From: Greg KH > On Mon, Jan 27, 2014 at 04:06:22PM +0000, David Laight wrote: > > Many of the net/usb ethernet drivers (including common ones like > > the smsc95xx) will fail to transmit all packet length properly > > when connected to a USB3 port (ie using the xhci driver). > > That's odd, as I've never had a problem with my USB 3.0 ethernet device > (sorry, don't remember what driver it uses), and I stress it all the > time. If it is the ax88179_178a driver then it carefully pads packets that are multiples of the message size. > I've also run two different USB 2 ethernet devices on xhci with no > issues at all, so perhaps the "many" statement might not be true? Dunno, quite a few will send down requests with URB_SEND_SERO set. Whether this causes a problem depends on exactly how the ethernet packets are encapsulated in usb ones. The ax88179_178a hardware gets very confused if you fail to send a ZLP - which it why it uses the 'bodge' in usbnet to append a byte. > > The underlying problem is that they assume the host controller > > will honour the URB_ZERO_PACKET flag - which usbnet sets because > > they specify FLAG_SEND_ZLP. > > > > However no one has ever added support for URB_ZERO_PACKET to > > the xhci driver - so packets that need padding (probably 512 > > bytes after any header is added) will not be sent correctly > > and may have very adverse effects on the usb target. > > Really? How has things been working so well up to now without this > support? Doesn't the hardware automatically add this padding with no > explicit need for the xhci driver to do something? Nope - things must work by luck! Try ping -n $((512-0x32)) on an smsc95xx card - it should need a ZLP. > > I don't think anything significant has changed (in the main kernel > > sources) since I wrote the patch. > > Then resubmit it, don't post links to it on the web, there's nothing we > can do with them, sorry. I've resubmitted it as a v3 patch (to linux-usb) in small steps so that the changes are easier to verify. The final result is slightly different as I spotted a couple of minor issues when re-reading the final version. Mostly due to another 2 months of looking at this code. David -- 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
