On Mon, Dec 05, 2016 at 09:40:38AM -0800, Dan Williams wrote: > > If it is kernel only with physical addresess we don't need a uAPI for > > it, so I'm not sure #1 is at all related to iopmem. > > > > Most people who want #1 probably can just mmap > > /sys/../pci/../resourceX to get a user handle to it, or pass around > > __iomem pointers in the kernel. This has been asked for before with > > RDMA. > > > > I'm still not really clear what iopmem is for, or why DAX should ever > > be involved in this.. > > Right, by default remap_pfn_range() does not establish DMA capable > mappings. You can think of iopmem as remap_pfn_range() converted to > use devm_memremap_pages(). Given the extra constraints of > devm_memremap_pages() it seems reasonable to have those DMA capable > mappings be optionally established via a separate driver. Except the iopmem driver claims the PCI ID, and presents a block interface which is really *NOT* what people who have asked for this in the past have wanted. IIRC it was embedded stuff eg RDMA video directly out of a capture card or a similar kind of thinking. It is a good point about devm_memremap_pages limitations, but maybe that just says to create a /sys/.../resource_dmableX ? Or is there some reason why people want a filesystem on top of BAR memory? That does not seem to have been covered yet.. Jason -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
