1// SPDX-License-Identifier: GPL-2.0-only
2/* -*- linux-c -*- ------------------------------------------------------- *
3 *
4 *   Copyright (C) 1991, 1992 Linus Torvalds
5 *   Copyright 2007 rPath, Inc. - All Rights Reserved
6 *   Copyright 2009 Intel Corporation; author H. Peter Anvin
7 *
8 *   Original APM BIOS checking by Stephen Rothwell, May 1994
9 *   (sfr@canb.auug.org.au)
10 *
11 * ----------------------------------------------------------------------- */
12
13/*
14 * Get APM BIOS information
15 */
16
17#include "boot.h"
18
19int query_apm_bios(void)
20{
21	struct biosregs ireg, oreg;
22
23	/* APM BIOS installation check */
24	initregs(&ireg);
25	ireg.ah = 0x53;
26	intcall(0x15, &ireg, &oreg);
27
28	if (oreg.flags & X86_EFLAGS_CF)
29		return -1;		/* No APM BIOS */
30
31	if (oreg.bx != 0x504d)		/* "PM" signature */
32		return -1;
33
34	if (!(oreg.cx & 0x02))		/* 32 bits supported? */
35		return -1;
36
37	/* Disconnect first, just in case */
38	ireg.al = 0x04;
39	intcall(0x15, &ireg, NULL);
40
41	/* 32-bit connect */
42	ireg.al = 0x03;
43	intcall(0x15, &ireg, &oreg);
44
45	boot_params.apm_bios_info.cseg        = oreg.ax;
46	boot_params.apm_bios_info.offset      = oreg.ebx;
47	boot_params.apm_bios_info.cseg_16     = oreg.cx;
48	boot_params.apm_bios_info.dseg        = oreg.dx;
49	boot_params.apm_bios_info.cseg_len    = oreg.si;
50	boot_params.apm_bios_info.cseg_16_len = oreg.hsi;
51	boot_params.apm_bios_info.dseg_len    = oreg.di;
52
53	if (oreg.flags & X86_EFLAGS_CF)
54		return -1;
55
56	/* Redo the installation check as the 32-bit connect;
57	   some BIOSes return different flags this way... */
58
59	ireg.al = 0x00;
60	intcall(0x15, &ireg, &oreg);
61
62	if ((oreg.eflags & X86_EFLAGS_CF) || oreg.bx != 0x504d) {
63		/* Failure with 32-bit connect, try to disconnect and ignore */
64		ireg.al = 0x04;
65		intcall(0x15, &ireg, NULL);
66		return -1;
67	}
68
69	boot_params.apm_bios_info.version = oreg.ax;
70	boot_params.apm_bios_info.flags   = oreg.cx;
71	return 0;
72}
73
74