Memory-management functions

usbd_alloc()
Allocate memory area to use for data transfers.
usbd_free()
Free memory allocated by usbd_alloc().
usbd_mphys()
Get the physical address of memory allocated by usbd_alloc().
usbd_alloc_urb()
Allocate a USB Request Block for subsequent URB-based operations.
usbd_free_urb()
Free the URB allocated by usbd_alloc_urb().