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 and the hardware ID is GOOG0016. The following ACPI objects are supported:

Supported ACPI Objects

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:

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:

Package {
        Reserved1
        Reserved2
        Active EC Firmware
        Active Main Firmware Type
        Reserved5
}

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:

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.

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:

Package {
        NV Storage Block Offset  //DWORD
        NV Storage Block Size    //DWORD
}

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:

Package {
        "CHSW",
        "FWID",
        "HWID",
        "FRID",
        "BINF",
        "GPIO",
        "VBNV",
        "FMAP",
        "VDTA",
        "MECK"
}