// SPDX-License-Identifier: GPL-2.0-only
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/* -*- linux-c -*- ------------------------------------------------------- *
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*
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* Copyright (C) 1991, 1992 Linus Torvalds
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* Copyright 2007 rPath, Inc. - All Rights Reserved
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* Copyright 2009 Intel Corporation; author H. Peter Anvin
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*
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* Original APM BIOS checking by Stephen Rothwell, May 1994
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* (sfr@canb.auug.org.au)
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*
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* ----------------------------------------------------------------------- */
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/*
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* Get APM BIOS information
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*/
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#include "boot.h"
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int query_apm_bios(void)
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{
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struct biosregs ireg, oreg;
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/* APM BIOS installation check */
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initregs(&ireg);
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ireg.ah = 0x53;
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intcall(0x15, &ireg, &oreg);
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if (oreg.flags & X86_EFLAGS_CF)
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return -1; /* No APM BIOS */
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if (oreg.bx != 0x504d) /* "PM" signature */
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return -1;
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if (!(oreg.cx & 0x02)) /* 32 bits supported? */
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return -1;
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/* Disconnect first, just in case */
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ireg.al = 0x04;
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intcall(0x15, &ireg, NULL);
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/* 32-bit connect */
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ireg.al = 0x03;
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intcall(0x15, &ireg, &oreg);
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boot_params.apm_bios_info.cseg = oreg.ax;
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boot_params.apm_bios_info.offset = oreg.ebx;
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boot_params.apm_bios_info.cseg_16 = oreg.cx;
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boot_params.apm_bios_info.dseg = oreg.dx;
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boot_params.apm_bios_info.cseg_len = oreg.si;
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boot_params.apm_bios_info.cseg_16_len = oreg.hsi;
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boot_params.apm_bios_info.dseg_len = oreg.di;
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if (oreg.flags & X86_EFLAGS_CF)
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return -1;
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/* Redo the installation check as the 32-bit connect;
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some BIOSes return different flags this way... */
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ireg.al = 0x00;
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intcall(0x15, &ireg, &oreg);
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if ((oreg.eflags & X86_EFLAGS_CF) || oreg.bx != 0x504d) {
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/* Failure with 32-bit connect, try to disconnect and ignore */
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ireg.al = 0x04;
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intcall(0x15, &ireg, NULL);
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return -1;
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}
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boot_params.apm_bios_info.version = oreg.ax;
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boot_params.apm_bios_info.flags = oreg.cx;
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return 0;
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}
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