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Date:   Wed, 24 Apr 2019 11:51:03 -0300
From:   Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
To:     Changbin Du <changbin.du@gmail.com>
Cc:     Jonathan Corbet <corbet@lwn.net>,
        Bjorn Helgaas <bhelgaas@google.com>, rjw@rjwysocki.net,
        linux-pci@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com,
        x86@kernel.org, fenghua.yu@intel.com,
        linuxppc-dev@lists.ozlabs.org, linux-acpi@vger.kernel.org,
        linux-gpio@vger.kernel.org
Subject: Re: [PATCH v4 23/63] Documentation: ACPI: move ssdt-overlays.txt to
 admin-guide/acpi and convert to reST
Message-ID: <20190424115103.554268cf@coco.lan>
In-Reply-To: <20190423162932.21428-24-changbin.du@gmail.com>
References: <20190423162932.21428-1-changbin.du@gmail.com>
        <20190423162932.21428-24-changbin.du@gmail.com>
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Em Wed, 24 Apr 2019 00:28:52 +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>

Reviewed-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

> ---
>  Documentation/acpi/ssdt-overlays.txt          | 172 -----------------
>  Documentation/admin-guide/acpi/index.rst      |   1 +
>  .../admin-guide/acpi/ssdt-overlays.rst        | 180 ++++++++++++++++++
>  3 files changed, 181 insertions(+), 172 deletions(-)
>  delete mode 100644 Documentation/acpi/ssdt-overlays.txt
>  create mode 100644 Documentation/admin-guide/acpi/ssdt-overlays.rst
> 
> diff --git a/Documentation/acpi/ssdt-overlays.txt b/Documentation/acpi/ssdt-overlays.txt
> deleted file mode 100644
> index 5ae13f161ea2..000000000000
> --- a/Documentation/acpi/ssdt-overlays.txt
> +++ /dev/null
> @@ -1,172 +0,0 @@
> -
> -In order to support ACPI open-ended hardware configurations (e.g. development
> -boards) we need a way to augment the ACPI configuration provided by the firmware
> -image. A common example is connecting sensors on I2C / SPI buses on development
> -boards.
> -
> -Although this can be accomplished by creating a kernel platform driver or
> -recompiling the firmware image with updated ACPI tables, neither is practical:
> -the former proliferates board specific kernel code while the latter requires
> -access to firmware tools which are often not publicly available.
> -
> -Because ACPI supports external references in AML code a more practical
> -way to augment firmware ACPI configuration is by dynamically loading
> -user defined SSDT tables that contain the board specific information.
> -
> -For example, to enumerate a Bosch BMA222E accelerometer on the I2C bus of the
> -Minnowboard MAX development board exposed via the LSE connector [1], the
> -following ASL code can be used:
> -
> -DefinitionBlock ("minnowmax.aml", "SSDT", 1, "Vendor", "Accel", 0x00000003)
> -{
> -    External (\_SB.I2C6, DeviceObj)
> -
> -    Scope (\_SB.I2C6)
> -    {
> -        Device (STAC)
> -        {
> -            Name (_ADR, Zero)
> -            Name (_HID, "BMA222E")
> -
> -            Method (_CRS, 0, Serialized)
> -            {
> -                Name (RBUF, ResourceTemplate ()
> -                {
> -                    I2cSerialBus (0x0018, ControllerInitiated, 0x00061A80,
> -                                  AddressingMode7Bit, "\\_SB.I2C6", 0x00,
> -                                  ResourceConsumer, ,)
> -                    GpioInt (Edge, ActiveHigh, Exclusive, PullDown, 0x0000,
> -                             "\\_SB.GPO2", 0x00, ResourceConsumer, , )
> -                    { // Pin list
> -                        0
> -                    }
> -                })
> -                Return (RBUF)
> -            }
> -        }
> -    }
> -}
> -
> -which can then be compiled to AML binary format:
> -
> -$ iasl minnowmax.asl
> -
> -Intel ACPI Component Architecture
> -ASL Optimizing Compiler version 20140214-64 [Mar 29 2014]
> -Copyright (c) 2000 - 2014 Intel Corporation
> -
> -ASL Input:     minnomax.asl - 30 lines, 614 bytes, 7 keywords
> -AML Output:    minnowmax.aml - 165 bytes, 6 named objects, 1 executable opcodes
> -
> -[1] http://wiki.minnowboard.org/MinnowBoard_MAX#Low_Speed_Expansion_Connector_.28Top.29
> -
> -The resulting AML code can then be loaded by the kernel using one of the methods
> -below.
> -
> -== Loading ACPI SSDTs from initrd ==
> -
> -This option allows loading of user defined SSDTs from initrd and it is useful
> -when the system does not support EFI or when there is not enough EFI storage.
> -
> -It works in a similar way with initrd based ACPI tables override/upgrade: SSDT
> -aml code must be placed in the first, uncompressed, initrd under the
> -"kernel/firmware/acpi" path. Multiple files can be used and this will translate
> -in loading multiple tables. Only SSDT and OEM tables are allowed. See
> -initrd_table_override.txt for more details.
> -
> -Here is an example:
> -
> -# Add the raw ACPI tables to an uncompressed cpio archive.
> -# They must be put into a /kernel/firmware/acpi directory inside the
> -# cpio archive.
> -# The uncompressed cpio archive must be the first.
> -# Other, typically compressed cpio archives, must be
> -# concatenated on top of the uncompressed one.
> -mkdir -p kernel/firmware/acpi
> -cp ssdt.aml kernel/firmware/acpi
> -
> -# Create the uncompressed cpio archive and concatenate the original initrd
> -# on top:
> -find kernel | cpio -H newc --create > /boot/instrumented_initrd
> -cat /boot/initrd >>/boot/instrumented_initrd
> -
> -== Loading ACPI SSDTs from EFI variables ==
> -
> -This is the preferred method, when EFI is supported on the platform, because it
> -allows a persistent, OS independent way of storing the user defined SSDTs. There
> -is also work underway to implement EFI support for loading user defined SSDTs
> -and using this method will make it easier to convert to the EFI loading
> -mechanism when that will arrive.
> -
> -In order to load SSDTs from an EFI variable the efivar_ssdt kernel command line
> -parameter can be used. The argument for the option is the variable name to
> -use. If there are multiple variables with the same name but with different
> -vendor GUIDs, all of them will be loaded.
> -
> -In order to store the AML code in an EFI variable the efivarfs filesystem can be
> -used. It is enabled and mounted by default in /sys/firmware/efi/efivars in all
> -recent distribution.
> -
> -Creating a new file in /sys/firmware/efi/efivars will automatically create a new
> -EFI variable. Updating a file in /sys/firmware/efi/efivars will update the EFI
> -variable. Please note that the file name needs to be specially formatted as
> -"Name-GUID" and that the first 4 bytes in the file (little-endian format)
> -represent the attributes of the EFI variable (see EFI_VARIABLE_MASK in
> -include/linux/efi.h). Writing to the file must also be done with one write
> -operation.
> -
> -For example, you can use the following bash script to create/update an EFI
> -variable with the content from a given file:
> -
> -#!/bin/sh -e
> -
> -while ! [ -z "$1" ]; do
> -        case "$1" in
> -        "-f") filename="$2"; shift;;
> -        "-g") guid="$2"; shift;;
> -        *) name="$1";;
> -        esac
> -        shift
> -done
> -
> -usage()
> -{
> -        echo "Syntax: ${0##*/} -f filename [ -g guid ] name"
> -        exit 1
> -}
> -
> -[ -n "$name" -a -f "$filename" ] || usage
> -
> -EFIVARFS="/sys/firmware/efi/efivars"
> -
> -[ -d "$EFIVARFS" ] || exit 2
> -
> -if stat -tf $EFIVARFS | grep -q -v de5e81e4; then
> -        mount -t efivarfs none $EFIVARFS
> -fi
> -
> -# try to pick up an existing GUID
> -[ -n "$guid" ] || guid=$(find "$EFIVARFS" -name "$name-*" | head -n1 | cut -f2- -d-)
> -
> -# use a randomly generated GUID
> -[ -n "$guid" ] || guid="$(cat /proc/sys/kernel/random/uuid)"
> -
> -# efivarfs expects all of the data in one write
> -tmp=$(mktemp)
> -/bin/echo -ne "\007\000\000\000" | cat - $filename > $tmp
> -dd if=$tmp of="$EFIVARFS/$name-$guid" bs=$(stat -c %s $tmp)
> -rm $tmp
> -
> -== Loading ACPI SSDTs from configfs ==
> -
> -This option allows loading of user defined SSDTs from userspace via the configfs
> -interface. The CONFIG_ACPI_CONFIGFS option must be select and configfs must be
> -mounted. In the following examples, we assume that configfs has been mounted in
> -/config.
> -
> -New tables can be loading by creating new directories in /config/acpi/table/ and
> -writing the SSDT aml code in the aml attribute:
> -
> -cd /config/acpi/table
> -mkdir my_ssdt
> -cat ~/ssdt.aml > my_ssdt/aml
> diff --git a/Documentation/admin-guide/acpi/index.rst b/Documentation/admin-guide/acpi/index.rst
> index 9049a7b9f065..4d13eeea1eca 100644
> --- a/Documentation/admin-guide/acpi/index.rst
> +++ b/Documentation/admin-guide/acpi/index.rst
> @@ -10,4 +10,5 @@ the Linux ACPI support.
>  
>     initrd_table_override
>     dsdt-override
> +   ssdt-overlays
>     cppc_sysfs
> diff --git a/Documentation/admin-guide/acpi/ssdt-overlays.rst b/Documentation/admin-guide/acpi/ssdt-overlays.rst
> new file mode 100644
> index 000000000000..da37455f96c9
> --- /dev/null
> +++ b/Documentation/admin-guide/acpi/ssdt-overlays.rst
> @@ -0,0 +1,180 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +=============
> +SSDT Overlays
> +=============
> +
> +In order to support ACPI open-ended hardware configurations (e.g. development
> +boards) we need a way to augment the ACPI configuration provided by the firmware
> +image. A common example is connecting sensors on I2C / SPI buses on development
> +boards.
> +
> +Although this can be accomplished by creating a kernel platform driver or
> +recompiling the firmware image with updated ACPI tables, neither is practical:
> +the former proliferates board specific kernel code while the latter requires
> +access to firmware tools which are often not publicly available.
> +
> +Because ACPI supports external references in AML code a more practical
> +way to augment firmware ACPI configuration is by dynamically loading
> +user defined SSDT tables that contain the board specific information.
> +
> +For example, to enumerate a Bosch BMA222E accelerometer on the I2C bus of the
> +Minnowboard MAX development board exposed via the LSE connector [1], the
> +following ASL code can be used::
> +
> +    DefinitionBlock ("minnowmax.aml", "SSDT", 1, "Vendor", "Accel", 0x00000003)
> +    {
> +        External (\_SB.I2C6, DeviceObj)
> +
> +        Scope (\_SB.I2C6)
> +        {
> +            Device (STAC)
> +            {
> +                Name (_ADR, Zero)
> +                Name (_HID, "BMA222E")
> +
> +                Method (_CRS, 0, Serialized)
> +                {
> +                    Name (RBUF, ResourceTemplate ()
> +                    {
> +                        I2cSerialBus (0x0018, ControllerInitiated, 0x00061A80,
> +                                    AddressingMode7Bit, "\\_SB.I2C6", 0x00,
> +                                    ResourceConsumer, ,)
> +                        GpioInt (Edge, ActiveHigh, Exclusive, PullDown, 0x0000,
> +                                "\\_SB.GPO2", 0x00, ResourceConsumer, , )
> +                        { // Pin list
> +                            0
> +                        }
> +                    })
> +                    Return (RBUF)
> +                }
> +            }
> +        }
> +    }
> +
> +which can then be compiled to AML binary format::
> +
> +    $ iasl minnowmax.asl
> +
> +    Intel ACPI Component Architecture
> +    ASL Optimizing Compiler version 20140214-64 [Mar 29 2014]
> +    Copyright (c) 2000 - 2014 Intel Corporation
> +
> +    ASL Input:     minnomax.asl - 30 lines, 614 bytes, 7 keywords
> +    AML Output:    minnowmax.aml - 165 bytes, 6 named objects, 1 executable opcodes
> +
> +[1] http://wiki.minnowboard.org/MinnowBoard_MAX#Low_Speed_Expansion_Connector_.28Top.29
> +
> +The resulting AML code can then be loaded by the kernel using one of the methods
> +below.
> +
> +Loading ACPI SSDTs from initrd
> +==============================
> +
> +This option allows loading of user defined SSDTs from initrd and it is useful
> +when the system does not support EFI or when there is not enough EFI storage.
> +
> +It works in a similar way with initrd based ACPI tables override/upgrade: SSDT
> +aml code must be placed in the first, uncompressed, initrd under the
> +"kernel/firmware/acpi" path. Multiple files can be used and this will translate
> +in loading multiple tables. Only SSDT and OEM tables are allowed. See
> +initrd_table_override.txt for more details.
> +
> +Here is an example::
> +
> +    # Add the raw ACPI tables to an uncompressed cpio archive.
> +    # They must be put into a /kernel/firmware/acpi directory inside the
> +    # cpio archive.
> +    # The uncompressed cpio archive must be the first.
> +    # Other, typically compressed cpio archives, must be
> +    # concatenated on top of the uncompressed one.
> +    mkdir -p kernel/firmware/acpi
> +    cp ssdt.aml kernel/firmware/acpi
> +
> +    # Create the uncompressed cpio archive and concatenate the original initrd
> +    # on top:
> +    find kernel | cpio -H newc --create > /boot/instrumented_initrd
> +    cat /boot/initrd >>/boot/instrumented_initrd
> +
> +Loading ACPI SSDTs from EFI variables
> +=====================================
> +
> +This is the preferred method, when EFI is supported on the platform, because it
> +allows a persistent, OS independent way of storing the user defined SSDTs. There
> +is also work underway to implement EFI support for loading user defined SSDTs
> +and using this method will make it easier to convert to the EFI loading
> +mechanism when that will arrive.
> +
> +In order to load SSDTs from an EFI variable the efivar_ssdt kernel command line
> +parameter can be used. The argument for the option is the variable name to
> +use. If there are multiple variables with the same name but with different
> +vendor GUIDs, all of them will be loaded.
> +
> +In order to store the AML code in an EFI variable the efivarfs filesystem can be
> +used. It is enabled and mounted by default in /sys/firmware/efi/efivars in all
> +recent distribution.
> +
> +Creating a new file in /sys/firmware/efi/efivars will automatically create a new
> +EFI variable. Updating a file in /sys/firmware/efi/efivars will update the EFI
> +variable. Please note that the file name needs to be specially formatted as
> +"Name-GUID" and that the first 4 bytes in the file (little-endian format)
> +represent the attributes of the EFI variable (see EFI_VARIABLE_MASK in
> +include/linux/efi.h). Writing to the file must also be done with one write
> +operation.
> +
> +For example, you can use the following bash script to create/update an EFI
> +variable with the content from a given file::
> +
> +    #!/bin/sh -e
> +
> +    while ! [ -z "$1" ]; do
> +            case "$1" in
> +            "-f") filename="$2"; shift;;
> +            "-g") guid="$2"; shift;;
> +            *) name="$1";;
> +            esac
> +            shift
> +    done
> +
> +    usage()
> +    {
> +            echo "Syntax: ${0##*/} -f filename [ -g guid ] name"
> +            exit 1
> +    }
> +
> +    [ -n "$name" -a -f "$filename" ] || usage
> +
> +    EFIVARFS="/sys/firmware/efi/efivars"
> +
> +    [ -d "$EFIVARFS" ] || exit 2
> +
> +    if stat -tf $EFIVARFS | grep -q -v de5e81e4; then
> +            mount -t efivarfs none $EFIVARFS
> +    fi
> +
> +    # try to pick up an existing GUID
> +    [ -n "$guid" ] || guid=$(find "$EFIVARFS" -name "$name-*" | head -n1 | cut -f2- -d-)
> +
> +    # use a randomly generated GUID
> +    [ -n "$guid" ] || guid="$(cat /proc/sys/kernel/random/uuid)"
> +
> +    # efivarfs expects all of the data in one write
> +    tmp=$(mktemp)
> +    /bin/echo -ne "\007\000\000\000" | cat - $filename > $tmp
> +    dd if=$tmp of="$EFIVARFS/$name-$guid" bs=$(stat -c %s $tmp)
> +    rm $tmp
> +
> +Loading ACPI SSDTs from configfs
> +================================
> +
> +This option allows loading of user defined SSDTs from userspace via the configfs
> +interface. The CONFIG_ACPI_CONFIGFS option must be select and configfs must be
> +mounted. In the following examples, we assume that configfs has been mounted in
> +/config.
> +
> +New tables can be loading by creating new directories in /config/acpi/table/ and
> +writing the SSDT aml code in the aml attribute::
> +
> +    cd /config/acpi/table
> +    mkdir my_ssdt
> +    cat ~/ssdt.aml > my_ssdt/aml


Thanks,
Mauro