[参考译文] TM4C123GE6PM：USB 器件：是否添加描述符回调函数？

尊敬的 Charles：

感谢您的答复！  我认为我的选择是正确的，你是正确的，我必须重新编译 usblib，因为我做了一些测试更改，但没有被采纳，因为我链接到它，而不是编译它。  关于那个主题-你知道重新编译这个库的步骤的大致顺序吗？ 或者是否有某处 PDF 文件讨论过重新编译 TI 库？   

在 USB 问题主题上-我想我已经弄清楚了(理论上)您必须做什么来处理这个问题、不幸的是、您(我认为)必须编辑 usbdenum.c 文件。  我认为这是因为您必须修改该文件中第1937行中的较低级别的枚举处理程序-见下文。

//*****************************************************************************
//
// This function handles the GET_DESCRIPTOR standard USB request.
//
// \param pvInstance is the USB device controller instance data.
// \param psUSBRequest holds the data for this request.
//
// This function will return most of the descriptors requested by the host
// controller.  The descriptor specified by \e
// pvInstance->psInfo->pui8DeviceDescriptor will be returned when the device
// descriptor is requested.  If a request for a specific configuration
// descriptor is made, then the appropriate descriptor from the \e
// g_pConfigDescriptors will be returned.  When a request for a string
// descriptor is made, the appropriate string from the
// \e pvInstance->psInfo->pStringDescriptors will be returned.  If the
// \e pvInstance->psInfo->psCallbacks->GetDescriptor is specified it will be
// called to handle the request.  In this case it must call the
// USBDCDSendDataEP0() function to send the data to the host controller.  If
// the callback is not specified, and the descriptor request is not for a
// device, configuration, or string descriptor then this function will stall
// the request to indicate that the request was not supported by the device.
//
// \return None.
//
//*****************************************************************************
static void
USBDGetDescriptor(void *pvInstance, tUSBRequest *psUSBRequest)
{
    bool bConfig;
    tDCDInstance *psUSBControl;
    tDeviceInfo *psDevice;
    const tConfigHeader *psConfig;
    const tDeviceDescriptor *psDeviceDesc;
    uint8_t ui8Index;
    int32_t i32Index;

    ASSERT(psUSBRequest != 0);
    ASSERT(pvInstance != 0);

    //
    // Create the device information pointer.
    //
    psUSBControl = (tDCDInstance *)pvInstance;
    psDevice = g_ppsDevInfo[0];

    //
    // Need to ACK the data on end point 0 without setting last data as there
    // will be a data phase.
    //
    MAP_USBDevEndpointDataAck(USB0_BASE, USB_EP_0, false);

    //
    // Assume we are not sending the configuration descriptor until we
    // determine otherwise.
    //
    bConfig = false;

    //
    // Which descriptor are we being asked for?
    //
    switch(psUSBRequest->wValue >> 8)
    {
        //
        // This request was for a device descriptor.
        //
        case USB_DTYPE_DEVICE:
        {
            //
            // Return the externally provided device descriptor.
            //
            psUSBControl->pui8EP0Data =
                                    (uint8_t *)psDevice->pui8DeviceDescriptor;

            //
            // The size of the device descriptor is in the first byte.
            //
            psUSBControl->ui32EP0DataRemain =
                psDevice->pui8DeviceDescriptor[0];

            break;
        }

        //
        // This request was for a configuration descriptor.
        //
        case USB_DTYPE_CONFIGURATION:
        {
            //
            // Which configuration are we being asked for?
            //
            ui8Index = (uint8_t)(psUSBRequest->wValue & 0xFF);

            //
            // Is this valid?
            //
            psDeviceDesc =
                (const tDeviceDescriptor *)psDevice->pui8DeviceDescriptor;

            if(ui8Index >= psDeviceDesc->bNumConfigurations)
            {
                //
                // This is an invalid configuration index.  Stall EP0 to
                // indicate a request error.
                //
                USBDCDStallEP0(0);
                psUSBControl->pui8EP0Data = 0;
                psUSBControl->ui32EP0DataRemain = 0;
            }
            else
            {
                //
                // Return the externally specified configuration descriptor.
                //
                psConfig = psDevice->ppsConfigDescriptors[ui8Index];

                //
                // Start by sending data from the beginning of the first
                // descriptor.
                //
                psUSBControl->ui8ConfigSection = 0;
                psUSBControl->ui16SectionOffset = 0;
                psUSBControl->pui8EP0Data =
                                (uint8_t *)psConfig->psSections[0]->pui8Data;

                //
                // Determine the total size of the configuration descriptor
                // by counting the sizes of the sections comprising it.
                //
                psUSBControl->ui32EP0DataRemain =
                                            USBDCDConfigDescGetSize(psConfig);

                //
                // Remember that we need to send the configuration descriptor
                // and which descriptor we need to send.
                //
                psUSBControl->ui8ConfigIndex = ui8Index;

                bConfig = true;
            }
            break;
        }

        //
        // This request was for a string descriptor.
        //
        case USB_DTYPE_STRING:
        {
            //
            // Determine the correct descriptor index based on the requested
            // language ID and index.
            //
            i32Index = USBDStringIndexFromRequest(psUSBRequest->wIndex,
                                                  psUSBRequest->wValue & 0xFF);

            //
            // If the mapping function returned -1 then stall the request to
            // indicate that the request was not valid.
            //
            if(i32Index == -1)
            {
                USBDCDStallEP0(0);
                break;
            }

            //
            // Return the externally specified configuration descriptor.
            //
            psUSBControl->pui8EP0Data =
                (uint8_t *)psDevice->ppui8StringDescriptors[i32Index];

            //
            // The total size of a string descriptor is in byte 0.
            //
            psUSBControl->ui32EP0DataRemain =
                psDevice->ppui8StringDescriptors[i32Index][0];

            break;
        }

        //
        // Any other request is not handled by the default enumeration handler
        // so see if it needs to be passed on to another handler.
        //
        default:
        {
            //
            // If there is a handler for requests that are not handled then
            // call it.
            //
            if(psDevice->psCallbacks->pfnGetDescriptor)
            {
                psDevice->psCallbacks->pfnGetDescriptor(g_psDCDInst[0].pvCBData,
                                                      psUSBRequest);
            }
            else
            {
                //
                // Whatever this was this handler does not understand it so
                // just stall the request.
                //
                USBDCDStallEP0(0);
            }

            return;
        }
    }

    //
    // If this request has data to send, then send it.
    //
    if(psUSBControl->pui8EP0Data)
    {
        //
        // If there is more data to send than is requested then just
        // send the requested amount of data.
        //
        if(psUSBControl->ui32EP0DataRemain > psUSBRequest->wLength)
        {
            psUSBControl->ui32EP0DataRemain = psUSBRequest->wLength;
        }

        //
        // Now in the transmit data state.  Be careful to call the correct
        // function since we need to handle the configuration descriptor
        // differently from the others.
        //
        if(!bConfig)
        {
            USBDEP0StateTx(0);
        }
        else
        {
            USBDEP0StateTxConfig(0);
        }
    }
}

我认为我最初的方法不会起作用,因为"USB_DTYPE_STRING"需要从窗口捕捉描述符消息,因为它是一个"字符串描述符"请求。  仅当调用此函数中用于未知请求类型的默认情况时、才会触发自定义处理程序。  因此、"我认为"我需要修改 USB_DTYPE_string 情况、以查找字符串描述符偏移值0xEE (由 windows 为 OS 描述符指定)并捕获该值、而不是让失速事件执行。  不确定最佳的解决方法是什么、但您是否同意 TI USB 驱动程序库源代码、MOD 应该在该代码处处理来自操作系统的"非标准"字符串描述符请求？  坚持 if 语句来获取0xEE 偏移 case 是否几乎是所有可能需要添加的语句？