| ASoC Platform Driver |
| ==================== |
| |
| An ASoC platform driver can be divided into audio DMA and SoC DAI configuration |
| and control. 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_platform:- |
| |
| struct snd_soc_platform { |
| char *name; |
| |
| int (*probe)(struct platform_device *pdev); |
| int (*remove)(struct platform_device *pdev); |
| int (*suspend)(struct platform_device *pdev, struct snd_soc_cpu_dai *cpu_dai); |
| int (*resume)(struct platform_device *pdev, struct snd_soc_cpu_dai *cpu_dai); |
| |
| /* pcm creation and destruction */ |
| int (*pcm_new)(struct snd_card *, struct snd_soc_codec_dai *, struct snd_pcm *); |
| void (*pcm_free)(struct snd_pcm *); |
| |
| /* platform stream ops */ |
| struct snd_pcm_ops *pcm_ops; |
| }; |
| |
| Please refer to the ALSA driver documentation for details of audio DMA. |
| http://www.alsa-project.org/~iwai/writing-an-alsa-driver/c436.htm |
| |
| 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.txt for a description of items 1 - 4. |
