On Fri, Aug 03, 2018 at 04:05:35PM -0400, Tony Battersby wrote: > For v3 of the patchset, I was also considering to add a note to the > kernel-doc comments for dma_pool_create() to use dma_alloc_coherent() > directly instead of a dma pool if the driver intends to allow userspace > to mmap() the returned pages, due to the new use of the _mapcount union > in struct page. Would you consider that useful information or pointless > trivia? If userspace is going to map the pages, it's going to expose other things to userspace than the dma pages. I'd suggest they not do this; they should do their own sub-allocation which only exposes to an individual task the data they're sure is OK for each task to see.
