The document summarizes efforts to port the Google Android mobile operating system to run on a Nokia N810 tablet device. It describes merging the Android source code with the Linux kernel used by the N810, addressing drivers and other changes. Key steps included porting the Linux kernel to a newer 2.6.25 version, adding Android patches, and resolving issues around filesystems, booting, and hardware support over nine days of development. Remaining tasks were noted as fixing crashes, adding WiFi and battery charging support.

2. Peter McDermott 马 岩

3. The NthCode Team

4. Porting Google Android to a Nokia N810 也可以在 NthCode.com 看看

5. Hear-Say 150 Google Engineers 2 years US$100 Million 687,860,000 人民 币

6. HTC G1

8. Android Is Java applications Dalvik VM ‘ C’ libraries Linux kernel

9. Dalvik? Java-like virtual machine But not a Java Why? Google says performance But probably because of $$ Dalvik? Java-like virtual machine But not a Java Why? Google says performance But probably because of $$

10. Dalvik Write Java foo.java Compile to foo.class apkbuilder foo.class... -> foo.apk foo.apk has foo.dex + metadata Transfer to device Run Dalvik foo.apk

12. Why Did Google Create Android? An open platform Where Google can ... ... make money from advertising?

13. Google released all the code Open source Royalty free / 免 费 看看 source.android.com 21 October 2008

14. How Hard Could It Be? We Thought ...

16. Nokia N810 Hardware 400 MHz OMAP 2420 ARM9 800x480 4.1” touch screen 128M RAM 2G flash WiFi Keyboard ** Not a phone ** Runs Linux Maemo US$425 / 2900 元

17. How Do We Make the N810 Run Android?

18. Merge Linux Kernel 2.6.21 + N810 Patches Linux Kernel 2.6.25 + Android Patches

19. Nokia N810 Linux Kernel 2.6.21 + MultiMedia Card driver I2C serial bus driver Touch screen driver Keyboard map Audio and video DSP Direct Memory Access (DMA) Board revision patch System software is Maemo GTK-based Lots of hackers ( 牛 !)

20. Android Patches Linux Kernel 2.6.25 + Goldfish YAFFS2 Bluetooth Scheduler IPC binder Low memory killer Ashmem RAM console & logging Android Debug Bridge (ADB) Power management Other changes

21. Goldfish Emulator CPU ARM926T Add 44 Files Not needed in real hardware

22. YAFFS2 Phones store data in flash memory YAFFS2 = Yet Another Flash File System 2 Optimized for NAND flash chips Add 35 Files Created by Charles Manning for Aleph1 GPL, but not in mainline kernel Integrated into Android by Google PCs store data on disks FAT, ext2, NTFS, xfs, afs ... All optimized for a spinning disk

23. Bluetooth 蓝呀 Change 10 files Fix headset bugs Add debugging Add access control

24. Scheduler Change 5 files Change impact not clear

25. IPC Binder InterProcess Communication (IPC) Add 2 files New kernel API Higher level IPC than standard UNIX

26. Low Memory Killer Add 3 files Scans processes, kills one New kernel API

27. Ashmem Anonymous SHared MEMory Add 3 files Named memory block Shared between processes Kernel can free Kernel can’t free standard SHMEM

28. RAM Console & Logging Add/change 3 files Puts kernel log in RAM Changes implementation Adds user space log read/write APIs New APIs

29. Android Debug Bridge (ADB) Add 3 files Connects Eclipse to an Android device USB Protocol

30. Power Management Add/change 5 files New APIs + changes

31. Other 36 files New APIs + changes Debugging Keypad lights TCP management ...

32. Which Kernel? Linux Kernel 2.6.21 Linux Kernel 2.6.25

33. Selected 2.6.25 ~75 files Drivers 163 files Some core OS User space quits if < 2.6.25

34. Port N810 to 2.6.25 MultiMedia Card driver I2C serial bus driver Touch screen driver Keyboard map Audio and video DSP Direct Memory Access (DMA) Board revision patch

35. Port N810 to 2.6.25 7 days Download Linux-OMAP git reset --hard v2.6.25-omap1 patch ... Compile/flash/debug/fix

36. Issue: WiFi No source for WiFi module Can’t recompile module No WiFi

37. Apply Android Patches to 2.6.25 Based on Linux 2.6.25 Goldfish YAFFS2 Bluetooth Scheduler IPC binder Low memory killer Ashmem RAM console & logging Android Debug Bridge (ADB) Power management Other changes

38. Android 2 days Android and N810 changes independent

39. Bring-Up 9 days jffs2 mmap() doesn’t work Switched to ext2 -- data corruption Switched to ext3 -- OK System hang at boot. Random reboots. Disabled watchdog Booted, but screen blank Applied a double-buffered video patch Sometimes booted, often crashed Copied libs to the N810, fixed crashes Touch screen wouldn’t work, changed power config Keypad not right, so changed keypad config

41. Next Steps Fix intermittent crashes WiFi Android Debug Bridge (ADB) Power off Battery charge

42. Peter McDermott [email_address] nthcode.com/pubs/porting-android-to-a-new-device.html