结构体介绍

先介绍声卡相关结构体

struct asoc_simple_priv {
        struct snd_soc_card snd_card;
        struct simple_dai_props {
                struct asoc_simple_dai *cpu_dai;
                struct asoc_simple_dai *codec_dai;
                struct snd_soc_dai_link_component cpus;   /* single cpu */
                struct snd_soc_dai_link_component codecs; /* single codec */
                struct snd_soc_dai_link_component platforms;
                struct asoc_simple_data adata;
                struct snd_soc_codec_conf *codec_conf;
                bool mclk_fp;
                unsigned int mclk_fs;
                unsigned int cpu_pll_fs;
                unsigned int codec_pll_fs;
        } *dai_props;
        struct asoc_simple_jack hp_jack;
        struct asoc_simple_jack mic_jack;
        struct snd_soc_dai_link *dai_link;
        struct asoc_simple_dai *dais;
        struct snd_soc_codec_conf *codec_conf;
        struct gpio_desc *pa_gpio;
};

struct snd_soc_card {
        const char *name;
        const char *long_name;
        const char *driver_name;
        char dmi_longname[80];
        char topology_shortname[32];

        struct device *dev;
        struct snd_card *snd_card;
        struct module *owner;

        struct mutex mutex;
        struct mutex dapm_mutex;

        /* Mutex for PCM operations */
        struct mutex pcm_mutex;
        enum snd_soc_pcm_subclass pcm_subclass;

        spinlock_t dpcm_lock;

        bool instantiated;
        bool topology_shortname_created;

        int (*probe)(struct snd_soc_card *card);
        int (*late_probe)(struct snd_soc_card *card);
        int (*remove)(struct snd_soc_card *card);

        /* 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 snd_soc_card *card);
        int (*suspend_post)(struct snd_soc_card *card);
        int (*resume_pre)(struct snd_soc_card *card);
        int (*resume_post)(struct snd_soc_card *card);

        /* callbacks */
        int (*set_bias_level)(struct snd_soc_card *,
                              struct snd_soc_dapm_context *dapm,
                              enum snd_soc_bias_level level);
        int (*set_bias_level_post)(struct snd_soc_card *,
                                   struct snd_soc_dapm_context *dapm,
                                   enum snd_soc_bias_level level);

        int (*add_dai_link)(struct snd_soc_card *,
                            struct snd_soc_dai_link *link);
        void (*remove_dai_link)(struct snd_soc_card *,
                            struct snd_soc_dai_link *link);

        long pmdown_time;

        /* CPU <--> Codec DAI links  */
        struct snd_soc_dai_link *dai_link;  /* predefined links only */
        int num_links;  /* predefined links only */
        struct list_head dai_link_list; /* all links */

        struct list_head rtd_list;
        int num_rtd;

        /* optional codec specific configuration */
        struct snd_soc_codec_conf *codec_conf;
        int num_configs;

        /*
         * optional auxiliary devices such as amplifiers or codecs with DAI
         * link unused
         */
        struct snd_soc_aux_dev *aux_dev;
        int num_aux_devs;
        struct list_head aux_comp_list;

        const struct snd_kcontrol_new *controls;
        int num_controls;

        /*
         * Card-specific routes and widgets.
         * Note: of_dapm_xxx for Device Tree; Otherwise for driver build-in.
         */
        const struct snd_soc_dapm_widget *dapm_widgets;
        int num_dapm_widgets;
        const struct snd_soc_dapm_route *dapm_routes;
        int num_dapm_routes;
        const struct snd_soc_dapm_widget *of_dapm_widgets;
        int num_of_dapm_widgets;
        const struct snd_soc_dapm_route *of_dapm_routes;
        int num_of_dapm_routes;
        bool fully_routed;
        bool disable_route_checks;

        /* lists of probed devices belonging to this card */
        struct list_head component_dev_list;
        struct list_head list;

        struct list_head widgets;
        struct list_head paths;
        struct list_head dapm_list;
        struct list_head dapm_dirty;

        /* attached dynamic objects */
        struct list_head dobj_list;

        /* Generic DAPM context for the card */
        struct snd_soc_dapm_context dapm;
        struct snd_soc_dapm_stats dapm_stats;
        struct snd_soc_dapm_update *update;
        
#ifdef CONFIG_DEBUG_FS
        struct dentry *debugfs_card_root;
#endif
#ifdef CONFIG_PM_SLEEP
        struct work_struct deferred_resume_work;
#endif
        u32 pop_time;

        void *drvdata;

        ANDROID_KABI_RESERVE(1);
        ANDROID_KABI_RESERVE(2);
        ANDROID_KABI_RESERVE(3);
        ANDROID_KABI_RESERVE(4);
};

struct snd_card {
        int number;                     /* number of soundcard (index to
                                                                snd_cards) */

        char id[16];                    /* id string of this card */
        char driver[16];                /* driver name */
        char shortname[32];             /* short name of this soundcard */
        char longname[80];              /* name of this soundcard */
        char irq_descr[32];             /* Interrupt description */
        char mixername[80];             /* mixer name */
        char components[128];           /* card components delimited with
                                                                space */
        struct module *module;          /* top-level module */

        void *private_data;             /* private data for soundcard */
        void (*private_free) (struct snd_card *card); /* callback for freeing of
                                                                private data */
        struct list_head devices;       /* devices */

        struct device ctl_dev;          /* control device */
        unsigned int last_numid;        /* last used numeric ID */
        struct rw_semaphore controls_rwsem;     /* controls list lock */
        rwlock_t ctl_files_rwlock;      /* ctl_files list lock */
        int controls_count;             /* count of all controls */
        int user_ctl_count;             /* count of all user controls */
        struct list_head controls;      /* all controls for this card */
        struct list_head ctl_files;     /* active control files */

        struct snd_info_entry *proc_root;       /* root for soundcard specific files */
        struct proc_dir_entry *proc_root_link;  /* number link to real id */

        struct list_head files_list;    /* all files associated to this card */
        struct snd_shutdown_f_ops *s_f_ops; /* file operations in the shutdown
                                                                state */
        spinlock_t files_lock;          /* lock the files for this card */
        int shutdown;                   /* this card is going down */
        struct completion *release_completion;
        struct device *dev;             /* device assigned to this card */
        struct device card_dev;         /* cardX object for sysfs */
        const struct attribute_group *dev_groups[4]; /* assigned sysfs attr */
        bool registered;                /* card_dev is registered? */
        wait_queue_head_t remove_sleep;

#ifdef CONFIG_PM
        unsigned int power_state;       /* power state */
        wait_queue_head_t power_sleep;
#endif

#if IS_ENABLED(CONFIG_SND_MIXER_OSS)
        struct snd_mixer_oss *mixer_oss;
        int mixer_oss_change_count;
#endif

        ANDROID_KABI_RESERVE(1);
        ANDROID_KABI_RESERVE(2);
};

可以看出，三个结构体的大致内容：

asoc_simple_priv:

1. 属于该结构体的snd_soc_card

2. dai相关

3. 时钟相关

4. 耳机、麦克风拔插相关

5. 功放相关

snd_soc_card:

1. snd_soc_card的基本信息

2. 属于该结构体的snd_card

3. 各种mutex(PCM、DAPM等)

4. 电源管理相关的操作函数

5. 回调函数(DAPM、DAI LINK)

6. DAPM、DAI LINK相关

snd_card:

1. 声卡的基本信息

2. 属于该声卡的control设备

3. proc文件系统的相关配置

4. sys文件系统的相关配置

流程介绍

probe()

1. 为asoc_simple_priv分配空间并初始化 --- devm_kzalloc_priv() asoc_simple_init_priv()

2. 判断pdev->dev的status是否为okay --- of_device_is_available()

3. 最后跳到进行声卡注册 --- devm_snd_soc_register_card()
   3.1 snd_soc_register_card() --- 初始化card里的内核链表以及mutex，
        3.1.1 然后return snd_soc_bind_card()

snd_soc_bind_card()

1. 实例化snd_soc_card --- snd_soc_instantiate_card()

snd_soc_instantiate_card()

1. 初始化snd_soc_dai_link结构体（关于dai匹配）--- soc_init_dai_link()

2. 初始化dapm，并把dapm->list加到card->dapm_list里面 --- snd_soc_dapm_init()

3. 绑定dai link--- soc_bind_dai_link()
   3.1 soc_new_pcm_runtime() --- 初始化rtd（该结构体与绑定codec和platform有关）
   3.2 通过snd_soc_find_dai() 和 snd_soc_rtdcom_add()来拿到已经注册的codec和platform并添加到rtd
   3.3 通过soc_add_pcm_runtime()将rtd添加到card

4. 绑定aux设备（耳机口），也是从component list中找到再给card --- soc_bind_aux_dev()

5. 都完成都开始创建声卡 --- snd_card_new()

6. 初始化dubugfs --- soc_init_card_debugfs()

7. 初始化dapm部分 --- snd_soc_dapm_new_controls()

8. 初始化声卡（仅一次）--- card->probe

9. 初始化所有dai用到的component --- soc_probe_link_components()

10. 初始化所有aux设备 --- soc_probe_aux_devices()

11. 初始化dai links的时候可能会添加新的dais和dai links，所以还需要再进行一次1和3

12. 初始化所有的dai link --- soc_probe_link_dais()

13. 创建、添加PCM设备 --- soc_link_init()

14. 连接dapm --- snd_soc_dapm_link_dai_widgets() snd_soc_dapm_connect_dai_link_widgets()

15. 注册control设备 --- snd_soc_add_card_controls()

16. 注册dapm的route --- snd_soc_dapm_add_routes()

17. 注册设备树的dapm的route --- snd_soc_dapm_add_routes()

18. 尝试设置dmi_name --- snd_soc_set_dmi_name()

19. 设置snd_card->name --- snprintf(card->snd_card->**name, ...)

20. 执行后部分初始化 --- card->late_probe()

21. 注册dapm_widget --- snd_soc_dapm_new_widgets()

22. 注册声卡 --- snd_card_register(card->snd_card)

23. 检查所有dapm尾指针 --- dapm_mark_endpoints_dirty() snd_soc_dapm_sync()

snd_card_register()

1. 注册声卡设备 --- device_add(&card->card_dev)

2. 注册所属声卡的所有设备 --- snd_device_register_all()

3. 通过 if 判断声卡是否已经注册 --- snd_cards[card->num]

4. 设置card->id --- snd_card_set_id_no_lock()

5. 加入到snd_cards[ ]中 --- snd_card[card->num] = card

6. 注册card的proc文件--- snd_info_card_register()