On Tue, 27 Jul 2010 14:45:58 +0200
Marek Szyprowski [off-list ref] wrote:

quoted

How does one obtain the CPU address of this memory in order for the CPU
to access it?  

Right, we did not cover such case. In CMA approach we tried to separate
memory allocation from the memory mapping into user/kernel space. Mapping
a buffer is much more complicated process that cannot be handled in a
generic way, so we decided to leave this for the device drivers. Usually
video processing devices also don't need in-kernel mapping for such
buffers at all.

Still...that *is* why I suggested an interface which would return both
the DMA address and a kernel-space virtual address, just like the DMA
API does...  Either that, or just return the void * kernel address and
let drivers do the DMA mapping themselves.  Returning only the
dma_addr_t address will make the interface difficult to use in many
situations.

jon