1 =======================
2 ASoC Codec Class Driver
3 =======================
4
5 The codec class driver is generic and hardware
6 the codec, FM, MODEM, BT or external DSP to pr
7 It should contain no code that is specific to
8 All platform and machine specific code should
9 machine drivers respectively.
10
11 Each codec class driver *must* provide the fol
12
13 1. Codec DAI and PCM configuration
14 2. Codec control IO - using RegMap API
15 3. Mixers and audio controls
16 4. Codec audio operations
17 5. DAPM description.
18 6. DAPM event handler.
19
20 Optionally, codec drivers can also provide:-
21
22 7. DAC Digital mute control.
23
24 Its probably best to use this guide in conjunc
25 driver code in sound/soc/codecs/
26
27 ASoC Codec driver breakdown
28 ===========================
29
30 Codec DAI and PCM configuration
31 -------------------------------
32 Each codec driver must have a struct snd_soc_d
33 PCM capabilities and operations. This struct i
34 registered with the core by your machine drive
35
36 e.g.
37 ::
38
39 static struct snd_soc_dai_ops wm8731_dai_ops
40 .prepare = wm8731_pcm_prepare,
41 .hw_params = wm8731_hw_params,
42 .shutdown = wm8731_shutdown,
43 .mute_stream = wm8731_mute,
44 .set_sysclk = wm8731_set_dai_syscl
45 .set_fmt = wm8731_set_dai_fmt,
46 };
47
48 struct snd_soc_dai_driver wm8731_dai = {
49 .name = "wm8731-hifi",
50 .playback = {
51 .stream_name = "Playback",
52 .channels_min = 1,
53 .channels_max = 2,
54 .rates = WM8731_RATES,
55 .formats = WM8731_FORMATS,},
56 .capture = {
57 .stream_name = "Capture",
58 .channels_min = 1,
59 .channels_max = 2,
60 .rates = WM8731_RATES,
61 .formats = WM8731_FORMATS,},
62 .ops = &wm8731_dai_ops,
63 .symmetric_rate = 1,
64 };
65
66
67 Codec control IO
68 ----------------
69 The codec can usually be controlled via an I2C
70 (AC97 combines control with data in the DAI).
71 Regmap API for all codec IO. Please see includ
72 codec drivers for example regmap usage.
73
74
75 Mixers and audio controls
76 -------------------------
77 All the codec mixers and audio controls can be
78 macros defined in soc.h.
79 ::
80
81 #define SOC_SINGLE(xname, reg, shift, mask
82
83 Defines a single control as follows:-
84 ::
85
86 xname = Control name e.g. "Playback Volume"
87 reg = codec register
88 shift = control bit(s) offset in register
89 mask = control bit size(s) e.g. mask of 7 =
90 invert = the control is inverted
91
92 Other macros include:-
93 ::
94
95 #define SOC_DOUBLE(xname, reg, shift_left,
96
97 A stereo control
98 ::
99
100 #define SOC_DOUBLE_R(xname, reg_left, reg_
101
102 A stereo control spanning 2 registers
103 ::
104
105 #define SOC_ENUM_SINGLE(xreg, xshift, xmas
106
107 Defines an single enumerated control as follow
108 ::
109
110 xreg = register
111 xshift = control bit(s) offset in register
112 xmask = control bit(s) size
113 xtexts = pointer to array of strings that d
114
115 #define SOC_ENUM_DOUBLE(xreg, xshift_l, xsh
116
117 Defines a stereo enumerated control
118
119
120 Codec Audio Operations
121 ----------------------
122 The codec driver also supports the following A
123 ::
124
125 /* SoC audio ops */
126 struct snd_soc_ops {
127 int (*startup)(struct snd_pcm_substrea
128 void (*shutdown)(struct snd_pcm_substr
129 int (*hw_params)(struct snd_pcm_substr
130 int (*hw_free)(struct snd_pcm_substrea
131 int (*prepare)(struct snd_pcm_substrea
132 };
133
134 Please refer to the ALSA driver PCM documentat
135 https://www.kernel.org/doc/html/latest/sound/k
136
137
138 DAPM description
139 ----------------
140 The Dynamic Audio Power Management description
141 components and their relationships and registe
142 Please read dapm.rst for details of building t
143
144 Please also see the examples in other codec dr
145
146
147 DAPM event handler
148 ------------------
149 This function is a callback that handles codec
150 domain PM calls (e.g. suspend and resume). It
151 to sleep when not in use.
152
153 Power states:-
154 ::
155
156 SNDRV_CTL_POWER_D0: /* full On */
157 /* vref/mid, clk and osc on, active */
158
159 SNDRV_CTL_POWER_D1: /* partial On */
160 SNDRV_CTL_POWER_D2: /* partial On */
161
162 SNDRV_CTL_POWER_D3hot: /* Off, with po
163 /* everything off except vref/vmid, in
164
165 SNDRV_CTL_POWER_D3cold: /* Everything
166
167
168 Codec DAC digital mute control
169 ------------------------------
170 Most codecs have a digital mute before the DAC
171 minimise any system noise. The mute stops any
172 entering the DAC.
173
174 A callback can be created that is called by th
175 when the mute is applied or freed.
176
177 i.e.
178 ::
179
180 static int wm8974_mute(struct snd_soc_dai *d
181 {
182 struct snd_soc_component *component =
183 u16 mute_reg = snd_soc_component_read(
184
185 if (mute)
186 snd_soc_component_write(compon
187 else
188 snd_soc_component_write(compon
189 return 0;
190 }
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