Hi Christoph and everyone, On Fri, Aug 31, 2018 at 3:51 PM Tomasz Figa <tfiga@xxxxxxxxxxxx> wrote: > > On Fri, Aug 31, 2018 at 2:50 PM Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote: > > > > On Thu, Aug 30, 2018 at 07:11:35PM -0300, Ezequiel Garcia wrote: > > > On Thu, 2018-08-30 at 10:58 -0700, Christoph Hellwig wrote: > > > > Please don't introduce new DMA_ATTR_NON_CONSISTENT users, it is > > > > a rather horrible interface, and I plan to kill it off rather sooner > > > > than later. I plan to post some patches for a better interface > > > > that can reuse the normal dma_sync_single_* interfaces for ownership > > > > transfers. I can happily include usb in that initial patch set based > > > > on your work here if that helps. > > > > > > Please do. Until we have proper allocators that go thru the DMA API, > > > drivers will have to kmalloc the USB transfer buffers, and have > > > streaming mappings. Which in turns mean not using IOMMU or CMA. > > > > dma_map_page will of course use the iommu. > > Sure, dma_map*() will, but using kmalloc() defeats (half of) the > purpose of it, since contiguous memory would be allocated > unnecessarily, risking failures due to fragmentation. Have we reached a conclusion here? It sounds like it's a quite significant problem, at least for some of the camera (media) devices over there and there are people interested in solving it, so all we need here is a conclusion on how to do it. :) Best regards, Tomasz
