On Mon, Nov 16, 2015 at 03:22:06PM -0500, Alan Stern wrote: > In other words, you're suggesting we do this: > > Check that userspace requested zerocopy (otherwise the user > program might try to access other data stored in the same cache > lines as the buffer while the I/O is in progres); > > Call get_user_pages (or get_user_pages_fast? -- it's not clear > which should be used) for this buffer; > > Use the array of pages returned by that routine to populate > a scatter-gather list (sg_alloc_table_from_pages); > > Pass that list to dma_map_sg. > > Is that right?
Yes. > Does dma_map_sg check the page addresses against the DMA mask and > automatically create a bounce buffer, or do we have to do that > manually? Documentation/DMA-API-HOWTO.txt doesn't discuss this. You need to do this manually. -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
