linux/arch/x86/boot/apm.c
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   1/* -*- linux-c -*- ------------------------------------------------------- *
   2 *
   3 *   Copyright (C) 1991, 1992 Linus Torvalds
   4 *   Copyright 2007 rPath, Inc. - All Rights Reserved
   5 *
   6 *   Original APM BIOS checking by Stephen Rothwell, May 1994
   7 *   (sfr@canb.auug.org.au)
   8 *
   9 *   This file is part of the Linux kernel, and is made available under
  10 *   the terms of the GNU General Public License version 2.
  11 *
  12 * ----------------------------------------------------------------------- */
  13
  14/*
  15 * Get APM BIOS information
  16 */
  17
  18#include "boot.h"
  19
  20int query_apm_bios(void)
  21{
  22        u16 ax, bx, cx, dx, di;
  23        u32 ebx, esi;
  24        u8 err;
  25
  26        /* APM BIOS installation check */
  27        ax = 0x5300;
  28        bx = cx = 0;
  29        asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp ; setc %0"
  30                     : "=d" (err), "+a" (ax), "+b" (bx), "+c" (cx)
  31                     : : "esi", "edi");
  32
  33        if (err)
  34                return -1;              /* No APM BIOS */
  35
  36        if (bx != 0x504d)       /* "PM" signature */
  37                return -1;
  38
  39        if (!(cx & 0x02))               /* 32 bits supported? */
  40                return -1;
  41
  42        /* Disconnect first, just in case */
  43        ax = 0x5304;
  44        bx = 0;
  45        asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp"
  46                     : "+a" (ax), "+b" (bx)
  47                     : : "ecx", "edx", "esi", "edi");
  48
  49        /* Paranoia */
  50        ebx = esi = 0;
  51        cx = dx = di = 0;
  52
  53        /* 32-bit connect */
  54        asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp ; setc %6"
  55                     : "=a" (ax), "+b" (ebx), "+c" (cx), "+d" (dx),
  56                       "+S" (esi), "+D" (di), "=m" (err)
  57                     : "a" (0x5303));
  58
  59        boot_params.apm_bios_info.cseg = ax;
  60        boot_params.apm_bios_info.offset = ebx;
  61        boot_params.apm_bios_info.cseg_16 = cx;
  62        boot_params.apm_bios_info.dseg = dx;
  63        boot_params.apm_bios_info.cseg_len = (u16)esi;
  64        boot_params.apm_bios_info.cseg_16_len = esi >> 16;
  65        boot_params.apm_bios_info.dseg_len = di;
  66
  67        if (err)
  68                return -1;
  69
  70        /* Redo the installation check as the 32-bit connect;
  71           some BIOSes return different flags this way... */
  72
  73        ax = 0x5300;
  74        bx = cx = 0;
  75        asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp ; setc %0"
  76                     : "=d" (err), "+a" (ax), "+b" (bx), "+c" (cx)
  77                     : : "esi", "edi");
  78
  79        if (err || bx != 0x504d) {
  80                /* Failure with 32-bit connect, try to disconect and ignore */
  81                ax = 0x5304;
  82                bx = 0;
  83                asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp"
  84                             : "+a" (ax), "+b" (bx)
  85                             : : "ecx", "edx", "esi", "edi");
  86                return -1;
  87        }
  88
  89        boot_params.apm_bios_info.version = ax;
  90        boot_params.apm_bios_info.flags = cx;
  91        return 0;
  92}
  93
  94