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authorChangbin Du <changbin.du@gmail.com>2019-04-24 20:52:51 +0300
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2019-04-26 00:07:20 +0300
commiteea7803278619d1a3bda6306cd8470497cd2c5e3 (patch)
tree8ad22a9de9e892ec6b85a9a3c53d342abe26825b /Documentation/acpi
parentb6dff0e153e919b62e2a1c90fd6e5a4ba922f99b (diff)
downloadlinux-eea7803278619d1a3bda6306cd8470497cd2c5e3.tar.xz
Documentation: ACPI: move method-customizing.txt to firmware-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 <changbin.du@gmail.com> Reviewed-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'Documentation/acpi')
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diff --git a/Documentation/acpi/method-customizing.txt b/Documentation/acpi/method-customizing.txt
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-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. Methods
- declared inside scope operators are also not supported.
-Note: The same ACPI control method can be overridden for many times,
- and it's always the latest one that used by Linux/kernel.
-Note: To get the ACPI debug object output (Store (AAAA, Debug)),
- please run "echo 1 > /sys/module/acpi/parameters/aml_debug_output".
-
-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)
- {
- 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.
- e) assemble the file to generate the AML code of the method.
- e.g. "iasl -vw 6084 psr.asl" (psr.aml is generated as a result)
- If parameter "-vw 6084" is not supported by your iASL compiler,
- please try a newer version.
- 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 overridden 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.
-
-Note: Be aware that root can mis-use this driver to modify arbitrary
- memory and gain additional rights, if root's privileges got
- restricted (for example if root is not allowed to load additional
- modules after boot).