LibUSB + multiple WinUSB functions in composite device

msf_descriptor.py

def compatibility_id():
    return msft.CompatibilityIdTriple(
        descriptorIndex=4,
        sectionsCount=3,

        interfaceNumber0=0,
        compatibleId0='WINUSB',
        subCompatibleId0='',

        interfaceNumber1=1,
        compatibleId1='WINUSB',
        subCompatibleId1='',

        interfaceNumber2=4,
        compatibleId2='WINUSB',
        subCompatibleId2=''
    )


def extended_descriptor1():
    return msft.ExtendedDescriptor(
        sections=[
            msft.ExtendedDescriptor.Section(
                data_type=1,
                property_name='DeviceInterfaceGUID\0',
                value='{644991b2-1f10-45f7-a445-9a50ee4ce73d}\0'
            )
        ]
    )


def extended_descriptor2():
    return msft.ExtendedDescriptor(
        sections=[
            msft.ExtendedDescriptor.Section(
                data_type=1,
                property_name='DeviceInterfaceGUID\0',
                value='{13b2b252-adbf-45f8-9512-07342e35f305}\0'
            )
        ]
    )

def extended_descriptor3():
    return msft.ExtendedDescriptor(
        sections=[
            msft.ExtendedDescriptor.Section(
                data_type=1,
                property_name='DeviceInterfaceGUID\0',
                value='{519c4f5a-9543-4a53-8da2-5f6b428421a6}\0'
            )
        ]
    )

usb_descriptor.py

def make_descriptor(collection: DeviceDescriptorCollection) -> None:
    with collection.DeviceDescriptor() as d:
        d.idVendor = int.from_bytes(b'MN', byteorder='big')
        d.idProduct = int.from_bytes(b'DU', byteorder='big')
        d.bcdDevice = 0x00_15
        d.bNumConfigurations = 1
        d.bDeviceClass = CLASS_MISC
        d.bDeviceSubclass = SUBCLASS_MISC_IAD
        d.bDeviceProtocol = PROTOCOL_MISC_IAD

        d.iManufacturer = 'Novakov'
        d.iProduct = 'Double WinUSB'
        d.iSerialNumber = '123456'

    with collection.ConfigurationDescriptor() as c:
        c: ConfigurationDescriptorEmitter

        # WinUSB device1
        with c.InterfaceDescriptor() as iface:
            iface: InterfaceDescriptorEmitter
            iface.bInterfaceNumber = 0
            iface.bInterfaceClass = CLASS_VENDOR

        with add_descriptor(c, InterfaceAssociationDescriptorEmitter) as iac:
            iac.bFirstInterface = 1
            iac.bInterfaceCount = 3
            iac.bFunctionClass = CLASS_VENDOR
            iac.bFunctionSubClass = ord('A')
            iac.bFunctionProtocol = 0
            iac.iFunction = collection.get_index_for_string('IAD Device')

        # WinUSB IAD Device
        with c.InterfaceDescriptor() as iface:
            iface: InterfaceDescriptorEmitter
            iface.bInterfaceNumber = 1
            iface.bInterfaceClass = CLASS_VENDOR
            iface.bInterfaceSubclass = ord('1')

        with c.InterfaceDescriptor() as iface:
            iface: InterfaceDescriptorEmitter
            iface.bInterfaceNumber = 2
            iface.bInterfaceClass = CLASS_VENDOR
            iface.bInterfaceSubclass = ord('2')

        with c.InterfaceDescriptor() as iface:
            iface: InterfaceDescriptorEmitter
            iface.bInterfaceNumber = 3
            iface.bInterfaceClass = CLASS_VENDOR
            iface.bInterfaceSubclass = ord('3')

        with c.InterfaceDescriptor() as iface:
            iface: InterfaceDescriptorEmitter
            iface.bInterfaceNumber = 4
            iface.bInterfaceClass = CLASS_VENDOR
            iface.iInterface = 'Third device'

vendor transfer callback.cpp

bool tud_vendor_control_xfer_cb(uint8_t rhport, uint8_t stage, tusb_control_request_t const* request)
{
    // nothing to with DATA & ACK stage
    if(stage != CONTROL_STAGE_SETUP)
        return true;
    if((request->bmRequestType_bit.type == TUSB_REQ_TYPE_VENDOR) &&
       (request->bmRequestType_bit.recipient == TUSB_REQ_RCPT_DEVICE) && (request->bRequest == 0xAA))
    {
        tud_control_status(rhport, request);
        return true;
    }

    if((request->bmRequestType_bit.type == TUSB_REQ_TYPE_VENDOR) && (request->bRequest == 0x33) &&
       (request->wIndex == 4))
    {
        return tud_control_xfer(
            rhport,
            request,
            (void*)usb::descriptors::msft::CompatibilityId,
            usb::descriptors::msft::CompatibilityIdLength);
    }

    if((request->bmRequestType_bit.type == TUSB_REQ_TYPE_VENDOR) && (request->bRequest == 0x33) &&
       (request->wIndex == 5))
    {
        switch((request->wValue & 0xFF))
        {
            case 0:
                return tud_control_xfer(
                    rhport,
                    request,
                    (void*)usb::descriptors::msft::ExtendedDescriptor1,
                    usb::descriptors::msft::ExtendedDescriptorLength1);
            case 1:
                return tud_control_xfer(
                    rhport,
                    request,
                    (void*)usb::descriptors::msft::ExtendedDescriptor2,
                    usb::descriptors::msft::ExtendedDescriptorLength2);
            case 4:
                return tud_control_xfer(
                    rhport,
                    request,
                    (void*)usb::descriptors::msft::ExtendedDescriptor3,
                    usb::descriptors::msft::ExtendedDescriptorLength3);
            default:;
        }
    }

    return false;
}