When an input module instance has received enough input to fully
populate the struct sr_dev_inst, sdi_ready is set to TRUE and its
receive() method returns immediately. Any remaining received data
is buffered until the next time the function is called.
SR_OK: a match was found.
SR_ERR: no match.
SR_ERR_DATA: a match was found but the module cannot handle the input.
SR_OK_CONTINUE: some module didn't have enough data to be sure.