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apm.c

/* -*- linux-c -*- ------------------------------------------------------- *
 *
 *   Copyright (C) 1991, 1992 Linus Torvalds
 *   Copyright 2007 rPath, Inc. - All Rights Reserved
 *
 *   Original APM BIOS checking by Stephen Rothwell, May 1994
 *   (sfr@canb.auug.org.au)
 *
 *   This file is part of the Linux kernel, and is made available under
 *   the terms of the GNU General Public License version 2.
 *
 * ----------------------------------------------------------------------- */

/*
 * arch/i386/boot/apm.c
 *
 * Get APM BIOS information
 */

#include "boot.h"

#if defined(CONFIG_APM) || defined(CONFIG_APM_MODULE)

int query_apm_bios(void)
{
      u16 ax, bx, cx, dx, di;
      u32 ebx, esi;
      u8 err;

      /* APM BIOS installation check */
      ax = 0x5300;
      bx = cx = 0;
      asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp ; setc %0"
                 : "=d" (err), "+a" (ax), "+b" (bx), "+c" (cx)
                 : : "esi", "edi");

      if (err)
            return -1;        /* No APM BIOS */

      if (bx != 0x504d) /* "PM" signature */
            return -1;

      if (!(cx & 0x02))       /* 32 bits supported? */
            return -1;

      /* Disconnect first, just in case */
      ax = 0x5304;
      bx = 0;
      asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp"
                 : "+a" (ax), "+b" (bx)
                 : : "ecx", "edx", "esi", "edi");

      /* Paranoia */
      ebx = esi = 0;
      cx = dx = di = 0;

      /* 32-bit connect */
      asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp ; setc %6"
                 : "=a" (ax), "+b" (ebx), "+c" (cx), "+d" (dx),
                   "+S" (esi), "+D" (di), "=m" (err)
                 : "a" (0x5303));

      boot_params.apm_bios_info.cseg = ax;
      boot_params.apm_bios_info.offset = ebx;
      boot_params.apm_bios_info.cseg_16 = cx;
      boot_params.apm_bios_info.dseg = dx;
      boot_params.apm_bios_info.cseg_len = (u16)esi;
      boot_params.apm_bios_info.cseg_16_len = esi >> 16;
      boot_params.apm_bios_info.dseg_len = di;

      if (err)
            return -1;

      /* Redo the installation check as the 32-bit connect;
         some BIOSes return different flags this way... */

      ax = 0x5300;
      bx = cx = 0;
      asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp ; setc %0"
                 : "=d" (err), "+a" (ax), "+b" (bx), "+c" (cx)
                 : : "esi", "edi");

      if (err || bx != 0x504d) {
            /* Failure with 32-bit connect, try to disconect and ignore */
            ax = 0x5304;
            bx = 0;
            asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp"
                       : "+a" (ax), "+b" (bx)
                       : : "ecx", "edx", "esi", "edi");
            return -1;
      }

      boot_params.apm_bios_info.version = ax;
      boot_params.apm_bios_info.flags = cx;
      return 0;
}

#endif

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