ALSA駆動中snd_soc_write()原理分析及びdemo

       remap_write() i2c_transter()  i2c     ,  。
1.Audio Codec    
kernel/include/sound/soc.h
/* SoC Audio Codec device */
<1>.struct snd_soc_codec {
  const struct snd_soc_codec_driver *driver;
  struct snd_soc_component component;
}

<2>./* codec driver */
struct snd_soc_codec_driver {
   int (*write)(struct snd_soc_codec *, unsigned int, unsigned int);
};

struct snd_soc_component { 
  struct snd_soc_dai_driver *dai_drv;
  const struct snd_soc_component_driver *driver;
  int (*write)(struct snd_soc_component *, unsigned int, unsigned int);
  struct snd_soc_codec *codec; 
  struct regmap *regmap;
};

******************************************************************************

1.snd_soc_write()      
kernel/sound/soc/soc-io.c
int snd_soc_write(struct snd_soc_codec *codec, unsigned int reg,  unsigned int val){
  return snd_soc_component_write(&codec->component, reg, val);
}

int snd_soc_component_write(struct snd_soc_component *component,unsigned int reg, unsigned int val){
 if(component->regmap)
   return regmap_write(component->regmap, reg, val);
 else if (component->write)  
   return component->write(component, reg, val);
 else
   return -EIO;
}
     ，        remap_write()  i2c_transter()  i2c  .
  ：
  snd_soc_write()   ，      snd_soc_codec_driver     write     ?
//1.    
struct snd_soc_codec *codec;
snd_soc_write(codec, 0x08, 0x01);

//2.      
static int xxx_write(struct snd_soc_codec *codec, unsigned int reg, unsigned int val){
  //     snd_soc_write()    reg = 8,val = 1;
  printk(KERN_ERR “%s, %d, reg = %d, val = %d
", __func__,__LINE__,reg, val);
}

static const struct snd_soc_codec_driver soc_codec_dev_xxx = {
     .write =   xxx_write,
}; 

// soc_codec_dev_xxx  snd_soc_register_codec()    codec ,       .
ret = snd_soc_register_codec(&i2c->dev, &soc_codec_dev_xxx, xxx, xxx);

//2.  snd_soc_register_codec()  
kernel/sound/soc/soc-core.c
int snd_soc_register_codec(struct device *dev， const struct snd_soc_codec_driver *codec_drv,…){
  //      snd_soc_codec_driver *codec_drv  。
  //    codec_drv->write  ，          ，    snd_soc_codec_drv_write()       。
  if(codec_drv->write)
    codec->component.write = snd_soc_codec_drv_write;    
}

//3.snd_soc_codec_drv_write()       
static int snd_soc_codec_drv_write(struct snd_sic_component *component, unsigned int reg, unsigned int val){
  //  snd_soc_codec  snd_sic_component    ，  snd_soc_codec      ，snd_soc_component_to_codec  。  container_of()    ，    .
  struct snd_soc_codec *codec = snd_soc_component_to_codec(component);
  //snd_soc_codec  snd_soc_codec_driver    write    ，        soc_codec_dev_xxx        。
  return codec->driver->write(codec, reg, val);
}

*********************************************************************************

4.  snd_soc_write()        demo  .

#include 
/*struct define*/
static struct snd_soc_codec_driver {
    int (*write)(struct snd_soc_codec *codec, unsigned int, unsigned int);
};

static struct snd_soc_component { 
    int (*write)(struct snd_soc_component *com, unsigned int, unsigned int);
};

static struct snd_soc_codec {
    struct snd_soc_codec_driver *driver;
    struct snd_soc_component component;
};

#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
#define container_of(ptr, type, member) ({				\
	    const typeof( ((type *)0)->member ) *__mptr = (ptr);	\
	    (type *)( (char *)__mptr - offsetof(type,member) );})

struct snd_soc_codec *codec = NULL;

//callback  
int callback_write(struct snd_soc_codec *codec, unsigned int reg, unsigned int val){
    printf("xxx--->%s(), %d, reg: %d, val: %d

",__FUNCTION__,__LINE__,reg,val);
    return 0;
}

static int snd_soc_codec_drv_write(struct snd_soc_component *component, unsigned int reg, unsigned int val){
    struct snd_soc_codec *c_codec = container_of(component, struct snd_soc_codec, component);
    printf("xxx--->%s(), %d, reg: %d, val: %d
",__FUNCTION__,__LINE__,reg,val);    
    return codec->driver->write(c_codec, reg, val);
}


void codec_register(struct snd_soc_codec_driver *codec_drv){
    printf("xxx--->%s(), %d
",__FUNCTION__,__LINE__);
    if(codec_drv->write)
	codec->component.write = snd_soc_codec_drv_write;
}

// snd_soc_write() callback_write()    ;    snd_soc_write    callback_write()  .
int snd_soc_write(struct snd_soc_codec *codec,unsigned int reg, unsigned int val){
    printf("xxx--->%s(), %d, reg: %d, val: %d
",__FUNCTION__,__LINE__,reg,val);
    if(codec->component.write)
	return codec->component.write(&codec->component, reg, val);    
    return 0;
}

int main(){
    codec = (struct snd_soc_codec*)malloc(sizeof(struct snd_soc_codec));
    //      
    struct snd_soc_codec_driver test_codec = {
	.write = callback_write,
    };
    
    codec->driver = &test_codec;
    //  
    codec_register(codec->driver);

    //  1:      .
    //codec->driver->write(codec, 11, 35); 
    
    //  2        
    while(1){
	snd_soc_write(codec, 11, 35);
    //   
    //codec->driver->write(codec, 11, 35);
	sleep(1);
    }
    
    if(codec)
	free(codec);
}