asoc 音频驱动学习笔记2

接下来我们看看codec的probe函数吧

static int wm8960_probe(struct snd_soc_codec *codec){<span style="color:#ff0000;">struct wm8960_priv *wm8960 = snd_soc_codec_get_drvdata(codec);struct wm8960_data *pdata = dev_get_platdata(codec->dev);</span>int ret;u16 reg;wm8960->set_bias_level = wm8960_set_bias_level_out3;codec->control_data = wm8960->control_data;

先看第一个snd_soc_codec_get_drvdata(codec);

static inline void *snd_soc_codec_get_drvdata(struct snd_soc_codec *codec){return dev_get_drvdata(codec->dev);}    void *dev_get_drvdata(const struct device *dev){if (dev && dev->p)return dev->p->driver_data;return NULL;}

由上面可知，最终得到的结构为codec->dev->p->driver_data，这个结构在哪呢，i2c_set_clientdata(i2c, wm8960)  ->  ret = snd_soc_register_codec(&i2c->dev,

&soc_codec_dev_wm8960, &wm8960_dai, 1); -> codec->dev = dev;，由此可知，这个driver_data为班级配置中定义的平台设备的driver_data

然后看第二个 dev_get_platdata(codec->dev);

static inline void *dev_get_platdata(const struct device *dev){return dev->platform_data;}

在板级配置中

#ifdef CONFIG_SND_SOC_WM8960_MINI210{<span style="color:#ff0000;">I2C_BOARD_INFO("wm8960", 0x1a),</span><span style="color:#ff0000;">.platform_data = &wm8960_pdata,</span>},#endif#ifdef CONFIG_SND_SOC_WM8960_MINI210#include <sound/wm8960.h>static struct wm8960_data wm8960_pdata = {.capless= 0,.dres= WM8960_DRES_400R,};#endif

////////////////////////////////////////////////////////////////////////////////////////////接着进行probe函数分析

wm8960->set_bias_level = wm8960_set_bias_level_out3;<span style="color:#ff0000;">codec->control_data = wm8960->control_data;这个地方的值为i2c</span>

<span style="color:#ff0000;">if (!pdata) {进行pdata的判断</span>dev_warn(codec->dev, "No platform data supplied\n");} else {if (pdata->dres > WM8960_DRES_MAX) {dev_err(codec->dev, "Invalid DRES: %d\n", pdata->dres);pdata->dres = 0;}if (pdata->capless)wm8960->set_bias_level = wm8960_set_bias_level_capless;}  <span style="color:#ff0000;">ret = snd_soc_codec_set_cache_io(codec, 7, 9, wm8960->control_type);这个函数值得研究</span>if (ret < 0) {dev_err(codec->dev, "Failed to set cache I/O: %d\n", ret);return ret;}

<span style="color:#ff0000;">查看snd_soc_codec_set_cache_io函数</span>

/**建立标准io功能 * snd_soc_codec_set_cache_io: Set up standard I/O functions. * * @codec: CODEC to configure. * @addr_bits: Number of bits of register address data.

 * @data_bits: Number of bits of data per register. * @control: Control bus used.使用的控制总线 <span style="color:#ff0000;">*寄存器格式被频繁的分享在i2c和spi设备间，为了提高代码的重用率，ASOC核心提供了标准的codec read 和write操作</span> * Register formats are frequently shared between many I2C and SPI * devices.  In order to promote code reuse the ASoC core provides * some standard implementations of CODEC read and write operations * which can be set up using this function. * * The caller is responsible for allocating and initialising the * actual cache. * * Note that at present this code cannot be used by CODECs with * volatile registers. */int snd_soc_codec_set_cache_io(struct snd_soc_codec *codec,       int addr_bits, int data_bits,       enum snd_soc_control_type control){int i;<span style="color:#ff0000;">寻找匹配的寄存器操作格式，8960为7位地址，9位数据</span>for (i = 0; i < ARRAY_SIZE(io_types); i++)if (io_types[i].addr_bits == addr_bits &&    io_types[i].data_bits == data_bits)break;<span style="color:#ff0000;">if (i == ARRAY_SIZE(io_types)) {如果循环完了还没找到合适的格式，那么打印信息printk(KERN_ERR       "No I/O functions for %d bit address %d bit data\n",       addr_bits, data_bits);</span>return -EINVAL;}     <span style="color:#ff0000;">函数赋值codec->write = io_types[i].write;这个结构赋值后，最终会调用回codec->hw_write函数codec->read = io_types[i].read;read和write的处理方法不太一样，不深究了吧</span>codec->bulk_write_raw = snd_soc_hw_bulk_write_raw;switch (control) {case SND_SOC_I2C:#if defined(CONFIG_I2C) || (defined(CONFIG_I2C_MODULE) && defined(MODULE))codec->hw_write = (hw_write_t)i2c_master_send;#endifif (io_types[i].i2c_read)codec->hw_read = io_types[i].i2c_read;

<span style="color:#ff0000;">codec->control_data = container_of(codec->dev,   struct i2c_client,   dev);这个和函数的意思是根据codec->dev找到它属于的结构struct i2c_client的地址，codec->dev,为dev型的break;</span>case SND_SOC_SPI:#ifdef CONFIG_SPI_MASTERcodec->hw_write = do_spi_write;#endifcodec->control_data = container_of(codec->dev,   struct spi_device,   dev);break;}return 0;}

接着进行wm8960_probe函数分析

ret = wm8960_reset(codec);if (ret < 0) {dev_err(codec->dev, "Failed to issue reset\n");return ret;}

////////////////////////////////展开wm8960_reset()

对8960进行复位

#define wm8960_reset(c)snd_soc_write(c, WM8960_RESET, 0)unsigned int snd_soc_write(struct snd_soc_codec *codec,   unsigned int reg, unsigned int val){dev_dbg(codec->dev, "write %x = %x\n", reg, val);trace_snd_soc_reg_write(codec, reg, val);return codec->write(codec, reg, val);}

//////////////////////回到probe函数

if (ret < 0) {dev_err(codec->dev, "Failed to issue reset\n");return ret;}wm8960->set_bias_level(codec, SND_SOC_BIAS_STANDBY);/* Latch the update bits */reg = snd_soc_read(codec, WM8960_LINVOL);snd_soc_write(codec, WM8960_LINVOL, reg | 0x100);

reg = snd_soc_read(codec, WM8960_RINVOL);snd_soc_write(codec, WM8960_RINVOL, reg | 0x100);reg = snd_soc_read(codec, WM8960_LADC);snd_soc_write(codec, WM8960_LADC, reg | 0x100);reg = snd_soc_read(codec, WM8960_RADC);snd_soc_write(codec, WM8960_RADC, reg | 0x100);reg = snd_soc_read(codec, WM8960_LDAC);snd_soc_write(codec, WM8960_LDAC, reg | 0x100);reg = snd_soc_read(codec, WM8960_RDAC);snd_soc_write(codec, WM8960_RDAC, reg | 0x100);reg = snd_soc_read(codec, WM8960_LOUT1);snd_soc_write(codec, WM8960_LOUT1, reg | 0x100);reg = snd_soc_read(codec, WM8960_ROUT1);snd_soc_write(codec, WM8960_ROUT1, reg | 0x100);reg = snd_soc_read(codec, WM8960_LOUT2);snd_soc_write(codec, WM8960_LOUT2, reg | 0x100);reg = snd_soc_read(codec, WM8960_ROUT2);snd_soc_write(codec, WM8960_ROUT2, reg | 0x100);

以上是对9860进行初始化操作

nd_soc_add_controls(codec, wm8960_snd_controls,     ARRAY_SIZE(wm8960_snd_controls));wm8960_add_widgets(codec);

展开snd_soc_add_controls，添加一个控制队列到一个codec

/** * snd_soc_add_controls - add an array of controls to a codec. * Convienience function to add a list of controls. Many codecs were * duplicating this code. * * @codec: codec to add controls to * @controls: array of controls to add * @num_controls: number of elements in the array * * Return 0 for success, else error. */int snd_soc_add_controls(struct snd_soc_codec *codec,const struct snd_kcontrol_new *controls, int num_controls){struct snd_card *card = codec->card->snd_card;int err, i;for (i = 0; i < num_controls; i++) {<span style="color:#ff0000;">const struct snd_kcontrol_new *control = &controls[i];新的control</span><span style="color:#ff0000;">err = snd_ctl_add(card, snd_soc_cnew(control, codec,     control->name,codec->name_prefix));</span>

<span style="color:#000000;">if (err < 0) {dev_err(codec->dev, "%s: Failed to add %s: %d\n",codec->name, control->name, err);return err;}}return 0;}</span>

<span style="color:#000000;">/** * snd_ctl_add - add the control instance to the card * @card: the card instance * @kcontrol: the control instance to add * * Adds the control instance created via snd_ctl_new() or * snd_ctl_new1() to the given card. Assigns also an unique * numid used for fast search. * * Returns zero if successful, or a negative error code on failure. * * It frees automatically the control which cannot be added. */int snd_ctl_add(struct snd_card *card, struct snd_kcontrol *kcontrol)</span>

这个函数的作用是添加一个control 实例到声卡Adds the control instance created via snd_ctl_new() or snd_ctl_new1() to the given card.

snd_soc_cnew(control, codec,control->name,codec->name_prefix)

    kcontrol = snd_ctl_new1(&template, data);

    return snd_ctl_new(&kctl, access);

Codec的驱动大体看到这，挺乱的，都是看代码时的顺序乱记的，写博客应该总结总结，以后再总结吧