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Date: Fri, 8 Jan 2016 23:18:06 +0000
From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: Doug Anderson <dianders@chromium.org>
Cc: Robin Murphy <robin.murphy@arm.com>, Tomasz Figa <tfiga@chromium.org>,
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Subject: Re: [PATCH v4 2/3] common: DMA-mapping: add DMA_ATTR_NOHUGEPAGE
 attribute
Message-ID: <20160108231806.GP19062@n2100.arm.linux.org.uk>
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On Fri, Jan 08, 2016 at 03:05:13PM -0800, Doug Anderson wrote:
> 1. I have to go and touch all existing DMA-mapping code to set
> DMA_ATTR_HUGE_PAGE.  That will be a big patchset and touch more code,
> making it more likely to break something.
...

Indeed, I was actually thinking of a positive "prefer/only use/force
smaller pages" thing rather than "allow huge pages" as a way to get
rid of the "no huge pages" negative as a way to get around that.
It has the same meaning when set as DMA_ATTR_NO_HUGE_PAGE but
avoids the problem of wondering what

	!dma_get_attr(DMA_ATTR_NO_HUGE_PAGE, attrs)

means.

I wasn't thinking of DMA_ATTR_HUGE_PAGE as that would certainly be
wrong when CONFIG_HAVE_DMA_ATTRS is disabled (when dma_get_attr()
always returns 0.)

-- 
RMK's Patch system: http://www.arm.linux.org.uk/developer/patches/
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