On Tue, 17 Nov 2015, Steinar H. Gunderson wrote: > On Tue, Nov 17, 2015 at 02:13:49PM -0500, Alan Stern wrote: > > But what other way of allocating memory is there? > > For my part, GPU memory versus malloc(). (You can ask OpenGL to permanently > map up a chunk of GPU memory for you into userspace, but you have no > guarantees as of if it's DMA-able. But typical memory from malloc() might.) I don't think there's any reason to expect malloc to provide memory where you need it. Also, since the memory it provides isn't locked, the kernel can move it to any physical address. > It might be overengineering things, though. I'd be fairly happy if I only had > zerocopy in most common situations. (Does xHCI have this 32-bit limitation?) xHCI always uses 64-bit addresses. But many EHCI controllers don't, and only a few of the EHCI platform drivers support 64-bit DMA. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
