1、輸入子系統 -event 層分析drivers/input/keyboard/gpio_keys.c:static int _devinit gpio_keys_probe(struct platform_device *pdev)struct gpio_keys_platform_data *pdata = pdev->dev.platform_data;struct input_dev *input;int i, error;input = input_allocate_device();/ 申請input_dev 結構if (!input)return -ENOMEM; p

2、latform_set_drvdata(pdev, input);/ 把 input_dev 結構放好 (以后方便調用 ) input->evbit0 = BIT(EV_KEY);/ 目前 event 的類型不操作 32,所以你會看到對于 evbit 數組的操作都是對 evbit0 中的位 來進行操作 . input->name = pdev->name;input->phys = "gpio-keys/input0" input->dev.parent = &pdev->d

3、ev;input->id.bustype = BUS_HOST; input->id.vendor = 0x0001; input->duct = 0x0001;input->id.version = 0x0100; for (i = 0; i <pdata->nbuttons; i+) struct gpio_keys_button *button =&pdata->buttonsi;int irq = gpio_to_irq(button->gpio)

4、;unsigned int type = button->type ?: EV_KEY;set_irq_type(irq, IRQ_TYPE_EDGE_BOTH); /* 根據 用戶所指定的 gpio_keys 來申請中斷和注冊中斷處理函數 */ error = request_irq(irq, gpio_keys_isr,IRQF_SAMPLE_RANDOM,button->desc ? button->desc :"gpio_keys",pdev);if (error) printk(KERN_ERR "gpio-ke

5、ys: unable to claimirq %d; error %dn",irq, error);goto fail; input_set_capability(input, type, button->code);error = input_register_device(input);/ 注冊輸入設備并和對應的 handler 處理函數掛鉤if (error) printk(KERN_ERR "Unable to register gpio-keys input devicen");goto fail; return 0; fail:for (

6、i = i - 1; i >= 0; i-)free_irq(gpio_to_irq(pdata->buttonsi.gpio), pdev); input_free_device(input); return error;提到 input_dev 結構 ,以下談一下我對于它的理解 :struct input_dev void *private; const char *name;const char *phys;const char *uniq;struct input_id id;/* 根據各種輸入信號的類型來建立類型為 unsigned long 的數組 ,

7、* 數組的每 1bit 代表一種信號類型 , * 內核中會對其進行置位或清位操作來表示時間的發生和 被處理 .*/ unsigned long evbitNBITS(EV_MAX);unsigned long keybitNBITS(KEY_MAX);unsigned long relbitNBITS(REL_MAX);unsigned long absbitNBITS(ABS_MAX);unsigned long mscbitNBITS(MSC_MAX);unsigned long ledbitNBITS(LED_MAX);unsigned long sndbitNBITS(SND_MAX)

8、; unsigned long ffbitNBITS(FF_MAX);unsigned long swbitNBITS(SW_MAX); ;/* 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 correspo

9、nding bit in appropriate capability* bitmap the function also adjusts dev->evbit.*/* 記錄本設備對于哪些事件感興趣 (對其進行處理 )*/ void input_set_capability(struct input_dev *dev, unsigned int type, unsigned int code)switch (type) case EV_KEY:_set_bit(code, dev->keybit);/ 比如按鍵 , 應該對哪 些鍵值的按鍵進行處理 (對于其它按鍵不予

10、理睬 )break; case EV_REL:_set_bit(code, dev->relbit);break; case EV_ABS:_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(

11、code, dev->sndbit);break; case EV_FF:_set_bit(code, dev->ffbit);break; default:printk(KERN_ERR"input_set_capability: unknown type %u(code %u)n",type, code);dump_stack();return;_set_bit(type, dev->evbit);/ 感覺和前面重復了(前面一經配置過一次了 )EXPORT_SYMBOL(input_set_capability);static

12、irqreturn_t gpio_keys_isr(int irq, void *dev_id)int i;struct platform_device *pdev = dev_id;struct gpio_keys_platform_data *pdata =pdev->dev.platform_data;struct input_dev *input = platform_get_drvdata(pdev);for (i = 0; i < pdata->nbuttons; i+) struct gpio_keys_button *button =&

13、amp;amp;pdata->buttonsi;int gpio = button->gpio;if (irq = gpio_to_irq(gpio) / 判斷哪個鍵被按了 ? unsigned int type = button->type ?: EV_KEY;int state = (gpio_get_value(gpio)1 : 0) A button->activeow; 記錄按鍵狀態 input_event(input, type, button->code, !state);/ 匯報輸入事 件input_sync

14、(input);/ 等待輸入事件處理完成 return IRQ_HANDLED;/* 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* See also input_inject_event()*/vo

15、id input_event(struct input_dev *dev, unsigned int type, unsigned int code, int value)struct input_handle *handle; if (type > EV_MAX| !test_bit(type, dev->evbit)/ 首先判斷該事件類型是否有 效且為該設備所接受return; add_input_randomness(type, code, value); switch (code) case SYN_CONFIG:if (dev->event)

16、dev->event(dev, type, code, value);break; caseSYN_REPORT:if (dev->sync)return;dev->sync = 1;break;break; case EV_KEY:/* 這里需要滿足幾個條件 :* 1:鍵值有效 (不超出定義的鍵值的有效范圍 )* 2:鍵值為設備所能接受 (屬于該設備所擁有的鍵值范圍 )* 3: 按鍵狀態改變了*/ if (code > KEY_MAX| !test_bit(code, dev->keybit) | !test_bit(co

17、de, dev->key) = value)dev->key);/ 改變對應按鍵的狀態 /* 如果你 希望按鍵未釋放的時候不斷匯報按鍵事件的話需要以下這 個 (在簡單的 gpio_keys 驅動中不需要這個 ,暫時不去分析 ) */if (test_bit(EV_REP, dev->evbit) && dev->repREP_PERIOD && dev->repREP_DELAY && dev->timer.data

18、 && value) dev->repeat_key = code; mod_timer(&dev->timer, jiffies + msecs_to_jiffies(dev->repREP_DELAY); break; if (type != EV_SYN) dev->sync = 0; if (dev->grab) dev->grab->handler->event(dev->grab, type, code, va

19、lue);else/* 循環調用所有處理該設備的 handle(event,mouse,ts,joy 等 ),* 如果有進程打開了這些handle(進行讀寫),則調用其對應的event接口向氣匯報該輸入事件*/list_for_each_entry(handle, &dev->h_list,d_node)if (handle->open)handle->handler->event(handle, type,code, value);EXPORT_SYMBOL(input_event);# # 好了 ,下面再來研究一下 e

20、vent 層對于 input 層報告的這個鍵 盤輸入事件是如何來處理的 .# #drivers/input/evdev.c:static struct input_handler evdev_handler = .event =evdev_event,.connect =evdev_connect,.disconnect =evdev_disconnect,.fops =&evdev_fops,.minor =EVDEV_MINOR_BASE,.name =evdev",.id_table =evdev_ids,;static void evdev_event(str

21、uct input_handle *handle, unsignedint type, unsigned int code, int value)struct evdev *evdev = handle->private;struct evdev_client *client; if(evdev->grab) client = evdev->grab;do_gettimeofday(&client->bufferclient->head.time );client->bufferclient-&

22、amp;gt;head.type = type;client->bufferclient->head.code = code;client->bufferclient->head.value = value;client->head = (client->head + 1)& (EVDEV_BUFFER_SIZE - 1); kill_fasync(&client->fasync, SIGIO, POLL_IN); else/* 遍厲 client_list 鏈表中

23、的 client 結構（代表些打開evdev的進程（個人理解A_A） */&evdev->client_list, node) /* 填充代表該輸入信號的 struct input_event 結構 (事件 ,類型 ,鍵碼 ,鍵值 ) */do_gettimeofday(&client->bufferclient->head.time );client->bufferclient->head.type = type;client->bufferclient->hea

24、d.code = code;client->bufferclient->head.value = value;/* 更新寫指針 */ client->head = (client->head + 1) & (EVDEV_BUFFER_SIZE - 1);kill_fasync(&client->fasync, SIGIO, POLL_IN);/ 通知 調用 input_sync 的進程 :輸入事件經已處理完畢 ( 通知底層 ). wake_up_interruptible(&e

25、vdev->wait);/ 喚醒睡眠在 evdev->wait 等待隊列等待輸入信息的進程 (通知上層 ). # #好了 ,至此一個按鍵的輸入事件處理完畢 ,現在再來從上到上 的來看看用戶是如何獲取這個輸入事件的 .# #static const struct file_operations evdev_fops = .owner =THIS_MODULE,.read =evdev_read,.write =evdev_write,.poll =evdev_poll,.open =evdev_open,.release =evdev_release,.unlocke

26、d_ioctlevdev_ioctl,#ifdef CONFIG_COMPAT.compat_ioctl = evdev_ioctl_compat,#endif.fasync =evdev_fasync,.flush =evdev_flush;static int evdev_open(struct inode *inode, struct file *file) struct evdev_client *client;struct evdev *evdev;int i = iminor(inode) - EVDEV_MINOR_BASE;int error;if (i >= E

27、VDEV_MINORS)return -ENODEV;evdev =evdev_tablei;if (!evdev | !evdev->exist)return -ENODEV;client =kzalloc(sizeof(struct evdev_client), GFP_KERNEL);if (!client)return -ENOMEM;client->evdev = evdev;/* 添加 evdev_client 結構到鏈表 evdev->client_list 中 (好讓輸入事件到來的時候填寫該結構 并喚醒進程讀取 ) */list_add

28、_tail(&client->node, &evdev->client_list); if (!evdev->open+ && evdev->exist) error = input_open_device(&evdev->handle);if (error) list_del(&client->node);kfree(client);return error;file->private_data =

29、client;/ 存放好 evdev_client 結構方便以后使用return 0;static ssize_t evdev_read(struct file *file, char _user *buffer, size_t count, loff_t *ppos)struct evdev_client *client = file->private_data; struct evdev *evdev = client->evdev;int retval; if (count <evdev_event_size()對于每次讀取的數據大小是有一定的要

30、 求.return -EINV AL;if(client->head = client->tail && evdev->exist && (file->f_flags &O_NONBLOCK)/ 緩存中沒有數據可讀且設備是存在的 ,如果設置為 NONBLOCK 方式來讀 ,立即返回 .return -EAGAIN;retval =wait_event_interruptible(evdev->wait,client->head !=

31、 client->tail| !evdev->exist);/ 否則等待緩存有數據可讀或設備不存在(被移去 )if (retval)return retval; return -ENODEV;if (!evdev->exist)while(client->head != client->tail && retval + evdev_event_size() <= count) / 下面開始讀取數據 struct input_event *event = (struct input

32、_event *) client->buffer + client->tail;/ 獲取緩存中的讀指針 if (evdev_event_to_user(buffer + retval, event)/ 返回數據給用 戶return -EFAULT;client->tail = (client->tail + 1) & (EVDEV_BUFFER_SIZE - 1);/ 更新讀指針 retval += evdev_event_size(); return retval;呵呵，看到了吧，應用程序就是這樣獲取輸入事件的A_A#

33、# #本來對于 gpio_keys 這樣的驅動程序 ,只要當發生按鍵事件的 時候向上層應用程序匯報鍵值即可 .不過 ,對于一些帶輸出設 備(例如 led 燈)的輸入設備來說 (例如鍵盤 ),上層應用程序同 樣可以利用 event 層來讀取或改變其狀態 .請看以下代碼 : # #static ssize_t evdev_write(struct file *file, const char _user *buffer, size_t count, loff_t *ppos)struct evdev_client *client = file->private_data;struct

34、 evdev *evdev = client->evdev;struct input_event event;int retval = 0;if (!evdev->exist)return -ENODEV;while (retval <count) if (evdev_event_from_user(buffer + retval, &event)/ 從用戶處獲取事件結構return -EFAULT; input_inject_event(&evdev->handle, event.type, event.

35、code, event.value);/ 往底層發送事件retval += evdev_event_size(); return retval;/* input_inject_event() - send input event from input handler* handle: input handle to send event through* type: type of the event* code: event codevalue: value of the event* Similar to input_event() but will ignore event if dev

36、ice is "grabbed" and handle* injecting event is not the one that owns the device.*/void input_inject_event(struct input_handle *handle, unsigned int type, unsigned int code, int value)if (!handle->dev->grab | handle->dev->grab = handle) input_event(handle-&g

37、t;dev, type, code, value); EXPORT_SYMBOL(input_inject_event);/* input_event() - report new input event* dev: device that generated the event* type: type of the event* code: event code* value: value of the eventThis function should be used by drivers implementingvarious input devices* See also input_inject_event()*/void input_event(struct input_dev *dev, unsigned int type, unsigned int code, int value)struct input_handle *handle; if (type > EV