The driver creates a waiting structure filling in the required mode value and associated data fields for that mode. This structure may be statically allocated and reused as required in any number of transactions. The USB system will inform the driver when the transaction has completed and the driver must then check the transactions completion status using USB_RequestGetState (SWI&55390) or the C A.P.I. function usb_request_get_state see Chapter 7, Transactions for more details on this.

There are six waiting modes each taking parameters as appropriate for the completion action (see Table A.9, “Constants used for USB waiting modes” for constants).

Any mode that specifies an action will have that action executed in either user or call-back context and should be prepared to adhere to the restrictions imposed by RISC OS.