1 files changed, 73 insertions, 0 deletions
diff --git a/arch/x86/boot/apm.c b/arch/x86/boot/apm.c
new file mode 100644
index 0000000000..bda15f9673
--- /dev/null
+++ b/arch/x86/boot/apm.c
@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* -*- linux-c -*- ------------------------------------------------------- *
+ *
+ *   Copyright (C) 1991, 1992 Linus Torvalds
+ *   Copyright 2007 rPath, Inc. - All Rights Reserved
+ *   Copyright 2009 Intel Corporation; author H. Peter Anvin
+ *
+ *   Original APM BIOS checking by Stephen Rothwell, May 1994
+ *   (sfr@canb.auug.org.au)
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * Get APM BIOS information
+ */
+
+#include "boot.h"
+
+int query_apm_bios(void)
+{
+	struct biosregs ireg, oreg;
+
+	/* APM BIOS installation check */
+	initregs(&ireg);
+	ireg.ah = 0x53;
+	intcall(0x15, &ireg, &oreg);
+
+	if (oreg.flags & X86_EFLAGS_CF)
+		return -1;		/* No APM BIOS */
+
+	if (oreg.bx != 0x504d)		/* "PM" signature */
+		return -1;
+
+	if (!(oreg.cx & 0x02))		/* 32 bits supported? */
+		return -1;
+
+	/* Disconnect first, just in case */
+	ireg.al = 0x04;
+	intcall(0x15, &ireg, NULL);
+
+	/* 32-bit connect */
+	ireg.al = 0x03;
+	intcall(0x15, &ireg, &oreg);
+
+	boot_params.apm_bios_info.cseg        = oreg.ax;
+	boot_params.apm_bios_info.offset      = oreg.ebx;
+	boot_params.apm_bios_info.cseg_16     = oreg.cx;
+	boot_params.apm_bios_info.dseg        = oreg.dx;
+	boot_params.apm_bios_info.cseg_len    = oreg.si;
+	boot_params.apm_bios_info.cseg_16_len = oreg.hsi;
+	boot_params.apm_bios_info.dseg_len    = oreg.di;
+
+	if (oreg.flags & X86_EFLAGS_CF)
+		return -1;
+
+	/* Redo the installation check as the 32-bit connect;
+	   some BIOSes return different flags this way... */
+
+	ireg.al = 0x00;
+	intcall(0x15, &ireg, &oreg);
+
+	if ((oreg.eflags & X86_EFLAGS_CF) || oreg.bx != 0x504d) {
+		/* Failure with 32-bit connect, try to disconnect and ignore */
+		ireg.al = 0x04;
+		intcall(0x15, &ireg, NULL);
+		return -1;
+	}
+
+	boot_params.apm_bios_info.version = oreg.ax;
+	boot_params.apm_bios_info.flags   = oreg.cx;
+	return 0;
+}
+