On Tue, 20 May 2008, Lennert Buytenhek wrote:

quoted text
> Well.  I just re-tested it a couple more times to be sure, and the
> "hcd->has_tt = 1;" line does make all the difference in the world when
> it comes to getting oopses on plugging in low speed USB devices on this
> board.  So if you don't understand what's going on then I guess I don't
> either.
> 
> 
> > That has_tt flag isn't used anywhere in ehci-hcd (it is only 
> > ever set, never read), and the only place it is used in usbcore is for 
> > adjusting the root hub's device descriptor.
> 
> Maybe this code in drivers/usb/core/hub.c has something to do with
> it?
> 
>         switch (hdev->descriptor.bDeviceProtocol) {
>                 case 0:
>                         break;
>                 case 1:
>                         dev_dbg(hub_dev, "Single TT\n");
>                         hub->tt.hub = hdev;
>                         break;
>                 case 2:
>                         ret = usb_set_interface(hdev, 0, 1);
>                         if (ret == 0) {
>                                 dev_dbg(hub_dev, "TT per port\n");
>                                 hub->tt.multi = 1;
>                         } else
>                                 dev_err(hub_dev, "Using single TT (err %d)\n",
>                                         ret);
>                         hub->tt.hub = hdev;
>                         break;
>                 default:
>                         dev_dbg(hub_dev, "Unrecognized hub protocol %d\n",
>                                 hdev->descriptor.bDeviceProtocol);
>                         break;
>         }

That must be it.  This code base is getting too large to keep in a 
single mind...

Looks like you should submit your patch.

Alan Stern


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