linux-kernel - Re: [RFC] dma: passing "attributes" to dma_map

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Date:	Tue, 18 Dec 2007 17:50:42 +0100
From:	Stefan Richter <stefanr@...6.in-berlin.de>
To:	akepner@....com
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	grundler@...isc-linux.org, jbarnes@...tuousgeek.org, jes@....com,
	randy.dunlap@...cle.com, rdreier@...co.com,
	James.Bottomley@...eleye.com, davem@...emloft.net,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC] dma: passing "attributes" to dma_map_* routines

akepner@....com wrote:
> Waaay back in October I sent some patches for passing additional 
> attributes to the dma_map_* routines:
> 
> http://marc.info/?l=linux-kernel&m=119137949604365&w=2

Do I understand correctly?:  A device and the CPUs communicate via two
separate memory areas:  A data buffer and a status FIFO.  The NUMA
interconnect may reorder accesses of the device to the areas.  (Write
accesses?  Read accesses?  Both?)

To ensure synchronization between device and CPUs, you want to mark a
memory area which is to be dma-mapped with a flag which says:  "Writes
to the memory region will cause in-flight DMA to be flushed".  Whose
writes?  A write access from the device or a write access from a CPU?
-- 
Stefan Richter
-=====-=-=== ==-- =--=-
http://arcgraph.de/sr/
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