MAX_FIFO_SIZE
usb_ep_set_maxpacket_limit(&ep->ep, MAX_FIFO_SIZE);
u8 fifo[MAX_FIFO_SIZE];
mdev_state->s[0].max_fifo_size = MAX_FIFO_SIZE;
mdev_state->s[1].max_fifo_size = MAX_FIFO_SIZE;
mdev_state->s[index].max_fifo_size = MAX_FIFO_SIZE;
#define CIRCULAR_BUF_INC_IDX(idx) (idx = (idx + 1) & (MAX_FIFO_SIZE - 1))