linux-kernel - Re: [PATCH 1/3 v3] dma: document dma_{un}map_{single|sg}

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Message-ID: <20080320003258.GM1843@sgi.com>
Date:	Wed, 19 Mar 2008 17:32:58 -0700
From:	akepner@....com
To:	Michael Ellerman <michael@...erman.id.au>
Cc:	James Bottomley <James.Bottomley@...senPartnership.com>,
	Grant Grundler <grundler@...isc-linux.org>,
	Tony Luck <tony.luck@...el.com>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Jes Sorensen <jes@....com>,
	Randy Dunlap <randy.dunlap@...cle.com>,
	Roland Dreier <rdreier@...co.com>,
	David Miller <davem@...emloft.net>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	linux-kernel@...r.kernel.org, Mark Nelson <mdnelson@....ibm.com>
Subject: Re: [PATCH 1/3 v3] dma: document dma_{un}map_{single|sg}_attrs() interface

On Fri, Mar 14, 2008 at 03:30:29PM +1100, Michael Ellerman wrote:
> 
> I like this better, sorry to keep nitpicking, but just a few comments
> below ..

Comments are appreciated.

> ...
> You say a "DMA to a memory region with the DMA_ATTR_BARRIER attribute
> forces all pending DMA writes to complete". Does it force _all_ DMA
> writes to complete, or just writes to the region, or just writes coming
> from devices? What if something is writing to a device?
>

Yes, forces all writes to complete (as others have already said).

 
> Does DMA_ATTR_BARRIER have any effect on reads?
> 

No, changed the name to DMA_ATTR_WRITE_BARRIER to emphasize this.

-- 
Arthur

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