声卡注册流程（linux-5.4）

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_FSstruct dentry *debugfs_card_root;
#endif
#ifdef CONFIG_PM_SLEEPstruct work_struct deferred_resume_work;
#endifu32 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 tosnd_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 withspace */struct module *module;          /* top-level module */void *private_data;             /* private data for soundcard */void (*private_free) (struct snd_card *card); /* callback for freeing ofprivate 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 shutdownstate */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_PMunsigned 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;
#endifANDROID_KABI_RESERVE(1);ANDROID_KABI_RESERVE(2);
};

可以看出，三个结构体的大致内容：

asoc_simple_priv:

属于该结构体的snd_soc_card
dai相关
时钟相关
耳机、麦克风拔插相关
功放相关

snd_soc_card:

snd_soc_card的基本信息
属于该结构体的snd_card
各种mutex(PCM、DAPM等)
电源管理相关的操作函数
回调函数(DAPM、DAI LINK)
DAPM、DAI LINK相关

snd_card:

声卡的基本信息
属于该声卡的control设备
proc文件系统的相关配置
sys文件系统的相关配置

流程介绍

probe()

为asoc_simple_priv分配空间并初始化 --- devm_kzalloc_priv() asoc_simple_init_priv()
判断pdev->dev的status是否为okay --- of_device_is_available()
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()

实例化snd_soc_card --- snd_soc_instantiate_card()

snd_soc_instantiate_card()

初始化snd_soc_dai_link结构体（关于dai匹配）--- soc_init_dai_link()
初始化dapm，并把dapm->list加到card->dapm_list里面 --- snd_soc_dapm_init()
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
绑定aux设备（耳机口），也是从component list中找到再给card --- soc_bind_aux_dev()
都完成都开始创建声卡 --- snd_card_new()
初始化dubugfs --- soc_init_card_debugfs()
初始化dapm部分 --- snd_soc_dapm_new_controls()
初始化声卡（仅一次）--- card->probe
初始化所有dai用到的component --- soc_probe_link_components()
初始化所有aux设备 --- soc_probe_aux_devices()
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
初始化所有的dai link --- soc_probe_link_dais()
创建、添加PCM设备 --- soc_link_init()
连接dapm --- snd_soc_dapm_link_dai_widgets() snd_soc_dapm_connect_dai_link_widgets()
注册control设备 --- snd_soc_add_card_controls()
注册dapm的route --- snd_soc_dapm_add_routes()
注册设备树的dapm的route --- snd_soc_dapm_add_routes()
尝试设置dmi_name --- snd_soc_set_dmi_name()
设置snd_card->name --- snprintf(card->snd_card->**name, ...)
执行后部分初始化 --- card->late_probe()
注册dapm_widget --- snd_soc_dapm_new_widgets()
注册声卡 --- snd_card_register(card->snd_card)
检查所有dapm尾指针 --- dapm_mark_endpoints_dirty() snd_soc_dapm_sync()

snd_card_register()

注册声卡设备 --- device_add(&card->card_dev)
注册所属声卡的所有设备 --- snd_device_register_all()
通过 if 判断声卡是否已经注册 --- snd_cards[card->num]
设置card->id --- snd_card_set_id_no_lock()
加入到snd_cards[ ]中 --- snd_card[card->num] = card
注册card的proc文件--- snd_info_card_register()

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声卡注册流程（linux-5.4）

结构体介绍

流程介绍

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