diff --git a/drivers/wdm/audio/hdaudbus/fdo.cpp b/drivers/wdm/audio/hdaudbus/fdo.cpp
index b032073eb9..6b98d19cdf 100644
--- a/drivers/wdm/audio/hdaudbus/fdo.cpp
+++ b/drivers/wdm/audio/hdaudbus/fdo.cpp
@@ -235,7 +235,7 @@ HDA_InitCodec(
             AudioGroup->FunctionGroup = FUNCTION_GROUP_NODETYPE_AUDIO;
 
             // Found an Audio Function Group!
-            DPRINT1("NodeId %x found an audio function group!\n");
+            DPRINT1("NodeId %x found an audio function group!\n", NodeId);
 
             Status = IoCreateDevice(DeviceObject->DriverObject, sizeof(HDA_PDO_DEVICE_EXTENSION), NULL, FILE_DEVICE_SOUND, FILE_AUTOGENERATED_DEVICE_NAME, FALSE, &AudioGroup->ChildPDO);
             if (!NT_SUCCESS(Status))
@@ -257,10 +257,12 @@ HDA_InitCodec(
             AudioGroup->ChildPDO->Flags &= ~DO_DEVICE_INITIALIZING;
 
             /* add audio group*/
+            ASSERT(Entry->AudioGroupCount < HDA_MAX_AUDIO_GROUPS);
             Entry->AudioGroups[Entry->AudioGroupCount] = AudioGroup;
             Entry->AudioGroupCount++;
         }
     }
+    DPRINT1("Codec %lu %p has %lu AudioGroups\n", codecAddress, Entry, Entry->AudioGroupCount);
     return STATUS_SUCCESS;
 
 }
@@ -538,11 +540,13 @@ HDA_FDOStartDevice(
     /* get device extension */
     DeviceExtension = (PHDA_FDO_DEVICE_EXTENSION)DeviceObject->DeviceExtension;
     ASSERT(DeviceExtension->IsFDO == TRUE);
+    NT_VERIFY(InterlockedExchange(&DeviceExtension->Started, 1) == 0);
 
     /* forward irp to lower device */
     Status = HDA_SyncForwardIrp(DeviceExtension->LowerDevice, Irp);
     if (!NT_SUCCESS(Status))
     {
+        NT_VERIFY(InterlockedExchange(&DeviceExtension->Started, 0) == 1);
         // failed to start
         DPRINT1("HDA_StartDevice Lower device failed to start %x\n", Status);
         return Status;
@@ -592,11 +596,19 @@ HDA_FDOStartDevice(
     {
         // Get controller into valid state
         Status = HDA_ResetController(DeviceObject);
-        if (!NT_SUCCESS(Status)) return Status;
+        if (!NT_SUCCESS(Status))
+        {
+            NT_VERIFY(InterlockedExchange(&DeviceExtension->Started, 0) == 1);
+            return Status;
+        }
 
         // Setup CORB/RIRB/DMA POS
         Status = HDA_InitCorbRirbPos(DeviceObject);
-        if (!NT_SUCCESS(Status)) return Status;
+        if (!NT_SUCCESS(Status))
+        {
+            NT_VERIFY(InterlockedExchange(&DeviceExtension->Started, 0) == 1);
+            return Status;
+        }
 
 
         // Don't enable codec state change interrupts. We don't handle
@@ -613,6 +625,7 @@ HDA_FDOStartDevice(
 
         Value = READ_REGISTER_USHORT((PUSHORT)(DeviceExtension->RegBase + HDAC_STATE_STATUS));
         if (!Value) {
+            NT_VERIFY(InterlockedExchange(&DeviceExtension->Started, 0) == 1);
             DPRINT1("hda: bad codec status\n");
             return STATUS_UNSUCCESSFUL;
         }
@@ -622,11 +635,26 @@ HDA_FDOStartDevice(
         DPRINT1("Codecs %lx\n", Value);
         for (Index = 0; Index < HDA_MAX_CODECS; Index++) {
             if ((Value & (1 << Index)) != 0) {
-                HDA_InitCodec(DeviceObject, Index);
+                Status = HDA_InitCodec(DeviceObject, Index);
+                if (!NT_SUCCESS(Status))
+                {
+                    DPRINT1("Codec %lu %p initialization failed\n", Index, DeviceExtension->Codecs[Index]);
+                    ASSERTMSG("Codec initialization failed", FALSE);
+                }
             }
         }
+        Status = STATUS_SUCCESS;
     }
 
+    DPRINT1("Device %p started with status %lx\n", DeviceObject, Status);
+    if (NT_SUCCESS(Status))
+    {
+        NT_VERIFY(InterlockedExchange(&DeviceExtension->Started, 2) == 1);
+    }
+    else
+    {
+        NT_VERIFY(InterlockedExchange(&DeviceExtension->Started, 0) == 1);
+    }
     return Status;
 }
 
@@ -644,6 +672,7 @@ HDA_FDOQueryBusRelations(
     /* get device extension */
     DeviceExtension = (PHDA_FDO_DEVICE_EXTENSION)DeviceObject->DeviceExtension;
     ASSERT(DeviceExtension->IsFDO == TRUE);
+    NT_VERIFY(DeviceExtension->Started == 2);
 
     DeviceCount = 0;
     for (CodecIndex = 0; CodecIndex < HDA_MAX_CODECS; CodecIndex++)
@@ -669,14 +698,28 @@ HDA_FDOQueryBusRelations(
             continue;
 
         Codec = DeviceExtension->Codecs[CodecIndex];
+        ASSERT(Codec->AudioGroupCount <= HDA_MAX_AUDIO_GROUPS);
         for (AFGIndex = 0; AFGIndex < Codec->AudioGroupCount; AFGIndex++)
         {
+            if (Codec->AudioGroups[AFGIndex] == NULL)
+            {
+                DPRINT1("Codec %lu %p AudioGroup %lu is NULL\n", CodecIndex, Codec, AFGIndex);
+                ASSERTMSG("AudioGroup is NULL", FALSE);
+            }
+            if (Codec->AudioGroups[AFGIndex]->ChildPDO == NULL)
+            {
+                DPRINT1("Codec %lu %p AudioGroup %lu %p ChildPDO is NULL\n", CodecIndex, Codec, AFGIndex, Codec->AudioGroups[AFGIndex]);
+                ASSERTMSG("ChildPDO is NULL", FALSE);
+            }
+            ASSERT(DeviceRelations->Count < DeviceCount);
             DeviceRelations->Objects[DeviceRelations->Count] = Codec->AudioGroups[AFGIndex]->ChildPDO;
             ObReferenceObject(Codec->AudioGroups[AFGIndex]->ChildPDO);
             DeviceRelations->Count++;
         }
     }
 
+    ASSERT(DeviceRelations->Count == DeviceCount);
+
     /* FIXME handle existing device relations */
     ASSERT(Irp->IoStatus.Information == 0);
 
diff --git a/drivers/wdm/audio/hdaudbus/hdaudbus.cpp b/drivers/wdm/audio/hdaudbus/hdaudbus.cpp
index 9239354c12..b2d81f1c59 100644
--- a/drivers/wdm/audio/hdaudbus/hdaudbus.cpp
+++ b/drivers/wdm/audio/hdaudbus/hdaudbus.cpp
@@ -115,7 +115,31 @@ HDA_Pnp(
             {
                 Status = Irp->IoStatus.Status;
             }
-        } 
+        }
+        else if (IoStack->MinorFunction == IRP_MN_QUERY_STOP_DEVICE)
+        {
+            ASSERTMSG("Device stop not implemented (query)", FALSE);
+        }
+        else if (IoStack->MinorFunction == IRP_MN_CANCEL_STOP_DEVICE)
+        {
+            ASSERTMSG("Device stop not implemented (cancel)", FALSE);
+        }
+        else if (IoStack->MinorFunction == IRP_MN_STOP_DEVICE)
+        {
+            ASSERTMSG("Device stop not implemented", FALSE);
+        }
+        else if (IoStack->MinorFunction == IRP_MN_QUERY_REMOVE_DEVICE)
+        {
+            ASSERTMSG("Device removal not implemented (query)", FALSE);
+        }
+        else if (IoStack->MinorFunction == IRP_MN_CANCEL_REMOVE_DEVICE)
+        {
+            ASSERTMSG("Device removal not implemented (cancel)", FALSE);
+        }
+        else if (IoStack->MinorFunction == IRP_MN_REMOVE_DEVICE)
+        {
+            ASSERTMSG("Device removal not implemented", FALSE);
+        }
         else
         {
             /* get default status */
@@ -238,6 +262,7 @@ IN PDEVICE_OBJECT PhysicalDeviceObject)
     /* init device extension*/
     DeviceExtension->IsFDO = TRUE;
     DeviceExtension->LowerDevice = IoAttachDeviceToDeviceStack(DeviceObject, PhysicalDeviceObject);
+    DeviceExtension->Started = 0;
     RtlZeroMemory(DeviceExtension->Codecs, sizeof(PHDA_CODEC_ENTRY) * (HDA_MAX_CODECS + 1));
 
     /* set device flags */
diff --git a/drivers/wdm/audio/hdaudbus/hdaudbus.h b/drivers/wdm/audio/hdaudbus/hdaudbus.h
index 1496f6de24..ab672e8005 100644
--- a/drivers/wdm/audio/hdaudbus/hdaudbus.h
+++ b/drivers/wdm/audio/hdaudbus/hdaudbus.h
@@ -64,7 +64,7 @@ typedef struct
 {
 	BOOLEAN IsFDO;
 	PDEVICE_OBJECT LowerDevice;
-	
+	LONG Started;
 	PUCHAR RegBase;
 	PKINTERRUPT Interrupt;