Presentation for Android Australia Sydney group on 22/August/2013 at fishburners.org

1. Learning AOSP
Android Linux Device Drivers
22nd
August 2013
August 2013
@nanikjava
ozandroid.info
bit.ly/12r7yOr

2. ANDROID & LINUX

3. ANDROID LINUX DRIVERS
 Android core low level
 Software & Hardware drivers (mostly
software)
 Minimum tasks performed
 Access via framework layer or library

4. MAINLINE VS VENDOR LINUX

v3.3 driver merge (excl wakelock)

v3.5 wakelock merge

Patch prior to v3.5 (different directory)

Vendor “normally” releases Linux kernel

5. ANDROID DRIVERS

ashmem (mm/ashmem.c)

binder (drivers/staging/android/binder.c)

lowmemorykiller (drivers/staging/android/lowmemorykiller.c)

ram_console (drivers/staging/android/ram_console.c)

timed_gpio (drivers/staging/android/timed_gpio.c)

usb – otg, adb, gadget, accessories, etc (drivers/usb/gadget)

logger (drivers/staging/android/logger.c)

alarm (drivers/staging/android/alarm.c)

wakelock (kernel/power/wakelock.c)

6. LAYERS INTERACTION

7. BINDER

Kernel

drivers/staging/binder.c

Framework

frameworks/base/core/java/android/os/Binder.java

frameworks/base/core/jni/android_util_Binder.java

frameworks/native/cmds/servicemanager/binder.c

frameworks/native/cmds/servicemanager/service_manager.c

Virtual Filesystem

/sys/kernel/debug/binder → debugging

/dev/binder → used internally by framework

8. 
Kernel

drivers/staging/android/logger.c

Framework

frameworks/base/core/java/android/util/Log.java

frameworks/base/core/jni/android_util_Log.cpp

system/core/liblog/logd_write.c

Virtual Filesystem

/dev/events

/dev/main

/dev/radio

/dev/system
LOGGER

9. USB

10. LINUX CONFIG
 CONFIG_ANDROID=y
 CONFIG_ANDROID_BINDER_IPC=y
 CONFIG_ASHMEM=y
 CONFIG_ANDROID_LOGGER=y
 CONFIG_ANDROID_TIMED_OUTPUT=y
 CONFIG_ANDROID_LOW_MEMORY_KILLER=y

11. BENEFITS
 Troubleshooting/Debugging
 Extending framework and/or services
 Helped in writing native code

12. RESOURCES
 source.android.com
 androidxref.com
 Source code