apm.c
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/* -*- linux-c -*- ------------------------------------------------------- *
*
* Copyright (C) 1991, 1992 Linus Torvalds
* Copyright 2007 rPath, Inc. - All Rights Reserved
* Copyright 2009 Intel Corporation; author H. Peter Anvin
*
* 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)
{
struct biosregs ireg, oreg;
/* APM BIOS installation check */
initregs(&ireg);
ireg.ah = 0x53;
intcall(0x15, &ireg, &oreg);
if (oreg.flags & X86_EFLAGS_CF)
return -1; /* No APM BIOS */
if (oreg.bx != 0x504d) /* "PM" signature */
return -1;
if (!(oreg.cx & 0x02)) /* 32 bits supported? */
return -1;
/* Disconnect first, just in case */
ireg.al = 0x04;
intcall(0x15, &ireg, NULL);
/* 32-bit connect */
ireg.al = 0x03;
intcall(0x15, &ireg, &oreg);
boot_params.apm_bios_info.cseg = oreg.ax;
boot_params.apm_bios_info.offset = oreg.ebx;
boot_params.apm_bios_info.cseg_16 = oreg.cx;
boot_params.apm_bios_info.dseg = oreg.dx;
boot_params.apm_bios_info.cseg_len = oreg.si;
boot_params.apm_bios_info.cseg_16_len = oreg.hsi;
boot_params.apm_bios_info.dseg_len = oreg.di;
if (oreg.flags & X86_EFLAGS_CF)
return -1;
/* Redo the installation check as the 32-bit connect;
some BIOSes return different flags this way... */
ireg.al = 0x00;
intcall(0x15, &ireg, &oreg);
if ((oreg.eflags & X86_EFLAGS_CF) || oreg.bx != 0x504d) {
/* Failure with 32-bit connect, try to disconect and ignore */
ireg.al = 0x04;
intcall(0x15, &ireg, NULL);
return -1;
}
boot_params.apm_bios_info.version = oreg.ax;
boot_params.apm_bios_info.flags = oreg.cx;
return 0;
}