I can't think of any use case where you would want sub-page cache flushing. This isn't a feature I plan on supporting. Generically we should probably extend the dirty map so that you can have page wise flushing of the carveout allocations. Again that's something I can implement when I get a chance, or you can submit a patch to me that adds it. The code in ion_system_heap.c that does the same can serve as an example. The current implementation of the carveout head doesn't support cached mappings at all -- it should print an error if you try to create one.
Rebecca
Thanks Rebecca,
Still not sure whether we need specific dma_data_direction direction. Currently DMA_BIDIRECTIONAL is used by default, and no interface could transfer direction.
Besides, which code base should be used if want to submit patch. How about common.git, android-3.4 branch?
Thanks