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  * Get APM BIOS information
  16  */
  17
  18 #include "boot.h"
  19
  20 int 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