On Thu, Feb 09, 2012 at 03:38:36PM -0500, Alan Stern wrote: > On Thu, 9 Feb 2012, Greg KH wrote: > > > On Thu, Feb 09, 2012 at 09:15:25PM +0100, Olivier DOLE wrote: > > > Hello, > > > > > > I have a question about USB 3.0 and host to host communication through a > > > "standard A" to "standard A" cable. > > > > Not possible at all, on a pure electrical basis. Please read the USB > > specification at www.usb.org for why. > > Actually it _is_ possible in USB-3. That's because unlike USB-2, USB-3 > cables use separate wires for TX+, TX-, RX+, and RX-. An A-to-A cable > simply has the TX+/TX- pair on each side connected to the RX+/RX- pair > on the other side. > > Nevertheless, although such connections are possible, they require > special software to drive them. They are intended for debugging and > other specialized uses; the Linux kernel does not currently support > them. Alan's right. The xHCI spec describes a debug port to connect two hosts together, but a debug port is optional and almost none of the xHCI hosts currently on the market actually have them. Also, as Alan said, there isn't any Linux software to support it. Sarah Sharp -- 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
