From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@infradead.org>
Date: Fri, 01 Jul 2011 13:47:05 +0000
Subject: Re: [PATCH 00/10] Enhance /dev/mem to allow read/write of arbitrary
Message-Id: <20110701134705.GA6175@infradead.org>
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References: <201106171038.25988.ptesarik@suse.cz>
	<20110617093032.GA19235@elte.hu>
	<201106291106.00070.ptesarik@suse.cz>
	<20110701125802.GE12605@elte.hu>
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To: linux-arm-kernel@lists.infradead.org

On Fri, Jul 01, 2011 at 02:58:02PM +0200, Ingo Molnar wrote:
> So what was not mentioned in your series, what is *your* motivation 
> and your usecase? Enabling closed-source userspace drivers? Enabling 
> the crash utility?

He stated it pretty clearly in the thread, it's the crash utility.

> 
> If the former then shame on you, if the latter then how do you 
> explain that distros appear to disable the RAM aspect of /dev/mem:
> 
>  $ grep DEVMEM $(rpm -ql kernel-2.6.38-0.rc7.git2.3.fc16.x86_64 | grep config-2.6 )
>  CONFIG_STRICT_DEVMEM=y
> 
> So the crash utility use-case does not work on unpatched, default 
> kernels, right?

Not if you have highmem.  That's why Redhat or Fedora to quote your
example patch in the /dev/crash driver, which totally defeats the
CONFIG_STRICT_DEVMEM setting.  But apparently it's good enough that no
one either noticed or at least doesn't care.