Hello, On Tuesday, July 27, 2010 2:59 PM Jonathan Corbet wrote: > On Tue, 27 Jul 2010 14:45:58 +0200 > Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> wrote: > > > > 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. As I said, drivers usually don't need in-kernel mapping for video buffers. Is there really a need for creating such mapping? Best regards -- Marek Szyprowski Samsung Poland R&D Center -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>