Linux输入子系统输入核心层源码简要剖析

本文详细解析了Linux输入子系统的内部结构,包括input_dev、input_handle和input_handler三个核心结构体的作用及相互关系,深入探讨了input核心的主要操作流程。

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_________ _        _______          _________
\__   __/( (    /|(  ____ )|\     /|\__   __/
   ) (   |  \  ( || (    )|| )   ( |   ) (   
   | |   |   \ | || (____)|| |   | |   | |   
   | |   | (\ \) ||  _____)| |   | |   | |   
   | |   | | \   || (      | |   | |   | |   
___) (___| )  \  || )      | (___) |   | |   
\_______/|/    )_)|/       (_______)   )_(   

 _______           ______   _______           _______ 
(  ____ \|\     /|(  ___ \ (  ____ \|\     /|(  ____ \
| (    \/| )   ( || (   ) )| (    \/( \   / )| (    \/
| (_____ | |   | || (__/ / | (_____  \ (_) / | (_____ 
(_____  )| |   | ||  __ (  (_____  )  \   /  (_____  )
      ) || |   | || (  \ \       ) |   ) (         ) |
/\____) || (___) || )___) )/\____) |   | |   /\____) |
\_______)(_______)|/ \___/ \_______)   \_/   \_______)

想要读懂Linux输入子系统的源码需要先明确三个结构体:

input_handle建立 input_dev 和 input_handler的联系,通过两个list保存系统中所有的device和 handler。

/**
 * struct input_handle - links input device with an input handler
 * @private: handler-specific data
 * @open: counter showing whether the handle is 'open', i.e. should deliver
 *  events from its device
 * @name: name given to the handle by handler that created it
 * @dev: input device the handle is attached to
 * @handler: handler that works with the device through this handle
 * @d_node: used to put the handle on device's list of attached handles
 * @h_node: used to put the handle on handler's list of handles from which
 *  it gets events
 */
struct input_handle {
    void *private;
    int open;
    const char *name;
    struct input_dev *dev;
    struct input_handler *handler;
  struct list_head  d_node;
    struct list_head    h_node;
};

input_dev表征一个输入设备:
在向InputCore注册一个输入设备前,需要先分配一个此结构体并且初始化某些值,如设置按键类型,按键值等。如需要定时操作,初始化timer_list,这样就可以进行定时操作了。

/**
 * 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 multitouch state
 * @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 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.
 * @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
 * @num_vals: number of values queued in the current frame
 * @max_vals: maximum number of values queued in a frame
 * @vals: array of values queued in the current frame
 * @devres_managed: indicates that devices is managed with devres framework
 *  and needs not be explicitly unregistered or freed.
 */
struct input_dev {
    const char *name;
    const char *phys;
    const char *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;
    void *keycode;
    int (*setkeycode)(struct input_dev *dev,
              const struct input_keymap_entry *ke,
              unsigned int *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 *mt;
    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; struct device dev; struct list_head h_list; struct list_head node; unsigned int num_vals; unsigned int max_vals; struct input_value *vals; bool devres_managed; }; #define to_input_dev(d) container_of(d, struct input_dev, dev)

input_handler

/**
 * struct input_handler - implements one of interfaces for input devices
 * @private: driver-specific data
 * @event: event handler. This method is being called by input core with
 *  interrupts disabled and dev->event_lock spinlock held and so
 *  it may not sleep
 * @events: event sequence handler. This method is being called by
 *  input core with interrupts disabled and dev->event_lock
 *  spinlock held and so it may not sleep
 * @filter: similar to @event; separates normal event handlers from
 *  "filters".
 * @match: called after comparing device's id with handler's id_table
 *  to perform fine-grained matching between device and handler
 * @connect: called when attaching a handler to an input device
 * @disconnect: disconnects a handler from input device
 * @start: starts handler for given handle. This function is called by
 *  input core right after connect() method and also when a process
 *  that "grabbed" a device releases it
 * @legacy_minors: set to %true by drivers using legacy minor ranges
 * @minor: beginning of range of 32 legacy minors for devices this driver
 *  can provide
 * @name: name of the handler, to be shown in /proc/bus/input/handlers
 * @id_table: pointer to a table of input_device_ids this driver can
 *  handle
 * @h_list: list of input handles associated with the handler
 * @node: for placing the driver onto input_handler_list
 *
 * Input handlers attach to input devices and create input handles. There
 * are likely several handlers attached to any given input device at the
 * same time. All of them will get their copy of input event generated by
 * the device.
 *
 * The very same structure is used to implement input filters. Input core
 * allows filters to run first and will not pass event to regular handlers
 * if any of the filters indicate that the event should be filtered (by
 * returning %true from their filter() method).
 *
 * Note that input core serializes calls to connect() and disconnect()
 * methods.
 */
struct input_handler {

    void *private;

    void (*event)(struct input_handle *handle, unsigned int type, unsigned int code, int value);
    void (*events)(struct input_handle *handle,
               const struct input_value *vals, unsigned int count);
    bool (*filter)(struct input_handle *handle, unsigned int type, unsigned int code, int value);
    bool (*match)(struct input_handler *handler, struct input_dev *dev);
    int (*connect)(struct input_handler *handler, struct input_dev *dev, const struct input_device_id *id); void (*disconnect)(struct input_handle *handle); void (*start)(struct input_handle *handle); bool legacy_minors; int minor; const char *name; const struct input_device_id *id_table; struct list_head h_list; struct list_head node; };

以下是inputcore的源码,我们需要着重关注,进行了中文注释的部分, 以及 register_input_deviceregister_input_handlerattach_to_handlerinput_handle_event等几个关键操作:

/*
 * The input core
 *
 * Copyright (c) 1999-2002 Vojtech Pavlik
 */

/*
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published by
 * the Free Software Foundation.
 */

#define pr_fmt(fmt) KBUILD_BASENAME ": " fmt

#include <linux/init.h>
#include <linux/types.h>
#include <linux/idr.h>
#include <linux/input/mt.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/random.h>
#include <linux/major.h>
#include <linux/proc_fs.h>
#include <linux/sched.h>
#include <linux/seq_file.h>
#include <linux/poll.h>
#include <linux/device.h>
#include <linux/mutex.h>
#include <linux/rcupdate.h>
#include "input-compat.h"

MODULE_AUTHOR("Vojtech Pavlik <vojtech@suse.cz>");
MODULE_DESCRIPTION("Input core");
MODULE_LICENSE("GPL");

#define INPUT_MAX_CHAR_DEVICES      1024
#define INPUT_FIRST_DYNAMIC_DEV     256
static DEFINE_IDA(input_ida);

static LIST_HEAD(input_dev_list);       //初始化设备列表
static LIST_HEAD(input_handler_list);   //初始化handler列表

/*
 * input_mutex protects access to both input_dev_list and input_handler_list.
 * This also causes input_[un]register_device and input_[un]register_handler
 * be mutually exclusive which simplifies locking in drivers implementing
 * input handlers.
 */
static DEFINE_MUTEX(input_mutex);       //在 input_[un]register_device input_[un]register_handler 起保护作用

static const struct input_value input_value_sync = { EV_SYN, SYN_REPORT, 1 };

static inline int is_event_supported(unsigned int code,
                     unsigned long *bm, unsigned int max)
{
    return code <= max && test_bit(code, bm);           //没超过事件的最大值,并且 1 << code & *bm != 0
}

//模糊绝对坐标
static int input_defuzz_abs_event(int value, int old_val, int fuzz)
{
    if (fuzz) {
        if (value > old_val - fuzz / 2 && value < old_val + fuzz / 2)
            return old_val;

        if (value > old_val - fuzz && value < old_val + fuzz)
            return (old_val * 3 + value) / 4;

        if (value > old_val - fuzz * 2 && value < old_val + fuzz * 2)
            return (old_val + value) / 2;
    }

    return value;
}

//自动重复做某一事件码,在设备驱动中我们可以调用此借口使核心层定时上传event,而不用在设备驱动中使用定时器
static void input_start_autorepeat(struct input_dev *dev, int code)
{
    if (test_bit(EV_REP, dev->evbit) &&
        dev->rep[REP_PERIOD] && dev->rep[REP_DELAY] &&
        dev->timer.data) {
        dev->repeat_key = code;
        mod_timer(&dev->timer,
              jiffies + msecs_to_jiffies(dev->rep[REP_DELAY])); //ms转jiffies
    }
}

//停止自动重复
static void input_stop_autorepeat(struct input_dev *dev)
{
    del_timer(&dev->timer);
}

/*
 * Pass event first through all filters and then, if event has not been
 * filtered out, through all open handles. This function is called with
 * dev->event_lock held and interrupts disabled.
 */
//由input得到对应的handler,怎么得到呢?就是查看由所有handler的filter函数决定,
//如果某一个handler能够处理某一类型的event 和 code
static unsigned int input_to_handler(struct input_handle *handle,
            struct input_value *vals, unsigned int count)
{
    struct input_handler *handler = handle->handler;
    struct input_value *end = vals;
    struct input_value *v;

    if (handler->filter) {
        for (v = vals; v != vals + count; v++) {
            if (handler->filter(handle, v->type, v->code, v->value))
                continue;
            if (end != v)
                *end = *v;
            end++;      //如果上面有一个通过-continue,那么 count = 0;,直接返回0
        }
        count = end - vals;
    }

    if (!count)
        return 0;

    //如果handler函数实现的序列处理,那么就调用序列处理,否则以一个调用event
    if (handler->events)
        handler->events(handle, vals, count);
    else if (handler->event)
        for (v = vals; v != vals + count; v++)
            handler->event(handle, v->type, v->code, v->value);

    return count;
}

/*
 * Pass values first through all filters and then, if event has not been
 * filtered out, through all open handles. This function is called with
 * dev->event_lock held and interrupts disabled.
 */
//上传某一个值的时候,需要先通过所有的filter
static void input_pass_values(struct input_dev *dev,
                  struct input_value *vals, unsigned int count)
{
    struct input_handle *handle;
    struct input_value *v;

    if (!count)
        return;

    rcu_read_lock();

    handle = rcu_dereference(dev->grab);
    if (handle) {
        //如果传入参数指定了handl,那么就传人指定的handle,否则在列表中一个个尝试
        count = input_to_handler(handle, vals, count);
    } else {
        list_for_each_entry_rcu(handle, &dev->h_list, d_node)
            if (handle->open) {
                count = input_to_handler(handle, vals, count);
                if (!count)
                    break;
            }
    }

    rcu_read_unlock();

    /* trigger auto repeat for key events */
    //如果该设备设置了重复位,就启动重复上传
    if (test_bit(EV_REP, dev->evbit) && test_bit(EV_KEY, dev->evbit)) {
        for (v = vals; v != vals + count; v++) {
            if (v->type == EV_KEY && v->value != 2) {
                if (v->value)
                    input_start_autorepeat(dev, v->code);
                else
                    input_stop_autorepeat(dev);
            }
        }
    }
}

static void input_pass_event(struct input_dev *dev,
                 unsigned int type, unsigned int code, int value)
{
    struct input_value vals[] = { { type, code, value } };

    input_pass_values(dev, vals, ARRAY_SIZE(vals));
}

/*
 * Generate software autorepeat event. Note that we take
 * dev->event_lock here to avoid racing with input_event
 * which may cause keys get "stuck".
 */
//重复上传事件的具体实现函数,在上传事件后,修改定时器
//前面的auto_repeat_start只是启动了重复上传的定时器,并没有上传具体事件(值)
//注意在这里会使用自旋锁防止竞争
static void input_repeat_key(unsigned long data)
{
    struct input_dev *dev = (void *) data;
    unsigned long flags;

    spin_lock_irqsave(&dev->event_lock, flags); //在得到锁之后会保存中断信息

    if (test_bit(dev->repeat_key, dev->key) &&
        is_event_supported(dev->repeat_key, dev->keybit, KEY_MAX)) {
        struct input_value vals[] =  {
            { EV_KEY, dev->repeat_key, 2 },
            input_value_sync
        };

        input_pass_values(dev, vals, ARRAY_SIZE(vals));

        if (dev->rep[REP_PERIOD])
            mod_timer(&dev->timer, jiffies +
                    msecs_to_jiffies(dev->rep[REP_PERIOD]));
    }

    spin_unlock_irqrestore(&dev->event_lock, flags);    //还原中断信息,为的是在得到锁的期间的其他输入在之后能够接着被处理
}

#define INPUT_IGNORE_EVENT  0
#define INPUT_PASS_TO_HANDLERS  1
#define INPUT_PASS_TO_DEVICE    2
#define INPUT_SLOT      4
#define INPUT_FLUSH     8
#define INPUT_PASS_TO_ALL   (INPUT_PASS_TO_HANDLERS | INPUT_PASS_TO_DEVICE)

//ABS事件的处理函数,在input_get_disposition函数中根据事件类型进行调用,
//在该函数中并没有与handler进行交互
static int input_handle_abs_event(struct input_dev *dev,
                  unsigned int code, int *pval)
{
    struct input_mt *mt = dev->mt;
    bool is_mt_event;
    int *pold;

    if (code == ABS_MT_SLOT) {
        /*
         * "Stage" the event; we'll flush it later, when we
         * get actual touch data.
         */
        if (mt && *pval >= 0 && *pval < mt->num_slots)
            mt->slot = *pval;

        return INPUT_IGNORE_EVENT;
    }

    is_mt_event = input_is_mt_value(code);

    if (!is_mt_event) {
        pold = &dev->absinfo[code].value;
    } else if (mt) {
        pold = &mt->slots[mt->slot].abs[code - ABS_MT_FIRST];
    } else {
        /*
         * Bypass filtering for multi-touch events when
         * not employing slots.
         */
        pold = NULL;
    }

    if (pold) {
        *pval = input_defuzz_abs_event(*pval, *pold,
                        dev->absinfo[code].fuzz);
        if (*pold == *pval)
            return INPUT_IGNORE_EVENT;

        *pold = *pval;
    }

    /* Flush pending "slot" event */
    if (is_mt_event && mt && mt->slot != input_abs_get_val(dev, ABS_MT_SLOT)) {
        input_abs_set_val(dev, ABS_MT_SLOT, mt->slot);
        return INPUT_PASS_TO_HANDLERS | INPUT_SLOT;
    }

    return INPUT_PASS_TO_HANDLERS;
}

//得到事件要发送的目的地
static int input_get_disposition(struct input_dev *dev,
              unsigned int type, unsigned int code, int *pval)
{
    int disposition = INPUT_IGNORE_EVENT;
    int value = *pval;

    switch (type) {

    case EV_SYN:
        switch (code) {
        case SYN_CONFIG:
            disposition = INPUT_PASS_TO_ALL;
            break;

        case SYN_REPORT:
            disposition = INPUT_PASS_TO_HANDLERS | INPUT_FLUSH;
            break;
        case SYN_MT_REPORT:
            disposition = INPUT_PASS_TO_HANDLERS;
            break;
        }
        break;

    case EV_KEY:
        if (is_event_supported(code, dev->keybit, KEY_MAX)) {

            /* auto-repeat bypasses state updates */
            //按键事件值不是2的时候,就直接传送给所有的handler
            if (value == 2) {
                disposition = INPUT_PASS_TO_HANDLERS;
                break;
            }
            //不是2时,进行相应转换,即 value转换为 1<<value,
            //在设备驱动层与handler的值表示方法有差异, n = 1<<n
            if (!!test_bit(code, dev->key) != !!value) {
                __change_bit(code, dev->key);
                disposition = INPUT_PASS_TO_HANDLERS;
            }
        }
        break;

    case EV_SW:
        if (is_event_supported(code, dev->swbit, SW_MAX) &&
            !!test_bit(code, dev->sw) != !!value) {

            __change_bit(code, dev->sw);
            disposition = INPUT_PASS_TO_HANDLERS;
        }
        break;

    case EV_ABS:
        if (is_event_supported(code, dev->absbit, ABS_MAX))
            disposition = input_handle_abs_event(dev, code, &value);

        break;

    case EV_REL:
        if (is_event_supported(code, dev->relbit, REL_MAX) && value)
            disposition = INPUT_PASS_TO_HANDLERS;

        break;

    case EV_MSC:
        if (is_event_supported(code, dev->mscbit, MSC_MAX))
            disposition = INPUT_PASS_TO_ALL;

        break;

    case EV_LED:
        if (is_event_supported(code, dev->ledbit, LED_MAX) &&
            !!test_bit(code, dev->led) != !!value) {

            __change_bit(code, dev->led);
            disposition = INPUT_PASS_TO_ALL;
        }
        break;

    case EV_SND:
        if (is_event_supported(code, dev->sndbit, SND_MAX)) {

            if (!!test_bit(code, dev->snd) != !!value)
                __change_bit(code, dev->snd);
            disposition = INPUT_PASS_TO_ALL;
        }
        break;

    case EV_REP:
        if (code <= REP_MAX && value >= 0 && dev->rep[code] != value) {
            dev->rep[code] = value;
            disposition = INPUT_PASS_TO_ALL;
        }
        break;

    case EV_FF:
        if (value >= 0)
            disposition = INPUT_PASS_TO_ALL;
        break;

    case EV_PWR:
        disposition = INPUT_PASS_TO_ALL;
        break;
    }

    *pval = value;
    return disposition;
}
/******************************************************************************/
//该函数为核心层事件处理的核心函数,依据 设备 事件类型 事件值 进行相应的上传
static void input_handle_event(struct input_dev *dev,
                   unsigned int type, unsigned int code, int value)
{
    int disposition = input_get_disposition(dev, type, code, &value);

    if (disposition != INPUT_IGNORE_EVENT && type != EV_SYN)
        add_input_randomness(type, code, value);

    if ((disposition & INPUT_PASS_TO_DEVICE) && dev->event)
        dev->event(dev, type, code, value);

    if (!dev->vals)
        return;

    //传送给handler的事件处理
    if (disposition & INPUT_PASS_TO_HANDLERS) {
        struct input_value *v;

        if (disposition & INPUT_SLOT) {
            v = &dev->vals[dev->num_vals++];
            v->type = EV_ABS;
            v->code = ABS_MT_SLOT;
            v->value = dev->mt->slot;
        }

        v = &dev->vals[dev->num_vals++];
        v->type = type;
        v->code = code;
        v->value = value;
    }

    if (disposition & INPUT_FLUSH) {
        if (dev->num_vals >= 2)
            input_pass_values(dev, dev->vals, dev->num_vals);
        dev->num_vals = 0;
    } else if (dev->num_vals >= dev->max_vals - 2) {
        dev->vals[dev->num_vals++] = input_value_sync;
        input_pass_values(dev, dev->vals, dev->num_vals);
        dev->num_vals = 0;
    }

}

/**
 * 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.
 */
//调用上一个函数,只不过加了自旋锁保护,同时也是一个对外的接口
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)) {

        spin_lock_irqsave(&dev->event_lock, flags);
        input_handle_event(dev, type, code, value);
        spin_unlock_irqrestore(&dev->event_lock, flags);
    }
}
EXPORT_SYMBOL(input_event);

/**
 * input_inject_event() - send input event from input handler
 * @handle: input handle to send event through
 * @type: type of the event
 * @code: event code
 * @value: value of the event
 *
 * Similar to input_event() but will ignore event if device is
 * "grabbed" and handle injecting event is not the one that owns
 * the device.
 */
//这个是handler调用的事件处理接口,当某一个handler不能处理上传给它的一个事件时、
//可以调用这个接口,进行反馈
void input_inject_event(struct input_handle *handle,
            unsigned int type, unsigned int code, int value)
{
    struct input_dev *dev = handle->dev;
    struct input_handle *grab;
    unsigned long flags;

    if (is_event_supported(type, dev->evbit, EV_MAX)) {
        spin_lock_irqsave(&dev->event_lock, flags);

        rcu_read_lock();
        grab = rcu_dereference(dev->grab);
        if (!grab || grab == handle)
            input_handle_event(dev, type, code, value);
        rcu_read_unlock();

        spin_unlock_irqrestore(&dev->event_lock, flags);
    }
}
EXPORT_SYMBOL(input_inject_event);

/**
 * input_alloc_absinfo - allocates array of input_absinfo structs
 * @dev: the input device emitting absolute events
 *
 * If the absinfo struct the caller asked for is already allocated, this
 * functions will not do anything.
 */
//为abs事件分配 abs_info结构体
//在input_set_abs_params中调用,这也就意味着如果你有ABS事件,那么你需要调用set_params接口
void input_alloc_absinfo(struct input_dev *dev)
{
    if (!dev->absinfo)
        dev->absinfo = kcalloc(ABS_CNT, sizeof(*dev->absinfo),
                    GFP_KERNEL);

    WARN(!dev->absinfo, "%s(): kcalloc() failed?\n", __func__);
}
EXPORT_SYMBOL(input_alloc_absinfo);

void input_set_abs_params(struct input_dev *dev, unsigned int axis,
              int min, int max, int fuzz, int flat)
{
    struct input_absinfo *absinfo;

    input_alloc_absinfo(dev);
    if (!dev->absinfo)
        return;

    absinfo = &dev->absinfo[axis];
    absinfo->minimum = min;
    absinfo->maximum = max;
    absinfo->fuzz = fuzz;
    absinfo->flat = flat;

    __set_bit(EV_ABS, dev->evbit);
    __set_bit(axis, dev->absbit);
}
EXPORT_SYMBOL(input_set_abs_params);


/**
 * input_grab_device - grabs device for exclusive use
 * @handle: input handle that wants to own the device
 *
 * When a device is grabbed by an input handle all events generated by
 * the device are delivered only to this handle. Also events injected
 * by other input handles are ignored while device is grabbed.
 */
//得到某个设备做排他使用,即如果某个handler得到了某个设备,那么这个设备产生的所有事件将只发送给这一个handler
int input_grab_device(struct input_handle *handle)
{
    struct input_dev *dev = handle->dev;
    int retval;

    retval = mutex_lock_interruptible(&dev->mutex);
    if (retval)
        return retval;

    if (dev->grab) {
        retval = -EBUSY;
        goto out;
    }

    rcu_assign_pointer(dev->grab, handle);

 out:
    mutex_unlock(&dev->mutex);
    return retval;
}
EXPORT_SYMBOL(input_grab_device);

//释放独占设备
static void __input_release_device(struct input_handle *handle)
{
    struct input_dev *dev = handle->dev;
    struct input_handle *grabber;

    grabber = rcu_dereference_protected(dev->grab,
                        lockdep_is_held(&dev->mutex));
    if (grabber == handle) {
        rcu_assign_pointer(dev->grab, NULL);
        /* Make sure input_pass_event() notices that grab is gone */
        synchronize_rcu();

        list_for_each_entry(handle, &dev->h_list, d_node)
            if (handle->open && handle->handler->start)
                handle->handler->start(handle);
    }
}

/**
 * input_release_device - release previously grabbed device
 * @handle: input handle that owns the device
 *
 * Releases previously grabbed device so that other input handles can
 * start receiving input events. Upon release all handlers attached
 * to the device have their start() method called so they have a change
 * to synchronize device state with the rest of the system.
 */
void input_release_device(struct input_handle *handle)
{
    struct input_dev *dev = handle->dev;

    mutex_lock(&dev->mutex);
    __input_release_device(handle);
    mutex_unlock(&dev->mutex);
}
EXPORT_SYMBOL(input_release_device);

/**
 * input_open_device - open input device
 * @handle: handle through which device is being accessed
 *
 * This function should be called by input handlers when they
 * want to start receive events from given input device.
 */
int input_open_device(struct input_handle *handle)
{
    //得到传入handle的dev
    struct input_dev *dev = handle->dev;
    int retval;

    retval = mutex_lock_interruptible(&dev->mutex);
    if (retval)
        return retval;

    if (dev->going_away) {
        retval = -ENODEV;
        goto out;
    }

    handle->open++;

    //调用对应dev->open打开设备,
    if (!dev->users++ && dev->open)
        retval = dev->open(dev);

    if (retval) {
        dev->users--;
        if (!--handle->open) {
            /*
             * Make sure we are not delivering any more events
             * through this handle
             */
            synchronize_rcu();
        }
    }

 out:
    mutex_unlock(&dev->mutex);
    return retval;
}
EXPORT_SYMBOL(input_open_device);

//就是调用对应的flush函数
int input_flush_device(struct input_handle *handle, struct file *file)
{
    struct input_dev *dev = handle->dev;
    int retval;

    retval = mutex_lock_interruptible(&dev->mutex);
    if (retval)
        return retval;

    if (dev->flush)
        retval = dev->flush(dev, file);

    mutex_unlock(&dev->mutex);
    return retval;
}
EXPORT_SYMBOL(input_flush_device);

/**
 * input_close_device - close input device
 * @handle: handle through which device is being accessed
 *
 * This function should be called by input handlers when they
 * want to stop receive events from given input device.
 */
void input_close_device(struct input_handle *handle)
{
    struct input_dev *dev = handle->dev;

    mutex_lock(&dev->mutex);

    __input_release_device(handle);

    if (!--dev->users && dev->close)
        dev->close(dev);

    if (!--handle->open) {
        /*
         * synchronize_rcu() makes sure that input_pass_event()
         * completed and that no more input events are delivered
         * through this handle
         */
        synchronize_rcu();
    }

    mutex_unlock(&dev->mutex);
}
EXPORT_SYMBOL(input_close_device);

/*
 * Simulate keyup events for all keys that are marked as pressed.
 * The function must be called with dev->event_lock held.
 */
//模拟一个释放按键的动作,比如handler要断开与设备的联系,但设备正在按键按下期间,那么可能导致驱动 “stuck"
static void input_dev_release_keys(struct input_dev *dev)
{
    bool need_sync = false;
    int code;

    if (is_event_supported(EV_KEY, dev->evbit, EV_MAX)) {
        for_each_set_bit(code, dev->key, KEY_CNT) {
            input_pass_event(dev, EV_KEY, code, 0);
            need_sync = true;
        }

        if (need_sync)
            input_pass_event(dev, EV_SYN, SYN_REPORT, 1);

        memset(dev->key, 0, sizeof(dev->key));
    }
}

/*
 * Prepare device for unregistering
 */
static void input_disconnect_device(struct input_dev *dev)
{
    struct input_handle *handle;

    /*
     * Mark device as going away. Note that we take dev->mutex here
     * not to protect access to dev->going_away but rather to ensure
     * that there are no threads in the middle of input_open_device()
     */
    mutex_lock(&dev->mutex);
    dev->going_away = true;
    mutex_unlock(&dev->mutex);

    spin_lock_irq(&dev->event_lock);

    /*
     * Simulate keyup events for all pressed keys so that handlers
     * are not left with "stuck" keys. The driver may continue
     * generate events even after we done here but they will not
     * reach any handlers.
     */
    input_dev_release_keys(dev);

    list_for_each_entry(handle, &dev->h_list, d_node)
        handle->open = 0;

    spin_unlock_irq(&dev->event_lock);
}

/**
 * input_scancode_to_scalar() - converts scancode in &struct input_keymap_entry
 * @ke: keymap entry containing scancode to be converted.
 * @scancode: pointer to the location where converted scancode should
 *  be stored.
 *
 * This function is used to convert scancode stored in &struct keymap_entry
 * into scalar form understood by legacy keymap handling methods. These
 * methods expect scancodes to be represented as 'unsigned int'.
 */
//不同数据长度之间的转化
//如设备驱动层用的是8位长度,但handler层使用的32位长度,那么就需要转换
int input_scancode_to_scalar(const struct input_keymap_entry *ke,
                 unsigned int *scancode)
{
    switch (ke->len) {
    case 1:
        *scancode = *((u8 *)ke->scancode);
        break;

    case 2:
        *scancode = *((u16 *)ke->scancode);
        break;

    case 4:
        *scancode = *((u32 *)ke->scancode);
        break;

    default:
        return -EINVAL;
    }

    return 0;
}
EXPORT_SYMBOL(input_scancode_to_scalar);

/*
 * Those routines handle the default case where no [gs]etkeycode() is
 * defined. In this case, an array indexed by the scancode is used.
 */

static unsigned int input_fetch_keycode(struct input_dev *dev,
                    unsigned int index)
{
    switch (dev->keycodesize) {
    case 1:
        return ((u8 *)dev->keycode)[index];

    case 2:
        return ((u16 *)dev->keycode)[index];

    default:
        return ((u32 *)dev->keycode)[index];
    }
}

static int input_default_getkeycode(struct input_dev *dev,
                    struct input_keymap_entry *ke)
{
    unsigned int index;
    int error;

    if (!dev->keycodesize)
        return -EINVAL;

    if (ke->flags & INPUT_KEYMAP_BY_INDEX)
        index = ke->index;
    else {
        error = input_scancode_to_scalar(ke, &index);
        if (error)
            return error;
    }

    if (index >= dev->keycodemax)
        return -EINVAL;

    ke->keycode = input_fetch_keycode(dev, index);
    ke->index = index;
    ke->len = sizeof(index);
    memcpy(ke->scancode, &index, sizeof(index));

    return 0;
}

static int input_default_setkeycode(struct input_dev *dev,
                    const struct input_keymap_entry *ke,
                    unsigned int *old_keycode)
{
    unsigned int index;
    int error;
    int i;

    if (!dev->keycodesize)
        return -EINVAL;

    if (ke->flags & INPUT_KEYMAP_BY_INDEX) {
        index = ke->index;
    } else {
        error = input_scancode_to_scalar(ke, &index);
        if (error)
            return error;
    }

    if (index >= dev->keycodemax)
        return -EINVAL;

    if (dev->keycodesize < sizeof(ke->keycode) &&
            (ke->keycode >> (dev->keycodesize * 8)))
        return -EINVAL;

    switch (dev->keycodesize) {
        case 1: {
            u8 *k = (u8 *)dev->keycode;
            *old_keycode = k[index];
            k[index] = ke->keycode;
            break;
        }
        case 2: {
            u16 *k = (u16 *)dev->keycode;
            *old_keycode = k[index];
            k[index] = ke->keycode;
            break;
        }
        default: {
            u32 *k = (u32 *)dev->keycode;
            *old_keycode = k[index];
            k[index] = ke->keycode;
            break;
        }
    }

    __clear_bit(*old_keycode, dev->keybit);
    __set_bit(ke->keycode, dev->keybit);

    for (i = 0; i < dev->keycodemax; i++) {
        if (input_fetch_keycode(dev, i) == *old_keycode) {
            __set_bit(*old_keycode, dev->keybit);
            break; /* Setting the bit twice is useless, so break */
        }
    }

    return 0;
}

/**
 * input_get_keycode - retrieve keycode currently mapped to a given scancode
 * @dev: input device which keymap is being queried
 * @ke: keymap entry
 *
 * This function should be called by anyone interested in retrieving current
 * keymap. Presently evdev handlers use it.
 */
int input_get_keycode(struct input_dev *dev, struct input_keymap_entry *ke)
{
    unsigned long flags;
    int retval;

    spin_lock_irqsave(&dev->event_lock, flags);
    retval = dev->getkeycode(dev, ke);
    spin_unlock_irqrestore(&dev->event_lock, flags);

    return retval;
}
EXPORT_SYMBOL(input_get_keycode);

/**
 * input_set_keycode - attribute a keycode to a given scancode
 * @dev: input device which keymap is being updated
 * @ke: new keymap entry
 *
 * This function should be called by anyone needing to update current
 * keymap. Presently keyboard and evdev handlers use it.
 */
int input_set_keycode(struct input_dev *dev,
              const struct input_keymap_entry *ke)
{
    unsigned long flags;
    unsigned int old_keycode;
    int retval;

    if (ke->keycode > KEY_MAX)
        return -EINVAL;

    spin_lock_irqsave(&dev->event_lock, flags);

    retval = dev->setkeycode(dev, ke, &old_keycode);
    if (retval)
        goto out;

    /* Make sure KEY_RESERVED did not get enabled. */
    __clear_bit(KEY_RESERVED, dev->keybit);

    /*
     * Simulate keyup event if keycode is not present
     * in the keymap anymore
     */
    if (test_bit(EV_KEY, dev->evbit) &&
        !is_event_supported(old_keycode, dev->keybit, KEY_MAX) &&
        __test_and_clear_bit(old_keycode, dev->key)) {
        struct input_value vals[] =  {
            { EV_KEY, old_keycode, 0 },
            input_value_sync
        };

        input_pass_values(dev, vals, ARRAY_SIZE(vals));
    }

 out:
    spin_unlock_irqrestore(&dev->event_lock, flags);

    return retval;
}
EXPORT_SYMBOL(input_set_keycode);

//参数dev为设备驱动层的属性
//input_device_id为handler的属性
bool input_match_device_id(const struct input_dev *dev,
               const struct input_device_id *id)
{
    //先判断flag中是否设置了某一属性,如依据BUS VENDOR进行对比
    if (id->flags & INPUT_DEVICE_ID_MATCH_BUS)
        if (id->bustype != dev->id.bustype)
            return false;

    if (id->flags & INPUT_DEVICE_ID_MATCH_VENDOR)
        if (id->vendor != dev->id.vendor)
            return false;

    if (id->flags & INPUT_DEVICE_ID_MATCH_PRODUCT)
        if (id->product != dev->id.product)
            return false;

    if (id->flags & INPUT_DEVICE_ID_MATCH_VERSION)
        if (id->version != dev->id.version)
            return false;

    //确认input_device中设置的事件是否是handler能处理的子集
    if (!bitmap_subset(id->evbit, dev->evbit, EV_MAX) ||
        !bitmap_subset(id->keybit, dev->keybit, KEY_MAX) ||
        !bitmap_subset(id->relbit, dev->relbit, REL_MAX) ||
        !bitmap_subset(id->absbit, dev->absbit, ABS_MAX) ||
        !bitmap_subset(id->mscbit, dev->mscbit, MSC_MAX) ||
        !bitmap_subset(id->ledbit, dev->ledbit, LED_MAX) ||
        !bitmap_subset(id->sndbit, dev->sndbit, SND_MAX) ||
        !bitmap_subset(id->ffbit, dev->ffbit, FF_MAX) ||
        !bitmap_subset(id->swbit, dev->swbit, SW_MAX) ||
        !bitmap_subset(id->propbit, dev->propbit, INPUT_PROP_MAX)) {
        return false;
    }

    return true;
}
EXPORT_SYMBOL(input_match_device_id);

static const struct input_device_id *input_match_device(struct input_handler *handler,
                            struct input_dev *dev)
{
    const struct input_device_id *id;

    //依次将设备的与handler的Idtable进行对比
    for (id = handler->id_table; id->flags || id->driver_info; id++) {
        if (input_match_device_id(dev, id) &&
            (!handler->match || handler->match(handler, dev))) {
            return id;
        }
    }

    return NULL;
}

static int input_attach_handler(struct input_dev *dev, struct input_handler *handler)
{
    const struct input_device_id *id;
    int error;

    id = input_match_device(handler, dev);
    if (!id)
        return -ENODEV;

    //对比通过后,通过connect建立联系
    error = handler->connect(handler, dev, id);
    if (error && error != -ENODEV)
        pr_err("failed to attach handler %s to device %s, error: %d\n",
               handler->name, kobject_name(&dev->dev.kobj), error);

    return error;
}

#ifdef CONFIG_COMPAT

static int input_bits_to_string(char *buf, int buf_size,
                unsigned long bits, bool skip_empty)
{
    int len = 0;

    if (in_compat_syscall()) {
        u32 dword = bits >> 32;
        if (dword || !skip_empty)
            len += snprintf(buf, buf_size, "%x ", dword);

        dword = bits & 0xffffffffUL;
        if (dword || !skip_empty || len)
            len += snprintf(buf + len, max(buf_size - len, 0),
                    "%x", dword);
    } else {
        if (bits || !skip_empty)
            len += snprintf(buf, buf_size, "%lx", bits);
    }

    return len;
}

#else /* !CONFIG_COMPAT */

static int input_bits_to_string(char *buf, int buf_size,
                unsigned long bits, bool skip_empty)
{
    return bits || !skip_empty ?
        snprintf(buf, buf_size, "%lx", bits) : 0;
}

#endif

#ifdef CONFIG_PROC_FS

static struct proc_dir_entry *proc_bus_input_dir;
static DECLARE_WAIT_QUEUE_HEAD(input_devices_poll_wait);
static int input_devices_state;

static inline void input_wakeup_procfs_readers(void)
{
    input_devices_state++;
    wake_up(&input_devices_poll_wait);
}

static unsigned int input_proc_devices_poll(struct file *file, poll_table *wait)
{
    poll_wait(file, &input_devices_poll_wait, wait);
    if (file->f_version != input_devices_state) {
        file->f_version = input_devices_state;
        return POLLIN | POLLRDNORM;
    }

    return 0;
}

union input_seq_state {
    struct {
        unsigned short pos;
        bool mutex_acquired;
    };
    void *p;
};

static void *input_devices_seq_start(struct seq_file *seq, loff_t *pos)
{
    union input_seq_state *state = (union input_seq_state *)&seq->private;
    int error;

    /* We need to fit into seq->private pointer */
    BUILD_BUG_ON(sizeof(union input_seq_state) != sizeof(seq->private));

    error = mutex_lock_interruptible(&input_mutex);
    if (error) {
        state->mutex_acquired = false;
        return ERR_PTR(error);
    }

    state->mutex_acquired = true;

    return seq_list_start(&input_dev_list, *pos);
}

static void *input_devices_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
    return seq_list_next(v, &input_dev_list, pos);
}

static void input_seq_stop(struct seq_file *seq, void *v)
{
    union input_seq_state *state = (union input_seq_state *)&seq->private;

    if (state->mutex_acquired)
        mutex_unlock(&input_mutex);
}

static void input_seq_print_bitmap(struct seq_file *seq, const char *name,
                   unsigned long *bitmap, int max)
{
    int i;
    bool skip_empty = true;
    char buf[18];

    seq_printf(seq, "B: %s=", name);

    for (i = BITS_TO_LONGS(max) - 1; i >= 0; i--) {
        if (input_bits_to_string(buf, sizeof(buf),
                     bitmap[i], skip_empty)) {
            skip_empty = false;
            seq_printf(seq, "%s%s", buf, i > 0 ? " " : "");
        }
    }

    /*
     * If no output was produced print a single 0.
     */
    if (skip_empty)
        seq_putc(seq, '0');

    seq_putc(seq, '\n');
}

static int input_devices_seq_show(struct seq_file *seq, void *v)
{
    struct input_dev *dev = container_of(v, struct input_dev, node);
    const char *path = kobject_get_path(&dev->dev.kobj, GFP_KERNEL);
    struct input_handle *handle;

    seq_printf(seq, "I: Bus=%04x Vendor=%04x Product=%04x Version=%04x\n",
           dev->id.bustype, dev->id.vendor, dev->id.product, dev->id.version);

    seq_printf(seq, "N: Name=\"%s\"\n", dev->name ? dev->name : "");
    seq_printf(seq, "P: Phys=%s\n", dev->phys ? dev->phys : "");
    seq_printf(seq, "S: Sysfs=%s\n", path ? path : "");
    seq_printf(seq, "U: Uniq=%s\n", dev->uniq ? dev->uniq : "");
    seq_puts(seq, "H: Handlers=");

    list_for_each_entry(handle, &dev->h_list, d_node)
        seq_printf(seq, "%s ", handle->name);
    seq_putc(seq, '\n');

    input_seq_print_bitmap(seq, "PROP", dev->propbit, INPUT_PROP_MAX);

    input_seq_print_bitmap(seq, "EV", dev->evbit, EV_MAX);
    if (test_bit(EV_KEY, dev->evbit))
        input_seq_print_bitmap(seq, "KEY", dev->keybit, KEY_MAX);
    if (test_bit(EV_REL, dev->evbit))
        input_seq_print_bitmap(seq, "REL", dev->relbit, REL_MAX);
    if (test_bit(EV_ABS, dev->evbit))
        input_seq_print_bitmap(seq, "ABS", dev->absbit, ABS_MAX);
    if (test_bit(EV_MSC, dev->evbit))
        input_seq_print_bitmap(seq, "MSC", dev->mscbit, MSC_MAX);
    if (test_bit(EV_LED, dev->evbit))
        input_seq_print_bitmap(seq, "LED", dev->ledbit, LED_MAX);
    if (test_bit(EV_SND, dev->evbit))
        input_seq_print_bitmap(seq, "SND", dev->sndbit, SND_MAX);
    if (test_bit(EV_FF, dev->evbit))
        input_seq_print_bitmap(seq, "FF", dev->ffbit, FF_MAX);
    if (test_bit(EV_SW, dev->evbit))
        input_seq_print_bitmap(seq, "SW", dev->swbit, SW_MAX);

    seq_putc(seq, '\n');

    kfree(path);
    return 0;
}

static const struct seq_operations input_devices_seq_ops = {
    .start  = input_devices_seq_start,
    .next   = input_devices_seq_next,
    .stop   = input_seq_stop,
    .show   = input_devices_seq_show,
};

static int input_proc_devices_open(struct inode *inode, struct file *file)
{
    return seq_open(file, &input_devices_seq_ops);
}

static const struct file_operations input_devices_fileops = {
    .owner      = THIS_MODULE,
    .open       = input_proc_devices_open,
    .poll       = input_proc_devices_poll,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = seq_release,
};

static void *input_handlers_seq_start(struct seq_file *seq, loff_t *pos)
{
    union input_seq_state *state = (union input_seq_state *)&seq->private;
    int error;

    /* We need to fit into seq->private pointer */
    BUILD_BUG_ON(sizeof(union input_seq_state) != sizeof(seq->private));

    error = mutex_lock_interruptible(&input_mutex);
    if (error) {
        state->mutex_acquired = false;
        return ERR_PTR(error);
    }

    state->mutex_acquired = true;
    state->pos = *pos;

    return seq_list_start(&input_handler_list, *pos);
}

static void *input_handlers_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
    union input_seq_state *state = (union input_seq_state *)&seq->private;

    state->pos = *pos + 1;
    return seq_list_next(v, &input_handler_list, pos);
}

static int input_handlers_seq_show(struct seq_file *seq, void *v)
{
    struct input_handler *handler = container_of(v, struct input_handler, node);
    union input_seq_state *state = (union input_seq_state *)&seq->private;

    seq_printf(seq, "N: Number=%u Name=%s", state->pos, handler->name);
    if (handler->filter)
        seq_puts(seq, " (filter)");
    if (handler->legacy_minors)
        seq_printf(seq, " Minor=%d", handler->minor);
    seq_putc(seq, '\n');

    return 0;
}

static const struct seq_operations input_handlers_seq_ops = {
    .start  = input_handlers_seq_start,
    .next   = input_handlers_seq_next,
    .stop   = input_seq_stop,
    .show   = input_handlers_seq_show,
};

static int input_proc_handlers_open(struct inode *inode, struct file *file)
{
    return seq_open(file, &input_handlers_seq_ops);
}

static const struct file_operations input_handlers_fileops = {
    .owner      = THIS_MODULE,
    .open       = input_proc_handlers_open,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = seq_release,
};

static int __init input_proc_init(void)
{
    struct proc_dir_entry *entry;

    proc_bus_input_dir = proc_mkdir("bus/input", NULL);
    if (!proc_bus_input_dir)
        return -ENOMEM;

    entry = proc_create("devices", 0, proc_bus_input_dir,
                &input_devices_fileops);
    if (!entry)
        goto fail1;

    entry = proc_create("handlers", 0, proc_bus_input_dir,
                &input_handlers_fileops);
    if (!entry)
        goto fail2;

    return 0;

 fail2: remove_proc_entry("devices", proc_bus_input_dir);
 fail1: remove_proc_entry("bus/input", NULL);
    return -ENOMEM;
}

static void input_proc_exit(void)
{
    remove_proc_entry("devices", proc_bus_input_dir);
    remove_proc_entry("handlers", proc_bus_input_dir);
    remove_proc_entry("bus/input", NULL);
}

#else /* !CONFIG_PROC_FS */
static inline void input_wakeup_procfs_readers(void) { }
static inline int input_proc_init(void) { return 0; }
static inline void input_proc_exit(void) { }
#endif

#define INPUT_DEV_STRING_ATTR_SHOW(name)                \
static ssize_t input_dev_show_##name(struct device *dev,        \
                     struct device_attribute *attr, \
                     char *buf)             \
{                                   \
    struct input_dev *input_dev = to_input_dev(dev);        \
                                    \
    return scnprintf(buf, PAGE_SIZE, "%s\n",            \
             input_dev->name ? input_dev->name : "");   \
}                                   \
static DEVICE_ATTR(name, S_IRUGO, input_dev_show_##name, NULL)

INPUT_DEV_STRING_ATTR_SHOW(name);
INPUT_DEV_STRING_ATTR_SHOW(phys);
INPUT_DEV_STRING_ATTR_SHOW(uniq);

static int input_print_modalias_bits(char *buf, int size,
                     char name, unsigned long *bm,
                     unsigned int min_bit, unsigned int max_bit)
{
    int len = 0, i;

    len += snprintf(buf, max(size, 0), "%c", name);
    for (i = min_bit; i < max_bit; i++)
        if (bm[BIT_WORD(i)] & BIT_MASK(i))
            len += snprintf(buf + len, max(size - len, 0), "%X,", i);
    return len;
}

static int input_print_modalias(char *buf, int size, struct input_dev *id,
                int add_cr)
{
    int len;

    len = snprintf(buf, max(size, 0),
               "input:b%04Xv%04Xp%04Xe%04X-",
               id->id.bustype, id->id.vendor,
               id->id.product, id->id.version);

    len += input_print_modalias_bits(buf + len, size - len,
                'e', id->evbit, 0, EV_MAX);
    len += input_print_modalias_bits(buf + len, size - len,
                'k', id->keybit, KEY_MIN_INTERESTING, KEY_MAX);
    len += input_print_modalias_bits(buf + len, size - len,
                'r', id->relbit, 0, REL_MAX);
    len += input_print_modalias_bits(buf + len, size - len,
                'a', id->absbit, 0, ABS_MAX);
    len += input_print_modalias_bits(buf + len, size - len,
                'm', id->mscbit, 0, MSC_MAX);
    len += input_print_modalias_bits(buf + len, size - len,
                'l', id->ledbit, 0, LED_MAX);
    len += input_print_modalias_bits(buf + len, size - len,
                's', id->sndbit, 0, SND_MAX);
    len += input_print_modalias_bits(buf + len, size - len,
                'f', id->ffbit, 0, FF_MAX);
    len += input_print_modalias_bits(buf + len, size - len,
                'w', id->swbit, 0, SW_MAX);

    if (add_cr)
        len += snprintf(buf + len, max(size - len, 0), "\n");

    return len;
}

static ssize_t input_dev_show_modalias(struct device *dev,
                       struct device_attribute *attr,
                       char *buf)
{
    struct input_dev *id = to_input_dev(dev);
    ssize_t len;

    len = input_print_modalias(buf, PAGE_SIZE, id, 1);

    return min_t(int, len, PAGE_SIZE);
}
static DEVICE_ATTR(modalias, S_IRUGO, input_dev_show_modalias, NULL);

static int input_print_bitmap(char *buf, int buf_size, unsigned long *bitmap,
                  int max, int add_cr);

static ssize_t input_dev_show_properties(struct device *dev,
                     struct device_attribute *attr,
                     char *buf)
{
    struct input_dev *input_dev = to_input_dev(dev);
    int len = input_print_bitmap(buf, PAGE_SIZE, input_dev->propbit,
                     INPUT_PROP_MAX, true);
    return min_t(int, len, PAGE_SIZE);
}
static DEVICE_ATTR(properties, S_IRUGO, input_dev_show_properties, NULL);

static struct attribute *input_dev_attrs[] = {
    &dev_attr_name.attr,
    &dev_attr_phys.attr,
    &dev_attr_uniq.attr,
    &dev_attr_modalias.attr,
    &dev_attr_properties.attr,
    NULL
};

static const struct attribute_group input_dev_attr_group = {
    .attrs  = input_dev_attrs,
};

#define INPUT_DEV_ID_ATTR(name)                     \
static ssize_t input_dev_show_id_##name(struct device *dev,     \
                    struct device_attribute *attr,  \
                    char *buf)          \
{                                   \
    struct input_dev *input_dev = to_input_dev(dev);        \
    return scnprintf(buf, PAGE_SIZE, "%04x\n", input_dev->id.name); \
}                                   \
static DEVICE_ATTR(name, S_IRUGO, input_dev_show_id_##name, NULL)

INPUT_DEV_ID_ATTR(bustype);
INPUT_DEV_ID_ATTR(vendor);
INPUT_DEV_ID_ATTR(product);
INPUT_DEV_ID_ATTR(version);

static struct attribute *input_dev_id_attrs[] = {
    &dev_attr_bustype.attr,
    &dev_attr_vendor.attr,
    &dev_attr_product.attr,
    &dev_attr_version.attr,
    NULL
};

static const struct attribute_group input_dev_id_attr_group = {
    .name   = "id",
    .attrs  = input_dev_id_attrs,
};

static int input_print_bitmap(char *buf, int buf_size, unsigned long *bitmap,
                  int max, int add_cr)
{
    int i;
    int len = 0;
    bool skip_empty = true;

    for (i = BITS_TO_LONGS(max) - 1; i >= 0; i--) {
        len += input_bits_to_string(buf + len, max(buf_size - len, 0),
                        bitmap[i], skip_empty);
        if (len) {
            skip_empty = false;
            if (i > 0)
                len += snprintf(buf + len, max(buf_size - len, 0), " ");
        }
    }

    /*
     * If no output was produced print a single 0.
     */
    if (len == 0)
        len = snprintf(buf, buf_size, "%d", 0);

    if (add_cr)
        len += snprintf(buf + len, max(buf_size - len, 0), "\n");

    return len;
}

#define INPUT_DEV_CAP_ATTR(ev, bm)                  \
static ssize_t input_dev_show_cap_##bm(struct device *dev,      \
                       struct device_attribute *attr,   \
                       char *buf)           \
{                                   \
    struct input_dev *input_dev = to_input_dev(dev);        \
    int len = input_print_bitmap(buf, PAGE_SIZE,            \
                     input_dev->bm##bit, ev##_MAX,  \
                     true);             \
    return min_t(int, len, PAGE_SIZE);              \
}                                   \
static DEVICE_ATTR(bm, S_IRUGO, input_dev_show_cap_##bm, NULL)

INPUT_DEV_CAP_ATTR(EV, ev);
INPUT_DEV_CAP_ATTR(KEY, key);
INPUT_DEV_CAP_ATTR(REL, rel);
INPUT_DEV_CAP_ATTR(ABS, abs);
INPUT_DEV_CAP_ATTR(MSC, msc);
INPUT_DEV_CAP_ATTR(LED, led);
INPUT_DEV_CAP_ATTR(SND, snd);
INPUT_DEV_CAP_ATTR(FF, ff);
INPUT_DEV_CAP_ATTR(SW, sw);

static struct attribute *input_dev_caps_attrs[] = {
    &dev_attr_ev.attr,
    &dev_attr_key.attr,
    &dev_attr_rel.attr,
    &dev_attr_abs.attr,
    &dev_attr_msc.attr,
    &dev_attr_led.attr,
    &dev_attr_snd.attr,
    &dev_attr_ff.attr,
    &dev_attr_sw.attr,
    NULL
};

static const struct attribute_group input_dev_caps_attr_group = {
    .name   = "capabilities",
    .attrs  = input_dev_caps_attrs,
};

static const struct attribute_group *input_dev_attr_groups[] = {
    &input_dev_attr_group,
    &input_dev_id_attr_group,
    &input_dev_caps_attr_group,
    NULL
};

static void input_dev_release(struct device *device)
{
    struct input_dev *dev = to_input_dev(device);

    input_ff_destroy(dev);
    input_mt_destroy_slots(dev);
    kfree(dev->absinfo);
    kfree(dev->vals);
    kfree(dev);

    module_put(THIS_MODULE);
}

/*
 * Input uevent interface - loading event handlers based on
 * device bitfields.
 */
static int input_add_uevent_bm_var(struct kobj_uevent_env *env,
                   const char *name, unsigned long *bitmap, int max)
{
    int len;

    if (add_uevent_var(env, "%s", name))
        return -ENOMEM;

    len = input_print_bitmap(&env->buf[env->buflen - 1],
                 sizeof(env->buf) - env->buflen,
                 bitmap, max, false);
    if (len >= (sizeof(env->buf) - env->buflen))
        return -ENOMEM;

    env->buflen += len;
    return 0;
}

static int input_add_uevent_modalias_var(struct kobj_uevent_env *env,
                     struct input_dev *dev)
{
    int len;

    if (add_uevent_var(env, "MODALIAS="))
        return -ENOMEM;

    len = input_print_modalias(&env->buf[env->buflen - 1],
                   sizeof(env->buf) - env->buflen,
                   dev, 0);
    if (len >= (sizeof(env->buf) - env->buflen))
        return -ENOMEM;

    env->buflen += len;
    return 0;
}

#define INPUT_ADD_HOTPLUG_VAR(fmt, val...)              \
    do {                                \
        int err = add_uevent_var(env, fmt, val);        \
        if (err)                        \
            return err;                 \
    } while (0)

#define INPUT_ADD_HOTPLUG_BM_VAR(name, bm, max)             \
    do {                                \
        int err = input_add_uevent_bm_var(env, name, bm, max);  \
        if (err)                        \
            return err;                 \
    } while (0)

#define INPUT_ADD_HOTPLUG_MODALIAS_VAR(dev)             \
    do {                                \
        int err = input_add_uevent_modalias_var(env, dev);  \
        if (err)                        \
            return err;                 \
    } while (0)

static int input_dev_uevent(struct device *device, struct kobj_uevent_env *env)
{
    struct input_dev *dev = to_input_dev(device);

    INPUT_ADD_HOTPLUG_VAR("PRODUCT=%x/%x/%x/%x",
                dev->id.bustype, dev->id.vendor,
                dev->id.product, dev->id.version);
    if (dev->name)
        INPUT_ADD_HOTPLUG_VAR("NAME=\"%s\"", dev->name);
    if (dev->phys)
        INPUT_ADD_HOTPLUG_VAR("PHYS=\"%s\"", dev->phys);
    if (dev->uniq)
        INPUT_ADD_HOTPLUG_VAR("UNIQ=\"%s\"", dev->uniq);

    INPUT_ADD_HOTPLUG_BM_VAR("PROP=", dev->propbit, INPUT_PROP_MAX);

    INPUT_ADD_HOTPLUG_BM_VAR("EV=", dev->evbit, EV_MAX);
    if (test_bit(EV_KEY, dev->evbit))
        INPUT_ADD_HOTPLUG_BM_VAR("KEY=", dev->keybit, KEY_MAX);
    if (test_bit(EV_REL, dev->evbit))
        INPUT_ADD_HOTPLUG_BM_VAR("REL=", dev->relbit, REL_MAX);
    if (test_bit(EV_ABS, dev->evbit))
        INPUT_ADD_HOTPLUG_BM_VAR("ABS=", dev->absbit, ABS_MAX);
    if (test_bit(EV_MSC, dev->evbit))
        INPUT_ADD_HOTPLUG_BM_VAR("MSC=", dev->mscbit, MSC_MAX);
    if (test_bit(EV_LED, dev->evbit))
        INPUT_ADD_HOTPLUG_BM_VAR("LED=", dev->ledbit, LED_MAX);
    if (test_bit(EV_SND, dev->evbit))
        INPUT_ADD_HOTPLUG_BM_VAR("SND=", dev->sndbit, SND_MAX);
    if (test_bit(EV_FF, dev->evbit))
        INPUT_ADD_HOTPLUG_BM_VAR("FF=", dev->ffbit, FF_MAX);
    if (test_bit(EV_SW, dev->evbit))
        INPUT_ADD_HOTPLUG_BM_VAR("SW=", dev->swbit, SW_MAX);

    INPUT_ADD_HOTPLUG_MODALIAS_VAR(dev);

    return 0;
}

#define INPUT_DO_TOGGLE(dev, type, bits, on)                \
    do {                                \
        int i;                          \
        bool active;                        \
                                    \
        if (!test_bit(EV_##type, dev->evbit))           \
            break;                      \
                                    \
        for_each_set_bit(i, dev->bits##bit, type##_CNT) {   \
            active = test_bit(i, dev->bits);        \
            if (!active && !on)             \
                continue;               \
                                    \
            dev->event(dev, EV_##type, i, on ? active : 0); \
        }                           \
    } while (0)

static void input_dev_toggle(struct input_dev *dev, bool activate)
{
    if (!dev->event)
        return;

    INPUT_DO_TOGGLE(dev, LED, led, activate);
    INPUT_DO_TOGGLE(dev, SND, snd, activate);

    if (activate && test_bit(EV_REP, dev->evbit)) {
        dev->event(dev, EV_REP, REP_PERIOD, dev->rep[REP_PERIOD]);
        dev->event(dev, EV_REP, REP_DELAY, dev->rep[REP_DELAY]);
    }
}

/**
 * input_reset_device() - reset/restore the state of input device
 * @dev: input device whose state needs to be reset
 *
 * This function tries to reset the state of an opened input device and
 * bring internal state and state if the hardware in sync with each other.
 * We mark all keys as released, restore LED state, repeat rate, etc.
 */
void input_reset_device(struct input_dev *dev)
{
    unsigned long flags;

    mutex_lock(&dev->mutex);
    spin_lock_irqsave(&dev->event_lock, flags);

    input_dev_toggle(dev, true);
    input_dev_release_keys(dev);

    spin_unlock_irqrestore(&dev->event_lock, flags);
    mutex_unlock(&dev->mutex);
}
EXPORT_SYMBOL(input_reset_device);

#ifdef CONFIG_PM_SLEEP
static int input_dev_suspend(struct device *dev)
{
    struct input_dev *input_dev = to_input_dev(dev);

    spin_lock_irq(&input_dev->event_lock);

    /*
     * Keys that are pressed now are unlikely to be
     * still pressed when we resume.
     */
    input_dev_release_keys(input_dev);

    /* Turn off LEDs and sounds, if any are active. */
    input_dev_toggle(input_dev, false);

    spin_unlock_irq(&input_dev->event_lock);

    return 0;
}

static int input_dev_resume(struct device *dev)
{
    struct input_dev *input_dev = to_input_dev(dev);

    spin_lock_irq(&input_dev->event_lock);

    /* Restore state of LEDs and sounds, if any were active. */
    input_dev_toggle(input_dev, true);

    spin_unlock_irq(&input_dev->event_lock);

    return 0;
}

static int input_dev_freeze(struct device *dev)
{
    struct input_dev *input_dev = to_input_dev(dev);

    spin_lock_irq(&input_dev->event_lock);

    /*
     * Keys that are pressed now are unlikely to be
     * still pressed when we resume.
     */
    input_dev_release_keys(input_dev);

    spin_unlock_irq(&input_dev->event_lock);

    return 0;
}

static int input_dev_poweroff(struct device *dev)
{
    struct input_dev *input_dev = to_input_dev(dev);

    spin_lock_irq(&input_dev->event_lock);

    /* Turn off LEDs and sounds, if any are active. */
    input_dev_toggle(input_dev, false);

    spin_unlock_irq(&input_dev->event_lock);

    return 0;
}

static const struct dev_pm_ops input_dev_pm_ops = {
    .suspend    = input_dev_suspend,
    .resume     = input_dev_resume,
    .freeze     = input_dev_freeze,
    .poweroff   = input_dev_poweroff,
    .restore    = input_dev_resume,
};
#endif /* CONFIG_PM */

static const struct device_type input_dev_type = {
    .groups     = input_dev_attr_groups,
    .release    = input_dev_release,
    .uevent     = input_dev_uevent,
#ifdef CONFIG_PM_SLEEP
    .pm     = &input_dev_pm_ops,
#endif
};

static char *input_devnode(struct device *dev, umode_t *mode)
{
    return kasprintf(GFP_KERNEL, "input/%s", dev_name(dev));
}

struct class input_class = {
    .name       = "input",
    .devnode    = input_devnode,
};
EXPORT_SYMBOL_GPL(input_class);

/**
 * input_allocate_device - allocate memory for new input device
 *
 * Returns prepared struct input_dev or %NULL.
 *
 * NOTE: Use input_free_device() to free devices that have not been
 * registered; input_unregister_device() should be used for already
 * registered devices.
 */
struct input_dev *input_allocate_device(void)
{
    static atomic_t input_no = ATOMIC_INIT(-1);
    struct input_dev *dev;

    dev = kzalloc(sizeof(*dev), GFP_KERNEL);
    if (dev) {
        dev->dev.type = &input_dev_type;
        dev->dev.class = &input_class;
        device_initialize(&dev->dev);
        mutex_init(&dev->mutex);
        spin_lock_init(&dev->event_lock);
        init_timer(&dev->timer);
        INIT_LIST_HEAD(&dev->h_list);
        INIT_LIST_HEAD(&dev->node);

        dev_set_name(&dev->dev, "input%lu",
                 (unsigned long)atomic_inc_return(&input_no));

        __module_get(THIS_MODULE);
    }

    return dev;
}
EXPORT_SYMBOL(input_allocate_device);

struct input_devres {
    struct input_dev *input;
};

static int devm_input_device_match(struct device *dev, void *res, void *data)
{
    struct input_devres *devres = res;

    return devres->input == data;
}

static void devm_input_device_release(struct device *dev, void *res)
{
    struct input_devres *devres = res;
    struct input_dev *input = devres->input;

    dev_dbg(dev, "%s: dropping reference to %s\n",
        __func__, dev_name(&input->dev));
    input_put_device(input);
}

/**
 * devm_input_allocate_device - allocate managed input device
 * @dev: device owning the input device being created
 *
 * Returns prepared struct input_dev or %NULL.
 *
 * Managed input devices do not need to be explicitly unregistered or
 * freed as it will be done automatically when owner device unbinds from
 * its driver (or binding fails). Once managed input device is allocated,
 * it is ready to be set up and registered in the same fashion as regular
 * input device. There are no special devm_input_device_[un]register()
 * variants, regular ones work with both managed and unmanaged devices,
 * should you need them. In most cases however, managed input device need
 * not be explicitly unregistered or freed.
 *
 * NOTE: the owner device is set up as parent of input device and users
 * should not override it.
 */
struct input_dev *devm_input_allocate_device(struct device *dev)
{
    struct input_dev *input;
    struct input_devres *devres;

    devres = devres_alloc(devm_input_device_release,
                  sizeof(*devres), GFP_KERNEL);
    if (!devres)
        return NULL;

    input = input_allocate_device();
    if (!input) {
        devres_free(devres);
        return NULL;
    }

    input->dev.parent = dev;
    input->devres_managed = true;

    devres->input = input;
    devres_add(dev, devres);

    return input;
}
EXPORT_SYMBOL(devm_input_allocate_device);

/**
 * input_free_device - free memory occupied by input_dev structure
 * @dev: input device to free
 *
 * This function should only be used if input_register_device()
 * was not called yet or if it failed. Once device was registered
 * use input_unregister_device() and memory will be freed once last
 * reference to the device is dropped.
 *
 * Device should be allocated by input_allocate_device().
 *
 * NOTE: If there are references to the input device then memory
 * will not be freed until last reference is dropped.
 */
void input_free_device(struct input_dev *dev)
{
    if (dev) {
        if (dev->devres_managed)
            WARN_ON(devres_destroy(dev->dev.parent,
                        devm_input_device_release,
                        devm_input_device_match,
                        dev));
        input_put_device(dev);
    }
}
EXPORT_SYMBOL(input_free_device);

/**
 * input_set_capability - mark device as capable of a certain event
 * @dev: device that is capable of emitting or accepting event
 * @type: type of the event (EV_KEY, EV_REL, etc...)
 * @code: event code
 *
 * In addition to setting up corresponding bit in appropriate capability
 * bitmap the function also adjusts dev->evbit.
 */
void input_set_capability(struct input_dev *dev, unsigned int type, unsigned int code)
{
    switch (type) {
    case EV_KEY:
        __set_bit(code, dev->keybit);
        break;

    case EV_REL:
        __set_bit(code, dev->relbit);
        break;

    case EV_ABS:
        input_alloc_absinfo(dev);
        if (!dev->absinfo)
            return;

        __set_bit(code, dev->absbit);
        break;

    case EV_MSC:
        __set_bit(code, dev->mscbit);
        break;

    case EV_SW:
        __set_bit(code, dev->swbit);
        break;

    case EV_LED:
        __set_bit(code, dev->ledbit);
        break;

    case EV_SND:
        __set_bit(code, dev->sndbit);
        break;

    case EV_FF:
        __set_bit(code, dev->ffbit);
        break;

    case EV_PWR:
        /* do nothing */
        break;

    default:
        pr_err("input_set_capability: unknown type %u (code %u)\n",
               type, code);
        dump_stack();
        return;
    }

    __set_bit(type, dev->evbit);
}
EXPORT_SYMBOL(input_set_capability);

static unsigned int input_estimate_events_per_packet(struct input_dev *dev)
{
    int mt_slots;
    int i;
    unsigned int events;

    if (dev->mt) {
        mt_slots = dev->mt->num_slots;
    } else if (test_bit(ABS_MT_TRACKING_ID, dev->absbit)) {
        mt_slots = dev->absinfo[ABS_MT_TRACKING_ID].maximum -
               dev->absinfo[ABS_MT_TRACKING_ID].minimum + 1,
        mt_slots = clamp(mt_slots, 2, 32);
    } else if (test_bit(ABS_MT_POSITION_X, dev->absbit)) {
        mt_slots = 2;
    } else {
        mt_slots = 0;
    }

    events = mt_slots + 1; /* count SYN_MT_REPORT and SYN_REPORT */

    if (test_bit(EV_ABS, dev->evbit))
        for_each_set_bit(i, dev->absbit, ABS_CNT)
            events += input_is_mt_axis(i) ? mt_slots : 1;

    if (test_bit(EV_REL, dev->evbit))
        events += bitmap_weight(dev->relbit, REL_CNT);

    /* Make room for KEY and MSC events */
    events += 7;

    return events;
}

#define INPUT_CLEANSE_BITMASK(dev, type, bits)              \
    do {                                \
        if (!test_bit(EV_##type, dev->evbit))           \
            memset(dev->bits##bit, 0,           \
                sizeof(dev->bits##bit));        \
    } while (0)

static void input_cleanse_bitmasks(struct input_dev *dev)
{
    INPUT_CLEANSE_BITMASK(dev, KEY, key);
    INPUT_CLEANSE_BITMASK(dev, REL, rel);
    INPUT_CLEANSE_BITMASK(dev, ABS, abs);
    INPUT_CLEANSE_BITMASK(dev, MSC, msc);
    INPUT_CLEANSE_BITMASK(dev, LED, led);
    INPUT_CLEANSE_BITMASK(dev, SND, snd);
    INPUT_CLEANSE_BITMASK(dev, FF, ff);
    INPUT_CLEANSE_BITMASK(dev, SW, sw);
}

static void __input_unregister_device(struct input_dev *dev)
{
    struct input_handle *handle, *next;

    input_disconnect_device(dev);

    mutex_lock(&input_mutex);

    list_for_each_entry_safe(handle, next, &dev->h_list, d_node)
        handle->handler->disconnect(handle);
    WARN_ON(!list_empty(&dev->h_list));

    del_timer_sync(&dev->timer);
    list_del_init(&dev->node);

    input_wakeup_procfs_readers();

    mutex_unlock(&input_mutex);

    device_del(&dev->dev);
}

static void devm_input_device_unregister(struct device *dev, void *res)
{
    struct input_devres *devres = res;
    struct input_dev *input = devres->input;

    dev_dbg(dev, "%s: unregistering device %s\n",
        __func__, dev_name(&input->dev));
    __input_unregister_device(input);
}

/**
 * input_enable_softrepeat - enable software autorepeat
 * @dev: input device
 * @delay: repeat delay
 * @period: repeat period
 *
 * Enable software autorepeat on the input device.
 */
void input_enable_softrepeat(struct input_dev *dev, int delay, int period)
{
    dev->timer.data = (unsigned long) dev;
    dev->timer.function = input_repeat_key;
    dev->rep[REP_DELAY] = delay;
    dev->rep[REP_PERIOD] = period;
}
EXPORT_SYMBOL(input_enable_softrepeat);

/**
 * input_register_device - register device with input core
 * @dev: device to be registered
 *
 * This function registers device with input core. The device must be
 * allocated with input_allocate_device() and all it's capabilities
 * set up before registering.
 * If function fails the device must be freed with input_free_device().
 * Once device has been successfully registered it can be unregistered
 * with input_unregister_device(); input_free_device() should not be
 * called in this case.
 *
 * Note that this function is also used to register managed input devices
 * (ones allocated with devm_input_allocate_device()). Such managed input
 * devices need not be explicitly unregistered or freed, their tear down
 * is controlled by the devres infrastructure. It is also worth noting
 * that tear down of managed input devices is internally a 2-step process:
 * registered managed input device is first unregistered, but stays in
 * memory and can still handle input_event() calls (although events will
 * not be delivered anywhere). The freeing of managed input device will
 * happen later, when devres stack is unwound to the point where device
 * allocation was made.
 */
int input_register_device(struct input_dev *dev)
{
    struct input_devres *devres = NULL;
    struct input_handler *handler;
    unsigned int packet_size;
    const char *path;
    int error;

    if (test_bit(EV_ABS, dev->evbit) && !dev->absinfo) {
        dev_err(&dev->dev,
            "Absolute device without dev->absinfo, refusing to register\n");
        return -EINVAL;
    }

    if (dev->devres_managed) {
        devres = devres_alloc(devm_input_device_unregister,
                      sizeof(*devres), GFP_KERNEL);
        if (!devres)
            return -ENOMEM;

        devres->input = dev;
    }

    /* Every input device generates EV_SYN/SYN_REPORT events. */
    __set_bit(EV_SYN, dev->evbit);

    /* KEY_RESERVED is not supposed to be transmitted to userspace. */
    __clear_bit(KEY_RESERVED, dev->keybit);

    /* Make sure that bitmasks not mentioned in dev->evbit are clean. */
    input_cleanse_bitmasks(dev);

    packet_size = input_estimate_events_per_packet(dev);
    if (dev->hint_events_per_packet < packet_size)
        dev->hint_events_per_packet = packet_size;

    dev->max_vals = dev->hint_events_per_packet + 2;
    dev->vals = kcalloc(dev->max_vals, sizeof(*dev->vals), GFP_KERNEL);
    if (!dev->vals) {
        error = -ENOMEM;
        goto err_devres_free;
    }

    /*
     * If delay and period are pre-set by the driver, then autorepeating
     * is handled by the driver itself and we don't do it in input.c.
     */
    if (!dev->rep[REP_DELAY] && !dev->rep[REP_PERIOD])
        input_enable_softrepeat(dev, 250, 33);

    if (!dev->getkeycode)
        dev->getkeycode = input_default_getkeycode;

    if (!dev->setkeycode)
        dev->setkeycode = input_default_setkeycode;

    error = device_add(&dev->dev);
    if (error)
        goto err_free_vals;

    path = kobject_get_path(&dev->dev.kobj, GFP_KERNEL);
    pr_info("%s as %s\n",
        dev->name ? dev->name : "Unspecified device",
        path ? path : "N/A");
    kfree(path);

    error = mutex_lock_interruptible(&input_mutex);
    if (error)
        goto err_device_del;

    list_add_tail(&dev->node, &input_dev_list);

    //在此处建立联系
    list_for_each_entry(handler, &input_handler_list, node)
        input_attach_handler(dev, handler);

    input_wakeup_procfs_readers();

    mutex_unlock(&input_mutex);

    if (dev->devres_managed) {
        dev_dbg(dev->dev.parent, "%s: registering %s with devres.\n",
            __func__, dev_name(&dev->dev));
        devres_add(dev->dev.parent, devres);
    }
    return 0;

err_device_del:
    device_del(&dev->dev);
err_free_vals:
    kfree(dev->vals);
    dev->vals = NULL;
err_devres_free:
    devres_free(devres);
    return error;
}
EXPORT_SYMBOL(input_register_device);

/**
 * input_unregister_device - unregister previously registered device
 * @dev: device to be unregistered
 *
 * This function unregisters an input device. Once device is unregistered
 * the caller should not try to access it as it may get freed at any moment.
 */
void input_unregister_device(struct input_dev *dev)
{
    if (dev->devres_managed) {
        WARN_ON(devres_destroy(dev->dev.parent,
                    devm_input_device_unregister,
                    devm_input_device_match,
                    dev));
        __input_unregister_device(dev);
        /*
         * We do not do input_put_device() here because it will be done
         * when 2nd devres fires up.
         */
    } else {
        __input_unregister_device(dev);
        input_put_device(dev);
    }
}
EXPORT_SYMBOL(input_unregister_device);

/**
 * input_register_handler - register a new input handler
 * @handler: handler to be registered
 *
 * This function registers a new input handler (interface) for input
 * devices in the system and attaches it to all input devices that
 * are compatible with the handler.
 */
//在
int input_register_handler(struct input_handler *handler)
{
    struct input_dev *dev;
    int error;

    error = mutex_lock_interruptible(&input_mutex);
    if (error)
        return error;

    INIT_LIST_HEAD(&handler->h_list);

    list_add_tail(&handler->node, &input_handler_list);

    list_for_each_entry(dev, &input_dev_list, node)
        input_attach_handler(dev, handler);

    input_wakeup_procfs_readers();

    mutex_unlock(&input_mutex);
    return 0;
}
EXPORT_SYMBOL(input_register_handler);

/**
 * input_unregister_handler - unregisters an input handler
 * @handler: handler to be unregistered
 *
 * This function disconnects a handler from its input devices and
 * removes it from lists of known handlers.
 */
void input_unregister_handler(struct input_handler *handler)
{
    struct input_handle *handle, *next;

    mutex_lock(&input_mutex);

    list_for_each_entry_safe(handle, next, &handler->h_list, h_node)
        handler->disconnect(handle);
    WARN_ON(!list_empty(&handler->h_list));

    list_del_init(&handler->node);

    input_wakeup_procfs_readers();

    mutex_unlock(&input_mutex);
}
EXPORT_SYMBOL(input_unregister_handler);

/**
 * input_handler_for_each_handle - handle iterator
 * @handler: input handler to iterate
 * @data: data for the callback
 * @fn: function to be called for each handle
 *
 * Iterate over @bus's list of devices, and call @fn for each, passing
 * it @data and stop when @fn returns a non-zero value. The function is
 * using RCU to traverse the list and therefore may be using in atomic
 * contexts. The @fn callback is invoked from RCU critical section and
 * thus must not sleep.
 */
int input_handler_for_each_handle(struct input_handler *handler, void *data,
                  int (*fn)(struct input_handle *, void *))
{
    struct input_handle *handle;
    int retval = 0;

    rcu_read_lock();

    list_for_each_entry_rcu(handle, &handler->h_list, h_node) {
        retval = fn(handle, data);
        if (retval)
            break;
    }

    rcu_read_unlock();

    return retval;
}
EXPORT_SYMBOL(input_handler_for_each_handle);

/**
 * input_register_handle - register a new input handle
 * @handle: handle to register
 *
 * This function puts a new input handle onto device's
 * and handler's lists so that events can flow through
 * it once it is opened using input_open_device().
 *
 * This function is supposed to be called from handler's
 * connect() method.
 */
int input_register_handle(struct input_handle *handle)
{
    struct input_handler *handler = handle->handler;
    struct input_dev *dev = handle->dev;
    int error;

    /*
     * We take dev->mutex here to prevent race with
     * input_release_device().
     */
    error = mutex_lock_interruptible(&dev->mutex);
    if (error)
        return error;

    /*
     * Filters go to the head of the list, normal handlers
     * to the tail.
     */
    if (handler->filter)
        list_add_rcu(&handle->d_node, &dev->h_list);
    else
        list_add_tail_rcu(&handle->d_node, &dev->h_list);

    mutex_unlock(&dev->mutex);

    /*
     * Since we are supposed to be called from ->connect()
     * which is mutually exclusive with ->disconnect()
     * we can't be racing with input_unregister_handle()
     * and so separate lock is not needed here.
     */
    list_add_tail_rcu(&handle->h_node, &handler->h_list);

    if (handler->start)
        handler->start(handle);

    return 0;
}
EXPORT_SYMBOL(input_register_handle);

/**
 * input_unregister_handle - unregister an input handle
 * @handle: handle to unregister
 *
 * This function removes input handle from device's
 * and handler's lists.
 *
 * This function is supposed to be called from handler's
 * disconnect() method.
 */
void input_unregister_handle(struct input_handle *handle)
{
    struct input_dev *dev = handle->dev;

    list_del_rcu(&handle->h_node);

    /*
     * Take dev->mutex to prevent race with input_release_device().
     */
    mutex_lock(&dev->mutex);
    list_del_rcu(&handle->d_node);
    mutex_unlock(&dev->mutex);

    synchronize_rcu();
}
EXPORT_SYMBOL(input_unregister_handle);

/**
 * input_get_new_minor - allocates a new input minor number
 * @legacy_base: beginning or the legacy range to be searched
 * @legacy_num: size of legacy range
 * @allow_dynamic: whether we can also take ID from the dynamic range
 *
 * This function allocates a new device minor for from input major namespace.
 * Caller can request legacy minor by specifying @legacy_base and @legacy_num
 * parameters and whether ID can be allocated from dynamic range if there are
 * no free IDs in legacy range.
 */
int input_get_new_minor(int legacy_base, unsigned int legacy_num,
            bool allow_dynamic)
{
    /*
     * This function should be called from input handler's ->connect()
     * methods, which are serialized with input_mutex, so no additional
     * locking is needed here.
     */
    if (legacy_base >= 0) {
        int minor = ida_simple_get(&input_ida,
                       legacy_base,
                       legacy_base + legacy_num,
                       GFP_KERNEL);
        if (minor >= 0 || !allow_dynamic)
            return minor;
    }

    return ida_simple_get(&input_ida,
                  INPUT_FIRST_DYNAMIC_DEV, INPUT_MAX_CHAR_DEVICES,
                  GFP_KERNEL);
}
EXPORT_SYMBOL(input_get_new_minor);

/**
 * input_free_minor - release previously allocated minor
 * @minor: minor to be released
 *
 * This function releases previously allocated input minor so that it can be
 * reused later.
 */
void input_free_minor(unsigned int minor)
{
    ida_simple_remove(&input_ida, minor);
}
EXPORT_SYMBOL(input_free_minor);

//注册类以及input设备节点
static int __init input_init(void)
{
    int err;

    err = class_register(&input_class);
    if (err) {
        pr_err("unable to register input_dev class\n");
        return err;
    }

    err = input_proc_init();
    if (err)
        goto fail1;

    err = register_chrdev_region(MKDEV(INPUT_MAJOR, 0),
                     INPUT_MAX_CHAR_DEVICES, "input");
    if (err) {
        pr_err("unable to register char major %d", INPUT_MAJOR);
        goto fail2;
    }

    return 0;

 fail2: input_proc_exit();
 fail1: class_unregister(&input_class);
    return err;
}

static void __exit input_exit(void)
{
    input_proc_exit();
    unregister_chrdev_region(MKDEV(INPUT_MAJOR, 0),
                 INPUT_MAX_CHAR_DEVICES);
    class_unregister(&input_class);
}

subsys_initcall(input_init);
module_exit(input_exit);

原文地址 : http://coderdock.com

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