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原文地址：http://blog.csdn.net/chenjin_zhong/article/details/6329316

1.Linux usb裝置驅動框架

USB是通用序列匯流排的總稱，Linux核心幾乎支援所有的usb裝置，包括鍵盤，滑鼠，印表機，modem,掃描器。Linux的usb驅動分為主機驅動與gadget驅動。前者是裝置連線到計算機上，通過主機驅動掃描usb裝置，控制所連線的裝置。而gadget驅動一般用於嵌入式裝置，gadget驅動用於控制嵌入式裝置。Linux的usb驅動兩種型別圖如下:

  

左側是usb的主機驅動，右側是gadget驅動。下面著重介紹一下usb的主機驅動:

(1)usb主機控制器-直接與硬體裝置互動。

(2)usb core-向usb裝置驅動提供API以及usb主機控制器驅動的程式。使用usb core所提供的函式，巨集來完成資料處理的功能。

(3)usb裝置驅動，即usb介面驅動，一般所說的usb驅動指的是usb介面驅動

  

2.usb系統的組成部分

usb系統一般由三個部分組成，主機，一個或多個usb hub,以及與之些hub連線的usb裝置。

(1)主機

在任何的usb系統中僅有一個主機，主機系統中的usb介面即上圖中的主機控制器，主機控制器可由硬體，軟體或韌體組成。主機主要負責:

a.檢測usb裝置的連線與拆除

b.管理主機與usb裝置之間的控制流

c.管理主機與usb裝置之間的資料流

d.收集狀態和活動的統計

e.為連線的usb裝置提供電源

 

 

(2)usb裝置

所有的usb裝置都是通過地址來存取的，這個地址在連線或列舉時分配。usb裝置對usb系統來說是端點的集合，一組端點實現一個介面。裝置端點是usb裝置中唯一可定址的部分。它是主機與裝置之間通訊流的結束點。一系列的相互獨立的端點構成了usb邏輯裝置。每個端點支援流進裝置或者是流出裝置。

主機與裝置端點上的usb資料傳輸是通過管道的方式。

 

(3)hub

所有的usb device都連線在hub埠上。

 

 

 

3. usb傳輸模式

 

(1)控制傳輸模式(Control)

控制傳輸模式支援雙向傳輸，用來處理從usb主機埠到usb裝置埠的資料傳輸，用於控制指令，裝置狀態查詢以及確認命令。

 

(2)等時傳輸方式(lsochronous)

等時傳輸是一種週期性的連續性的意向傳輸模式，通常用於對時間有著密切關係的資訊的傳輸，對準確性要求不高，但對時間要求極為敏感的裝置，如視訊，音訊的傳輸。

 

(3)中斷傳輸模式(Interrupt)

中斷傳輸模式用於非週期性的，自然發生的，資料量小的傳輸，資料傳輸的方向是從裝置到主機。如usb鍵盤和滑鼠

 

(4)批量傳輸模式(bulk)

批量傳輸模式是一種單向的，用於大量資料傳輸的模式，該方式用來傳輸正確無誤的資料。通常印表機，掃描器，數碼相機以這種方式與主機連線

 

 

4. usb裝置組成

(1)一個usb裝置由可以有一個或多個配置

(2)一個配置通常可以有一個或多個介面

(3)一個介面通常可以有一個或多個端點

通常所盡的usb裝置驅動是指介面驅動，即一個介面對應一個驅動。

所以Linux usb裝置有四大描述符，分別為裝置描述符，配置描述符，介面描述符，端點描述符。下面看一個這幾個描述符的相關資料結構:

 

 

struct usb_device_descriptor

{
      _u8 bLength;  //此描述符的位元組數
      _u8  bDescriptorType; //描述符的種類為裝置
      _u16 bcdUSB;  //此裝置與描述符相容的usb裝置說明版本號(BCD碼)
      _u8   bDeviceClass; //裝置類碼
      _u8   bDeviceSubClass; //裝置子類碼
      _u8   bDeviceProtocol; //協議碼
      _u8   bMaxPacketSize0; //端點0的最大包大小
      _u16 idVendor; //廠商標誌
      _u16  idProduct; //產品標誌
      _u16 bcdDevice; //裝置發行號
      _u8   iManufacturer; //描述廠商的字串索引

      _u8   iProduct; //描述產品資訊的字串索引

      _u8  iSerialNumber; //描述裝置序列號資訊的字串索引
      _u8  bNumConfigurations;//此裝置支援的配置數

  }_attribute_ ((packed));

 

裝置類碼的典型值如下:

 

#define USB_CLASS_PER_INTERFACE 0

#define USB_CLAS_AUDIO 1     //聲音裝置

#define USB_CLASS_COMM 2   // 調變解調器，網絡卡，ISDN連線

#define USB_CLASS_HID  3    //HID裝置，如滑鼠，鍵盤

#define USB_CLASS_PHYSICAL 5 //物理裝置

#define USB_CLASS_STILL_IMAGE 6 //靜止影象捕捉裝置

#define USB_CLASS_PRINTER 7//印表機

#define USB_CLASS_MASS_STORAGE //8 批量儲存裝置

#define USB_CLASS_HUB 9   //USB HUBS

#define USB_CLASS_CSCID 0x0B  //智慧卡

#define USB_CLASS_VIDEO 0X0E //視訊裝置，如網路攝像頭

#define USB_CLASS_VENDOR_SPEC 0xFF //廠商自定義的裝置

 

  struct usb_config_descriptor{

 

 _u8 bLength ;//此描述符的位元組數

_u8 bDescriptorType; //配置描述符型別

_u16 wTotalLength; //此配置資訊的總長(包括配置，介面，端點和裝置型別及廠商定義的描述符)

_u8 bNumInterfaces; //此配置所支援的介面數

_u8 bConfigurationValue ;//在setConfiguration()請求中用作引數來選定此配置

_u8 iConfiguration; //描述此配置的字串描述符索引

_u8 bmAttributes; //電源配置特性

_u8 bMaxpowe;r //此配置下的匯流排電源耗電量

}_attribute_ ((packed));

 

 

配置描述符給出了usb裝置配置資訊，以及此配置下的介面數。每個介面可能的獨立操作。

 

 

 

struct usb_interface_descriptor{

 

_u8 bLength ;//此描述符的位元組數

_u8 bDescriptorType;//介面描述符類

_u8 bInterfacNumber;//介面號，當前配置所支援的介面陣列索引,從0開始

_u8 bNumEndpoints ;//此介面用的端點數量，如果是0,說明此介面只有預設控制通道

_u8 bAlernateSetting;//可選裝置的索引值

_u8 bInterfaceClass;// 類值,0值作為將來保留使用如果是0FFH,此介面由廠商說明

_u8 bInterfaceSubClass;//子類碼

_u8 bInterfaceProtocol;//協議碼

_u8 iInterface;//描述此介面的字串描述符索引

 

}_attribute_ ((packed));

 

struct usb_endpoint_descriptor{

_u8 bLength ;//此描述符的位元組數

_u8 bDescriptorType;//端點描述符類

_u8 bEndpointAddress;此描述符所描述的端點的地址

_u8 bmAtrributes;//所指定的端點的特性，如果是00=控制傳送,01=等時傳送,10=批傳送,11=中斷傳送

_u8 wMaxPacketSize;//當前配置下端點能夠傳送與接收的最大資料包大小

_u8 bInterval;//輪詢資料傳送端點的時間間隙

_u8 bRefresh

_u8 bSynchAddress

}_attribute_ ((packed));

 

以上給出了usb中的裝置描述符，配置描述符，介面描述符和端點描述符。

 

 

5. usb裝置驅動的幾個重要的資料結構

 

usb_driver,usb_device,usb_bus.

 

 

/**
788* stru ctusb_driver - identifiesU SB interface driver tou sbcore
789* @name: The driver name shou ld beu niqu e amongU SB drivers,
790*      and shou ld normally be the same as the modu le name.
791* @probe: Called to see if the driver is willing to manage a particu lar
792*      interface on a device.  If it is, probe retu rns zero andu ses
793*     u sb_set_intfdata() to associate driver-specific data with the
794*      interface.  It may alsou seu sb_set_interface() to specify the
795*      appropriate altsetting.  Ifu nwilling to manage the interface,
796*      retu rn -ENODEV, if genu ine IO errors occu red, an appropriate
797*      negative errno valu e.
798* @disconnect: Called when the interface is no longer accessible,u su ally
799*      becau se its device has been (or is being) disconnected or the
800*      driver modu le is beingu nloaded.
801* @u nlocked_ioctl:U sed for drivers that want to talk tou serspace throu gh
802*      the "u sbfs" filesystem.  This lets devices provide ways to
803*      expose information tou ser space regardless of where they
804*      do (or don't) showu p otherwise in the filesystem.
805* @su spend: Called when the device is going to be su spended by the system.
806* @resu me: Called when the device is being resu med by the system.
807* @reset_resu me: Called when the su spended device has been reset instead
808*      of being resu med.
809* @pre_reset: Called byu sb_reset_device() when the device
810*      is abou t to be reset.
811* @post_reset: Called byu sb_reset_device() after the device
812*      has been reset
813* @id_table:U SB driversu se ID table to su pport hotplu gging.
814*      Export this with MODU LE_DEVICE_TABLE(u sb,...).  This mu st be set
815*      or you r driver's probe fu nction will never get called.
816* @dynids:u sed internally to hold the list of dynamically added device
817*      ids for this driver.
818* @drvwrap: Driver-model core stru ctu re wrapper.
819* @no_dynamic_id: if set to 1, theU SB core will not allow dynamic ids to be
820*      added to this driver by preventing the sysfs file from being created.
821* @su pports_au tosu spend: if set to 0, theU SB core will not allow au tosu spend
822*      for interfaces bou nd to this driver.
823* @soft_u nbind: if set to 1, theU SB core will not killU RBs and disable
824*      endpoints before calling the driver's disconnect method.
825*
826*U SB interface drivers mu st provide a name, probe() and disconnect()
827* methods, and an id_table.  Other driver fields are optional.
828*
829* The id_table isu sed in hotplu gging.  It holds a set of descriptors,
830* and specialized data may be associated with each entry.  That table
831* isu sed by bothu ser and kernel mode hotplu gging su pport.
832*
833* The probe() and disconnect() methods are called in a context where
834* they can sleep, bu t they shou ld avoid abu sing the privilege.  Most
835* work to connect to a device shou ld be done when the device is opened,
836* andu ndone at the last close.  The disconnect code needs to address
837* concu rrency issu es with respect to open() and close() methods, as
838* well as forcing all pending I/O requ ests to complete (byu nlinking
839* them as necessary, and blockingu ntil theu nlinks complete).
840*/
841stru ctusb_driver{
842         const char *name;
843
844         int (*probe) (stru ct u sb_interface*intf,
845                       const stru ctu sb_device_id*id);
846
847         void (*disconnect) (stru ct u sb_interface*intf);
848
849         int (*u nlocked_ioctl) (stru ctu sb_interface*intf,u nsigned intcode,
850                         void *bu f);
851
852         int (*su spend) (stru ct u sb_interface *intf,pm_message_tmessage);
853         int (*resu me) (stru ct u sb_interface *intf);
854         int (*reset_resu me)(stru ctu sb_interface*intf);
855
856         int (*pre_reset)(stru ct u sb_interface*intf);
857         int (*post_reset)(stru ctu sb_interface*intf);
858
859         const stru ctu sb_device_id*id_table;
860
861         stru ctu sb_dynidsdynids;
862         stru ctu sbdrv_wrapdrvwrap;
863        u nsigned int no_dynamic_id:1;
864        u nsigned int su pports_au tosu spend:1;
865        u nsigned int soft_u nbind:1;
866};

 

usb_driver中的probe函式掃描連線到主機上的usb裝置，並且註冊usb介面驅動。

 

disconnect函式是當usb裝置移除時呼叫。

 

 

/*
310* Allocated per bu s (tree of devices) we have:
311*/
312stru ctu sb_bu s {
313         stru ctdevice *controller ;     /* host/master side hardware */
314         int bu snu m;                    /* Bu s nu mber (in order of reg) */
315         const char *bu s_name;          /* stable id (PCI slot_name etc) */
316        u 8u ses_dma;                   /* Does the host controlleru se DMA? */
317        u 8u ses_pio_for_control;       /*
318                                         * Does the host controlleru se PIO
319                                         * for control transfers?
320                                         */
321        u 8 otg_port;                   /* 0, or nu mber of OTG/HNP port */
322        u nsigned is_b_host:1;          /* tru e du ring some HNP roleswitches */
323        u nsigned b_hnp_enable:1;       /* OTG: did A-Host enable HNP? */
324        u nsignedsg_tablesize ;         /* 0 or largest nu mber of sg list entries */
325
326         int devnu m_next;               /* Next open device nu mber in
327                                         * rou nd-robin allocation */
328
329         stru ctu sb_devmap  devmap;      /* device address allocation map */
330         stru ctusb_device * root_hu b;   /* Root hu b */
331         stru ctu sb_bu s *hs_companion;  /* Companion EHCI bu s, if any */
332         stru ctlist_head bu s_list;     /* list of bu sses */
333
334         int bandwidth_allocated;       /* on this bu s: how mu ch of the time
335                                         * reserved for periodic (intr/iso)
336                                         * requ ests isu sed, on average?
337                                         *U nits: microseconds/frame.
338                                         * Limits: Fu ll/low speed reserve 90%,
339                                         * while high speed reserves 80%.
340                                         */
341         int bandwidth_int_reqs;        /* nu mber of Interru pt requ ests */
342         int bandwidth_isoc_reqs;       /* nu mber of Isoc. requ ests */
343
344#ifdef CONFIG_USB_DEVICE FS
345         stru ctdentry *u sbfs_dentry;   /*u sbfs dentry entry for the bu s */
346#endif
347
348#ifdefined (CONFIG_U SB_MON) ||defined(CONFIG_U SB_MON_MODU LE)
349         stru ctmon_bu s *mon_bu s ;       /* non-nu ll when associated */
350         int monitored;                 /* non-zero when monitored */
351#endif
352};
353

 

 

**
370* stru ctusb_device - kernel's representation of aU SB device
371* @devnu m: device nu mber; address on aU SB bu s
372* @devpath: device ID string foru se in messages (e.g., /port/...)
373* @rou te: tree topology hex string foru se with xHCI
374* @state: device state: configu red, not attached, etc.
375* @speed: device speed: high/fu ll/low (or error)
376* @tt: Transaction Translator info;u sed with low/fu ll speed dev, highspeed hu b
377* @ttport: device port on that tt hu b
378* @toggle: one bit for each endpoint, with ([0] = IN, [1] = OU T) endpoints
379* @parent: ou r hu b,u nless we're the root
380* @bu s: bu s we're part of
381* @ep0: endpoint 0 data (defau lt control pipe)
382* @dev: generic device interface
383* @descriptor:U SB device descriptor
384* @config: all of the device's configs
385* @actconfig: the active configu ration
386* @ep_in: array of IN endpoints
387* @ep_ou t: array of OU T endpoints
388* @rawdescriptors: raw descriptors for each config
389* @bu s_mA: Cu rrent available from the bu s
390* @portnu m: parent port nu mber (origin 1)
391* @level: nu mber ofU SB hu b ancestors
392* @can_su bmit:U RBs may be su bmitted
393* @persist_enabled: U SB_PERSIST enabled for this device
394* @have_langid: whether string_langid is valid
395* @au thorized: policy has said we canu se it;
396*      (u ser space) policy determines if we au thorize this device to be
397*     u sed or not. By defau lt, wiredU SB devices are au thorized.
398*      WU SB devices are not,u ntil we au thorize them fromu ser space.
399*      FIXME -- complete doc
400* @au thenticated: Crypto au thentication passed
401* @wu sb: device is WirelessU SB
402* @string_langid: langu age ID for strings
403* @produ ct: iProdu ct string, if present (static)
404* @manu factu rer: iManu factu rer string, if present (static)
405* @serial: iSerialNu mber string, if present (static)
406* @filelist:u sbfs files that are open to this device
407* @u sb_classdev:U SB class device that was created foru sbfs device
408*      access fromu serspace
409* @u sbfs_dentry:u sbfs dentry entry for the device
410* @maxchild: nu mber of ports if hu b
411* @children: child devices -U SB devices that are attached to this hu b
412* @qu irks: qu irks of the whole device
413* @u rbnu m: nu mber ofU RBs su bmitted for the whole device
414* @active_du ration: total time device is not su spended
415* @connect_time: time device was first connected
416* @do_remote_wakeu p:  remote wakeu p shou ld be enabled
417* @reset_resu me: needs reset instead of resu me
418* @wu sb_dev: if this is a WirelessU SB device, link to the WU SB
419*      specific data for the device.
420* @slot_id: Slot ID assigned by xHCI
421*
422* Notes:
423*U sbcore drivers shou ld not setu sbdev->state directly.  Insteadu se
424*u sb_set_device_state().
425*/
426stru ctusb_device{
427         int             devnu m;
428         char            devpath[16];
429        u 32             rou te;
430         enu musb_device _state  state;
431         enu musb_device _speed  speed;
432
433         stru ctu sb_tt   *tt;
434         int             ttport;
435
436        u nsigned inttoggle[2];
437
438         stru ctusb_device*parent;
439         stru ctu sb_bu s*bu s;
440         stru ctu sb_host_endpointep0;
441
442         stru ctdevicedev;
443
444         stru ctusb_device _descriptordescriptor;
445         stru ctu sb_host_config*config;
446
447         stru ctu sb_host_config*actconfig;
448         stru ctu sb_host_endpoint*ep_in[16];
449         stru ctu sb_host_endpoint*ep_ou t[16];
450

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