為rt5625 codec 的 sysfs 增加一個 mic gain attr

mic gain 是 RT5625_MIC_CTRL,
使用的 write function 是：

snd_soc_write(codec,RT5625_MIC_CTRL,value);

read function 是：

int data = snd_soc_read(codec,RT5625_MIC_CTRL);

所以 sysfs 的 show 和 store:

	static ssize_t rt5625_mic_ctrl_show(struct device *dev,
	struct device_attribute *attr, char *buf)
	{
	struct i2c_client *client = to_i2c_client(dev);
	struct rt5625_priv *rt5625 = i2c_get_clientdata(client);
	struct snd_soc_codec *codec = rt5625->codec;
	int data = snd_soc_read(codec, RT5625_MIC_CTRL);
	return sprintf(buf, "%x",data);
	}
	static ssize_t rt5625_mic_ctrl_store(struct device *dev,
	struct device_attribute *attr, const char *buf, size_t count)
	{
	struct i2c_client *client = to_i2c_client(dev);
	struct rt5625_priv *rt5625 = i2c_get_clientdata(client);
	struct snd_soc_codec *codec = rt5625->codec;
	long regvalue;
	int status;
	status = strict_strtol(buf,16,&regvalue);
	if (status != 0) {
	printk("rt5625 invalid parameter format %s\n",buf);
	return -EINVAL;
	}
	snd_soc_write(codec, RT5625_MIC_CTRL, (int)regvalue&0xFFFF);
	return count;
	}
	static DEVICE_ATTR(mic_ctrl, S_IRUGO | S_IWUSR | S_IWGRP,
	rt5625_mic_ctrl_show, rt5625_mic_ctrl_store);

view raw gistfile1.c hosted with ❤ by GitHub

最後，在 rt5625_probe( ) 裡，加上：

        ret = device_create_file(codec->dev, &dev_attr_mic_ctrl);

        if (ret < 0 ) {
                dev_err(codec->dev,
                        "Failed to create mic_ctrl sysfs files: %d\n", ret);
                return ret;
        }

就可以了，
然後在機器啟動後，在 /sys/bus/i2c/drivers/rt5625-codec/0-001e 下，就會出現：

mic_ctrl

cat mic_ctrl 就會顯示 reg22 的值。
echo 800 > mic_ctrl 就會把 800 寫入 reg22