Add the rt linux 4.1.3-rt3 as base

[kvmfornfv.git] / kernel / Documentation / sound / alsa / soc / machine.txt

diff --git a/kernel/Documentation/sound/alsa/soc/machine.txt b/kernel/Documentation/sound/alsa/soc/machine.txt
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+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 componnent 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.