usb_alloc_urb — creates a new urb for a USB driver to use
number of iso packets for this urb
the type of memory to allocate, see
kmalloc for a list of
valid options for this.
Creates an urb for the USB driver to use, initializes a few internal structures, increments the usage counter, and returns a pointer to it.
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.