[ros-diffs] [aandrejevic] 67280: [NTVDM] Fix host-to-VGA address translation.

Author: aandrejevic
Date: Sat Apr 18 22:00:44 2015
New Revision: 67280

URL: http://svn.reactos.org/svn/reactos?rev=67280&view=rev
Log:
[NTVDM]
Fix host-to-VGA address translation.

Modified:
    trunk/reactos/subsystems/mvdm/ntvdm/hardware/video/vga.c

Modified: trunk/reactos/subsystems/mvdm/ntvdm/hardware/video/vga.c
URL: http://svn.reactos.org/svn/reactos/trunk/reactos/subsystems/mvdm/ntvdm/hardw...
==============================================================================
--- trunk/reactos/subsystems/mvdm/ntvdm/hardware/video/vga.c	[iso-8859-1] (original)
+++ trunk/reactos/subsystems/mvdm/ntvdm/hardware/video/vga.c	[iso-8859-1] Sat Apr 18 22:00:44 2015
@@ -629,13 +629,13 @@
     {
         /* The lowest two bits are the plane number */
         Plane = Offset & 0x03;
-        Offset >>= 2;
+        Offset &= ~3;
     }
     else if (VgaGcRegisters[VGA_GC_MODE_REG] & VGA_GC_MODE_OE)
     {
         /* The LSB is the plane number */
         Plane = Offset & 0x01;
-        Offset >>= 1;
+        Offset &= ~1;
     }
     else
     {
@@ -643,9 +643,6 @@
         Plane = VgaGcRegisters[VGA_GC_READ_MAP_SEL_REG] & 0x03;
     }

-    /* Multiply the offset by the address size */
-    Offset *= VgaGetAddressSize();
-    
     return Offset + Plane * VGA_BANK_SIZE;
 }

@@ -656,17 +653,14 @@
     /* Check for chain-4 and odd-even mode */
     if (VgaSeqRegisters[VGA_SEQ_MEM_REG] & VGA_SEQ_MEM_C4)
     {
-        /* Shift the offset to the right by 2 */
-        Offset >>= 2;
+        /* Clear the lowest two bits since they're used to select the bank */
+        Offset &= ~3;
     }
     else if (VgaGcRegisters[VGA_GC_MODE_REG] & VGA_GC_MODE_OE)
     {
-        /* Shift the offset to the right by 1 */
-        Offset >>= 1;
-    }
-
-    /* Multiply the offset by the address size */
-    Offset *= VgaGetAddressSize();
+        /* Clear the lowest bit since it's used to select odd/even */
+        Offset &= ~1;
+    }

/* Return the offset on plane 0 */
     return Offset;