mirror of https://gitee.com/openkylin/linux.git
98 lines
2.8 KiB
ReStructuredText
98 lines
2.8 KiB
ReStructuredText
===================
|
|
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.
|