From 59bcdcccf31f5a42cd23ea46154f9b3546d66009 Mon Sep 17 00:00:00 2001 From: Changbin Du Date: Thu, 25 Apr 2019 01:52:52 +0800 Subject: Documentation: ACPI: move initrd_table_override.txt to admin-guide/acpi and convert to reST This converts the plain text documentation to reStructuredText format and adds it to Sphinx TOC tree. No essential content change. Signed-off-by: Changbin Du Reviewed-by: Mauro Carvalho Chehab Signed-off-by: Rafael J. Wysocki --- Documentation/acpi/initrd_table_override.txt | 111 --------------------------- 1 file changed, 111 deletions(-) delete mode 100644 Documentation/acpi/initrd_table_override.txt (limited to 'Documentation/acpi') diff --git a/Documentation/acpi/initrd_table_override.txt b/Documentation/acpi/initrd_table_override.txt deleted file mode 100644 index 30437a6db373..000000000000 --- a/Documentation/acpi/initrd_table_override.txt +++ /dev/null @@ -1,111 +0,0 @@ -Upgrading ACPI tables via initrd -================================ - -1) Introduction (What is this about) -2) What is this for -3) How does it work -4) References (Where to retrieve userspace tools) - -1) What is this about ---------------------- - -If the ACPI_TABLE_UPGRADE compile option is true, it is possible to -upgrade the ACPI execution environment that is defined by the ACPI tables -via upgrading the ACPI tables provided by the BIOS with an instrumented, -modified, more recent version one, or installing brand new ACPI tables. - -When building initrd with kernel in a single image, option -ACPI_TABLE_OVERRIDE_VIA_BUILTIN_INITRD should also be true for this -feature to work. - -For a full list of ACPI tables that can be upgraded/installed, take a look -at the char *table_sigs[MAX_ACPI_SIGNATURE]; definition in -drivers/acpi/tables.c. -All ACPI tables iasl (Intel's ACPI compiler and disassembler) knows should -be overridable, except: - - ACPI_SIG_RSDP (has a signature of 6 bytes) - - ACPI_SIG_FACS (does not have an ordinary ACPI table header) -Both could get implemented as well. - - -2) What is this for -------------------- - -Complain to your platform/BIOS vendor if you find a bug which is so severe -that a workaround is not accepted in the Linux kernel. And this facility -allows you to upgrade the buggy tables before your platform/BIOS vendor -releases an upgraded BIOS binary. - -This facility can be used by platform/BIOS vendors to provide a Linux -compatible environment without modifying the underlying platform firmware. - -This facility also provides a powerful feature to easily debug and test -ACPI BIOS table compatibility with the Linux kernel by modifying old -platform provided ACPI tables or inserting new ACPI tables. - -It can and should be enabled in any kernel because there is no functional -change with not instrumented initrds. - - -3) How does it work -------------------- - -# Extract the machine's ACPI tables: -cd /tmp -acpidump >acpidump -acpixtract -a acpidump -# Disassemble, modify and recompile them: -iasl -d *.dat -# For example add this statement into a _PRT (PCI Routing Table) function -# of the DSDT: -Store("HELLO WORLD", debug) -# And increase the OEM Revision. For example, before modification: -DefinitionBlock ("DSDT.aml", "DSDT", 2, "INTEL ", "TEMPLATE", 0x00000000) -# After modification: -DefinitionBlock ("DSDT.aml", "DSDT", 2, "INTEL ", "TEMPLATE", 0x00000001) -iasl -sa dsdt.dsl -# Add the raw ACPI tables to an uncompressed cpio archive. -# They must be put into a /kernel/firmware/acpi directory inside the cpio -# archive. Note that if the table put here matches a platform table -# (similar Table Signature, and similar OEMID, and similar OEM Table ID) -# with a more recent OEM Revision, the platform table will be upgraded by -# this table. If the table put here doesn't match a platform table -# (dissimilar Table Signature, or dissimilar OEMID, or dissimilar OEM Table -# ID), this table will be appended. -mkdir -p kernel/firmware/acpi -cp dsdt.aml kernel/firmware/acpi -# A maximum of "NR_ACPI_INITRD_TABLES (64)" tables are currently allowed -# (see osl.c): -iasl -sa facp.dsl -iasl -sa ssdt1.dsl -cp facp.aml kernel/firmware/acpi -cp ssdt1.aml kernel/firmware/acpi -# The uncompressed cpio archive must be the first. Other, typically -# compressed cpio archives, must be concatenated on top of the uncompressed -# one. Following command creates the uncompressed cpio archive and -# concatenates the original initrd on top: -find kernel | cpio -H newc --create > /boot/instrumented_initrd -cat /boot/initrd >>/boot/instrumented_initrd -# reboot with increased acpi debug level, e.g. boot params: -acpi.debug_level=0x2 acpi.debug_layer=0xFFFFFFFF -# and check your syslog: -[ 1.268089] ACPI: PCI Interrupt Routing Table [\_SB_.PCI0._PRT] -[ 1.272091] [ACPI Debug] String [0x0B] "HELLO WORLD" - -iasl is able to disassemble and recompile quite a lot different, -also static ACPI tables. - - -4) Where to retrieve userspace tools ------------------------------------- - -iasl and acpixtract are part of Intel's ACPICA project: -http://acpica.org/ -and should be packaged by distributions (for example in the acpica package -on SUSE). - -acpidump can be found in Len Browns pmtools: -ftp://kernel.org/pub/linux/kernel/people/lenb/acpi/utils/pmtools/acpidump -This tool is also part of the acpica package on SUSE. -Alternatively, used ACPI tables can be retrieved via sysfs in latest kernels: -/sys/firmware/acpi/tables -- cgit v1.2.3