// SPDX-License-Identifier: GPL-2.0-only
/* -*- 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)
 *
 * ----------------------------------------------------------------------- */

/*
 * 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 disconnect 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;
}