Re: Patch for boot for enabling gate A20 with BIOS

[Giuseppe Magnotta]

Sorry,

it seems that the patch was not included in my last email.

Here is the patch:

Index: gateA20.c
===================================================================
RCS file: /cvs/src/sys/arch/i386/stand/libsa/gateA20.c,v
retrieving revision 1.10
diff -u -r1.10 gateA20.c
--- gateA20.c   19 Mar 2004 13:48:18 -0000      1.10
+++ gateA20.c   1 Mar 2010 14:27:58 -0000
@@ -41,6 +41,31 @@
                                           enable data line
                                           enable clock line */
 
+/*
+ * Author: Giuseppe Magnotta <giuseppe.magno...@gmail.com>
+ *
+ * Enable the gate A20 by using the INT 15/AX=2401h if the
+ * BIOS supports it.
+ *
+ * Returns 0 if ok or the error code fetched from AH register.
+ */
+static __inline int
+enableA20Gate(void)
+{
+       char status;
+       short r;
+
+       __asm __volatile(DOINT(0x15) "\n\t"
+                        "setc %1\n\t"
+                        : "=a" (r), "=r" (status)
+                        : "0" (0x2401)
+                        : "cc");
+
+       if (status)
+               return (r >> 8);
+       else
+               return 0;
+}
 
 /*
  * "Probe"-style routine (no parameters) to turn A20 on
@@ -58,7 +83,9 @@
 void
 gateA20(int on)
 {
-       if (ps2model == 0xf82 ||
+       if (enableA20Gate() == 0) {
+               /* gate A20 enabled! */
+       } else if (ps2model == 0xf82 ||
            (inb(IO_KBD + KBSTATP) == 0xff && inb(IO_KBD + KBDATAP) == 0xff))
{
                int data;