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diff --git a/Documentation/sound/soc/platform.rst b/Documentation/sound/soc/platform.rst new file mode 100644 index 0000000000..7036630eaf --- /dev/null +++ b/Documentation/sound/soc/platform.rst @@ -0,0 +1,78 @@ +==================== +ASoC Platform Driver +==================== + +An ASoC platform driver class can be divided into audio DMA drivers, SoC DAI +drivers and DSP drivers. The platform drivers only target the SoC CPU and must +have no board specific code. + +Audio DMA +========= + +The platform DMA driver optionally supports the following ALSA operations:- +:: + + /* SoC audio ops */ + struct snd_soc_ops { + int (*startup)(struct snd_pcm_substream *); + void (*shutdown)(struct snd_pcm_substream *); + int (*hw_params)(struct snd_pcm_substream *, struct snd_pcm_hw_params *); + int (*hw_free)(struct snd_pcm_substream *); + int (*prepare)(struct snd_pcm_substream *); + int (*trigger)(struct snd_pcm_substream *, int); + }; + +The platform driver exports its DMA functionality via struct +snd_soc_component_driver:- +:: + + struct snd_soc_component_driver { + const char *name; + + ... + int (*probe)(struct snd_soc_component *); + void (*remove)(struct snd_soc_component *); + int (*suspend)(struct snd_soc_component *); + int (*resume)(struct snd_soc_component *); + + /* pcm creation and destruction */ + int (*pcm_new)(struct snd_soc_pcm_runtime *); + void (*pcm_free)(struct snd_pcm *); + + ... + const struct snd_pcm_ops *ops; + const struct snd_compr_ops *compr_ops; + ... + }; + +Please refer to the ALSA driver documentation for details of audio DMA. +https://www.kernel.org/doc/html/latest/sound/kernel-api/writing-an-alsa-driver.html + +An example DMA driver is soc/pxa/pxa2xx-pcm.c + + +SoC DAI Drivers +=============== + +Each SoC DAI driver must provide the following features:- + +1. Digital audio interface (DAI) description +2. Digital audio interface configuration +3. PCM's description +4. SYSCLK configuration +5. Suspend and resume (optional) + +Please see codec.rst for a description of items 1 - 4. + + +SoC DSP Drivers +=============== + +Each SoC DSP driver usually supplies the following features :- + +1. DAPM graph +2. Mixer controls +3. DMA IO to/from DSP buffers (if applicable) +4. Definition of DSP front end (FE) PCM devices. + +Please see DPCM.txt for a description of item 4. |