1 files changed, 106 insertions, 0 deletions
diff --git a/private/mvdm/xms.486/xmsa20.c b/private/mvdm/xms.486/xmsa20.c
new file mode 100644
index 000000000..d52aa1d48
--- /dev/null
+++ b/private/mvdm/xms.486/xmsa20.c
@@ -0,0 +1,106 @@
+/* xmsa20.c - A20 related XMS routines
+ *
+ * XMSA20
+ *
+ * Modification History:
+ *
+ * Sudeepb 15-May-1991 Created
+ */
+
+#include "xms.h"
+
+#include <xmssvc.h>
+#include <softpc.h>
+
+void sas_enable_20_bit_wrapping(void);
+void sas_disable_20_bit_wrapping(void);
+BOOL sas_twenty_bit_wrapping_enabled(void);
+
+BYTE * pHimemA20State = NULL;
+
+
+/* xmsA20 - Handle A20 requests
+ *
+ *
+ * Entry - Client (AX) 0 - Disable A20
+ *		       1 - Enable A20
+ *		       2 - Query
+ *
+ * Exit
+ *	   SUCCESS
+ *	     Client (AX) = 1
+ *	     if on entry AX=2 Then
+ *		Cleint (AX) =1 means was enabled
+ *		Cleint (AX) =0 means was disabled
+ *
+ *	   FAILURE
+ *	     Client (AX) = 0
+ */
+
+VOID xmsA20 (VOID)
+{
+    int reason;
+
+    reason = getAX();
+
+    setAX(1);
+
+    if (reason == 0)
+	xmsEnableA20Wrapping();
+    else if (reason == 1)
+	    xmsDisableA20Wrapping();
+	 else if (reason == 2) {
+		if (sas_twenty_bit_wrapping_enabled())
+		    setAX(0);
+		setBL(0);
+	      }
+	      else
+		setAX(0);
+}
+// function to enable 1MB wrapping (turn off A20 line)
+VOID xmsEnableA20Wrapping(VOID)
+{
+    sas_enable_20_bit_wrapping();
+    if (pHimemA20State != NULL)
+	*pHimemA20State = 0;
+
+#if 0 // this is not necessay because the intel space(pointed by
+      // HimemA20State) doesn't contain instruction
+      // doesn't contain instruction
+#ifdef MIPS
+	Sim32FlushVDMPointer
+	 (
+	  (((ULONG)pHimemA20State >> 4) << 16) | ((ULONG)pHimemA20State & 0xF),
+	  1,
+	  pHimemA20State,
+	  FALSE
+	 );
+
+#endif
+#endif
+
+}
+
+// function to disable 1MB wrapping(turn on A20 line)
+VOID xmsDisableA20Wrapping(VOID)
+{
+
+    sas_disable_20_bit_wrapping();
+    if (pHimemA20State != NULL)
+	*pHimemA20State = 1;
+#if 0 // this is not necessay because the intel space(pointed by
+      // HimemA20State) doesn't contain instruction
+      // doesn't contain instruction
+#ifdef MIPS
+	Sim32FlushVDMPointer
+	 (
+	  (((ULONG)pHimemA20State >> 4) << 16) | ((ULONG)pHimemA20State & 0xF),
+	  1,
+	  pHimemA20State,
+	  FALSE
+	 );
+
+#endif
+#endif
+
+}