Traditionally, Android* has been designed to have a unique lunch target for each enabled device, and each lunch target has a product source code directory associated with it. To enable Android on a variety of Intel x86- based boards across many CPU types at once, any given device needs to be tuned for specific peripherals and software features. With completely independent lunch targets and product directories, a great deal of configuration data was copied and pasted among build targets spread across many configuration file types. In addition, any changes to the configuration data must be propagated to those copies in the product directories, which significantly increases the maintenance cost. To mitigate the effort, Celadon introduces a multiple-inheritance system to generate product-definition features based on a mixin model.

Mixins are placed in groups; each group represents a functional area on the system, such as audio, Wi-Fi*, or boot parameters among other features and characteristics. Thus, configuration directives for functional areas are grouped together and can be reused. Each group provides radio- button-like selection options among features, and a product must choose at least one option for each group. A script device/intel/mixins/mixin-update then updates all the build targets with this data whenever it’s changed.


Mixin groups

Each mixin group represents a functional area of the system that has multiple radio button options from which to select for a particular product. Some groups may be simple true/false selections. A typical example is the option to integrate GMS. Many mixin groups offer a variety of selections, such as the cpu-arch mixin group, which instructs the system to gather configuration data relevant to the particular SoC and to generate the configuration for the target product.

Each mixin group has a subdirectory in the base mixin directory at device/intel/mixins/groups/. The path to the base mixin directory is specified in mixins.spec in each product directory:

$ ls device/intel/mixins/groups/
aaf                         boot-arch         debug-coredump      debug-usb-config    ethernet           gptbuild      memtrack           pstore            touch             vndk
abota-fw                    bugreport         debug-crashlogd     debugfs             evs                graphics      midi               public-libraries  treble            wlan
acpi-partition              camera-ext        debug-dvc_desc      default-drm         factory-partition  hdcpd         navigationbar      rfkill            trusty
acpio-partition             codec2            debug-kernel        device-specific     factory-scripts    health        net                sepolicy          usb
allow-missing-dependencies  codecs            debug-lmdump        device-type         filesystem_config  houdini       neuralnetworks     serialport        usb-audio-init
art-config                  config-partition  debug-log-watch     dexpreopt           firmware           intel_prop    odm-partition      slot-ab           usb-gadget
atrace                      cpu-arch          debug-npk           disk-bus            firststage-mount   kernel        ota-upgrade        storage           usb-init
audio                       cpuset            debug-phonedoctor   disk-encryption     flashfiles         lights        power              suspend           usb-otg-switch
avb                         dalvik-heap       debug-tools         display-density     fota               load_modules  product-partition  swap              variants
bluetooth                   dbc               debug-unresponsive  dynamic-partitions  googleservice      media         psdapp             thermal           vendor-partition


A mixin spec file is a text file that describes the product configurations. Every Celadon build target that uses mixins should have a mixins.spec file in their product board configuration directories. Instead of manually modifying feature settings in the product makefiles, the product customization and peripherals tuning are done by editing the mixins.spec file.

If there are updates or changes to any mixin configuration files, you should re-run the mixin-update script from the root of the Celadon Android source tree. The script searches all files named mixins.spec under the device/intel/ directory and generates the makefiles (e.g. AndroidBoard.mk, BoardConfig.mk, device.mk, init.rc, etc.) required for building Android in individual product directories.


The option.spec file, if it is present in an option subdirectory of a mixin group, specifies metadata for that option of a particular group. This file is used to set arguments to a default value if the value is not provided in mixins.spec. For example, a ‘efi’ option is available for the ‘boot-arch’ mixin group:

$ ls device/intel/mixins/groups/boot-arch/efi:
AndroidBoard.mk  fstab    init.rc           option.spec
BoardConfig.mk   gpt.ini  init.recovery.rc  product.mk

The configuration fragments such as AndroidBoard.mk and BoardConfig.mk included in the previous option directory are applied to the product configuration files if the option ‘efi’ is specified in the product mixin spec file mixins.spec:

boot-arch: efi(uefi_arch=x86_64,fastboot=efi,acpi_permissive=true)


The files.spec file is used to specify additional files that will be copied to device/intel/<lunch-target>/extra_files/<mixin-group>/ before building Celadon images. This configuration file should be placed in an option subdirectory of a group. The files listed in files.spec will be copied into the target product repo if this group is selected. For example, the mixins.spec of the CiV lunch target specifies the project-celadon option for the boot-arch group. As a result, the UEFI firmware startup file startup.nsh listed in files.spec is copied to the CiV source repository after running the device/intel/mixins/mixin-update script:

$ cat device/intel/project-celadon/caas/mixins.spec
boot-arch: project-celadon(uefi_arch=x86_64,fastboot=efi,ignore_rsci=true,disable_watchdog=true,...)

$ cat device/intel/mixins/groups/boot-arch/project-celadon/files.spec
update_ifwi_ab.sh: "ifwi update script running in postinstall"
startup.nsh: "Auto installer start"


The mixinfo.spec file is an optional file in a mixin group directory, which defines metadata for a particular group. It is currently used to manage dependencies between mixin groups. For example:

$ cat device/intel/mixins/groups/debug-phonedoctor/mixinfo.spec
deps = debug-crashlogd

Running a mixin update ensures the mixin group ‘debug-crashlogd’ is included before processing the ‘debug-phonedoctor’ group.