linux-kernel - RE: [Linaro-mm-sig] [PATCHv2 1/6] common: DMA-mapping: add DMA_ATTR_NO_KERNEL

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Date:	Thu, 14 Jun 2012 11:01:11 +0200
From:	Marek Szyprowski <m.szyprowski@...sung.com>
To:	'Daniel Vetter' <daniel@...ll.ch>
Cc:	linux-arm-kernel@...ts.infradead.org,
	linaro-mm-sig@...ts.linaro.org, linux-mm@...ck.org,
	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
	'Abhinav Kochhar' <abhinav.k@...sung.com>,
	'Russell King - ARM Linux' <linux@....linux.org.uk>,
	'Arnd Bergmann' <arnd@...db.de>,
	'Konrad Rzeszutek Wilk' <konrad.wilk@...cle.com>,
	'Benjamin Herrenschmidt' <benh@...nel.crashing.org>,
	'Kyungmin Park' <kyungmin.park@...sung.com>,
	'Subash Patel' <subash.ramaswamy@...aro.org>
Subject: RE: [Linaro-mm-sig] [PATCHv2 1/6] common: DMA-mapping: add
 DMA_ATTR_NO_KERNEL_MAPPING attribute

Hello,

On Wednesday, June 13, 2012 8:52 PM Daniel Vetter wrote:

> On Wed, Jun 13, 2012 at 01:50:13PM +0200, Marek Szyprowski wrote:
> > This patch adds DMA_ATTR_NO_KERNEL_MAPPING attribute which lets the
> > platform to avoid creating a kernel virtual mapping for the allocated
> > buffer. On some architectures creating such mapping is non-trivial task
> > and consumes very limited resources (like kernel virtual address space
> > or dma consistent address space). Buffers allocated with this attribute
> > can be only passed to user space by calling dma_mmap_attrs().
> >
> > Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
> > Reviewed-by: Kyungmin Park <kyungmin.park@...sung.com>
> 
> Looks like a nice little extension to support dma-buf for the common case,
> so:
> 
> Reviewed-by: Daniel Vetter <daniel.vetter@...ll.ch>
> 
> One question is whether we should go right ahead and add kmap support for
> this, too (with a default implementation that simply returns a pointer to
> the coherent&contigous dma mem), but I guess that can wait until a
> use-case pops up.

I will wait with this until there will be real use cases. Let's get the
patch into mainline first.

Best regards
-- 
Marek Szyprowski
Samsung Poland R&D Center


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