On Thu, Jul 18, 2019 at 3:08 AM Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote: > > This and the previous one seem very much duplicated boilerplate > code. So yes, there is some duplicate boilerplate between the system and cma heaps particularly in the allocation function, where we allocate and set up the helper buffer structure, allocate the pages, then create and export the dmabuf. I took a pass at trying to minimize some of this earlier, but those efforts ended up adding helper functions that take a ton of arguments, and had some trouble properly handling error paths without leaking memory, so I left it as is. I'll try to take another pass myself but if you have specific suggestions for improving here, I'd be happy to try them. > Why can't just normal branches for allocating and freeing > normal pages vs cma? We even have an existing helper for that > with dma_alloc_contiguous(). Apologies, I'm not sure I'm understanding your suggestion here. dma_alloc_contiguous() does have some interesting optimizations (avoiding allocating single page from cma), though its focus on default area vs specific device area doesn't quite match up the usage model for dma heaps. Instead of allocating memory for a single device, we want to be able to allow userland, for a given usage mode, to be able to allocate a dmabuf from a specific heap of memory which will satisfy the usage mode for that buffer pipeline (across multiple devices). Now, indeed, the system and cma heaps in this patchset are a bit simple/trivial (though useful with my devices that require contiguous buffers for the display driver), but more complex ION heaps have traditionally stayed out of tree in vendor code, in many cases making incompatible tweaks to the ION core dmabuf exporter logic. That's why dmabuf heaps is trying to destage ION in a way that allows heaps to implement their exporter logic themselves, so we can start pulling those more complicated heaps out of their vendor hidey-holes and get some proper upstream review. But I suspect I just am confused as to what your suggesting. Maybe could you expand a bit? Apologies for being a bit dense. Thanks again for the input! -john _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
