root/arch/x86/boot/apm.c

DEFINITIONS

1. query_apm_bios

/* -*- 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.
 *
 * ----------------------------------------------------------------------- */

/*
 * Get APM BIOS information
 */

#include "boot.h"

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;
}