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Adding a New Device

Use the information in this page to create the makefiles for your device and product.

Each new Android module must have a configuration file to direct the build system with module metadata, compile-time dependencies, and packaging instructions. Android uses the Soong build system. See Building Android for more information about the Android build system.

Understanding build layers

The build hierarchy includes the abstraction layers that correspond to the physical makeup of a device. These layers are described in the table below. Each layer relates to the one above it in a one-to-many relationship. For example, an architecture can have more than one board and each board can have more than one product. You may define an element in a given layer as a specialization of an element in the same layer, which eliminates copying and simplifies maintenance.

Layer Example Description
Product myProduct, myProduct_eu, myProduct_eu_fr, j2, sdk The product layer defines the feature specification of a shipping product such as the modules to build, locales supported, and configuration for various locales. In other words, this is the name of the overall product. Product-specific variables are defined in product definition makefiles. A product can inherit from other product definitions, which simplifies maintenance. A common method is to create a base product that contains features that apply to all products, then create product variants based on that base product. For example, two products that differ only by their radios (CDMA versus GSM) can inherit from the same base product that doesn't define a radio.
Board/device marlin, blueline, coral The board/device layer represents the physical layer of plastic on the device (that is, the industrial design of the device). This layer also represents the bare schematics of a product. These include the peripherals on the board and their configuration. The names used are merely codes for different board/device configurations.
Arch arm, x86, arm64, x86_64 The architecture layer describes the processor configuration and application binary interface (ABI) running on the board.

Using build variants

When building for a particular product, it's useful to have minor variations on the final release build. In a module definition, the module can specify tags with LOCAL_MODULE_TAGS, which can be one or more values of optional (default), debug, and eng.

If a module doesn't specify a tag (by LOCAL_MODULE_TAGS), its tag defaults to optional. An optional module is installed only if it's required by the product configuration with PRODUCT_PACKAGES.

These are the currently defined build variants.

Variant Description
eng This is the default flavor.
  • Installs modules tagged with eng or debug.
  • Installs modules according to the product definition files, in addition to tagged modules.
  • ro.secure=0
  • ro.debuggable=1
  • ro.kernel.android.checkjni=1
  • adb is enabled by default.
user The variant intended to be the final release bits.
  • Installs modules tagged with user.
  • Installs modules according to the product definition files, in addition to tagged modules.
  • ro.secure=1
  • ro.debuggable=0
  • adb is disabled by default.
userdebug The same as user, with these exceptions:
  • Also installs modules tagged with debug.
  • ro.debuggable=1
  • adb is enabled by default.

Guidelines for userdebug

Running userdebug builds in testing helps device developers understand the performance and power of in-development releases. To maintain consistency between user and userdebug builds, and to achieve reliable metrics in builds used for debugging, device developers should follow these guidelines:

  • userdebug is defined as a user build with root access enabled, except:
    • userdebug-only apps that are run only on-demand by the user
    • Operations that run only during idle maintenance (on charger/fully charged), such as using dex2oatd versus dex2oat for background compiles
  • Don't include features that are enabled/disabled by default based on the build type. Developers are discouraged from using any form of logging that affects battery life, such as debug logging or heap dumping.
  • Any debugging features that are enabled by default in userdebug should be clearly defined and shared with all developers working on the project. You should enable debugging features only on a limited-time basis until the issue you're trying to debug is resolved.

Customizing the build with resource overlays

The Android build system uses resource overlays to customize a product at build time. Resource overlays specify resource files that are applied on top of the defaults. To use resource overlays, modify the project buildfile to set PRODUCT_PACKAGE_OVERLAYS to a path relative to your top-level directory. That path becomes a shadow root searched along with the current root when the build system searches for resources.

The most commonly customized settings are contained in the file frameworks/base/core/res/res/values/config.xml.

To set up a resource overlay on this file, add the overlay directory to the project buildfile using one of the following:

PRODUCT_PACKAGE_OVERLAYS := device/device-implementer/device-name/overlay

or

PRODUCT_PACKAGE_OVERLAYS := vendor/vendor-name/overlay

Then, add an overlay file to the directory, for example:

vendor/foobar/overlay/frameworks/base/core/res/res/config.xml

Any strings or string arrays found in the overlay config.xml file replace those found in the original file.

Building a product

You can organize the source files for your device in many different ways. Here's a brief description of one way to organize a Pixel implementation.

Pixel is implemented with a main device configuration named marlin. From this device configuration, a product is created with a product definition makefile that declares product-specific information about the device such as the name and model. You can view the device/google/marlin directory to see how all of this is set up.

Writing product makefiles

The following steps describe how to set up product makefiles in a way similar to that of the Pixel product line:

  1. Create a device/<company-name>/<device-name> directory for your product. For example, device/google/marlin. This directory will contain source code for your device along with the makefiles to build them.
  2. Create a device.mk makefile that declares the files and modules needed for the device. For an example, see device/google/marlin/device-marlin.mk.
  3. Create a product definition makefile to create a specific product based on the device. The following makefile is taken from device/google/marlin/aosp_marlin.mk as an example. Notice that the product inherits from the device/google/marlin/device-marlin.mk and vendor/google/marlin/device-vendor-marlin.mk files through the makefile while also declaring the product-specific information such as name, brand, and model.
    # Inherit from the common Open Source product configuration
    $(call inherit-product, $(SRC_TARGET_DIR)/product/core_64_bit.mk)
    $(call inherit-product, $(SRC_TARGET_DIR)/product/aosp_base_telephony.mk)
    
    PRODUCT_NAME := aosp_marlin
    PRODUCT_DEVICE := marlin
    PRODUCT_BRAND := Android
    PRODUCT_MODEL := AOSP on msm8996
    PRODUCT_MANUFACTURER := Google
    PRODUCT_RESTRICT_VENDOR_FILES := true
    
    PRODUCT_COPY_FILES += device/google/marlin/fstab.common:$(TARGET_COPY_OUT_VENDOR)/etc/fstab.marlin
    
    $(call inherit-product, device/google/marlin/device-marlin.mk)
    $(call inherit-product-if-exists, vendor/google_devices/marlin/device-vendor-marlin.mk)
    
    PRODUCT_PACKAGES += \
        Launcher3QuickStep \
        WallpaperPicker
    

    See Setting product definition variables for additional product-specific variables that you can add to your makefiles.

  4. Create an AndroidProducts.mk file that points to the product's makefiles. In this example, only the product definition makefile is needed. The example below is from device/google/marlin/AndroidProducts.mk (which contains both marlin, the Pixel, and sailfish, the Pixel XL, which shared most configuration):
    PRODUCT_MAKEFILES := \
    	$(LOCAL_DIR)/aosp_marlin.mk \
    	$(LOCAL_DIR)/aosp_sailfish.mk
    
    COMMON_LUNCH_CHOICES := \
    	aosp_marlin-userdebug \
    	aosp_sailfish-userdebug
    
  5. Create a BoardConfig.mk makefile that contains board-specific configurations. For an example, see device/google/marlin/BoardConfig.mk.
  6. Create a vendorsetup.sh file to add your product (a "lunch combo") to the build along with a build variant separated by a dash. For example:
    add_lunch_combo <product-name>-userdebug
    
  7. At this point, you can create more product variants based on the same device.

Setting product definition variables

Product-specific variables are defined in the product's makefile. The table shows some of the variables maintained in a product definition file.

Variable Description Example
PRODUCT_AAPT_CONFIG aapt configurations to use when creating packages.
PRODUCT_BRAND The brand (for example, carrier) the software is customized for, if any.
PRODUCT_CHARACTERISTICS aapt characteristics to allow adding variant-specific resources to a package. tablet, nosdcard
PRODUCT_COPY_FILES List of words like source_path:destination_path. The file at the source path should be copied to the destination path when building this product. The rules for the copy steps are defined in config/makefile.
PRODUCT_DEVICE Name of the industrial design. This is also the board name, and the build system uses it to locate BoardConfig.mk. tuna
PRODUCT_LOCALES A space-separated list of two-letter language code, two-letter country code pairs that describe several settings for the user, such as the UI language and time, date, and currency formatting. The first locale listed in PRODUCT_LOCALES is used as the product's default locale. en_GB, de_DE, es_ES, fr_CA
PRODUCT_MANUFACTURER Name of the manufacturer. acme
PRODUCT_MODEL End-user-visible name for the end product.
PRODUCT_NAME End-user-visible name for the overall product. Appears in the Settings > About screen.
PRODUCT_OTA_PUBLIC_KEYS List of over-the-air (OTA) public keys for the product.
PRODUCT_PACKAGES List of the APKs and modules to install. Calendar contacts
PRODUCT_PACKAGE_OVERLAYS Indicates whether to use default resources or add any product specific overlays. vendor/acme/overlay
PRODUCT_SYSTEM_PROPERTIES List of the system property assignments in the format "key=value" for the system partition. System properties for other partitions can be set via PRODUCT_<PARTITION>_PROPERTIES as in PRODUCT_VENDOR_PROPERTIES for the vendor partition. Supported partition names: SYSTEM, VENDOR, ODM, SYSTEM_EXT, and PRODUCT.

Setting ADB_VENDOR_KEYS to connect over USB

The ADB_VENDOR_KEYS environment variable enables device manufacturers to access debuggable builds (-userdebug and -eng, but not -user) over adb without manual authorization. Normally adb generates a unique RSA authentication key for each client computer, which it will send to any connected device. This is the RSA key shown in the adb authorization dialog. As an alternative you can build known keys into the system image and share them with the adb client. This is useful for OS development and especially for testing because it avoids the need to manually interact with the adb authorization dialog.

To create vendor keys, one person (usually a release manager) should:

  1. Generate a key pair using adb keygen. For Google devices, Google generates a new key pair for each new OS version.
  2. Check the key pairs in, somewhere in the source tree. Google stores them in vendor/google/security/adb/, for example.
  3. Set the build variable PRODUCT_ADB_KEYS to point to your key directory. Google does this by adding an Android.mk file in the key directory that says PRODUCT_ADB_KEYS := $(LOCAL_PATH)/$(PLATFORM_VERSION).adb_key.pub, which helps ensure that we remember to generate a new key pair for each OS version.

Here's the makefile Google uses in the directory where we store our checked-in key pairs for each release:

PRODUCT_ADB_KEYS := $(LOCAL_PATH)/$(PLATFORM_VERSION).adb_key.pub

ifeq ($(wildcard $(PRODUCT_ADB_KEYS)),)
  $(warning ========================)
  $(warning The adb key for this release)
  $(warning )
  $(warning   $(PRODUCT_ADB_KEYS))
  $(warning )
  $(warning does not exist. Most likely PLATFORM_VERSION in build/core/version_defaults.mk)
  $(warning has changed and a new adb key needs to be generated.)
  $(warning )
  $(warning Please run the following commands to create a new key:)
  $(warning )
  $(warning   make -j8 adb)
  $(warning   LOGNAME=android-eng HOSTNAME=google.com adb keygen $(patsubst %.pub,%,$(PRODUCT_ADB_KEYS)))
  $(warning )
  $(warning and upload/review/submit the changes)
  $(warning ========================)
  $(error done)
endif

To use these vendor keys, an engineer only needs to set the ADB_VENDOR_KEYS environment variable to point to the directory in which the key pairs are stored. This tells adb to try these canonical keys first, before falling back to the generated host key that requires manual authorization. When adb can't connect to an unauthorized device, the error message will suggest that you set ADB_VENDOR_KEYS if it's not already set.