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Subject: Re: [BUILD FAILURE 01/04] Next June 04:PPC64 randconfig
	[drivers/staging/comedi/drivers.o]
From: Subrata Modak <subrata@linux.vnet.ibm.com>
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Date: Sun, 07 Jun 2009 20:06:45 +0530
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Cc: sachinp@linux.vnet.ibm.com, sfr@canb.auug.org.au, Greg KH <greg@kroah.com>,
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On Sat, 2009-06-06 at 09:36 -0400, Frank Mori Hess wrote:
> On Saturday 06 June 2009, Greg KH wrote:
> > Frank and Ian, any thoughts about the vmap call in the
> > comedi_buf_alloc() call?  Why is it using PAGE_KERNEL_NOCACHE, and what
> > is the prealloc_buf buffer used for?
> 
> It is a circular buffer used to hold data streaming either to or from a 
> board (for example when producing an analog output waveform).  Reads and 
> writes to the device files read/write to the circular buffer, plus a few 
> drivers do dma directly to/from it.  I personally don't have a problem 
> with requiring drivers to have their own dma buffers and making them copy 
> data between their private dma buffers and the main circular buffer.  I 
> guess the original design wanted to support zero-copy dma.

Great to hear that. How about a patch that solves my build problem on
PPC64(the problem seems to be existing for long) ? 

Regards--
Subrata

>