On Sunday 01 July 2007, jidong xiao wrote:
> Take root hub for example, how does the hub itself know whether its
> upstream facing port is connected at high-speed or
> full-speed?

There *IS* no upstream facing port.  The upstream link hooks
to a non-USB bus. 


> Futhermore, if a host send a GET_DESCRIPTOR request to a 
> hub, how does it know which set of descriptor should be reported?

For non-root hubs, the answer is obvious:  the right one
according to the spec (high speed vs low speed) and hardware
capabilities (e.g. TT-per port, per-hub, or not).

For root hubs, any answer whatsoever is out-of-spec.  All that's
important is that Linux not confuse itself by the answer it gives.


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