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    SubjectRe: [PATCH v12 7/8] usb: Adding SuperSpeed support to dummy_hcd
    On Mon, 23 May 2011, Felipe Balbi wrote:

    > > > > +module_param_named(is_super_speed, mod_data.is_super_speed, bool,
    > > > > +S_IRUGO); MODULE_PARM_DESC(is_super_speed, "true to simulate
    > > > > +SuperSpeed connection");
    > > >
    > > > you shouldn't need this. You should always enable SuperSpeed for this
    > > > driver.
    > >
    > > You mean I don't need the module parameter? IMO it's the best way to enable
    > > HS connection. If driver->speed=USB_SPEED_SUPER than dummy_hcd will try to
    > > enumerate the device on the SS root hub and if the gadget didn't provide SS
    > > descriptors - it will fail. Just as it happened before. Finding out from
    >
    > then it should hand the device over to the hs_hcd ;-) Meaning it would
    > disconnect the device, switch to hs_hcd and reconnect :-)

    No. That doesn't happen with real devices, so there's no reason
    dummy-hcd should do it.

    > > dummy_hcd that the enumeration failed is very complicated (if even possible)
    > > and I'm not sure that is the right thing to do... If you connect a real
    > > device over SS port to xHCI and the device doesn't provide SS descriptors -
    > > the enumeration fails and it's ok. But if you connect the same device to a
    > > HS port - it should work properly. This is what I tried to simulate with
    > > this parameter.
    >
    > it doesn't just fails, it gives the device over to the shared_hcd :-)

    It does not. xhci-hcd does not keep track of whether or not
    enumeration succeeds, and it doesn't do anything special when
    enumeration fails.

    Alan Stern



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