On Mon, 2011-02-07 at 09:13 -0600, Timur Tabi wrote: > > This behavior is modified if you specify a restricted DMA > > mask for the device. In this case, dma_alloc_coherent > > will force GFP_DMA on your behalf (on PowerPC). > > Isn't it required for all callers of dma_alloc_coherent to specify a > mask (via > dma_set_mask) first?
GFP_DMA historically means ISA DMA memory on x86 :-) Other platforms had different "use" for it but basically it's old style drivers. The problem with dma_set_mask() is that there's no way without an iommu that the implementation of dma_alloc_coherent() can satisfy arbitrary masks since you don't control where the page allocator gets you the pages from ... unless you have zones. That's what ZONE_DMA and ZONE_DMA32 are for. Cheers, Ben. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
