On Tue, 2008-09-30 at 17:21 +1000, Benjamin Herrenschmidt wrote: > On Mon, 2008-09-29 at 10:26 -0700, Remi Machet wrote: > > > > I also removed the HIGHMEM support in dma_sync since memory allocated for > > DMA transfer should always be in ZONE_DMA (ie not in ZONE_HIGHMEM). > > While I like the idea of simplifying that stuff, the above sentence is > incorrect unfortunately. > > ZONE_DMA is an artifact of x86 ISA DMA limitations. You -will- get > request for mapping pages for DMA that have been allocated within > different zones (notably highmem). > > The problem with highmem is that whether you can or not DMA to/from > highmem is somewhat unclear, drivers set flags individually in various > layers to allow it, which is definitely not the right place to do so. So > while it would be nice to think we never will, in practice, we do. >
Yes, I realized that looking at the changes Becky's made. I will put back the highmem support when merging my changes with those. Thanks! Remi _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev