hi3798m怎么设置I2S0作为音频输出端口？？？？

代码如下，执行HI_UNF_SND_Open失败

HI_S32 HIADP_Snd_Init(HI_VOID)
{
    HI_S32                  Ret;
    HI_UNF_SND_ATTR_S       stAttr;

    Ret = HI_UNF_SND_Init();
    if (Ret != HI_SUCCESS)
    {
        sample_common_printf("call HI_UNF_SND_Init failed.\n");
        return Ret;
    }
    Ret = HI_UNF_SND_GetDefaultOpenAttr(HI_UNF_SND_0, &stAttr);
    if (Ret != HI_SUCCESS)
    {
        sample_common_printf("call HI_UNF_SND_GetDefaultOpenAttr failed.\n");
        return Ret;
    }


stAttr.u32PortNum=3;
stAttr.enSampleRate=HI_UNF_SAMPLE_RATE_48K;
stAttr.stOutport[0].enOutPort = HI_UNF_SND_OUTPUTPORT_DAC0 ; //HI_UNF_SND_OUTPUTPORT_DAC0; HI_UNF_SND_OUTPUTPORT_I2S0
stAttr.stOutport[1].enOutPort = HI_UNF_SND_OUTPUTPORT_HDMI0  ;
stAttr.stOutport[2].enOutPort = HI_UNF_SND_OUTPUTPORT_I2S0  ;
stAttr.stOutport[2].unAttr.stI2sAttr.stAttr.bMaster=HI_FALSE;
stAttr.stOutport[2].unAttr.stI2sAttr.stAttr.enI2sMode=HI_UNF_I2S_STD_MODE;
stAttr.stOutport[2].unAttr.stI2sAttr.stAttr.enChannel=HI_UNF_I2S_CHNUM_2;
stAttr.stOutport[2].unAttr.stI2sAttr.stAttr.enBitDepth=HI_UNF_I2S_BIT_DEPTH_16;

sample_common_printf("%s u32PortNum=%d,enOutPort=%d %d \n",__func__,stAttr.u32PortNum,stAttr.stOutport[0].enOutPort,stAttr.stOutport[1].enOutPort);

    Ret = HI_UNF_SND_Open(HI_UNF_SND_0, &stAttr);
    if (Ret != HI_SUCCESS)
    {
        sample_common_printf("call HI_UNF_SND_Open failed.\n");
        return Ret;
    }

    return HI_SUCCESS;
}