tree: 2db2e29a266bbc50b20e2cf57b56144de97f830a [path history] [tgz]
  1. .gitignore
  5. PRESUBMIT.cfg
  8. cros_config_host/
  14. libcros_config/

Chrome OS Configuration -- Master Chrome OS Configuration tools / library

This is the homepage/documentation for chromeos-config which provides access to the master configuration for Chrome OS.

Internal Documentation

See the design doc for information about the design. This is accessible only within Google. A public page will be published to once the feature is complete and launched.

Important classes

See CrosConfig for the class to use to access configuration strings on a target. See for access to the config on a host or during a build.

CLI Usage

There are two CLIs built for Chrome OS configuration access, cros_config for use on the target, and cros_config_host for use on the host/during building. See the --help for each tool respectively for help on usage.


libcros_config will emit a lot of debugging log messages if you set the CROS_CONFIG_DEBUG environment variable to a non-empty value before calling into the library.

Config Schema

Chrome OS config is now YAML based. If you're still using the Flat Device Tree (FDT) based implementation, see the v1 schema description below.

The following components make up the YAML based chromeos-config support:

YAML Source

The YAML source is designed for human maintainability. It allows for easy config sharing across many different devices (via anchors).

For background on YAML, see: Learn YAML in 10 minutes

The source is generally located at: overlay-${BOARD}/chromeos-base/chromeos-config-bsp/files/model.yaml

Beyond the normal features of YAML, there are a few custom features supported that allow for even better re-use and expressiveness in the YAML config.

  1. Templating - Templating allows config to be shared by letting callers reference variables in the config, which are then evaluated on a per device/sku/product basis.

    The basic syntax is:

    some-element: "{{some-template-variable}}"

    Valid template variables are any YAML elements that are currently in scope. When generating config, scope is evaluated in the following order:

    1. sku
    2. config (this is recursive ... any variable at any level can be referenced)
    3. device
    4. product

    This order allows shared anchors to define default variables that are then optionally overridden by either the device or product scope.

  2. Local Variables - These are variables that are only used for templating and are dropped in the final JSON output. Variables starting with ‘$’ are considered local and are ignored after template evaluation. The basic syntax is:

      $some-local-variable: "some-value"
      some-element: "{{$some-local-variable}}"

    This supports the following:

    1. Defining local variables that are re-used in multiple places (e.g. file paths).
    2. Re-using common config (e.g. ‘identity’) where the variable value isn't known until the device/product/sku variables come into scope (e.g. $sku-id).
  3. File Imports - File imports allow common snippets of YAML to be shared across multiple different implementations. File importing works the same as if the YAML files were cat'd together and then evaluated. File importing is recursive also, so it will support importing files that import other files. Import paths must be relative to the file that specifies the import.

      - "some_common_import_file.yaml"
      - "../common/some_other_common_import_file.yaml"

The following provides a simple example of a config using both core YAML features and the custom features described above.

common_config: &common_config
  name: "{{$device-name}}"
  brand-code: "{{$brand-code}}"
    platform-name: "SomePlatform"
    smbios-name-match: "SomePlatform"
    sku-id: "{{$sku-id}}"
    key-id: "{{$key-id}}"
    signature-id: "{{name}}"
    - $device-name: "SomeDevice"
        - $brand-code: "YYYY"
          $key-id: "SOME-KEY-ID"
        - $sku-id: 0
            <<: *common_config
            wallpaper: "some-wallpaper"
        - $sku-id: 1
          config: *common_config

When this YAML is evaluated, it will fully expand out as the following:

    - name: "SomeDevice"
      brand-code: "YYYY"
        platform-name: "SomePlatform"
        smbios-name-match: "SomePlatform"
        sku-id: 0
        key-id: "SOME-KEY-ID"
        signature-id: "SomeDevice"
      wallpaper: "some-wallpaper"
    - name: "SomeDevice"
      brand-code: "YYYY"
        platform-name: "SomePlatform"
        smbios-name-match: "SomePlatform"
        sku-id: 1
        key-id: "SOME-KEY-ID"
        signature-id: "SomeDevice"

YAML Merging (multiple source YAML files)

There are various cases where it makes sense to manage YAML config across multiple different repos in separate YAML files.


  • Permissions based control via git repo access to specific config
  • Extending overlays for device customization (e.g. Moblab)

This is supported through cros_config_schema tool and is invoked as part of the chromeos-config ebuild.

Using normal portage ebuilds/config, users can install as many YAML files as they wish to be merged together into: /usr/share/chromeos-config/yaml


  • models.yaml
  • models-private.yaml (private config overlaid on the public config)

These files are then merged together based on their lexicographic name order.

Merging of YAML files applies the following characteristics:

  1. Order is important. If two files supply the same config, the last file wins.

  2. Identity is important. Config is merged based on ONE OF the following:

    1. name - If the name attribute matches, the config is merged
    2. identity - all fields of identity must match explicitly for code generation purposes. The fields are documented in identity. All fields that are present in the second file must be present in the first file. Note that a null value (the field is not present) and an empty string (the field is assigned the value of "") are not considered a match for code generation purposes.

For a detailed example of how merging works, see the following test files:

  1. test_merge_base.yaml - First file passed to the merge routine.
  2. test_merge_overlay.yaml - Second file passed (winner of any conflicts).
  3. test_merge.json - Result generated from the merge.

YAML Transform (to JSON)

In addition to the templating evaluation discussed above, the YAML is converted to JSON before it's actually used in chromeos-config. This fully evaluated/de-normalized form accomplishes a couple things:

  1. It provides a great diffable format so it's obvious what changes are actually applied if, for example, a shared config element was changed.
  2. It keeps the consumer code very simple (host and runtime). The code just matches the identity attributes and then uses the respective config. It never has to care about re-use or config sharing.

The transform algorithm works as follows:

  • FOREACH device in chromeos/devices
    • FOREACH product in device/products
      • FOREACH sku in device/skus
        • sku varibles are put into scope
        • config variables are put into scope
        • device variables are put into scope
        • product variables are put into scope
        • with sku/config
          • config template variables are evaluated
          • the config contents are captured and stored in the resulting json

Based on this algorithm, some key points are:

  • Only ‘sku/config’ actually lands in the JSON output. All other YAML structure supports the generation of the sku/config payloads.
  • ‘product’ generally defines identity/branding information only. The main reason multiple products are supported is for the whitelabel case.

Making changes to a YAML model file

When modifying a model.yaml file there are few steps that need to be taken to manifest the change in a board target. Since the actual work to combine and process the YAML files is done in the chromeos-config ebuild, it needs to be remerged after the input YAML has been modified.

  1. Start cros_workon on the ebuild where your source model.yaml lives: cros_workon start chromeos-base/chrome-config-bsp-{BOARD}
  2. Make and install your incremental changes: cros_workon_make chromeos-base/chrome-config-bsp-{BOARD} --install
  3. Remerge the chromeos-config ebuild: emerge-$BORAD chromeos-config

Note: The config-bsp overlay path may be slightly different depending on the board and if it is public or private.

Schema Validation

The config is evaluated against a schema located at: chromeos-config/cros_config_host/cros_config_schema.yaml

NOTE: The schema is managed in YAML because it's easier to edit than JSON.

Only the transformed JSON is actually evaluated against the schema. Authors can do whatever makes sense in the YAML (from a sharing perspective) as long as it generates compliant JSON that passes the schema validation.

The schema documentation is auto-generated (and put into this file) via: python -m cros_config_host.generate_schema_doc -o

The schema definition is below:

CrOS Config Type Definitions (v2)


In the tables below,

  • Build-only attributes get automatically stripped from the platform JSON as part of the build.


AttributeTypeRegExRequiredOneof GroupBuild-onlyDescription
brand-codestringFalseFalseBrand code of the model (also called RLZ code).
hardware-propertieshardware-propertiesFalseFalseContains boolean flags or enums for hardware properties of this board, for example if it's convertible, has a touchscreen, has a camera, etc. This information is used to auto-generate C code that is consumed by the EC build process in order to do run-time configuration. If a value is defined within a config file, but not for a specific model, that value will be assumed to be false for that model. If a value is an enum and is not specified for a specific model, it will default to “none”. All properties must be booleans or enums. If non-boolean properties are desired, the generation code in must be updated to support them.
identityidentityFalseFalseDefines attributes that are used by cros_config to detect the identity of the platform and which corresponding config should be used. This tuple must either contain x86 properties only or ARM properties only.
namestring^[_a-zA-Z0-9]{3,}TrueFalseUnique name for the given model.
oem-idstring[0-9]+FalseFalseSome projects store SKU ID, OEM ID and Board Revision in an EEPROM and only SKU ID can be updated in the factory and RMA flow but others should be pre-flashed in the chip level. In this case, we would like to validate whether oem-id here from the updated SKU ID matches the one in the EEPROM so we can prevent this device from being updated to another OEM's devices.
powerpowerFalseFalseWARNING -- This config contains unvalidated settings, which is not a correct usage pattern, but this will be used in the interim until a longer term solution can be put in place where the overall schema can be single sourced (for the YAML and C++ that uses it); likely though some type of code generation. SUMMARY -- Contains power_manager device settings. This is the new mechanism used in lieu of the previous file based implementation (via powerd-prefs). Power manager will first check for a property in this config, else it will revert to the file based mechanism (via the powerd-prefs setting). This provides more flexibility in sharing power settings across different devices that share the same build overlay. Any property can be overridden from - src/platform2/power_manager/default_prefs or src/platform2/power_manager/optional_prefs For details about each setting property, see - src/platform2/power_manager/common/power_constants.h For examples on setting these properties (including multiline examples), see the power config example in libcros_config/test.yaml
powerd-prefsstringFalseFalsePowerd config that should be used.
regulatory-labelstringFalseFalseBase name of the directory containing the regulatory label files to show on this device.
test-labelstringFalseFalseTest alias (model) label that will be applied in Autotest and reported for test results.
wallpaperstringFalseFalseBase filename of the default wallpaper to show on this device.


AttributeTypeRegExRequiredOneof GroupBuild-onlyDescription
filesarray - filesFalseTrue


AttributeTypeRegExRequiredOneof GroupBuild-onlyDescription
devicestringFalseFalseDevice name to report in ‘ro.product.device’. This is often ‘{product}_cheets’ but it can be something else if desired.
first-api-levelstringFalseFalseThe first Android API level that this model shipped with.
marketing-namestringFalseFalseName of this model as it is called in the market, reported in ‘ro.product.model’. This often starts with ‘{oem}’.
metrics-tagstringFalseFalseTag to use to track metrics for this model. The tag can be shared across many devices if desired, but this will result in larger granularity for metrics reporting. Ideally the metrics system should support collation of metrics with different tags into groups, but if this is not supported, this tag can be used to achieve the same end. This is reported in ‘ro.product.metrics.tag’.
oemstringFalseFalseOriginal Equipment Manufacturer for this model. This generally means the OEM name printed on the device.
productstringFalseFalseProduct name to report in ‘’. This may be the device name, or it can be something else, to allow several devices to be grouped into one product.


AttributeTypeRegExRequiredOneof GroupBuild-onlyDescription
destinationstringFalseTrueInstallation path for the file on the system image.
sourcestringFalseTrueSource of the file relative to the build system.


AttributeTypeRegExRequiredOneof GroupBuild-onlyDescription


AttributeTypeRegExRequiredOneof GroupBuild-onlyDescription
cras-config-dirstringTrueFalseSubdirectory for model-specific configuration.
disable-profilestringFalseFalseOptional --disable_profile parameter for CRAS deamon.
filesarray - filesFalseTrue
ucm-suffixstringFalseFalseOptional UCM suffix used to determine model specific config.


AttributeTypeRegExRequiredOneof GroupBuild-onlyDescription
destinationstringFalseTrueInstallation path for the file on the system image.
sourcestringFalseTrueSource of the file relative to the build system.


AttributeTypeRegExRequiredOneof GroupBuild-onlyDescription


AttributeTypeRegExRequiredOneof GroupBuild-onlyDescription
build-pathstringTrueTrueSource of the file relative to the build system.
system-pathstringTrueFalseInstallation path for the file on the system image.


AttributeTypeRegExRequiredOneof GroupBuild-onlyDescription
clockstringFalseFalseSpecified the camera clock on the model.
config-pathstringFalseFalseSpecified the camera configuration file path on the model.
countintegerFalseFalseSpecified the number of cameras on the model.


AttributeTypeRegExRequiredOneof GroupBuild-onlyDescription
bcs-overlaystringFalseTrueBCS overlay path used to determine BCS file path for binary firmware downloads.
ec-ro-imagestringFalseTrueName of the file located in BCS under the respective bcs-overlay.
key-idstringFalseTrueKey ID from the signer key set that is used to sign the given firmware image.
main-ro-imagestringFalseTrueName of the file located in BCS under the respective bcs-overlay.
main-rw-imagestringFalseTrueName of the file located in BCS under the respective bcs-overlay.
namestringFalseTrueThis is a human-recognizable name used to refer to the firmware. It will be used when generating the shellball via firmware packer. Mainly, this is only for compatibility testing with device tree (since DT allowed firmwares to be named).
no-firmwarebooleanFalseTrueIf present this indicates that this model has no firmware at present. This means that it will be omitted from the firmware updater (chromeos-firmware- ebuild) and it will not be included in the signer instructions file sent to the signer. This option is often useful when a model is first added, since it may not have firmware at that point.
pd-ro-imagestringFalseTrueName of the file located in BCS under the respective bcs-overlay.


AttributeTypeRegExRequiredOneof GroupBuild-onlyDescription
basestringFalseTrueBuild target of the base EC firmware for a detachable device, that will be considered dirty when building/testing
corebootstringFalseTrueBuild target that will be considered dirty when building/testing locally.
cr50stringFalseTrueBuild target that will be considered dirty when building/testing locally.
depthchargestringFalseTrueBuild target that will be considered dirty when building/testing locally.
ecstringFalseTrueBuild target that will be considered dirty when building/testing locally.
ec_extrasarray - stringFalseTrueExtra EC build targets to build within chromeos-ec.
ishstringFalseTrueBuild target that will be considered dirty when building/testing locally.
libpayloadstringFalseTrueBuild target that will be considered dirty when building/testing locally.
u-bootstringFalseTrueBuild target that will be considered dirty when building/testing locally.


AttributeTypeRegExRequiredOneof GroupBuild-onlyDescription
key-idstringTrueTrueKey ID from the signer key set that is used to sign the given firmware image.
sig-id-in-customization-idbooleanFalseTrueIndicates that this model cannot be decoded by the mapping table. Instead the model is stored in the VPD (Vital Product Data) region in the customization_id property. This allows us to determine the model to use in the factory during the finalization stage. Note that if the VPD is wiped then the model will be lost. This may mean that the device will revert back to a generic model, or may not work. It is not possible in general to test whether the model in the VPD is correct at run-time. We simply assume that it is. The advantage of using this property is that no hardware changes are needed to change one model into another. For example we can create 20 different whitelabel boards, all with the same hardware, just by changing the customization_id that is written into SPI flash.
signature-idstringTrueTrueID used to generate keys/keyblocks in the firmware signing output. This is also the value provided to mosys platform signature for the script.


AttributeTypeRegExRequiredOneof GroupBuild-onlyDescription
has-base-accelerometerbooleanFalseFalseIs there an accelerometer in the base of the device.
has-base-gyroscopebooleanFalseFalseIs there a gyroscope in the base of the device.
has-base-magnetometerbooleanFalseFalseIs there a magnetometer in the base of the device.
has-fingerprint-sensorbooleanFalseFalseIs there a fingerprint sensor on the device.
has-lid-accelerometerbooleanFalseFalseIs there an accelerometer in the lid of the device.
has-lid-gyroscopebooleanFalseFalseIs there a gyroscope in the lid of the device.
has-lid-magnetometerbooleanFalseFalseIs there a magnetometer in the lid of the device.
has-touchscreenbooleanFalseFalseDoes the device have a touchscreen.
is-lid-convertiblebooleanFalseFalseCan the lid be rotated 360 degrees.
stylus-categorystringFalseFalseDenotes the category of stylus this device contains.


AttributeTypeRegExRequiredOneof GroupBuild-onlyDescription
customization-idstringFalsex86False‘customization_id’ value set in the VPD for non-unibuild Zergs and Whitelabels. Deprecated for use in new products since 2017/07/26.
platform-namestringFalsex86FalseDefines the name that is reported by ‘mosys platform name’ This is typically the reference design name with the first letter capitalized
sku-idintegerFalsex86FalseSKU/Board strapping pins configured during board manufacturing. Minimum value: -0x1. Maximum value: 0x7fffffff.
smbios-name-matchstringFalsex86False[x86] Firmware name built into the firmware and reflected back out in the SMBIOS tables.
whitelabel-tagstringFalsex86False‘whitelabel_tag’ value set in the VPD, to add Whitelabel branding over an unbranded base model.
customization-idstringFalseARMFalse‘customization_id’ value set in the VPD for non-unibuild Zergs and Whitelabels. Deprecated for use in new products since 2017/07/26.
device-tree-compatible-matchstringFalseARMFalse[ARM] String pattern (partial) that is matched against the contents of /proc/device-tree/compatible on ARM devices.
platform-namestringFalseARMFalseDefines the name that is reported by ‘mosys platform name’ This is typically the reference design name with the first letter capitalized
sku-idintegerFalseARMFalseSKU/Board strapping pins configured during board manufacturing. Minimum value: -0x1. Maximum value: 0x7fffffff.
whitelabel-tagstringFalseARMFalse‘whitelabel_tag’ value set in the VPD, to add Whitelabel branding over an unbranded base model.


AttributeTypeRegExRequiredOneof GroupBuild-onlyDescription
firmware-variantstringFalseFalseVariant of the modem firmware to be used. This value is read by modemfwd to match against the variant field of a firmware entry in a firmware manifest. In most cases, we simply use the model name as the value.


AttributeTypeRegExRequiredOneof GroupBuild-onlyDescription
[ANY]N/AN/AN/AN/AN/AThis type allows additional properties not governed by the schema. See the type description for details on these additional properties.
touchpad-wakeupstring^[01]$FalseFalseEnable (1) or disable (0) wake from touchpad.


AttributeTypeRegExRequiredOneof GroupBuild-onlyDescription
dptf-dvstringFalseFalseSystem image path to the .dv file containing DPTF (Dynamic Platform and Thermal Framework) settings.
filesarray - filesTrueTrue


AttributeTypeRegExRequiredOneof GroupBuild-onlyDescription
destinationstringFalseTrueInstallation path for the file on the system image.
sourcestringFalseTrueSource of the file relative to the build system.


AttributeTypeRegExRequiredOneof GroupBuild-onlyDescription
filesarray - filesFalseTrue
presentstringFalseFalseWhether touch is present or needs to be probed for.
probe-regexstringFalseFalseIf probe is set, the regex used to look for touch.


AttributeTypeRegExRequiredOneof GroupBuild-onlyDescription
destinationstringFalseTrueInstallation path for the file on the system image.
sourcestringFalseTrueSource of the file relative to the build system ${FILESDIR}
symlinkstringFalseTrueSymlink file that will be installed pointing to the destination.


AttributeTypeRegExRequiredOneof GroupBuild-onlyDescription
side-volume-buttonside-volume-buttonFalseFalseDefines the position of the side volume button. region indicates whether the button is at the side of the “screen” or “keyboard” of the device. side indicates which edge the button is anchored to while the device in landscape primary screen orientation. It can be “left”, “right”, “top”, “bottom”.


AttributeTypeRegExRequiredOneof GroupBuild-onlyDescription


AttributeTypeRegExRequiredOneof GroupBuild-onlyDescription

Usage Instructions

Adding and testing new properties

Before starting, cros_workon the following:

  • cros_workon --host start chromeos-config-host
  • cros_workon --board=BOARD start chromeos-config-bsp chromeos-config

To introduce a new property, first add its definition to the schema:

  • chromeos-config/cros_config_host/cros_config_schema.yaml

Then update the automatically via (unit tests will check this):

  • python -m cros_config_host.generate_schema_doc -o

To install the updated schema, run:

  • FEATURES=test sudo -E emerge chromeos-config-host

To use the new property, update your respective YAML source file. E.g. overlay-${BOARD}-private/chromeos-base/chromeos-config-bsp/files/model.yaml

To install the changes, run:

  • emerge-${BOARD} chromeos-config-bsp chromeos-config

At this point the updated config is located at:

  • /build/${BOARD}/usr/share/chromeos-config/yaml/config.yaml

To query your new item run the test command in the chroot:

  • cros_config_host -c /build/${BOARD}/usr/share/chromeos-config/yaml/config.yaml -m get </path/to/property>

For instance:

  • cros_config_host -c /build/coral/usr/share/chromeos-config/yaml/config.yaml -m robo360 get /firmware key-id
  • cros_config_host -c /build/coral/usr/share/chromeos-config/yaml/config.yaml get-models

Device Testing

To test configuration changes on actual devices use the platform.CrosConfig Tast test. This will run cros_config tests for unibuilds and mosys for all devices. See HOWTO.