LXR linux/arch/x86/boot/apm.c

   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
  21int 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