From 7f81d670e4d1577005e48ee9ca3b8c43d11ddb19 Mon Sep 17 00:00:00 2001
From: Yuri Benditovich <yuri.benditovich@daynix.com>
Date: Fri, 25 Jan 2019 09:48:52 +0200
Subject: [PATCH] qxl-wddm-dod: Load best know defaults for video mode at
 driver's start

Even if initial display resolution is not available at driver start, try
to find it in the registry. Then the driver can prevent black screen
on uninstall/disable also when it was installed on UEFI machine after
the production driver 0.18 which did not report valid video mode.

Signed-off-by: Yuri Benditovich <yuri.benditovich@daynix.com>
Acked-by: Marek Kedzierski <mkedzier@redhat.com>
---
 qxldod/QxlDod.cpp | 37 ++++++++++++++++++++++++++++++++-----
 1 file changed, 32 insertions(+), 5 deletions(-)

diff --git a/qxldod/QxlDod.cpp b/qxldod/QxlDod.cpp
index dea78e2..525cdc3 100755
--- a/qxldod/QxlDod.cpp
+++ b/qxldod/QxlDod.cpp
@@ -5169,6 +5169,37 @@ UINT SpiceFromPixelFormat(D3DDDIFORMAT Format)
     }
 }
 
+// Width and Height values for initial video mode are populated by
+// display class driver upon switch from boot display to operational one.
+// This is not documented and can be changed in future, but
+// present under the same key in Win8.1/Win10/2016/2019
+static void RetrieveDisplayDefaults(DXGK_DISPLAY_INFORMATION& DispInfo)
+{
+    PAGED_CODE();
+    RTL_QUERY_REGISTRY_TABLE QueryTable[3] = {};
+    QueryTable[0].Flags = QueryTable[1].Flags = RTL_QUERY_REGISTRY_DIRECT | RTL_QUERY_REGISTRY_TYPECHECK | RTL_QUERY_REGISTRY_REQUIRED;
+    QueryTable[0].DefaultType = QueryTable[1].DefaultType = REG_DWORD << 24;
+    QueryTable[0].Name = L"Height";
+    QueryTable[0].EntryContext = &DispInfo.Height;
+    QueryTable[1].Name = L"Width";
+    QueryTable[1].EntryContext = &DispInfo.Width;
+
+    NTSTATUS status = RtlQueryRegistryValues(RTL_REGISTRY_CONTROL, L"BGFX", QueryTable, NULL, NULL);
+    if (NT_SUCCESS(status))
+    {
+        DbgPrint(TRACE_LEVEL_INFORMATION, ("%s: %dx%d\n", __FUNCTION__, DispInfo.Width, DispInfo.Height));
+    }
+    else
+    {
+        DbgPrint(TRACE_LEVEL_INFORMATION, ("%s: status = %X\n", __FUNCTION__, status));
+        DispInfo.Width = INITIAL_WIDTH;
+        DispInfo.Height = INITIAL_HEIGHT;
+    }
+    DispInfo.ColorFormat = D3DDDIFMT_X8R8G8B8;
+    DispInfo.Pitch = DispInfo.Width * BPPFromPixelFormat(DispInfo.ColorFormat) / BITS_PER_BYTE;
+    DispInfo.TargetId = DispInfo.AcpiId = 0;
+}
+
 NTSTATUS HwDeviceInterface::AcquireDisplayInfo(DXGK_DISPLAY_INFORMATION& DispInfo)
 {
     PAGED_CODE();
@@ -5188,11 +5219,7 @@ NTSTATUS HwDeviceInterface::AcquireDisplayInfo(DXGK_DISPLAY_INFORMATION& DispInf
     if (DispInfo.Width == 0)
     {
         DbgPrint(TRACE_LEVEL_WARNING, ("QxlDod::AcquireDisplayInfo has zero width!\n"));
-        DispInfo.ColorFormat = D3DDDIFMT_A8R8G8B8;
-        DispInfo.Width = INITIAL_WIDTH;
-        DispInfo.Height = INITIAL_HEIGHT;
-        DispInfo.Pitch = DispInfo.Width * BPPFromPixelFormat(DispInfo.ColorFormat) / BITS_PER_BYTE;
-        DispInfo.TargetId = 0;
+        RetrieveDisplayDefaults(DispInfo);
     }
     return Status;
 }