On Monday 20 June 2011, Marek Szyprowski wrote:

Introduce new alloc/free/mmap methods that take attributes argument.
alloc/free_coherent can be implemented on top of the new alloc/free
calls with NULL attributes. dma_alloc_non_coherent can be implemented
using DMA_ATTR_NONCOHERENT attribute, dma_alloc_writecombine can also
use separate DMA_ATTR_WRITECOMBINE attribute. This way the drivers will
get more generic, platform independent way of allocating dma memory
buffers with specific parameters.

One more attribute can be usefull: DMA_ATTR_NOKERNELVADDR. Buffers with
such attribute will not have valid kernel virtual address. They might be
usefull for drivers that only exports the DMA buffers to userspace (like
for example V4L2 or ALSA).

mmap method is introduced to let the drivers create a user space mapping
for a DMA buffer in generic, architecture independent way.

TODO: update all dma_map_ops clients for all architectures

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>

Yes, I think that is good, but the change needs to be done atomically
across all architectures. This should be easy enough as I believe
all other architectures that use dma_map_ops don't even require
dma_alloc_noncoherent but just define it to dma_alloc_coherent
because they have only coherent memory in regular device drivers.

On a related note, do you plan to make the CMA work use this
transparently, or do you want to have a DMA_ATTR_LARGE or
DMA_ATTR_CONTIGUOUS for CMA?

	Arnd