usb_alloc_urb — creates a new urb for a USB driver to use
struct urb * usb_alloc_urb (int iso_packets, gfp_t mem_flags);
iso_packetsnumber of iso packets for this urb
mem_flags
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, 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.