usb_ep_alloc_request — allocate a request object to use with this endpoint
struct usb_request * usb_ep_alloc_request (struct usb_ep * ep, gfp_t gfp_flags);
Request objects must be allocated with this call, since they normally
need controller-specific setup and may even need endpoint-specific
resources such as allocation of DMA descriptors.
Requests may be submitted with usb_ep_queue, and receive a single
completion callback. Free requests with usb_ep_free_request, when
they are no longer needed.
Returns the request, or null if one could not be allocated.