CMD_HDR_DIF_SGL_LEN_OFF
#define CMD_HDR_DIF_SGL_LEN_MSK (0xffff << CMD_HDR_DIF_SGL_LEN_OFF)
hdr->sg_len |= cpu_to_le32(n_elem << CMD_HDR_DIF_SGL_LEN_OFF);
#define CMD_HDR_DIF_SGL_LEN_MSK (0xffff << CMD_HDR_DIF_SGL_LEN_OFF)