Jollen's Presentation: Introducing Android low-level

Jollen’s Consulting

,
,

,
: www.jollen.org/consulting

Jollen’s Consulting
ta@jollen.org
[
]

Jollen’s Consulting Team

Presentation Training Coaching

Android Kernel

•Binder
•Ashmem (Android shared memory)
•PMEM (Processor memory allocator)
•logcat (Android Logger)
•wakelock (Android Power Management)
•Alarm

Key Features 2.6.23 2.6.25 2.6.27 2.6.29

1 Alarm Driver O O O O

2 Android Logger O O O O

3 Low Memory Killer O O O O

4 Power Management O O O O

5 USB Gadget O O O O

6 ASHMEM X O O O

7 PMEM X X O O

8 x86 Support X X O O

9 ./drivers/staging/Android/ X X X O

Android Toolchain

•android-toolchain-20081019
•http://android.git.kernel.org/pub/
•gcc 4.2.1 / binutils 2.17 / gdb 6.6
•ARMV5te+
•ABI: EABI, AAPCS
•--with-float=soft --with=fpu-vfp
•--enable-threads (single)

Application Developers

Applications change

Application Framework

Surface Manager Dalvik VM
System
Media Framework Shared Libraries
Image

Linux Kernel

Product Branch Maintainer

Applications


rebuild


Linux Kernel

Hardware Developing

Applications


change


Linux Kernel change

Architecture Porting

Applications



porting

Linux Kernel

• Application Developers
• Product Branch Maintainer

• Hardware Developing

• Hardware Developing
• Architecture Porting

• The best way to write good, efﬁcient code for
embedded systems is to understand what the
code you write really does. --Android Dev Guide

private SensorManager mSensorManager;

public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

mSensorManager = (SensorManager) getSystemService
(SENSOR_SERVICE);
}



(SENSOR_SERVICE);
}


(SENSOR_SERVICE);

}


UI;

SensorManager;
}


UI;

SensorManager;
}


SensorManager;

UI;
}

public class TunitBill extends Activity {
/** Called when the activity is first created. */
@Override

Debug.startMethodTracing("TunitB");

CharSequence time = Long.toString(SystemClock.elapsedRealtime());

Debug.stopMethodTracing();
}
}

public class TunitBill extends Activity {
@Override


CharSequence time = Long.toString(SystemClock.elapsedRealtime());

}
}

•
method-level

• TraceView method (method
tracing)

Avoid Creating Objects
Use Native Methods
Prefer Virtual Over Interface
Prefer Static Over Virtual
Avoid Internal Getters/Setters
Cache Field Lookups
Declare Constants Final
Use Enhanced For Loop Syntax With Caution
Avoid Enums
Use Package Scope with Inner Classes
Avoid Float

Avoid Creating Objects
Use Native Methods
Prefer Virtual Over Interface
Prefer Static Over Virtual
Avoid Internal Getters/Setters
Cache Field Lookups
Declare Constants Final
Use Enhanced For Loop Syntax With Caution
Avoid Enums
Use Package Scope with Inner Classes
Avoid Float

• Designing for Performance -- Android Dev
Guide

Android Tracing API
android.os.Debug


/* writing codes to profile */


Android Tracing API
android.os.Debug

public class TunitChris extends Activity {
@Override

Button button = (Button)findViewById(R.id.btn);

button.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// Perform action on click
}
});

}
}

Acitivty
View.OnClickListener

Android Copyright (c) 2009 Jollen’s Consulting . www.jollen.org/consulting

public class TunitChris extends Activity implements
View.OnClickListener {
@Override

Button button = (Button)findViewById(R.id.btn);
button.setOnClickListener(this);
}

Toast.makeText(
this,
"Yes.",
Toast.LENGTH_LONG).show();
}
}

button.setOnClickListener(new View.OnClickListener() {
// Perform action on click
}
});

public class TunitChris extends Activity implements
View.OnClickListener



(SENSOR_SERVICE);
}

SensorManager


}

public void onStop() {
super.onStop();

(SENSOR_SERVICE);
}


}

public void onStop() {
super.onStop();

(SENSOR_SERVICE);
}

better

Android Driver Model
HAL

native C programs

glibc & shared libs

S!"#$%!&'((

Kernel

Hardware

Android Framework

Application

JNI

S!"#$%!&'((
bionic & shared libs

Kernel

Hardware

public class Sensors extends Activity {
...
...
@Override
protected void onCreate(Bundle savedInstanceState) {
// Be sure to call the super class.

(SENSOR_SERVICE);
}
...
}

class SensorService extends ISensorService.Stub {
...
private static native int _sensors_control_init();
private static native ParcelFileDescriptor
_sensors_control_open();
private static native boolean
_sensors_control_activate(int sensor, boolean activate);
private static native int _sensors_control_set_delay
(int ms);
}

at framework/base/services/java/SensorService.java

...
public SensorService(Context context) {
if (localLOGV) Log.d(TAG, "SensorService
startup");
_sensors_control_init();
mNotificationManager = (NotificationManager)
context.getSystemService
(Context.NOTIFICATION_SERVICE);
mContext = context;
}
...
}


static JNINativeMethod gMethods[] = {
{"_sensors_control_init", "()I", (void*) android_init },
{"_sensors_control_open", "()Landroid/os/
ParcelFileDescriptor;",
(void*) android_open },
{"_sensors_control_activate", "(IZ)Z", (void*)
android_activate },
{"_sensors_control_wake", "()I", (void*)
android_data_wake },
{"_sensors_control_set_delay","(I)I", (void*)
android_set_delay },
};

static jint
android_init(JNIEnv *env, jclass clazz)
{
sensors_module_t* module;
if (hw_get_module(SENSORS_HARDWARE_MODULE_ID, (const hw_module_t**)
&module) == 0) {
if (sensors_control_open(&module->common, &sSensorDevice) == 0)
{
const struct sensor_t* list;
int count = module->get_sensors_list(module, &list);
return count;
}
}
return 0;
}

static inline int sensors_control_open(const struct hw_module_t*
module, struct sensors_control_device_t** device) {
return module->methods->open(module,
SENSORS_HARDWARE_CONTROL, (struct hw_device_t**)
device);
}

Application Context

getSystemService

Create Manager

App
App View

!"#$%& IStubService

Manager
framework/base/services/java

alvik VM IStubService

public Object getSystemService(String name) {
if (WINDOW_SERVICE.equals(name)) {
return WindowManagerImpl.getDefault();
} else if (LAYOUT_INFLATER_SERVICE.equals(name)) {
synchronized (mSync) {
LayoutInflater inflater = mLayoutInflater;
if (inflater != null) {
return inflater;
}
mLayoutInflater = inflater =
PolicyManager.makeNewLayoutInflater(getOuterContext());
return inflater;
}
} else if (ACTIVITY_SERVICE.equals(name)) {
return getActivityManager();
} else if (ALARM_SERVICE.equals(name)) {
return getAlarmManager();
..
} else if ( SENSOR_SERVICE.equals(name)) {
return getSensorManager();
}
...
}


private SensorManager getSensorManager() {
synchronized (mSync) {
if (mSensorManager == null) {
mSensorManager = new SensorManager
(mMainThread.getHandler().getLooper());
}
}
return mSensorManager;
}

Application Context

getSystemService

Create Manager

App
App View

!"#$%& IStubService

Manager

Dalvik VM IStubService

Service/Java

register
JNI Table
Android server

VM Onload App Onload


!"#$%&

Manager

Dalvik VM IStubService

Service/Java

register
JNI Table
Android server

Service/JNI
framework/base/services/jni

HAL
hardware/libhardware

HAL Stub

sysfs
/sys

VM Onload App Onload


...
public SensorService(Context context) {
if (localLOGV) Log.d(TAG, "SensorService
startup");
_sensors_control_init();
mNotificationManager = (NotificationManager)
context.getSystemService(Context.NOTIFICATION_SERVICE);
mContext = context;
}
...
}


VFS

Driver D
Driver B

Driver A
Driver E

Driver C

Copyright (c) 2009 Jollen’s Consulting, www.jollen.org/consulting Embedded Linux

kernel

buses devices classes firmware kobject

Core Driver Model – Subsystems (ksets…) /sys

Driver D
Driver B

Driver A
Driver E

Driver C

Copyright (c) 2009 Jollen’s Consulting, www.jollen.org/consulting Embedded Linux

Android

• Launcher Model
• getSystemService
• Framework
• HAL module sysfs

high-level

architect-level

low-level

<company_name>
<board_name>
+ Android.mk
+ product_config.mk
+ system.prop
products
+ AndroidProducts.mk
+ <first_product_name>.mk
+ <second_product_name>.mk

Android Jollen’s Consulting. www.jollen.org/consulting

1. Get Google Android
$ repo init -u git://android.git.kernel.org/platform/manifest.git -b cupcake
$ repo sync

2. Manifest ﬁle.
<manifest>
...
<project name="platform/vendor/asus/eee_701" path="vendor/asus/
eee_701"/>
...
</manifest>

3. Get EeePC platform.
$ repo sync

4. Build Android image.
$ TARGET_ARCH=x86 TARGET_PRODUCT=eee_701
DISABLE_DEXPREOPT=true make -j2 installer_img

5. Create USB boot stick.
Use make-live script. https://review.source.android.com/Gerrit#change,6475


Build EeePC 701 Product Tips # Google API issue

$(call inherit-product, $(SRC_TARGET_DIR)/product/generic.mk)

PRODUCT_NAME := eee_701
PRODUCT_DEVICE := eee_701
PRODUCT_POLICY := android.policy_mid
PRODUCT_PROPERTY_OVERRIDES +=
ro.com.android.dataroaming=true

Cupcake将Google APIs add-ons


Build EeePC 701 Product Tips # e2fsprogs issue

external/e2fsprogs/Android.mk:
--- a/Android.mk
+++ b/Android.mk
@@ -1,3 +1,3 @@
ifneq ($(TARGET_SIMULATOR),true)
-# include $(call all-subdir-makefiles)
+ include $(call all-subdir-makefiles)
endif


boot.img

installer.img

ramdisk.img

system.img

userdata.img


Android 随
$ make-live


AMD PCnet32 PCI support

VESA VGA graphics support

VGA 8x8 font

VGA 8x16 font


$ VBoxManage convertromraw -format VDI ./installer.img ./android.vdi


device/system/init

device/system/init/init.c

/etc/init.rc

动mount file system ( /etc/fstab)


/system/bin/logd
/sbin/adbd
/system/bin/usbd
/system/bin/debuggerd
/system/bin/rild
/system/bin/app_process
/system/bin/runtime
/system/bin/dbus-daemon
system_server


• Hardware Developingframework, app
LED : kernel, hal,

• Architecture Porting

www.jollen.org/consulting
Jollen@jollen.org

Jollen's Presentation: Introducing Android low-level

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