APM probing code

APM probing code 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/apm.c

+/* -*- linux-c -*- ------------------------------------------------------- *
+ *
+ *   Copyright (C) 1991, 1992 Linus Torvalds
+ *   Copyright 2007 rPath, Inc. - All Rights Reserved
+ *
+ *   Original APM BIOS checking by Stephen Rothwell, May 1994
+ *   (sfr@canb.auug.org.au)
+ *
+ *   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/apm.c
+ *
+ * Get APM BIOS information
+ */
+
+#include "boot.h"
+
+#if defined(CONFIG_APM) || defined(CONFIG_APM_MODULE)
+
+int query_apm_bios(void)
+{
+	u16 ax, bx, cx, dx, di;
+	u32 ebx, esi;
+	u8 err;
+
+	/* APM BIOS installation check */
+	ax = 0x5300;
+	bx = cx = 0;
+	asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp ; setc %0"
+		     : "=d" (err), "+a" (ax), "+b" (bx), "+c" (cx)
+		     : : "esi", "edi");
+
+	if (err)
+		return -1;		/* No APM BIOS */
+
+	if (bx != 0x504d)	/* "PM" signature */
+		return -1;
+
+	if (cx & 0x02)		/* 32 bits supported? */
+		return -1;
+
+	/* Disconnect first, just in case */
+	ax = 0x5304;
+	asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp"
+		     : "+a" (ax)
+		     : : "ebx", "ecx", "edx", "esi", "edi");
+
+	/* Paranoia */
+	ebx = esi = 0;
+	cx = dx = di = 0;
+
+	/* 32-bit connect */
+	asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp ; setc %6"
+		     : "=a" (ax), "+b" (ebx), "+c" (cx), "+d" (dx),
+		       "+S" (esi), "+D" (di), "=m" (err)
+		     : "a" (0x5303));
+
+	boot_params.apm_bios_info.cseg = ax;
+	boot_params.apm_bios_info.offset = ebx;
+	boot_params.apm_bios_info.cseg_16 = cx;
+	boot_params.apm_bios_info.dseg = dx;
+	boot_params.apm_bios_info.cseg_len = (u16)esi;
+	boot_params.apm_bios_info.cseg_16_len = esi >> 16;
+	boot_params.apm_bios_info.dseg_len = di;
+
+	if (err)
+		return -1;
+
+	/* Redo the installation check as the 32-bit connect;
+	   some BIOSes return different flags this way... */
+
+	ax = 0x5300;
+	bx = cx = 0;
+	asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp ; setc %0"
+		     : "=d" (err), "+a" (ax), "+b" (bx), "+c" (cx)
+		     : : "esi", "edi");
+
+	if (err || bx != 0x504d) {
+		/* Failure with 32-bit connect, try to disconect and ignore */
+		ax = 0x5304;
+		bx = 0;
+		asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp"
+			     : "+a" (ax), "+b" (bx)
+			     : : "ecx", "edx", "esi", "edi");
+		return -1;
+	}
+
+	boot_params.apm_bios_info.version = ax;
+	boot_params.apm_bios_info.flags = cx;
+	return 0;
+}
+
+#endif