libusb_alloc_transfer() function

Allocate a libusb transfer with a specified number of isochronous packet descriptors. The returned transfer is pre-initialized for you. When the new transfer is no longer needed, it should be freed with libusb_free_transfer(). Transfers intended for non-isochronous endpoints (e.g. control, bulk, interrupt) should specify an iso_packets count of zero. For transfers intended for isochronous endpoints, specify an appropriate number of packet descriptors to be allocated as part of the transfer. The returned transfer is not specially initialized for isochronous I/O; you are still required to set the libusb_transfer ::num_iso_packets "num_iso_packets" and libusb_transfer ::type "type" fields accordingly. It is safe to allocate a transfer with some isochronous packets and then use it on a non-isochronous endpoint. If you do this, ensure that at time of submission, num_iso_packets is 0 and that type is set appropriately.