comip-lm49350 Soc音频模块和codec

最新推荐文章于 2024-04-12 17:34:48 发布

原创最新推荐文章于 2024-04-12 17:34:48 发布 · 953 阅读

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#codec #struct #audio #allocation #代码分析 #module

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本文详细介绍了COMIP_LM49350音频模块的初始化过程，包括平台设备的创建、注册及卸载流程，并深入探讨了音频子系统的结构和组成部分。

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comip-lm49350.c 是CPU的音频模块+ codec lm49350 统一成一个整体的设备结构。他会先注册成一个platform device。

代码分析如下：

1. init/exit

static int __init comip_soc_init(void)
    {
        int ret;
        printk(KERN_INFO "COMIP_LM49350 SoC Audio driver\n");
        comip_snd_lm49350_device = platform_device_alloc("soc-audio", -1);  //分配一块platform device 内存空间
        if (!comip_snd_lm49350_device) {
            printk(KERN_ERR "Platform device allocation failed\n");
            return -ENOMEM;
        }
        platform_set_drvdata(comip_snd_lm49350_device, &comip_snd_devdata);  //把comip_snd_devdata 设置进platform device中
        comip_snd_devdata.dev = &comip_snd_lm49350_device->dev;  //dev -> snd_soc_device.dev
        ret = platform_device_add(comip_snd_lm49350_device);   //添加platform 设备
        if (ret) {
            printk(KERN_ERR "COMIP_LM49350 Soc Audio: Unable to add \n");
            platform_device_put(comip_snd_lm49350_device);     //如失败，则去除platform设备
        }
        return ret;
    }
    module_init(comip_soc_init);
    static void __exit comip_soc_exit(void)
    {
        platform_device_unregister(comip_snd_lm49350_device);  //注销platform device
    }
    module_exit(comip_soc_exit);

    static struct platform_device *comip_snd_lm49350_device;   //定义platform设备,comip_snd_lm49350_device 最上层的数据结构

2. struct snd_soc_device comip_snd_devdata;

/* Audio subsystem */
    static struct snd_soc_device comip_snd_devdata = {
        .card = &snd_soc_comip,                    //卡card
        .codec_dev = &soc_codec_dev_lm49350,       //codec 设备 lm49350 操作。
    };

snd_soc_device 原型定义如下，代表一个SOC音频控制器和CODEC，即系统中的整个音频模块。

/* SoC Device - the audio subsystem */
    struct snd_soc_device {
        struct device *dev;
        struct snd_soc_card *card;
        struct snd_soc_codec_device *codec_dev;
        void *codec_data;
    };

3. struct snd_soc_card snd_soc_comip ：代表一个 card

/* Audio machine driver */
    static struct snd_soc_card snd_soc_comip = {
        .name = "COMIP_LM49350",
        .platform = &comip_soc_platform,
        .dai_link = comip_lm49350_dai,
        .num_links = ARRAY_SIZE(comip_lm49350_dai),
    };

snd_soc_card 原型定义如下：

/* SoC card */
    struct snd_soc_card {
        char *name;
        struct device *dev;
        struct list_head list;
        int instantiated;
        int (*probe)(struct platform_device *pdev);
        int (*remove)(struct platform_device *pdev);
        /* the pre and post PM functions are used to do any PM work before and
         * after the codec and DAI's do any PM work. */
        int (*suspend_pre)(struct platform_device *pdev, pm_message_t state);
        int (*suspend_post)(struct platform_device *pdev, pm_message_t state);
        int (*resume_pre)(struct platform_device *pdev);
        int (*resume_post)(struct platform_device *pdev);
        /* callbacks */
        int (*set_bias_level)(struct snd_soc_card *,
                 enum snd_soc_bias_level level);
        long pmdown_time;
        /* CPU <--> Codec DAI links */
        struct snd_soc_dai_link *dai_link;
        int num_links;
        struct snd_soc_device *socdev;
        struct snd_soc_codec *codec;
        struct snd_soc_platform *platform;
        struct delayed_work delayed_work;
        struct work_struct deferred_resume_work;
    };