Hello, On Friday, June 24, 2011 5:52 PM Arnd Bergmann wrote: > 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@xxxxxxxxxxx> > > Signed-off-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx> > > Yes, I think that is good, but the change needs to be done atomically > across all architectures. Yes, I'm aware of this and I will include such changes in the next version of my patches. > 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. Right, this should be quite simple. I will also add DMA_ATTR_NON_COHERENT attribute for implementing dma_alloc_noncoherent() call. > 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? IMHO it will be better to hide the CMA from the drivers. Memory allocated from CMA doesn't really differ from the one allocated by dma_alloc_coherent() (which internally use alloc_pages()), so I really see no reason for adding additional attribute for it. Best regards -- Marek Szyprowski Samsung Poland R&D Center -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>