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Message-ID: <ded85a65-2631-cf7d-88f7-532a26eec5ed@collabora.com>
Date:   Fri, 22 Apr 2022 19:47:05 +0500
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Cc:     usama.anjum@collabora.com,
        Collabora Kernel ML <kernel@collabora.com>,
        groeck@chromium.org, dtor@chromium.org,
        Len Brown <lenb@kernel.org>, gwendal@chromium.org,
        vbendeb@chromium.org, andy@infradead.org,
        Ayman Bagabas <ayman.bagabas@gmail.com>,
        Benjamin Tissoires <benjamin.tissoires@redhat.com>,
        =?UTF-8?Q?Bla=c5=be_Hrastnik?= <blaz@mxxn.io>,
        Darren Hart <dvhart@infradead.org>,
        Dmitry Torokhov <dmitry.torokhov@gmail.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jeremy Soller <jeremy@system76.com>,
        Mattias Jacobsson <2pi@mok.nu>,
        Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
        Rajat Jain <rajatja@google.com>,
        Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
        platform-driver-x86@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-acpi@vger.kernel.org,
        "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
        Enric Balletbo i Serra <eballetbo@gmail.com>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Mark Gross <markgross@kernel.org>
Subject: Re: [PATCH v8] platform: x86: Add ChromeOS ACPI device driver
Content-Language: en-US
To:     Hans de Goede <hdegoede@redhat.com>,
        Benson Leung <bleung@chromium.org>
References: <Ylmmf03fewXEjRr0@debian-BULLSEYE-live-builder-AMD64>
 <e4c150a8-6e68-d06b-c695-a428ccba14c8@collabora.com>
From:   Muhammad Usama Anjum <usama.anjum@collabora.com>
In-Reply-To: <e4c150a8-6e68-d06b-c695-a428ccba14c8@collabora.com>
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Hi Hans,

Can I add you as a maintainer of drivers/platform/x86/chromeos_acpi.c?
You already maintain some other drivers in this directory.

Thanks you,
Usama

On 4/18/22 10:57 PM, Muhammad Usama Anjum wrote:
> Hi Benson,
> 
> We are very near to getting this patch in. I can see that you are
> maintaining Chrome Platform support. This driver is in
> drivers/platform/x86/chromeos_acpi.c. Can you maintain this driver as
> well? I'll add you to the maintainers.
> 
> Thank you,
> Usama
> 
> On 4/15/22 10:08 PM, Muhammad Usama Anjum wrote:
>> From: Enric Balletbo i Serra <enric.balletbo@collabora.com>
>>
>> The x86 Chromebooks have ChromeOS ACPI device. This driver attaches to
>> the ChromeOS ACPI device and exports the values reported by ACPI in a
>> sysfs directory. This data isn't present in ACPI tables when read
>> through ACPI tools, hence a driver is needed to do it. The driver gets
>> data from firmware using ACPI component of the kernel. The ACPI values
>> are presented in string form (numbers as decimal values) or binary
>> blobs, and can be accessed as the contents of the appropriate read only
>> files in the standard ACPI device's sysfs directory tree. This data is
>> consumed by the ChromeOS user space.
>>
>> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>> Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
>> Cc: Hans de Goede <hdegoede@redhat.com>
>> Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
>> Signed-off-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
>> ---
>> Changes in v8:
>> - Change struct platform_driver name from chromeos_acpi_driver to
>>   chromeos_acpi_device_driver
>>
>> Changes in v7:
>> - Rename acpi_chromeos Kconfig option to chromeos_acpi
>> - Change this acpi driver to platform driver
>> - Minor cosmetic changes
>>
>> There were the following concerns on v4 which have been delt with in
>> v5/v6:
>> - Remove BINF.{0,1,4} from sysfs as they are reserved and not used
>>   anymore
>> - Reword the description of MECK
>> - Change function name from chromeos_acpi_alloc_name() to
>>   chromeos_acpi_gen_file_name()
>> - Remove local variable obj in chromeos_acpi_add_method()
>> - Replace usage of dev_info() to dev_dbg()
>> - Improve the description of the patch
>> - Add the firmware interface document which serves as primary
>>   documentation and garantees that this interface will not change
>> - GGL0001 is valid PNP ID of the Google. PNP ID can be used with the
>>   ACPI devices. Consensus was developed on it in discussion of v4.
>>
>> Changes in v6:
>> - Correct authorship and path email's From
>> - Add changelog between v4 and v5 in detail
>> - Add copywrite year 2022
>> - Improve the description and add concerns from V4 which have been fixed
>>
>> Changes in v5:
>> - Improve the description of the patch
>> - Document firmware interface
>> - Update sysfs interface documentation
>> - Remove binf{0,1,4} as they have been deprecated
>> - Update some cleanup logic in case of error
>>   - Remove freeing of chromeos_acpi.root explicitely in
>>     chromeos_acpi_device_remove() as it'll be automatically freed by
>>     chromeos_acpi_remove_groups()
>>   - If sysfs_create_groups() fails in chromeos_acpi_process_mlst(),
>>     cleanup all groups
>> - Cosmetic changes
>>
>> Changes in v4:
>> https://lore.kernel.org/lkml/20200413134611.478441-1-enric.balletbo@collabora.com/t/
>> - Add COMPILE_TEST to increase build coverage.
>> - Add sysfs ABI documentation.
>> - Rebased on top of 5.7-rc1 and solve conflicts.
>> - Cc ACPI maintainers.
>>
>> Changes in v3:
>> - Use attribute groups instead of adding files "by hand".
>> - Do not use "raw" kobject to create directories.
>> - Do not abuse of the platform_device interface. Remove it.
>>
>> Changes in v2:
>> - Note that this version is a total rework, with those major changes:
>> - Use lists to track dinamically allocated attributes and groups.
>> - Use sysfs binary attributes to store the ACPI contents.
>> - Remove all the functionalities except the one that creates the sysfs files.
>> ---
>>  .../ABI/testing/sysfs-driver-chromeos-acpi    | 126 +++++
>>  .../acpi/chromeos-acpi-device.rst             | 363 +++++++++++++
>>  Documentation/firmware-guide/acpi/index.rst   |   1 +
>>  drivers/platform/x86/Kconfig                  |  11 +
>>  drivers/platform/x86/Makefile                 |   3 +
>>  drivers/platform/x86/chromeos_acpi.c          | 513 ++++++++++++++++++
>>  6 files changed, 1017 insertions(+)
>>  create mode 100644 Documentation/ABI/testing/sysfs-driver-chromeos-acpi
>>  create mode 100644 Documentation/firmware-guide/acpi/chromeos-acpi-device.rst
>>  create mode 100644 drivers/platform/x86/chromeos_acpi.c
>>
>> diff --git a/Documentation/ABI/testing/sysfs-driver-chromeos-acpi b/Documentation/ABI/testing/sysfs-driver-chromeos-acpi
>> new file mode 100644
>> index 0000000000000..b74fbca62f4c3
>> --- /dev/null
>> +++ b/Documentation/ABI/testing/sysfs-driver-chromeos-acpi
>> @@ -0,0 +1,126 @@
>> +What:		/sys/bus/platform/devices/GGL0001:00/BINF.2
>> +Date:		April 2022
>> +KernelVersion:	5.19
>> +Description:
>> +		This file shows information about the current boot of
>> +		the active EC firmware.
>> +		  * 0 - Read only (recovery) firmware.
>> +		  * 1 - Rewritable firmware.
>> +
>> +What:		/sys/bus/platform/devices/GGL0001:00/BINF.3
>> +Date:		April 2022
>> +KernelVersion:	5.19
>> +Description:
>> +		This file shows information about the current boot of
>> +		the active main	firmware type.
>> +		  * 0 - Recovery.
>> +		  * 1 - Normal.
>> +		  * 2 - Developer.
>> +		  * 3 - Netboot (factory installation only).
>> +
>> +What:		/sys/bus/platform/devices/GGL0001:00/CHSW
>> +Date:		April 2022
>> +KernelVersion:	5.19
>> +Description:
>> +		This file shows the switch position for the Chrome OS specific
>> +		hardware switches.
>> +		  * 0   - No changes.
>> +		  * 2   - Recovery button was pressed when firmware booted.
>> +		  * 4   - Recovery button was pressed when EC firmware booted.
>> +		  * 32  - Developer switch was enabled when firmware booted.
>> +		  * 512 - Firmware write protect was disabled when firmware
>> +			  booted.
>> +
>> +What:		/sys/bus/platform/devices/GGL0001:00/FMAP
>> +Date:		April 2022
>> +KernelVersion:	5.19
>> +Description:
>> +		This file shows the physical memory address of the start of
>> +		the main processor firmware flashmap.
>> +
>> +What:		/sys/bus/platform/devices/GGL0001:00/FRID
>> +Date:		April 2022
>> +KernelVersion:	5.19
>> +Description:
>> +		This file shows the firmware version for the read-only portion
>> +		of the main processor firmware.
>> +
>> +What:		/sys/bus/platform/devices/GGL0001:00/FWID
>> +Date:		April 2022
>> +KernelVersion:	5.19
>> +Description:
>> +		This file shows the firmware version for the rewritable portion
>> +		of the main processor firmware.
>> +
>> +What:		/sys/bus/platform/devices/GGL0001:00/GPIO.X/GPIO.0
>> +Date:		April 2022
>> +KernelVersion:	5.19
>> +Description:
>> +		This file shows the type of the GPIO signal for the Chrome OS
>> +		specific GPIO assignments.
>> +		  * 1   - Recovery button.
>> +		  * 2   - Developer mode switch.
>> +		  * 3   - Firmware write protect switch.
>> +		  * 256 to 511 - Debug header GPIO 0 to GPIO 255.
>> +
>> +What:		/sys/bus/platform/devices/GGL0001:00/GPIO.X/GPIO.1
>> +Date:		April 2022
>> +KernelVersion:	5.19
>> +Description:
>> +		This file shows the signal attributes of the GPIO signal.
>> +		  * 0 - Signal is active low.
>> +		  * 1 - Signal is active high.
>> +
>> +What:		/sys/bus/platform/devices/GGL0001:00/GPIO.X/GPIO.2
>> +Date:		April 2022
>> +KernelVersion:	5.19
>> +Description:
>> +		This file shows the GPIO number on the specified GPIO
>> +		controller.
>> +
>> +What:		/sys/bus/platform/devices/GGL0001:00/GPIO.X/GPIO.3
>> +Date:		April 2022
>> +KernelVersion:	5.19
>> +Description:
>> +		This file shows the name of the GPIO controller.
>> +
>> +What:		/sys/bus/platform/devices/GGL0001:00/HWID
>> +Date:		April 2022
>> +KernelVersion:	5.19
>> +Description:
>> +		This file shows the hardware ID for the Chromebook.
>> +
>> +What:		/sys/bus/platform/devices/GGL0001:00/MECK
>> +Date:		April 2022
>> +KernelVersion:	5.19
>> +Description:
>> +		This binary file returns the SHA-1 or SHA-256 hash that is
>> +		read out of the Management Engine extend registers during
>> +		boot. The hash is exported vi ACPI so the OS can verify that
>> +		the Management Engine firmware has not changed. If Management
>> +		Engine is not present, or if the firmware was unable to read the
>> +		extend registers, this buffer size can be zero.
>> +
>> +What:		/sys/bus/platform/devices/GGL0001:00/VBNV.0
>> +Date:		April 2022
>> +KernelVersion:	5.19
>> +Description:
>> +		This file shows the offset in CMOS bank 0 of the verified boot
>> +		non-volatile storage block, counting from the first writable
>> +		CMOS byte (that is, 'offset = 0' is the byte following the 14
>> +		bytes of clock data).
>> +
>> +What:		/sys/bus/platform/devices/GGL0001:00/VBNV.1
>> +Date:		April 2022
>> +KernelVersion:	5.19
>> +Description:
>> +		This file shows the size in bytes of the verified boot
>> +		non-volatile storage block.
>> +
>> +What:		/sys/bus/platform/devices/GGL0001:00/VDAT
>> +Date:		April 2022
>> +KernelVersion:	5.19
>> +Description:
>> +		This binary file returns the verified boot data block shared
>> +		between the firmware verification step and the kernel
>> +		verification step.
>> diff --git a/Documentation/firmware-guide/acpi/chromeos-acpi-device.rst b/Documentation/firmware-guide/acpi/chromeos-acpi-device.rst
>> new file mode 100644
>> index 0000000000000..ef3cc980bad54
>> --- /dev/null
>> +++ b/Documentation/firmware-guide/acpi/chromeos-acpi-device.rst
>> @@ -0,0 +1,363 @@
>> +.. SPDX-License-Identifier: GPL-2.0
>> +
>> +=====================
>> +Chrome OS ACPI Device
>> +=====================
>> +
>> +Hardware functionality specific to Chrome OS is exposed through a Chrome OS ACPI device.
>> +The plug and play ID of a Chrome OS ACPI device is GGL0001. GGL is valid PNP ID of Google.
>> +PNP ID can be used with the ACPI devices accourding to the guidelines. The following ACPI
>> +objects are supported:
>> +
>> +.. flat-table:: Supported ACPI Objects
>> +   :widths: 1 2
>> +   :header-rows: 1
>> +
>> +   * - Object
>> +     - Description
>> +
>> +   * - CHSW
>> +     - Chrome OS switch positions
>> +
>> +   * - HWID
>> +     - Chrome OS hardware ID
>> +
>> +   * - FWID
>> +     - Chrome OS firmware version
>> +
>> +   * - FRID
>> +     - Chrome OS read-only firmware version
>> +
>> +   * - BINF
>> +     - Chrome OS boot information
>> +
>> +   * - GPIO
>> +     - Chrome OS GPIO assignments
>> +
>> +   * - VBNV
>> +     - Chrome OS NVRAM locations
>> +
>> +   * - VDTA
>> +     - Chrome OS verified boot data
>> +
>> +   * - FMAP
>> +     - Chrome OS flashmap base address
>> +
>> +   * - MLST
>> +     - Chrome OS method list
>> +
>> +CHSW (Chrome OS switch positions)
>> +=================================
>> +This control method returns the switch positions for Chrome OS specific hardware switches.
>> +
>> +Arguments:
>> +----------
>> +None
>> +
>> +Result code:
>> +------------
>> +An integer containing the switch positions as bitfields:
>> +
>> +.. flat-table::
>> +   :widths: 1 2
>> +
>> +   * - 0x00000002
>> +     - Recovery button was pressed when x86 firmware booted.
>> +
>> +   * - 0x00000004
>> +     - Recovery button was pressed when EC firmware booted. (required if EC EEPROM is
>> +       rewritable; otherwise optional)
>> +
>> +   * - 0x00000020
>> +     - Developer switch was enabled when x86 firmware booted.
>> +
>> +   * - 0x00000200
>> +     - Firmware write protect was disabled when x86 firmware booted. (required if
>> +       firmware write protect is controlled through x86 BIOS; otherwise optional)
>> +
>> +All other bits are reserved and should be set to 0.
>> +
>> +HWID (Chrome OS hardware ID)
>> +============================
>> +This control method returns the hardware ID for the Chromebook.
>> +
>> +Arguments:
>> +----------
>> +None
>> +
>> +Result code:
>> +------------
>> +A null-terminated ASCII string containing the hardware ID from the Model-Specific Data area of
>> +EEPROM.
>> +
>> +Note that the hardware ID can be up to 256 characters long, including the terminating null.
>> +
>> +FWID (Chrome OS firmware version)
>> +=================================
>> +This control method returns the firmware version for the rewritable portion of the main
>> +processor firmware.
>> +
>> +Arguments:
>> +----------
>> +None
>> +
>> +Result code:
>> +------------
>> +A null-terminated ASCII string containing the complete firmware version for the rewritable
>> +portion of the main processor firmware.
>> +
>> +FRID (Chrome OS read-only firmware version)
>> +===========================================
>> +This control method returns the firmware version for the read-only portion of the main
>> +processor firmware.
>> +
>> +Arguments:
>> +----------
>> +None
>> +
>> +Result code:
>> +------------
>> +A null-terminated ASCII string containing the complete firmware version for the read-only
>> +(bootstrap + recovery ) portion of the main processor firmware.
>> +
>> +BINF (Chrome OS boot information)
>> +=================================
>> +This control method returns information about the current boot.
>> +
>> +Arguments:
>> +----------
>> +None
>> +
>> +Result code:
>> +------------
>> +
>> +.. code-block::
>> +
>> +   Package {
>> +           Reserved1
>> +           Reserved2
>> +           Active EC Firmware
>> +           Active Main Firmware Type
>> +           Reserved5
>> +   }
>> +
>> +.. flat-table::
>> +   :widths: 1 1 2
>> +   :header-rows: 1
>> +
>> +   * - Field
>> +     - Format
>> +     - Description
>> +
>> +   * - Reserved1
>> +     - DWORD
>> +     - Set to 256 (0x100). This indicates this field is no longer used.
>> +
>> +   * - Reserved2
>> +     - DWORD
>> +     - Set to 256 (0x100). This indicates this field is no longer used.
>> +
>> +   * - Active EC firmware
>> +     - DWORD
>> +     - The EC firmware which was used during boot.
>> +
>> +       - 0 - Read-only (recovery) firmware
>> +       - 1 - Rewritable firmware.
>> +
>> +       Set to 0 if EC firmware is always read-only.
>> +
>> +   * - Active Main Firmware Type
>> +     - DWORD
>> +     - The main firmware type which was used during boot.
>> +
>> +       - 0 - Recovery
>> +       - 1 - Normal
>> +       - 2 - Developer
>> +       - 3 - netboot (factory installation only)
>> +
>> +       Other values are reserved.
>> +
>> +   * - Reserved5
>> +     - DWORD
>> +     - Set to 256 (0x100). This indicates this field is no longer used.
>> +
>> +GPIO (Chrome OS GPIO assignments)
>> +=================================
>> +This control method returns information about Chrome OS specific GPIO assignments for
>> +Chrome OS hardware, so the kernel can directly control that hardware.
>> +
>> +Arguments:
>> +----------
>> +None
>> +
>> +Result code:
>> +------------
>> +.. code-block::
>> +
>> +        Package {
>> +                Package {
>> +                        // First GPIO assignment
>> +                        Signal Type        //DWORD
>> +                        Attributes         //DWORD
>> +                        Controller Offset  //DWORD
>> +                        Controller Name    //ASCIIZ
>> +                },
>> +                ...
>> +                Package {
>> +                        // Last GPIO assignment
>> +                        Signal Type        //DWORD
>> +                        Attributes         //DWORD
>> +                        Controller Offset  //DWORD
>> +                        Controller Name    //ASCIIZ
>> +                }
>> +        }
>> +
>> +Where ASCIIZ means a null-terminated ASCII string.
>> +
>> +.. flat-table::
>> +   :widths: 1 1 2
>> +   :header-rows: 1
>> +
>> +   * - Field
>> +     - Format
>> +     - Description
>> +
>> +   * - Signal Type
>> +     - DWORD
>> +     - Type of GPIO signal
>> +
>> +       - 0x00000001 - Recovery button
>> +       - 0x00000002 - Developer mode switch
>> +       - 0x00000003 - Firmware write protect switch
>> +       - 0x00000100 - Debug header GPIO 0
>> +       - ...
>> +       - 0x000001FF - Debug header GPIO 255
>> +
>> +       Other values are reserved.
>> +
>> +   * - Attributes
>> +     - DWORD
>> +     - Signal attributes as bitfields:
>> +
>> +       - 0x00000001 - Signal is active-high (for button, a GPIO value
>> +         of 1 means the button is pressed; for switches, a GPIO value
>> +         of 1 means the switch is enabled). If this bit is 0, the signal
>> +         is active low. Set to 0 for debug header GPIOs.
>> +
>> +   * - Controller Offset
>> +     - DWORD
>> +     - GPIO number on the specified controller.
>> +
>> +   * - Controller Name
>> +     - ASCIIZ
>> +     - Name of the controller for the GPIO.
>> +       Currently supported names:
>> +       "NM10" - Intel NM10 chip
>> +
>> +VBNV (Chrome OS NVRAM locations)
>> +================================
>> +This control method returns information about the NVRAM (CMOS) locations used to
>> +communicate with the BIOS.
>> +
>> +Arguments:
>> +----------
>> +None
>> +
>> +Result code:
>> +------------
>> +.. code-block::
>> +
>> +        Package {
>> +                NV Storage Block Offset  //DWORD
>> +                NV Storage Block Size    //DWORD
>> +        }
>> +
>> +.. flat-table::
>> +   :widths: 1 1 2
>> +   :header-rows: 1
>> +
>> +   * - Field
>> +     - Format
>> +     - Description
>> +
>> +   * - NV Storage Block Offset
>> +     - DWORD
>> +     - Offset in CMOS bank 0 of the verified boot non-volatile storage block, counting from
>> +       the first writable CMOS byte (that is, offset=0 is the byte following the 14 bytes of
>> +       clock data).
>> +
>> +   * - NV Storage Block Size
>> +     - DWORD
>> +     - Size in bytes of the verified boot non-volatile storage block.
>> +
>> +FMAP (Chrome OS flashmap address)
>> +=================================
>> +This control method returns the physical memory address of the start of the main processor
>> +firmware flashmap.
>> +
>> +Arguments:
>> +----------
>> +None
>> +
>> +NoneResult code:
>> +----------------
>> +A DWORD containing the physical memory address of the start of the main processor firmware
>> +flashmap.
>> +
>> +VDTA (Chrome OS verified boot data)
>> +===================================
>> +This control method returns the verified boot data block shared between the firmware
>> +verification step and the kernel verification step.
>> +
>> +Arguments:
>> +----------
>> +None
>> +
>> +Result code:
>> +------------
>> +A buffer containing the verified boot data block.
>> +
>> +MECK (Management Engine Checksum)
>> +=================================
>> +This control method returns the SHA-1 or SHA-256 hash that is read out of the Management
>> +Engine extend registers during boot. The hash is exported via ACPI so the OS can verify that
>> +the ME firmware has not changed. If Management Engine is not present, or if the firmware was
>> +unable to read the extend registers, this buffer can be zero.
>> +
>> +Arguments:
>> +----------
>> +None
>> +
>> +Result code:
>> +------------
>> +A buffer containing the ME hash.
>> +
>> +MLST (Chrome OS method list)
>> +============================
>> +This control method returns a list of the other control methods supported by the Chrome OS
>> +hardware device.
>> +
>> +Arguments:
>> +----------
>> +None
>> +
>> +Result code:
>> +------------
>> +A package containing a list of null-terminated ASCII strings, one for each control method
>> +supported by the Chrome OS hardware device, not including the MLST method itself.
>> +For this version of the specification, the result is:
>> +
>> +.. code-block::
>> +
>> +        Package {
>> +                "CHSW",
>> +                "FWID",
>> +                "HWID",
>> +                "FRID",
>> +                "BINF",
>> +                "GPIO",
>> +                "VBNV",
>> +                "FMAP",
>> +                "VDTA",
>> +                "MECK"
>> +        }
>> diff --git a/Documentation/firmware-guide/acpi/index.rst b/Documentation/firmware-guide/acpi/index.rst
>> index b053b0c3d6969..b6a42f4ffe032 100644
>> --- a/Documentation/firmware-guide/acpi/index.rst
>> +++ b/Documentation/firmware-guide/acpi/index.rst
>> @@ -29,3 +29,4 @@ ACPI Support
>>     non-d0-probe
>>     extcon-intel-int3496
>>     intel-pmc-mux
>> +   chromeos-acpi-device
>> diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
>> index 5d9dd70e4e0f5..53ddfe6f99b06 100644
>> --- a/drivers/platform/x86/Kconfig
>> +++ b/drivers/platform/x86/Kconfig
>> @@ -322,6 +322,17 @@ config ASUS_NB_WMI
>>  	  If you have an ACPI-WMI compatible Asus Notebook, say Y or M
>>  	  here.
>>  
>> +config CHROMEOS_ACPI
>> +	tristate "ChromeOS specific ACPI extensions"
>> +	depends on ACPI || COMPILE_TEST
>> +	help
>> +	  This driver provides the firmware interface for the services
>> +	  exported through the ChromeOS interfaces when using ChromeOS
>> +	  ACPI firmware.
>> +
>> +	  If you have an ACPI-compatible Chromebook, say Y or M
>> +	  here.
>> +
>>  config ASUS_TF103C_DOCK
>>  	tristate "Asus TF103C 2-in-1 keyboard dock"
>>  	depends on ACPI
>> diff --git a/drivers/platform/x86/Makefile b/drivers/platform/x86/Makefile
>> index fe4d4c8970efa..ae68f4fa9a6c4 100644
>> --- a/drivers/platform/x86/Makefile
>> +++ b/drivers/platform/x86/Makefile
>> @@ -44,6 +44,9 @@ obj-$(CONFIG_EEEPC_WMI)		+= eeepc-wmi.o
>>  # Cisco/Meraki
>>  obj-$(CONFIG_MERAKI_MX100)	+= meraki-mx100.o
>>  
>> +# Chrome
>> +obj-$(CONFIG_CHROMEOS_ACPI)	+= chromeos_acpi.o
>> +
>>  # Dell
>>  obj-$(CONFIG_X86_PLATFORM_DRIVERS_DELL)		+= dell/
>>  
>> diff --git a/drivers/platform/x86/chromeos_acpi.c b/drivers/platform/x86/chromeos_acpi.c
>> new file mode 100644
>> index 0000000000000..de86119a446b8
>> --- /dev/null
>> +++ b/drivers/platform/x86/chromeos_acpi.c
>> @@ -0,0 +1,513 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * ChromeOS specific ACPI extensions
>> + *
>> + * Copyright 2011 Google, Inc.
>> + * Copyright 2020-2022 Google LLC
>> + *
>> + * This file is a rework and part of the code is ported from chromeos-3.18
>> + * kernel and was originally written by Vadim Bendebury <vbendeb@chromium.org>.
>> + *
>> + * This driver attaches to the ChromeOS ACPI device and then exports the
>> + * values reported by the ACPI in a sysfs directory. All values are
>> + * presented in the string form (numbers as decimal values) and can be
>> + * accessed as the contents of the appropriate read only files in the
>> + * sysfs directory tree.
>> + */
>> +
>> +#include <linux/acpi.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/kernel.h>
>> +#include <linux/list.h>
>> +#include <linux/module.h>
>> +
>> +/*
>> + * ACPI method name for MLST; the response for this method is a package of
>> + * strings listing the methods which should be reflected in sysfs.
>> + */
>> +#define MLST "MLST"
>> +
>> +/*
>> + * The default list of methods the ChromeOS ACPI device is supposed to export,
>> + * if the MLST method is not present or is poorly formed.  The MLST method
>> + * itself is included, to aid in debugging.
>> + */
>> +static char *chromeos_acpi_default_methods[] = {
>> +	"CHSW", "HWID", "BINF", "GPIO", "CHNV", "FWID", "FRID", MLST
>> +};
>> +
>> +/*
>> + * Representation of a single sysfs attribute. In addition to the standard
>> + * bin_attribute structure has a list of these structures (to keep track for
>> + * de-allocation when removing the driver) and a pointer to the actual
>> + * attribute name and value, reported when accessing the appropriate sysfs
>> + * file.
>> + */
>> +struct chromeos_acpi_attribute {
>> +	struct bin_attribute bin_attr;
>> +	struct list_head list;
>> +	char *name;
>> +	char *data;
>> +};
>> +
>> +/*
>> + * Representation of a sysfs attribute group (a sub directory in the device's
>> + * sysfs directory). In addition to the standard structure has lists to allow
>> + * to keep track of the allocated structures.
>> + */
>> +struct chromeos_acpi_attribute_group {
>> +	struct attribute_group group;
>> +	struct list_head attribs;
>> +	struct list_head list;
>> +	char *name;
>> +};
>> +
>> +/*
>> + * This is the main structure, we use it to store data and adds links pointing
>> + * at lists of allocated attributes and attribute groups.
>> + */
>> +struct chromeos_acpi_dev {
>> +	struct chromeos_acpi_attribute_group *root;
>> +	const struct attribute_group **dev_groups;
>> +	struct list_head groups;
>> +	unsigned int num_groups;
>> +	unsigned int num_attrs;
>> +};
>> +
>> +static struct chromeos_acpi_dev chromeos_acpi;
>> +
>> +static ssize_t chromeos_acpi_read_bin_attribute(struct file *filp,
>> +						struct kobject *kobj,
>> +						struct bin_attribute *bin_attr,
>> +						char *buffer, loff_t pos,
>> +						size_t count)
>> +{
>> +	struct chromeos_acpi_attribute *info = bin_attr->private;
>> +
>> +	return memory_read_from_buffer(buffer, count, &pos, info->data,
>> +				       info->bin_attr.size);
>> +}
>> +
>> +static char *chromeos_acpi_gen_file_name(char *name, int count, int index)
>> +{
>> +	char *str;
>> +
>> +	if (count == 1)
>> +		str = kstrdup(name, GFP_KERNEL);
>> +	else
>> +		str = kasprintf(GFP_KERNEL, "%s.%d", name, index);
>> +
>> +	return str;
>> +}
>> +
>> +static int
>> +chromeos_acpi_add_attr(struct chromeos_acpi_attribute_group *aag,
>> +		       union acpi_object *element, char *name,
>> +		       int count, int index)
>> +{
>> +	struct chromeos_acpi_attribute *info;
>> +	char buffer[24]; /* enough to store a u64 and null character */
>> +	int length;
>> +	int ret;
>> +
>> +	/* Files BINF.{0,1,4} are historical and no longer used. */
>> +	if (!strcmp(name, "BINF") && (index == 0 || index == 1 || index == 4))
>> +		return 0;
>> +
>> +	info = kzalloc(sizeof(*info), GFP_KERNEL);
>> +	if (!info)
>> +		return -ENOMEM;
>> +
>> +	info->name = chromeos_acpi_gen_file_name(name, count, index);
>> +	if (!info->name) {
>> +		ret = -ENOMEM;
>> +		goto free_attribute;
>> +	}
>> +	sysfs_bin_attr_init(&info->bin_attr);
>> +	info->bin_attr.attr.name = info->name;
>> +	info->bin_attr.attr.mode = 0444;
>> +
>> +	switch (element->type) {
>> +	case ACPI_TYPE_BUFFER:
>> +		length = element->buffer.length;
>> +		info->data = kmemdup(element->buffer.pointer,
>> +				     length, GFP_KERNEL);
>> +		break;
>> +	case ACPI_TYPE_INTEGER:
>> +		length = snprintf(buffer, sizeof(buffer), "%d",
>> +				  (int)element->integer.value);
>> +		info->data = kmemdup(buffer, length, GFP_KERNEL);
>> +		break;
>> +	case ACPI_TYPE_STRING:
>> +		length = element->string.length + 1;
>> +		info->data = kstrdup(element->string.pointer, GFP_KERNEL);
>> +		break;
>> +	default:
>> +		ret = -EINVAL;
>> +		goto free_attr_name;
>> +	}
>> +
>> +	if (!info->data) {
>> +		ret = -ENOMEM;
>> +		goto free_attr_name;
>> +	}
>> +
>> +	info->bin_attr.size = length;
>> +	info->bin_attr.read = chromeos_acpi_read_bin_attribute;
>> +	info->bin_attr.private = info;
>> +
>> +	INIT_LIST_HEAD(&info->list);
>> +
>> +	list_add(&info->list, &aag->attribs);
>> +	return 0;
>> +
>> +free_attr_name:
>> +	kfree(info->name);
>> +free_attribute:
>> +	kfree(info);
>> +	return ret;
>> +}
>> +
>> +static void
>> +chromeos_acpi_remove_attribs(struct chromeos_acpi_attribute_group *aag)
>> +{
>> +	struct chromeos_acpi_attribute *attr, *tmp_attr;
>> +
>> +	list_for_each_entry_safe(attr, tmp_attr, &aag->attribs, list) {
>> +		kfree(attr->name);
>> +		kfree(attr->data);
>> +		kfree(attr);
>> +	}
>> +}
>> +
>> +static int
>> +chromeos_acpi_add_attribs_to_group(struct chromeos_acpi_attribute_group *aag,
>> +				   unsigned int num_attrs)
>> +{
>> +	struct chromeos_acpi_attribute *attr;
>> +	int count = 0;
>> +
>> +	aag->group.bin_attrs = kcalloc(num_attrs + 1,
>> +				       sizeof(*aag->group.bin_attrs),
>> +				       GFP_KERNEL);
>> +	if (!aag->group.bin_attrs)
>> +		return -ENOMEM;
>> +
>> +	list_for_each_entry(attr, &aag->attribs, list) {
>> +		aag->group.bin_attrs[count] = &attr->bin_attr;
>> +		count++;
>> +	}
>> +
>> +	chromeos_acpi.num_groups++;
>> +	list_add(&aag->list, &chromeos_acpi.groups);
>> +
>> +	return 0;
>> +}
>> +
>> +/**
>> + * chromeos_acpi_add_group() - Create a sysfs group including attributes
>> + *			       representing a nested ACPI package
>> + *
>> + * @obj: Package contents as returned by ACPI
>> + * @name: Name of the group
>> + * @num_attrs: Number of attributes of this package
>> + * @index: Index number of this particular group
>> + *
>> + * The created group is called @name in case there is a single instance, or
>> + * @name.@index otherwise.
>> + *
>> + * All group and attribute storage allocations are included in the lists for
>> + * tracking of allocated memory.
>> + *
>> + * Return: 0 on success, negative errno on failure.
>> + */
>> +static int chromeos_acpi_add_group(union acpi_object *obj, char *name,
>> +				   int num_attrs, int index)
>> +{
>> +	struct chromeos_acpi_attribute_group *aag;
>> +	union acpi_object *element;
>> +	int i, count, ret;
>> +
>> +	aag = kzalloc(sizeof(*aag), GFP_KERNEL);
>> +	if (!aag)
>> +		return -ENOMEM;
>> +	aag->name = chromeos_acpi_gen_file_name(name, num_attrs, index);
>> +	if (!aag->name) {
>> +		ret = -ENOMEM;
>> +		goto free_group;
>> +	}
>> +
>> +	INIT_LIST_HEAD(&aag->attribs);
>> +	INIT_LIST_HEAD(&aag->list);
>> +
>> +	count = obj->package.count;
>> +	element = obj->package.elements;
>> +	for (i = 0; i < count; i++, element++) {
>> +		ret = chromeos_acpi_add_attr(aag, element, name, count, i);
>> +		if (ret)
>> +			goto free_group_attr;
>> +	}
>> +
>> +	aag->group.name = aag->name;
>> +
>> +	ret = chromeos_acpi_add_attribs_to_group(aag, count);
>> +	if (ret)
>> +		goto free_group_attr;
>> +
>> +	return 0;
>> +
>> +free_group_attr:
>> +	chromeos_acpi_remove_attribs(aag);
>> +	kfree(aag->name);
>> +free_group:
>> +	kfree(aag);
>> +	return ret;
>> +}
>> +
>> +static void chromeos_acpi_remove_groups(void)
>> +{
>> +	struct chromeos_acpi_attribute_group *aag, *tmp_aag;
>> +
>> +	list_for_each_entry_safe(aag, tmp_aag, &chromeos_acpi.groups, list) {
>> +		chromeos_acpi_remove_attribs(aag);
>> +		kfree(aag->group.bin_attrs);
>> +		kfree(aag->name);
>> +		kfree(aag);
>> +	}
>> +}
>> +
>> +/**
>> + * chromeos_acpi_handle_package() - Create sysfs group including attributes
>> + *				    representing an ACPI package
>> + *
>> + * @pdev: Platform device
>> + * @obj: Package contents as returned by ACPI
>> + * @name: Name of the group
>> + *
>> + * Scalar objects included in the package get sysfs attributes created for
>> + * them. Nested packages are passed to a function creating a sysfs group per
>> + * package.
>> + *
>> + * Return: 0 on success, negative errno on failure.
>> + */
>> +static int chromeos_acpi_handle_package(struct platform_device *pdev,
>> +					union acpi_object *obj, char *name)
>> +{
>> +	struct device *dev = &pdev->dev;
>> +	int count = obj->package.count;
>> +	union acpi_object *element;
>> +	int i, ret;
>> +
>> +	element = obj->package.elements;
>> +	for (i = 0; i < count; i++, element++) {
>> +		if (element->type == ACPI_TYPE_BUFFER ||
>> +		    element->type == ACPI_TYPE_STRING ||
>> +		    element->type == ACPI_TYPE_INTEGER) {
>> +			/* Create a single attribute in the root directory */
>> +			ret = chromeos_acpi_add_attr(chromeos_acpi.root,
>> +						     element, name,
>> +						     count, i);
>> +			if (ret) {
>> +				dev_err(dev, "error adding attributes (%d)\n",
>> +					ret);
>> +				return ret;
>> +			}
>> +			chromeos_acpi.num_attrs++;
>> +		} else if (element->type == ACPI_TYPE_PACKAGE) {
>> +			/* Create a group of attributes */
>> +			ret = chromeos_acpi_add_group(element, name, count, i);
>> +			if (ret) {
>> +				dev_err(dev, "error adding a group (%d)\n",
>> +					ret);
>> +				return ret;
>> +			}
>> +		} else {
>> +			if (ret) {
>> +				dev_err(dev, "error on element type (%d)\n",
>> +					ret);
>> +				return -EINVAL;
>> +			}
>> +		}
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +/**
>> + * chromeos_acpi_add_method() - Evaluate an ACPI method and create sysfs
>> + *				attributes
>> + *
>> + * @pdev: Platform device
>> + * @name: Name of the method to evaluate
>> + *
>> + * Return: 0 on success, non-zero on failure
>> + */
>> +static int chromeos_acpi_add_method(struct platform_device *pdev, char *name)
>> +{
>> +	struct device *dev = &pdev->dev;
>> +	struct acpi_buffer output = { ACPI_ALLOCATE_BUFFER, NULL };
>> +	acpi_status status;
>> +	int ret = 0;
>> +
>> +	status = acpi_evaluate_object(ACPI_COMPANION(&pdev->dev)->handle, name, NULL, &output);
>> +	if (ACPI_FAILURE(status)) {
>> +		dev_err(dev, "failed to retrieve %s (%d)\n", name, status);
>> +		return status;
>> +	}
>> +
>> +	if (((union acpi_object *)output.pointer)->type == ACPI_TYPE_PACKAGE)
>> +		ret = chromeos_acpi_handle_package(pdev, output.pointer, name);
>> +
>> +	kfree(output.pointer);
>> +	return ret;
>> +}
>> +
>> +/**
>> + * chromeos_acpi_process_mlst() - Evaluate the MLST method and add methods
>> + *				  listed in the response
>> + *
>> + * @pdev: Platform device
>> + *
>> + * Returns: 0 if successful, non-zero if error.
>> + */
>> +static int chromeos_acpi_process_mlst(struct platform_device *pdev)
>> +{
>> +	struct chromeos_acpi_attribute_group *aag;
>> +	char name[ACPI_NAMESEG_SIZE + 1];
>> +	union acpi_object *element, *obj;
>> +	struct device *dev = &pdev->dev;
>> +	struct acpi_buffer output = { ACPI_ALLOCATE_BUFFER, NULL };
>> +	acpi_status status;
>> +	int ret = 0;
>> +	int size;
>> +	int i;
>> +
>> +	status = acpi_evaluate_object(ACPI_COMPANION(&pdev->dev)->handle, MLST, NULL,
>> +				      &output);
>> +	if (ACPI_FAILURE(status))
>> +		return status;
>> +
>> +	obj = output.pointer;
>> +	if (obj->type != ACPI_TYPE_PACKAGE) {
>> +		ret = -EINVAL;
>> +		goto free_acpi_buffer;
>> +	}
>> +
>> +	element = obj->package.elements;
>> +	for (i = 0; i < obj->package.count; i++, element++) {
>> +		if (element->type == ACPI_TYPE_STRING) {
>> +			size = min(element->string.length + 1,
>> +				   (u32)ACPI_NAMESEG_SIZE + 1);
>> +			strscpy(name, element->string.pointer, size);
>> +			ret = chromeos_acpi_add_method(pdev, name);
>> +			if (ret) {
>> +				chromeos_acpi_remove_groups();
>> +				break;
>> +			}
>> +		}
>> +	}
>> +
>> +	/* Add root attributes to the main group */
>> +	ret = chromeos_acpi_add_attribs_to_group(chromeos_acpi.root,
>> +						 chromeos_acpi.num_attrs);
>> +	if (ret)
>> +		goto free_acpi_buffer;
>> +
>> +	chromeos_acpi.dev_groups = kcalloc(chromeos_acpi.num_groups + 1,
>> +					   sizeof(struct attribute_group),
>> +					   GFP_KERNEL);
>> +
>> +	i = 0;
>> +	list_for_each_entry(aag, &chromeos_acpi.groups, list) {
>> +		chromeos_acpi.dev_groups[i] = &aag->group;
>> +		i++;
>> +	}
>> +
>> +	ret = sysfs_create_groups(&dev->kobj, chromeos_acpi.dev_groups);
>> +	if (ret) {
>> +		kfree(chromeos_acpi.dev_groups);
>> +
>> +		/* Remove allocated chromeos acpi groups and attributes */
>> +		chromeos_acpi_remove_groups();
>> +	}
>> +
>> +free_acpi_buffer:
>> +	kfree(output.pointer);
>> +	return ret;
>> +}
>> +
>> +static int chromeos_acpi_device_probe(struct platform_device *pdev)
>> +{
>> +	struct chromeos_acpi_attribute_group *aag;
>> +	struct device *dev = &pdev->dev;
>> +	int i, ret;
>> +
>> +	aag = kzalloc(sizeof(*aag), GFP_KERNEL);
>> +	if (!aag)
>> +		return -ENOMEM;
>> +
>> +	INIT_LIST_HEAD(&aag->attribs);
>> +	INIT_LIST_HEAD(&aag->list);
>> +	INIT_LIST_HEAD(&chromeos_acpi.groups);
>> +
>> +	chromeos_acpi.root = aag;
>> +
>> +	/*
>> +	 * Attempt to add methods by querying the device's MLST method
>> +	 * for the list of methods.
>> +	 */
>> +	if (!chromeos_acpi_process_mlst(pdev))
>> +		return 0;
>> +
>> +	dev_dbg(dev, "falling back to default list of methods\n");
>> +
>> +	for (i = 0; i < ARRAY_SIZE(chromeos_acpi_default_methods); i++) {
>> +		ret = chromeos_acpi_add_method(pdev,
>> +					       chromeos_acpi_default_methods[i]);
>> +		if (ret) {
>> +			dev_err(dev, "failed to add default methods (%d)\n",
>> +				ret);
>> +			goto free_group_root;
>> +		}
>> +	}
>> +
>> +	return 0;
>> +
>> +free_group_root:
>> +	kfree(chromeos_acpi.root);
>> +	return ret;
>> +}
>> +
>> +static int chromeos_acpi_device_remove(struct platform_device *pdev)
>> +{
>> +	/* Remove sysfs groups */
>> +	sysfs_remove_groups(&pdev->dev.kobj, chromeos_acpi.dev_groups);
>> +	kfree(chromeos_acpi.dev_groups);
>> +
>> +	/* Remove allocated chromeos acpi groups and attributes */
>> +	chromeos_acpi_remove_groups();
>> +
>> +	return 0;
>> +}
>> +
>> +/* GGL is valid PNP ID of Google. PNP ID can be used with the ACPI devices. */
>> +static const struct acpi_device_id chromeos_device_ids[] = {
>> +	{ "GGL0001", 0 },
>> +	{ }
>> +};
>> +MODULE_DEVICE_TABLE(acpi, chromeos_device_ids);
>> +
>> +static struct platform_driver chromeos_acpi_device_driver = {
>> +	.probe = chromeos_acpi_device_probe,
>> +	.remove = chromeos_acpi_device_remove,
>> +	.driver = {
>> +		.name   = "chromeos-acpi",
>> +		.acpi_match_table = ACPI_PTR(chromeos_device_ids)
>> +	}
>> +};
>> +
>> +module_platform_driver(chromeos_acpi_device_driver);
>> +
>> +MODULE_AUTHOR("Enric Balletbo i Serra <enric.balletbo@collabora.com>");
>> +MODULE_LICENSE("GPL");
>> +MODULE_DESCRIPTION("ChromeOS specific ACPI extensions");
> 

-- 
Muhammad Usama Anjum