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+.. 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 a valid PNP ID of Google.
+PNP ID can be used with the ACPI devices according 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 protection was disabled when x86 firmware booted. (required if
+ firmware write protection 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 protection 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 extended 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 extended 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"
+ }