.

Or you could use the approach I suggested, like wot everyone else does.

> > This changes behaviour, doesn't it?
> 
> Yes.
> 
> >  But only for !CONFIG_MMU kernels?
> 
> Yes.  For the moment, nothing in MMU world actually looks at these
> capabilities, though perhaps they should.
> 
> > Perhaps some additional commentary around this is needed.
> 
> Perhaps... or perhaps it should have different capabilities if there's an MMU.
> 
> Is doing a private mapping of /dev/mem a valid thing to do anyway, even if
> there is an MMU?

It would be strange, I guess.  But the important thing is to not change
behaviour.
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