RE: [Linaro-mm-sig] [PATCHv2 1/6] common: DMA-mapping: add DMA_ATTR_NO_KERNEL_MAPPING attribute

Marek Szyprowski
2012-06-14T09:01:30Z

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@samsung.com>
> > Reviewed-by: Kyungmin Park <kyungmin.park@samsung.com>
>
> Looks like a nice little extension to support dma-buf for the common case,
> so:
>
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.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