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diff --git a/Documentation/sound/soc/machine.rst b/Documentation/sound/soc/machine.rst new file mode 100644 index 000000000..515c9444d --- /dev/null +++ b/Documentation/sound/soc/machine.rst @@ -0,0 +1,97 @@ +=================== +ASoC Machine Driver +=================== + +The ASoC machine (or board) driver is the code that glues together all the +component drivers (e.g. codecs, platforms and DAIs). It also describes the +relationships between each component which include audio paths, GPIOs, +interrupts, clocking, jacks and voltage regulators. + +The machine driver can contain codec and platform specific code. It registers +the audio subsystem with the kernel as a platform device and is represented by +the following struct:- +:: + + /* SoC machine */ + struct snd_soc_card { + char *name; + + ... + + int (*probe)(struct platform_device *pdev); + int (*remove)(struct platform_device *pdev); + + /* the pre and post PM functions are used to do any PM work before and + * after the codec and DAIs do any PM work. */ + int (*suspend_pre)(struct platform_device *pdev, pm_message_t state); + int (*suspend_post)(struct platform_device *pdev, pm_message_t state); + int (*resume_pre)(struct platform_device *pdev); + int (*resume_post)(struct platform_device *pdev); + + ... + + /* CPU <--> Codec DAI links */ + struct snd_soc_dai_link *dai_link; + int num_links; + + ... + }; + +probe()/remove() +---------------- +probe/remove are optional. Do any machine specific probe here. + + +suspend()/resume() +------------------ +The machine driver has pre and post versions of suspend and resume to take care +of any machine audio tasks that have to be done before or after the codec, DAIs +and DMA is suspended and resumed. Optional. + + +Machine DAI Configuration +------------------------- +The machine DAI configuration glues all the codec and CPU DAIs together. It can +also be used to set up the DAI system clock and for any machine related DAI +initialisation e.g. the machine audio map can be connected to the codec audio +map, unconnected codec pins can be set as such. + +struct snd_soc_dai_link is used to set up each DAI in your machine. e.g. +:: + + /* corgi digital audio interface glue - connects codec <--> CPU */ + static struct snd_soc_dai_link corgi_dai = { + .name = "WM8731", + .stream_name = "WM8731", + .cpu_dai_name = "pxa-is2-dai", + .codec_dai_name = "wm8731-hifi", + .platform_name = "pxa-pcm-audio", + .codec_name = "wm8713-codec.0-001a", + .init = corgi_wm8731_init, + .ops = &corgi_ops, + }; + +struct snd_soc_card then sets up the machine with its DAIs. e.g. +:: + + /* corgi audio machine driver */ + static struct snd_soc_card snd_soc_corgi = { + .name = "Corgi", + .dai_link = &corgi_dai, + .num_links = 1, + }; + + +Machine Power Map +----------------- + +The machine driver can optionally extend the codec power map and to become an +audio power map of the audio subsystem. This allows for automatic power up/down +of speaker/HP amplifiers, etc. Codec pins can be connected to the machines jack +sockets in the machine init function. + + +Machine Controls +---------------- + +Machine specific audio mixer controls can be added in the DAI init function. |