Failed to switch Samsung Fold 4 to Accessory Mode

Question

I have developed a code using the libusb library to send USB packets to a Samsung device. Initially, I tested it with my Samsung Note 10. After running the code, the device transitioned to accessory mode, as indicated by the output of the lsusb command:

Before running the code:

Bus 001 Device 079: ID 04e8:6860 Samsung Electronics Co., Ltd Galaxy series, misc. (MTP mode)

After running the code:

Bus 001 Device 080: ID 18d1:2d01 Google Inc. Android Open Accessory device (accessory + ADB)

However, when attempting to use the same code with my Samsung Fold 4, the device did not transition to accessory mode. I'm uncertain whether the Fold 4 supports accessory mode. Could someone confirm this? Additionally, I would appreciate any insights into what might be wrong with my code.

#include <iostream>
#include <cstring>
#include <libusb-1.0/libusb.h>

// Define vendor and product IDs for Samsung devices
#define SAMSUNG_ACCESSORY_VID 0x04e8  // Samsung's vendor ID
#define SAMSUNG_ACCESSORY_PID 0x6860  // PID for accessory mode

// Define Android accessory protocol requests
#define ACCESSORY_GET_PROTOCOL 51
#define ACCESSORY_SEND_STRING 52
#define ACCESSORY_START 53

// Define accessory identification strings
#define MANUFACTURER "YourManufacturer"
#define MODEL "YourModel"
#define DESCRIPTION "YourDescription"
#define VERSION "1.0"
#define URI "http://your.uri"
#define SERIAL_NUMBER "YourSerialNumber"

// Function to send accessory command to the device
void send_accessory_command(libusb_device_handle* handle, int request, const char* data) {
    libusb_control_transfer(handle,
                            LIBUSB_REQUEST_TYPE_VENDOR | LIBUSB_RECIPIENT_DEVICE | LIBUSB_ENDPOINT_OUT,
                            request, 0, 0, (unsigned char*)data, data ? strlen(data) + 1 : 0, 0);
}

int main() {
    libusb_device_handle* handle = nullptr;
    libusb_context* ctx = nullptr;

    // Initialize libusb
    int r = libusb_init(&ctx);
    if (r < 0) {
        std::cerr << "Error initializing libusb: " << libusb_error_name(r) << std::endl;
        return 1;
    }

    // Try to open the Samsung Fold 4 device in accessory mode
    handle = libusb_open_device_with_vid_pid(ctx, SAMSUNG_ACCESSORY_VID, SAMSUNG_ACCESSORY_PID);
    if (!handle) {
        std::cerr << "Could not find Samsung Fold 4 device in accessory mode." << std::endl;
        libusb_exit(ctx);
        return 1;
    }

    // Check accessory protocol version
    unsigned char protocol[2];
    int protocolVersion = 0;
    r = libusb_control_transfer(handle, LIBUSB_ENDPOINT_IN | LIBUSB_REQUEST_TYPE_VENDOR | LIBUSB_RECIPIENT_DEVICE,
                                ACCESSORY_GET_PROTOCOL, 0, 0, protocol, sizeof(protocol), 0);
    if (r >= 0) {
        protocolVersion = protocol[1] << 8 | protocol[0];
    }
    std::cerr << "Accessory protocol: " << protocolVersion << std::endl;

    // Check if accessory protocol is supported
    if (protocolVersion < 1) {
        std::cerr << "Accessory protocol not supported." << std::endl;
        libusb_release_interface(handle, 0);
        libusb_close(handle);
        libusb_exit(ctx);
        return 1;
    }

    // Send accessory identification strings
    send_accessory_command(handle, ACCESSORY_SEND_STRING, MANUFACTURER);
    send_accessory_command(handle, ACCESSORY_SEND_STRING, MODEL);
    send_accessory_command(handle, ACCESSORY_SEND_STRING, DESCRIPTION);
    send_accessory_command(handle, ACCESSORY_SEND_STRING, VERSION);
    send_accessory_command(handle, ACCESSORY_SEND_STRING, URI);
    send_accessory_command(handle, ACCESSORY_SEND_STRING, SERIAL_NUMBER);

    // Switch the device to accessory mode
    send_accessory_command(handle, ACCESSORY_START, NULL);

    // Output message indicating successful switch to accessory mode
    std::cout << "Switched to accessory mode." << std::endl;

    // Clean up libusb resources
    libusb_release_interface(handle, 0);
    libusb_close(handle);
    libusb_exit(ctx);

    return 0;
}