What's new internally in Marshmallow ?

The following lists some of the key code/features changes inside Marshmallow. This is based on full AOSP code comparison between android-5.1.1_r18 and android-6.0.0_r1. This list is just a mean to start off to know the difference between the version of Android platform.

* /developers

	- build/prebuilts/androidtv/sample-inputs
	- build/prebuilts/gradle
	- samples/android/common
		* contain example for MIDI
	- samples/android/admin
		* contain example for device owner and NFC
	- samples/android/connectivity	
		* contain interesting example for bluetooth advertisement, wifi-direct and networking
	- samples/android/content
		* contain interesting example for backup and directshare
	- samples/android/media
		* contain example for Camera and MIDI
	- samples/android/notification
		* contain example for active notification
	- samples/android/security
		* fingerprint and device security

/development
	- samples/ReceiveShareDemo
/external
	- androidplot
		* contain sample plotting app
/frameworks
	- data-binding 
		* new feature
	- base/cmds/hid
		* USB based hid tool ?
	- base/cmds/sm
		* related to mount and disk	
	- base/cmds/telecom 
		* telecom related too ?
	* base/packages/StatementService -- new app that allow to check an apk from a website (used also inside PackageManagerService)
	* base/packages/SystemUI 
		* new Assist functionality added
		* tuner view
	* base/media
		* MIDI server and service
		* /packages -- Bluetooth MIDI service
	* base/wifi	
		* WiFi passpoint implementation (http://www.wi-fi.org/discover-wi-fi/wi-fi-certified-passpoint)
		* frequency are split into it's own 
				   /**
				    * AP Channel bandwidth is 20 MHZ
				    */
				    public static final int CHANNEL_WIDTH_20MHZ = 0;
				   /**
				    * AP Channel bandwidth is 40 MHZ
				    */
				    public static final int CHANNEL_WIDTH_40MHZ = 1;
				   /**
				    * AP Channel bandwidth is 80 MHZ
				    */
				    public static final int CHANNEL_WIDTH_80MHZ = 2;
				   /**
				    * AP Channel bandwidth is 160 MHZ
				    */
				    public static final int CHANNEL_WIDTH_160MHZ = 3;
				   /**
				    * AP Channel bandwidth is 160 MHZ, but 80MHZ + 80MHZ
				    */
				    public static final int CHANNEL_WIDTH_80MHZ_PLUS_MHZ = 4;
	* base/tools
		* aapt2 available
	* base/telephony
		* carrier configuration manager
		* modem activity information available
		* voicemail has got it's own class, does this mean we can save voicemail in a contentprovider ?
		* lots of changes to video calling capability
	* base/services
		* voice assistant has got it's own service
		* USB has few new manager classes - MIDI, ALSA Audio, USB Port (control the properties of physical USB ports via the "/sys/class/dual_role_usb") interface. 			  At the moment USB C provide the capability to switch between USB charging and data direction. For non USB C the kernel driver must be modified or changed
		* alarm is now also using /sys/class/rtc
		* Fingerprint and Midi native service implementation
		* GPS has batching data
		* GNSS capability is provided for GPS (if feature available)
		* detecting any kind of motion movement class provided (AnyMotionDetector)
		* Token based (time expired) authentication provided
		* debugging flag configuration for ActivityManagerService has been moved to a separate class
		* new class to track the amount of time a user spent on an app (AppTimeTracker)
		* volume service as the volume UI changed in M
		* network diagnostic class provided to enable network checking (at the moment used in the dump() method)
		* substantial changes on the notification framework	
		* DefaultPermissionGrantPolicy.java contain the default permission for the system
		* PackageDexOptimizer - Helper class for running dexopt command on packages.
		* timezone can be updated automatically
		* GraphicsStatsService useful for stats graphics ashmem
/hardware
	* new .so FM library from Mediatek
	* libbt-vendor.so source for Marvell Bluetooth
	* usbcamera HAL is provided (created under camera.usb.default.so) all we need to do is enable Camera drivers in Kernel
	* radio HAL (created under radio.fm.default.so) is provided
	* interesting input subsystem (created under input.evdev.default.so) --> not very sure what this is for but seems like USB related input
	* Intel provide hwcompose for merrifield and moorefield. There is a simple example of how to use hwcompose intel/img/hwcomposer/merrifield/test/nv12_ved_test.cpp

/libcore
	* tzdata for time zone manipulation
	* inside support/ folder there is a test for testing TLS
	* Netlink socket communication possible internally via Java layer	

/ndk
	* docs/ directory contain a comprehensive NDK development guide

/packages
	* CarrierConfig app to configure carrier configuration (NEW !)
	* ExactCalculator
	* lots of small changes here and there for the different built-in app
	* Mms has been renamed to Messaging 
	* experimental/ contains few sample app - permission and printing
	* providers - provide new provider ==> BookmarkProvider and CallLogProvider
	* Telecomm app inside services/ now has a test app that is very useful for testing purpose

/system
	* bt/ bluedroid implementation
	* base/ libbase
	* fingerprintd/ daemon for fingerprint
	* gatekeeperd/ daemon for gatekeeper
	* new init commands
		- writepid <file...>
		- bootchart_init
		- class_reset <serviceclass>
		- copy <src> <dst>
		- load_all_props
		- load_persist_props
		- loglevel <level>
		- mount_all <fstab>
		- powerctl
		- restart <service>
		- rmdir <path>
		- rm <path>	
		- swapon_all <fstab>
		- verity_load_state
		- verity_update_state <mount_point>

		 
			For quicker turnaround when working on init itself, use:

			  mm -j
			  m ramdisk-nodeps
			  m bootimage-nodeps
			  adb reboot bootloader
			  fastboot boot $ANDROID_PRODUCT_OUT/boot.img

			Alternatively, use the emulator:

			  emulator -partition-size 1024 -verbose -show-kernel -no-window

			You might want to call klog_set_level(6) after the klog_init() call
			so you see the kernel logging in dmesg (or the emulator output).	
	* extras/
		- slideshow app used in verity 
			on verity-logging
			    exec u:r:slideshow:s0 -- /sbin/slideshow warning/verity_red_1 warning/verity_red_2
		- perfprofd - collects system-wide profiles 
	* gatekeeper/
	* vold/ a number of new class and modification for external storage and security	

***********
Tech Notes
***********
- /storage/emulated/legacy has been removed completely
- Nice to see drm_gralloc, drm_hwcompose, libdrm included (inside external/)
- Interesing google-breakpad
- Jetty is included the question is why ?
- mockftpserver ? ftp server what for ?
- v8 JS engine is included
- IpReachabilityMonitor.java is an interesting class as it allows app to be notified when an IP connection is lost
- android/os/storage has new API to detect new storage device that has come online
- IDeviceIdleController interesting interface. The implementation is inside DeviceIdleController.java
- BatteryManager.java added new state 
	    public static final String ACTION_CHARGING = "android.os.action.CHARGING";
	    public static final String ACTION_DISCHARGING = "android.os.action.DISCHARGING";
- new method to create a unique filename is provided inside android/os/FileUtils
- Interesting new feature inside android/os/INetworkManagementService
	    /**
	     * Enables unidirectional packet forwarding from {@code fromIface} to
	     * {@code toIface}.
	     */
	    void startInterfaceForwarding(String fromIface, String toIface);

	    /**
	     * Disables unidirectional packet forwarding from {@code fromIface} to
	     * {@code toIface}.
	     */
	    void stopInterfaceForwarding(String fromIface, String toIface);
- new feature inside android/os/IPowerManager.aidl
    * boolean isDeviceIdleMode();
    * boolean isScreenBrightnessBoosted();
- new feature inside android/os/IProcessInfoService.aidl
    void getProcessStatesFromPids(in int[] pids, out int[] states);
- android/os/MessageQueue.java
	provide new API that allows to tap into the queuing to know whether it is idle and also parcel event handler
- android/os/PowerManagerInternal.java
	    public abstract void setDeviceIdleMode(boolean enabled);
	    public abstract void setDeviceIdleWhitelist(int[] appids);
	    public abstract void setDeviceIdleTempWhitelist(int[] appids);
	    public abstract void updateUidProcState(int uid, int procState);
	    public abstract void uidGone(int uid);
- new zygote parameter
		--mount-external-write
		--mount-external-read
		--mount-external-default
		--generate-debug-info
		--enable-jit
- interesting new feature inside android/os/StrictMode.java (strict mode inside Settings)
		- detectCleartextNetwork()
		- penaltyDeathOnCleartextNetwork()  --> VERY interesting (Crashes the whole process when cleartext network traffic is detected)
- plenty of changes inside android/os/storage/StorageManager because of the addition of adding external storage feature
- new intent inside android/provider/AlarmClock
		- ACTION_DISMISS_ALARM
		- ACTION_SNOOZE_ALARM
		- EXTRA_ALARM_SEARCH_MODE	
- new security keymaster API inside android/security/keymaster
- new deep linking inside android/service/chooser
- new interface for communication with GateKeeper android/service/gatekeeper
- new camera API service/media/CameraPrewarmService
- interesting notification API android/service/notification/ZenModeConfig
- hypenation word UI android/text/Hyphenator
- cool class 
	* android/util/KeyValueListParser.java

- new display density for different kind of display android/util/DisplayMetrics - DENSITY_360 , DENSITY_420
- new animation class android/view/animation/ClipRectLRAnimation, android/view/animation/ClipRectTBAnimation, android/view/animation/TranslateXAnimation,  android/view/animation/TranslateYAnimation
- android/view/IWindowManager
	* requestAssistScreenshot
- different key events for different function android/view/KeyEvent.java
     /** Key code constant: Navigate to previous key.
     * Goes backward by one item in an ordered collection of items. */
    public static final int KEYCODE_NAVIGATE_PREVIOUS = 260;
    /** Key code constant: Navigate to next key.
     * Advances to the next item in an ordered collection of items. */
    public static final int KEYCODE_NAVIGATE_NEXT   = 261;
    /** Key code constant: Navigate in key.
     * Activates the item that currently has focus or expands to the next level of a navigation
     * hierarchy. */
    public static final int KEYCODE_NAVIGATE_IN     = 262;
    /** Key code constant: Navigate out key.
     * Backs out one level of a navigation hierarchy or collapses the item that currently has
     * focus. */
    public static final int KEYCODE_NAVIGATE_OUT    = 263;
    /** Key code constant: Skip forward media key. */
    public static final int KEYCODE_MEDIA_SKIP_FORWARD = 272;
    /** Key code constant: Skip backward media key. */
    public static final int KEYCODE_MEDIA_SKIP_BACKWARD = 273;
    /** Key code constant: Step forward media key.
     * Steps media forward, one frame at a time. */
    public static final int KEYCODE_MEDIA_STEP_FORWARD = 274;
    /** Key code constant: Step backward media key.
     * Steps media backward, one frame at a time. */
    public static final int KEYCODE_MEDIA_STEP_BACKWARD = 275;
- android/view/SearchEvent
- ALSA specific helper file com/android/internal/alsa
- com/android/internal/app/AssistUtils - interesting to investigate more about this
- com/android/internal/app/DumpHeapActivity - This activity is displayed when the system has collected a heap dump from a large process and the user has selected to share it.
- new packages
	* com/android/internal/logging 
	* com/android/internal/midi