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Diffstat (limited to 'Documentation/sound/alsa/soc/codec.txt')
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diff --git a/Documentation/sound/alsa/soc/codec.txt b/Documentation/sound/alsa/soc/codec.txt deleted file mode 100644 index db5f9c9ae149..000000000000 --- a/Documentation/sound/alsa/soc/codec.txt +++ /dev/null @@ -1,179 +0,0 @@ -ASoC Codec Class Driver -======================= - -The codec class driver is generic and hardware independent code that configures -the codec, FM, MODEM, BT or external DSP to provide audio capture and playback. -It should contain no code that is specific to the target platform or machine. -All platform and machine specific code should be added to the platform and -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. - -Optionally, codec drivers can also provide:- - - 7) DAC Digital mute control. - -Its probably best to use this guide in conjunction with the existing codec -driver code in sound/soc/codecs/ - -ASoC Codec driver breakdown -=========================== - -1 - 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, - .hw_params = wm8731_hw_params, - .shutdown = wm8731_shutdown, - .digital_mute = wm8731_mute, - .set_sysclk = wm8731_set_dai_sysclk, - .set_fmt = wm8731_set_dai_fmt, -}; - -struct snd_soc_dai_driver wm8731_dai = { - .name = "wm8731-hifi", - .playback = { - .stream_name = "Playback", - .channels_min = 1, - .channels_max = 2, - .rates = WM8731_RATES, - .formats = WM8731_FORMATS,}, - .capture = { - .stream_name = "Capture", - .channels_min = 1, - .channels_max = 2, - .rates = WM8731_RATES, - .formats = WM8731_FORMATS,}, - .ops = &wm8731_dai_ops, - .symmetric_rates = 1, -}; - - -2 - 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 ------------------------------ -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 - shift = control bit(s) offset in register - mask = control bit size(s) e.g. mask of 7 = 3 bits - 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 - xmask = control bit(s) size - xtexts = pointer to array of strings that describe each setting - - #define SOC_ENUM_DOUBLE(xreg, xshift_l, xshift_r, xmask, xtexts) - -Defines a stereo enumerated control - - -4 - Codec Audio Operations --------------------------- -The codec driver also supports the following ALSA PCM 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 *); -}; - -Please refer to the ALSA driver PCM documentation for details. -http://www.alsa-project.org/~iwai/writing-an-alsa-driver/ - - -5 - 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. - -Please also see the examples in other codec drivers. - - -6 - 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 */ - - SNDRV_CTL_POWER_D1: /* partial On */ - SNDRV_CTL_POWER_D2: /* partial On */ - - SNDRV_CTL_POWER_D3hot: /* Off, with power */ - /* everything off except vref/vmid, inactive */ - - SNDRV_CTL_POWER_D3cold: /* Everything Off, without power */ - - -7 - 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. - -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) -{ - struct snd_soc_codec *codec = dai->codec; - u16 mute_reg = snd_soc_read(codec, WM8974_DAC) & 0xffbf; - - if (mute) - snd_soc_write(codec, WM8974_DAC, mute_reg | 0x40); - else - snd_soc_write(codec, WM8974_DAC, mute_reg); - return 0; -} |