platform.rst (2016B)
1==================== 2ASoC Platform Driver 3==================== 4 5An ASoC platform driver class can be divided into audio DMA drivers, SoC DAI 6drivers and DSP drivers. The platform drivers only target the SoC CPU and must 7have no board specific code. 8 9Audio DMA 10========= 11 12The platform DMA driver optionally supports the following ALSA operations:- 13:: 14 15 /* SoC audio ops */ 16 struct snd_soc_ops { 17 int (*startup)(struct snd_pcm_substream *); 18 void (*shutdown)(struct snd_pcm_substream *); 19 int (*hw_params)(struct snd_pcm_substream *, struct snd_pcm_hw_params *); 20 int (*hw_free)(struct snd_pcm_substream *); 21 int (*prepare)(struct snd_pcm_substream *); 22 int (*trigger)(struct snd_pcm_substream *, int); 23 }; 24 25The platform driver exports its DMA functionality via struct 26snd_soc_component_driver:- 27:: 28 29 struct snd_soc_component_driver { 30 const char *name; 31 32 ... 33 int (*probe)(struct snd_soc_component *); 34 void (*remove)(struct snd_soc_component *); 35 int (*suspend)(struct snd_soc_component *); 36 int (*resume)(struct snd_soc_component *); 37 38 /* pcm creation and destruction */ 39 int (*pcm_new)(struct snd_soc_pcm_runtime *); 40 void (*pcm_free)(struct snd_pcm *); 41 42 ... 43 const struct snd_pcm_ops *ops; 44 const struct snd_compr_ops *compr_ops; 45 ... 46 }; 47 48Please refer to the ALSA driver documentation for details of audio DMA. 49http://www.alsa-project.org/~iwai/writing-an-alsa-driver/ 50 51An example DMA driver is soc/pxa/pxa2xx-pcm.c 52 53 54SoC DAI Drivers 55=============== 56 57Each SoC DAI driver must provide the following features:- 58 591. Digital audio interface (DAI) description 602. Digital audio interface configuration 613. PCM's description 624. SYSCLK configuration 635. Suspend and resume (optional) 64 65Please see codec.rst for a description of items 1 - 4. 66 67 68SoC DSP Drivers 69=============== 70 71Each SoC DSP driver usually supplies the following features :- 72 731. DAPM graph 742. Mixer controls 753. DMA IO to/from DSP buffers (if applicable) 764. Definition of DSP front end (FE) PCM devices. 77 78Please see DPCM.txt for a description of item 4.