How to identify target_product in Android makefile

http://blog.csdn.net/stevenliyong/article/details/5285334

Today there is time to underestimate the Android makefile, and finally a little understanding of how the Android compiler system through the environment variable target_product to decide to compile custom PRODUCT.

First, compiling Android code is typically used:

# Make Showcommands

This is actually equivalent to the complete command below (see build/core/envsetup.mk for details)

# target_arch=arm Target_product=generic target_build_type=release make Showcommands

Visible, by default the compilation system considers target_product to be generic

So how do you compile a specific product for Android?

This requires a look at how Android makefile resolves environment variable target_product.

The reference relationship for Android Makefile is like this

Makefile, Build/core/main.mk, Build/core/config.mk, Build/core/envsetup.mk, build/core/product_ Config.mk

Compiling the system in BUILD/CORE/PRODUCT_CONFIG.MK first calls the function Get-all-product-makefiles defined in BUILD/CORE/PRODUCT.MK to

Traverse the entire vendor subdirectory, find vendor under all androidproducts.mk, different sub-directories androidproducts.mk defined different product_name, product_device and other information, (We can also export all product information when the console compiles by opening the #$ (dump-products) statement in build/core/product_config.mk), and then build/core/product_ CONFIG.MK calls Resolve-short-product-name to assign Product_device the Target_device defined in target_product matching androidproducts.mk.

With this target_device, and then back to Build/core/config.mk,

will include $ (target_devcie)/boardconfig.mk

BOARD_CONFIG_MK: =/
$ (Strip $ (wildcard/
$ (Src_target_dir)/board/$ (target_device)/boardconfig.mk/
vendor/*/$ (Target_device)/boardconfig.mk/
))

Include $ (BOARD_CONFIG_MK)

And this configuration file BOARDCONFIG.MK determines the target system compiler properties, such as using ALSA or not generic_audio, etc.

In addition here Target_device macro also decided Target_device_dir, because Target_device_dir take is the above mentioned boardconfig.mk path.

Target_device_dir: = $ (Patsubst%/,%,$ (DIR $ (BOARD_CONFIG_MK)))

Of course the Android OB target output is also determined by Target_device, see BUILD/CORE/ENVSETUP.MK

Target_out_root_release: = $ (Out_dir)/target
Target_out_root_debug: = $ (Debug_out_dir)/target
Target_out_root: = $ (target_out_root_$ (Target_build_type))

Target_product_out_root: = $ (target_out_root)/product

Product_out: = $ (target_product_out_root)/$ (Target_device)

Back to Build/core/main.mk, one of the things that the compilation system does next is to traverse through all the word directories, find all the android.mk files, and include these android.mk files in

#
# Typical build; Include any android.mk files we can find.
#

Subdir_makefiles: =/
$ (Shell build/tools/findleaves.py--prune=out--prune=.repo--prune=.git $ (subdirs) android.mk)

Include $ (subdir_makefiles)

We'll see it again.

./build/target/board/android.mk

, yes, it references the

Include $ (target_device_dir)/androidboard.mk

By the definition of the above target_device_dir, this goes again into the

Vendor the directory under Target_device, this MK file defines the specific product to compile and install the app and script.

How to identify target_product in Android makefile