about change the sequence of interfaces in composite device in high speed usb stack

Question: Can we change the sequences of interfaces in composite device? Like we want the modem as the first interface?
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Answer: Yes, you can modify code in build_fd_struct()
Detail: By default on the hsu stack, in the composite device, the diag will be the first interface in the composite device, and NMEA(for GPS) will be the second one, then mass storage, modem, NDIS.
Why diag is the first? Because when switch to download mode, only diag port exists, to order to keep the same COM port in Windows, so in amss, diag is the first interface.If you want modem as the first interface, you shall consider this download issue.
If you use your own download application, it shall have the feature to detect the COM port if it changes. You can change the initialization sequence for different fd in build_fd_struct(). The sequence is related with fd in fds_to_init[], so you can change the sequence in build_fd_struct().