--- /dev/null 2004-11-18 01:04:18.509511472 +0100
+++ linux-2.6.9/Documentation/dsdt-initrd.txt 2004-11-20 11:37:34.856629896 +0100
@@ -0,0 +1,48 @@
+ACPI Custom DSDT read from initrd
+
+2003 by Markuss Gaugusch < dsdt at gaugusch dot org >
+Special thanks go to Thomas Renninger from SuSE, who updated the patch for 2.6.0
+2004 maintained by Eric Piel < eric dot piel at tremplin-utc dot net >
+
+This option is intended for people who like to hack their DSDT and don't want
+to recompile their kernel after every change. It can also be useful to distros
+which offers pre-compiled kernels and want to allow their users to use a
+modified DSDT. In the Kernel config, enable the ramdisk (not as module!) and initrd
+(in Block Devices) and enable ACPI_CUSTOM_DSDT_INITRD at the ACPI
+options (General Setup|ACPI Support|Read custom DSDT from initrd).
+
+A custom DSDT (Differentiated System Description Table) is useful when your
+computer uses ACPI but problems occurs due to broken implementation. Typically,
+your computer works but there are some troubles with the hardware detection or
+the power management. You can check that troubles come from errors in the DSDT by
+activating the ACPI debug option and reading the logs. This table is provided
+by the BIOS, therefore it might be a good idea to check for BIOS update on your
+vendor website before going any further. Errors are often caused by vendors
+testing their hardware only with Windows or because there is code which is
+executed only on a specific OS with a specific version and Linux hasn't been
+considered during the development.
+
+Before you run away from customising your DSDT, you should note that already
+corrected tables are available for a fair amount of computers on this web-page:
+http://acpi.sf.net/dsdt . If you are part of the unluckies who cannot find
+their hardware in this database, you can modify your DSDT by yourself. This
+process is less painful than it sounds. Download the Intel ASL
+compiler/decompiler at http://www.intel.com/technology/IAPC/acpi/downloads.htm .
+As root, you then have to dump your DSDT and decompile it. By using the
+compiler messages as well as the kernel ACPI debug messages and the reference book
+(available at the Intel website and also at http://www.acpi.info), it is quite
+easy to obtain a fully working table.
+
+Once your new DSDT is ready you'll have to add it to an initrd so that the
+kernel can read the table at the very beginning of the boot. If you don't have
+any initrd yet, you can just specify the table as an initrd file (in lilo or
+grub) and it will work. Otherwise you have to separate the DSDT from the rest
+by a signature. Do it like it:
+echo -n "INITRDDSDT123DSDT123" >> /boot/initrd #magic signature
+cat DSDT.aml >> /boot/initrd
+
+The message "Looking for DSDT in initrd..." will tell you if the DSDT was
+found or not. If you need to update your DSDT, generate a new initrd and
+perform the steps above.
+
+
--- linux-2.6.9.orig/drivers/acpi/osl.c 2004-10-18 23:54:55.000000000 +0200
+++ linux-2.6.9/drivers/acpi/osl.c 2004-11-20 11:14:22.000000000 +0100
@@ -34,6 +34,7 @@
#include <linux/interrupt.h>
#include <linux/kmod.h>
#include <linux/delay.h>
+#include <linux/initrd.h>
#include <linux/workqueue.h>
#include <linux/nmi.h>
#include <acpi/acpi.h>
@@ -237,6 +238,43 @@ acpi_os_predefined_override (const struc
return AE_OK;
}
+#ifdef CONFIG_ACPI_CUSTOM_DSDT_INITRD
+struct acpi_table_header * acpi_find_dsdt_initrd(void)
+{
+ unsigned char start_signature[] = "INITRDDSDT123DSDT123";
+ unsigned char *data = (unsigned char*)initrd_start;
+ unsigned char *dsdt_start = NULL;
+
+ if (!initrd_start)
+ return NULL;
+
+ printk(KERN_INFO PREFIX "Looking for DSDT in initrd...");
+ if ((initrd_end - initrd_start) > 4 &&
+ !strncmp((unsigned char*)initrd_start, "DSDT", 4))
+ /* found DSDT at start of initrd */
+ dsdt_start = (unsigned char*)initrd_start;
+ else { /* searching for start signature in initrd */
+ for (; data < (unsigned char*)initrd_end; data++) {
+ if (!strncmp(data, start_signature,
+ sizeof(start_signature) - 1)) {
+ dsdt_start = data + sizeof(start_signature) - 1;
+ break;
+ }
+ }
+ }
+ /* check if head of dsdt is valid */
+ if (dsdt_start && !strncmp(dsdt_start, "DSDT", 4)) {
+ printk(" found (at offset 0x%02x).\n",
+ (unsigned int) (dsdt_start - (unsigned char*)initrd_start));
+ return (struct acpi_table_header*)dsdt_start;
+ } else
+ printk(" not found.\n");
+
+ /* no DSDT found */
+ return NULL;
+}
+#endif
+
acpi_status
acpi_os_table_override (struct acpi_table_header *existing_table,
struct acpi_table_header **new_table)
@@ -244,13 +282,18 @@ acpi_os_table_override (struct acpi_tabl
if (!existing_table || !new_table)
return AE_BAD_PARAMETER;
+ *new_table = NULL;
+
#ifdef CONFIG_ACPI_CUSTOM_DSDT
if (strncmp(existing_table->signature, "DSDT", 4) == 0)
*new_table = (struct acpi_table_header*)AmlCode;
- else
- *new_table = NULL;
-#else
- *new_table = NULL;
+#endif
+#ifdef CONFIG_ACPI_CUSTOM_DSDT_INITRD
+ if (strncmp(existing_table->signature, "DSDT", 4) == 0) {
+ struct acpi_table_header* initrd_table = acpi_find_dsdt_initrd();
+ if (initrd_table)
+ *new_table = initrd_table;
+ }
#endif
return AE_OK;
}
--- linux-2.6.9.orig/drivers/acpi/Kconfig 2004-10-18 23:55:29.000000000 +0200
+++ linux-2.6.9/drivers/acpi/Kconfig 2004-11-09 23:38:28.000000000 +0100
@@ -219,6 +219,23 @@ config ACPI_CUSTOM_DSDT_FILE
help
Enter the full path name to the file wich includes the AmlCode declaration.
+config ACPI_CUSTOM_DSDT_INITRD
+ bool "Read Custom DSDT from initrd"
+ depends on X86
+ depends on ACPI_INTERPRETER
+ depends on BLK_DEV_INITRD
+ default y
+ help
+ The DSDT (Differentiated System Description Table) often needs to be
+ overridden because of broken BIOS implementations. If you want to use
+ a customized DSDT, please use the mkinitrd tool (mkinitrd package) to
+ attach the DSDT to the initrd. For more details see
+ file:Documentation/dsdt-initrd.txt . If there is no table found in the
+ initrd, the DSDT from the BIOS is used.
+
+ Even if you do not need a new one at the moment, you may want to use a
+ better implemented DSDT later. It is safe to say Y here.
+
config ACPI_BLACKLIST_YEAR
int "Disable ACPI for systems before Jan 1st this year"
default 0