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Documentation / sound / alsa / soc / platform.txt




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Based on kernel version 3.16. Page generated on 2014-08-06 21:41 EST.

1	ASoC Platform Driver
2	====================
3	
4	An ASoC platform driver class can be divided into audio DMA drivers, SoC DAI
5	drivers and DSP drivers. The platform drivers only target the SoC CPU and must
6	have no board specific code.
7	
8	Audio DMA
9	=========
10	
11	The platform DMA driver optionally supports the following ALSA operations:-
12	
13	/* SoC audio ops */
14	struct snd_soc_ops {
15		int (*startup)(struct snd_pcm_substream *);
16		void (*shutdown)(struct snd_pcm_substream *);
17		int (*hw_params)(struct snd_pcm_substream *, struct snd_pcm_hw_params *);
18		int (*hw_free)(struct snd_pcm_substream *);
19		int (*prepare)(struct snd_pcm_substream *);
20		int (*trigger)(struct snd_pcm_substream *, int);
21	};
22	
23	The platform driver exports its DMA functionality via struct
24	snd_soc_platform_driver:-
25	
26	struct snd_soc_platform_driver {
27		char *name;
28	
29		int (*probe)(struct platform_device *pdev);
30		int (*remove)(struct platform_device *pdev);
31		int (*suspend)(struct platform_device *pdev, struct snd_soc_cpu_dai *cpu_dai);
32		int (*resume)(struct platform_device *pdev, struct snd_soc_cpu_dai *cpu_dai);
33	
34		/* pcm creation and destruction */
35		int (*pcm_new)(struct snd_card *, struct snd_soc_codec_dai *, struct snd_pcm *);
36		void (*pcm_free)(struct snd_pcm *);
37	
38		/*
39		 * For platform caused delay reporting.
40		 * Optional.
41		 */
42		snd_pcm_sframes_t (*delay)(struct snd_pcm_substream *,
43			struct snd_soc_dai *);
44	
45		/* platform stream ops */
46		struct snd_pcm_ops *pcm_ops;
47	};
48	
49	Please refer to the ALSA driver documentation for details of audio DMA.
50	http://www.alsa-project.org/~iwai/writing-an-alsa-driver/
51	
52	An example DMA driver is soc/pxa/pxa2xx-pcm.c
53	
54	
55	SoC DAI Drivers
56	===============
57	
58	Each SoC DAI driver must provide the following features:-
59	
60	 1) Digital audio interface (DAI) description
61	 2) Digital audio interface configuration
62	 3) PCM's description
63	 4) SYSCLK configuration
64	 5) Suspend and resume (optional)
65	
66	Please see codec.txt for a description of items 1 - 4.
67	
68	
69	SoC DSP Drivers
70	===============
71	
72	Each SoC DSP driver usually supplies the following features :-
73	
74	 1) DAPM graph
75	 2) Mixer controls
76	 3) DMA IO to/from DSP buffers (if applicable)
77	 4) Definition of DSP front end (FE) PCM devices.
78	
79	Please see DPCM.txt for a description of item 4.
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