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
  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