Usage of 'NtOpenFile' to access a device driver that doesn't export any symlink

beep.cpp

#include <Windows.h>
#include <stdio.h>
#include <winternl.h>

#pragma comment(lib, "ntdll")

#define IOCTL_BEEP      CTL_CODE(FILE_DEVICE_BEEP, 0, METHOD_BUFFERED, FILE_ANY_ACCESS)

typedef struct _BEEP_SETTINGS {
    ULONG ulFrequency;
    ULONG ulDuration;
} BEEP_SETTINGS;


int Error(const char* msg) {
    printf("%s (%u)\n", msg, GetLastError());
    return 1;
}

int main() {
    UNICODE_STRING name;
    OBJECT_ATTRIBUTES BeepObjectAttributes;
    IO_STATUS_BLOCK IOBlock;

    RtlInitUnicodeString(&name, L"\\Device\\Beep");
    InitializeObjectAttributes(&BeepObjectAttributes, &name, 0, nullptr, nullptr);

    IO_STATUS_BLOCK isb;
    HANDLE hDevice;
    auto status = NtOpenFile(&hDevice, GENERIC_WRITE, &BeepObjectAttributes, &isb, FILE_SHARE_WRITE, 0);

    BEEP_SETTINGS BeepSettings;
    BeepSettings.ulDuration = 10000;
    BeepSettings.ulFrequency = 500;
    
    DWORD bytes;

    if (!::DeviceIoControl(hDevice, IOCTL_BEEP, &BeepSettings, sizeof(BeepSettings), nullptr, 0, &bytes, nullptr))
        return Error("failed in DeviceIoControl");

    Sleep(1000);
    CloseHandle(hDevice);
    return 0;
}