Use the information in this page to create the Makefiles for your device and product. Please note, unlike the other pages in this section, the contents here are applicable only when creating an entirely new device type and are intended for company build and product teams only.

Understand 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, thus eliminating copying and simplifying maintenance.

Use Build Variants

When building for a particular product, it's often useful to have minor variations on what is ultimately 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, 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 is required by product configuration with PRODUCT_PACKAGES.

These are the currently-defined build variants:

Customize 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/config.xml.

To set up a resource overlay on this file, add the overlay directory to the project buildfile, as follows:

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.

Build a Product

There are many ways to organize the source files for your device. We'll briefly go over how the Nexus 6 implementation was organized as an example, but you can organize your source files and build the way you see fit.

Nexus 6 was implemented with a main device configuration named shamu. 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/moto/shamu directory to see how all of this is setup.

Write the Makefiles

The following steps describe how to set up product Makefiles in a way similar to that of the Nexus 6 product line:

1. Create a device/<company_name>/<device_name> directory for your product. For example, device/moto/shamu. 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/moto/shamu/device.mk.
3. Create a product definition Makefile to create a specific product based on the device. The following Makefile is taken from device/moto/shamu/aosp_shamu.mk as an example. Notice the product is inheriting from the device/moto/shamu/device.mk and vendor/moto/shamu/device-vendor.mk files via 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/aosp_base_telephony.mk)
   
   PRODUCT_NAME := aosp_shamu
   PRODUCT_DEVICE := shamu
   PRODUCT_BRAND := Android
   PRODUCT_MODEL := AOSP on Shamu
   PRODUCT_MANUFACTURER := motorola
   PRODUCT_RESTRICT_VENDOR_FILES := true
   
   $(call inherit-product, device/moto/shamu/device.mk)
   $(call inherit-product-if-exists, vendor/moto/shamu/device-vendor.mk)
   
   PRODUCT_NAME := aosp_shamu
   
   PRODUCT_PACKAGES += \
       Launcher3
   

   See Product Definition Variables for additional product-specific variables 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/moto/shamu/AndroidProducts.mk:

   #
   # This file should set PRODUCT_MAKEFILES to a list of product makefiles
   # to expose to the build system.  LOCAL_DIR will already be set to
   # the directory containing this file.
   #
   # This file may not rely on the value of any variable other than
   # LOCAL_DIR; do not use any conditionals, and do not look up the
   # value of any variable that isn't set in this file or in a file that
   # it includes.
   #
   
   PRODUCT_MAKEFILES := \
       $(LOCAL_DIR)/aosp_shamu.mk
   

5. Create a BoardConfig.mk Makefile that contains board-specific configurations. For an example, see device/moto/shamu/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.

Set Product Definition Variables

Product-specific variables are defined in the product's Makefile. Variables maintained in a product definition files include:

Set ANDROID_VENDOR_KEYS to connect over USB

The ANDROID_VENDOR_KEYS environment variable enables device manufacturers to access production builds over adb. Generate a key for each release that every device will accept, store those internally (such as at vendor/oem-name/security/adb/), and then use ANDROID_VENDOR_KEYS to tell adb to use these canonical keys rather than random keys.

Use the ANDROID_VENDOR_KEYS environment variable to point to the directory containing the generated adb public and private keys used for encryption. The private key is stored in file. The public key is stored in file.pub. The ANDROID_VENDOR_KEYS environment variable points to a file or directory where the generated key pairs are stored.

This variable is set to a file or directory that contains 2048-bit RSA authentication key pairs generated with the adb keygen file command. These key pairs are in addition to the RSA key pairs generated by the ADB server. An RSA key pair is needed when you use adb to connect over USB for the first time.

You must accept the host computer's RSA key to explicitly grant adb access to the device. By default key pairs generated by the ADB server are stored in the following key store directories as adbkey (private key) and adbkey.pub (public key):

For file locations, on MacOS, this will likely be: $HOME/.android. On Windows and Linux, this will be: %USERPOFILE%\.android. On Windows, RSA authentication keys can also be in C:\Windows\System32\config\systemprofile\.android in some cases. When the ADB server needs a key, it first searches the ADB server key store directory. If no keys are found, it then checks the ANDROID_VENDOR_KEYS environment variable. If no keys are found, the local ADB server generates and saves a new key pair in the ADB server key store directory.

Note: You can override the default directory where the ADB server stores RSA keys by setting the ANDROID_SDK_HOME environment variable. On the device, keys are stored in the /data/misc/adb/adb_keys/ file, and new authorized keys are appended to the same file as you accept them.