fm10k_fifo_tail_offset
u32 *tail = mbx->rx.buffer + fm10k_fifo_tail_offset(&mbx->rx, 0);
u16 end = fm10k_fifo_tail_offset(fifo, tail_offset);
msg = fifo->buffer + fm10k_fifo_tail_offset(fifo, total_len);
end = fm10k_fifo_tail_offset(fifo, mbx->pushed);
u16 offset = fm10k_fifo_tail_offset(fifo, mbx->pushed) - len;