On Tue, 29 May 2012, Rajeev kumar wrote:
> Just for curiosity,
> I have passed USB1 from this flag and it starts supporting full speed
> device.
>
> When I passed USB2 flag from this and connect a full speed hub, it
> reflect "parent hub has no TT". The print is coming from
>
> /* Set up TT records, if needed */
> if (hdev->tt) {
> udev->tt = hdev->tt;
> udev->ttport = hdev->ttport;
> } else if (udev->speed != USB_SPEED_HIGH
> && hdev->speed == USB_SPEED_HIGH) {
> if (!hub->tt.hub) {
> dev_err(&udev->dev, "parent hub has no TT\n");
> retval = -EINVAL;
> goto fail;
> }
> }
> My debugging says that
> 1. hdev->speed == USB_SPEED_HIGH comparison is true, but why when I am
> attaching a full speed device.
hdev->speed is the speed of the parent hub, not the speed of the
device.
> 2. The print "parent hub has no TT\n" will only come when there is no
> tt.hub. Now this is only possible when hdev->descriptor.bDeviceProtocol
> == 0. Could you please guide me from where this field is getting updated?
It gets set from hcd->has_tt, which your driver must initialize in its
probe or reset routine. There are examples in various source files in
drivers/usb/host.
Alan Stern
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