Re: [PATCH v4 09/63] Documentation: ACPI: move method-customizing.txt to firmware-guide/acpi and convert to reST

Mauro Carvalho Chehab
2019-04-23T21:03:34Z

Em Wed, 24 Apr 2019 00:28:38 +0800
Changbin Du <changbin.du@gmail.com> escreveu:

> This converts the plain text documentation to reStructuredText format and
> add it to Sphinx TOC tree. No essential content change.
>
> Signed-off-by: Changbin Du <changbin.du@gmail.com>
> ---
> Documentation/acpi/method-customizing.txt | 73 -----------------
> Documentation/firmware-guide/acpi/index.rst | 3 +-
> .../acpi/method-customizing.rst | 82 +++++++++++++++++++
> 3 files changed, 84 insertions(+), 74 deletions(-)
> delete mode 100644 Documentation/acpi/method-customizing.txt
> create mode 100644 Documentation/firmware-guide/acpi/method-customizing.rst
>
> diff --git a/Documentation/acpi/method-customizing.txt b/Documentation/acpi/method-customizing.txt
> deleted file mode 100644
> index 7235da975f23..000000000000
> --- a/Documentation/acpi/method-customizing.txt
> +++ /dev/null
> @@ -1,73 +0,0 @@
> -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).
> diff --git a/Documentation/firmware-guide/acpi/index.rst b/Documentation/firmware-guide/acpi/index.rst
> index 61d67763851b..d1d069b26bbc 100644
> --- a/Documentation/firmware-guide/acpi/index.rst
> +++ b/Documentation/firmware-guide/acpi/index.rst
> @@ -10,5 +10,6 @@ ACPI Support
> namespace
> enumeration
> osi
> + method-customizing
> DSD-properties-rules
> - gpio-properties
> + gpio-properties
> \ No newline at end of file
> diff --git a/Documentation/firmware-guide/acpi/method-customizing.rst b/Documentation/firmware-guide/acpi/method-customizing.rst
> new file mode 100644
> index 000000000000..32eb1cdc1549
> --- /dev/null
> +++ b/Documentation/firmware-guide/acpi/method-customizing.rst
> @@ -0,0 +1,82 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +=======================================
> +Linux ACPI Custom Control Method How To
> +=======================================
> +
> +:Author: 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".

Hmm... this may work (not sure if Sphinx would warn or not), but it
is visually bad on text mode. I would code it, instead, with something
like:

.. 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.

- The same ACPI control method can be overridden for many times,
and it's always the latest one that used by Linux/kernel.

- To get the ACPI debug object output (Store (AAAA, Debug)),
please run::

echo 1 > /sys/module/acpi/parameters/aml_debug_output

As this would make it visually better on both text and html formats.

> +
> +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.

I would use ``iasl -vw 6084 psr.asl`` and ``-vw 6084``.

> +f) mount debugfs by "mount -t debugfs none /sys/kernel/debug"

I would do:

f) mount debugfs by running::

mount -t debugfs none /sys/kernel/debug

As it makes a better html document. I believe that the focus here is
sysadmins. Doing the above makes easier for them to cut and paste
commands.

> +g) override the old method via the debugfs by running
> + "cat /tmp/psr.aml > /sys/kernel/debug/acpi/custom_method"

Same applies here: I would also place the "cat" command on a literal
block.

> +
> +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).

Same comment as above: IMHO, having a single note block with the two
notes would be better.

Thanks,
Mauro