mirror of
https://github.com/xcat2/xNBA.git
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108 lines
2.6 KiB
C
108 lines
2.6 KiB
C
/*
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* Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include <stdint.h>
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#include <string.h>
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#include <errno.h>
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#include <realmode.h>
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#include <pnpbios.h>
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/** @file
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*
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* PnP BIOS
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*
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*/
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/** PnP BIOS structure */
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struct pnp_bios {
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/** Signature
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*
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* Must be equal to @c PNP_BIOS_SIGNATURE
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*/
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uint32_t signature;
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/** Version as BCD (e.g. 1.0 is 0x10) */
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uint8_t version;
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/** Length of this structure */
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uint8_t length;
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/** System capabilities */
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uint16_t control;
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/** Checksum */
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uint8_t checksum;
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} __attribute__ (( packed ));
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/** Signature for a PnP BIOS structure */
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#define PNP_BIOS_SIGNATURE \
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( ( '$' << 0 ) + ( 'P' << 8 ) + ( 'n' << 16 ) + ( 'P' << 24 ) )
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/**
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* Test address for PnP BIOS structure
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*
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* @v offset Offset within BIOS segment to test
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* @ret rc Return status code
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*/
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static int is_pnp_bios ( unsigned int offset ) {
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union {
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struct pnp_bios pnp_bios;
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uint8_t bytes[256]; /* 256 is maximum length possible */
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} u;
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size_t len;
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unsigned int i;
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uint8_t sum = 0;
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/* Read start of header and verify signature */
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copy_from_real ( &u.pnp_bios, BIOS_SEG, offset, sizeof ( u.pnp_bios ));
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if ( u.pnp_bios.signature != PNP_BIOS_SIGNATURE )
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return -EINVAL;
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/* Read whole header and verify checksum */
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len = u.pnp_bios.length;
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copy_from_real ( &u.bytes, BIOS_SEG, offset, len );
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for ( i = 0 ; i < len ; i++ ) {
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sum += u.bytes[i];
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}
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if ( sum != 0 )
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return -EINVAL;
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DBG ( "Found PnP BIOS at %04x:%04x\n", BIOS_SEG, offset );
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return 0;
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}
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/**
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* Locate Plug-and-Play BIOS
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*
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* @ret pnp_offset Offset of PnP BIOS structure within BIOS segment
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*
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* The PnP BIOS structure will be at BIOS_SEG:pnp_offset. If no PnP
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* BIOS is found, -1 is returned.
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*/
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int find_pnp_bios ( void ) {
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static int pnp_offset = 0;
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if ( pnp_offset )
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return pnp_offset;
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for ( pnp_offset = 0 ; pnp_offset < 0x10000 ; pnp_offset += 0x10 ) {
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if ( is_pnp_bios ( pnp_offset ) == 0 )
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return pnp_offset;
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}
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pnp_offset = -1;
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return pnp_offset;
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}
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