Specifically, I'm trying to build the sensors.hammerhead.so, which is under device/lge/hammerhead/libsensors/
I have the 4.4.2_r1 branch downloaded and compiled.
But this module is not being built (can't find it under out/target/product/hammerhead/system/lib/hw or system/vendor/lib/hw)
I tried using mmm device/lge/hammerhead/libsensors but I get:
make: Nothing to be done for `all_modules'.
Other modules such as lights.hammerhead.so (device/lge/hammerhead/liblight/) or sensors.default.so (hardware/akm/AKM8975_FS/libsensors/) work fine with mmm.
If you look in device/lge/hammerhead/libsensors/Android.mk you'll see that the entire contents of the file is excluded with a ifeq (0,1) conditional:
ifeq (0,1)
ifneq ($(TARGET_BUILD_PDK), true)
LOCAL_PATH := $(call my-dir)
...
endif
endif
Using git blame we can find that this conditional was added in commit 4e858dde. I have no idea why the module is disabled, but you can reenable it by reverting said commit (git revert 4e858dde). Whether this will result in something that actually works is another matter. You might find additional clues by walking through the history of the git. This particular sensor has gone through a long series for enable-disable-enable-disable commits.