Linux/Android——输入子系统input_event传递 (二)【转】

Linux/Android——输入子系统input_event传递 (二)【转】
本文转载自：http://blog.csdn.net/jscese/article/details/42099381

在前文 Linux/Android——usb触摸屏驱动 - usbtouchscreen (一) 中记录了如何在kernel中添加input device 类型为touchscreen的驱动，

这在整个输入体系中是最下层的设备驱动部分，往上一层就是linux内核的管理驱动input系统，kernel中的源码位置：/kernel/drivers/input/input.c

                                  撰写不易,转载需注明出处：http://blog.csdn.net/jscese/article/details/42099381

到目前已经完全调通，可以正常使用了，现在记录一下这段时间接触到的Android 输入input 系统，先看一张网上的层次图，蛮不错的：




上一篇博客里面的 usbtouchscreen 就是对应上图的I2c module的位置，而在kernel中input的核心就是input.c .

input_dev：

这个结构体表述的是一个输入设备的相关信息，在usbtouchscreen 驱动中的 usbtouch_probe 会初始化input_dev,作为usbtouch设备的一部分.

会对 input_dev 做一系列的初始化，设置参数之类的，具体可参考之前博客

input_dev 结构原型如下，/kernel/include/linux/input.h中定义：
[objc] view plain copy
1. /**
2. * struct input_dev - represents an input device
3. * @name: name of the device
4. * @phys: physical path to the device in the system hierarchy
5. * @uniq: unique identification code for the device (if device has it)
6. * @id: id of the device (struct input_id)
7. * @propbit: bitmap of device properties and quirks
8. * @evbit: bitmap of types of events supported by the device (EV_KEY,
9. * EV_REL, etc.)
10. * @keybit: bitmap of keys/buttons this device has
11. * @relbit: bitmap of relative axes for the device
12. * @absbit: bitmap of absolute axes for the device
13. * @mscbit: bitmap of miscellaneous events supported by the device
14. * @ledbit: bitmap of leds present on the device
15. * @sndbit: bitmap of sound effects supported by the device
16. * @ffbit: bitmap of force feedback effects supported by the device
17. * @swbit: bitmap of switches present on the device
18. * @hint_events_per_packet: average number of events generated by the
19. * device in a packet (between EV_SYN/SYN_REPORT events). Used by
20. * event handlers to estimate size of the buffer needed to hold
21. * events.
22. * @keycodemax: size of keycode table
23. * @keycodesize: size of elements in keycode table
24. * @keycode: map of scancodes to keycodes for this device
25. * @getkeycode: optional legacy method to retrieve current keymap.
26. * @setkeycode: optional method to alter current keymap, used to implement
27. * sparse keymaps. If not supplied default mechanism will be used.
28. * The method is being called while holding event_lock and thus must
29. * not sleep
30. * @ff: force feedback structure associated with the device if device
31. * supports force feedback effects
32. * @repeat_key: stores key code of the last key pressed; used to implement
33. * software autorepeat
34. * @timer: timer for software autorepeat
35. * @rep: current values for autorepeat parameters (delay, rate)
36. * @mt: pointer to array of struct input_mt_slot holding current values
37. * of tracked contacts
38. * @mtsize: number of MT slots the device uses
39. * @slot: MT slot currently being transmitted
40. * @trkid: stores MT tracking ID for the current contact
41. * @absinfo: array of &struct input_absinfo elements holding information
42. * about absolute axes (current value, min, max, flat, fuzz,
43. * resolution)
44. * @key: reflects current state of device's keys/buttons
45. * @led: reflects current state of device's LEDs
46. * @snd: reflects current state of sound effects
47. * @sw: reflects current state of device's switches
48. * @open: this method is called when the very first user calls
49. * input_open_device(). The driver must prepare the device
50. * to start generating events (start polling thread,
51. * request an IRQ, submit URB, etc.)
52. * @close: this method is called when the very last user calls
53. * input_close_device().
54. * @flush: purges the device. Most commonly used to get rid of force
55. * feedback effects loaded into the device when disconnecting
56. * from it
57. * @event: event handler for events sent _to_ the device, like EV_LED
58. * or EV_SND. The device is expected to carry out the requested
59. * action (turn on a LED, play sound, etc.) The call is protected
60. * by @event_lock and must not sleep
61. * @grab: input handle that currently has the device grabbed (via
62. * EVIOCGRAB ioctl). When a handle grabs a device it becomes sole
63. * recipient for all input events coming from the device
64. * @event_lock: this spinlock is is taken when input core receives
65. * and processes a new event for the device (in input_event()).
66. * Code that accesses and/or modifies parameters of a device
67. * (such as keymap or absmin, absmax, absfuzz, etc.) after device
68. * has been registered with input core must take this lock.
69. * @mutex: serializes calls to open(), close() and flush() methods
70. * @users: stores number of users (input handlers) that opened this
71. * device. It is used by input_open_device() and input_close_device()
72. * to make sure that dev->open() is only called when the first
73. * user opens device and dev->close() is called when the very
74. * last user closes the device
75. * @going_away: marks devices that are in a middle of unregistering and
76. * causes input_open_device*() fail with -ENODEV.
77. * @sync: set to %true when there were no new events since last EV_SYN
78. * @dev: driver model's view of this device
79. * @h_list: list of input handles associated with the device. When
80. * accessing the list dev->mutex must be held
81. * @node: used to place the device onto input_dev_list
82. */
83. struct input_dev {
84. const charchar *name;
85. const charchar *phys;
86. const charchar *uniq;
87. struct input_id id;
89. unsigned long propbit[BITS_TO_LONGS(INPUT_PROP_CNT)];
91. unsigned long evbit[BITS_TO_LONGS(EV_CNT)];
92. unsigned long keybit[BITS_TO_LONGS(KEY_CNT)];
93. unsigned long relbit[BITS_TO_LONGS(REL_CNT)];
94. unsigned long absbit[BITS_TO_LONGS(ABS_CNT)];
95. unsigned long mscbit[BITS_TO_LONGS(MSC_CNT)];
96. unsigned long ledbit[BITS_TO_LONGS(LED_CNT)];
97. unsigned long sndbit[BITS_TO_LONGS(SND_CNT)];
98. unsigned long ffbit[BITS_TO_LONGS(FF_CNT)];
99. unsigned long swbit[BITS_TO_LONGS(SW_CNT)];
101. unsigned int hint_events_per_packet;
103. unsigned int keycodemax;
104. unsigned int keycodesize;
105. voidvoid *keycode;
107. int (*setkeycode)(struct input_dev *dev,
108. const struct input_keymap_entry *ke,
109. unsigned intint *old_keycode);
110. int (*getkeycode)(struct input_dev *dev,
111. struct input_keymap_entry *ke);
113. struct ff_device *ff;
115. unsigned int repeat_key;
116. struct timer_list timer;
118. int rep[REP_CNT];
120. struct input_mt_slot *mt;
121. int mtsize;
122. int slot;
123. int trkid;
125. struct input_absinfo *absinfo;
127. unsigned long key[BITS_TO_LONGS(KEY_CNT)];
128. unsigned long led[BITS_TO_LONGS(LED_CNT)];
129. unsigned long snd[BITS_TO_LONGS(SND_CNT)];
130. unsigned long sw[BITS_TO_LONGS(SW_CNT)];
132. int (*open)(struct input_dev *dev);
133. void (*close)(struct input_dev *dev);
134. int (*flush)(struct input_dev *dev, struct file *file);
135. int (*event)(struct input_dev *dev, unsigned int type, unsigned int code, int value);
137. struct input_handle __rcu *grab;
139. spinlock_t event_lock;
140. struct mutex mutex;
142. unsigned int users;
143. bool going_away;
145. bool sync;
147. struct device dev;
149. struct list_head h_list;
150. struct list_head node;
151. };
我解释可能还会误导，源码上面的注释是最好的解释，都是描述一个input 设备的相关信息.

每一个input设备，都需要初始化一个这样的input_dev结构来描述记录此设备的一些特性，然后通过input_register_device 注册到设备总线上以供后续使用

可以到系统运行目录的/proc/bus/input下 cat devices 查看总线上的已经注册上的input device

input_event：

设备驱动部分往上传递的就是触发的event事件了，还以usbtouchscreen的为例，回调函数为：
[objc] view plain copy
1. /*****************************************************************************
2. * Generic Part
3. */
4. static void usbtouch_process_pkt(struct usbtouch_usb *usbtouch,
5. unsigned charchar *pkt, int len)
6. {
7. struct usbtouch_device_info *type = usbtouch->type;
9. if (!type->read_data(usbtouch, pkt))
10. return;
12. input_report_key(usbtouch->input, BTN_TOUCH, usbtouch->touch); // 上报触摸类型。touch为按下
14. if (swap_xy) {
15. input_report_abs(usbtouch->input, ABS_X, usbtouch->y);
16. input_report_abs(usbtouch->input, ABS_Y, usbtouch->x);
17. } else {
18. input_report_abs(usbtouch->input, ABS_X, usbtouch->x);
19. input_report_abs(usbtouch->input, ABS_Y, usbtouch->y); // 上报绝对坐标值
20. }
21. if (type->max_press)
22. input_report_abs(usbtouch->input, ABS_PRESSURE, usbtouch->press);
23. input_sync(usbtouch->input); // 同步操作
24. }
可以看到通过 input_report_* 上报事件到input.c中，这也就是上面层次图中的箭头 9 ，初始在/kernel/include/linux/input.h：
[objc] view plain copy
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. }
6. static inline void input_report_rel(struct input_dev *dev, unsigned int code, int value)
7. {
8. input_event(dev, EV_REL, code, value);
9. }
11. static inline void input_report_abs(struct input_dev *dev, unsigned int code, int value)
12. {
13. input_event(dev, EV_ABS, code, value);
14. }
可以看到不同的report 都调用进了input_event，只是传参不同，接下来的事就全交由input.c 来做了！
[objc] view plain copy
1. /**
2. * input_event() - report new input event
3. * @dev: device that generated the event
4. * @type: type of the event
5. * @code: event code
6. * @value: value of the event
7. *
8. * This function should be used by drivers implementing various input
9. * devices to report input events. See also input_inject_event().
10. *
11. * NOTE: input_event() may be safely used right after input device was
12. * allocated with input_allocate_device(), even before it is registered
13. * with input_register_device(), but the event will not reach any of the
14. * input handlers. Such early invocation of input_event() may be used
15. * to 'seed' initial state of a switch or initial position of absolute
16. * axis, etc.
17. */
18. void input_event(struct input_dev *dev,
19. unsigned int type, unsigned int code, int value)
20. {
21. unsigned long flags;
23. if (is_event_supported(type, dev->evbit, EV_MAX)) { //判断是否是注册时的event类型，驱动probe时注册input_dev时设置了能响应的event类型
25. spin_lock_irqsave(&dev->event_lock, flags); //自旋锁枷锁
27. add_input_randomness(type, code, value);
28. input_handle_event(dev, type, code, value); //进一步处理传上来的这个 event
29. spin_unlock_irqrestore(&dev->event_lock, flags);//解锁
30. }
31. }
可以看到在这里首先就是过滤了事件类型，这个也是在usbtouchscreen中的probe中初始化过的！

类型有如下几种：
[objc] view plain copy
1. /*
2. * Event types
3. */
5. #define EV_SYN 0x00
6. #define EV_KEY 0x01
7. #define EV_REL 0x02
8. #define EV_ABS 0x03
9. #define EV_MSC 0x04
10. #define EV_SW 0x05
11. #define EV_LED 0x11
12. #define EV_SND 0x12
13. #define EV_REP 0x14
14. #define EV_FF 0x15
15. #define EV_PWR 0x16
16. #define EV_FF_STATUS 0x17
17. #define EV_MAX 0x1f
18. #define EV_CNT (EV_MAX+1)
input_handle_event：

由上面的input_event 调入进这个handle处理。这里会根据type进行分类处理：
[objc] view plain copy
1. static void input_handle_event(struct input_dev *dev,
2. unsigned int type, unsigned int code, int value)
3. {
4. int disposition = INPUT_IGNORE_EVENT; //初始为不做处理
6. switch (type) {
8. case EV_SYN:
9. switch (code) {
10. case SYN_CONFIG:
11. disposition = INPUT_PASS_TO_ALL;
12. break;
14. case SYN_REPORT:
15. if (!dev->sync) {
16. dev->sync = true;
17. disposition = INPUT_PASS_TO_HANDLERS;
18. }
19. break;
21. ...
23. case EV_KEY:
25. if (is_event_supported(code, dev->keybit, KEY_MAX) && //按键code是否被keybit支持
26. !!test_bit(code, dev->key) != value) { //key是键盘当前所有键状态，测试code对应键状态，value传来事件的按键状态。此句表示按键状态应有变化
28. if (value != 2) {
29. __change_bit(code, dev->key); //改变key的值以改变按键状态。
30. if (value)
31. input_start_autorepeat(dev, code); //如果按键值为按下，则开始重复按键操作。具体会不会重复，input_start_autorepeat还会根据evbit中有没有置位重复事件等判断。
32. else
33. input_stop_autorepeat(dev); //如果是松开按键则应停止重复按键相关操作。
34. }
36. disposition = INPUT_PASS_TO_HANDLERS;
37. }
38. break;
40. ...
42. case EV_ABS:
43. if (is_event_supported(code, dev->absbit, ABS_MAX)) //同上面一样看是否支持
44. disposition = input_handle_abs_event(dev, code, &value); //这个函数可以跟进去看，是做为筛选的，第一次是不会返回INPUT_IGNORE_EVENT ，后面如果有跟上次相同的ABS坐标就会被过滤掉，返回IGNORE
45. // err("jscese display disposition vlue ==0x%x,code==0x%x, value== 0x%x ",disposition,code,value);
46. break;
48. ...
50. }
52. if (disposition != INPUT_IGNORE_EVENT && type != EV_SYN)
53. dev->sync = false;
55. if ((disposition & INPUT_PASS_TO_DEVICE) && dev->event)
56. dev->event(dev, type, code, value);
58. if (disposition & INPUT_PASS_TO_HANDLERS)
59. input_pass_event(dev, type, code, value); //更深一步调用，最终都是调用到 event(**)方法
61. }
这里先记录整个输入系统从设备驱动到上层的关系，以及从kernel中的驱动调用到input系统中的传递过程，虽然看到调用了input.c中的一些函数传递，但是对input核心还是没多少概念，

下篇解析记录一下input这个核心模块～
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原文地址：https://www.cnblogs.com/zzb-Dream-90Time/p/7808406.html

Linux/Android——输入子系统input_event传递 (二)【转】

input_dev：

input_event：

input_handle_event：