[alsa-devel] DPCM: BE to BE cpu DAIs question‏

[srv_kaichieh.chaung]

Hi,
        Our platform use ASoC structure. Currently, we want to refactor
our driver to use DPCM structure.
I followed the documentation of DPCM, but have some trouble
implementing hostless  BE to BE dai links.

My question is:
1.  Is there any  code example for this(hostless BE to BE)?
Since I didn't see any existing code on  linux kernel.
2.  From  documentation,  i have to assgin  a  snd_soc_pcm_stream for BE
dais.
     It seems that the BE<->BE dai links can only support one spec
(format/rates/ch).
    Or am i getting it wrong, does it support dynamically change of the
spec?

Thanks in advanced!

--------------------------------------------------------------------------------------
  I have  tried some  implementations, but failed.  My linux version is
3.18.

Illustration,
PCM -----------------> BE1
                                       ↑
                                          -------< BE2

Code snippet,

static const struct snd_soc_dapm_route machine_routes[] = {
	{BE1_PLAYBACK_CPU_DAI_STNAME, NULL, FE_STNAME},
	{BE1_PLAYBACK_CPU_DAI_STNAME, NULL, BE2_CAPTURE_CPU_DAI_STNAME},
};

static const struct snd_soc_pcm_stream dai_params = {
	.formats = SNDRV_PCM_FMTBIT_S32_LE,
	.rate_min = 48000,
	.rate_max = 48000,
	.channels_min = 2,
	.channels_max = 2,
};

static struct snd_soc_dai_link mt_soc_dai_common[] = {
		{
			.name = FE_PCM,
			.stream_name = FE_STNAME,
			.cpu_dai_name = FE_CPUDAINAME,	// cannot use dummy!!!!
			.platform_name = FE_PCMNAME,
			.codec_name = "snd-soc-dummy",
			.codec_dai_name = "snd-soc-dummy-dai",
			.init = mt_soc_audio_init3,
			.ops = &kc_snd_soc_ops,
			.dynamic = 1,
			.dpcm_playback = 1,
			.trigger = {SND_SOC_DPCM_TRIGGER_POST, SND_SOC_DPCM_TRIGGER_POST},
		 },
		 /* BE DAIs */
		{
			.name = "BE2",
			.cpu_dai_name = BE2_PLAYBACK_CPU_DAI, //"snd-soc-dummy-dai",
			.platform_name = "snd-soc-dummy",
			.codec_name = "snd-soc-dummy",
			.codec_dai_name = "snd-soc-dummy-dai",
			.dai_fmt = SND_SOC_DAIFMT_I2S | SND_SOC_DAIFMT_NB_NF |
				SND_SOC_DAIFMT_CBS_CFS,
			.no_pcm = 1,
			.dpcm_playback = 1,
			.dpcm_capture = 1,
			.ignore_suspend = 1,
			.ignore_pmdown_time = 1,
			.params = &dai_params,
		},
		{
			.name = BE1_PLAYBACK,
			.cpu_dai_name = BE1_PLAYBACK_CPU_DAI,
			.platform_name = "snd-soc-dummy",
			.codec_name = "snd-soc-dummy",
			.codec_dai_name = "snd-soc-dummy-dai",
			.no_pcm = 1,
			.dpcm_playback = 1,
			.dpcm_capture = 1,
			.ignore_suspend = 1,
			.ignore_pmdown_time = 1,
			.params = &dai_params,
		},

1. when only  routes  PCM-->BE1,  
        If i add .params in BE1 soc dai link,  when i start PCM, it will
crash. and get "Unable to handle kernel NULL pointer dereference at
virtual address 000000d0"
        Seems to crash in dpcm_be_dai_startup()
         If i removed .params, it will not crash, and play normally.

2.  when only with BE2--> BE1,
        BE2 is never trigger,  where did i  get wrong?

Thanks.




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