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author | James Morris <jmorris@namei.org> | 2010-01-18 09:56:22 +1100 |
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committer | James Morris <jmorris@namei.org> | 2010-01-18 09:56:22 +1100 |
commit | 2457552d1e6f3183cd93f81c49a8da5fe8bb0e42 (patch) | |
tree | 7ca46caa910012d75617700e4083b3657053cb31 /Documentation/acpi/method-customizing.txt | |
parent | selinux: change the handling of unknown classes (diff) | |
parent | page allocator: update NR_FREE_PAGES only when necessary (diff) | |
download | linux-dev-2457552d1e6f3183cd93f81c49a8da5fe8bb0e42.tar.xz linux-dev-2457552d1e6f3183cd93f81c49a8da5fe8bb0e42.zip |
Merge branch 'master' into next
Diffstat (limited to 'Documentation/acpi/method-customizing.txt')
-rw-r--r-- | Documentation/acpi/method-customizing.txt | 66 |
1 files changed, 66 insertions, 0 deletions
diff --git a/Documentation/acpi/method-customizing.txt b/Documentation/acpi/method-customizing.txt new file mode 100644 index 000000000000..e628cd23ca80 --- /dev/null +++ b/Documentation/acpi/method-customizing.txt @@ -0,0 +1,66 @@ +Linux ACPI Custom Control Method How To +======================================= + +Written by Zhang Rui <rui.zhang@intel.com> + + +Linux supports customizing ACPI control methods at runtime. + +Users can use this to +1. override an existing method which may not work correctly, + or just for debugging purposes. +2. insert a completely new method in order to create a missing + method such as _OFF, _ON, _STA, _INI, etc. +For these cases, it is far simpler to dynamically install a single +control method rather than override the entire DSDT, because kernel +rebuild/reboot is not needed and test result can be got in minutes. + +Note: Only ACPI METHOD can be overridden, any other object types like + "Device", "OperationRegion", are not recognized. +Note: The same ACPI control method can be overridden for many times, + and it's always the latest one that used by Linux/kernel. + +1. override an existing method + a) get the ACPI table via ACPI sysfs I/F. e.g. to get the DSDT, + just run "cat /sys/firmware/acpi/tables/DSDT > /tmp/dsdt.dat" + b) disassemble the table by running "iasl -d dsdt.dat". + c) rewrite the ASL code of the method and save it in a new file, + d) package the new file (psr.asl) to an ACPI table format. + Here is an example of a customized \_SB._AC._PSR method, + + DefinitionBlock ("", "SSDT", 1, "", "", 0x20080715) + { + External (ACON) + + Method (\_SB_.AC._PSR, 0, NotSerialized) + { + Store ("In AC _PSR", Debug) + Return (ACON) + } + } + Note that the full pathname of the method in ACPI namespace + should be used. + And remember to use "External" to declare external objects. + e) assemble the file to generate the AML code of the method. + e.g. "iasl psr.asl" (psr.aml is generated as a result) + f) mount debugfs by "mount -t debugfs none /sys/kernel/debug" + g) override the old method via the debugfs by running + "cat /tmp/psr.aml > /sys/kernel/debug/acpi/custom_method" + +2. insert a new method + This is easier than overriding an existing method. + We just need to create the ASL code of the method we want to + insert and then follow the step c) ~ g) in section 1. + +3. undo your changes + The "undo" operation is not supported for a new inserted method + right now, i.e. we can not remove a method currently. + For an overrided method, in order to undo your changes, please + save a copy of the method original ASL code in step c) section 1, + and redo step c) ~ g) to override the method with the original one. + + +Note: We can use a kernel with multiple custom ACPI method running, + But each individual write to debugfs can implement a SINGLE + method override. i.e. if we want to insert/override multiple + ACPI methods, we need to redo step c) ~ g) for multiple times. |