iso_packets
mem_flags
Creates an urb for the USB driver to use, initializes a few internal structures, incrementes the usage counter, and returns a pointer to it.
If no memory is available, NULL is returned.
If the driver want to use this urb for interrupt, control, or bulk endpoints, pass '0' as the number of iso packets.
The driver must call usb_free_urb when it is finished with the urb.