原文鏈接地址：http://www.linuxidc.com/Linux/2012-12/76197p9.htm

?

跟USB鼠標類型一樣，USB鍵盤也屬于HID類型，代碼在/dirver/hid/usbhid/usbkbd.c下。USB鍵盤除了提交中斷URB外，還需要提交控制URB。不多話，我們看代碼

[cpp]?view plaincopy

static?int?__init?usb_kbd_init(void)??

{??

????int?result?=?usb_register(&usb_kbd_driver);??

????if?(result?==?0)??

????????printk(KERN_INFO?KBUILD_MODNAME?":?"?DRIVER_VERSION?":"??

????????????????DRIVER_DESC?"\n");??

????return?result;??

}??

[cpp]?view plaincopy

static?struct?usb_driver?usb_kbd_driver?=?{??

????.name?=?????"usbkbd",??

????.probe?=????usb_kbd_probe,??

????.disconnect?=???usb_kbd_disconnect,??

????.id_table?=?usb_kbd_id_table,???????//驅動設備ID表,用來指定設備或接口??

};??

下面跟蹤usb_driver中的probe

?

[cpp]?view plaincopy

static?int?usb_kbd_probe(struct?usb_interface?*iface,??

?????????????const?struct?usb_device_id?*id)??

{??

????struct?usb_device?*dev?=?interface_to_usbdev(iface);????//通過接口獲取USB設備指針??

????struct?usb_host_interface?*interface;???????????????????//設置??

????struct?usb_endpoint_descriptor?*endpoint;???????????????//端點描述符??

????struct?usb_kbd?*kbd;????????????????????????????????????//usb_kbd私有數據??

????struct?input_dev?*input_dev;????????????????????????????//input設備??

????int?i,?pipe,?maxp;??

????int?error?=?-ENOMEM;??

??

????interface?=?iface->cur_altsetting;???????????????????????//獲取設置??

??

????if?(interface->desc.bNumEndpoints?!=?1)??????????????????//與mouse一樣只有一個端點????

????????return?-ENODEV;??

??

????endpoint?=?&interface->endpoint[0].desc;?????????????//獲取端點描述符??

????if?(!usb_endpoint_is_int_in(endpoint))??????????????????//檢查端點是否為中斷輸入端點??

????????return?-ENODEV;??

??

????pipe?=?usb_rcvintpipe(dev,?endpoint->bEndpointAddress);??//將endpoint設置為中斷IN端點??

????maxp?=?usb_maxpacket(dev,?pipe,?usb_pipeout(pipe));?????//端點傳輸的最大數據包??

??

????kbd?=?kzalloc(sizeof(struct?usb_kbd),?GFP_KERNEL);??????//分配urb??

????input_dev?=?input_allocate_device();????????????????????//分配input設備空間??

????if?(!kbd?||?!input_dev)??

????????goto?fail1;??

??

????if?(usb_kbd_alloc_mem(dev,?kbd))????????????????????????//分配urb空間和其他緩沖區??

????????goto?fail2;??

??

????kbd->usbdev?=?dev;???????????????????????????????????????//給內嵌結構體賦值??

????kbd->dev?=?input_dev;??

??

????if?(dev->manufacturer)???//拷貝廠商ID??

????????strlcpy(kbd->name,?dev->manufacturer,?sizeof(kbd->name));??

??

????if?(dev->product)?{??????//拷貝產品ID??

????????if?(dev->manufacturer)??

????????????strlcat(kbd->name,?"?",?sizeof(kbd->name));??

????????strlcat(kbd->name,?dev->product,?sizeof(kbd->name));??

????}??

??

????if?(!strlen(kbd->name))??//檢測不到廠商名字??

????????snprintf(kbd->name,?sizeof(kbd->name),??

?????????????"USB?HIDBP?Keyboard?%04x:%04x",??

?????????????le16_to_cpu(dev->descriptor.idVendor),??

?????????????le16_to_cpu(dev->descriptor.idProduct));??

????//設備鏈接地址??

????usb_make_path(dev,?kbd->phys,?sizeof(kbd->phys));??

????strlcat(kbd->phys,?"/input0",?sizeof(kbd->phys));??

??

????input_dev->name?=?kbd->name;??????????//給input_dev結構體賦值??

????input_dev->phys?=?kbd->phys;??

????usb_to_input_id(dev,?&input_dev->id);????//拷貝usb_driver的支持給input,設置bustype,vendo,product等??

????input_dev->dev.parent?=?&iface->dev;??

??

????input_set_drvdata(input_dev,?kbd);??????//將kbd設置為input的私有數據??

??

????input_dev->evbit[0]?=?BIT_MASK(EV_KEY)?|?BIT_MASK(EV_LED)?|??

????????BIT_MASK(EV_REP);???????????????????//支持的按鍵事件類型??

????input_dev->ledbit[0]?=?BIT_MASK(LED_NUML)?|?BIT_MASK(LED_CAPSL)?|??

????????BIT_MASK(LED_SCROLLL)?|?BIT_MASK(LED_COMPOSE)?|??

????????BIT_MASK(LED_KANA);?????????????????//EV_LED事件支持的事件碼??

??

????for?(i?=?0;?i?<?255;?i++)??

????????set_bit(usb_kbd_keycode[i],?input_dev->keybit);??//EV_KEY事件支持的事件碼(即設置支持的鍵盤碼)??

????clear_bit(0,?input_dev->keybit);??

??

????input_dev->event?=?usb_kbd_event;????????//定義event函數??

????input_dev->open?=?usb_kbd_open;??

????input_dev->close?=?usb_kbd_close;??

??

????usb_fill_int_urb(kbd->irq,?dev,?pipe,??

?????????????kbd->new,?(maxp?>?8???8?:?maxp),??

?????????????usb_kbd_irq,?kbd,?endpoint->bInterval);//填充中斷urb??

????kbd->irq->transfer_dma?=?kbd->new_dma;??

????kbd->irq->transfer_flags?|=?URB_NO_TRANSFER_DMA_MAP;??

??

????kbd->cr->bRequestType?=?USB_TYPE_CLASS?|?USB_RECIP_INTERFACE;??

????kbd->cr->bRequest?=?0x09;//設置控制請求的格式??

????kbd->cr->wValue?=?cpu_to_le16(0x200);??

????kbd->cr->wIndex?=?cpu_to_le16(interface->desc.bInterfaceNumber);??

????kbd->cr->wLength?=?cpu_to_le16(1);??

??

????usb_fill_control_urb(kbd->led,?dev,?usb_sndctrlpipe(dev,?0),??

?????????????????(void?*)?kbd->cr,?kbd->leds,?1,??

?????????????????usb_kbd_led,?kbd);//填充控制urb??

????kbd->led->transfer_dma?=?kbd->leds_dma;??

????kbd->led->transfer_flags?|=?URB_NO_TRANSFER_DMA_MAP;??

??

????error?=?input_register_device(kbd->dev);??

????if?(error)??

????????goto?fail2;??

??

????usb_set_intfdata(iface,?kbd);??

????device_set_wakeup_enable(&dev->dev,?1);??

????return?0;??

??

fail2:????

????usb_kbd_free_mem(dev,?kbd);??

fail1:????

????input_free_device(input_dev);??

????kfree(kbd);??

????return?error;??

}??

?

在上面的probe中，我們主要是初始化一些結構體，然后提交中斷urb和控制urb，并注冊input設備。其中有幾個地方需要細看下，其一，usb_kbd_alloc_mem的實現。其二，設置控制請求的格式。

先來看看usb_kbd_alloc_mem的實現

?

[cpp]?view plaincopy

static?int?usb_kbd_alloc_mem(struct?usb_device?*dev,?struct?usb_kbd?*kbd)??

{??

????if?(!(kbd->irq?=?usb_alloc_urb(0,?GFP_KERNEL)))??????//分配中斷urb??

????????return?-1;??

????if?(!(kbd->led?=?usb_alloc_urb(0,?GFP_KERNEL)))??????//分配控制urb??

????????return?-1;??

????if?(!(kbd->new?=?usb_alloc_coherent(dev,?8,?GFP_ATOMIC,?&kbd->new_dma)))??

????????return?-1;??????//分配中斷urb使用的緩沖區??

????if?(!(kbd->cr?=?kmalloc(sizeof(struct?usb_ctrlrequest),?GFP_KERNEL)))??

????????return?-1;??????//分配控制urb使用的控制請求描述符??

????if?(!(kbd->leds?=?usb_alloc_coherent(dev,?1,?GFP_ATOMIC,?&kbd->leds_dma)))??

????????return?-1;??????//分配控制urb使用的緩沖區??

??

????return?0;??

}??

?

這里我們需要明白中斷urb和控制urb需要分配不同的urb結構體，同時在提交urb之前，需要填充的內容也不同，中斷urb填充的是緩沖區和中斷處理函數，控制urb填充的是控制請求描述符與回調函數。

設置控制請求的格式。cr是struct usb_ctrlrequest結構的指針，USB協議中規定一個控制請求的格式為一個8個字節的數據包，其定義如下

?

[cpp]?view plaincopy

/**?

?*?struct?usb_ctrlrequest?-?SETUP?data?for?a?USB?device?control?request?

?*?@bRequestType:?matches?the?USB?bmRequestType?field?

?*?@bRequest:?matches?the?USB?bRequest?field?

?*?@wValue:?matches?the?USB?wValue?field?(le16?byte?order)?

?*?@wIndex:?matches?the?USB?wIndex?field?(le16?byte?order)?

?*?@wLength:?matches?the?USB?wLength?field?(le16?byte?order)?

?*?

?*?This?structure?is?used?to?send?control?requests?to?a?USB?device.??It?matches?

?*?the?different?fields?of?the?USB?2.0?Spec?section?9.3,?table?9-2.??See?the?

?*?USB?spec?for?a?fuller?description?of?the?different?fields,?and?what?they?are?

?*?used?for.?

?*?

?*?Note?that?the?driver?for?any?interface?can?issue?control?requests.?

?*?For?most?devices,?interfaces?don't?coordinate?with?each?other,?so?

?*?such?requests?may?be?made?at?any?time.?

?*/??

struct?usb_ctrlrequest?{??

????__u8?bRequestType;??//設定傳輸方向、請求類型等??

????__u8?bRequest;??????//指定哪個請求，可以是規定的標準值也可以是廠家定義的值??

????__le16?wValue;??????//即將寫到寄存器的數據??

????__le16?wIndex;??????//接口數量，也就是寄存器的偏移地址??

????__le16?wLength;?????//數據傳輸階段傳輸多少個字節??

}?__attribute__?((packed));??

?

USB協議中規定，所有的USB設備都會響應主機的一些請求，這些請求來自USB主機控制器，主機控制器通過設備的默認控制管道發出這些請求。默認的管道為0號端口對應的那個管道。

同樣這個input設備首先由用戶層調用open函數，所以先看看input中定義的open

?

[cpp]?view plaincopy

static?int?usb_kbd_open(struct?input_dev?*dev)??

{??

????struct?usb_kbd?*kbd?=?input_get_drvdata(dev);??

??

????kbd->irq->dev?=?kbd->usbdev;??

????if?(usb_submit_urb(kbd->irq,?GFP_KERNEL))??

????????return?-EIO;??

??

????return?0;??

}??

因為這個驅動里面有一個中斷urb一個控制urb，我們先看中斷urb的處理流程。中斷urb在input的open中被提交后，當USB core處理完畢，會通知這個USB設備驅動，然后執行回調函數，也就是中斷處理函數usb_kbd_irq

?

?

[cpp]?view plaincopy

static?void?usb_kbd_irq(struct?urb?*urb)??

{??

????struct?usb_kbd?*kbd?=?urb->context;??

????int?i;??

??

????switch?(urb->status)?{??

????case?0:?????????/*?success?*/??

????????break;??

????case?-ECONNRESET:???/*?unlink?*/??

????case?-ENOENT:??

????case?-ESHUTDOWN:??

????????return;??

????/*?-EPIPE:??should?clear?the?halt?*/??

????default:????????/*?error?*/??

????????goto?resubmit;??

????}??

????//報告usb_kbd_keycode[224..231]8按鍵狀態??

????//KEY_LEFTCTRL,KEY_LEFTSHIFT,KEY_LEFTALT,KEY_LEFTMETA,??

????//KEY_RIGHTCTRL,KEY_RIGHTSHIFT,KEY_RIGHTALT,KEY_RIGHTMETA??

????for?(i?=?0;?i?<?8;?i++)??

????????input_report_key(kbd->dev,?usb_kbd_keycode[i?+?224],?(kbd->new[0]?>>?i)?&?1);??

????//若同時只按下1個按鍵則在第[2]個字節,若同時有兩個按鍵則第二個在第[3]字節，類推最多可有6個按鍵同時按下??

????for?(i?=?2;?i?<?8;?i++)?{??

????????//獲取鍵盤離開的中斷??

????????????//同時沒有該KEY的按下狀態??

????????if?(kbd->old[i]?>?3?&&?memscan(kbd->new?+?2,?kbd->old[i],?6)?==?kbd->new?+?8)?{??

????????????if?(usb_kbd_keycode[kbd->old[i]])??

????????????????input_report_key(kbd->dev,?usb_kbd_keycode[kbd->old[i]],?0);??

????????????else??

????????????????hid_info(urb->dev,??

?????????????????????"Unknown?key?(scancode?%#x)?released.\n",??

?????????????????????kbd->old[i]);??

????????}??

????????//獲取鍵盤按下的中斷??

????????????//同時沒有該KEY的離開狀態??

????????if?(kbd->new[i]?>?3?&&?memscan(kbd->old?+?2,?kbd->new[i],?6)?==?kbd->old?+?8)?{??

????????????if?(usb_kbd_keycode[kbd->new[i]])??

????????????????input_report_key(kbd->dev,?usb_kbd_keycode[kbd->new[i]],?1);??

????????????else??

????????????????hid_info(urb->dev,??

?????????????????????"Unknown?key?(scancode?%#x)?released.\n",??

?????????????????????kbd->new[i]);??

????????}??

????}??

??

????input_sync(kbd->dev);????????????//同步設備,告知事件的接收者驅動已經發出了一個完整的報告??

??

????memcpy(kbd->old,?kbd->new,?8);????//防止未松開時被當成新的按鍵處理??

??

resubmit:??

????i?=?usb_submit_urb?(urb,?GFP_ATOMIC);??

????if?(i)??

????????hid_err(urb->dev,?"can't?resubmit?intr,?%s-%s/input0,?status?%d",??

????????????kbd->usbdev->bus->bus_name,??

????????????kbd->usbdev->devpath,?i);??

}??

?

這個就是中斷urb的處理流程，跟前面講的的USB鼠標中斷處理流程類似。好了，我們再來看看剩下的控制urb處理流程吧。

我們有個疑問，我們知道在probe中，我們填充了中斷urb和控制urb，但是在input的open中，我們只提交了中斷urb，那么控制urb什么時候提交呢？

我們知道對于input子系統，如果有事件被響應，我們會調用事件處理層的event函數，而該函數最終調用的是input下的event。所以，對于input設備，我們在USB鍵盤驅動中只設置了支持LED選項，也就是ledbit項，這是怎么回事呢？剛才我們分析的那個中斷urb其實跟這個 input基本沒啥關系，中斷urb并不是像講鍵盤input實現的那樣屬于input下的中斷。我們在USB鍵盤驅動中的input子系統中只設計了 LED選項，那么當input子系統有按鍵選項的時候必然會使得內核調用調用事件處理層的event函數，最終調用input下的event。好了，那我們來看看input下的event干了些什么。

[cpp]?view plaincopy

static?int?usb_kbd_event(struct?input_dev?*dev,?unsigned?int?type,??

?????????????unsigned?int?code,?int?value)??

{??

????struct?usb_kbd?*kbd?=?input_get_drvdata(dev);??

??

????if?(type?!=?EV_LED)//不支持LED事件??

????????return?-1;??

????//獲取指示燈的目標狀態??

????kbd->newleds?=?(!!test_bit(LED_KANA,????dev->led)?<<?3)?|?(!!test_bit(LED_COMPOSE,?dev->led)?<<?3)?|??

???????????????(!!test_bit(LED_SCROLLL,?dev->led)?<<?2)?|?(!!test_bit(LED_CAPSL,???dev->led)?<<?1)?|??

???????????????(!!test_bit(LED_NUML,????dev->led));??

??

????if?(kbd->led->status?==?-EINPROGRESS)??

????????return?0;??

????//指示燈狀態已經是目標狀態則不需要再做任何操作??

????if?(*(kbd->leds)?==?kbd->newleds)??

????????return?0;??

??

????*(kbd->leds)?=?kbd->newleds;??

????kbd->led->dev?=?kbd->usbdev;??

????if?(usb_submit_urb(kbd->led,?GFP_ATOMIC))??

????????pr_err("usb_submit_urb(leds)?failed\n");??

????//提交控制urb??

????return?0;??

}??

當在input的event里提交了控制urb后，經過URB處理流程，最后返回給USB設備驅動的回調函數，也就是在probe中定義的usb_kbd_led

?

[cpp]?view plaincopy

static?void?usb_kbd_led(struct?urb?*urb)??

{??

????struct?usb_kbd?*kbd?=?urb->context;??

??

????if?(urb->status)??

????????hid_warn(urb->dev,?"led?urb?status?%d?received\n",??

?????????????urb->status);??

??

????if?(*(kbd->leds)?==?kbd->newleds)??

????????return;??

??

????*(kbd->leds)?=?kbd->newleds;??

????kbd->led->dev?=?kbd->usbdev;??

????if?(usb_submit_urb(kbd->led,?GFP_ATOMIC))??

????????hid_err(urb->dev,?"usb_submit_urb(leds)?failed\n");??

}??

?

總結下，我們的控制urb走的是先由input的event提交，觸發后由控制urb的回調函數再次提交。好了，通過USB鼠標，我們已經知道了控制urb和中斷urb的設計和處理流程。

轉載于:https://www.cnblogs.com/MMLoveMeMM/articles/4105665.html

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