mixer_hw_open

"mixer_hw_open"通常是指在一个音频处理系统中，特别是Linux内核的ALSA (Advanced Linux Sound Architecture) API的一部分。它是一个函数，用于初始化或打开硬件音效混合器（Mixer）。Mixer是一种控制台，允许用户调整声音的各种属性，如音量、平衡等。当应用程序需要访问声卡的硬件混音功能时，会调用这个函数来建立到特定硬件混音器的连接，并获取操作权限。

该函数的原型一般类似这样：

int mixer_hw_open(struct hw_device_info *hwdev, struct mixer_card **card);

其中，`struct hw_device_info *hwdev`是一个设备描述结构体，包含了关于设备的信息；`struct mixer_card **card`是一个指向混合器卡片的指针，返回成功连接后的混音器设备信息。

如果想深入了解，

相关问题

ls_stk3332.c

以下是一个示例的ls_stk3332.c驱动程序，用于实现RK3588与STK3332之间的音频输入和输出功能：

#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/slab.h>
#include <linux/regmap.h>
#include <sound/core.h>
#include <sound/pcm.h>
#include <sound/control.h>

#define STK3332_REG_GAIN 0x00
#define STK3332_REG_VOLUME 0x01
#define STK3332_REG_MUTE 0x02

struct stk3332_data {
    struct regmap *regmap;
    unsigned int gain;
    unsigned int volume;
    bool mute;
};

static int stk3332_set_gain(struct snd_kcontrol *kcontrol,
                            struct snd_ctl_elem_value *ucontrol)
{
    struct stk3332_data *data = snd_kcontrol_chip(kcontrol);
    unsigned int gain = ucontrol->value.integer.value[0];

    if (gain > 255)
        gain = 255;

    data->gain = gain;
    regmap_write(data->regmap, STK3332_REG_GAIN, gain);

    return 0;
}

static int stk3332_get_gain(struct snd_kcontrol *kcontrol,
                            struct snd_ctl_elem_value *ucontrol)
{
    struct stk3332_data *data = snd_kcontrol_chip(kcontrol);

    ucontrol->value.integer.value[0] = data->gain;

    return 0;
}

static int stk3332_set_volume(struct snd_kcontrol *kcontrol,
                              struct snd_ctl_elem_value *ucontrol)
{
    struct stk3332_data *data = snd_kcontrol_chip(kcontrol);
    unsigned int volume = ucontrol->value.integer.value[0];

    if (volume > 255)
        volume = 255;

    data->volume = volume;
    regmap_write(data->regmap, STK3332_REG_VOLUME, volume);

    return 0;
}

static int stk3332_get_volume(struct snd_kcontrol *kcontrol,
                              struct snd_ctl_elem_value *ucontrol)
{
    struct stk3332_data *data = snd_kcontrol_chip(kcontrol);

    ucontrol->value.integer.value[0] = data->volume;

    return 0;
}

static int stk3332_set_mute(struct snd_kcontrol *kcontrol,
                            struct snd_ctl_elem_value *ucontrol)
{
    struct stk3332_data *data = snd_kcontrol_chip(kcontrol);
    bool mute = ucontrol->value.integer.value[0];

    data->mute = mute;
    regmap_write(data->regmap, STK3332_REG_MUTE, mute ? 1 : 0);

    return 0;
}

static int stk3332_get_mute(struct snd_kcontrol *kcontrol,
                            struct snd_ctl_elem_value *ucontrol)
{
    struct stk3332_data *data = snd_kcontrol_chip(kcontrol);

    ucontrol->value.integer.value[0] = data->mute ? 1 : 0;

    return 0;
}

static const struct snd_kcontrol_new stk3332_controls[] = {
    {
        .iface = SNDRV_CTL_ELEM_IFACE_MIXER,
        .name = "Gain",
        .access = SNDRV_CTL_ELEM_ACCESS_READWRITE,
        .info = snd_ctl_boolean_mono_info,
        .get = stk3332_get_gain,
        .put = stk3332_set_gain,
    },
    {
        .iface = SNDRV_CTL_ELEM_IFACE_MIXER,
        .name = "Volume",
        .access = SNDRV_CTL_ELEM_ACCESS_READWRITE,
        .info = snd_ctl_boolean_mono_info,
        .get = stk3332_get_volume,
        .put = stk3332_set_volume,
    },
    {
        .iface = SNDRV_CTL_ELEM_IFACE_MIXER,
        .name = "Mute",
        .access = SNDRV_CTL_ELEM_ACCESS_READWRITE,
        .info = snd_ctl_boolean_mono_info,
        .get = stk3332_get_mute,
        .put = stk3332_set_mute,
    },
    { } /* end */
};

static int stk3332_pcm_open(struct snd_pcm_substream *substream)
{
    return 0;
}

static int stk3332_pcm_close(struct snd_pcm_substream *substream)
{
    return 0;
}

static int stk3332_pcm_hw_params(struct snd_pcm_substream *substream,
                                 struct snd_pcm_hw_params *params)
{
    return 0;
}

static int stk3332_pcm_hw_free(struct snd_pcm_substream *substream)
{
    return 0;
}

static struct snd_pcm_ops stk3332_pcm_ops = {
    .open = stk3332_pcm_open,
    .close = stk3332_pcm_close,
    .ioctl = snd_pcm_lib_ioctl,
    .hw_params = stk3332_pcm_hw_params,
    .hw_free = stk3332_pcm_hw_free,
};

static int stk3332_pcm_new(struct snd_card *card,
                           struct snd_soc_pcm_runtime *rtd)
{
    struct snd_pcm *pcm;
    int ret;

    ret = snd_pcm_new(card, "STK3332 PCM", 0, 1, 0, &pcm);
    if (ret < 0)
        return ret;

    pcm->private_data = rtd;
    pcm->info_flags = 0;
    strcpy(pcm->name, "STK3332 PCM");

    snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK, &stk3332_pcm_ops);

    return 0;
}

static int stk3332_probe(struct platform_device *pdev)
{
    struct device *dev = &pdev->dev;
    struct stk3332_data *data;
    struct regmap *regmap;

    regmap = dev_get_regmap(dev->parent, NULL);
    if (!regmap) {
        dev_err(dev, "Failed to get regmap\n");
        return -ENODEV;
    }

    data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
    if (!data)
        return -ENOMEM;

    data->regmap = regmap;
    data->gain = 128;
    data->volume = 128;
    data->mute = false;

    platform_set_drvdata(pdev, data);

    // 注册音频控制器
    snd_soc_register_codec(&pdev->dev, &codec_stk3332, &stk3332_dai, 1);

    // 注册PCM设备
    return snd_soc_new_pcm_runtime(&pdev->dev, &stk3332_pcm_dai, &stk3332_pcm_platform, 0);
}

static int stk3332_remove(struct platform_device *pdev)
{
    snd_soc_unregister_codec(&pdev->dev);
    return 0;
}

static const struct of_device_id stk3332_of_match[] = {
    { .compatible = "st,stk3332", },
    { },
};
MODULE_DEVICE_TABLE(of, stk3332_of_match);

static struct platform_driver stk3332_driver = {
    .probe = stk3332_probe,
    .remove = stk3332_remove,
    .driver = {
        .name = "stk3332",
        .of_match_table = stk3332_of_match,
    },
};
module_platform_driver(stk3332_driver);

MODULE_DESCRIPTION("STK3332 audio driver");
MODULE_AUTHOR("Your Name");
MODULE_LICENSE("GPL");

以上驱动程序仅供参考，具体的驱动程序要根据实际的硬件连接和应用需求进行调整和修改。同时，需要根据实际情况进行dts配置和驱动程序的加载，以实现音频输入和输出的功能。