理論:
對于USB接口的設(shè)備，現(xiàn)在越來越多了。本篇我們就通過獲取一個USB掃描儀設(shè)備中的序列號，來介紹如何獲取usb設(shè)備的一些硬件信息。對于usb設(shè)備都是采用HCD0,HCD1,HCD2,HCD3等符號描述的。如下圖：
因此，有了這個名字，我們就可以使用CreateFile來打開usb設(shè)備。然后使用DeviceIoControl函數(shù)與usb設(shè)備通訊了。
HCD是host controller driver的簡寫。需要了解詳情的，還要仔細的閱讀usb協(xié)議。
usb的通訊基本步驟如下圖所示：
基本步驟：
1）打開HCD%X
2) 得到上面的USB root hub
3) 遍歷usb root hub上連接的usb 設(shè)備。獲取信息
4）如果有多個usb口，循環(huán)前3步。
下面介紹通訊用的幾個IOCTL:1)
USB_HCD_DRIVERKEY_NAME ,用于獲取USB設(shè)備驅(qū)動在注冊表中的鍵名。相應的一個結(jié)構(gòu)體是：
typedef struct _USB_HCD_DRIVERKEY_NAME
{
ULONG ActualLength;
WCHAR DriverKeyName[1];
} USB_HCD_DRIVERKEY_NAME, *PUSB_HCD_DRIVERKEY_NAME;2）
IOCTL_USB_GET_ROOT_HUB_NAME，用于獲取root hub 鍵名。使用的結(jié)構(gòu)體，跟上面一樣。
typedef struct _USB_ROOT_HUB_NAME
{
ULONG ActualLength;
WCHAR RootHubName[1];
} USB_ROOT_HUB_NAME, *PUSB_ROOT_HUB_NAME;
3）IOCTL_USB_GET_NODE_INFORMATION，用于獲取連接在root hub上的節(jié)點設(shè)備信息。也就是我們接在usb口上的所有usb設(shè)備的信息，對應的結(jié)構(gòu)體：
typedef struct _USB_NODE_INFORMATION
{
USB_HUB_NODE NodeType;
union {
USB_HUB_INFORMATION HubInformation;
USB_MI_PARENT_INFORMATION MiParentInformation;
} u;
} USB_NODE_INFORMATION, *PUSB_NODE_INFORMATION;
typedef struct _USB_MI_PARENT_INFORMATION
{
ULONG NumberOfInterfaces;
} USB_MI_PARENT_INFORMATION, *PUSB_MI_PARENT_INFORMATION;
typedef struct _USB_HUB_INFORMATION
{
USB_HUB_DESCRIPTOR HubDescriptor;
BOOLEAN HubIsBusPowered;
} USB_HUB_INFORMATION, *PUSB_HUB_INFORMATION;
typedef struct _USB_HUB_DESCRIPTOR
{
UCHAR bDescriptorLength; // Length of this descriptor
UCHAR bDescriptorType; // Hub configuration type
UCHAR bNumberOfPorts; // number of ports on this hub
USHORT wHubCharacteristics; // Hub Charateristics
UCHAR bPowerOnToPowerGood; // port power on till power good in 2ms
UCHAR bHubControlCurrent; // max current in mA
//
// room for 255 ports power control and removable bitmask
UCHAR bRemoveAndPowerMask[64];
} USB_HUB_DESCRIPTOR, *PUSB_HUB_DESCRIPTOR;
4) IOCTL_USB_GET_NODE_CONNECTION_INFORMATION, 用于獲取接在usb口上的單個usb設(shè)備的信息，對應的結(jié)構(gòu)體：
typedef struct _USB_NODE_CONNECTION_INFORMATION
{
ULONG ConnectionIndex;
USB_DEVICE_DESCRIPTOR DeviceDescriptor;
UCHAR CurrentConfigurationValue;
BOOLEAN LowSpeed;
BOOLEAN DeviceIsHub;
USHORT DeviceAddress;
ULONG NumberOfOpenPipes;
USB_CONNECTION_STATUS ConnectionStatus;
USB_PIPE_INFO PipeList[0];
} USB_NODE_CONNECTION_INFORMATION, *PUSB_NODE_CONNECTION_INFORMATION;
4）IOCTL_USB_GET_DESCRIPTOR_FROM_NODE_CONNECTION， 用于獲取usb設(shè)備的描述信息。
typedef struct _USB_DEVICE_DESCRIPTOR
{
UCHAR bLength;
UCHAR bDescriptorType;
USHORT bcdUSB;
UCHAR bDeviceClass;
UCHAR bDeviceSubClass;
UCHAR bDeviceProtocol;
UCHAR bMaxPacketSize0;
USHORT idVendor;
USHORT idProduct;
USHORT bcdDevice;
UCHAR iManufacturer;
UCHAR iProduct;
UCHAR iSerialNumber;
UCHAR bNumConfigurations;
} USB_DEVICE_DESCRIPTOR, *PUSB_DEVICE_DESCRIPTOR;
typedef struct _USB_DEVICE_DESCRIPTOR
{
UCHAR bLength;
UCHAR bDescriptorType;
USHORT bcdUSB;
UCHAR bDeviceClass;
UCHAR bDeviceSubClass;
UCHAR bDeviceProtocol;
UCHAR bMaxPacketSize0;
USHORT idVendor;
USHORT idProduct;
USHORT bcdDevice;
UCHAR iManufacturer;
UCHAR iProduct;
UCHAR iSerialNumber;
UCHAR bNumConfigurations;
} USB_DEVICE_DESCRIPTOR, *PUSB_DEVICE_DESCRIPTOR;
typedef enum _USB_CONNECTION_STATUS
{
NoDeviceConnected,
DeviceConnected,
/* failure codes, these map to fail reasons */
DeviceFailedEnumeration,
DeviceGeneralFailure,
DeviceCausedOvercurrent,
DeviceNotEnoughPower,
DeviceNotEnoughBandwidth,
DeviceHubNestedTooDeeply,
DeviceInLegacyHub
} USB_CONNECTION_STATUS, *PUSB_CONNECTION_STATUS;
typedef struct _USB_PIPE_INFO
{
USB_ENDPOINT_DESCRIPTOR EndpointDescriptor;
ULONG ScheduleOffset;
} USB_PIPE_INFO, *PUSB_PIPE_INFO;
typedef struct _USB_ENDPOINT_DESCRIPTOR
{
UCHAR bLength;
UCHAR bDescriptorType;
UCHAR bEndpointAddress;
UCHAR bmAttributes;
USHORT wMaxPacketSize;
UCHAR bInterval;
} USB_ENDPOINT_DESCRIPTOR, *PUSB_ENDPOINT_DESCRIPTOR;
需要注意一點，如果要得到pid,vid,則直接從USB_DEVICE_DESCRIPTOR結(jié)構(gòu)中取出idVendor，idProduct這兩項的值就行了。如果要得到序列號，則不是取出 iSerialNumber就可以的。這里的 iSerialNumber僅僅是一個索引值。如果想得到序列號，就需要定義一個結(jié)構(gòu)，然后給設(shè)備發(fā)送個請求。請求的結(jié)構(gòu)如下圖：
代碼參照GetStringDescriptor函數(shù)。可以根據(jù)
iSerialNumber偏移，取出其對應的字符串，存放在上圖USB_STRING_DESCRIPTOR結(jié)構(gòu)中。