On Tue, 17 Nov 2015, Steinar H. Gunderson wrote: > > 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. > > OK, sure. But are systems with USB2 only and more than 4GB of RAM common? > (And will they not increasingly die out, if nothing else as USB3 becomes > commonplace?) I think they're still reasonably common. For example, the computer I'm writing this email on has an xHCI controller, but that controller is connected only to the SuperSpeed bus. The High/Full/Low speed bus is connected to an EHCI controller. And the computer has 8 GB of memory. Over time such things will die out in the desktop world. I'm not so sure about the mobile or embedded worlds, though. Anyway, right now we would like to support as much as possible. 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
