Linux input子系统实例分析（二）

紧接着上一节的实例我们来分析调用的input子系统的接口：

1. input_dev,用来标识输入设备

   1:  struct input_dev {

   2:      const char *name;      //设备名

   3:      const char *phys;     // 设备在系统中路径

   4:      const char *uniq;

   5:      struct input_id id;    //与input_handler匹配用的id

   6:   

   7:      unsigned long propbit[BITS_TO_LONGS(INPUT_PROP_CNT)];

   8:   

   9:      unsigned long evbit[BITS_TO_LONGS(EV_CNT)]; //设备所支持事件类型，主要有EV_SYNC,EV_KEY,EV_REL,EV_ABS等       

  10:      unsigned long keybit[BITS_TO_LONGS(KEY_CNT)];// 按键所对应的位图

  11:      unsigned long relbit[BITS_TO_LONGS(REL_CNT)];//  相对坐标对应位图

  12:      unsigned long absbit[BITS_TO_LONGS(ABS_CNT)];// 绝对坐标对应位图

  13:      unsigned long mscbit[BITS_TO_LONGS(MSC_CNT)];//支持其它事件

  14:      unsigned long ledbit[BITS_TO_LONGS(LED_CNT)];//支持led事件

  15:      unsigned long sndbit[BITS_TO_LONGS(SND_CNT)];//支持声音事件

  16:      unsigned long ffbit[BITS_TO_LONGS(FF_CNT)];//支持受力事件

  17:      unsigned long swbit[BITS_TO_LONGS(SW_CNT)];//支持开关机事件

  18:   

  19:      unsigned int hint_events_per_packet;

  20:   

  21:      unsigned int keycodemax;

  22:      unsigned int keycodesize;

  23:      void *keycode;

  24:   

  25:      int (*setkeycode)(struct input_dev *dev,

  26:                const struct input_keymap_entry *ke,

  27:                unsigned int *old_keycode);

  28:      int (*getkeycode)(struct input_dev *dev,

  29:                struct input_keymap_entry *ke);

  30:   

  31:      struct ff_device *ff;

  32:   

  33:      unsigned int repeat_key;//最近一次的按键值

  34:      struct timer_list timer;

  35:   

  36:      int rep[REP_CNT];

  37:   

  38:      struct input_mt_slot *mt;

  39:      int mtsize;

  40:      int slot;

  41:      int trkid;

  42:   

  43:      struct input_absinfo *absinfo;

  44:   

  45:      unsigned long key[BITS_TO_LONGS(KEY_CNT)];//反应设备当前的按键状态

  46:      unsigned long led[BITS_TO_LONGS(LED_CNT)];//反应设备当前的led状态

  47:      unsigned long snd[BITS_TO_LONGS(SND_CNT)];//反应设备当前的声音输入状态

  48:      unsigned long sw[BITS_TO_LONGS(SW_CNT)];//反应设备当前的开关状态

  49:   

  50:      int (*open)(struct input_dev *dev);//第一次打开设备时调用，初始化设备用

  51:      void (*close)(struct input_dev *dev);//最后一个应用程序释放设备时用，关闭设备

  52:      int (*flush)(struct input_dev *dev, struct file *file);/*用于处理传递给设备的事件，如LED事件和声音事件*/

  53:      //  事件处理函数，主要是接收用户下发的命令，如点亮led；

  54:      int (*event)(struct input_dev *dev, unsigned int type, unsigned int code, int value);

  55:   

  56:      struct input_handle __rcu *grab;    //当前占有该设备的input_handle

  57:   

  58:      spinlock_t event_lock;

  59:      struct mutex mutex;

  60:   

  61:      unsigned int users;        //打开该设备的用户数量(input handlers)

  62:      bool going_away;

  63:   

  64:      bool sync;

  65:   

  66:      struct device dev;

  67:   

  68:      struct list_head    h_list; // 设备所支持的input handle; 

  69:      struct list_head    node;    //用于将此input_dev链接到input_dev_list

  70:  };

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2.把输入设备注册进核心层  int input_register_device(struct input_dev *dev)

   1:  int input_register_device(struct input_dev *dev)

   2:  {

   3:      static atomic_t input_no = ATOMIC_INIT(0);

   4:      struct input_handler *handler;

   5:      const char *path;

   6:      int error;

   7:   

   8:      /* Every input device generates EV_SYN/SYN_REPORT events. */

   9:      __set_bit(EV_SYN, dev->evbit);//  /*表示设备支持所有的事件*/ 

  10:   

  11:      /* KEY_RESERVED is not supposed to be transmitted to userspace. */

  12:      __clear_bit(KEY_RESERVED, dev->keybit);

  13:   

  14:      /* Make sure that bitmasks not mentioned in dev->evbit are clean. */

  15:      input_cleanse_bitmasks(dev);

  16:   

  17:      if (!dev->hint_events_per_packet)

  18:          dev->hint_events_per_packet =

  19:                  input_estimate_events_per_packet(dev);

  20:   

  21:      /*

  22:       * If delay and period are pre-set by the driver, then autorepeating

  23:       * is handled by the driver itself and we don't do it in input.c.

  24:       */

  25:      init_timer(&dev->timer);//初始化定时器

  26:      /*如果dev->rep[REP_DELAY]和dev->rep[REP_PERIOD]没有设值，

  27:      则将其赋默认值，这主要是为自动处理重复按键定义*/

  28:      if (!dev->rep[REP_DELAY] && !dev->rep[REP_PERIOD]) {

  29:          dev->timer.data = (long) dev;

  30:          dev->timer.function = input_repeat_key;//定时器处理函数

  31:          dev->rep[REP_DELAY] = 250;

  32:          dev->rep[REP_PERIOD] = 33;

  33:      }

  34:   

  35:      if (!dev->getkeycode)//获取键值

  36:          dev->getkeycode = input_default_getkeycode;

  37:   

  38:      if (!dev->setkeycode)//设置键值

  39:          dev->setkeycode = input_default_setkeycode;

  40:      //设置input_dev中的device的名字

  41:      dev_set_name(&dev->dev, "input%ld",

  42:               (unsigned long) atomic_inc_return(&input_no) - 1);

  43:   

  44:      error = device_add(&dev->dev);//将input_dev包含的device结构注册到Linux设备模型中，并可以在sysfs文件系统中表现出来。

  45:      if (error)

  46:          return error;

  47:   

  48:      path = kobject_get_path(&dev->dev.kobj, GFP_KERNEL);

  49:      pr_info("%s as %s\n",

  50:          dev->name ? dev->name : "Unspecified device",

  51:          path ? path : "N/A");

  52:      kfree(path);

  53:   

  54:      error = mutex_lock_interruptible(&input_mutex);

  55:      if (error) {

  56:          device_del(&dev->dev);

  57:          return error;

  58:      }

  59:   

  60:      list_add_tail(&dev->node, &input_dev_list);//添加到input device 链表

  61:   

  62:      list_for_each_entry(handler, &input_handler_list, node)//

  63:          input_attach_handler(dev, handler);

  64:   

  65:      input_wakeup_procfs_readers();

  66:   

  67:      mutex_unlock(&input_mutex);

  68:   

  69:      return 0;

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3.调用input_report_key函数报告此事件

   1:  static inline void input_report_key(struct input_dev *dev, unsigned int code, int value)

   2:  {

   3:      input_event(dev, EV_KEY, code, !!value);

   4:  }

input_report_key函数参数，1.input_dev设备，2。按键值 3.按键的状态（1按下，0松开）

在input.h中定义了按键类code的值，BTN_0,BTN_1,KEY_A KEY_B等等这样的键值

此函数只是调用了input_event函数，这个函数是总的事件报告函数，

   1:  void input_event(struct input_dev *dev, unsigned int type, unsigned int code, int value)

   2:  {

   3:      unsigned long flags;

   4:   

   5:      if (is_event_supported(type, dev->evbit, EV_MAX)) {    //(1)

   6:   

   7:          spin_lock_irqsave(&dev->event_lock, flags);    //(2)

   8:          add_input_randomness(type, code, value);    //(3)

   9:          input_handle_event(dev, type, code, value);    //(4)

  10:          spin_unlock_irqrestore(&dev->event_lock, flags);//(5)    

  11:      }

  12:  }

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参数1.input_dev 2.事件类型(如EV_KEY键盘事件) 3.此类型具体事件code(如KEY_A，键A) 4.此事件的值(如1，按键按下)

(1)设备是否支持该事件类型。下面分析

(2)自旋锁上锁

(3)因为按键是随机事件，所以对随机熵有贡献，对于驱动无关。具体不懂

(4)进一步处理报告的事件

(5)自旋锁解锁

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