usbutil.cpp File Reference

#include "fxusbpch.hpp"

Include dependency graph for usbutil.cpp:

Go to the source code of this file.

Functions
VOID	FxFormatUsbRequest (__in FxRequestBase *Request, __in PURB Urb, __in FX_URB_TYPE FxUrbType, __drv_when(FxUrbType==FxUrbTypeUsbdAllocated, __in) __drv_when(FxUrbType !=FxUrbTypeUsbdAllocated, __in_opt) USBD_HANDLE UsbdHandle)
NTSTATUS	FxFormatUrbRequest (__in PFX_DRIVER_GLOBALS FxDriverGlobals, __in FxIoTarget *Target, __in FxRequestBase *Request, __in FxRequestBuffer *Buffer, __in FX_URB_TYPE FxUrbType, __drv_when(FxUrbType==FxUrbTypeUsbdAllocated, __in) __drv_when(FxUrbType !=FxUrbTypeUsbdAllocated, __in_opt) USBD_HANDLE UsbdHandle)
NTSTATUS	FxUsbValidateConfigDescriptorHeaders (__in PFX_DRIVER_GLOBALS FxDriverGlobals, __in PUSB_CONFIGURATION_DESCRIPTOR ConfigDescriptor, __in size_t ConfigDescriptorLength)
PUSB_COMMON_DESCRIPTOR	FxUsbFindDescriptorType (__in PVOID Buffer, __in size_t BufferLength, __in PVOID Start, __in LONG DescriptorType)
NTSTATUS	FxUsbValidateDescriptorType (__in PFX_DRIVER_GLOBALS FxDriverGlobals, __in PUSB_CONFIGURATION_DESCRIPTOR ConfigDescriptor, __in PVOID Start, __in PVOID End, __in LONG DescriptorType, __in size_t SizeToValidate, __in FxUsbValidateDescriptorOp Op, __in ULONG MaximumNumDescriptorsToValidate)
PUSB_INTERFACE_DESCRIPTOR	FxUsbParseConfigurationDescriptor (__in PUSB_CONFIGURATION_DESCRIPTOR ConfigDesc, __in UCHAR InterfaceNumber, __in UCHAR AlternateSetting)
PURB	FxUsbCreateConfigRequest (__in PFX_DRIVER_GLOBALS FxDriverGlobals, __in PUSB_CONFIGURATION_DESCRIPTOR ConfigDesc, __in PUSBD_INTERFACE_LIST_ENTRY InterfaceList, __in ULONG DefaultMaxPacketSize)
VOID	FxUsbUmFormatRequest (__in FxRequestBase *Request, __in_xcount(Urb->Length) PUMURB_HEADER Urb, __in IWudfFile *HostFile, __in BOOLEAN Reuse)
VOID	FxUsbUmInitDescriptorUrb (__inout PUMURB UmUrb, __in WINUSB_INTERFACE_HANDLE WinUsbHandle, __in UCHAR DescriptorType, __in ULONG BufferLength, __in PVOID Buffer)
VOID	FxUsbUmInitControlTransferUrb (__inout PUMURB UmUrb, __in WINUSB_INTERFACE_HANDLE WinUsbHandle, __in ULONG BufferLength, __in PVOID Buffer)
VOID	FxUsbUmInitInformationUrb (__inout PUMURB UmUrb, __in WINUSB_INTERFACE_HANDLE WinUsbHandle, __in ULONG BufferLength, __in PVOID Buffer)

Function Documentation

FxFormatUrbRequest()

NTSTATUS FxFormatUrbRequest	(	__in PFX_DRIVER_GLOBALS	FxDriverGlobals,
		__in FxIoTarget *	Target,
		__in FxRequestBase *	Request,
		__in FxRequestBuffer *	Buffer,
		__in FX_URB_TYPE	FxUrbType,
		__drv_when(FxUrbType==FxUrbTypeUsbdAllocated, __in) __drv_when(FxUrbType !=FxUrbTypeUsbdAllocated, __in_opt) USBD_HANDLE	UsbdHandle
	)

Definition at line 64 of file usbutil.cpp.

{
    FxUsbUrbContext* pContext;
    NTSTATUS status;
 
    status = Request->ValidateTarget(Target);
    if (!NT_SUCCESS(status)) {
        DoTraceLevelMessage(FxDriverGlobals, TRACE_LEVEL_VERBOSE, TRACINGIOTARGET,
                            "FormatUrbRequest:  Target %p, Request %p, "
                            "setting target failed, %!STATUS!",
                            Target, Request, status);
 
        return status;
    }
 
    if (Request->HasContextType(FX_RCT_USB_URB_REQUEST)) {
        pContext = (FxUsbUrbContext*) Request->GetContext();
    }
    else {
        pContext = new(Target->GetDriverGlobals()) FxUsbUrbContext();
 
        if (pContext == NULL) {
            return STATUS_INSUFFICIENT_RESOURCES;
        }
 
        Request->SetContext(pContext);
    }
 
    //
    // Always set the memory after determining the context.  This way we can
    // free a previously referenced memory object if necessary.
    //
    pContext->StoreAndReferenceMemory(Buffer);
 
    FxFormatUsbRequest(Request, pContext->m_pUrb, FxUrbType, UsbdHandle);
 
    return STATUS_SUCCESS;
}

Referenced by __in_xcount().

FxFormatUsbRequest()

VOID FxFormatUsbRequest	(	__in FxRequestBase *	Request,
		__in PURB	Urb,
		__in FX_URB_TYPE	FxUrbType,
		__drv_when(FxUrbType==FxUrbTypeUsbdAllocated, __in) __drv_when(FxUrbType !=FxUrbTypeUsbdAllocated, __in_opt) USBD_HANDLE	UsbdHandle
	)

Definition at line 31 of file usbutil.cpp.

{
    FxIrp* irp;
 
    ASSERT(Urb->UrbHeader.Length >= sizeof(_URB_HEADER));
 
    irp = Request->GetSubmitFxIrp();
    irp->ClearNextStackLocation();
    irp->SetMajorFunction(IRP_MJ_INTERNAL_DEVICE_CONTROL);
    irp->SetParameterIoctlCode(IOCTL_INTERNAL_USB_SUBMIT_URB);
 
 
 
 
 
    if (FxUrbType == FxUrbTypeUsbdAllocated) {
        USBD_AssignUrbToIoStackLocation(UsbdHandle, irp->GetNextIrpStackLocation(), Urb);
    }
    else {
        irp->SetNextStackParameterOthersArgument1(Urb);
    }
 
    Request->VerifierSetFormatted();
}

Referenced by FxUsbDevice::Deconfig(), FxUsbPipe::FormatAbortRequest(), FxUsbDevice::FormatControlRequest(), FxUsbPipe::FormatResetRequest(), FxUsbDevice::FormatStringRequest(), FxUsbPipe::FormatTransferRequest(), FxFormatUrbRequest(), FxUsbDevice::GetString(), FxUsbDevice::InitDevice(), FxUsbDevice::SelectConfig(), and FxUsbInterface::SelectSetting().

FxUsbCreateConfigRequest()

PURB FxUsbCreateConfigRequest	(	__in PFX_DRIVER_GLOBALS	FxDriverGlobals,
		__in PUSB_CONFIGURATION_DESCRIPTOR	ConfigDesc,
		__in PUSBD_INTERFACE_LIST_ENTRY	InterfaceList,
		__in ULONG	DefaultMaxPacketSize
	)

Definition at line 366 of file usbutil.cpp.

{
    PURB urb;
    PUSBD_INTERFACE_LIST_ENTRY pList;
    USHORT size;
 
    //
    // Our mission here is to construct a URB of the proper
    // size and format for a select_configuration request.
    //
    // This function uses the configuration descriptor as a
    // reference and builds a URB with interface_information
    // structures for each interface requested in the interface
    // list passed in
    //
    // NOTE: the config descriptor may contain interfaces that
    // the caller does not specify in the list -- in this case
    // the other interfaces will be ignored.
    //
 
    //
    // First figure out how many interfaces we are dealing with
    //
    pList = InterfaceList;
 
    //
    // For a multiple interface configuration, GET_SELECT_CONFIGURATION_REQUEST_SIZE
    // doesn't work as expected.  This is because it subtracts one from totalPipes
    // to compensate for the embedded USBD_PIPE_INFORMATION in USBD_INTERFACE_INFORMATION.
    // A multiple interface device will have more then one embedded
    // USBD_PIPE_INFORMATION in its configuration request and any of these interfaces
    // might not have any pipes on them.
    //
    // To fix, just iterate and compute the size incrementally.
    //
    if (InterfaceList[0].InterfaceDescriptor != NULL) {
        size = sizeof(_URB_SELECT_CONFIGURATION) - sizeof(USBD_INTERFACE_INFORMATION);
 
        while (pList->InterfaceDescriptor != NULL) {
            NTSTATUS status;
 
            status = RtlUShortAdd(size,
                                  GET_USBD_INTERFACE_SIZE(
                                        pList->InterfaceDescriptor->bNumEndpoints),
                                  &size);
            if (!NT_SUCCESS(status)) {
                DoTraceLevelMessage(
                    FxDriverGlobals, TRACE_LEVEL_ERROR, TRACINGIOTARGET,
                    "InterfaceList %p, NumEndPoints 0x%x, "
                    "Integer overflow while calculating interface size, %!STATUS!",
                    InterfaceList,
                    pList->InterfaceDescriptor->bNumEndpoints,
                    status);
                return NULL;
            }
            pList++;
        }
    }
    else {
        size = sizeof(_URB_SELECT_CONFIGURATION);
    }
 
    //
    // Make sure we are dealing with a value that fits into a USHORT
    //
    ASSERT(size <= 0xFFFF);
 
    urb = (PURB) FxPoolAllocate(FxDriverGlobals, NonPagedPool, size);
 
    if (urb != NULL) {
        PUCHAR pCur;
 
        //
        // now all we have to do is initialize the urb
        //
        RtlZeroMemory(urb, size);
 
        pList = InterfaceList;
 
        pCur = (PUCHAR) &urb->UrbSelectConfiguration.Interface;
        while (pList->InterfaceDescriptor != NULL) {
            PUSB_INTERFACE_DESCRIPTOR pInterfaceDesc;
            PUSBD_INTERFACE_INFORMATION pInterfaceInfo;
 
            pInterfaceDesc = pList->InterfaceDescriptor;
 
            pInterfaceInfo = (PUSBD_INTERFACE_INFORMATION) pCur;
#pragma prefast(suppress: __WARNING_BUFFER_OVERFLOW, "Esp:675");
            pInterfaceInfo->InterfaceNumber = pInterfaceDesc->bInterfaceNumber;
            pInterfaceInfo->AlternateSetting = pInterfaceDesc->bAlternateSetting;
            pInterfaceInfo->NumberOfPipes = pInterfaceDesc->bNumEndpoints;
            pInterfaceInfo->Length = (USHORT)
                GET_USBD_INTERFACE_SIZE(pInterfaceDesc->bNumEndpoints);
 
            for (LONG j = 0; j < pInterfaceDesc->bNumEndpoints; j++) {
                pInterfaceInfo->Pipes[j].PipeFlags = 0;
                pInterfaceInfo->Pipes[j].MaximumTransferSize = DefaultMaxPacketSize;
            }
 
            ASSERT(pCur + pInterfaceInfo->Length <= ((PUCHAR) urb) + size);
 
            pList->Interface = pInterfaceInfo;
 
            pList++;
            pCur += pInterfaceInfo->Length;
        }
 
        urb->UrbHeader.Length   = size;
        urb->UrbHeader.Function = URB_FUNCTION_SELECT_CONFIGURATION;
        urb->UrbSelectConfiguration.ConfigurationDescriptor = ConfigDesc;
    }
 
    return urb;
}

Referenced by FxUsbDevice::SelectConfigDescriptor(), FxUsbDevice::SelectConfigInterfaces(), FxUsbDevice::SelectConfigMulti(), and FxUsbDevice::SelectConfigSingle().

FxUsbFindDescriptorType()

PUSB_COMMON_DESCRIPTOR FxUsbFindDescriptorType	(	__in PVOID	Buffer,
		__in size_t	BufferLength,
		__in PVOID	Start,
		__in LONG	DescriptorType
	)

Definition at line 176 of file usbutil.cpp.

{
    PUSB_COMMON_DESCRIPTOR descriptor;
    PUCHAR pCur, pEnd;
 
    pCur = (PUCHAR) Start;
    pEnd = ((PUCHAR) Buffer) + BufferLength;
 
    while (pCur < pEnd) {
        //
        // Check to see if the current point is the desired descriptor type
        //
        descriptor = (PUSB_COMMON_DESCRIPTOR) pCur;
 
        if (descriptor->bDescriptorType == DescriptorType) {
            return descriptor;
        }
 
        pCur += descriptor->bLength;
    }
 
    //
    // Iterated to the end and found nothing
    //
    return NULL;
}

Referenced by FxUsbDevice::CreateInterfaces(), FxUsbInterface::CreateSettings(), FxUsbParseConfigurationDescriptor(), and FxUsbValidateDescriptorType().

FxUsbParseConfigurationDescriptor()

PUSB_INTERFACE_DESCRIPTOR FxUsbParseConfigurationDescriptor	(	__in PUSB_CONFIGURATION_DESCRIPTOR	ConfigDesc,
		__in UCHAR	InterfaceNumber,
		__in UCHAR	AlternateSetting
	)

Definition at line 309 of file usbutil.cpp.

{
    PUSB_INTERFACE_DESCRIPTOR found, usbInterface;
    PVOID pStart;
 
    found = NULL,
 
    ASSERT(ConfigDesc->bDescriptorType == USB_CONFIGURATION_DESCRIPTOR_TYPE);
 
    //
    // Walk the table of descriptors looking for an interface descriptor with
    // parameters matching those passed in.
    //
    pStart = ConfigDesc;
 
    do {
        //
        // Search for descriptor type 'interface'
        //
        usbInterface = (PUSB_INTERFACE_DESCRIPTOR)
            FxUsbFindDescriptorType(ConfigDesc,
                                    ConfigDesc->wTotalLength,
                                    pStart,
                                    USB_INTERFACE_DESCRIPTOR_TYPE);
 
        //
        // Check to see if have a matching descriptor by eliminating mismatches
        //
        if (usbInterface != NULL) {
            found = usbInterface;
 
            if (InterfaceNumber != -1 &&
                usbInterface->bInterfaceNumber != InterfaceNumber) {
                found = NULL;
            }
 
            if (AlternateSetting != -1 &&
                usbInterface->bAlternateSetting != AlternateSetting) {
                found = NULL;
            }
 
            pStart = ((PUCHAR)usbInterface) + usbInterface->bLength;
        }
 
        if (found != NULL) {
            break;
        }
    } while (usbInterface!= NULL);
 
    return found;
}

Referenced by FxUsbDevice::SelectConfigMulti().

FxUsbUmFormatRequest()

VOID FxUsbUmFormatRequest	(	__in FxRequestBase *	Request,
		__in_xcount(Urb->Length) PUMURB_HEADER	Urb,
		__in IWudfFile *	HostFile,
		__in BOOLEAN	Reuse
	)

Definition at line 488 of file usbutil.cpp.

{
    FX_VERIFY(INTERNAL, CHECK_NOT_NULL(Request));
    FX_VERIFY(INTERNAL, CHECK_NOT_NULL(Urb));
    FX_VERIFY(INTERNAL, CHECK_TODO(Urb->Length >= sizeof(_UMURB_HEADER)));
    FX_VERIFY(INTERNAL, CHECK_NOT_NULL(HostFile));
 
    IWudfIoIrp* pIoIrp = NULL;
    IWudfIrp* pIrp = Request->GetSubmitIrp();
 
    if (Reuse) {
        //
        // This allows us to use the same FxSyncRequest
        // stack object multiple times.
        //
        Request->GetSubmitFxIrp()->Reuse(STATUS_SUCCESS);
        Request->ClearFieldsForReuse();
    }
 
    HRESULT hrQI = pIrp->QueryInterface(IID_IWudfIoIrp, (PVOID*)&pIoIrp);
    FX_VERIFY(INTERNAL, CHECK_QI(hrQI, pIoIrp));
 
    pIoIrp->SetTypeForNextStackLocation(UMINT::WdfRequestInternalIoctl);
 
 
 
 
    pIoIrp->SetDeviceIoControlParametersForNextStackLocation(IOCTL_INETRNAL_USB_SUBMIT_UMURB,
                                                             0,
                                                             0);
 
    pIoIrp->SetOtherParametersForNextStackLocation((PVOID*)&Urb,
                                                   NULL,
                                                   NULL,
                                                   NULL);
 
    pIoIrp->SetFileForNextIrpStackLocation(HostFile);
 
    //
    // Release reference taken by QI
    //
    SAFE_RELEASE(pIoIrp);
    Request->VerifierSetFormatted();
}

Referenced by FxUsbPipe::FormatAbortRequest(), FxUsbPipe::FormatResetRequest(), and FxUsbDevice::SendSyncUmUrb().

FxUsbUmInitControlTransferUrb()

VOID FxUsbUmInitControlTransferUrb	(	__inout PUMURB	UmUrb,
		__in WINUSB_INTERFACE_HANDLE	WinUsbHandle,
		__in ULONG	BufferLength,
		__in PVOID	Buffer
	)

Definition at line 580 of file usbutil.cpp.

{
    RtlZeroMemory(UmUrb, sizeof(UMURB));
 
    UmUrb->UmUrbControlTransfer.Hdr.InterfaceHandle = WinUsbHandle;
    UmUrb->UmUrbControlTransfer.Hdr.Function = UMURB_FUNCTION_CONTROL_TRANSFER;
    UmUrb->UmUrbControlTransfer.Hdr.Length = sizeof(_UMURB_CONTROL_TRANSFER);
 
    UmUrb->UmUrbControlTransfer.TransferBufferLength = BufferLength;
    UmUrb->UmUrbControlTransfer.TransferBuffer = Buffer;
}

FxUsbUmInitDescriptorUrb()

VOID FxUsbUmInitDescriptorUrb	(	__inout PUMURB	UmUrb,
		__in WINUSB_INTERFACE_HANDLE	WinUsbHandle,
		__in UCHAR	DescriptorType,
		__in ULONG	BufferLength,
		__in PVOID	Buffer
	)

Definition at line 558 of file usbutil.cpp.

{
    RtlZeroMemory(UmUrb, sizeof(UMURB));
 
    UmUrb->UmUrbDescriptorRequest.Hdr.InterfaceHandle = WinUsbHandle;
    UmUrb->UmUrbDescriptorRequest.Hdr.Function = UMURB_FUNCTION_GET_DESCRIPTOR;
    UmUrb->UmUrbDescriptorRequest.Hdr.Length = sizeof(_UMURB_DESCRIPTOR_REQUEST);
 
    UmUrb->UmUrbDescriptorRequest.DescriptorType = DescriptorType;
    UmUrb->UmUrbDescriptorRequest.Index = 0;
    UmUrb->UmUrbDescriptorRequest.LanguageID = 0;
    UmUrb->UmUrbDescriptorRequest.BufferLength = BufferLength;
    UmUrb->UmUrbDescriptorRequest.Buffer = Buffer;
}

FxUsbUmInitInformationUrb()

VOID FxUsbUmInitInformationUrb	(	__inout PUMURB	UmUrb,
		__in WINUSB_INTERFACE_HANDLE	WinUsbHandle,
		__in ULONG	BufferLength,
		__in PVOID	Buffer
	)

Definition at line 598 of file usbutil.cpp.

{
    RtlZeroMemory(UmUrb, sizeof(UMURB));
 
    UmUrb->UmUrbDeviceInformation.Hdr.InterfaceHandle = WinUsbHandle;
    UmUrb->UmUrbDeviceInformation.Hdr.Function = UMURB_FUNCTION_GET_DEVICE_INFORMATION;
    UmUrb->UmUrbDeviceInformation.Hdr.Length = sizeof(_UMURB_DEVICE_INFORMATION);
 
    UmUrb->UmUrbDeviceInformation.InformationType = DEVICE_SPEED;
    UmUrb->UmUrbDeviceInformation.BufferLength = BufferLength;
    UmUrb->UmUrbDeviceInformation.Buffer = Buffer;
}

FxUsbValidateConfigDescriptorHeaders()

NTSTATUS FxUsbValidateConfigDescriptorHeaders	(	__in PFX_DRIVER_GLOBALS	FxDriverGlobals,
		__in PUSB_CONFIGURATION_DESCRIPTOR	ConfigDescriptor,
		__in size_t	ConfigDescriptorLength
	)

Definition at line 113 of file usbutil.cpp.

{
    PUCHAR pCur, pEnd;
 
    pCur = (PUCHAR) ConfigDescriptor;
    pEnd = pCur + ConfigDescriptorLength;
 
    while (pCur < pEnd) {
        PUSB_COMMON_DESCRIPTOR pDescriptor = (PUSB_COMMON_DESCRIPTOR) pCur;
 
        //
        // Make sure we can safely deref bLength, bDescriptorType
        //
        if (pCur + sizeof(USB_COMMON_DESCRIPTOR) > pEnd) {
            DoTraceLevelMessage(
                FxDriverGlobals, TRACE_LEVEL_ERROR, TRACINGIOTARGET,
                "USB Configuration packet contains bad data, expected "
                "at least %d remaining bytes in config descriptor at "
                "offset %I64d, total size is %I64d",
                sizeof(USB_COMMON_DESCRIPTOR), pCur-(PUCHAR)ConfigDescriptor,
                ConfigDescriptorLength
                );
            return STATUS_INVALID_PARAMETER;
        }
 
        //
        // Make sure bLength is within bounds of the config descriptor
        //
        if ((pCur + pDescriptor->bLength) > pEnd) {
            DoTraceLevelMessage(
                FxDriverGlobals, TRACE_LEVEL_ERROR, TRACINGIOTARGET,
                "USB Configuration packet contains bad data, descriptor at offset "
                "%I64d specified bLength %d, only %I64d bytes remaining in config "
                "descriptor, total size is %I64d",
                pCur-(PUCHAR)ConfigDescriptor, pDescriptor->bLength, pEnd-pCur,
                ConfigDescriptorLength
                );
            return STATUS_INVALID_PARAMETER;
        }
 
        if (pDescriptor->bLength == 0) {
            DoTraceLevelMessage(
                FxDriverGlobals, TRACE_LEVEL_ERROR, TRACINGIOTARGET,
                "USB Configuration packet contains bad data, descriptor at offset "
                "%I64d contains bLength == 0, this is due to a broken device or driver",
                pCur - (PUCHAR) ConfigDescriptor
                );
            return STATUS_INVALID_PARAMETER;
        }
 
 
        pCur += pDescriptor->bLength;
    }
 
    return STATUS_SUCCESS;
}

Referenced by FxUsbDevice::CreateInterfaces().

FxUsbValidateDescriptorType()

NTSTATUS FxUsbValidateDescriptorType	(	__in PFX_DRIVER_GLOBALS	FxDriverGlobals,
		__in PUSB_CONFIGURATION_DESCRIPTOR	ConfigDescriptor,
		__in PVOID	Start,
		__in PVOID	End,
		__in LONG	DescriptorType,
		__in size_t	SizeToValidate,
		__in FxUsbValidateDescriptorOp	Op,
		__in ULONG	MaximumNumDescriptorsToValidate
	)

Definition at line 209 of file usbutil.cpp.

{
    PUSB_COMMON_DESCRIPTOR pDescriptor = NULL;
    PVOID pCur = Start;
    ULONG i = 1;
 
    while ((pDescriptor = FxUsbFindDescriptorType(Start,
                                                  (PUCHAR)End-(PUCHAR)Start,
                                                  pCur,
                                                  DescriptorType
                                                  )) != NULL) {
        //
        // Make sure bLength is the correct value
        //
        if (Op == FxUsbValidateDescriptorOpEqual) {
            if (pDescriptor->bLength != SizeToValidate) {
                DoTraceLevelMessage(
                    FxDriverGlobals, TRACE_LEVEL_ERROR, TRACINGIOTARGET,
                    "USB Configuration packet contains bad data, found descriptor "
                    "#%d of type %d at offset %I64d, expected bLength of %I64d, found %d",
                    i, DescriptorType, ((PUCHAR)pDescriptor)-((PUCHAR)ConfigDescriptor),
                    SizeToValidate, pDescriptor->bLength
                    );
                return STATUS_INVALID_PARAMETER;
            }
        }
        else if (Op == FxUsbValidateDescriptorOpAtLeast) {
            if (pDescriptor->bLength < SizeToValidate) {
                DoTraceLevelMessage(
                    FxDriverGlobals, TRACE_LEVEL_ERROR, TRACINGIOTARGET,
                    "USB Configuration packet contains bad data, found descriptor "
                    "#%d of type %d at offset %I64d, expected minimum bLength of %I64d, "
                    "found %d",
                    i, DescriptorType, ((PUCHAR)pDescriptor)-((PUCHAR)ConfigDescriptor),
                    SizeToValidate, pDescriptor->bLength
                    );
                return STATUS_INVALID_PARAMETER;
            }
        }
 
        //
        // No need to validate WDF_PTR_ADD_OFFSET(pDescriptor, pDescriptor->bLength) > End
        // because FxUsbValidateConfigDescriptorHeaders already has done so. End is either
        // 1) == end of the config descriptor, in which case FxUsbValidateConfigDescriptorHeaders
        //    directly validated bLength
        // or
        // 2) End is somewere in the middle of the config descriptor and ASSUMED to be the start
        //    of a common descriptor header. To find that value of End, we would have had to use
        //    pDescriptor->bLength to get to End, we would not overrun
        //
 
        //
        // i is one based, so the current value is Nth descriptor we have validated. If
        // the caller wants to limit the number of descriptors validated by indicating a
        // Max > 0, stop with success if the condition is met.
        //
        if (MaximumNumDescriptorsToValidate > 0 && i == MaximumNumDescriptorsToValidate) {
            break;
        }
 
        pCur = WDF_PTR_ADD_OFFSET(pDescriptor, pDescriptor->bLength);
        i++;
    }
 
    return STATUS_SUCCESS;
}

Referenced by FxUsbDevice::CreateInterfaces(), and FxUsbInterface::CreateSettings().