1ASoC Machine Driver
2===================
3
4The ASoC machine (or board) driver is the code that glues together the platform
5and codec drivers.
6
7The machine driver can contain codec and platform specific code. It registers
8the audio subsystem with the kernel as a platform device and is represented by
9the following struct:-
10
11/* SoC machine */
12struct snd_soc_card {
13	char *name;
14
15	...
16
17	int (*probe)(struct platform_device *pdev);
18	int (*remove)(struct platform_device *pdev);
19
20	/* the pre and post PM functions are used to do any PM work before and
21	 * after the codec and DAIs do any PM work. */
22	int (*suspend_pre)(struct platform_device *pdev, pm_message_t state);
23	int (*suspend_post)(struct platform_device *pdev, pm_message_t state);
24	int (*resume_pre)(struct platform_device *pdev);
25	int (*resume_post)(struct platform_device *pdev);
26
27	...
28
29	/* CPU <--> Codec DAI links  */
30	struct snd_soc_dai_link *dai_link;
31	int num_links;
32
33	...
34};
35
36probe()/remove()
37----------------
38probe/remove are optional. Do any machine specific probe here.
39
40
41suspend()/resume()
42------------------
43The machine driver has pre and post versions of suspend and resume to take care
44of any machine audio tasks that have to be done before or after the codec, DAIs
45and DMA is suspended and resumed. Optional.
46
47
48Machine DAI Configuration
49-------------------------
50The machine DAI configuration glues all the codec and CPU DAIs together. It can
51also be used to set up the DAI system clock and for any machine related DAI
52initialisation e.g. the machine audio map can be connected to the codec audio
53map, unconnected codec pins can be set as such.
54
55struct snd_soc_dai_link is used to set up each DAI in your machine. e.g.
56
57/* corgi digital audio interface glue - connects codec <--> CPU */
58static struct snd_soc_dai_link corgi_dai = {
59	.name = "WM8731",
60	.stream_name = "WM8731",
61	.cpu_dai_name = "pxa-is2-dai",
62	.codec_dai_name = "wm8731-hifi",
63	.platform_name = "pxa-pcm-audio",
64	.codec_name = "wm8713-codec.0-001a",
65	.init = corgi_wm8731_init,
66	.ops = &corgi_ops,
67};
68
69struct snd_soc_card then sets up the machine with its DAIs. e.g.
70
71/* corgi audio machine driver */
72static struct snd_soc_card snd_soc_corgi = {
73	.name = "Corgi",
74	.dai_link = &corgi_dai,
75	.num_links = 1,
76};
77
78
79Machine Power Map
80-----------------
81
82The machine driver can optionally extend the codec power map and to become an
83audio power map of the audio subsystem. This allows for automatic power up/down
84of speaker/HP amplifiers, etc. Codec pins can be connected to the machines jack
85sockets in the machine init function.
86
87
88Machine Controls
89----------------
90
91Machine specific audio mixer controls can be added in the DAI init function.
92