diff --git a/headers/private/kernel/disk_device_manager/ddm_userland_interface.h b/headers/private/kernel/disk_device_manager/ddm_userland_interface.h
index 562245cffb..3e810dabb5 100644
--- a/headers/private/kernel/disk_device_manager/ddm_userland_interface.h
+++ b/headers/private/kernel/disk_device_manager/ddm_userland_interface.h
@@ -3,7 +3,12 @@
 #ifndef _DISK_DEVICE_MANAGER_USERLAND_INTERFACE_H
 #define _DISK_DEVICE_MANAGER_USERLAND_INTERFACE_H
 
-#include "disk_device_manager.h"
+#include <DiskDeviceDefs.h>
+#include <OS.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
 
 // userland partition representation
 struct user_partition_data {
@@ -14,6 +19,7 @@ struct user_partition_data {
 	uint32				status;
 	uint32				flags;
 	dev_t				volume;
+	int32				index;
 	int32				change_counter;	// needed?
 	disk_system_id		disk_system;
 	char				*name;
@@ -49,20 +55,23 @@ struct user_disk_device_job_info {
 };
 
 // iterating, retrieving device/partition data
-partition_id get_next_disk_device_id(int32 *cookie, size_t neededSize = NULL);
-status_t get_disk_device_data(partition_id deviceID, bool shadow,
-							  user_disk_device_data *buffer,
-							  size_t bufferSize, size_t *neededSize);
-status_t get_partition_data(partition_id partitionID, bool shadow,
-							user_partition_data *buffer,
-							size_t bufferSize, size_t *neededSize);
-	// Dangerous?!
-status_t get_partitionable_spaces(partition_id partitionID, bool shadow,
-								  user_partitionable_space_data *buffer,
+partition_id _kern_get_next_disk_device_id(int32 *cookie,
+										   size_t *neededSize = NULL);
+status_t _kern_get_disk_device_data(partition_id deviceID, bool shadow,
+									user_disk_device_data *buffer,
+									size_t bufferSize, size_t *neededSize);
+status_t _kern_get_partition_data(partition_id partitionID, bool shadow,
+								  user_partition_data *buffer,
 								  size_t bufferSize, size_t *neededSize);
+	// Dangerous?!
+status_t _kern_get_partitionable_spaces(partition_id partitionID, bool shadow,
+										user_partitionable_space_data *buffer,
+										size_t bufferSize, size_t *neededSize);
 	// Pass the partition change counter? If GetPartitionInfo() is only
 	// allowed, when the device is locked, then we wouldn't need it.
 
+#if 0
+
 // disk systems
 status_t find_disk_system(const char *name, disk_system_id *id);
 status_t get_next_disk_system(disk_system_id *id, char *name, int32 *cookie);
@@ -114,4 +123,10 @@ status_t start_disk_device_job_watching(disk_job_id job, port_id, int32 token,
 										uint32 flags);
 status_t stop_disk_device_watching(port_id, int32 token);
 
+#endif	// 0
+
+#ifdef __cplusplus
+}
+#endif
+
 #endif	// _DISK_DEVICE_MANAGER_USERLAND_INTERFACE_H
diff --git a/src/kernel/core/disk_device_manager/ddm_user_interface.cpp b/src/kernel/core/disk_device_manager/ddm_user_interface.cpp
new file mode 100644
index 0000000000..4dc3cb693f
--- /dev/null
+++ b/src/kernel/core/disk_device_manager/ddm_user_interface.cpp
@@ -0,0 +1,55 @@
+// ddm_userland_interface.cpp
+
+#include <KDiskDevice.h>
+#include <KDiskDeviceManager.h>
+#include <KDiskDeviceUtils.h>
+
+#include "ddm_userland_interface.h"
+#include "UserDataWriter.h"
+
+// _kern_get_next_disk_device_id
+partition_id
+_kern_get_next_disk_device_id(int32 *cookie, size_t *neededSize)
+{
+	if (!cookie)
+		return B_BAD_VALUE;
+	partition_id id = B_ERROR;
+	KDiskDeviceManager *manager = KDiskDeviceManager::Default();
+	if (KDiskDevice *device = manager->RegisterNextDevice(cookie)) {
+		PartitionRegistrar _(device, true);
+		id = device->ID();
+		if (neededSize) {
+			if (DeviceReadLocker locker = device) {
+				UserDataWriter writer;
+				device->WriteUserData(writer, false);
+				*neededSize = writer.AllocatedSize();
+			} else
+				return B_ERROR;
+		}
+	}
+	return id;
+}
+
+// _kern_get_disk_device_data
+status_t
+_kern_get_disk_device_data(partition_id deviceID, bool shadow,
+						   user_disk_device_data *buffer, size_t bufferSize,
+						   size_t *neededSize)
+{
+	if (!buffer && bufferSize > 0)
+		return B_BAD_VALUE;
+	KDiskDeviceManager *manager = KDiskDeviceManager::Default();
+	if (KDiskDevice *device = manager->RegisterDevice(deviceID)) {
+		PartitionRegistrar _(device, true);
+		if (DeviceReadLocker locker = device) {
+			UserDataWriter writer(buffer, bufferSize);
+			device->WriteUserData(writer, shadow);
+			if (neededSize)
+				*neededSize = writer.AllocatedSize();
+			if (writer.AllocatedSize() <= bufferSize)
+				return B_OK;
+		}
+	}
+	return B_ERROR;
+}
+