Hello,

On Sunday, December 11, 2011 11:46 PM Stephen Rothwell wrote:

On Fri, 09 Dec 2011 17:39:56 +0100 Marek Szyprowski [off-list ref] wrote:

quoted

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

To give everyone some chance, you should come up with a transition plan
rather than this "attempt to fix everyone at once" approach.  You could
(for example) just add the new methods now and only remove them in the
following merge window when all the architectures have had a chance to
migrate.

And, in fact, (as I presume you know) this patch just breaks everyone
with no attempt to cope.

Yes, I know that. Next version will include correct fix for this issue as
well as adjustments for other architectures. I was asked to post a current
version of DMA-mapping & IOMMU integration patch rebased on the latest kernel
and I wanted to this before going for holidays to let others to work with the
latest version.

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