1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
|
/*
* Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of the
* License, or any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
FILE_LICENCE ( GPL2_OR_LATER );
#include <stdint.h>
#include <string.h>
#include <errno.h>
#include <realmode.h>
#include <pnpbios.h>
/** @file
*
* PnP BIOS
*
*/
/** PnP BIOS structure */
struct pnp_bios {
/** Signature
*
* Must be equal to @c PNP_BIOS_SIGNATURE
*/
uint32_t signature;
/** Version as BCD (e.g. 1.0 is 0x10) */
uint8_t version;
/** Length of this structure */
uint8_t length;
/** System capabilities */
uint16_t control;
/** Checksum */
uint8_t checksum;
} __attribute__ (( packed ));
/** Signature for a PnP BIOS structure */
#define PNP_BIOS_SIGNATURE \
( ( '$' << 0 ) + ( 'P' << 8 ) + ( 'n' << 16 ) + ( 'P' << 24 ) )
/**
* Test address for PnP BIOS structure
*
* @v offset Offset within BIOS segment to test
* @ret rc Return status code
*/
static int is_pnp_bios ( unsigned int offset ) {
union {
struct pnp_bios pnp_bios;
uint8_t bytes[256]; /* 256 is maximum length possible */
} u;
size_t len;
unsigned int i;
uint8_t sum = 0;
/* Read start of header and verify signature */
copy_from_real ( &u.pnp_bios, BIOS_SEG, offset, sizeof ( u.pnp_bios ));
if ( u.pnp_bios.signature != PNP_BIOS_SIGNATURE )
return -EINVAL;
/* Read whole header and verify checksum */
len = u.pnp_bios.length;
copy_from_real ( &u.bytes, BIOS_SEG, offset, len );
for ( i = 0 ; i < len ; i++ ) {
sum += u.bytes[i];
}
if ( sum != 0 )
return -EINVAL;
DBG ( "Found PnP BIOS at %04x:%04x\n", BIOS_SEG, offset );
return 0;
}
/**
* Locate Plug-and-Play BIOS
*
* @ret pnp_offset Offset of PnP BIOS structure within BIOS segment
*
* The PnP BIOS structure will be at BIOS_SEG:pnp_offset. If no PnP
* BIOS is found, -1 is returned.
*/
int find_pnp_bios ( void ) {
static int pnp_offset = 0;
if ( pnp_offset )
return pnp_offset;
for ( pnp_offset = 0 ; pnp_offset < 0x10000 ; pnp_offset += 0x10 ) {
if ( is_pnp_bios ( pnp_offset ) == 0 )
return pnp_offset;
}
pnp_offset = -1;
return pnp_offset;
}
|
