Author: Len Brown <[EMAIL PROTECTED]>
AuthorDate: Wed Feb 6 19:28:02 2008 -0500
Committer: Len Brown <[EMAIL PROTECTED]>
CommitDate: Thu Feb 7 04:00:38 2008 -0500
ACPI: update DSDT override documentation
Signed-off-by: Len Brown <[EMAIL PROTECTED]>
Documentation/acpi/dsdt-initrd.txt | 99 ------------------------------
Documentation/acpi/dsdt-override.txt | 15 +++++
Documentation/acpi/initramfs-add-dsdt.sh | 43 +++++++++++++
drivers/acpi/Kconfig | 22 +++----
4 files changed, 67 insertions(+), 112 deletions(-)
diff --git a/Documentation/acpi/dsdt-initrd.txt
deleted file mode 100644
@@ -1,99 +0,0 @@
-ACPI Custom DSDT read from initramfs
-2003 by Markus Gaugusch < dsdt at gaugusch dot at >
-Special thanks go to Thomas Renninger from SuSE, who updated the patch for
-2.6.0 and later modified it to read inside initramfs
-2004 - 2008 maintained by Eric Piel < eric dot piel at tremplin-utc dot net >
-This option is intended for people who would 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 initial RAM filesystem
-support (in General Setup) and enable ACPI_CUSTOM_DSDT_INITRD at the ACPI
-options (General Setup|ACPI Support|Read Custom DSDT from initramfs).
-A custom DSDT (Differentiated System Description Table) is useful when your
-computer uses ACPI but problems occur 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
-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 . Be careful though, to work correctly a DSDT has to
-match closely the hardware, including the amount of RAM, the frequency of the
-processor and the PCI cards present! 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 initramfs so that the
-kernel can read the table at the very beginning of the boot. As the file has to
-be accessed very early during the boot process the initramfs has to be an
-initramfs. The file is contained into the initramfs under the name /DSDT.aml .
-To obtain such an initramfs, you might have to modify your initramfs script or
-you can add it later to the initramfs with the script appended to this
-document. The command will look like:
-initramfs-add-dsdt initramfs.img my-dsdt.aml
-In case you don't use any initramfs, the possibilities you have are to either
-start using one (try mkinitrd or yaird), or use the "Include Custom DSDT"
-configure option to directly include your DSDT inside the kernel.
-The message "Looking for DSDT in initramfs..." will tell you if the DSDT was
-found or not. If you need to update your DSDT, generate a new initramfs and
-perform the steps above. Don't forget that with Lilo, you'll have to re-run it.
-====================== Here starts initramfs-add-dsdt
-# Adds a DSDT file to the initrd (if it's an initramfs)
-# first argument is the name of archive
-# second argument is the name of the file to add
-# The file will be copied as /DSDT.aml
-# 20060126: fix "Premature end of file" with some old cpio (Roland Robic)
-# 20060205: this time it should really work
-# check the arguments
-if [ $# -ne 2 ]; then
- program_name=$(basename $0)
- echo "\
-$program_name: too few arguments
-Usage: $program_name initrd-name.img DSDT-to-add.aml
-Adds a DSDT file to an initrd (in initramfs format)
- initrd-name.img: filename of the initrd in initramfs format
- DSDT-to-add.aml: filename of the DSDT file to add
- " 1>&2
- exit 1
-# we should check it's an initramfs
-# cleanup on exit, hangup, interrupt, quit, termination
-trap 'rm -rf $tempcpio' 0 1 2 3 15
-# extract the archive
-gunzip -c "$1" > "$tempcpio"/initramfs.cpio || exit 1
-# copy the DSDT file at the root of the directory so that we can call it
-cp -f "$2" "$tempcpio"/DSDT.aml
-# add the file
-(echo DSDT.aml | cpio --quiet -H newc -o -A -O "$tempcpio"/initramfs.cpio) ||
-# re-compress the archive
-gzip -c "$tempcpio"/initramfs.cpio > "$1"
diff --git a/Documentation/acpi/dsdt-override.txt
new file mode 100644
@@ -0,0 +1,15 @@
+Linux supports two methods of overriding the BIOS DSDT:
+CONFIG_ACPI_CUSTOM_DSDT builds the image into the kernel.
+CONFIG_ACPI_CUSTOM_DSDT_INITRD adds the image to the initrd.
+When to use these methods is described in detail on the
+Linux/ACPI home page:
+Note that if both options are used, the DSDT supplied
+by the INITRD method takes precedence.
+Documentation/initramfs-add-dsdt.sh is provided for convenience
+for use with the CONFIG_ACPI_CUSTOM_DSDT_INITRD method.
diff --git a/Documentation/acpi/initramfs-add-dsdt.sh
new file mode 100755
@@ -0,0 +1,43 @@
+# Adds a DSDT file to the initrd (if it's an initramfs)
+# first argument is the name of archive
+# second argument is the name of the file to add
+# The file will be copied as /DSDT.aml
+# 20060126: fix "Premature end of file" with some old cpio (Roland Robic)
+# 20060205: this time it should really work
+# check the arguments
+if [ $# -ne 2 ]; then
+ program_name=$(basename $0)
+ echo "\
+$program_name: too few arguments
+Usage: $program_name initrd-name.img DSDT-to-add.aml
+Adds a DSDT file to an initrd (in initramfs format)
+ initrd-name.img: filename of the initrd in initramfs format
+ DSDT-to-add.aml: filename of the DSDT file to add
+ " 1>&2
+ exit 1
+# we should check it's an initramfs
+# cleanup on exit, hangup, interrupt, quit, termination
+trap 'rm -rf $tempcpio' 0 1 2 3 15
+# extract the archive
+gunzip -c "$1" > "$tempcpio"/initramfs.cpio || exit 1
+# copy the DSDT file at the root of the directory so that we can call it
+cp -f "$2" "$tempcpio"/DSDT.aml
+# add the file
+(echo DSDT.aml | cpio --quiet -H newc -o -A -O "$tempcpio"/initramfs.cpio) ||
+# re-compress the archive
+gzip -c "$tempcpio"/initramfs.cpio > "$1"
diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
index 0442ae1..c8e8320 100644
@@ -263,8 +263,10 @@ config ACPI_CUSTOM_DSDT
depends on !STANDALONE
- This option is to load a custom ACPI DSDT
- If you don't know what that is, say N.
+ This option supports a custom DSDT by linking it into the kernel.
+ See Documentation/acpi/dsdt-override.txt
+ If unsure, say N.
string "Custom DSDT Table file to include"
@@ -279,17 +281,11 @@ config ACPI_CUSTOM_DSDT_INITRD
depends on BLK_DEV_INITRD
- The DSDT (Differentiated System Description Table) often needs to be
- overridden because of broken BIOS implementations. If this feature is
- activated you will be able to provide a customized DSDT by adding it
- to your initramfs. If your mkinitrd tool does not support this feature
- a script is provided in the documentation. For more details see
- <file:Documentation/dsdt-initrd.txt> or
- If there is no table found, it will fall-back to the custom DSDT
- in-kernel (if activated) or to the DSDT from the BIOS.
- Even if you do not need a new one at the moment, you may want to use a
- better DSDT later. It is safe to say Y here.
+ This option supports a custom DSDT by optionally loading it from
+ See Documentation/acpi/dsdt-override.txt
+ If you are not using this feature now, but may use it later,
+ it is safe to say Y here.
int "Disable ACPI for systems before Jan 1st this year" if X86_32
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