ALSA driver---DAPM flow
参考：
https://elixir.bootlin.com/linux/v4.9.218/source/sound/soc/soc-dapm.c#L804
https://blog.csdn.net/DroidPhone/article/details/14146319
https://blog.csdn.net/DroidPhone/article/details/14052861
https://blog.csdn.net/whshiyun/article/details/80889838
定义widget
There are 4 power domains within DAPM:
- Codec domain – VREF, VMID (core codec and audio power). Usually controlled at codec probe/remove and suspend/resume, although can be set at stream time if power is not needed for sidetone, etc.
- Platform/Machine domain – physically connected inputs and outputs. Is platform/machine and user action specific, is configured by the machine driver and responds to asynchronous events. e.g when HP are inserted
- Path domain – audio subsystem signal paths. Automatically set when mixer and mux settings are changed by the user. e.g. alsamixer, amixer.
- Stream domain – DAC's and ADC's. Enabled and disabled when stream playback/capture is started and stopped respectively. e.g. aplay, arecord.
DAPM框架为我们提供了大量的辅助宏用来定义各种各样的widget控件.
widget 结构体如下：
* dapm widget */
struct snd_soc_dapm_widget {
enum snd_soc_dapm_type id;
const char *name; /* widget name */
const char *sname; /* stream name */
struct list_head list;
struct snd_soc_dapm_context *dapm;
void *priv; /* widget specific data */
struct regulator *regulator; /* attached regulator */
const struct snd_soc_pcm_stream *params; /* params for dai links */
unsigned int num_params; /* number of params for dai links */
unsigned int params_select; /* currently selected param for dai link */
/* dapm control */
int reg; /* negative reg = no direct dapm */
unsigned char shift; /* bits to shift */
unsigned int mask; /* non-shifted mask */
unsigned int on_val; /* on state value */
unsigned int off_val; /* off state value */
unsigned char power:1; /* block power status */
unsigned char active:1; /* active stream on DAC, ADC's */
unsigned char connected:1; /* connected codec pin */
unsigned char new:1; /* cnew complete */
unsigned char force:1; /* force state */
unsigned char ignore_suspend:1; /* kept enabled over suspend */
unsigned char new_power:1; /* power from this run */
unsigned char power_checked:1; /* power checked this run */
unsigned char is_supply:1; /* Widget is a supply type widget */
unsigned char is_ep:2; /* Widget is a endpoint type widget */
int subseq; /* sort within widget type */
int (*power_check)(struct snd_soc_dapm_widget *w);
/* external events */
unsigned short event_flags; /* flags to specify event types */
int (*event)(struct snd_soc_dapm_widget*, struct snd_kcontrol *, int);
/* kcontrols that relate to this widget */
int num_kcontrols;
const struct snd_kcontrol_new *kcontrol_news;
struct snd_kcontrol **kcontrols;
struct snd_soc_dobj dobj;
/* widget input and output edges */
struct list_head edges[2];
/* used during DAPM updates */
struct list_head work_list;
struct list_head power_list;
struct list_head dirty;
int endpoints[2];
struct clk *clk;
};
widget的type:
/* dapm widget types */
enum snd_soc_dapm_type {
snd_soc_dapm_input = 0, /* input pin */
snd_soc_dapm_output, /* output pin */
snd_soc_dapm_mux, /* selects 1 analog signal from many inputs */
snd_soc_dapm_demux, /* connects the input to one of multiple outputs */
snd_soc_dapm_mixer, /* mixes several analog signals together */
snd_soc_dapm_mixer_named_ctl, /* mixer with named controls */
snd_soc_dapm_pga, /* programmable gain/attenuation (volume) */
snd_soc_dapm_out_drv, /* output driver */
snd_soc_dapm_adc, /* analog to digital converter */
snd_soc_dapm_dac, /* digital to analog converter */
snd_soc_dapm_micbias, /* microphone bias (power) - DEPRECATED: use snd_soc_dapm_supply */
snd_soc_dapm_mic, /* microphone */
snd_soc_dapm_hp, /* headphones */
snd_soc_dapm_spk, /* speaker */
snd_soc_dapm_line, /* line input/output */
snd_soc_dapm_switch, /* analog switch */
snd_soc_dapm_vmid, /* codec bias/vmid - to minimise pops */
snd_soc_dapm_pre, /* machine specific pre widget - exec first */
snd_soc_dapm_post, /* machine specific post widget - exec last */
snd_soc_dapm_supply, /* power/clock supply */
snd_soc_dapm_regulator_supply, /* external regulator */
snd_soc_dapm_clock_supply, /* external clock */
snd_soc_dapm_aif_in, /* audio interface input */
snd_soc_dapm_aif_out, /* audio interface output */
snd_soc_dapm_siggen, /* signal generator */
snd_soc_dapm_sink,
snd_soc_dapm_dai_in, /* link to DAI structure */
snd_soc_dapm_dai_out,
snd_soc_dapm_dai_link, /* link between two DAI structures */
snd_soc_dapm_kcontrol, /* Auto-disabled kcontrol */
};
codec domain:
/* codec domain */
#define SND_SOC_DAPM_VMID(wname) \
{ .id = snd_soc_dapm_vmid, .name = wname, .kcontrol_news = NULL, \
.num_kcontrols = 0}
platform domain:
platform domain的widget分别对应信号发生器，输入引脚，输出引脚，麦克风，耳机，扬声器，线路输入接口。其中的reg字段被设置为SND_SOC_NOPM（-1），表明这些widget是没有寄存器控制位来控制widget的电源状态的。麦克风，耳机，扬声器，线路输入接口这几种widget，还可以定义一个dapm事件回调函数wevent，从event_flags字段的设置可以看出，他们只会响应SND_SOC_DAPM_POST_PMU（上电后）和SND_SOC_DAPM_PMD（下电前）事件，这几个widget通常会在machine驱动中定义，而SND_SOC_DAPM_INPUT和SND_SOC_DAPM_OUTPUT则用来定义codec芯片的输出输入脚，通常在codec驱动中定义，最后，在machine驱动中增加相应的route，把麦克风和耳机等widget与相应的codec输入输出引脚的widget连接起来。
/* platform domain */
#define SND_SOC_DAPM_SIGGEN(wname) \
{ .id = snd_soc_dapm_siggen, .name = wname, .kcontrol_news = NULL, \
.num_kcontrols = 0, .reg = SND_SOC_NOPM }
#define SND_SOC_DAPM_SINK(wname) \
{ .id = snd_soc_dapm_sink, .name = wname, .kcontrol_news = NULL, \
.num_kcontrols = 0, .reg = SND_SOC_NOPM }
#define SND_SOC_DAPM_INPUT(wname) \
{ .id = snd_soc_dapm_input, .name = wname, .kcontrol_news = NULL, \
.num_kcontrols = 0, .reg = SND_SOC_NOPM }
#define SND_SOC_DAPM_OUTPUT(wname) \
{ .id = snd_soc_dapm_output, .name = wname, .kcontrol_news = NULL, \
.num_kcontrols = 0, .reg = SND_SOC_NOPM }
#define SND_SOC_DAPM_MIC(wname, wevent) \
{ .id = snd_soc_dapm_mic, .name = wname, .kcontrol_news = NULL, \
.num_kcontrols = 0, .reg = SND_SOC_NOPM, .event = wevent, \
.event_flags = SND_SOC_DAPM_PRE_PMU | SND_SOC_DAPM_POST_PMD}
#define SND_SOC_DAPM_HP(wname, wevent) \
{ .id = snd_soc_dapm_hp, .name = wname, .kcontrol_news = NULL, \
.num_kcontrols = 0, .reg = SND_SOC_NOPM, .event = wevent, \
.event_flags = SND_SOC_DAPM_POST_PMU | SND_SOC_DAPM_PRE_PMD}
#define SND_SOC_DAPM_SPK(wname, wevent) \
{ .id = snd_soc_dapm_spk, .name = wname, .kcontrol_news = NULL, \
.num_kcontrols = 0, .reg = SND_SOC_NOPM, .event = wevent, \
.event_flags = SND_SOC_DAPM_POST_PMU | SND_SOC_DAPM_PRE_PMD}
#define SND_SOC_DAPM_LINE(wname, wevent) \
{ .id = snd_soc_dapm_line, .name = wname, .kcontrol_news = NULL, \
.num_kcontrols = 0, .reg = SND_SOC_NOPM, .event = wevent, \
.event_flags = SND_SOC_DAPM_POST_PMU | SND_SOC_DAPM_PRE_PMD}
path domain:
path domain 的widget通常是对普通kcontrols控件的再封装，增加音频路径和电源管理功能，所以这种widget会包含一个或多个kcontrol，这些widget的reg和shift字段是需要赋值的，说明这些widget是有相应的电源控制寄存器的，DAPM框架在扫描和更新音频路径时，会利用这些寄存器来控制widget的电源状态，使得它们的供电状态是按需分配的，需要的时候（在有效的音频路径上）上电，不需要的时候（不再有效的音频路径上）下电。
#define SND_SOC_DAPM_INIT_REG_VAL(wreg, wshift, winvert) \
.reg = wreg, .mask = 1, .shift = wshift, \
.on_val = winvert ? 0 : 1, .off_val = winvert ? 1 : 0
/* path domain */
#define SND_SOC_DAPM_PGA(wname, wreg, wshift, winvert,\
wcontrols, wncontrols) \
{ .id = snd_soc_dapm_pga, .name = wname, \
SND_SOC_DAPM_INIT_REG_VAL(wreg, wshift, winvert), \
.kcontrol_news = wcontrols, .num_kcontrols = wncontrols}
#define SND_SOC_DAPM_OUT_DRV(wname, wreg, wshift, winvert,\
wcontrols, wncontrols) \
{ .id = snd_soc_dapm_out_drv, .name = wname, \
SND_SOC_DAPM_INIT_REG_VAL(wreg, wshift, winvert), \
.kcontrol_news = wcontrols, .num_kcontrols = wncontrols}
#define SND_SOC_DAPM_MIXER(wname, wreg, wshift, winvert, \
wcontrols, wncontrols)\
{ .id = snd_soc_dapm_mixer, .name = wname, \
SND_SOC_DAPM_INIT_REG_VAL(wreg, wshift, winvert), \
.kcontrol_news = wcontrols, .num_kcontrols = wncontrols}
#define SND_SOC_DAPM_MIXER_NAMED_CTL(wname, wreg, wshift, winvert, \
wcontrols, wncontrols)\
{ .id = snd_soc_dapm_mixer_named_ctl, .name = wname, \
SND_SOC_DAPM_INIT_REG_VAL(wreg, wshift, winvert), \
.kcontrol_news = wcontrols, .num_kcontrols = wncontrols}
/* DEPRECATED: use SND_SOC_DAPM_SUPPLY */
#define SND_SOC_DAPM_MICBIAS(wname, wreg, wshift, winvert) \
{ .id = snd_soc_dapm_micbias, .name = wname, \
SND_SOC_DAPM_INIT_REG_VAL(wreg, wshift, winvert), \
.kcontrol_news = NULL, .num_kcontrols = 0}
#define SND_SOC_DAPM_SWITCH(wname, wreg, wshift, winvert, wcontrols) \
{ .id = snd_soc_dapm_switch, .name = wname, \
SND_SOC_DAPM_INIT_REG_VAL(wreg, wshift, winvert), \
.kcontrol_news = wcontrols, .num_kcontrols = 1}
#define SND_SOC_DAPM_MUX(wname, wreg, wshift, winvert, wcontrols) \
{ .id = snd_soc_dapm_mux, .name = wname, \
SND_SOC_DAPM_INIT_REG_VAL(wreg, wshift, winvert), \
.kcontrol_news = wcontrols, .num_kcontrols = 1}
#define SND_SOC_DAPM_DEMUX(wname, wreg, wshift, winvert, wcontrols) \
{ .id = snd_soc_dapm_demux, .name = wname, \
SND_SOC_DAPM_INIT_REG_VAL(wreg, wshift, winvert), \
.kcontrol_news = wcontrols, .num_kcontrols = 1}
这些widget需要完成和的mixer、mux等控件同样的功能，实际上，这是通过它们包含的kcontrol控件来完成的，这些kcontrol我们需要在定义widget前先定义好，然后通过wcontrols和num_kcontrols参数传递给这些辅助定义宏。dapm利用这些kcontrol完成音频路径的控制。不过，对于widget来说，它的任务还不止这些，dapm还要动态地管理这些音频路径的连结关系，以便可以根据这些连接关系来控制这些widget的电源状态，如果按照普通的方法定义这些kcontrol，是无法达到这个目的的，因此，dapm为我们提供了另外一套定义宏，由它们完成这些被widget包含的kcontrol的定义。
/* dapm kcontrol types */
#define SOC_DAPM_SINGLE(xname, reg, shift, max, invert) \
{ .iface = SNDRV_CTL_ELEM_IFACE_MIXER, .name = xname, \
.info = snd_soc_info_volsw, \
.get = snd_soc_dapm_get_volsw, .put = snd_soc_dapm_put_volsw, \
.private_value = SOC_SINGLE_VALUE(reg, shift, max, invert, 0) }
#define SOC_DAPM_SINGLE_AUTODISABLE(xname, reg, shift, max, invert) \
{ .iface = SNDRV_CTL_ELEM_IFACE_MIXER, .name = xname, \
.info = snd_soc_info_volsw, \
.get = snd_soc_dapm_get_volsw, .put = snd_soc_dapm_put_volsw, \
.private_value = SOC_SINGLE_VALUE(reg, shift, max, invert, 1) }
#define SOC_DAPM_SINGLE_VIRT(xname, max) \
SOC_DAPM_SINGLE(xname, SND_SOC_NOPM, 0, max, 0)
#define SOC_DAPM_SINGLE_TLV(xname, reg, shift, max, invert, tlv_array) \
{ .iface = SNDRV_CTL_ELEM_IFACE_MIXER, .name = xname, \
.info = snd_soc_info_volsw, \
.access = SNDRV_CTL_ELEM_ACCESS_TLV_READ | SNDRV_CTL_ELEM_ACCESS_READWRITE,\
.tlv.p = (tlv_array), \
.get = snd_soc_dapm_get_volsw, .put = snd_soc_dapm_put_volsw, \
.private_value = SOC_SINGLE_VALUE(reg, shift, max, invert, 0) }
#define SOC_DAPM_SINGLE_TLV_AUTODISABLE(xname, reg, shift, max, invert, tlv_array) \
{ .iface = SNDRV_CTL_ELEM_IFACE_MIXER, .name = xname, \
.info = snd_soc_info_volsw, \
.access = SNDRV_CTL_ELEM_ACCESS_TLV_READ | SNDRV_CTL_ELEM_ACCESS_READWRITE,\
.tlv.p = (tlv_array), \
.get = snd_soc_dapm_get_volsw, .put = snd_soc_dapm_put_volsw, \
.private_value = SOC_SINGLE_VALUE(reg, shift, max, invert, 1) }
#define SOC_DAPM_SINGLE_TLV_VIRT(xname, max, tlv_array) \
SOC_DAPM_SINGLE(xname, SND_SOC_NOPM, 0, max, 0, tlv_array)
#define SOC_DAPM_ENUM(xname, xenum) \
{ .iface = SNDRV_CTL_ELEM_IFACE_MIXER, .name = xname, \
.info = snd_soc_info_enum_double, \
.get = snd_soc_dapm_get_enum_double, \
.put = snd_soc_dapm_put_enum_double, \
.private_value = (unsigned long)&xenum }
#define SOC_DAPM_ENUM_EXT(xname, xenum, xget, xput) \
{ .iface = SNDRV_CTL_ELEM_IFACE_MIXER, .name = xname, \
.info = snd_soc_info_enum_double, \
.get = xget, \
.put = xput, \
.private_value = (unsigned long)&xenum }
#define SOC_DAPM_PIN_SWITCH(xname) \
{ .iface = SNDRV_CTL_ELEM_IFACE_MIXER, .name = xname " Switch", \
.info = snd_soc_dapm_info_pin_switch, \
.get = snd_soc_dapm_get_pin_switch, \
.put = snd_soc_dapm_put_pin_switch, \
.private_value = (unsigned long)xname }
可以看出，SOC_DAPM_SINGLE对应与普通控件的SOC_SINGLE，SOC_DAPM_SINGLE_TLV对应SOC_SINGLE_TLV......，相比普通的kcontrol控件，dapm的kcontrol控件只是把info，get，put回调函数换掉了。dapm kcontrol的put回调函数不仅仅会更新控件本身的状态，他还会把这种变化传递到相邻的dapm kcontrol，相邻的dapm kcontrol又会传递这个变化到他自己相邻的dapm kcontrol，直到音频路径的末端，通过这种机制，只要改变其中一个widget的连接状态，与之相关的所有widget都会被扫描并测试一下自身是否还在有效的音频路径中，从而可以动态地改变自身的电源状态，这就是dapm的精髓所在。
stream domain:
这些widget主要包含音频输入/输出接口，ADC/DAC等等：
/* stream domain */
#define SND_SOC_DAPM_AIF_IN(wname, stname, wslot, wreg, wshift, winvert) \
{ .id = snd_soc_dapm_aif_in, .name = wname, .sname = stname, \
SND_SOC_DAPM_INIT_REG_VAL(wreg, wshift, winvert), }
#define SND_SOC_DAPM_AIF_IN_E(wname, stname, wslot, wreg, wshift, winvert, \
wevent, wflags) \
{ .id = snd_soc_dapm_aif_in, .name = wname, .sname = stname, \
SND_SOC_DAPM_INIT_REG_VAL(wreg, wshift, winvert), \
.event = wevent, .event_flags = wflags }
#define SND_SOC_DAPM_AIF_OUT(wname, stname, wslot, wreg, wshift, winvert) \
{ .id = snd_soc_dapm_aif_out, .name = wname, .sname = stname, \
SND_SOC_DAPM_INIT_REG_VAL(wreg, wshift, winvert), }
#define SND_SOC_DAPM_AIF_OUT_E(wname, stname, wslot, wreg, wshift, winvert, \
wevent, wflags) \
{ .id = snd_soc_dapm_aif_out, .name = wname, .sname = stname, \
SND_SOC_DAPM_INIT_REG_VAL(wreg, wshift, winvert), \
.event = wevent, .event_flags = wflags }
#define SND_SOC_DAPM_DAC(wname, stname, wreg, wshift, winvert) \
{ .id = snd_soc_dapm_dac, .name = wname, .sname = stname, \
SND_SOC_DAPM_INIT_REG_VAL(wreg, wshift, winvert) }
#define SND_SOC_DAPM_DAC_E(wname, stname, wreg, wshift, winvert, \
wevent, wflags) \
{ .id = snd_soc_dapm_dac, .name = wname, .sname = stname, \
SND_SOC_DAPM_INIT_REG_VAL(wreg, wshift, winvert), \
.event = wevent, .event_flags = wflags}
#define SND_SOC_DAPM_ADC(wname, stname, wreg, wshift, winvert) \
{ .id = snd_soc_dapm_adc, .name = wname, .sname = stname, \
SND_SOC_DAPM_INIT_REG_VAL(wreg, wshift, winvert), }
#define SND_SOC_DAPM_ADC_E(wname, stname, wreg, wshift, winvert, \
wevent, wflags) \
{ .id = snd_soc_dapm_adc, .name = wname, .sname = stname, \
SND_SOC_DAPM_INIT_REG_VAL(wreg, wshift, winvert), \
.event = wevent, .event_flags = wflags}
#define SND_SOC_DAPM_CLOCK_SUPPLY(wname) \
{ .id = snd_soc_dapm_clock_supply, .name = wname, \
.reg = SND_SOC_NOPM, .event = dapm_clock_event, \
.event_flags = SND_SOC_DAPM_PRE_PMU | SND_SOC_DAPM_POST_PMD }
定义route
route 表示widget的连接路径(Destination Widget <=== Path Name <=== Source Widget)。route结构体如下:
/*
* DAPM audio route definition.
*
* Defines an audio route originating at source via control and finishing
* at sink.
*/
struct snd_soc_dapm_route {
const char *sink;
const char *control;
const char *source;
/* Note: currently only supported for links where source is a supply */
int (*connected)(struct snd_soc_dapm_widget *source,
struct snd_soc_dapm_widget *sink);
};
以sound/soc/codecs/tlv320aic23.c 为例，以下是tlv320 codec driver定义的widget定义的widgets和route
DAPM Widgets:
static const struct snd_soc_dapm_widget tlv320aic23_dapm_widgets[] = {
SND_SOC_DAPM_DAC("DAC", "Playback", TLV320AIC23_PWR, 3, 1),
SND_SOC_DAPM_ADC("ADC", "Capture", TLV320AIC23_PWR, 2, 1),
SND_SOC_DAPM_MUX("Capture Source", SND_SOC_NOPM, 0, 0,
&tlv320aic23_rec_src_mux_controls),
SND_SOC_DAPM_MIXER("Output Mixer", TLV320AIC23_PWR, 4, 1,
&tlv320aic23_output_mixer_controls[0],
ARRAY_SIZE(tlv320aic23_output_mixer_controls)),
SND_SOC_DAPM_PGA("Line Input", TLV320AIC23_PWR, 0, 1, NULL, 0),
SND_SOC_DAPM_PGA("Mic Input", TLV320AIC23_PWR, 1, 1, NULL, 0),
SND_SOC_DAPM_OUTPUT("LHPOUT"),
SND_SOC_DAPM_OUTPUT("RHPOUT"),
SND_SOC_DAPM_OUTPUT("LOUT"),
SND_SOC_DAPM_OUTPUT("ROUT"),
SND_SOC_DAPM_INPUT("LLINEIN"),
SND_SOC_DAPM_INPUT("RLINEIN"),
SND_SOC_DAPM_INPUT("MICIN"),
};
widget kcontrol:
/* PGA Mixer controls for Line and Mic switch */
static const struct snd_kcontrol_new tlv320aic23_output_mixer_controls[] = {
SOC_DAPM_SINGLE("Line Bypass Switch", TLV320AIC23_ANLG, 3, 1, 0),
SOC_DAPM_SINGLE("Mic Sidetone Switch", TLV320AIC23_ANLG, 5, 1, 0),
SOC_DAPM_SINGLE("Playback Switch", TLV320AIC23_ANLG, 4, 1, 0),
};
DAPM routes:
static const struct snd_soc_dapm_route tlv320aic23_intercon[] = {
/* Output Mixer */
{"Output Mixer", "Line Bypass Switch", "Line Input"},
{"Output Mixer", "Playback Switch", "DAC"},
{"Output Mixer", "Mic Sidetone Switch", "Mic Input"},
/* Outputs */
{"RHPOUT", NULL, "Output Mixer"},
{"LHPOUT", NULL, "Output Mixer"},
{"LOUT", NULL, "Output Mixer"},
{"ROUT", NULL, "Output Mixer"},
/* Inputs */
{"Line Input", "NULL", "LLINEIN"},
{"Line Input", "NULL", "RLINEIN"},
{"Mic Input", "NULL", "MICIN"},
/* input mux */
{"Capture Source", "Line", "Line Input"},
{"Capture Source", "Mic", "Mic Input"},
{"ADC", NULL, "Capture Source"},
};
capture audio path:
LLININ->Line Input->Catpture source ->ADC
MICIN->Mic Input->Catpute source->ADC
playback audio path:
DAC->Ouptput Mixer->LOUT/LHPOUT/ROUT/RHPOUT
LLININ->Line Input->Output Mixer->LOUT
MICIN->Mic Input ->Output Mixer->LOUT/LHPOUT/ROUT/RHPOUT
创建widget和path:
DAPM widget和route定义在CPU DAI driver和Codec driver的component driver.当调用snd_soc_register_component()注册CPU DAI ， 调用snd_soc_register_codec()注册Codec时，都会创建snd_soc_component类型的component, 并调用snd_soc_component_initialize()将component driver中定义的widgets和route赋值给component。
在snd_soc_instantiate_card()会调用soc_probe_link_component()->soc_probe_component()来probe component.
static int soc_probe_component(struct snd_soc_card *card,
struct snd_soc_component *component)
{
struct snd_soc_dapm_context *dapm = snd_soc_component_get_dapm(component);
struct snd_soc_dai *dai;
int ret;
if (!strcmp(component->name, "snd-soc-dummy"))
return 0;
if (component->card) {
if (component->card != card) {
dev_err(component->dev,
"Trying to bind component to card \"%s\" but is already bound to card \"%s\"\n",
card->name, component->card->name);
return -ENODEV;
}
return 0;
}
if (!try_module_get(component->dev->driver->owner))
return -ENODEV;
component->card = card;
dapm->card = card;
soc_set_name_prefix(card, component);
soc_init_component_debugfs(component);
if (component->dapm_widgets) {
ret = snd_soc_dapm_new_controls(dapm, component->dapm_widgets,
component->num_dapm_widgets);
if (ret != 0) {
dev_err(component->dev,
"Failed to create new controls %d\n", ret);
goto err_probe;
}
}
list_for_each_entry(dai, &component->dai_list, list) {
ret = snd_soc_dapm_new_dai_widgets(dapm, dai);
if (ret != 0) {
dev_err(component->dev,
"Failed to create DAI widgets %d\n", ret);
goto err_probe;
}
}
if (component->probe) {
ret = component->probe(component);
if (ret < 0) {
dev_err(component->dev,
"ASoC: failed to probe component %d\n", ret);
goto err_probe;
}
WARN(dapm->idle_bias_off &&
dapm->bias_level != SND_SOC_BIAS_OFF,
"codec %s can not start from non-off bias with idle_bias_off==1\n",
component->name);
}
/* machine specific init */
if (component->init) {
ret = component->init(component);
if (ret < 0) {
dev_err(component->dev,
"Failed to do machine specific init %d\n", ret);
goto err_probe;
}
}
if (component->controls)
snd_soc_add_component_controls(component, component->controls,
component->num_controls);
if (component->dapm_routes)
snd_soc_dapm_add_routes(dapm, component->dapm_routes,
component->num_dapm_routes);
list_add(&dapm->list, &card->dapm_list);
/* This is a HACK and will be removed soon */
if (component->codec)
list_add(&component->codec->card_list, &card->codec_dev_list);
return 0;
err_probe:
soc_cleanup_component_debugfs(component);
component->card = NULL;
module_put(component->dev->driver->owner);
return ret;
}
在soc_probe_component()里面，
调用snd_soc_dapm_new_controls()对component->dapm_widgets中每个widget创建新的widget,将widget加到card->widgets链表中。该函数只是简单的一个循环，为传入的widget模板数组依次调用snd_soc_dapm_new_control函数，实际的工作由snd_soc_dapm_new_control完成
/**
* snd_soc_dapm_new_controls - create new dapm controls
* @dapm: DAPM context
* @widget: widget array
* @num: number of widgets
*
* Creates new DAPM controls based upon the templates.
*
* Returns 0 for success else error.
*/
int snd_soc_dapm_new_controls(struct snd_soc_dapm_context *dapm,
const struct snd_soc_dapm_widget *widget,
int num)
{
struct snd_soc_dapm_widget *w;
int i;
int ret = 0;
mutex_lock_nested(&dapm->card->dapm_mutex, SND_SOC_DAPM_CLASS_INIT);
for (i = 0; i < num; i++) {
w = snd_soc_dapm_new_control_unlocked(dapm, widget);
if (IS_ERR(w)) {
ret = PTR_ERR(w);
/* Do not nag about probe deferrals */
if (ret == -EPROBE_DEFER)
break;
dev_err(dapm->dev,
"ASoC: Failed to create DAPM control %s (%d)\n",
widget->name, ret);
break;
}
if (!w) {
dev_err(dapm->dev,
"ASoC: Failed to create DAPM control %s\n",
widget->name);
ret = -ENOMEM;
break;
}
widget++;
}
mutex_unlock(&dapm->card->dapm_mutex);
return ret;
}
创建widget由snd_soc_dapm_new_control_unlocked()完成,在此函数中调用dapm_cnew_widget()对widget分配内存,设定widget的power_check()函数(为不同类型的widget设置合适的power_check电源状态回调函数, 当音频路径发生变化时，power_check回调会被调用，用于检查该widget的电源状态是否需要更新)，最后将创建的widget加到card->widget链表中。
struct snd_soc_dapm_widget *
snd_soc_dapm_new_control_unlocked(struct snd_soc_dapm_context *dapm,
const struct snd_soc_dapm_widget *widget)
{
enum snd_soc_dapm_direction dir;
struct snd_soc_dapm_widget *w;
const char *prefix;
int ret;
if ((w = dapm_cnew_widget(widget)) == NULL)
return NULL;
switch (w->id) {
case snd_soc_dapm_regulator_supply:
w->regulator = devm_regulator_get(dapm->dev, w->name);
if (IS_ERR(w->regulator)) {
ret = PTR_ERR(w->regulator);
if (ret == -EPROBE_DEFER)
return ERR_PTR(ret);
dev_err(dapm->dev, "ASoC: Failed to request %s: %d\n",
w->name, ret);
return NULL;
}
if (w->on_val & SND_SOC_DAPM_REGULATOR_BYPASS) {
ret = regulator_allow_bypass(w->regulator, true);
if (ret != 0)
dev_warn(w->dapm->dev,
"ASoC: Failed to bypass %s: %d\n",
w->name, ret);
}
break;
case snd_soc_dapm_clock_supply:
#ifdef CONFIG_CLKDEV_LOOKUP
w->clk = devm_clk_get(dapm->dev, w->name);
if (IS_ERR(w->clk)) {
ret = PTR_ERR(w->clk);
if (ret == -EPROBE_DEFER)
return ERR_PTR(ret);
dev_err(dapm->dev, "ASoC: Failed to request %s: %d\n",
w->name, ret);
return NULL;
}
#else
return NULL;
#endif
break;
default:
break;
}
prefix = soc_dapm_prefix(dapm);
if (prefix)
w->name = kasprintf(GFP_KERNEL, "%s %s", prefix, widget->name);
else
w->name = kstrdup_const(widget->name, GFP_KERNEL);
if (w->name == NULL) {
kfree(w);
return NULL;
}
switch (w->id) {
case snd_soc_dapm_mic:
w->is_ep = SND_SOC_DAPM_EP_SOURCE;
w->power_check = dapm_generic_check_power;
break;
case snd_soc_dapm_input:
if (!dapm->card->fully_routed)
w->is_ep = SND_SOC_DAPM_EP_SOURCE;
w->power_check = dapm_generic_check_power;
break;
case snd_soc_dapm_spk:
case snd_soc_dapm_hp:
w->is_ep = SND_SOC_DAPM_EP_SINK;
w->power_check = dapm_generic_check_power;
break;
case snd_soc_dapm_output:
if (!dapm->card->fully_routed)
w->is_ep = SND_SOC_DAPM_EP_SINK;
w->power_check = dapm_generic_check_power;
break;
case snd_soc_dapm_vmid:
case snd_soc_dapm_siggen:
w->is_ep = SND_SOC_DAPM_EP_SOURCE;
w->power_check = dapm_always_on_check_power;
break;
case snd_soc_dapm_sink:
w->is_ep = SND_SOC_DAPM_EP_SINK;
w->power_check = dapm_always_on_check_power;
break;
case snd_soc_dapm_mux:
case snd_soc_dapm_demux:
case snd_soc_dapm_switch:
case snd_soc_dapm_mixer:
case snd_soc_dapm_mixer_named_ctl:
case snd_soc_dapm_adc:
case snd_soc_dapm_aif_out:
case snd_soc_dapm_dac:
case snd_soc_dapm_aif_in:
case snd_soc_dapm_pga:
case snd_soc_dapm_out_drv:
case snd_soc_dapm_micbias:
case snd_soc_dapm_line:
case snd_soc_dapm_dai_link:
case snd_soc_dapm_dai_out:
case snd_soc_dapm_dai_in:
w->power_check = dapm_generic_check_power;
break;
case snd_soc_dapm_supply:
case snd_soc_dapm_regulator_supply:
case snd_soc_dapm_clock_supply:
case snd_soc_dapm_kcontrol:
w->is_supply = 1;
w->power_check = dapm_supply_check_power;
break;
default:
w->power_check = dapm_always_on_check_power;
break;
}
w->dapm = dapm;
INIT_LIST_HEAD(&w->list);
INIT_LIST_HEAD(&w->dirty);
list_add_tail(&w->list, &dapm->card->widgets);
snd_soc_dapm_for_each_direction(dir) {
INIT_LIST_HEAD(&w->edges[dir]);
w->endpoints[dir] = -1;
}
/* machine layer sets up unconnected pins and insertions */
w->connected = 1;
return w;
}
基于component->dai_list中的dai 通过调用snd_soc_dapm_new_dai_widgets()创建dai widget，也将此widget加到card->widgets链表中。
在创建的widget中，其name和sname都是dai driver中的stream name，后面的链接时会去匹配这个名字.
int snd_soc_dapm_new_dai_widgets(struct snd_soc_dapm_context *dapm,
struct snd_soc_dai *dai)
{
struct snd_soc_dapm_widget template;
struct snd_soc_dapm_widget *w;
WARN_ON(dapm->dev != dai->dev);
memset(&template, 0, sizeof(template));
template.reg = SND_SOC_NOPM;
if (dai->driver->playback.stream_name) {
template.id = snd_soc_dapm_dai_in;
template.name = dai->driver->playback.stream_name;
template.sname = dai->driver->playback.stream_name;
dev_dbg(dai->dev, "ASoC: adding %s widget\n",
template.name);
w = snd_soc_dapm_new_control_unlocked(dapm, &template);
if (IS_ERR(w)) {
int ret = PTR_ERR(w);
/* Do not nag about probe deferrals */
if (ret != -EPROBE_DEFER)
dev_err(dapm->dev,
"ASoC: Failed to create %s widget (%d)\n",
dai->driver->playback.stream_name, ret);
return ret;
}
if (!w) {
dev_err(dapm->dev, "ASoC: Failed to create %s widget\n",
dai->driver->playback.stream_name);
return -ENOMEM;
}
w->priv = dai;
dai->playback_widget = w;
}
if (dai->driver->capture.stream_name) {
template.id = snd_soc_dapm_dai_out;
template.name = dai->driver->capture.stream_name;
template.sname = dai->driver->capture.stream_name;
dev_dbg(dai->dev, "ASoC: adding %s widget\n",
template.name);
w = snd_soc_dapm_new_control_unlocked(dapm, &template);
if (IS_ERR(w)) {
int ret = PTR_ERR(w);
/* Do not nag about probe deferrals */
if (ret != -EPROBE_DEFER)
dev_err(dapm->dev,
"ASoC: Failed to create %s widget (%d)\n",
dai->driver->playback.stream_name, ret);
return ret;
}
if (!w) {
dev_err(dapm->dev, "ASoC: Failed to create %s widget\n",
dai->driver->capture.stream_name);
return -ENOMEM;
}
w->priv = dai;
dai->capture_widget = w;
}
return 0;
}
基于component->dapm_routes创建dapm path,并将创建的path加到card->paths.
如果widget之间没有连接关系，dapm就无法实现动态的电源管理工作，正是widget之间有了连结关系，这些连接关系形成了一条所谓的完成的音频路径，dapm可以顺着这条路径，统一控制路径上所有widget的电源状态，widget之间是使用snd_soc_dapm_path结构进行连接的，驱动要做的是定义一个snd_soc_route结构数组，该数组的每个条目描述了目的widget的和源widget的名称，以及控制这个连接的kcontrol的名称，最终，驱动程序使用api函数snd_soc_dapm_add_routes来注册这些连接信息.
/**
* snd_soc_dapm_add_routes - Add routes between DAPM widgets
* @dapm: DAPM context
* @route: audio routes
* @num: number of routes
*
* Connects 2 dapm widgets together via a named audio path. The sink is
* the widget receiving the audio signal, whilst the source is the sender
* of the audio signal.
*
* Returns 0 for success else error. On error all resources can be freed
* with a call to snd_soc_card_free().
*/
int snd_soc_dapm_add_routes(struct snd_soc_dapm_context *dapm,
const struct snd_soc_dapm_route *route, int num)
{
int i, r, ret = 0;
mutex_lock_nested(&dapm->card->dapm_mutex, SND_SOC_DAPM_CLASS_INIT);
for (i = 0; i < num; i++) {
r = snd_soc_dapm_add_route(dapm, route);
if (r < 0) {
dev_err(dapm->dev, "ASoC: Failed to add route %s -> %s -> %s\n",
route->source,
route->control ? route->control : "direct",
route->sink);
ret = r;
}
route++;
}
mutex_unlock(&dapm->card->dapm_mutex);
return ret;
}
该函数只是一个循环，依次对参数传入的数组调用snd_soc_dapm_add_route，主要的工作由snd_soc_dapm_add_route完成。
static int snd_soc_dapm_add_route(struct snd_soc_dapm_context *dapm,
const struct snd_soc_dapm_route *route)
{
struct snd_soc_dapm_widget *wsource = NULL, *wsink = NULL, *w;
struct snd_soc_dapm_widget *wtsource = NULL, *wtsink = NULL;
const char *sink;
const char *source;
char prefixed_sink[80];
char prefixed_source[80];
const char *prefix;
int ret;
prefix = soc_dapm_prefix(dapm);
if (prefix) {
snprintf(prefixed_sink, sizeof(prefixed_sink), "%s %s",
prefix, route->sink);
sink = prefixed_sink;
snprintf(prefixed_source, sizeof(prefixed_source), "%s %s",
prefix, route->source);
source = prefixed_source;
} else {
sink = route->sink;
source = route->source;
}
wsource = dapm_wcache_lookup(&dapm->path_source_cache, source);
wsink = dapm_wcache_lookup(&dapm->path_sink_cache, sink);
if (wsink && wsource)
goto skip_search;
/*
* find src and dest widgets over all widgets but favor a widget from
* current DAPM context
*/
list_for_each_entry(w, &dapm->card->widgets, list) {
if (!wsink && !(strcmp(w->name, sink))) {
wtsink = w;
if (w->dapm == dapm) {
wsink = w;
if (wsource)
break;
}
continue;
}
if (!wsource && !(strcmp(w->name, source))) {
wtsource = w;
if (w->dapm == dapm) {
wsource = w;
if (wsink)
break;
}
}
}
/* use widget from another DAPM context if not found from this */
if (!wsink)
wsink = wtsink;
if (!wsource)
wsource = wtsource;
if (wsource == NULL) {
dev_err(dapm->dev, "ASoC: no source widget found for %s\n",
route->source);
return -ENODEV;
}
if (wsink == NULL) {
dev_err(dapm->dev, "ASoC: no sink widget found for %s\n",
route->sink);
return -ENODEV;
}
skip_search:
dapm_wcache_update(&dapm->path_sink_cache, wsink);
dapm_wcache_update(&dapm->path_source_cache, wsource);
ret = snd_soc_dapm_add_path(dapm, wsource, wsink, route->control,
route->connected);
if (ret)
goto err;
return 0;
err:
dev_warn(dapm->dev, "ASoC: no dapm match for %s --> %s --> %s\n",
source, route->control, sink);
return ret;
}
snd_soc_dapm_add_route()中用widget的名字来比较，遍历card->widgets链表，找出source widget和sink widget，最后调用snd_soc_dapm_add_path()来创建snd_soc_dapm_path结构体的path，将sourc widget和sink widget赋值给相应的成员，根据source 和sink widget的control(path name) 来初始化path->connect,如果有control，读取path->sink->kcontrol_new的register值来初始化path->connect,最后将path添加到card->paths链表。
static int snd_soc_dapm_add_path(struct snd_soc_dapm_context *dapm,
struct snd_soc_dapm_widget *wsource, struct snd_soc_dapm_widget *wsink,
const char *control,
int (*connected)(struct snd_soc_dapm_widget *source,
struct snd_soc_dapm_widget *sink))
{
struct snd_soc_dapm_widget *widgets[2];
enum snd_soc_dapm_direction dir;
struct snd_soc_dapm_path *path;
int ret;
if (wsink->is_supply && !wsource->is_supply) {
dev_err(dapm->dev,
"Connecting non-supply widget to supply widget is not supported (%s -> %s)\n",
wsource->name, wsink->name);
return -EINVAL;
}
if (connected && !wsource->is_supply) {
dev_err(dapm->dev,
"connected() callback only supported for supply widgets (%s -> %s)\n",
wsource->name, wsink->name);
return -EINVAL;
}
if (wsource->is_supply && control) {
dev_err(dapm->dev,
"Conditional paths are not supported for supply widgets (%s -> [%s] -> %s)\n",
wsource->name, control, wsink->name);
return -EINVAL;
}
ret = snd_soc_dapm_check_dynamic_path(dapm, wsource, wsink, control);
if (ret)
return ret;
path = kzalloc(sizeof(struct snd_soc_dapm_path), GFP_KERNEL);
if (!path)
return -ENOMEM;
path->node[SND_SOC_DAPM_DIR_IN] = wsource;
path->node[SND_SOC_DAPM_DIR_OUT] = wsink;
widgets[SND_SOC_DAPM_DIR_IN] = wsource;
widgets[SND_SOC_DAPM_DIR_OUT] = wsink;
path->connected = connected;
INIT_LIST_HEAD(&path->list);
INIT_LIST_HEAD(&path->list_kcontrol);
if (wsource->is_supply || wsink->is_supply)
path->is_supply = 1;
/* connect static paths */
if (control == NULL) {
path->connect = 1;
} else {
switch (wsource->id) {
case snd_soc_dapm_demux:
ret = dapm_connect_mux(dapm, path, control, wsource);
if (ret)
goto err;
break;
default:
break;
}
switch (wsink->id) {
case snd_soc_dapm_mux:
ret = dapm_connect_mux(dapm, path, control, wsink);
if (ret != 0)
goto err;
break;
case snd_soc_dapm_switch:
case snd_soc_dapm_mixer:
case snd_soc_dapm_mixer_named_ctl:
ret = dapm_connect_mixer(dapm, path, control);
if (ret != 0)
goto err;
break;
default:
break;
}
}
list_add(&path->list, &dapm->card->paths);
snd_soc_dapm_for_each_direction(dir)
list_add(&path->list_node[dir], &widgets[dir]->edges[dir]);
snd_soc_dapm_for_each_direction(dir) {
dapm_update_widget_flags(widgets[dir]);
dapm_mark_dirty(widgets[dir], "Route added");
}
if (dapm->card->instantiated && path->connect)
dapm_path_invalidate(path);
return 0;
err:
kfree(path);
return ret;
}
dapm_connect_mixer 用该函数连接一个sink widget为mixer类型的所有source端。
用需要用来连接的kcontrol的名字，和sink widget中的kcontrol模板数组中的名字相比较，path的名字设置为该kcontrol的名字，然后用dapm_set_path_status函数来初始化该输入端的连接状态。
/* connect mixer widget to its interconnecting audio paths */
static int dapm_connect_mixer(struct snd_soc_dapm_context *dapm,
struct snd_soc_dapm_path *path, const char *control_name)
{
int i;
/* search for mixer kcontrol */
for (i = 0; i < path->sink->num_kcontrols; i++) {
if (!strcmp(control_name, path->sink->kcontrol_news[i].name)) {
path->name = path->sink->kcontrol_news[i].name;
dapm_set_mixer_path_status(path, i);
return 0;
}
}
return -ENODEV;
}
以上是CPU DAI 和Codec内部dapm建立path的过程。
在snd_soc_instantiate_card中，调用snd_soc_dapm_link_dai_widgets来建立dai widget和非dai widget的path
snd_soc_dapm_link_dai_widgets函数会去遍历每一个dai widgets，然后遍历所有的非dai widgets，如果非dai widgets的stream name与dai widgets的name相同，则把两个widgets建立path。这也是为什么创建dai widgets时name一定要是stream name的原因之一了。
int snd_soc_dapm_link_dai_widgets(struct snd_soc_card *card)
{
struct snd_soc_dapm_widget *dai_w, *w;
struct snd_soc_dapm_widget *src, *sink;
struct snd_soc_dai *dai;
/* For each DAI widget... */
list_for_each_entry(dai_w, &card->widgets, list) {
switch (dai_w->id) {
case snd_soc_dapm_dai_in:
case snd_soc_dapm_dai_out:
break;
default:
continue;
}
/* let users know there is no DAI to link */
if (!dai_w->priv) {
dev_dbg(card->dev, "dai widget %s has no DAI\n",
dai_w->name);
continue;
}
dai = dai_w->priv;
/* ...find all widgets with the same stream and link them */
list_for_each_entry(w, &card->widgets, list) {
if (w->dapm != dai_w->dapm)
continue;
switch (w->id) {
case snd_soc_dapm_dai_in:
case snd_soc_dapm_dai_out:
continue;
default:
break;
}
if (!w->sname || !strstr(w->sname, dai_w->sname))
continue;
if (dai_w->id == snd_soc_dapm_dai_in) {
src = dai_w;
sink = w;
} else {
src = w;
sink = dai_w;
}
dev_dbg(dai->dev, "%s -> %s\n", src->name, sink->name);
snd_soc_dapm_add_path(w->dapm, src, sink, NULL, NULL);
}
}
return 0;
}
调用snd_soc_dapm_connect_dai_link_widgets() 建立CPU BE DAI widget 和 codec DAI widget之间的path.
void snd_soc_dapm_connect_dai_link_widgets(struct snd_soc_card *card)
{
struct snd_soc_pcm_runtime *rtd;
/* for each BE DAI link... */
list_for_each_entry(rtd, &card->rtd_list, list) {
/*
* dynamic FE links have no fixed DAI mapping.
* CODEC<->CODEC links have no direct connection.
*/
if (rtd->dai_link->dynamic || rtd->dai_link->params)
continue;
dapm_connect_dai_link_widgets(card, rtd);
}
}
static void dapm_connect_dai_link_widgets(struct snd_soc_card *card,
struct snd_soc_pcm_runtime *rtd)
{
struct snd_soc_dai *cpu_dai = rtd->cpu_dai;
struct snd_soc_dapm_widget *sink, *source;
int i;
for (i = 0; i < rtd->num_codecs; i++) {
struct snd_soc_dai *codec_dai = rtd->codec_dais[i];
/* connect BE DAI playback if widgets are valid */
if (codec_dai->playback_widget && cpu_dai->playback_widget) {
source = cpu_dai->playback_widget;
sink = codec_dai->playback_widget;
dev_dbg(rtd->dev, "connected DAI link %s:%s -> %s:%s\n",
cpu_dai->component->name, source->name,
codec_dai->component->name, sink->name);
snd_soc_dapm_add_path(&card->dapm, source, sink,
NULL, NULL);
}
/* connect BE DAI capture if widgets are valid */
if (codec_dai->capture_widget && cpu_dai->capture_widget) {
source = codec_dai->capture_widget;
sink = cpu_dai->capture_widget;
dev_dbg(rtd->dev, "connected DAI link %s:%s -> %s:%s\n",
codec_dai->component->name, source->name,
cpu_dai->component->name, sink->name);
snd_soc_dapm_add_path(&card->dapm, source, sink,
NULL, NULL);
}
}
}
建立widget 的dapm kcontrol
定义一个widget，我们需要指定两个很重要的内容：一个是用于控制widget的电源状态的reg/shift等寄存器信息，另一个是用于控制音频路径切换的dapm kcontrol信息，这些dapm kcontrol有它们自己的reg/shift寄存器信息用于切换widget的路径连接方式。前面我们只是创建了widget的实例，并把它们注册到声卡的widgts链表中，但是到目前为止，包含在widget中的dapm kcontrol并没有建立起来，dapm框架在声卡的初始化阶段，等所有的widget（包括machine、platform、codec）都创建好之后，通过snd_soc_dapm_new_widgets函数，创建widget内包含的dapm kcontrol，并初始化widget的初始电源状态和音频路径的初始连接状态。
/**
* snd_soc_dapm_new_widgets - add new dapm widgets
* @card: card to be checked for new dapm widgets
*
* Checks the codec for any new dapm widgets and creates them if found.
*
* Returns 0 for success.
*/
int snd_soc_dapm_new_widgets(struct snd_soc_card *card)
{
struct snd_soc_dapm_widget *w;
unsigned int val;
mutex_lock_nested(&card->dapm_mutex, SND_SOC_DAPM_CLASS_INIT);
list_for_each_entry(w, &card->widgets, list)
{
if (w->new)
continue;
if (w->num_kcontrols) {
w->kcontrols = kzalloc(w->num_kcontrols *
sizeof(struct snd_kcontrol *),
GFP_KERNEL);
if (!w->kcontrols) {
mutex_unlock(&card->dapm_mutex);
return -ENOMEM;
}
}
switch(w->id) {
case snd_soc_dapm_switch:
case snd_soc_dapm_mixer:
case snd_soc_dapm_mixer_named_ctl:
dapm_new_mixer(w);
break;
case snd_soc_dapm_mux:
case snd_soc_dapm_demux:
dapm_new_mux(w);
break;
case snd_soc_dapm_pga:
case snd_soc_dapm_out_drv:
dapm_new_pga(w);
break;
case snd_soc_dapm_dai_link:
dapm_new_dai_link(w);
break;
default:
break;
}
/* Read the initial power state from the device */
if (w->reg >= 0) {
soc_dapm_read(w->dapm, w->reg, &val);
val = val >> w->shift;
val &= w->mask;
if (val == w->on_val)
w->power = 1;
}
w->new = 1;
dapm_mark_dirty(w, "new widget");
dapm_debugfs_add_widget(w);
}
dapm_power_widgets(card, SND_SOC_DAPM_STREAM_NOP);
mutex_unlock(&card->dapm_mutex);
return 0;
}
该函数通过声卡的widgets链表，遍历所有已经注册了的widget，其中的new字段用于判断该widget是否已经执行过snd_soc_dapm_new_widgets函数，如果num_kcontrols字段有数值，表明该widget包含有若干个dapm kcontrol，那么就需要为这些kcontrol分配一个指针数组，并把数组的首地址赋值给widget的kcontrols字段，该数组存放着指向这些kcontrol的指针，当然现在这些都是空指针，因为实际的kcontrol现在还没有被创建.
接着，对几种能影响音频路径的widget，创建并初始化它们所包含的dapm kcontrol.
需要用到的创建函数分别是：
dapm_new_mixer() 对于mixer类型，用该函数创建dapm kcontrol；
dapm_new_mux() 对于mux类型，用该函数创建dapm kcontrol；
dapm_new_pga() 对于pga类型，用该函数创建dapm kcontrol；
根据widget寄存器的当前值，初始化widget的电源状态，并设置到power字段中.
接着，设置new字段，表明该widget已经初始化完成，我们还要吧该widget加入到声卡的dapm_dirty链表中，表明该widget的状态发生了变化，稍后在合适的时刻，dapm框架会扫描dapm_dirty链表，统一处理所有已经变化的widget。为什么要统一处理？因为dapm要控制各种widget的上下电顺序，同时也是为了减少寄存器的读写次数（多个widget可能使用同一个寄存器）
最后，通过dapm_power_widgets函数，统一处理所有位于dapm_dirty链表上的widget的状态改变.
damp_new_mixer:
/* create new dapm mixer control */
static int dapm_new_mixer(struct snd_soc_dapm_widget *w)
{
int i, ret;
struct snd_soc_dapm_path *path;
struct dapm_kcontrol_data *data;
/* add kcontrol */
for (i = 0; i < w->num_kcontrols; i++) {
/* match name */
snd_soc_dapm_widget_for_each_source_path(w, path) {
/* mixer/mux paths name must match control name */
if (path->name != (char *)w->kcontrol_news[i].name)
continue;
if (!w->kcontrols[i]) {
ret = dapm_create_or_share_kcontrol(w, i);
if (ret < 0)
return ret;
}
dapm_kcontrol_add_path(w->kcontrols[i], path);
data = snd_kcontrol_chip(w->kcontrols[i]);
if (data->widget)
snd_soc_dapm_add_path(data->widget->dapm,
data->widget,
path->source,
NULL, NULL);
}
}
return 0;
}
一个mixer类型的widget是由多个kcontrol组成的，每个kcontrol控制着mixer的一个输入端的开启和关闭，所以，该函数会根据kcontrol的数量做循环，逐个建立对应的kcontrol。
找到mixer widget的source path, 如果kcontrol的name和source path的name一样则创建kcontrol.
如果kcontrol之前没有被创建，则通过dapm_create_or_share_kcontrol()创建这个输入端的kcontrol.
/*
* Determine if a kcontrol is shared. If it is, look it up. If it isn't,
* create it. Either way, add the widget into the control's widget list
*/
static int dapm_create_or_share_kcontrol(struct snd_soc_dapm_widget *w,
int kci)
{
struct snd_soc_dapm_context *dapm = w->dapm;
struct snd_card *card = dapm->card->snd_card;
const char *prefix;
size_t prefix_len;
int shared;
struct snd_kcontrol *kcontrol;
bool wname_in_long_name, kcname_in_long_name;
char *long_name = NULL;
const char *name;
int ret = 0;
prefix = soc_dapm_prefix(dapm);
if (prefix)
prefix_len = strlen(prefix) + 1;
else
prefix_len = 0;
shared = dapm_is_shared_kcontrol(dapm, w, &w->kcontrol_news[kci],
&kcontrol);
if (!kcontrol) {
if (shared) {
wname_in_long_name = false;
kcname_in_long_name = true;
} else {
switch (w->id) {
case snd_soc_dapm_switch:
case snd_soc_dapm_mixer:
case snd_soc_dapm_pga:
case snd_soc_dapm_out_drv:
wname_in_long_name = true;
kcname_in_long_name = true;
break;
case snd_soc_dapm_mixer_named_ctl:
wname_in_long_name = false;
kcname_in_long_name = true;
break;
case snd_soc_dapm_demux:
case snd_soc_dapm_mux:
wname_in_long_name = true;
kcname_in_long_name = false;
break;
default:
return -EINVAL;
}
}
if (wname_in_long_name && kcname_in_long_name) {
/*
* The control will get a prefix from the control
* creation process but we're also using the same
* prefix for widgets so cut the prefix off the
* front of the widget name.
*/
long_name = kasprintf(GFP_KERNEL, "%s %s",
w->name + prefix_len,
w->kcontrol_news[kci].name);
if (long_name == NULL)
return -ENOMEM;
name = long_name;
} else if (wname_in_long_name) {
long_name = NULL;
name = w->name + prefix_len;
} else {
long_name = NULL;
name = w->kcontrol_news[kci].name;
}
kcontrol = snd_soc_cnew(&w->kcontrol_news[kci], NULL, name,
prefix);
if (!kcontrol) {
ret = -ENOMEM;
goto exit_free;
}
kcontrol->private_free = dapm_kcontrol_free;
ret = dapm_kcontrol_data_alloc(w, kcontrol, name);
if (ret) {
snd_ctl_free_one(kcontrol);
goto exit_free;
}
ret = snd_ctl_add(card, kcontrol);
if (ret < 0) {
dev_err(dapm->dev,
"ASoC: failed to add widget %s dapm kcontrol %s: %d\n",
w->name, name, ret);
goto exit_free;
}
}
ret = dapm_kcontrol_add_widget(kcontrol, w);
if (ret == 0)
w->kcontrols[kci] = kcontrol;
exit_free:
kfree(long_name);
return ret;
}
dapm_create_or_share_kcontrol()所做的事情如下：
（1） 为了节省内存，通过kcontrol名字的匹配查找，如果这个kcontrol已经在其他widget中已经创建好了，那我们不再创建，dapm_is_shared_kcontrol的参数kcontrol会返回已经创建好的kcontrol的指针。
（2） 如果kcontrol指针被赋值，说明在（1）中查找到了其他widget中同名的kcontrol，我们不用再次创建，只要共享该kcontrol即可。
（3） 在snd_soc_cnew()中调用标准的kcontrol创建函数snd_ctl_new1()。
（4） 在dapm_kcontrol_data_alloc中，如果widget支持autodisable特性，创建与该kcontrol所对应的影子widget，该影子widget的类型是：snd_soc_dapm_kcontrol。
（5） 调用snd_ctl_add()将创建的kcontrol添加到card->snd_card->controls链表
（6） 把所有共享该kcontrol的影子widget（snd_soc_dapm_kcontrol），加入到kcontrol的private_data字段所指向的dapm_kcontrol_data结构中。
（7） 把创建好的kcontrol指针赋值到widget的kcontrols数组中。
增加一个虚拟的影子widget，该影子widget在dapm_new_mixer()中和path->source widget建立path，因为使用了kcontrol本身的reg/shift等寄存器信息，所以实际上控制的是该kcontrol的开和关，这个影子widget只有在kcontrol的autodisable字段被设置的情况下才会被创建，该特性使得source的关闭时，与之连接的mixer的输入端也可以自动关闭。
在 snd_soc_dapm_new_widgets的最后，通过dapm_power_widgets()函数，统一处理所有位于dapm_dirty链表上的widget的状态改变.
/*
* Scan each dapm widget for complete audio path.
* A complete path is a route that has valid endpoints i.e.:-
*
* o DAC to output pin.
* o Input pin to ADC.
* o Input pin to Output pin (bypass, sidetone)
* o DAC to ADC (loopback).
*/
static int dapm_power_widgets(struct snd_soc_card *card, int event)
{
struct snd_soc_dapm_widget *w;
struct snd_soc_dapm_context *d;
LIST_HEAD(up_list);
LIST_HEAD(down_list);
ASYNC_DOMAIN_EXCLUSIVE(async_domain);
enum snd_soc_bias_level bias;
lockdep_assert_held(&card->dapm_mutex);
trace_snd_soc_dapm_start(card);
list_for_each_entry(d, &card->dapm_list, list) {
if (dapm_idle_bias_off(d))
d->target_bias_level = SND_SOC_BIAS_OFF;
else
d->target_bias_level = SND_SOC_BIAS_STANDBY;
}
dapm_reset(card);
/* Check which widgets we need to power and store them in
* lists indicating if they should be powered up or down. We
* only check widgets that have been flagged as dirty but note
* that new widgets may be added to the dirty list while we
* iterate.
*/
list_for_each_entry(w, &card->dapm_dirty, dirty) {
dapm_power_one_widget(w, &up_list, &down_list);
}
list_for_each_entry(w, &card->widgets, list) {
switch (w->id) {
case snd_soc_dapm_pre:
case snd_soc_dapm_post:
/* These widgets always need to be powered */
break;
default:
list_del_init(&w->dirty);
break;
}
if (w->new_power) {
d = w->dapm;
/* Supplies and micbiases only bring the
* context up to STANDBY as unless something
* else is active and passing audio they
* generally don't require full power. Signal
* generators are virtual pins and have no
* power impact themselves.
*/
switch (w->id) {
case snd_soc_dapm_siggen:
case snd_soc_dapm_vmid:
break;
case snd_soc_dapm_supply:
case snd_soc_dapm_regulator_supply:
case snd_soc_dapm_clock_supply:
case snd_soc_dapm_micbias:
if (d->target_bias_level < SND_SOC_BIAS_STANDBY)
d->target_bias_level = SND_SOC_BIAS_STANDBY;
break;
default:
d->target_bias_level = SND_SOC_BIAS_ON;
break;
}
}
}
/* Force all contexts in the card to the same bias state if
* they're not ground referenced.
*/
bias = SND_SOC_BIAS_OFF;
list_for_each_entry(d, &card->dapm_list, list)
if (d->target_bias_level > bias)
bias = d->target_bias_level;
list_for_each_entry(d, &card->dapm_list, list)
if (!dapm_idle_bias_off(d))
d->target_bias_level = bias;
trace_snd_soc_dapm_walk_done(card);
/* Run card bias changes at first */
dapm_pre_sequence_async(&card->dapm, 0);
/* Run other bias changes in parallel */
list_for_each_entry(d, &card->dapm_list, list) {
if (d != &card->dapm)
async_schedule_domain(dapm_pre_sequence_async, d,
&async_domain);
}
async_synchronize_full_domain(&async_domain);
list_for_each_entry(w, &down_list, power_list) {
dapm_seq_check_event(card, w, SND_SOC_DAPM_WILL_PMD);
}
list_for_each_entry(w, &up_list, power_list) {
dapm_seq_check_event(card, w, SND_SOC_DAPM_WILL_PMU);
}
/* Power down widgets first; try to avoid amplifying pops. */
dapm_seq_run(card, &down_list, event, false);
dapm_widget_update(card);
/* Now power up. */
dapm_seq_run(card, &up_list, event, true);
/* Run all the bias changes in parallel */
list_for_each_entry(d, &card->dapm_list, list) {
if (d != &card->dapm)
async_schedule_domain(dapm_post_sequence_async, d,
&async_domain);
}
async_synchronize_full_domain(&async_domain);
/* Run card bias changes at last */
dapm_post_sequence_async(&card->dapm, 0);
/* do we need to notify any clients that DAPM event is complete */
list_for_each_entry(d, &card->dapm_list, list) {
if (d->stream_event)
d->stream_event(d, event);
}
pop_dbg(card->dev, card->pop_time,
"DAPM sequencing finished, waiting %dms\n", card->pop_time);
pop_wait(card->pop_time);
trace_snd_soc_dapm_done(card);
return 0;
}
dapm_power_widgets
当一个widget的状态改变后，该widget会被加入dapm_dirty链表，然后通过dapm_power_widgets函数来改变整个音频路径上的电源状态
1)该函数通过遍历dapm_dirty链表，对每个链表中的widget调用dapm_power_one_widget，dapm_power_one_widget函数除了处理自身的状态改变外，还把自身的变化传递到和它相连的邻居widget中，结果就是，所有需要上电的widget会被放在up_list链表中，而所有需要下电的widget会被放在down_list链表中，这个函数我们稍后再讨论。
2)遍历down_list链表，向其中的widget发出SND_SOC_DAPM_WILL_PMD事件，感兴趣该事件的widget的event回调会被调用。
3)遍历up_list链表，向其中的widget发出SND_SOC_DAPM_WILL_PMU事件，感兴趣该事件的widget的event回调会被调用。
4)通过dapm_seq_run函数，处理down_list中的widget，使它们按定义好的顺序依次下电。
5)通过dapm_widget_update函数，切换触发该次状态变化的widget的kcontrol中的寄存器值，对应的结果就是：改变音频路径。
6)通过dapm_seq_run函数，处理up_list中的widget，使它们按定义好的顺序依次上电。
7)对每个dapm context发出状态改变回调。
8)适当的延时，防止pop-pop声。
dapm_power_one_widget:
dapm_power_widgets的第一步，就是遍历dapm_dirty链表，对每个链表中的widget调用dapm_power_one_widget，把需要上电和需要下电的widget分别加入到up_list和down_list链表中，同时，他还会把受到影响的邻居widget再次加入到dapm_dirty链表的末尾，通过这个动作，声卡中所以受到影响的widget都会被“感染”，依次被加到dapm_dirty链表，然后依次被执行dapm_power_one_widget函数。
static void dapm_power_one_widget(struct snd_soc_dapm_widget *w,
struct list_head *up_list,
struct list_head *down_list)
{
int power;
switch (w->id) {
case snd_soc_dapm_pre:
dapm_seq_insert(w, down_list, false);
break;
case snd_soc_dapm_post:
dapm_seq_insert(w, up_list, true);
break;
default:
power = dapm_widget_power_check(w);
dapm_widget_set_power(w, power, up_list, down_list);
break;
}
}
1)通过dapm_widget_power_check，调用widget的power_check回调函数，获得该widget新的电源状态。
2)调用dapm_widget_set_power，“感染”与之相连的邻居widget。
遍历source widget，通过dapm_widget_set_peer_power函数，把处于连接状态的source widget加入dapm_dirty链表中。
遍历sink widget，通过dapm_widget_set_peer_power函数，把处于连接状态的sink widget加入dapm_dirty链表中。
3)根据第一步得到的新的电源状态，把widget加入到up_list或down_list链表中。
可见，通过该函数，一个widget的状态改变，邻居widget会受到“感染”而被加入到dapm_dirty链表的末尾，所以扫描到链表的末尾时，邻居widget也会执行同样的操作，从而“感染”邻居的邻居，直到没有新的widget被加入dapm_dirty链表为止，这时，所有受到影响的widget都被加入到up_list或down_li链表中，等待后续的上下电操作。
power_check回调函数
在创建widget的时候，widget的power_check回调函数会根据widget的类型，设置不同的回调函数。当widget的状态改变后，dapm会遍历dapm_dirty链表，并通过power_check回调函数，决定该widget是否需要上电。
dapm要给一个widget上电的其中一个前提条件是：这个widget位于一条完整的音频路径上，而一条完整的音频路径的两头，必须是输入/输出引脚，或者是一个外部音频设备，又或者是一个处于激活状态的音频流widget，它们可以位于路径的末端，但不是构成完成音频路径的必要条件，我们只用它来判断扫描一条路径的结束条件。
大多数的widget的power_check回调被设置为：dapm_generic_check_power
/* Generic check to see if a widget should be powered. */
static int dapm_generic_check_power(struct snd_soc_dapm_widget *w)
{
int in, out;
DAPM_UPDATE_STAT(w, power_checks);
in = is_connected_input_ep(w, NULL, NULL);
out = is_connected_output_ep(w, NULL, NULL);
return out != 0 && in != 0;
}
dapm_generic_check_power()中分别用is_connected_output_ep和is_connected_input_ep得到该widget连到多少个input endpoint和output endpoint, 从而判断是否有同时连接到一个输入端和一个输出端，如果是，返回1来表示该widget需要上电。
dapm提供了两个内部函数，用来统计一个widget连接到输出引脚、输入引脚、激活的音频流widget的有效路径个数：
is_connected_output_ep 返回连接至输出引脚或激活状态的输出音频流的路径数量
is_connected_input_ep 返回连接至输入引脚或激活状态的输入音频流的路径数量
/*
* Recursively check for a completed path to an active or physically connected
* output widget. Returns number of complete paths.
*
* Optionally, can be supplied with a function acting as a stopping condition.
* This function takes the dapm widget currently being examined and the walk
* direction as an arguments, it should return true if widgets from that point
* in the graph onwards should not be added to the widget list.
*/
static int is_connected_output_ep(struct snd_soc_dapm_widget *widget,
struct list_head *list,
bool (*custom_stop_condition)(struct snd_soc_dapm_widget *i,
enum snd_soc_dapm_direction))
{
return is_connected_ep(widget, list, SND_SOC_DAPM_DIR_OUT,
is_connected_output_ep, custom_stop_condition);
}
/*
* Recursively check for a completed path to an active or physically connected
* input widget. Returns number of complete paths.
*
* Optionally, can be supplied with a function acting as a stopping condition.
* This function takes the dapm widget currently being examined and the walk
* direction as an arguments, it should return true if the walk should be
* stopped and false otherwise.
*/
static int is_connected_input_ep(struct snd_soc_dapm_widget *widget,
struct list_head *list,
bool (*custom_stop_condition)(struct snd_soc_dapm_widget *i,
enum snd_soc_dapm_direction))
{
return is_connected_ep(widget, list, SND_SOC_DAPM_DIR_IN,
is_connected_input_ep, custom_stop_condition);
}
/*
* Common implementation for is_connected_output_ep() and
* is_connected_input_ep(). The function is inlined since the combined size of
* the two specialized functions is only marginally larger then the size of the
* generic function and at the same time the fast path of the specialized
* functions is significantly smaller than the generic function.
*/
static __always_inline int is_connected_ep(struct snd_soc_dapm_widget *widget,
struct list_head *list, enum snd_soc_dapm_direction dir,
int (*fn)(struct snd_soc_dapm_widget *, struct list_head *,
bool (*custom_stop_condition)(struct snd_soc_dapm_widget *,
enum snd_soc_dapm_direction)),
bool (*custom_stop_condition)(struct snd_soc_dapm_widget *,
enum snd_soc_dapm_direction))
{
enum snd_soc_dapm_direction rdir = SND_SOC_DAPM_DIR_REVERSE(dir);
struct snd_soc_dapm_path *path;
int con = 0;
if (widget->endpoints[dir] >= 0)
return widget->endpoints[dir];
DAPM_UPDATE_STAT(widget, path_checks);
/* do we need to add this widget to the list ? */
if (list)
list_add_tail(&widget->work_list, list);
if (custom_stop_condition && custom_stop_condition(widget, dir)) {
list = NULL;
custom_stop_condition = NULL;
}
if ((widget->is_ep & SND_SOC_DAPM_DIR_TO_EP(dir)) && widget->connected) {
widget->endpoints[dir] = snd_soc_dapm_suspend_check(widget);
return widget->endpoints[dir];
}
snd_soc_dapm_widget_for_each_path(widget, rdir, path) {
DAPM_UPDATE_STAT(widget, neighbour_checks);
if (path->weak || path->is_supply)
continue;
if (path->walking)
return 1;
trace_snd_soc_dapm_path(widget, dir, path);
if (path->connect) {
path->walking = 1;
con += fn(path->node[dir], list, custom_stop_condition);
path->walking = 0;
}
}
widget->endpoints[dir] = con;
return con;
}
dapm_seq_run
当所有需要上电或下电的widget都被加入到dapm_dirty链表后，接着会通过dapm_seq_run处理down_list链表上的widget，把该链表上的widget按顺序下电，然后通过dapm_widget_update更新widget中的kcontrol（这个kcontrol通常就是触发本次状态改变的触发源），接着又通过apm_seq_run处理up_list链表上的widget，把该链表上的widget按顺序上电。最终的上电或下电操作需要通过codec的寄存器来实现，因为定义widget时，如果这是一个带电源控制的widget，我们必须提供reg/shift等字段的设置值，如果该widget无需寄存器控制电源状态，则reg字段必须赋值为：
SND_SOC_NOPM (该宏定义的实际值是-1)
具体实现上，dapm框架使用了一点技巧：如果位于同一个上下电顺序的几个widget使用了同一个寄存器地址（一个寄存器可能使用不同的位来控制不同的widget的电源状态），dapm_seq_run通过dapm_seq_run_coalesced函数合并这几个widget的变更，然后只需要把合并后的值一次写入寄存器即可。
/* Apply a DAPM power sequence.
*
* We walk over a pre-sorted list of widgets to apply power to. In
* order to minimise the number of writes to the device required
* multiple widgets will be updated in a single write where possible.
* Currently anything that requires more than a single write is not
* handled.
*/
static void dapm_seq_run(struct snd_soc_card *card,
struct list_head *list, int event, bool power_up)
{
struct snd_soc_dapm_widget *w, *n;
struct snd_soc_dapm_context *d;
LIST_HEAD(pending);
int cur_sort = -1;
int cur_subseq = -1;
int cur_reg = SND_SOC_NOPM;
struct snd_soc_dapm_context *cur_dapm = NULL;
int ret, i;
int *sort;
if (power_up)
sort = dapm_up_seq;
else
sort = dapm_down_seq;
list_for_each_entry_safe(w, n, list, power_list) {
ret = 0;
/* Do we need to apply any queued changes? */
if (sort[w->id] != cur_sort || w->reg != cur_reg ||
w->dapm != cur_dapm || w->subseq != cur_subseq) {
if (!list_empty(&pending))
dapm_seq_run_coalesced(card, &pending);
if (cur_dapm && cur_dapm->seq_notifier) {
for (i = 0; i < ARRAY_SIZE(dapm_up_seq); i++)
if (sort[i] == cur_sort)
cur_dapm->seq_notifier(cur_dapm,
i,
cur_subseq);
}
if (cur_dapm && w->dapm != cur_dapm)
soc_dapm_async_complete(cur_dapm);
INIT_LIST_HEAD(&pending);
cur_sort = -1;
cur_subseq = INT_MIN;
cur_reg = SND_SOC_NOPM;
cur_dapm = NULL;
}
switch (w->id) {
case snd_soc_dapm_pre:
if (!w->event)
list_for_each_entry_safe_continue(w, n, list,
power_list);
if (event == SND_SOC_DAPM_STREAM_START)
ret = w->event(w,
NULL, SND_SOC_DAPM_PRE_PMU);
else if (event == SND_SOC_DAPM_STREAM_STOP)
ret = w->event(w,
NULL, SND_SOC_DAPM_PRE_PMD);
break;
case snd_soc_dapm_post:
if (!w->event)
list_for_each_entry_safe_continue(w, n, list,
power_list);
if (event == SND_SOC_DAPM_STREAM_START)
ret = w->event(w,
NULL, SND_SOC_DAPM_POST_PMU);
else if (event == SND_SOC_DAPM_STREAM_STOP)
ret = w->event(w,
NULL, SND_SOC_DAPM_POST_PMD);
break;
default:
/* Queue it up for application */
cur_sort = sort[w->id];
cur_subseq = w->subseq;
cur_reg = w->reg;
cur_dapm = w->dapm;
list_move(&w->power_list, &pending);
break;
}
if (ret < 0)
dev_err(w->dapm->dev,
"ASoC: Failed to apply widget power: %d\n", ret);
}
if (!list_empty(&pending))
dapm_seq_run_coalesced(card, &pending);
if (cur_dapm && cur_dapm->seq_notifier) {
for (i = 0; i < ARRAY_SIZE(dapm_up_seq); i++)
if (sort[i] == cur_sort)
cur_dapm->seq_notifier(cur_dapm,
i, cur_subseq);
}
list_for_each_entry(d, &card->dapm_list, list) {
soc_dapm_async_complete(d);
}
}
dapm kcontrol的put回调
上面我们已经讨论了如何判断一个widget是否需要上电，以及widget的上电过程，一个widget的状态改变如何传递到整个音频路径上的所有widget。这些过程总是需要一个起始点：是谁触动了dapm，使得它需要执行上述的扫描和上电过程？事实上，以下几种情况可以触发dapm发起一次扫描操作：
1)声卡初始化阶段，snd_soc_dapm_new_widgets函数创建widget包含的kcontrol后，会触发一次扫描操作。
2)用户空间的应用程序修改了widget中包含的dapm kcontrol的配置值时，会触发一次扫描操作。
3)pcm的打开或关闭，会通过音频流widget触发一次扫描操作。
4)驱动程序在改变了某个widget并把它加入到dapm_dirty链表后，主动调用snd_soc_dapm_sync函数触发扫描操作。
这里我们主要讨论一下第二种，用户空间对kcontrol的修改，最终都会调用到kcontrol的put回调函数。对于常用的dapm kcontrol，系统已经为我们定义好了它们的put回调函数：
snd_soc_dapm_put_volsw mixer类型的dapm kcontrol使用的put回调
snd_soc_dapm_put_enum_double mux类型的dapm kcontrol使用的put回调
snd_soc_dapm_put_enum_virt 虚拟mux类型的dapm kcontrol使用的put回调
snd_soc_dapm_put_value_enum_double 控制值不连续的mux类型的dapm kcontrol使用的put回调
snd_soc_dapm_put_pin_switch 引脚类dapm kcontrol使用的put回调
我们以mixer类型的dapm kcontrol的put回调讲解一下触发的过程：
/**
* snd_soc_dapm_put_volsw - dapm mixer set callback
* @kcontrol: mixer control
* @ucontrol: control element information
*
* Callback to set the value of a dapm mixer control.
*
* Returns 0 for success.
*/
int snd_soc_dapm_put_volsw(struct snd_kcontrol *kcontrol,
struct snd_ctl_elem_value *ucontrol)
{
struct snd_soc_dapm_context *dapm = snd_soc_dapm_kcontrol_dapm(kcontrol);
struct snd_soc_card *card = dapm->card;
struct soc_mixer_control *mc =
(struct soc_mixer_control *)kcontrol->private_value;
int reg = mc->reg;
unsigned int shift = mc->shift;
int max = mc->max;
unsigned int mask = (1 << fls(max)) - 1;
unsigned int invert = mc->invert;
unsigned int val;
int connect, change, reg_change = 0;
struct snd_soc_dapm_update update;
int ret = 0;
if (snd_soc_volsw_is_stereo(mc))
dev_warn(dapm->dev,
"ASoC: Control '%s' is stereo, which is not supported\n",
kcontrol->id.name);
val = (ucontrol->value.integer.value[0] & mask);
connect = !!val;
if (invert)
val = max - val;
mutex_lock_nested(&card->dapm_mutex, SND_SOC_DAPM_CLASS_RUNTIME);
change = dapm_kcontrol_set_value(kcontrol, val);
if (reg != SND_SOC_NOPM) {
mask = mask << shift;
val = val << shift;
reg_change = soc_dapm_test_bits(dapm, reg, mask, val);
}
if (change || reg_change) {
if (reg_change) {
update.kcontrol = kcontrol;
update.reg = reg;
update.mask = mask;
update.val = val;
card->update = &update;
}
change |= reg_change;
ret = soc_dapm_mixer_update_power(card, kcontrol, connect);
card->update = NULL;
}
mutex_unlock(&card->dapm_mutex);
if (ret > 0)
soc_dpcm_runtime_update(card);
return change;
}
其中的dapm_kcontrol_set_value函数用于把设置值缓存到kcontrol对应的影子widget，影子widget是为了实现autodisable特性而创建的一个虚拟widget，影子widget的输出连接到kcontrol的source widget，影子widget的寄存器被设置为和kcontrol一样的寄存器地址，这样当source widget被关闭时，会触发影子widget被关闭，其作用就是kcontrol也被自动关闭从而在物理上断开与source widget的连接，但是此时逻辑连接依然有效，dapm依然认为它们是连接在一起的。 触发dapm进行电源状态扫描关键的函数是soc_dapm_mixer_update_power：
/* test and update the power status of a mixer or switch widget */
static int soc_dapm_mixer_update_power(struct snd_soc_card *card,
struct snd_kcontrol *kcontrol, int connect)
{
struct snd_soc_dapm_path *path;
int found = 0;
lockdep_assert_held(&card->dapm_mutex);
/* find dapm widget path assoc with kcontrol */
dapm_kcontrol_for_each_path(path, kcontrol) {
found = 1;
soc_dapm_connect_path(path, connect, "mixer update");
}
if (found)
dapm_power_widgets(card, SND_SOC_DAPM_STREAM_NOP);
return found;
}
最终，还是通过dapm_power_widgets函数，触发整个音频路径的扫描过程，这个函数执行后，因为kcontrol的状态改变，被断开连接的音频路径上的所有widget被按顺序下电，而重新连上的音频路径上的所有widget被顺序地上电，所以，尽管我们只改变了mixer kcontrol中的一个输入端的连接状态，所有相关的widget的电源状态都会被重新设定，这一切，都是自动完成的，对用户空间的应用程序完全透明，实现了dapm的原本设计目标。