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  *
   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  * arch/i386/boot/apm.c
  16  *
  17  * Get APM BIOS information
  18  */
  19
  20 #include "boot.h"
  21
  22 int query_apm_bios(void)
  23 {
  24         u16 ax, bx, cx, dx, di;
  25         u32 ebx, esi;
  26         u8 err;
  27
  28         /* APM BIOS installation check */
  29         ax = 0x5300;
  30         bx = cx = 0;
  31         asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp ; setc %0"
  32                      : "=d" (err), "+a" (ax), "+b" (bx), "+c" (cx)
  33                      : : "esi", "edi");
  34
  35         if (err)
  36                 return -1;              /* No APM BIOS */
  37
  38         if (bx != 0x504d)       /* "PM" signature */
  39                 return -1;
  40
  41         if (!(cx & 0x02))               /* 32 bits supported? */
  42                 return -1;
  43
  44         /* Disconnect first, just in case */
  45         ax = 0x5304;
  46         bx = 0;
  47         asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp"
  48                      : "+a" (ax), "+b" (bx)
  49                      : : "ecx", "edx", "esi", "edi");
  50
  51         /* Paranoia */
  52         ebx = esi = 0;
  53         cx = dx = di = 0;
  54
  55         /* 32-bit connect */
  56         asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp ; setc %6"
  57                      : "=a" (ax), "+b" (ebx), "+c" (cx), "+d" (dx),
  58                        "+S" (esi), "+D" (di), "=m" (err)
  59                      : "a" (0x5303));
  60
  61         boot_params.apm_bios_info.cseg = ax;
  62         boot_params.apm_bios_info.offset = ebx;
  63         boot_params.apm_bios_info.cseg_16 = cx;
  64         boot_params.apm_bios_info.dseg = dx;
  65         boot_params.apm_bios_info.cseg_len = (u16)esi;
  66         boot_params.apm_bios_info.cseg_16_len = esi >> 16;
  67         boot_params.apm_bios_info.dseg_len = di;
  68
  69         if (err)
  70                 return -1;
  71
  72         /* Redo the installation check as the 32-bit connect;
  73            some BIOSes return different flags this way... */
  74
  75         ax = 0x5300;
  76         bx = cx = 0;
  77         asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp ; setc %0"
  78                      : "=d" (err), "+a" (ax), "+b" (bx), "+c" (cx)
  79                      : : "esi", "edi");
  80
  81         if (err || bx != 0x504d) {
  82                 /* Failure with 32-bit connect, try to disconect and ignore */
  83                 ax = 0x5304;
  84                 bx = 0;
  85                 asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp"
  86                              : "+a" (ax), "+b" (bx)
  87                              : : "ecx", "edx", "esi", "edi");
  88                 return -1;
  89         }
  90
  91         boot_params.apm_bios_info.version = ax;
  92         boot_params.apm_bios_info.flags = cx;
  93         return 0;
  94 }
  95