On Mon, 7 Aug 2006, rakesh kn wrote:

> In function rh_call_control , there is no support for
> HUB_CLEAR_TT_BUFFER hub request.

No.  This is because rh_call_control handles only requests that are common
to all root hubs.  Since most root hubs don't support HUB_CLEAR_TT_BUFFER, 
neither does rh_call_control.

> Suppose if we are connecting low/full speed devices to a USB 2.0 EHCI
> , host controller., through a HUB , which has a transaction translator
> . Then the following function "usb_hub_tt_clear_buffer" will be called
> from the  function "qtd_copy_status" in the file ehci-q.c .. in case
> of errors  in CSPILT transaction  .
> 
> But since this is a hub-transaction request... the function
> "rh_call_control" , is not implementing the request type
> HUB_CLEAR_TT_BUFFER.
> 
> Please explain why is this. Is the hub requests for external hubs
> handled elsewhere.

Of course it is.  It is sent to the external hub and handled there.

> Also why is that the TT hub contents not cleared if the EHCI
> controller has an embedded Transcation translator ,, as is evident
> from the following code in the function qtd_copy_status.

I don't know.  You should ask the person who developed the embedded TT 
support for EHCI.

Alan Stern


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