On Mon, Jan 21, 2019 at 04:33:27PM +0100, Ard Biesheuvel wrote: > On Mon, 21 Jan 2019 at 16:07, Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote: > > > > > +#include <linux/dma-noncoherent.h> > > > > This header is not for usage in device drivers, but purely for > > dma-mapping implementations! > > > > Is that documented anywhere? I'll add big fat comments. But the fact that nothing is exported there should be a fairly big hint. > > And even if something like this was valid to do, it would have to be > > a core function with an arch hook, and not hidden in a random driver. > > Why would it not be valid to do? Is it wrong for a driver to be aware > of whether a device is cache coherent or not? > > And in case it isn't, do you have an alternative suggestion on how to > fix this mess? For the write combine mappings we need a proper core API how instances can advertise the support. One thing I want to do fairly soon is error checking of the attrs argument to dma_alloc_attrs - so if you pass in something unsupported it will give you back an error. It seems that isn't quite enough for the drm use case, so we might also need a way to query these features, but that really has to go through the usual dma layer abstraction as well and not hacked together in a driver based on an eduacted guestimate. _______________________________________________ amd-gfx mailing list amd-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/amd-gfx
