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USB NCM usbnet 枚舉流程代碼分析
2021-10-20 10:31:48


USB NCM usbnet 枚舉流程代碼分析

一、cdc_ncm.c

在linux 驅動中，CDC NCM的驅動位于: ??kerneldrivers etusbcdc_ncm.c??

static struct usb_driver cdc_ncm_driver = {
  .name = "cdc_ncm",
  .id_table = cdc_devs,
  .probe = usbnet_probe,
  .disconnect = usbnet_disconnect,
  .suspend = usbnet_suspend,
  .resume = usbnet_resume,
  .reset_resume = usbnet_resume,
  .supports_autosuspend = 1,
  .disable_hub_initiated_lpm = 1,
};

module_usb_driver(cdc_ncm_driver);

在結構體??cdc_ncm_driver??中，比較重要的是??id_table??，??probe??這兩個，

在??id_table?? 中定義了所有符合??cdc_ncm??設備的 ??idVendor??號，當??linux?? 枚舉時檢測到USB設備的??idVendor??在這個??id_table??中時，就會調用??usbnet_probe??進行起網操作。


1.1 struct usb_device_id結構體

在分析??cdc_ncm??的??id_table??之前，我們先來看下??usb_device_id?? 結構體是如何定義的：

# kernelincludelinuxmod_devicetable.h
struct usb_device_id {
/* which fields to match against? */
__u16   match_flags;      //說明使用哪種匹配方式

/* Used for product specific matches; range is inclusive */
__u16   idVendor;       //供應商ID  
__u16   idProduct;        //產品ID 
__u16   bcdDevice_lo;
__u16   bcdDevice_hi;

/* Used for device class matches */
__u8    bDeviceClass;     //設備類型  
__u8    bDeviceSubClass;    //設備子類型 
__u8    bDeviceProtocol;    //協議 

/* Used for interface class matches */
__u8    bInterfaceClass;    //接口類 
__u8    bInterfaceSubClass;   //接口子類  
__u8    bInterfaceProtocol;   //接口協議 

/* Used for vendor-specific interface matches */
__u8    bInterfaceNumber;

/* not matched against */
kernel_ulong_t  driver_info
__attribute__((aligned(sizeof(kernel_ulong_t)))); // NCM 驅動結構體，其中包含了收發(fā)包的函數等
};

結合結構體定義，我們來看下??cdc_ncm??的??id_table??：

static const struct usb_device_id cdc_devs[] = {
// 愛立信 F5521gw USB網卡
/* Ericsson MBM devices like F5521gw */
  { .match_flags = USB_DEVICE_ID_MATCH_INT_INFO | USB_DEVICE_ID_MATCH_VENDOR, 
//匹配方式：CLASS（設備類）、SUBCLASS（子類）、PROTOCOL（設備協議）
    .idVendor = 0x0bdb,                           //供應商ID： 0x0bdb
    .bInterfaceClass = USB_CLASS_COMM,                    //設備類型： 網卡類
    .bInterfaceSubClass = USB_CDC_SUBCLASS_NCM,               //設備子類型：NCM
    .bInterfaceProtocol = USB_CDC_PROTO_NONE,                 //設備協議:  無
    .driver_info = (unsigned long) &wwan_info,                // NCM 驅動結構體，其中包含了收發(fā)包的函數等
  },

/* DW5812 LTE Verizon Mobile Broadband Card Unlike DW5550 this device requires FLAG_NOARP */
  { USB_DEVICE_AND_INTERFACE_INFO(0x413c, 0x81bb,
USB_CLASS_COMM,
USB_CDC_SUBCLASS_NCM, USB_CDC_PROTO_NONE),
    .driver_info = (unsigned long)&wwan_noarp_info,
  },

/* DW5813 LTE AT&T Mobile Broadband Card Unlike DW5550 this device requires FLAG_NOARP */
  { USB_DEVICE_AND_INTERFACE_INFO(0x413c, 0x81bc,
USB_CLASS_COMM,
USB_CDC_SUBCLASS_NCM, USB_CDC_PROTO_NONE),
    .driver_info = (unsigned long)&wwan_noarp_info,
  },

/* Dell branded MBM devices like DW5550 */
  { .match_flags = USB_DEVICE_ID_MATCH_INT_INFO | USB_DEVICE_ID_MATCH_VENDOR,
    .idVendor = 0x413c,
    .bInterfaceClass = USB_CLASS_COMM,
    .bInterfaceSubClass = USB_CDC_SUBCLASS_NCM,
    .bInterfaceProtocol = USB_CDC_PROTO_NONE,
    .driver_info = (unsigned long) &wwan_info,
  },

/* Toshiba branded MBM devices */
  { .match_flags = USB_DEVICE_ID_MATCH_INT_INFO | USB_DEVICE_ID_MATCH_VENDOR,
    .idVendor = 0x0930,
    .bInterfaceClass = USB_CLASS_COMM,
    .bInterfaceSubClass = USB_CDC_SUBCLASS_NCM,
    .bInterfaceProtocol = USB_CDC_PROTO_NONE,
    .driver_info = (unsigned long) &wwan_info,
  },

/* tag Huawei devices as wwan */
  { USB_VENDOR_AND_INTERFACE_INFO(0x12d1,
USB_CLASS_COMM,
USB_CDC_SUBCLASS_NCM,
USB_CDC_PROTO_NONE),
    .driver_info = (unsigned long)&wwan_info,
  },

/* Infineon(now Intel) HSPA Modem platform */
  { USB_DEVICE_AND_INTERFACE_INFO(0x1519, 0x0443,
USB_CLASS_COMM,
USB_CDC_SUBCLASS_NCM, USB_CDC_PROTO_NONE),
    .driver_info = (unsigned long)&wwan_noarp_info,
  },

/* Generic CDC-NCM devices */
  { USB_INTERFACE_INFO(USB_CLASS_COMM,
USB_CDC_SUBCLASS_NCM, USB_CDC_PROTO_NONE),
    .driver_info = (unsigned long)&cdc_ncm_info,
  }
};
MODULE_DEVICE_TABLE(usb, cdc_devs);

1.1.1 match_flags 設備類型

所有的??match_flags??定義在??mod_devicetable.h?? 中：

# kernelincludelinuxmod_devicetable.h
/* Some useful macros to use to create struct usb_device_id */
#define USB_DEVICE_ID_MATCH_VENDOR      0x0001
#define USB_DEVICE_ID_MATCH_PRODUCT     0x0002
#define USB_DEVICE_ID_MATCH_DEV_LO      0x0004
#define USB_DEVICE_ID_MATCH_DEV_HI      0x0008
#define USB_DEVICE_ID_MATCH_DEV_CLASS   0x0010
#define USB_DEVICE_ID_MATCH_DEV_SUBCLASS  0x0020
#define USB_DEVICE_ID_MATCH_DEV_PROTOCOL  0x0040
#define USB_DEVICE_ID_MATCH_INT_CLASS   0x0080
#define USB_DEVICE_ID_MATCH_INT_SUBCLASS  0x0100
#define USB_DEVICE_ID_MATCH_INT_PROTOCOL  0x0200
#define USB_DEVICE_ID_MATCH_INT_NUMBER    0x0400

1.1.2 bInterfaceClass 接口類

# kernelincludeuapilinuxusbch9.h

/* Device and/or Interface Class codes
* as found in bDeviceClass or bInterfaceClass
* and defined by www.usb.org documents */
#define USB_CLASS_PER_INTERFACE   0 /* for DeviceClass */
#define USB_CLASS_AUDIO     1         //聲音設備
#define USB_CLASS_COMM      2         //調制解調器，網卡，ISDN連接
#define USB_CLASS_HID     3         //HID設備，如鼠標，鍵盤
#define USB_CLASS_PHYSICAL    5         //物理設備
#define USB_CLASS_STILL_IMAGE 6         //靜止圖像捕捉設備
#define USB_CLASS_PRINTER   7         //打印機
#define USB_CLASS_MASS_STORAGE  8         //批量存儲設備
#define USB_CLASS_HUB     9         //USB HUBS
#define USB_CLASS_CDC_DATA    0x0a        
#define USB_CLASS_CSCID     0x0b  /* chip+ smart card */    //智能卡
#define USB_CLASS_CONTENT_SEC   0x0d  /* content security */
#define USB_CLASS_VIDEO     0x0e        //視頻設備，如網絡攝像頭
#define USB_CLASS_WIRELESS_CONTROLLER 0xe0    //網絡控制設備
#define USB_CLASS_MISC      0xef        //雜項設備
#define USB_CLASS_APP_SPEC    0xfe
#define USB_CLASS_VENDOR_SPEC   0xff      //廠商自定義的設備

#define USB_SUBCLASS_VENDOR_SPEC  0xff

wait…

本文摘自 ：https://blog.51cto.com/c

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