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
19 int 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 disconect 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