1 /* -*- linux-c -*- ------------------------------------------------------- *
2 *
3 * Copyright (C) 1991, 1992 Linus Torvalds
4 * Copyright 2007 rPath, Inc. - All Rights Reserved
5 * Copyright 2009 Intel Corporation; author H. Peter Anvin
6 *
7 * Original APM BIOS checking by Stephen Rothwell, May 1994
8 * (sfr@canb.auug.org.au)
9 *
10 * This file is part of the Linux kernel, and is made available under
11 * the terms of the GNU General Public License version 2.
12 *
13 * ----------------------------------------------------------------------- */
14
15 /*
16 * Get APM BIOS information
17 */
18
19 #include "boot.h"
20
query_apm_bios(void)21 int query_apm_bios(void)
22 {
23 struct biosregs ireg, oreg;
24
25 /* APM BIOS installation check */
26 initregs(&ireg);
27 ireg.ah = 0x53;
28 intcall(0x15, &ireg, &oreg);
29
30 if (oreg.flags & X86_EFLAGS_CF)
31 return -1; /* No APM BIOS */
32
33 if (oreg.bx != 0x504d) /* "PM" signature */
34 return -1;
35
36 if (!(oreg.cx & 0x02)) /* 32 bits supported? */
37 return -1;
38
39 /* Disconnect first, just in case */
40 ireg.al = 0x04;
41 intcall(0x15, &ireg, NULL);
42
43 /* 32-bit connect */
44 ireg.al = 0x03;
45 intcall(0x15, &ireg, &oreg);
46
47 boot_params.apm_bios_info.cseg = oreg.ax;
48 boot_params.apm_bios_info.offset = oreg.ebx;
49 boot_params.apm_bios_info.cseg_16 = oreg.cx;
50 boot_params.apm_bios_info.dseg = oreg.dx;
51 boot_params.apm_bios_info.cseg_len = oreg.si;
52 boot_params.apm_bios_info.cseg_16_len = oreg.hsi;
53 boot_params.apm_bios_info.dseg_len = oreg.di;
54
55 if (oreg.flags & X86_EFLAGS_CF)
56 return -1;
57
58 /* Redo the installation check as the 32-bit connect;
59 some BIOSes return different flags this way... */
60
61 ireg.al = 0x00;
62 intcall(0x15, &ireg, &oreg);
63
64 if ((oreg.eflags & X86_EFLAGS_CF) || oreg.bx != 0x504d) {
65 /* Failure with 32-bit connect, try to disconect and ignore */
66 ireg.al = 0x04;
67 intcall(0x15, &ireg, NULL);
68 return -1;
69 }
70
71 boot_params.apm_bios_info.version = oreg.ax;
72 boot_params.apm_bios_info.flags = oreg.cx;
73 return 0;
74 }
75
76