NFP_MBOX_DATA_LEN
err = nfp_rtsym_writeq(pf->cpp, pf->mbox, NFP_MBOX_DATA_LEN, in_length);
err = nfp_rtsym_readl(pf->cpp, pf->mbox, NFP_MBOX_DATA_LEN, &val);
err = nfp_rtsym_readl(pf->cpp, pf->mbox, NFP_MBOX_DATA_LEN, &val);