# madplay 123.mp3
 WM8960 Playback: ASoC: unmatched rate symmetry: 8000 - 44100
 output: ioctl(SNDCTL_DSP_SPEED): Invalid argument

#aplay  windowsxp.wav
 aplay: pcm_write:1939: write error: Input/output error
=====================================================
static int soc_pcm_params_symmetry(struct snd_pcm_substream *substream,
                struct
 
 snd_pcm_hw_params *params)
{
    struct snd_soc_dai *cpu_dai = substream->private_data->cpu_dai;

    rate = params_rate(params);
    if (symmetry && cpu_dai->rate && cpu_dai->rate != rate) {
        dev_err(rtd->dev, "ASoC: unmatched rate symmetry: %d - %d\n",//soc-pcm.c 157
 

    }
}
            ||
static int soc_pcm_hw_params(struct snd_pcm_substream *substream,
                struct snd_pcm_hw_params *params)
{
    ret = soc_pcm_params_symmetry(substream, params);
}
            ||
int dpcm_be_dai_hw_params(struct snd_soc_pcm_runtime *fe, int stream)
{
    struct snd_soc_dpcm *dpcm;
    int
 
 ret;

    list_for_each_entry(dpcm, &fe->dpcm[stream].be_clients, list_be) {

        struct snd_soc_pcm_runtime *be = dpcm->be;
        struct snd_pcm_substream *be_substream =snd_soc_dpcm_get_substream(be, stream);

        /* copy params for each dpcm */
        memcpy(&dpcm->hw_params, &fe->dpcm[stream].hw_params,
                sizeof(struct snd_pcm_hw_params));

        ret = soc_pcm_hw_params(be_substream, &dpcm->hw_params);
}
            ||
static int dpcm_fe_dai_hw_params(struct snd_pcm_substream *substream,
                 struct snd_pcm_hw_params *params)
{
    struct snd_soc_pcm_runtime *fe = substream->private_data;
    int ret, stream = substream->stream;

    memcpy(&fe->dpcm[substream->stream].hw_params, params,
            sizeof(struct snd_pcm_hw_params));
    ret = dpcm_be_dai_hw_params(fe, substream->stream);
}
            ||
int soc_new_pcm(struct snd_soc_pcm_runtime *rtd, int num)
{

        rtd->ops.hw_params  = dpcm_fe_dai_hw_params;
}
            ||
static int soc_probe_link_dais(struct snd_soc_card *card, int num, int order)
{                       //soc-core.c 1429
    struct snd_soc_dai_link *dai_link = &card->dai_link[num];
    struct snd_soc_pcm_runtime *rtd = &card->rtd[num];
    ret = soc_new_pcm(rtd, num);
}
            ||

static int snd_soc_instantiate_card(struct snd_soc_card *card)
{
    /* probe all DAI links on this card */
    /*probe所有音效卡上的DAI連結，主要執行兩個任務：
     *一是呼叫了s3c24xx_i2s_probe函式，完成i2s控制器時鐘啟動和
     *    s3c24xx的i2s對應的io口配置初始化；
     *二是執行了soc_new_pcm函式來建立PCM
     */
    ret = soc_probe_link_dais(card, i, order);
}
            ||
int snd_soc_register_card(struct snd_soc_card *card)
{
    ret = snd_soc_instantiate_card(card);
}
            ||
static int soc_probe(struct platform_device *pdev)
{
    struct snd_soc_card *card = platform_get_drvdata(pdev);
    return snd_soc_register_card(card);
}           ||
static struct platform_driver soc_driver = {
    .driver     = {
        .name       = "soc-audio",
    },
    .probe      = soc_probe,
};
            ||
static int __init mixtile_audio_init(void)
{           //smdk_wm8960.c 321
    mixtile_snd_device = platform_device_alloc("soc-audio", -1);
}
=========================
ioctl出錯：
static long snd_pcm_oss_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
    switch (cmd) {
    case SNDCTL_DSP_RESET:
        return snd_pcm_oss_reset(pcm_oss_file);
    case SNDCTL_DSP_SYNC:
        return snd_pcm_oss_sync(pcm_oss_file);
    case SNDCTL_DSP_SPEED:
        if (get_user(res, p))
            return -EFAULT;
        if ((res = snd_pcm_oss_set_rate(pcm_oss_file, res))<0)
            return res;//定位到這裡  返回-22 sound/core/oss/pcm_oss.c 2533
        return put_user(res, p);
}
        ||
        \/
static int snd_pcm_oss_change_params(struct snd_pcm_substream *substream)
{
    if ((err = snd_pcm_kernel_ioctl(substream, SNDRV_PCM_IOCTL_HW_PARAMS, sparams)) < 0) {  //sound/core/oss/pcm_oss.c 1000
        snd_printd("HW_PARAMS failed: %i\n", err);
        printk("snd_pcm_kernel_ioctl < 0"); 
        goto failure;
    }
}
        ||
static int snd_pcm_common_ioctl1(struct file *file,
                 struct snd_pcm_substream *substream,
                 unsigned int cmd, void __user *arg)
{
    case SNDRV_PCM_IOCTL_HW_PARAMS:
        return snd_pcm_hw_params_user(substream, arg);//sound/core/pcm_native.c 2566
}
        ||
static int snd_pcm_hw_params(struct snd_pcm_substream *substream,
                 struct snd_pcm_hw_params *params)
{
    if (substream->ops->hw_params != NULL) {
        err = substream->ops->hw_params(substream, params);//sound/core/pcm_native.c 430
        if (err < 0)
        {
            goto _error;
        }
    }
}
        ||
static int soc_pcm_hw_params(struct snd_pcm_substream *substream,
                struct snd_pcm_hw_params *params)
{
    ret = soc_pcm_params_symmetry(substream, params);
    if (ret)
    {
        printk("--%s-----%d-----\n",__FUNCTION__,__LINE__);//error <<====//sound/soc/soc-pcm.c  619
        goto out;
    }
}
==========================          
 WM8960 Playback: ASoC: unmatched rate symmetry: 8000 - 44100
 output: ioctl(SNDCTL_DSP_SPEED): Invalid argument
解決:下面的ioctl是由上面的rate不匹配造成的
cpu->rate的設定是在：
wm8960.c
static struct snd_soc_dai_driver wm8960_dai = {
    .name = "wm8960-hifi",
    .playback = {
        .stream_name = "Playback",
        .channels_min = 1,
        .channels_max = 2,
        .rates = WM8960_RATES,//改為SNDRV_PCM_RATE_44100
        .formats = WM8960_FORMATS,},
    .capture = {
        .stream_name = "Capture",
        .channels_min = 1,
        .channels_max = 2,
        .rates = WM8960_RATES,
        .formats = WM8960_FORMATS,},
    .ops = &wm8960_dai_ops,
    .symmetric_rates = 1,
};