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Subject: Re: [PATCH] powerpc/mm: setting mmaped page cache property through
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From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Li Yang <leoli@freescale.com>
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Date: Fri, 04 Dec 2009 13:37:37 +1100
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On Tue, 2009-12-01 at 19:34 +0800, Li Yang wrote:
> The scenario for the second case is to pre-allocate some memory to a
> certain application or device (probably through mem=XXX kernel
> parameter or limit through device tree).  The memory is not known to
> kernel, but fully managed by the application/device.  We need being
> able to map the region cachable for better performance.
> 
> > trying to achieve here ? We can find a solution though it might
> involve
> > a specific driver to handle that memory.
> 
> Right, but what the user to kernel API should be used?  Is it ok to
> use the O_SYNC flag as I previously proposed? 

If it's cachable, why don't you write yourself a little driver that
allocates memory maps it to userspace and provides you with the physical
addresses and problem solved ?

Cheers,
Ben.