com32/mboot/apm.c

   1 /* ----------------------------------------------------------------------- *
   2  *
   3  *   Copyright 2009 Intel Corporation; author: H. Peter Anvin
   4  *
   5  *   This program is free software; you can redistribute it and/or modify
   6  *   it under the terms of the GNU General Public License as published by
   7  *   the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
   8  *   Boston MA 02110-1301, USA; either version 2 of the License, or
   9  *   (at your option) any later version; incorporated herein by reference.
  10  *
  11  *   Based on code from the Linux kernel:
  12  *
  13  *   Copyright (C) 1991, 1992 Linus Torvalds
  14  *   Copyright 2007 rPath, Inc. - All Rights Reserved
  15  *
  16  *   Original APM BIOS checking by Stephen Rothwell, May 1994
  17  *   (sfr@canb.auug.org.au)
  18  *
  19  *   This file is part of the Linux kernel, and is made available under
  20  *   the terms of the GNU General Public License version 2.
  21  *
  22  * ----------------------------------------------------------------------- */
  23
  24 /*
  25  * apm.c
  26  *
  27  * APM information for Multiboot
  28  */
  29
  30 #include "mboot.h"
  31 #include <com32.h>
  32
  33 void mboot_apm(void)
  34 {
  35     static struct apm_info apm;
  36     com32sys_t ireg, oreg;
  37
  38     memset(&ireg, 0, sizeof ireg);
  39
  40     ireg.eax.w[0] = 0x5300;
  41     __intcall(0x15, &ireg, &oreg);
  42
  43     if (oreg.eflags.l & EFLAGS_CF)
  44         return;                 /* No APM BIOS */
  45
  46     if (oreg.ebx.w[0] != 0x504d)
  47         return;                 /* No "PM" signature */
  48
  49     if (!(oreg.ecx.w[0] & 0x02))
  50         return;                 /* 32 bits not supported */
  51
  52     /* Disconnect first, just in case */
  53     memset(&ireg, 0, sizeof ireg);
  54     ireg.eax.b[0] = 0x04;
  55     __intcall(0x15, &ireg, &oreg);
  56
  57     /* 32-bit connect */
  58     ireg.eax.b[0] = 0x03;
  59     __intcall(0x15, &ireg, &oreg);
  60
  61     apm.cseg = oreg.eax.w[0];
  62     apm.offset = oreg.ebx.l;
  63     apm.cseg_16 = oreg.ecx.w[0];
  64     apm.dseg_16 = oreg.edx.w[0];
  65     apm.cseg_len = oreg.esi.w[0];
  66     apm.cseg_16_len = oreg.esi.w[1];
  67     apm.dseg_16_len = oreg.edi.w[0];
  68
  69     /* Redo the installation check as the 32-bit connect;
  70        some BIOSes return different flags this way... */
  71
  72     memset(&ireg, 0, sizeof ireg);
  73     ireg.eax.b[0] = 0x00;
  74     __intcall(0x15, &ireg, &oreg);
  75
  76     if ((oreg.eflags.l & EFLAGS_CF) || (oreg.ebx.w[0] != 0x504d)) {
  77         /* Failure with 32-bit connect, try to disconect and ignore */
  78         ireg.eax.b[0] = 0x04;
  79         __intcall(0x15, &ireg, NULL);
  80         return;
  81     }
  82
  83     apm.version = oreg.eax.w[0];
  84
  85     mbinfo.apm_table = map_data(&apm, sizeof apm, 4, false);
  86     if (mbinfo.apm_table)
  87         mbinfo.flags |= MB_INFO_APM_TABLE;
  88 }