1 /******************************************************************************
3 * Module Name: tbxfroot - Find the root ACPI table (RSDT)
6 *****************************************************************************/
9 * Copyright (C) 2000 R. Byron Moore
11 * This program is free software; you can redistribute it and/or modify
12 * it under the terms of the GNU General Public License as published by
13 * the Free Software Foundation; either version 2 of the License, or
14 * (at your option) any later version.
16 * This program is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 * GNU General Public License for more details.
21 * You should have received a copy of the GNU General Public License
22 * along with this program; if not, write to the Free Software
23 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
32 #define _COMPONENT TABLE_MANAGER
33 MODULE_NAME ("tbxfroot")
35 #define RSDP_CHECKSUM_LENGTH 20
38 /*******************************************************************************
40 * FUNCTION: Acpi_find_root_pointer
42 * PARAMETERS: **Rsdp_physical_address - Where to place the RSDP address
44 * RETURN: Status, Physical address of the RSDP
46 * DESCRIPTION: Find the RSDP
48 ******************************************************************************/
51 acpi_find_root_pointer (
52 ACPI_PHYSICAL_ADDRESS
*rsdp_physical_address
)
54 ACPI_TABLE_DESC table_info
;
60 status
= acpi_tb_find_rsdp (&table_info
);
61 if (ACPI_FAILURE (status
)) {
62 return (AE_NO_ACPI_TABLES
);
65 *rsdp_physical_address
= table_info
.physical_address
;
71 /*******************************************************************************
73 * FUNCTION: Acpi_tb_scan_memory_for_rsdp
75 * PARAMETERS: Start_address - Starting pointer for search
76 * Length - Maximum length to search
78 * RETURN: Pointer to the RSDP if found, otherwise NULL.
80 * DESCRIPTION: Search a block of memory for the RSDP signature
82 ******************************************************************************/
85 acpi_tb_scan_memory_for_rsdp (
93 /* Search from given start addr for the requested length */
95 for (offset
= 0, mem_rover
= start_address
;
97 offset
+= RSDP_SCAN_STEP
, mem_rover
+= RSDP_SCAN_STEP
)
100 /* The signature and checksum must both be correct */
102 if (STRNCMP ((NATIVE_CHAR
*) mem_rover
,
103 RSDP_SIG
, sizeof (RSDP_SIG
)-1) == 0 &&
104 acpi_tb_checksum (mem_rover
, RSDP_CHECKSUM_LENGTH
) == 0)
106 /* If so, we have found the RSDP */
112 /* Searched entire block, no RSDP was found */
118 /*******************************************************************************
120 * FUNCTION: Acpi_tb_find_rsdp
122 * PARAMETERS: *Buffer_ptr - If == NULL, read data from buffer
123 * rather than searching memory
124 * *Table_info - Where the table info is returned
128 * DESCRIPTION: Search lower 1_mbyte of memory for the root system descriptor
129 * pointer structure. If it is found, set *RSDP to point to it.
131 * NOTE: The RSDP must be either in the first 1_k of the Extended
132 * BIOS Data Area or between E0000 and FFFFF (ACPI 1.0 section
133 * 5.2.2; assertion #421).
135 ******************************************************************************/
139 ACPI_TABLE_DESC
*table_info
)
144 ACPI_STATUS status
= AE_OK
;
148 * Search memory for RSDP. First map low physical memory.
151 status
= acpi_os_map_memory (LO_RSDP_WINDOW_BASE
, LO_RSDP_WINDOW_SIZE
,
152 (void **)&table_ptr
);
154 if (ACPI_FAILURE (status
)) {
159 * 1) Search EBDA (low memory) paragraphs
162 mem_rover
= acpi_tb_scan_memory_for_rsdp (table_ptr
, LO_RSDP_WINDOW_SIZE
);
164 /* This mapping is no longer needed */
166 acpi_os_unmap_memory (table_ptr
, LO_RSDP_WINDOW_SIZE
);
169 /* Found it, return the physical address */
171 phys_addr
= LO_RSDP_WINDOW_BASE
;
172 phys_addr
+= (mem_rover
- table_ptr
);
174 table_info
->physical_address
= phys_addr
;
181 * 2) Search upper memory: 16-byte boundaries in E0000h-F0000h
184 status
= acpi_os_map_memory (HI_RSDP_WINDOW_BASE
, HI_RSDP_WINDOW_SIZE
,
185 (void **)&table_ptr
);
187 if (ACPI_FAILURE (status
)) {
191 mem_rover
= acpi_tb_scan_memory_for_rsdp (table_ptr
, HI_RSDP_WINDOW_SIZE
);
193 /* This mapping is no longer needed */
195 acpi_os_unmap_memory (table_ptr
, HI_RSDP_WINDOW_SIZE
);
198 /* Found it, return the physical address */
200 phys_addr
= HI_RSDP_WINDOW_BASE
;
201 phys_addr
+= (mem_rover
- table_ptr
);
203 table_info
->physical_address
= phys_addr
;
209 /* RSDP signature was not found */
211 return (AE_NOT_FOUND
);