USB_SG_SIZE
num_sgs = DIV_ROUND_UP(uurb->buffer_length, USB_SG_SIZE);
u = (totlen > USB_SG_SIZE) ? USB_SG_SIZE : totlen;
size = (len > USB_SG_SIZE) ? USB_SG_SIZE : len;
size = (len > USB_SG_SIZE) ? USB_SG_SIZE : len;