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Linux驱动学习笔记之输入子系统（1）

分类：

2012-03-15 16:38:57

原文地址：Linux驱动学习笔记之输入子系统（1） 作者：jiaweijing

之所以要引入子系统，是为了让程序更标准化。之前的按键程序，虽然最后相对比较完善，但是不是通用的，别人在不熟悉的情况下是不能随心所欲调用的。显然这与实际应用不合.input输入子系统是内核源码自带的，如果按他这种框架来写，写出的程序就可以很方便地被上层调用，而不用过份关注一些其他的问题。

首先，分析一个驱动程序，先从入口函数开始。static int __init input_init（）中有一句err = register_chrdev(INPUT_MAJOR, "input", &input_fops);是用来注册设备的，接下来再看注册设备的信息。
在
static const struct file_operations input_fops = {
    .owner = THIS_MODULE,
    .open = input_open_file,
};
想调用open肯定要进入input_open_file中执行，打开input_open_file 分析见代码中的注释。根据实际情况构造新的new_fops.
err = new_fops->open(inode, file);   // 返回新的fops
应用程序中要读就要执行：
read > ... > file->f_op->read
input_table数组由谁构造
MODULE_DEVICE_TABLE(input, evdev_ids);   // 源自drivers\input\Evdev.c

static struct input_handler evdev_handler = {
    .event =    evdev_event,                   // 事件
    .connect =    evdev_connect,               // 连接
    .disconnect =    evdev_disconnect,         // 断开连接，关联
    .fops =        &evdev_fops,                // fops
    .minor =    EVDEV_MINOR_BASE,              // 次设备号
    .name =        "evdev",                    // 设备名
    .id_table =    evdev_ids,                  // id_table 表示可以支持的设备 如果id_table支持设备则调用connect函数。让input_device(硬件上的）和input_handler(软件上的）建立一个连接。
};

input_register_handler（软件上的）

注册input_handler:
input_register_handler:
input_table[handler->minor >> 5] = handler  // 数组
list_add_tail(&handler->node, &input_handler_list);  // 放入链表

list_for_each_entry(dev, &input_dev_list, node)      // 对于每一个input_dev调用input_attach_handler
    input_attach_handler(dev, handler);              // 根据input_handler中的id_table来判断能否支持这个input_dev
          
注册输入设备
input_register_device
    list_add_tail(&dev->node, &input_dev_list)   // 放入链表
   
    list_for_each_entry(handler, &input_handler_list, node) // 对input_handler_list中的每一个条目都调用input_attach_handler（）;
        input_attach_handler(dev, handler);  // 根据input_handler中的id_table来判断能否支持这个input_dev

   
   
input_attach_handler:

id = input_match_device(handler->id_table, dev);

error = handler->connect(handler, dev, id);

根据注册input_dev或input_handler时，会两两比较input_dev和input_handler
根据input_handler的id_table判断这个input_handler能否支持这个input_dev,如果可以则调用
input_handler的connect函数建立“连接”

怎么建立连接：
1，分配一个input_handle结构体
2，设置
    input_handle.dev = input_dev;
    input_handle.handler = input_handler;
3,注册
    input_handler->h_list = &input_handle
    input_dev->h_list     = &input_handle
   
Evdev.c
evdev_connect()

evdev = kzalloc(sizeof(struct evdev), GFP_KERNEL);    // 分配一个input_handle结构

    // 设置
    evdev->handle.dev = dev;            // 指向input_dev结构体
    evdev->handle.name = evdev->name;   //
    evdev->handle.handler = handler;    // 指向input_handler结构体
    evdev->handle.private = evdev;
   
error = input_register_handle(&evdev->handle);  //  注册这个handle
   
怎么读按键：
app: read
---------------------------------------------
   ..............
        evdev_read
            // 无数据并且是非阻塞方式打开，则立刻返回。
            if (client->head == client->tail && evdev->exist && (file->f_flags & O_NONBLOCK))
            return -EAGAIN; // client缓冲，如果环形缓冲头和尾是一样。表示数据是空的。并且文件是以非阻塞方式打开
                                 则再次尝试。
            // 否则休眠
            retval = wait_event_interruptible(evdev->wait  // 如果是以阻塞方式打开则马上进入休眠。
                client->head != client->tail || !evdev->exist);
               
        谁来唤醒：
        evdev_event事件里面唤醒
            wake_up_interruptible(&evdev->wait);
           
        evdev_event被谁来调用
        
        怎么写符合输入子系统框架的驱动程序？
        1，分配一个input_dev结构体
        2，设置
        3，注册
        4，硬件相关的代码，比如在中断服务程序里面上报事件。


点击(此处)折叠或打开

  1. /*
  2.  * The input core
  3.  *
  4.  * Copyright (c) 1999-2002 Vojtech Pavlik
  5.  */

  7. /*
  8.  * This program is free software; you can redistribute it and/or modify it
  9.  * under the terms of the GNU General Public License version 2 as published by
  10.  * the Free Software Foundation.
  11.  */

  13. #include <linux/init.h>
  14. #include <linux/input.h>
  15. #include <linux/module.h>
  16. #include <linux/random.h>
  17. #include <linux/major.h>
  18. #include <linux/proc_fs.h>
  19. #include <linux/seq_file.h>
  20. #include <linux/interrupt.h>
  21. #include <linux/poll.h>
  22. #include <linux/device.h>
  23. #include <linux/mutex.h>

  25. MODULE_AUTHOR("Vojtech Pavlik ");
  26. MODULE_DESCRIPTION("Input core");
  27. MODULE_LICENSE("GPL");

  29. #define INPUT_DEVICES    256

  31. static LIST_HEAD(input_dev_list);
  32. static LIST_HEAD(input_handler_list);

  34. static struct input_handler *input_table[8];

  36. /**
  37.  * input_event() - report new input event
  38.  * @dev: device that generated the event
  39.  * @type: type of the event
  40.  * @code: event code
  41.  * @value: value of the event
  42.  *
  43.  * This function should be used by drivers implementing various input devices
  44.  * See also input_inject_event()
  45.  */
  46. void input_event(struct input_dev *dev, unsigned int type, unsigned int code, int value)
  47. {
  48.     struct input_handle *handle;

  50.     if (type > EV_MAX || !test_bit(type, dev->evbit))
  51.         return;

  53.     add_input_randomness(type, code, value);

  55.     switch (type) {

  57.         case EV_SYN:
  58.             switch (code) {
  59.                 case SYN_CONFIG:
  60.                     if (dev->event)
  61.                         dev->event(dev, type, code, value);
  62.                     break;

  64.                 case SYN_REPORT:
  65.                     if (dev->sync)
  66.                         return;
  67.                     dev->sync = 1;
  68.                     break;
  69.             }
  70.             break;

  72.         case EV_KEY:

  74.             if (code > KEY_MAX || !test_bit(code, dev->keybit) || !!test_bit(code, dev->key) == value)
  75.                 return;

  77.             if (value == 2)
  78.                 break;

  80.             change_bit(code, dev->key);

  82.             if (test_bit(EV_REP, dev->evbit) && dev->rep[REP_PERIOD] && dev->rep[REP_DELAY] && dev->timer.data && value) {
  83.                 dev->repeat_key = code;
  84.                 mod_timer(&dev->timer, jiffies + msecs_to_jiffies(dev->rep[REP_DELAY]));
  85.             }

  87.             break;

  89.         case EV_SW:

  91.             if (code > SW_MAX || !test_bit(code, dev->swbit) || !!test_bit(code, dev->sw) == value)
  92.                 return;

  94.             change_bit(code, dev->sw);

  96.             break;

  98.         case EV_ABS:

  100.             if (code > ABS_MAX || !test_bit(code, dev->absbit))
  101.                 return;

  103.             if (dev->absfuzz[code]) {
  104.                 if ((value > dev->abs[code] - (dev->absfuzz[code] >> 1)) &&
  105.                  (value < dev->abs[code] + (dev->absfuzz[code] >> 1)))
  106.                     return;

  108.                 if ((value > dev->abs[code] - dev->absfuzz[code]) &&
  109.                  (value < dev->abs[code] + dev->absfuzz[code]))
  110.                     value = (dev->abs[code] * 3 + value) >> 2;

  112.                 if ((value > dev->abs[code] - (dev->absfuzz[code] << 1)) &&
  113.                  (value < dev->abs[code] + (dev->absfuzz[code] << 1)))
  114.                     value = (dev->abs[code] + value) >> 1;
  115.             }

  117.             if (dev->abs[code] == value)
  118.                 return;

  120.             dev->abs[code] = value;
  121.             break;

  123.         case EV_REL:

  125.             if (code > REL_MAX || !test_bit(code, dev->relbit) || (value == 0))
  126.                 return;

  128.             break;

  130.         case EV_MSC:

  132.             if (code > MSC_MAX || !test_bit(code, dev->mscbit))
  133.                 return;

  135.             if (dev->event)
  136.                 dev->event(dev, type, code, value);

  138.             break;

  140.         case EV_LED:

  142.             if (code > LED_MAX || !test_bit(code, dev->ledbit) || !!test_bit(code, dev->led) == value)
  143.                 return;

  145.             change_bit(code, dev->led);

  147.             if (dev->event)
  148.                 dev->event(dev, type, code, value);

  150.             break;

  152.         case EV_SND:

  154.             if (code > SND_MAX || !test_bit(code, dev->sndbit))
  155.                 return;

  157.             if (!!test_bit(code, dev->snd) != !!value)
  158.                 change_bit(code, dev->snd);

  160.             if (dev->event)
  161.                 dev->event(dev, type, code, value);

  163.             break;

  165.         case EV_REP:

  167.             if (code > REP_MAX || value < 0 || dev->rep[code] == value)
  168.                 return;

  170.             dev->rep[code] = value;
  171.             if (dev->event)
  172.                 dev->event(dev, type, code, value);

  174.             break;

  176.         case EV_FF:

  178.             if (value < 0)
  179.                 return;

  181.             if (dev->event)
  182.                 dev->event(dev, type, code, value);
  183.             break;
  184.     }

  186.     if (type != EV_SYN)
  187.         dev->sync = 0;

  189.     if (dev->grab)
  190.         dev->grab->handler->event(dev->grab, type, code, value);
  191.     else
  192.         list_for_each_entry(handle, &dev->h_list, d_node)
  193.             if (handle->open)
  194.                 handle->handler->event(handle, type, code, value);
  195. }
  196. EXPORT_SYMBOL(input_event);

  198. /**
  199.  * input_inject_event() - send input event from input handler
  200.  * @handle: input handle to send event through
  201.  * @type: type of the event
  202.  * @code: event code
  203.  * @value: value of the event
  204.  *
  205.  * Similar to input_event() but will ignore event if device is "grabbed" and handle
  206.  * injecting event is not the one that owns the device.
  207.  */
  208. void input_inject_event(struct input_handle *handle, unsigned int type, unsigned int code, int value)
  209. {
  210.     if (!handle->dev->grab || handle->dev->grab == handle)
  211.         input_event(handle->dev, type, code, value);
  212. }
  213. EXPORT_SYMBOL(input_inject_event);

  215. static void input_repeat_key(unsigned long data)
  216. {
  217.     struct input_dev *dev = (void *) data;

  219.     if (!test_bit(dev->repeat_key, dev->key))
  220.         return;

  222.     input_event(dev, EV_KEY, dev->repeat_key, 2);
  223.     input_sync(dev);

  225.     if (dev->rep[REP_PERIOD])
  226.         mod_timer(&dev->timer, jiffies + msecs_to_jiffies(dev->rep[REP_PERIOD]));
  227. }

  229. int input_grab_device(struct input_handle *handle)
  230. {
  231.     if (handle->dev->grab)
  232.         return -EBUSY;

  234.     handle->dev->grab = handle;
  235.     return 0;
  236. }
  237. EXPORT_SYMBOL(input_grab_device);

  239. void input_release_device(struct input_handle *handle)
  240. {
  241.     struct input_dev *dev = handle->dev;

  243.     if (dev->grab == handle) {
  244.         dev->grab = NULL;

  246.         list_for_each_entry(handle, &dev->h_list, d_node)
  247.             if (handle->handler->start)
  248.                 handle->handler->start(handle);
  249.     }
  250. }
  251. EXPORT_SYMBOL(input_release_device);

  253. int input_open_device(struct input_handle *handle)
  254. {
  255.     struct input_dev *dev = handle->dev;
  256.     int err;

  258.     err = mutex_lock_interruptible(&dev->mutex);
  259.     if (err)
  260.         return err;

  262.     handle->open++;

  264.     if (!dev->users++ && dev->open)
  265.         err = dev->open(dev);

  267.     if (err)
  268.         handle->open--;

  270.     mutex_unlock(&dev->mutex);

  272.     return err;
  273. }
  274. EXPORT_SYMBOL(input_open_device);

  276. int input_flush_device(struct input_handle* handle, struct file* file)
  277. {
  278.     if (handle->dev->flush)
  279.         return handle->dev->flush(handle->dev, file);

  281.     return 0;
  282. }
  283. EXPORT_SYMBOL(input_flush_device);

  285. void input_close_device(struct input_handle *handle)
  286. {
  287.     struct input_dev *dev = handle->dev;

  289.     input_release_device(handle);

  291.     mutex_lock(&dev->mutex);

  293.     if (!--dev->users && dev->close)
  294.         dev->close(dev);
  295.     handle->open--;

  297.     mutex_unlock(&dev->mutex);
  298. }
  299. EXPORT_SYMBOL(input_close_device);

  301. static int input_fetch_keycode(struct input_dev *dev, int scancode)
  302. {
  303.     switch (dev->keycodesize) {
  304.         case 1:
  305.             return ((u8 *)dev->keycode)[scancode];

  307.         case 2:
  308.             return ((u16 *)dev->keycode)[scancode];

  310.         default:
  311.             return ((u32 *)dev->keycode)[scancode];
  312.     }
  313. }

  315. static int input_default_getkeycode(struct input_dev *dev,
  316.                  int scancode, int *keycode)
  317. {
  318.     if (!dev->keycodesize)
  319.         return -EINVAL;

  321.     if (scancode < 0 || scancode >= dev->keycodemax)
  322.         return -EINVAL;

  324.     *keycode = input_fetch_keycode(dev, scancode);

  326.     return 0;
  327. }

  329. static int input_default_setkeycode(struct input_dev *dev,
  330.                  int scancode, int keycode)
  331. {
  332.     int old_keycode;
  333.     int i;

  335.     if (scancode < 0 || scancode >= dev->keycodemax)
  336.         return -EINVAL;

  338.     if (keycode < 0 || keycode > KEY_MAX)
  339.         return -EINVAL;

  341.     if (!dev->keycodesize)
  342.         return -EINVAL;

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

  347.     switch (dev->keycodesize) {
  348.         case 1: {
  349.             u8 *k = (u8 *)dev->keycode;
  350.             old_keycode = k[scancode];
  351.             k[scancode] = keycode;
  352.             break;
  353.         }
  354.         case 2: {
  355.             u16 *k = (u16 *)dev->keycode;
  356.             old_keycode = k[scancode];
  357.             k[scancode] = keycode;
  358.             break;
  359.         }
  360.         default: {
  361.             u32 *k = (u32 *)dev->keycode;
  362.             old_keycode = k[scancode];
  363.             k[scancode] = keycode;
  364.             break;
  365.         }
  366.     }

  368.     clear_bit(old_keycode, dev->keybit);
  369.     set_bit(keycode, dev->keybit);

  371.     for (i = 0; i < dev->keycodemax; i++) {
  372.         if (input_fetch_keycode(dev, i) == old_keycode) {
  373.             set_bit(old_keycode, dev->keybit);
  374.             break; /* Setting the bit twice is useless, so break */
  375.         }
  376.     }

  378.     return 0;
  379. }


  382. #define MATCH_BIT(bit, max) \
  383.         for (i = 0; i < NBITS(max); i++) \
  384.             if ((id->bit[i] & dev->bit[i]) != id->bit[i]) \
  385.                 break; \
  386.         if (i != NBITS(max)) \
  387.             continue;

  389. static const struct input_device_id *input_match_device(const struct input_device_id *id,
  390.                             struct input_dev *dev)
  391. {
  392.     int i;

  394.     for (; id->flags || id->driver_info; id++) {

  396.         if (id->flags & INPUT_DEVICE_ID_MATCH_BUS)
  397.             if (id->bustype != dev->id.bustype)
  398.                 continue;

  400.         if (id->flags & INPUT_DEVICE_ID_MATCH_VENDOR)
  401.             if (id->vendor != dev->id.vendor)
  402.                 continue;

  404.         if (id->flags & INPUT_DEVICE_ID_MATCH_PRODUCT)
  405.             if (id->product != dev->id.product)
  406.                 continue;

  408.         if (id->flags & INPUT_DEVICE_ID_MATCH_VERSION)
  409.             if (id->version != dev->id.version)
  410.                 continue;

  412.         MATCH_BIT(evbit, EV_MAX);
  413.         MATCH_BIT(keybit, KEY_MAX);
  414.         MATCH_BIT(relbit, REL_MAX);
  415.         MATCH_BIT(absbit, ABS_MAX);
  416.         MATCH_BIT(mscbit, MSC_MAX);
  417.         MATCH_BIT(ledbit, LED_MAX);
  418.         MATCH_BIT(sndbit, SND_MAX);
  419.         MATCH_BIT(ffbit, FF_MAX);
  420.         MATCH_BIT(swbit, SW_MAX);

  422.         return id;
  423.     }

  425.     return NULL;
  426. }

  428. static int input_attach_handler(struct input_dev *dev, struct input_handler *handler)
  429. {
  430.     const struct input_device_id *id;
  431.     int error;

  433.     if (handler->blacklist && input_match_device(handler->blacklist, dev))
  434.         return -ENODEV;

  436.     id = input_match_device(handler->id_table, dev);
  437.     if (!id)
  438.         return -ENODEV;

  440.     error = handler->connect(handler, dev, id);
  441.     if (error && error != -ENODEV)
  442.         printk(KERN_ERR
  443.             "input: failed to attach handler %s to device %s, "
  444.             "error: %d\n",
  445.             handler->name, kobject_name(&dev->cdev.kobj), error);

  447.     return error;
  448. }


  451. #ifdef CONFIG_PROC_FS

  453. static struct proc_dir_entry *proc_bus_input_dir;
  454. static DECLARE_WAIT_QUEUE_HEAD(input_devices_poll_wait);
  455. static int input_devices_state;

  457. static inline void input_wakeup_procfs_readers(void)
  458. {
  459.     input_devices_state++;
  460.     wake_up(&input_devices_poll_wait);
  461. }

  463. static unsigned int input_proc_devices_poll(struct file *file, poll_table *wait)
  464. {
  465.     int state = input_devices_state;

  467.     poll_wait(file, &input_devices_poll_wait, wait);
  468.     if (state != input_devices_state)
  469.         return POLLIN | POLLRDNORM;

  471.     return 0;
  472. }

  474. static struct list_head *list_get_nth_element(struct list_head *list, loff_t *pos)
  475. {
  476.     struct list_head *node;
  477.     loff_t i = 0;

  479.     list_for_each(node, list)
  480.         if (i++ == *pos)
  481.             return node;

  483.     return NULL;
  484. }

  486. static struct list_head *list_get_next_element(struct list_head *list, struct list_head *element, loff_t *pos)
  487. {
  488.     if (element->next == list)
  489.         return NULL;

  491.     ++(*pos);
  492.     return element->next;
  493. }

  495. static void *input_devices_seq_start(struct seq_file *seq, loff_t *pos)
  496. {
  497.     /* acquire lock here ... Yes, we do need locking, I knowi, I know... */

  499.     return list_get_nth_element(&input_dev_list, pos);
  500. }

  502. static void *input_devices_seq_next(struct seq_file *seq, void *v, loff_t *pos)
  503. {
  504.     return list_get_next_element(&input_dev_list, v, pos);
  505. }

  507. static void input_devices_seq_stop(struct seq_file *seq, void *v)
  508. {
  509.     /* release lock here */
  510. }

  512. static void input_seq_print_bitmap(struct seq_file *seq, const char *name,
  513.                  unsigned long *bitmap, int max)
  514. {
  515.     int i;

  517.     for (i = NBITS(max) - 1; i > 0; i--)
  518.         if (bitmap[i])
  519.             break;

  521.     seq_printf(seq, "B: %s=", name);
  522.     for (; i >= 0; i--)
  523.         seq_printf(seq, "%lx%s", bitmap[i], i > 0 ? " " : "");
  524.     seq_putc(seq, '\n');
  525. }

  527. static int input_devices_seq_show(struct seq_file *seq, void *v)
  528. {
  529.     struct input_dev *dev = container_of(v, struct input_dev, node);
  530.     const char *path = kobject_get_path(&dev->cdev.kobj, GFP_KERNEL);
  531.     struct input_handle *handle;

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

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

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

  546.     input_seq_print_bitmap(seq, "EV", dev->evbit, EV_MAX);
  547.     if (test_bit(EV_KEY, dev->evbit))
  548.         input_seq_print_bitmap(seq, "KEY", dev->keybit, KEY_MAX);
  549.     if (test_bit(EV_REL, dev->evbit))
  550.         input_seq_print_bitmap(seq, "REL", dev->relbit, REL_MAX);
  551.     if (test_bit(EV_ABS, dev->evbit))
  552.         input_seq_print_bitmap(seq, "ABS", dev->absbit, ABS_MAX);
  553.     if (test_bit(EV_MSC, dev->evbit))
  554.         input_seq_print_bitmap(seq, "MSC", dev->mscbit, MSC_MAX);
  555.     if (test_bit(EV_LED, dev->evbit))
  556.         input_seq_print_bitmap(seq, "LED", dev->ledbit, LED_MAX);
  557.     if (test_bit(EV_SND, dev->evbit))
  558.         input_seq_print_bitmap(seq, "SND", dev->sndbit, SND_MAX);
  559.     if (test_bit(EV_FF, dev->evbit))
  560.         input_seq_print_bitmap(seq, "FF", dev->ffbit, FF_MAX);
  561.     if (test_bit(EV_SW, dev->evbit))
  562.         input_seq_print_bitmap(seq, "SW", dev->swbit, SW_MAX);

  564.     seq_putc(seq, '\n');

  566.     kfree(path);
  567.     return 0;
  568. }

  570. static struct seq_operations input_devices_seq_ops = {
  571.     .start    = input_devices_seq_start,
  572.     .next    = input_devices_seq_next,
  573.     .stop    = input_devices_seq_stop,
  574.     .show    = input_devices_seq_show,
  575. };

  577. static int input_proc_devices_open(struct inode *inode, struct file *file)
  578. {
  579.     return seq_open(file, &input_devices_seq_ops);
  580. }

  582. static const struct file_operations input_devices_fileops = {
  583.     .owner        = THIS_MODULE,
  584.     .open        = input_proc_devices_open,
  585.     .poll        = input_proc_devices_poll,
  586.     .read        = seq_read,
  587.     .llseek        = seq_lseek,
  588.     .release    = seq_release,
  589. };

  591. static void *input_handlers_seq_start(struct seq_file *seq, loff_t *pos)
  592. {
  593.     /* acquire lock here ... Yes, we do need locking, I knowi, I know... */
  594.     seq->private = (void *)(unsigned long)*pos;
  595.     return list_get_nth_element(&input_handler_list, pos);
  596. }

  598. static void *input_handlers_seq_next(struct seq_file *seq, void *v, loff_t *pos)
  599. {
  600.     seq->private = (void *)(unsigned long)(*pos + 1);
  601.     return list_get_next_element(&input_handler_list, v, pos);
  602. }

  604. static void input_handlers_seq_stop(struct seq_file *seq, void *v)
  605. {
  606.     /* release lock here */
  607. }

  609. static int input_handlers_seq_show(struct seq_file *seq, void *v)
  610. {
  611.     struct input_handler *handler = container_of(v, struct input_handler, node);

  613.     seq_printf(seq, "N: Number=%ld Name=%s",
  614.          (unsigned long)seq->private, handler->name);
  615.     if (handler->fops)
  616.         seq_printf(seq, " Minor=%d", handler->minor);
  617.     seq_putc(seq, '\n');

  619.     return 0;
  620. }
  621. static struct seq_operations input_handlers_seq_ops = {
  622.     .start    = input_handlers_seq_start,
  623.     .next    = input_handlers_seq_next,
  624.     .stop    = input_handlers_seq_stop,
  625.     .show    = input_handlers_seq_show,
  626. };

  628. static int input_proc_handlers_open(struct inode *inode, struct file *file)
  629. {
  630.     return seq_open(file, &input_handlers_seq_ops);
  631. }

  633. static const struct file_operations input_handlers_fileops = {
  634.     .owner        = THIS_MODULE,
  635.     .open        = input_proc_handlers_open,
  636.     .read        = seq_read,
  637.     .llseek        = seq_lseek,
  638.     .release    = seq_release,
  639. };

  641. static int __init input_proc_init(void)
  642. {
  643.     struct proc_dir_entry *entry;

  645.     proc_bus_input_dir = proc_mkdir("input", proc_bus);
  646.     if (!proc_bus_input_dir)
  647.         return -ENOMEM;

  649.     proc_bus_input_dir->owner = THIS_MODULE;

  651.     entry = create_proc_entry("devices", 0, proc_bus_input_dir);
  652.     if (!entry)
  653.         goto fail1;

  655.     entry->owner = THIS_MODULE;
  656.     entry->proc_fops = &input_devices_fileops;

  658.     entry = create_proc_entry("handlers", 0, proc_bus_input_dir);
  659.     if (!entry)
  660.         goto fail2;

  662.     entry->owner = THIS_MODULE;
  663.     entry->proc_fops = &input_handlers_fileops;

  665.     return 0;

  667.  fail2:    remove_proc_entry("devices", proc_bus_input_dir);
  668.  fail1: remove_proc_entry("input", proc_bus);
  669.     return -ENOMEM;
  670. }

  672. static void input_proc_exit(void)
  673. {
  674.     remove_proc_entry("devices", proc_bus_input_dir);
  675.     remove_proc_entry("handlers", proc_bus_input_dir);
  676.     remove_proc_entry("input", proc_bus);
  677. }

  679. #else /* !CONFIG_PROC_FS */
  680. static inline void input_wakeup_procfs_readers(void) { }
  681. static inline int input_proc_init(void) { return 0; }
  682. static inline void input_proc_exit(void) { }
  683. #endif

  685. #define INPUT_DEV_STRING_ATTR_SHOW(name)                    \
  686. static ssize_t input_dev_show_##name(struct class_device *dev, char *buf)    \
  687. {                                        \
  688.     struct input_dev *input_dev = to_input_dev(dev);            \
  689.                                         \
  690.     return scnprintf(buf, PAGE_SIZE, "%s\n",                \
  691.              input_dev->name ? input_dev->name : "");        \
  692. }                                        \
  693. static CLASS_DEVICE_ATTR(name, S_IRUGO, input_dev_show_##name, NULL);

  695. INPUT_DEV_STRING_ATTR_SHOW(name);
  696. INPUT_DEV_STRING_ATTR_SHOW(phys);
  697. INPUT_DEV_STRING_ATTR_SHOW(uniq);

  699. static int input_print_modalias_bits(char *buf, int size,
  700.                  char name, unsigned long *bm,
  701.                  unsigned int min_bit, unsigned int max_bit)
  702. {
  703.     int len = 0, i;

  705.     len += snprintf(buf, max(size, 0), "%c", name);
  706.     for (i = min_bit; i < max_bit; i++)
  707.         if (bm[LONG(i)] & BIT(i))
  708.             len += snprintf(buf + len, max(size - len, 0), "%X,", i);
  709.     return len;
  710. }

  712. static int input_print_modalias(char *buf, int size, struct input_dev *id,
  713.                 int add_cr)
  714. {
  715.     int len;

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

  722.     len += input_print_modalias_bits(buf + len, size - len,
  723.                 'e', id->evbit, 0, EV_MAX);
  724.     len += input_print_modalias_bits(buf + len, size - len,
  725.                 'k', id->keybit, KEY_MIN_INTERESTING, KEY_MAX);
  726.     len += input_print_modalias_bits(buf + len, size - len,
  727.                 'r', id->relbit, 0, REL_MAX);
  728.     len += input_print_modalias_bits(buf + len, size - len,
  729.                 'a', id->absbit, 0, ABS_MAX);
  730.     len += input_print_modalias_bits(buf + len, size - len,
  731.                 'm', id->mscbit, 0, MSC_MAX);
  732.     len += input_print_modalias_bits(buf + len, size - len,
  733.                 'l', id->ledbit, 0, LED_MAX);
  734.     len += input_print_modalias_bits(buf + len, size - len,
  735.                 's', id->sndbit, 0, SND_MAX);
  736.     len += input_print_modalias_bits(buf + len, size - len,
  737.                 'f', id->ffbit, 0, FF_MAX);
  738.     len += input_print_modalias_bits(buf + len, size - len,
  739.                 'w', id->swbit, 0, SW_MAX);

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

  744.     return len;
  745. }

  747. static ssize_t input_dev_show_modalias(struct class_device *dev, char *buf)
  748. {
  749.     struct input_dev *id = to_input_dev(dev);
  750.     ssize_t len;

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

  754.     return min_t(int, len, PAGE_SIZE);
  755. }
  756. static CLASS_DEVICE_ATTR(modalias, S_IRUGO, input_dev_show_modalias, NULL);

  758. static struct attribute *input_dev_attrs[] = {
  759.     &class_device_attr_name.attr,
  760.     &class_device_attr_phys.attr,
  761.     &class_device_attr_uniq.attr,
  762.     &class_device_attr_modalias.attr,
  763.     NULL
  764. };

  766. static struct attribute_group input_dev_attr_group = {
  767.     .attrs    = input_dev_attrs,
  768. };

  770. #define INPUT_DEV_ID_ATTR(name)                            \
  771. static ssize_t input_dev_show_id_##name(struct class_device *dev, char *buf)    \
  772. {                                        \
  773.     struct input_dev *input_dev = to_input_dev(dev);            \
  774.     return scnprintf(buf, PAGE_SIZE, "%04x\n", input_dev->id.name);        \
  775. }                                        \
  776. static CLASS_DEVICE_ATTR(name, S_IRUGO, input_dev_show_id_##name, NULL);

  778. INPUT_DEV_ID_ATTR(bustype);
  779. INPUT_DEV_ID_ATTR(vendor);
  780. INPUT_DEV_ID_ATTR(product);
  781. INPUT_DEV_ID_ATTR(version);

  783. static struct attribute *input_dev_id_attrs[] = {
  784.     &class_device_attr_bustype.attr,
  785.     &class_device_attr_vendor.attr,
  786.     &class_device_attr_product.attr,
  787.     &class_device_attr_version.attr,
  788.     NULL
  789. };

  791. static struct attribute_group input_dev_id_attr_group = {
  792.     .name    = "id",
  793.     .attrs    = input_dev_id_attrs,
  794. };

  796. static int input_print_bitmap(char *buf, int buf_size, unsigned long *bitmap,
  797.              int max, int add_cr)
  798. {
  799.     int i;
  800.     int len = 0;

  802.     for (i = NBITS(max) - 1; i > 0; i--)
  803.         if (bitmap[i])
  804.             break;

  806.     for (; i >= 0; i--)
  807.         len += snprintf(buf + len, max(buf_size - len, 0),
  808.                 "%lx%s", bitmap[i], i > 0 ? " " : "");

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

  813.     return len;
  814. }

  816. #define INPUT_DEV_CAP_ATTR(ev, bm)                        \
  817. static ssize_t input_dev_show_cap_##bm(struct class_device *dev, char *buf)    \
  818. {                                        \
  819.     struct input_dev *input_dev = to_input_dev(dev);            \
  820.     int len = input_print_bitmap(buf, PAGE_SIZE,                \
  821.                  input_dev->bm##bit, ev##_MAX, 1);        \
  822.     return min_t(int, len, PAGE_SIZE);                    \
  823. }                                        \
  824. static CLASS_DEVICE_ATTR(bm, S_IRUGO, input_dev_show_cap_##bm, NULL);

  826. INPUT_DEV_CAP_ATTR(EV, ev);
  827. INPUT_DEV_CAP_ATTR(KEY, key);
  828. INPUT_DEV_CAP_ATTR(REL, rel);
  829. INPUT_DEV_CAP_ATTR(ABS, abs);
  830. INPUT_DEV_CAP_ATTR(MSC, msc);
  831. INPUT_DEV_CAP_ATTR(LED, led);
  832. INPUT_DEV_CAP_ATTR(SND, snd);
  833. INPUT_DEV_CAP_ATTR(FF, ff);
  834. INPUT_DEV_CAP_ATTR(SW, sw);

  836. static struct attribute *input_dev_caps_attrs[] = {
  837.     &class_device_attr_ev.attr,
  838.     &class_device_attr_key.attr,
  839.     &class_device_attr_rel.attr,
  840.     &class_device_attr_abs.attr,
  841.     &class_device_attr_msc.attr,
  842.     &class_device_attr_led.attr,
  843.     &class_device_attr_snd.attr,
  844.     &class_device_attr_ff.attr,
  845.     &class_device_attr_sw.attr,
  846.     NULL
  847. };

  849. static struct attribute_group input_dev_caps_attr_group = {
  850.     .name    = "capabilities",
  851.     .attrs    = input_dev_caps_attrs,
  852. };

  854. static struct attribute_group *input_dev_attr_groups[] = {
  855.     &input_dev_attr_group,
  856.     &input_dev_id_attr_group,
  857.     &input_dev_caps_attr_group,
  858.     NULL
  859. };

  861. static void input_dev_release(struct class_device *class_dev)
  862. {
  863.     struct input_dev *dev = to_input_dev(class_dev);

  865.     input_ff_destroy(dev);
  866.     kfree(dev);

  868.     module_put(THIS_MODULE);
  869. }

  871. /*
  872.  * Input uevent interface - loading event handlers based on
  873.  * device bitfields.
  874.  */
  875. static int input_add_uevent_bm_var(char **envp, int num_envp, int *cur_index,
  876.                  char *buffer, int buffer_size, int *cur_len,
  877.                  const char *name, unsigned long *bitmap, int max)
  878. {
  879.     if (*cur_index >= num_envp - 1)
  880.         return -ENOMEM;

  882.     envp[*cur_index] = buffer + *cur_len;

  884.     *cur_len += snprintf(buffer + *cur_len, max(buffer_size - *cur_len, 0), name);
  885.     if (*cur_len >= buffer_size)
  886.         return -ENOMEM;

  888.     *cur_len += input_print_bitmap(buffer + *cur_len,
  889.                     max(buffer_size - *cur_len, 0),
  890.                     bitmap, max, 0) + 1;
  891.     if (*cur_len > buffer_size)
  892.         return -ENOMEM;

  894.     (*cur_index)++;
  895.     return 0;
  896. }

  898. static int input_add_uevent_modalias_var(char **envp, int num_envp, int *cur_index,
  899.                      char *buffer, int buffer_size, int *cur_len,
  900.                      struct input_dev *dev)
  901. {
  902.     if (*cur_index >= num_envp - 1)
  903.         return -ENOMEM;

  905.     envp[*cur_index] = buffer + *cur_len;

  907.     *cur_len += snprintf(buffer + *cur_len, max(buffer_size - *cur_len, 0),
  908.              "MODALIAS=");
  909.     if (*cur_len >= buffer_size)
  910.         return -ENOMEM;

  912.     *cur_len += input_print_modalias(buffer + *cur_len,
  913.                      max(buffer_size - *cur_len, 0),
  914.                      dev, 0) + 1;
  915.     if (*cur_len > buffer_size)
  916.         return -ENOMEM;

  918.     (*cur_index)++;
  919.     return 0;
  920. }

  922. #define INPUT_ADD_HOTPLUG_VAR(fmt, val...)                \
  923.     do {                                \
  924.         int err = add_uevent_var(envp, num_envp, &i,        \
  925.                     buffer, buffer_size, &len,    \
  926.                     fmt, val);            \
  927.         if (err)                        \
  928.             return err;                    \
  929.     } while (0)

  931. #define INPUT_ADD_HOTPLUG_BM_VAR(name, bm, max)                \
  932.     do {                                \
  933.         int err = input_add_uevent_bm_var(envp, num_envp, &i,    \
  934.                     buffer, buffer_size, &len,    \
  935.                     name, bm, max);            \
  936.         if (err)                        \
  937.             return err;                    \
  938.     } while (0)

  940. #define INPUT_ADD_HOTPLUG_MODALIAS_VAR(dev)                \
  941.     do {                                \
  942.         int err = input_add_uevent_modalias_var(envp,        \
  943.                     num_envp, &i,            \
  944.                     buffer, buffer_size, &len,    \
  945.                     dev);                \
  946.         if (err)                        \
  947.             return err;                    \
  948.     } while (0)

  950. static int input_dev_uevent(struct class_device *cdev, char **envp,
  951.              int num_envp, char *buffer, int buffer_size)
  952. {
  953.     struct input_dev *dev = to_input_dev(cdev);
  954.     int i = 0;
  955.     int len = 0;

  957.     INPUT_ADD_HOTPLUG_VAR("PRODUCT=%x/%x/%x/%x",
  958.                 dev->id.bustype, dev->id.vendor,
  959.                 dev->id.product, dev->id.version);
  960.     if (dev->name)
  961.         INPUT_ADD_HOTPLUG_VAR("NAME=\"%s\"", dev->name);
  962.     if (dev->phys)
  963.         INPUT_ADD_HOTPLUG_VAR("PHYS=\"%s\"", dev->phys);
  964.     if (dev->uniq)
  965.         INPUT_ADD_HOTPLUG_VAR("UNIQ=\"%s\"", dev->uniq);

  967.     INPUT_ADD_HOTPLUG_BM_VAR("EV=", dev->evbit, EV_MAX);
  968.     if (test_bit(EV_KEY, dev->evbit))
  969.         INPUT_ADD_HOTPLUG_BM_VAR("KEY=", dev->keybit, KEY_MAX);
  970.     if (test_bit(EV_REL, dev->evbit))
  971.         INPUT_ADD_HOTPLUG_BM_VAR("REL=", dev->relbit, REL_MAX);
  972.     if (test_bit(EV_ABS, dev->evbit))
  973.         INPUT_ADD_HOTPLUG_BM_VAR("ABS=", dev->absbit, ABS_MAX);
  974.     if (test_bit(EV_MSC, dev->evbit))
  975.         INPUT_ADD_HOTPLUG_BM_VAR("MSC=", dev->mscbit, MSC_MAX);
  976.     if (test_bit(EV_LED, dev->evbit))
  977.         INPUT_ADD_HOTPLUG_BM_VAR("LED=", dev->ledbit, LED_MAX);
  978.     if (test_bit(EV_SND, dev->evbit))
  979.         INPUT_ADD_HOTPLUG_BM_VAR("SND=", dev->sndbit, SND_MAX);
  980.     if (test_bit(EV_FF, dev->evbit))
  981.         INPUT_ADD_HOTPLUG_BM_VAR("FF=", dev->ffbit, FF_MAX);
  982.     if (test_bit(EV_SW, dev->evbit))
  983.         INPUT_ADD_HOTPLUG_BM_VAR("SW=", dev->swbit, SW_MAX);

  985.     INPUT_ADD_HOTPLUG_MODALIAS_VAR(dev);

  987.     envp[i] = NULL;
  988.     return 0;
  989. }

  991. struct class input_class = {
  992.     .name            = "input",
  993.     .release        = input_dev_release,
  994.     .uevent            = input_dev_uevent,
  995. };
  996. EXPORT_SYMBOL_GPL(input_class);

  998. /**
  999.  * input_allocate_device - allocate memory for new input device
  1000.  *
  1001.  * Returns prepared struct input_dev or NULL.
  1002.  *
  1003.  * NOTE: Use input_free_device() to free devices that have not been
  1004.  * registered; input_unregister_device() should be used for already
  1005.  * registered devices.
  1006.  */
  1007. struct input_dev *input_allocate_device(void)
  1008. {
  1009.     struct input_dev *dev;

  1011.     dev = kzalloc(sizeof(struct input_dev), GFP_KERNEL);
  1012.     if (dev) {
  1013.         dev->cdev.class = &input_class;
  1014.         dev->cdev.groups = input_dev_attr_groups;
  1015.         class_device_initialize(&dev->cdev);
  1016.         mutex_init(&dev->mutex);
  1017.         INIT_LIST_HEAD(&dev->h_list);
  1018.         INIT_LIST_HEAD(&dev->node);

  1020.         __module_get(THIS_MODULE);
  1021.     }

  1023.     return dev;
  1024. }
  1025. EXPORT_SYMBOL(input_allocate_device);

  1027. /**
  1028.  * input_free_device - free memory occupied by input_dev structure
  1029.  * @dev: input device to free
  1030.  *
  1031.  * This function should only be used if input_register_device()
  1032.  * was not called yet or if it failed. Once device was registered
  1033.  * use input_unregister_device() and memory will be freed once last
  1034.  * refrence to the device is dropped.
  1035.  *
  1036.  * Device should be allocated by input_allocate_device().
  1037.  *
  1038.  * NOTE: If there are references to the input device then memory
  1039.  * will not be freed until last reference is dropped.
  1040.  */
  1041. void input_free_device(struct input_dev *dev)
  1042. {
  1043.     if (dev)
  1044.         input_put_device(dev);
  1045. }
  1046. EXPORT_SYMBOL(input_free_device);

  1048. /**
  1049.  * input_set_capability - mark device as capable of a certain event
  1050.  * @dev: device that is capable of emitting or accepting event
  1051.  * @type: type of the event (EV_KEY, EV_REL, etc...)
  1052.  * @code: event code
  1053.  *
  1054.  * In addition to setting up corresponding bit in appropriate capability
  1055.  * bitmap the function also adjusts dev->evbit.
  1056.  */
  1057. void input_set_capability(struct input_dev *dev, unsigned int type, unsigned int code)
  1058. {
  1059.     switch (type) {
  1060.     case EV_KEY:
  1061.         __set_bit(code, dev->keybit);
  1062.         break;

  1064.     case EV_REL:
  1065.         __set_bit(code, dev->relbit);
  1066.         break;

  1068.     case EV_ABS:
  1069.         __set_bit(code, dev->absbit);
  1070.         break;

  1072.     case EV_MSC:
  1073.         __set_bit(code, dev->mscbit);
  1074.         break;

  1076.     case EV_SW:
  1077.         __set_bit(code, dev->swbit);
  1078.         break;

  1080.     case EV_LED:
  1081.         __set_bit(code, dev->ledbit);
  1082.         break;

  1084.     case EV_SND:
  1085.         __set_bit(code, dev->sndbit);
  1086.         break;

  1088.     case EV_FF:
  1089.         __set_bit(code, dev->ffbit);
  1090.         break;

  1092.     default:
  1093.         printk(KERN_ERR
  1094.             "input_set_capability: unknown type %u (code %u)\n",
  1095.             type, code);
  1096.         dump_stack();
  1097.         return;
  1098.     }

  1100.     __set_bit(type, dev->evbit);
  1101. }
  1102. EXPORT_SYMBOL(input_set_capability);

  1104. int input_register_device(struct input_dev *dev)
  1105. {
  1106.     static atomic_t input_no = ATOMIC_INIT(0);
  1107.     struct input_handler *handler;
  1108.     const char *path;
  1109.     int error;

  1111.     set_bit(EV_SYN, dev->evbit);

  1113.     /*
  1114.      * If delay and period are pre-set by the driver, then autorepeating
  1115.      * is handled by the driver itself and we don't do it in input.c.
  1116.      */

  1118.     init_timer(&dev->timer);
  1119.     if (!dev->rep[REP_DELAY] && !dev->rep[REP_PERIOD]) {
  1120.         dev->timer.data = (long) dev;
  1121.         dev->timer.function = input_repeat_key;
  1122.         dev->rep[REP_DELAY] = 250;
  1123.         dev->rep[REP_PERIOD] = 33;
  1124.     }

  1126.     if (!dev->getkeycode)
  1127.         dev->getkeycode = input_default_getkeycode;

  1129.     if (!dev->setkeycode)
  1130.         dev->setkeycode = input_default_setkeycode;

  1132.     list_add_tail(&dev->node, &input_dev_list);

  1134.     snprintf(dev->cdev.class_id, sizeof(dev->cdev.class_id),
  1135.          "input%ld", (unsigned long) atomic_inc_return(&input_no) - 1);

  1137.     if (!dev->cdev.dev)
  1138.         dev->cdev.dev = dev->dev.parent;

  1140.     error = class_device_add(&dev->cdev);
  1141.     if (error)
  1142.         return error;

  1144.     path = kobject_get_path(&dev->cdev.kobj, GFP_KERNEL);
  1145.     printk(KERN_INFO "input: %s as %s\n",
  1146.         dev->name ? dev->name : "Unspecified device", path ? path : "N/A");
  1147.     kfree(path);

  1149.     list_for_each_entry(handler, &input_handler_list, node)
  1150.         input_attach_handler(dev, handler);

  1152.     input_wakeup_procfs_readers();

  1154.     return 0;
  1155. }
  1156. EXPORT_SYMBOL(input_register_device);

  1158. void input_unregister_device(struct input_dev *dev)
  1159. {
  1160.     struct input_handle *handle, *next;
  1161.     int code;

  1163.     for (code = 0; code <= KEY_MAX; code++)
  1164.         if (test_bit(code, dev->key))
  1165.             input_report_key(dev, code, 0);
  1166.     input_sync(dev);

  1168.     del_timer_sync(&dev->timer);

  1170.     list_for_each_entry_safe(handle, next, &dev->h_list, d_node)
  1171.         handle->handler->disconnect(handle);
  1172.     WARN_ON(!list_empty(&dev->h_list));

  1174.     list_del_init(&dev->node);

  1176.     class_device_unregister(&dev->cdev);

  1178.     input_wakeup_procfs_readers();
  1179. }
  1180. EXPORT_SYMBOL(input_unregister_device);

  1182. int input_register_handler(struct input_handler *handler)
  1183. {
  1184.     struct input_dev *dev;

  1186.     INIT_LIST_HEAD(&handler->h_list);

  1188.     if (handler->fops != NULL) {
  1189.         if (input_table[handler->minor >> 5])
  1190.             return -EBUSY;

  1192.         input_table[handler->minor >> 5] = handler;
  1193.     }

  1195.     list_add_tail(&handler->node, &input_handler_list);

  1197.     list_for_each_entry(dev, &input_dev_list, node)
  1198.         input_attach_handler(dev, handler);

  1200.     input_wakeup_procfs_readers();
  1201.     return 0;
  1202. }
  1203. EXPORT_SYMBOL(input_register_handler);

  1205. void input_unregister_handler(struct input_handler *handler)
  1206. {
  1207.     struct input_handle *handle, *next;

  1209.     list_for_each_entry_safe(handle, next, &handler->h_list, h_node)
  1210.         handler->disconnect(handle);
  1211.     WARN_ON(!list_empty(&handler->h_list));

  1213.     list_del_init(&handler->node);

  1215.     if (handler->fops != NULL)
  1216.         input_table[handler->minor >> 5] = NULL;

  1218.     input_wakeup_procfs_readers();
  1219. }
  1220. EXPORT_SYMBOL(input_unregister_handler);

  1222. int input_register_handle(struct input_handle *handle)
  1223. {
  1224.     struct input_handler *handler = handle->handler;

  1226.     list_add_tail(&handle->d_node, &handle->dev->h_list);
  1227.     list_add_tail(&handle->h_node, &handler->h_list);

  1229.     if (handler->start)
  1230.         handler->start(handle);

  1232.     return 0;
  1233. }
  1234. EXPORT_SYMBOL(input_register_handle);

  1236. void input_unregister_handle(struct input_handle *handle)
  1237. {
  1238.     list_del_init(&handle->h_node);
  1239.     list_del_init(&handle->d_node);
  1240. }
  1241. EXPORT_SYMBOL(input_unregister_handle);

  1243. static int input_open_file(struct inode *inode, struct file *file)
  1244. {   // 根据所打开文件的次设备号，得到一个input_handler
  1245.     struct input_handler *handler = input_table[iminor(inode) >> 5]; // 分配一个input_handler结构体
  1246.     const struct file_operations *old_fops, *new_fops = NULL;
  1247.     int err;

  1249.     /* No load-on-demand here? */
  1250.     if (!handler || !(new_fops = fops_get(handler->fops))) // new_fops与handler中的fops不一样则返回。
  1251.         return -ENODEV;

  1253.     /*
  1254.      * That's _really_ odd. Usually NULL ->open means "nothing special",
  1255.      * not "no device". Oh, well...
  1256.      */
  1257.     if (!new_fops->open) {       // 如果新的fops中的open没有被打开。
  1258.         fops_put(new_fops);      // 就将fpos放入新的fops中。
  1259.         return -ENODEV;
  1260.     }                            // 否则将新fops写入旧的fops中。
  1261.     old_fops = file->f_op;
  1262.     file->f_op = new_fops;     // 将新的fops传入旧的fops

  1264.     err = new_fops->open(inode, file);   // 返回新的fops

  1266.     if (err) {                           // 如果新的fops被打开
  1267.         fops_put(file->f_op);
  1268.         file->f_op = fops_get(old_fops);
  1269.     }
  1270.     fops_put(old_fops);
  1271.     return err;                           //  返回fops
  1272. }

  1274. static const struct file_operations input_fops = {
  1275.     .owner = THIS_MODULE,
  1276.     .open = input_open_file,
  1277. };

  1279. static int __init input_init(void)
  1280. {
  1281.     int err;

  1283.     err = class_register(&input_class);
  1284.     if (err) {
  1285.         printk(KERN_ERR "input: unable to register input_dev class\n");
  1286.         return err;
  1287.     }

  1289.     err = input_proc_init();
  1290.     if (err)
  1291.         goto fail1;

  1293.     err = register_chrdev(INPUT_MAJOR, "input", &input_fops);
  1294.     if (err) {
  1295.         printk(KERN_ERR "input: unable to register char major %d", INPUT_MAJOR);
  1296.         goto fail2;
  1297.     }

  1299.     return 0;

  1301.  fail2:    input_proc_exit();
  1302.  fail1:    class_unregister(&input_class);
  1303.     return err;
  1304. }

  1306. static void __exit input_exit(void)
  1307. {
  1308.     input_proc_exit();
  1309.     unregister_chrdev(INPUT_MAJOR, "input");
  1310.     class_unregister(&input_class);
  1311. }

  1313. subsys_initcall(input_init);
  1314. module_exit(input_exit);

要看一个驱动程序，首先要从入口函数开始看。
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