1 ==============================================
2 Creating codec to codec dai link for ALSA dapm
3 ==============================================
4
5 Mostly the flow of audio is always from CPU to
6 will look as below:
7 ::
8
9 --------- ---------
10 | | dai | |
11 CPU -------> codec
12 | | | |
13 --------- ---------
14
15 In case your system looks as below:
16 ::
17
18 ---------
19 | |
20 codec-2
21 | |
22 ---------
23 |
24 dai-2
25 |
26 ---------- ---------
27 | | dai-1 | |
28 CPU -------> codec-1
29 | | | |
30 ---------- ---------
31 |
32 dai-3
33 |
34 ---------
35 | |
36 codec-3
37 | |
38 ---------
39
40 Suppose codec-2 is a bluetooth chip and codec-
41 a speaker and you have a below scenario:
42 codec-2 will receive the audio data and the us
43 audio through codec-3 without involving the CP
44 aforementioned case is the ideal case when cod
45 connection should be used.
46
47 Your dai_link should appear as below in your m
48 file:
49 ::
50
51 /*
52 * this pcm stream only supports 24 bit, 2 ch
53 * 48k sampling rate.
54 */
55 static const struct snd_soc_pcm_stream dsp_co
56 .formats = SNDRV_PCM_FMTBIT_S24_LE,
57 .rate_min = 48000,
58 .rate_max = 48000,
59 .channels_min = 2,
60 .channels_max = 2,
61 };
62
63 {
64 .name = "CPU-DSP",
65 .stream_name = "CPU-DSP",
66 .cpu_dai_name = "samsung-i2s.0",
67 .codec_name = "codec-2,
68 .codec_dai_name = "codec-2-dai_name",
69 .platform_name = "samsung-i2s.0",
70 .dai_fmt = SND_SOC_DAIFMT_I2S | SND_SOC_DA
71 | SND_SOC_DAIFMT_CBM_CFM,
72 .ignore_suspend = 1,
73 .c2c_params = &dsp_codec_params,
74 .num_c2c_params = 1,
75 },
76 {
77 .name = "DSP-CODEC",
78 .stream_name = "DSP-CODEC",
79 .cpu_dai_name = "wm0010-sdi2",
80 .codec_name = "codec-3,
81 .codec_dai_name = "codec-3-dai_name",
82 .dai_fmt = SND_SOC_DAIFMT_I2S | SND_SOC_DA
83 | SND_SOC_DAIFMT_CBM_CFM,
84 .ignore_suspend = 1,
85 .c2c_params = &dsp_codec_params,
86 .num_c2c_params = 1,
87 },
88
89 Above code snippet is motivated from sound/soc
90
91 Note the "c2c_params" callback which lets the
92 dai_link is a codec to codec connection.
93
94 In dapm core a route is created between cpu_da
95 and codec_dai capture widget for playback path
96 true for capture path. In order for this afore
97 triggered, DAPM needs to find a valid endpoint
98 a sink or source widget corresponding to playb
99 respectively.
100
101 In order to trigger this dai_link widget, a th
102 the speaker amp can be created as demonstrated
103 sets appropriate constraints for the device ev
104
105 Make sure to name your corresponding cpu and c
106 dai names ending with "Playback" and "Capture"
107 will link and power those dais based on the na
108
109 A dai_link in a "simple-audio-card" will autom
110 codec to codec when all DAIs on the link belon
111 The dai_link will be initialized with the subs
112 (channels, format, sample rate) supported by a
113 there is no way to provide these parameters in
114 mostly useful for communication with simple fi
115 as a Bluetooth controller or cellular modem.
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