USB: xhci: Control transfer support.
Allow device drivers to enqueue URBs to control endpoints on devices under an xHCI host controller. Each control transfer is represented by a series of Transfer Descriptors (TDs) written to an endpoint ring. There is one TD for the Setup phase, (optionally) one TD for the Data phase, and one TD for the Status phase. Enqueue these TDs onto the endpoint ring that represents the control endpoint. The host controller hardware will return an event on the event ring that points to the (DMA) address of one of the TDs on the endpoint ring. If the transfer was successful, the transfer event TRB will have a completion code of success, and it will point to the Status phase TD. Anything else is considered an error. This should work for control endpoints besides the default endpoint, but that hasn't been tested. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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