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Commit 693ba474 authored by Takashi Iwai's avatar Takashi Iwai
Browse files

ASoC: doc: ReSTize codec.txt 



A simple conversion from a plain text file.
The section numbers are dropped to align with other documents.

Acked-by: default avatarMark Brown <broonie@kernel.org>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent 8e5336a1

Documentation/sound/alsa/soc/codec.txt→Documentation/sound/soc/codec.rst

+43 −32
Original line number Diff line number Diff line 
=======================

ASoC Codec Class Driver

=======================
@@ -9,16 +10,16 @@ machine drivers respectively. 


Each codec class driver *must* provide the following features:-



 1) Codec DAI and PCM configuration

 2) Codec control IO - using RegMap API

 3) Mixers and audio controls

 4) Codec audio operations

 5) DAPM description.

 6) DAPM event handler.

1. Codec DAI and PCM configuration

2. Codec control IO - using RegMap API

3. Mixers and audio controls

4. Codec audio operations

5. DAPM description.

6. DAPM event handler.



Optionally, codec drivers can also provide:-



 7) DAC Digital mute control.

7. DAC Digital mute control.



Its probably best to use this guide in conjunction with the existing codec

driver code in sound/soc/codecs/
@@ -26,13 +27,14 @@ driver code in sound/soc/codecs/ 
ASoC Codec driver breakdown

===========================



1 - Codec DAI and PCM configuration

-----------------------------------

Codec DAI and PCM configuration

-------------------------------

Each codec driver must have a struct snd_soc_dai_driver to define its DAI and

PCM capabilities and operations. This struct is exported so that it can be

registered with the core by your machine driver.



e.g.

::



  static struct snd_soc_dai_ops wm8731_dai_ops = {

	.prepare	= wm8731_pcm_prepare,
@@ -62,22 +64,24 @@ struct snd_soc_dai_driver wm8731_dai = { 
  };





2 - Codec control IO

--------------------

Codec control IO

----------------

The codec can usually be controlled via an I2C or SPI style interface

(AC97 combines control with data in the DAI). The codec driver should use the

Regmap API for all codec IO. Please see include/linux/regmap.h and existing

codec drivers for example regmap usage.





3 - Mixers and audio controls

-----------------------------

Mixers and audio controls

-------------------------

All the codec mixers and audio controls can be defined using the convenience

macros defined in soc.h.

::



    #define SOC_SINGLE(xname, reg, shift, mask, invert)



Defines a single control as follows:-

::



  xname = Control name e.g. "Playback Volume"

  reg = codec register
@@ -86,18 +90,22 @@ Defines a single control as follows:- 
  invert = the control is inverted



Other macros include:-

::



    #define SOC_DOUBLE(xname, reg, shift_left, shift_right, mask, invert)



A stereo control

::



    #define SOC_DOUBLE_R(xname, reg_left, reg_right, shift, mask, invert)



A stereo control spanning 2 registers

::



    #define SOC_ENUM_SINGLE(xreg, xshift, xmask, xtexts)



Defines an single enumerated control as follows:-

::



   xreg = register

   xshift = control bit(s) offset in register
@@ -109,9 +117,10 @@ Defines an single enumerated control as follows:- 
Defines a stereo enumerated control





4 - Codec Audio Operations

--------------------------

Codec Audio Operations

----------------------

The codec driver also supports the following ALSA PCM operations:-

::



  /* SoC audio ops */

  struct snd_soc_ops {
@@ -126,8 +135,8 @@ Please refer to the ALSA driver PCM documentation for details. 
http://www.alsa-project.org/~iwai/writing-an-alsa-driver/





5 - DAPM description.

---------------------

DAPM description

----------------

The Dynamic Audio Power Management description describes the codec power

components and their relationships and registers to the ASoC core.

Please read dapm.txt for details of building the description.
@@ -135,13 +144,14 @@ Please read dapm.txt for details of building the description. 
Please also see the examples in other codec drivers.





6 - DAPM event handler

----------------------

DAPM event handler

------------------

This function is a callback that handles codec domain PM calls and system

domain PM calls (e.g. suspend and resume). It is used to put the codec

to sleep when not in use.



Power states:-

::



	SNDRV_CTL_POWER_D0: /* full On */

	/* vref/mid, clk and osc on, active */
@@ -155,8 +165,8 @@ Power states:- 
	SNDRV_CTL_POWER_D3cold: /* Everything Off, without power */





7 - Codec DAC digital mute control

----------------------------------

Codec DAC digital mute control

------------------------------

Most codecs have a digital mute before the DACs that can be used to

minimise any system noise.  The mute stops any digital data from

entering the DAC.
@@ -165,6 +175,7 @@ A callback can be created that is called by the core for each codec DAI 
when the mute is applied or freed.



i.e.

::



  static int wm8974_mute(struct snd_soc_dai *dai, int mute)

  {

Documentation/sound/soc/index.rst

+1 −0
Original line number Diff line number Diff line
@@ -8,3 +8,4 @@ The documentation is spilt into the following sections:- 
   :maxdepth: 2



   overview

   codec