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 chromium.org once the feature is complete and launched.

Important classes

See CrosConfig for the class to use to access configuration strings on a target. See cros_config_host.py 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.

Debugging

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:

   config:
     $some-local-variable: "some-value"
     some-element: "{{$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.

   imports:
     - "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}}"
  identity:
    platform-name: "SomePlatform"
    smbios-name-match: "SomePlatform"
    sku-id: "{{$sku-id}}"
  firmware-signing:
    key-id: "{{$key-id}}"
    signature-id: "{{name}}"
chromeos:
  devices:
    - $device-name: "SomeDevice"
      products:
        - $brand-code: "YYYY"
          $key-id: "SOME-KEY-ID"
      skus:
        - $sku-id: 0
          config:
            <<: *common_config
            wallpaper: "some-wallpaper"
        - $sku-id: 1
          config: *common_config

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

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

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.

Schema Validation

The config is evaluated against a http://json-schema.org/ 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 README.md file) via: python -m cros_config_host.generate_schema_doc -o README.md

The schema definition is below:

CrOS Config Type Definitions (v2)

model

arc

build-properties

files

audio

main

files

firmware

build-targets

firmware-signing

identity

power

thermal

files

touch

files

ui

power-button

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 README.md automatically via (unit tests will check this):

• python -m cros_config_host.generate_schema_doc -o README.md

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 Tree - Schema (v1)

The 2017 unibuild devices were launched under version 1 for chromeos-config. For these cases, the v1 schema (below) is still used; however, all new devices should be using the v2 schema (YAML based).

We plan to migrate all overlays to v2 as soon as possible. Please do not create any new device tree based configs or update the device tree implementation with features for overlays that have already been migrated.

• family: Provides family-level configuration settings, which apply to all models in the family.

  • audio (optional): Contains information about audio devices used by this family. Each subnode is defined as a phandle that can be referenced from the model-specific configuration using the audio-type property.

    • <audio-type>: Node containing the audio config for one device type. All filenames referenced are in relation to the ${FILERDIR} directory of the ebuild containing them.
      • cras-config-dir: Directory to pass to cras for the location of its config files
      • ucm-suffix: Internal UCM suffix to pass to cras
      • topology-name (optional): Name of the topology firmware to use
      • card: Name of the audio ‘card’
      • volume: Template filename of volume curve file
      • dsp-ini: Template filename of dsp.ini file
      • hifi-conf: Template filename of the HiFi.conf file
      • alsa-conf: Template filename of the card configuration file
      • topology-bin (optional): Template filename of the topology firmware file Template filenames may include the following fields, enclosed in {...} defined by the audio node: card, cras-config-dir, topology-name, ucm-suffix as well as model for the model name. The expansion / interpretation happens in cros_config_host. Other users should not attempt to implement this. The purpose is to avoid having to repeat the filename in each model that uses a particular manufacturer's card, since the naming convention is typically consistent for that manufacturer.

  • arc (optional): Contains information for the Android container used by this family.

    • build-properties (optional): Contains information that will be set into the Android property system inside the container. Each subnode is defined as a phandle that can be referenced from the model-specific configuration using the arc-properties-type property. The information here is not to be used for Chrome OS itself. It is purely for the container environment.

      The Android build fingerprint is generated from these properties. Currently the fingerprint is:

      google/{product}/{device}:{version_rel}/{id}/{version_inc}:{type}/{tags}

      Of these, the first three fields come from the properties here. The rest are defined by the build system.

      • <arc-properties-type>: Node containing the base cheets configuration for use by models.
        • product: Product name to report in ro.product.name. This may be the model name, or it can be something else, to allow several models to be grouped into one product.
        • device: Device name to report in ro.product.device. This is often {product}_cheets but it can be something else if desired.
        • oem: Original Equipment Manufacturer for this model. This generally means the OEM name printed on the device.
        • marketing-name: Name of this model as it is called in the market, reported in ro.product.model. This often starts with {oem}.
        • metrics-tag: Tag to use to track metrics for this model. The tag can be shared across many models 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.
        • first-api-level: The first Android API level that this model shipped with.

  • power (optional): Contains information about power devices used by this family. Each subnode is defined as a phandle that can be referenced from the model-specific configuration using the power-type property.

    • <power-type>: Node containing the power config for one device type. Each property corresponds to a power_manager preference, more completely documented in power_manager.
      • charging-ports: String describing charging port positions.
      • keyboard-backlight-no-als-brightness: Initial brightness for the keyboard backlight for systems without ambient light sensors, in the range [0.0, 100.0].
      • low-battery-shutdown-percent: Battery percentage threshold at which the system should shut down automatically, in the range [0.0, 100.0].
      • power-supply-full-factor: Fraction of the battery's total charge at which it should be reported as full in the UI, in the range (0.0, 1.0].
      • set-wifi-transmit-power-for-tablet-mode: If true (1), update wifi transmit power when in tablet vs. clamshell mode.
      • suspend-to-idle: If true (1), suspend to idle by writing freeze to /sys/power/state.

  • bcs (optional): Provides a set of BCS (Binary Cloud Storage) sources which can be used to download files needed by the build system. Each subnode is defined as a phandle that can be referenced from a node which needs access to BCS.

    • <bcs-type>: Node containing information about one BCS tarfile:
      • overlay: Name of overlay to download from
      • package: Package subdirectory to download from
      • ebuild-version: Tarfile version to download. This corresponds to the ebuild version prior to unibuild, but can be any suitable string.
      • tarball: Template for tarball to download. This can include {package} and {version}.

  • firmware (optional) : Contains information about firmware versions and files

    • script: Updater script to use. See the pack_dist directory for the scripts. The options are:
      • updater1s.sh: Only used by mario. Do not use for new boards.
      • updater2.sh: Only used by x86-alex and x86-zgb. Do not use for new boards.
      • updater3.sh: Used for various devices shipped around 2012.
      • updater4.sh: In current use. Supports software sync for the EC.
      • updater5.sh: In current use. Supports firmware v4 (chromeos-ec, vboot2)
    • shared: Contains information intended to be shared across all models (see firmware discussion under models below)
      • bcs-overlay: Overlay name containing the firmware binaries. This is used to generate the full path. For example a value of overlay-reef-private in the reef model means that all files will be of the form gs://chromeos-binaries/HOME/bcs-reef-private/overlay-reef-private/chromeos-base/chromeos-firmware-reef/<filename>.
      • build-targets: Sub-nodes of this define the name of the build artifact produced by a particular software project in the Portage tree.
        • coreboot: Defines the Kconfig/target used for coreboot and chromeos-bootimage ebuilds.
        • ec: Defines the “board” used to generate the ec firmware blob within the chromeos-ec ebuild.
        • depthcharge: Defines the model target passed to the compile phase within the depthcharge ebuild.
        • libpayload: Not currently used as the libpayload ebuild is not yet unibuild-aware.
        • cr50 (optional): Defines the model target to build cr50, if this is used on the platform. This is actually a build target for the EC but is specified separately to make it clear that it is a build for a separate device.
      • main-image: Main image location. This must start with bcs:// . It refers to a file available in BCS. The file will be unpacked to produce a firmware binary image.
      • main-rw-image (optional): Main RW (Read/Write) image location. This must start with bcs://. It refers to a file available in BCS. The file will be unpacked to produce a firmware binary image.
      • ec-image (optional): EC (Embedded Controller) image location. This must start with bcs:// . It refers to a file available in BCS. The file will be unpacked to produce a firmware binary image.
      • pd-image (optional): PD (Power Delivery controller) image location. This must start with bcs:// . It refers to a file available in BCS. The file will be unpacked to produce a firmware binary image.
      • stable-main-version (optional): Version of the stable firmware. On dogfood devices where RO firmware can be updated, we perform a full firmware update if the existing firmware on the device is older than this version. Deprecation in progress. See crbug.com/70541.
      • stable-ec-version (optional): Version of the stable EC firmware. On dogfood devices where RO EC firmware can be updated, we perform a full firmware update if the existing EC firmware on the device is older than this version. Deprecation in progress. See crbug.com/70541.
      • stable-pd-version (optional): Version of the stable PD firmware. On dogfood devices where RO PD firmware can be updated, we perform a full firmware update if the existing PD firmware on the device is older than this version. Deprecation in progress. See crbug.com/70541.
      • extra (optional): A list of extra files or directories needed to update firmware, each being a string filename. Any filename is supported. If it starts with bcs:// then it is read from BCS as with main-image above. But normally it is a path. A typical example is ${FILESDIR}/extra which means that the extra diectory is copied from the firmware ebuild's files/extra directory. Full paths can be provided, e.g. ${SYSROOT}/usr/bin/ectool. If a directory is provided, its contents are copied (subdirectories are not supported). This mirrors the functionality of CROS_FIRMWARE_EXTRA_LIST. But note that multiple files or directories should use a normal device-tree list format, not be separated by semicolon.
      • tools (optional): A list of additional tools which should be packed into the firmware update shellball. This is only needed if this model needs to run a special tool to do the firmware update.
      • create-bios-rw-image (optional): If present this indicates that we should re-sign and generate a read-write firmware image. This replaces the CROS_FIRMWARE_BUILD_MAIN_RW_IMAGE ebuild variable.
      • no-firmware (optional): If 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.

  • mapping: (optional): Used to determine the model/sub-model for a particular device. There can be any number of mappings. At present only a sku-map is allowed.

    • sku-map: Provides a mapping from SKU ID to model/sub-model. One of simple-sku-map or single-sku must be provided. smbios-name-match is needed only if the family supports models which have SKU ID conflicts and needs the SMBIOS name to disambiguate them. This is common when migrating legacy boards to unified builds, but may also occur if the SKU ID mapping is not used for some reason.
      • platform-name: Indicates the platform name for this platform. This is reported by ‘mosys platform name’. It is typically the family name with the first letter capitalized.
      • smbios-name-match (optional) Indicates the smbios name that this table mapping relates to. This map will be ignored on models which don't have a matching smbios name.
      • simple-sku-map (optional): Provides a simple mapping from SKU (an integer value) to model / sub-model. Each entry consists of a sku value (typically 0-255) and a phandle pointing to the model or sub-model.
      • single-sku (optional): Used in cases where only a single model is supported by this mapping. In other words, if the SMBIOS name matches, this is the model to use. The value is a phandle pointing to the model (it cannot point to a sub-model).

  • touch (optional): Contains information about touch devices used by this family. Each node is defined as a Phandle that can be referenced from the model-specific configuration using the touch-type property.

    • vendor: Name of vendor.
    • firmware-bin: Template filename to use for vendor firmware binary. The file is installed into /opt/google/touch.
    • firmware-symlink: Template filename to use for the /lib/firmware symlink to the firmware file in /opt/google/touch. The /lib/firmware part is assumed.
    • bcs-type (optional): phandle pointing to the BCS node to use to obtain a tarfile containing the firmware.

    Template filenames may include the following fields, enclosed in {...} defined by the touch node: vendor, pid, version as well as model for the model name. The expansion / interpretation happens in cros_config. Other users should not attempt to implement this. The purpose is to avoid having to repeat the filename in each model that uses a particular manufacturer's touchscreen, since the naming convention is typically consistent for that manufacturer.

• models: Sub-nodes of this define models supported by this board.

  • <model name>: actual name of the model being defined, e.g. reef or pyro

    • arc (optional): Contains arc++ configuration information

      • hw-features: Script filename that configures the Arc++ hardware features (by probing or hard-coding) for a model.
      • build-properties (optional): Contains information for the Android container system properties used by this model. Properties here are the same as in the family node above, with one addition to provide common values:
        • arc-properties-type: Phandle pointing to a subnode of the family arc build-properties configuration.

    • audio (optional): Contains information about audio devices used by this model.

      • <audio_system>: Contains information about a particular audio device used by this model. Valid values for the package name are:

        • main: The main audio system

        For each of these:

        • audio-type: Phandle pointing to a subnode of the family audio configuration.

        All properties defined by the family subnode can be used here. Typically it is enough to define only cras-config-dir, ucm-suffix and topology-name. The rest are generally defined in terms of these, within the family configuration nodes.

    • brand-code: (optional): Brand code of the model (also called RLZ code). See list and one-pager.

    • default (optional): Indicates that all of the nodes and properties of this model should default to the same as another model. The value is a phandle pointing to the model. It is not possible to ‘remove’ nodes / properties defined by the other model. It is only possible to change properties or add new ones. Note: This is an experimental feature which will be evaluated in December 2017 to determine its usefulness versus the potential confusion it can cause.

    • thermal(optional): Contains information about thermal properties and settings.

      • dptf-dv: Filename of the .dv file containing DPTF (Dynamic Platform and Thermal Framework) settings, relative to the ebuild's FILESDIR.

    • touch (optional): Contains information about touch devices such as touchscreens, touchpads, stylus.

      • present (optional): Indicates whether this model has a touchscreen. This is used by the ARC++ system to pass information to Android, for example. Valid values are:

        • no: This model does not have a touchscreen (default)
        • yes: This model has a touchscreen
        • probe: This model might have a touchscreen but we need to probe at run-time to find out. This should ideally only be needed on legacy devices which were not shipped with unibuild.

      • probe-regex (optional): Indicates the regular expression that should be used to match again device names in sys/class/input/input*/name. If the expression matches any device then the touchscreen is assumed to exist.

      • <device_type> (optional): Contains information about touch firmware packages. Valid values for package_name are:

        • stylus - a pen-like device with a sensor on or behind the display which together provide absolute positions with respect to the display
        • touchpad - a touch surface separate from the display
        • touchscreen - a transparent touch surface on a display which provides absolute positions with respect to the display

        You can use unit values (touchscreen@0, touchscreen@1) to allow multiple devices of the same type on a model.

        For each of these:

        • touch-type: Phandle pointing to the touch node in the Family configuration. This allows the vendor name and default firmware file template to be defined.
        • pid: Product ID string, as defined by the vendor.
        • version: Version string, as defined by the vendor.
        • firmware-bin (optional): Filename of firmware file. See the Family touch node above for the format. If not specified then the firmware-bin property from touch-type is used.
        • firmware-symlink: Filename of firmware file within /lib/firmware on the device. See the Family touch node above for the format.

    • wallpaper (optional): base filename of the default wallpaper to show on this device. The base filename points session_manager to two files in the /usr/share/chromeos-assets/wallpaper/<wallpaper> directory: /[filename]_[small|large].jpg. If these files are missing or the property does not exist, “default” is used.

    • whitelabel (optional): Sometimes models are so similar that we do not want to have separate settings. This happens in particular with ‘white-label’ devices, where the same device is shipped by several OEMs under difference brands. This is a phandle pointing to another model whose configuration is shared. All settings (except for a very few exceptions) will then come from the shares node. Currently if this properly is used, then only the firmware { key-id }, brand-code and wallpaper propertles can be provided. All other properties will come from the shared model.

    • firmware (optional) : Contains information about firmware versions and files. The properties and nodes inside this node are exactly the same as family/firmware/shared. By convention, tools looking for firmware properties for a model will fallback to the family-level firmware/shared configuration if the node or property is not found at the model level.

      • shares(optional): Phandle pointing to the firmware to use for this model. This is a list with a single phandle, pointing to the firmware node of another model. The presence of this property indicates that this model does not have separate firmware although it may have its own keyset. This property is used to share firmware across multiple models where hardware differences are small and we can detect the model from board ID pins. At this time, only a phandle reference to a subnode of family/firmware is supported. There are no restrictions on the phandle target node naming. Note that this property cannot be provided if the model configuration is shared at the model level (the whitelabel property under <model_name>).
      • key-id (optional): Unique ID that matches which key will be used in for firmware signing as part of vboot. For context, see go/cros-unibuild-signing
      • sig-id-in-customization-id (optional): Indicates 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.

    • powerd-prefs (optional): Name of a subdirectory under the powerd model_specific prefs directory where model-specific prefs files are stored.

    • test-label (optional): Test label applied to DUTs in the lab. In Autotest, this will be the model label. By allowing an alternate label, different models can be shared for testing purposes.

    • ui (optional): Config related to operation of the UI on this model.

      • power-button (optional): Defines the position on the screen where the power-button menu appears after a long press of the power button on a tablet device. The position is defined according to the ‘landscape-primary’ orientation, so that if the device is rotated, the button position on the screen will follow the rotation.

        • edge: Indicates which edge the power button is anchored to. Can be “left”, “right”, “top”, “bottom”. For example, “left” means that the menu will appear on the left side of the screen, with the distance along that edge (top to bottom) defined by the next property.
        • `position': Indicates the position of the menu along that edge, as a fraction, measured from the top or left of the screen. For example, “0.3” means that the menu will be 30% of the way from the origin (which is the left or top of the screen).

    • oem-id (optional): Some 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 models.