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

/**

* struct input_dev - represents an input device

* @name: name of the device

* @phys: physical path to the device in the system hierarchy

* @uniq: unique identification code for the device (if device has it)

* @id: id of the device (struct input_id)

* @propbit: bitmap of device properties and quirks

* @evbit: bitmap of types of events supported by the device (EV_KEY,

* EV_REL, etc.)

* @keybit: bitmap of keys/buttons this device has

* @relbit: bitmap of relative axes for the device

* @absbit: bitmap of absolute axes for the device

* @mscbit: bitmap of miscellaneous events supported by the device

* @ledbit: bitmap of leds present on the device

* @sndbit: bitmap of sound effects supported by the device

* @ffbit: bitmap of force feedback effects supported by the device

* @swbit: bitmap of switches present on the device

* @hint_events_per_packet: average number of events generated by the

* device in a packet (between EV_SYN/SYN_REPORT events). Used by

* event handlers to estimate size of the buffer needed to hold

* events.

* @keycodemax: size of keycode table

* @keycodesize: size of elements in keycode table

* @keycode: map of scancodes to keycodes for this device

* @getkeycode: optional legacy method to retrieve current keymap.

* @setkeycode: optional method to alter current keymap, used to implement

* sparse keymaps. If not supplied default mechanism will be used.

* The method is being called while holding event_lock and thus must

* not sleep

* @ff: force feedback structure associated with the device if device

* supports force feedback effects

* @repeat_key: stores key code of the last key pressed; used to implement

* software autorepeat

* @timer: timer for software autorepeat

* @rep: current values for autorepeat parameters (delay, rate)

* @mt: pointer to array of struct input_mt_slot holding current values

* of tracked contacts

* @mtsize: number of MT slots the device uses

* @slot: MT slot currently being transmitted

* @trkid: stores MT tracking ID for the current contact

* @absinfo: array of &struct input_absinfo elements holding information

* about absolute axes (current value, min, max, flat, fuzz,

* resolution)

* @key: reflects current state of device's keys/buttons

* @led: reflects current state of device's LEDs

* @snd: reflects current state of sound effects

* @sw: reflects current state of device's switches

* @open: this method is called when the very first user calls

* input_open_device(). The driver must prepare the device

* to start generating events (start polling thread,

* request an IRQ, submit URB, etc.)

* @close: this method is called when the very last user calls

* input_close_device().

* @flush: purges the device. Most commonly used to get rid of force

* feedback effects loaded into the device when disconnecting

* from it

* @event: event handler for events sent _to_ the device, like EV_LED

* or EV_SND. The device is expected to carry out the requested

* action (turn on a LED, play sound, etc.) The call is protected

* by @event_lock and must not sleep

* @grab: input handle that currently has the device grabbed (via

* EVIOCGRAB ioctl). When a handle grabs a device it becomes sole

* recipient for all input events coming from the device

* @event_lock: this spinlock is is taken when input core receives

* and processes a new event for the device (in input_event()).

* Code that accesses and/or modifies parameters of a device

* (such as keymap or absmin, absmax, absfuzz, etc.) after device

* has been registered with input core must take this lock.

* @mutex: serializes calls to open(), close() and flush() methods

* @users: stores number of users (input handlers) that opened this

* device. It is used by input_open_device() and input_close_device()

* to make sure that dev->open() is only called when the first

* user opens device and dev->close() is called when the very

* last user closes the device

* @going_away: marks devices that are in a middle of unregistering and

* causes input_open_device*() fail with -ENODEV.

* @sync: set to %true when there were no new events since last EV_SYN

* @dev: driver model's view of this device

* @h_list: list of input handles associated with the device. When

* accessing the list dev->mutex must be held

* @node: used to place the device onto input_dev_list

*/

struct input_dev {

const charchar *name;

const charchar *phys;

const charchar *uniq;

struct input_id id;

unsigned long propbit[BITS_TO_LONGS(INPUT_PROP_CNT)];

unsigned long evbit[BITS_TO_LONGS(EV_CNT)];

unsigned long keybit[BITS_TO_LONGS(KEY_CNT)];

unsigned long relbit[BITS_TO_LONGS(REL_CNT)];

unsigned long absbit[BITS_TO_LONGS(ABS_CNT)];

unsigned long mscbit[BITS_TO_LONGS(MSC_CNT)];

unsigned long ledbit[BITS_TO_LONGS(LED_CNT)];

unsigned long sndbit[BITS_TO_LONGS(SND_CNT)];

unsigned long ffbit[BITS_TO_LONGS(FF_CNT)];

unsigned long swbit[BITS_TO_LONGS(SW_CNT)];

unsigned int hint_events_per_packet;

unsigned int keycodemax;

unsigned int keycodesize;

voidvoid *keycode;

int (*setkeycode)(struct input_dev *dev,

const struct input_keymap_entry *ke,

unsigned intint *old_keycode);

int (*getkeycode)(struct input_dev *dev,

struct input_keymap_entry *ke);

struct ff_device *ff;

unsigned int repeat_key;

struct timer_list timer;

int rep[REP_CNT];

struct input_mt_slot *mt;

int mtsize;

int slot;

int trkid;

struct input_absinfo *absinfo;

unsigned long key[BITS_TO_LONGS(KEY_CNT)];

unsigned long led[BITS_TO_LONGS(LED_CNT)];

unsigned long snd[BITS_TO_LONGS(SND_CNT)];

unsigned long sw[BITS_TO_LONGS(SW_CNT)];

int (*open)(struct input_dev *dev);

void (*close)(struct input_dev *dev);

int (*flush)(struct input_dev *dev, struct file *file);

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

struct input_handle __rcu *grab;

spinlock_t event_lock;

struct mutex mutex;

unsigned int users;

bool going_away;

bool sync;

struct device dev;

struct list_head h_list;

struct list_head node;

};

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

/*****************************************************************************

* Generic Part

*/

static void usbtouch_process_pkt(struct usbtouch_usb *usbtouch,

unsigned charchar *pkt, int len)

{

struct usbtouch_device_info *type = usbtouch->type;

if (!type->read_data(usbtouch, pkt))

return;

input_report_key(usbtouch->input, BTN_TOUCH, usbtouch->touch); // 上报触摸类型 。touch为按下

if (swap_xy) {

input_report_abs(usbtouch->input, ABS_X, usbtouch->y);

input_report_abs(usbtouch->input, ABS_Y, usbtouch->x);

} else {

input_report_abs(usbtouch->input, ABS_X, usbtouch->x);

input_report_abs(usbtouch->input, ABS_Y, usbtouch->y); // 上报绝对坐标值

}

if (type->max_press)

input_report_abs(usbtouch->input, ABS_PRESSURE, usbtouch->press);

input_sync(usbtouch->input); // 同步操作

}

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

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

{

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

}

static inline void input_report_rel(struct input_dev *dev, unsigned int code, int value)

{

input_event(dev, EV_REL, code, value);

}

static inline void input_report_abs(struct input_dev *dev, unsigned int code, int value)

{

input_event(dev, EV_ABS, code, value);

}

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

/**

* input_event() - report new input event

* @dev: device that generated the event

* @type: type of the event

* @code: event code

* @value: value of the event

*

* This function should be used by drivers implementing various input

* devices to report input events. See also input_inject_event().

*

* NOTE: input_event() may be safely used right after input device was

* allocated with input_allocate_device(), even before it is registered

* with input_register_device(), but the event will not reach any of the

* input handlers. Such early invocation of input_event() may be used

* to 'seed' initial state of a switch or initial position of absolute

* axis, etc.

*/

void input_event(struct input_dev *dev,

unsigned int type, unsigned int code, int value)

{

unsigned long flags;

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

spin_lock_irqsave(&dev->event_lock, flags); //自旋锁枷锁

add_input_randomness(type, code, value);

input_handle_event(dev, type, code, value); //进一步处理传上来的这个 event

spin_unlock_irqrestore(&dev->event_lock, flags);//解锁

}

}

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

/*

* Event types

*/

#define EV_SYN 0x00

#define EV_KEY 0x01

#define EV_REL 0x02

#define EV_ABS 0x03

#define EV_MSC 0x04

#define EV_SW 0x05

#define EV_LED 0x11

#define EV_SND 0x12

#define EV_REP 0x14

#define EV_FF 0x15

#define EV_PWR 0x16

#define EV_FF_STATUS 0x17

#define EV_MAX 0x1f

#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

static void input_handle_event(struct input_dev *dev,

unsigned int type, unsigned int code, int value)

{

int disposition = INPUT_IGNORE_EVENT; //初始为不做处理

switch (type) {

case EV_SYN:

switch (code) {

case SYN_CONFIG:

disposition = INPUT_PASS_TO_ALL;

break;

case SYN_REPORT:

if (!dev->sync) {

dev->sync = true;

disposition = INPUT_PASS_TO_HANDLERS;

}

break;

...

case EV_KEY:

if (is_event_supported(code, dev->keybit, KEY_MAX) && //按键code是否被keybit支持

!!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

if (value != 2) {

__change_bit(code, dev->key); //改变key的值以改变按键状态。

if (value)

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。

else

input_stop_autorepeat(dev); //如果是松开按键则应停止重复按键相关操作。

}

disposition = INPUT_PASS_TO_HANDLERS;

}

break;

...

case EV_ABS:

if (is_event_supported(code, dev->absbit, ABS_MAX)) //同上面一样看是否支持

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

// err("jscese display disposition vlue ==0x%x,code==0x%x, value== 0x%x\n",disposition,code,value);

break;

...

}

if (disposition != INPUT_IGNORE_EVENT && type != EV_SYN)

dev->sync = false;

if ((disposition & INPUT_PASS_TO_DEVICE) && dev->event)

dev->event(dev, type, code, value);

if (disposition & INPUT_PASS_TO_HANDLERS)

input_pass_event(dev, type, code, value); //更深一步调用 ，最终都是 调用到 event(**)方法

}

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～