2 * Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License as
6 * published by the Free Software Foundation; either version 2 of the
7 * License, or any later version.
9 * This program is distributed in the hope that it will be useful, but
10 * WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * General Public License for more details.
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
20 FILE_LICENCE ( GPL2_OR_LATER );
34 /** PnP BIOS structure */
38 * Must be equal to @c PNP_BIOS_SIGNATURE
41 /** Version as BCD (e.g. 1.0 is 0x10) */
43 /** Length of this structure */
45 /** System capabilities */
49 } __attribute__ (( packed ));
51 /** Signature for a PnP BIOS structure */
52 #define PNP_BIOS_SIGNATURE \
53 ( ( '$' << 0 ) + ( 'P' << 8 ) + ( 'n' << 16 ) + ( 'P' << 24 ) )
56 * Test address for PnP BIOS structure
58 * @v offset Offset within BIOS segment to test
59 * @ret rc Return status code
61 static int is_pnp_bios ( unsigned int offset ) {
63 struct pnp_bios pnp_bios;
64 uint8_t bytes[256]; /* 256 is maximum length possible */
70 /* Read start of header and verify signature */
71 copy_from_real ( &u.pnp_bios, BIOS_SEG, offset, sizeof ( u.pnp_bios ));
72 if ( u.pnp_bios.signature != PNP_BIOS_SIGNATURE )
75 /* Read whole header and verify checksum */
76 len = u.pnp_bios.length;
77 copy_from_real ( &u.bytes, BIOS_SEG, offset, len );
78 for ( i = 0 ; i < len ; i++ ) {
84 DBG ( "Found PnP BIOS at %04x:%04x\n", BIOS_SEG, offset );
90 * Locate Plug-and-Play BIOS
92 * @ret pnp_offset Offset of PnP BIOS structure within BIOS segment
94 * The PnP BIOS structure will be at BIOS_SEG:pnp_offset. If no PnP
95 * BIOS is found, -1 is returned.
97 int find_pnp_bios ( void ) {
98 static int pnp_offset = 0;
103 for ( pnp_offset = 0 ; pnp_offset < 0x10000 ; pnp_offset += 0x10 ) {
104 if ( is_pnp_bios ( pnp_offset ) == 0 )