On Thu, Dec 23, 2010 at 11:58:08AM +0100, Marek Szyprowski wrote: > Actually this contiguous memory allocator is a better replacement for > alloc_pages() which is used by dma_alloc_coherent(). It is a generic > framework that is not tied only to ARM architecture. ... which is open to abuse. What I'm trying to find out is - if it can't be used for DMA, what is it to be used for? Or are we inventing an everything-but-ARM framework? > > In other words, do we _actually_ have a use for this which doesn't > > involve doing something like allocating 32MB of memory from it, > > remapping it so that it's DMA coherent, and then performing DMA > > on the resulting buffer? > > This is an arm specific problem, also related to dma_alloc_coherent() > allocator. To be 100% conformant with ARM specification we would > probably need to unmap all pages used by the dma_coherent allocator > from the LOW MEM area. This is doable, but completely not related > to the CMA and this patch series. You've already been told why we can't unmap pages from the kernel direct mapping. Okay, so I'm just going to assume that CMA has _no_ _business_ being used on ARM, and is not something that should interest anyone in the ARM community. -- 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/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>