arch/i386/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 #if defined(CONFIG_APM) || defined(CONFIG_APM_MODULE)
  23
  24 int query_apm_bios(void)
  25 {
  26         u16 ax, bx, cx, dx, di;
  27         u32 ebx, esi;
  28         u8 err;
  29
  30         /* APM BIOS installation check */
  31         ax = 0x5300;
  32         bx = cx = 0;
  33         asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp ; setc %0"
  34                      : "=d" (err), "+a" (ax), "+b" (bx), "+c" (cx)
  35                      : : "esi", "edi");
  36
  37         if (err)
  38                 return -1;              /* No APM BIOS */
  39
  40         if (bx != 0x504d)       /* "PM" signature */
  41                 return -1;
  42
  43         if (!(cx & 0x02))               /* 32 bits supported? */
  44                 return -1;
  45
  46         /* Disconnect first, just in case */
  47         ax = 0x5304;
  48         asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp"
  49                      : "+a" (ax)
  50                      : : "ebx", "ecx", "edx", "esi", "edi");
  51
  52         /* Paranoia */
  53         ebx = esi = 0;
  54         cx = dx = di = 0;
  55
  56         /* 32-bit connect */
  57         asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp ; setc %6"
  58                      : "=a" (ax), "+b" (ebx), "+c" (cx), "+d" (dx),
  59                        "+S" (esi), "+D" (di), "=m" (err)
  60                      : "a" (0x5303));
  61
  62         boot_params.apm_bios_info.cseg = ax;
  63         boot_params.apm_bios_info.offset = ebx;
  64         boot_params.apm_bios_info.cseg_16 = cx;
  65         boot_params.apm_bios_info.dseg = dx;
  66         boot_params.apm_bios_info.cseg_len = (u16)esi;
  67         boot_params.apm_bios_info.cseg_16_len = esi >> 16;
  68         boot_params.apm_bios_info.dseg_len = di;
  69
  70         if (err)
  71                 return -1;
  72
  73         /* Redo the installation check as the 32-bit connect;
  74            some BIOSes return different flags this way... */
  75
  76         ax = 0x5300;
  77         bx = cx = 0;
  78         asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp ; setc %0"
  79                      : "=d" (err), "+a" (ax), "+b" (bx), "+c" (cx)
  80                      : : "esi", "edi");
  81
  82         if (err || bx != 0x504d) {
  83                 /* Failure with 32-bit connect, try to disconect and ignore */
  84                 ax = 0x5304;
  85                 bx = 0;
  86                 asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp"
  87                              : "+a" (ax), "+b" (bx)
  88                              : : "ecx", "edx", "esi", "edi");
  89                 return -1;
  90         }
  91
  92         boot_params.apm_bios_info.version = ax;
  93         boot_params.apm_bios_info.flags = cx;
  94         return 0;
  95 }
  96
  97 #endif