IGameInputDevice::GetInputReportInfo

uint32_t GetInputReportInfo(
    uint32_t infoArrayCount,
    GameInputRawDeviceReportInfo* infoArray
);

uint32_t reportCount = device->GetInputReportCount();
std::vector<GameInputRawDeviceReportInfo> reports(reportCount);
reports.resize(device->GetInputReportInfo(reportCount, reports.data()));

for (const GameInputRawDeviceReportInfo& report : reports)
{
    // report.id identifies an input report that can arrive in readings;
    // report.size is the size of its data in bytes.
}