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authorLinus Torvalds <torvalds@linux-foundation.org>2019-05-07 05:35:13 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2019-05-07 05:35:13 +0300
commit59df1c2bdecb0d1aaadfb8533df4bea528ee4952 (patch)
treeded1e05c84622331dd6a61b24db31e9b920f6970 /Documentation/acpi/method-customizing.txt
parentc620f7bd0ba5c882b3e7fc199a8d5c2f6c2f5263 (diff)
parent10b4768b27a0b8f9459570723ecb1809f4d707e0 (diff)
downloadlinux-59df1c2bdecb0d1aaadfb8533df4bea528ee4952.tar.xz
Merge tag 'acpi-5.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm
Pull ACPI updates from Rafael Wysocki: "These rearrange the ACPI documentation by converting it to the .rst format and splitting it into clear categories (admin guide, driver API, firmware guide), switch over multiple users of a problematic library function to a new better one, update the ACPICA code in the kernel to a new upstream release, fix a few issues, improve power device management diagnostics and do some cleanups. Specifics: - Convert the ACPI documentation in the kernel source tree to the .rst format and split it into the admin guide, driver API and firmware guide parts (Changbin Du). - Add a PRP0001 usage example to the ACPI documentation (Thomas Preston). - Switch over the users of the acpi_dev_get_first_match_name() library function which turned out to be problematic to a new, better one called acpi_dev_get_first_match_dev() (Andy Shevchenko, YueHaibing). - Update the ACPICA code in the kernel to upstream release 20190405 including: * Null pointer dereference check in acpi_ns_delete_node() (Erik Schmauss). * Multiple macro and function name changes (Bob Moore). * Predefined operation region name fix (Erik Schmauss). - Fix hibernation issue on systems using the Baytrail and Cherrytrail Intel SoCs introduced during the 4.20 development cycle (Hans de Goede). - Add Sony VPCEH3U1E to the backlight quirk list (Zhang Rui). - Fix button handling during system resume (Zhang Rui). - Add a device PM diagnostic message (Rafael Wysocki). - Clean up the code, comments and white space in multiple places (Bjorn Helgaas, Gustavo Silva, Kefeng Wang)" * tag 'acpi-5.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm: (53 commits) Documentation: ACPI: move video_extension.txt to firmware-guide/acpi and convert to reST Documentation: ACPI: move ssdt-overlays.txt to admin-guide/acpi and convert to reST Documentation: ACPI: move lpit.txt to firmware-guide/acpi and convert to reST Documentation: ACPI: move cppc_sysfs.txt to admin-guide/acpi and convert to reST Documentation: ACPI: move apei/einj.txt to firmware-guide/acpi and convert to reST Documentation: ACPI: move apei/output_format.txt to firmware-guide/acpi and convert to reST Documentation: ACPI: move aml-debugger.txt to firmware-guide/acpi and convert to reST Documentation: ACPI: move method-tracing.txt to firmware-guide/acpi and convert to rsST Documentation: ACPI: move debug.txt to firmware-guide/acpi and convert to reST Documentation: ACPI: move dsd/data-node-references.txt to firmware-guide/acpi and convert to reST Documentation: ACPI: move dsd/graph.txt to firmware-guide/acpi and convert to reST Documentation: ACPI: move acpi-lid.txt to firmware-guide/acpi and convert to reST Documentation: ACPI: move i2c-muxes.txt to firmware-guide/acpi and convert to reST Documentation: ACPI: move dsdt-override.txt to admin-guide/acpi and convert to reST Documentation: ACPI: move initrd_table_override.txt to admin-guide/acpi and convert to reST Documentation: ACPI: move method-customizing.txt to firmware-guide/acpi and convert to reST Documentation: ACPI: move gpio-properties.txt to firmware-guide/acpi and convert to reST Documentation: ACPI: move DSD-properties-rules.txt to firmware-guide/acpi and covert to reST Documentation: ACPI: move scan_handlers.txt to driver-api/acpi and convert to reST Documentation: ACPI: move linuxized-acpica.txt to driver-api/acpi and convert to reST ...
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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).