MCA support for new x86 setup code

MCA probing support for the new x86 setup code.  This implements the
same functionality as the assembly version.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/i386/boot/mca.c

+/* -*- linux-c -*- ------------------------------------------------------- *
+ *
+ *   Copyright (C) 1991, 1992 Linus Torvalds
+ *   Copyright 2007 rPath, Inc. - All Rights Reserved
+ *
+ *   This file is part of the Linux kernel, and is made available under
+ *   the terms of the GNU General Public License version 2.
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * arch/i386/boot/mca.c
+ *
+ * Get the MCA system description table
+ */
+
+#include "boot.h"
+
+int query_mca(void)
+{
+	u8 err;
+	u16 es, bx, len;
+
+	asm("pushw %%es ; "
+	    "int $0x15 ; "
+	    "setc %0 ; "
+	    "movw %%es, %1 ; "
+	    "popw %%es"
+	    : "=acdSDm" (err), "=acdSDm" (es), "=b" (bx)
+	    : "a" (0xc000));
+
+	if (err)
+		return -1;	/* No MCA present */
+
+	set_fs(es);
+	len = rdfs16(bx);
+
+	if (len > sizeof(boot_params.sys_desc_table))
+		len = sizeof(boot_params.sys_desc_table);
+
+	copy_from_fs(&boot_params.sys_desc_table, bx, len);
+	return 0;
+}