Use 3G modem data card in Android

We found Android-x86 had a new feature about telephony. It's about to use a 3G modem data card in EeePC and it can use 3G network to browse Internet. Therefore, I followed up this issue and verified it in Devkit8000 device. Now, it's one of our new released features and it comes with 0xdroid 0x4 release pre-built image too. In the beginning, I was trying to use a Quanta Q101 data card in Android emulator. How to run this experiment in my Ubuntu 9.10 manchine?



Set up Quanta Q101

Check this long discussion, I added a new rule file as below. When I plug-in q101 card, it can auto-mount to GSM modem mode with 4 ports.

erin@midnight:~$ cat /etc/udev/rules.d/30-q101.rules
#
# first, q101 will be detected as usb_storage of 0408:1000
# you have to force it suspend to change running mode from
# storage to 3.5g card

SUBSYSTEM=="block", ENV{DEVTYPE}=="disk", ACTION=="add", ATTRS{idVendor}=="0408", ATTRS{idProduct}=="1000", RUN+="/bin/sh -c 'cd /sys$env{DEVPATH};until test -f power/level;do cd ..;done;if [ -f power/level ];then echo suspend > power/level;fi'"

Wait about 10 seconds, then you can check these devices. RIL is /dev/ttyUSB3, PPP is /dev/ttyUSB1. When you use in Android emulator, it would become /dev/ttyS2 and /dev/ttyS3.

erin@midnight:~$ ls -l /dev/ttyUSB*
crw-rw---- 1 root dialout 188, 1 2010-04-27 16:34 /dev/ttyUSB1
crw-rw---- 1 root dialout 188, 2 2010-04-27 15:55 /dev/ttyUSB2
crw-rw---- 1 root dialout 188, 3 2010-04-27 17:16 /dev/ttyUSB3
crw-rw---- 1 root dialout 188, 4 2010-04-27 15:50 /dev/ttyUSB4

Need Kernel support PPP
I read this discussion and download Android kernel source code to rebuild kernel.

# git clone git://android.git.kernel.org/kernel/common.git
# cd kernel
# git checkout -b android-goldfish korg/android-goldfish-2.6.29
# cd $MYDROID/out
# ./host/linux-x86/bin/emulator -system ./target/product/generic/system.img -sysdir ./target/product/generic/system -data ./target/product/generic/userdata.img -kernel ../prebuilt/android-arm/kernel/kernel-qemu -ramdisk ./target/product/generic/ramdisk.img
# adb pull /proc/config.gz $MYDROID/kernel/
# cd $MYDROID/kernel/
# gunzip config.gz
# mv config .config
# make ARCH=arm menuconfig
(Add PPP in)
# make ARCH=arm CROSS_COMPILE=../prebuilt/linux-x86/toolchain/arm-eabi-4.4.0/bin/arm-eabi- zImage

Start the emulator again with new kernel image and then check /dev/ppp device!

# cd $MYDROID/out
# ./host/linux-x86/bin/emulator -system ./target/product/generic/system.img -sysdir ./target/product/generic/system -data ./target/product/generic/userdata.img -kernel ../kernel/arch/arm/boot/zImage -ramdisk ./target/product/generic/ramdisk.img
# adb shell ls -l /dev/ppp
crw-rw---- radio vpn 108, 0 2010-04-27 15:36 ppp

Modify Android source code
I applied the patches from Android-x86 and re-modified some code for Quanta q101 card. Also modify gprs script, since I am using Taiwan GSM netowork.

external ppp
http://gitorious.org/0xdroid/external_ppp/commit/6624b6760d8fde02993f3a3f02df3ec9db739e41

hardware ril
http://git.android-x86.org/?p=platform/hardware/ril.git;a=commit;h=b499fabc3459930a42f0ecc62257caef6aa216dc

system core
http://gitorious.org/0xdroid/system_core/commit/81b121623c3f05298b5166d03714655d1ab2ddf8

Since I am using Android emulator, the device names are different from Devkit8000.

Change the device permissions:

diff --git a/init/devices.c b/init/devices.c
index 4d93b44..0023cc3 100644
--- a/init/devices.c
+++ b/init/devices.c
@@ -108,6 +108,8 @@ static struct perms_ devperms[] = {
     { "/dev/android_adb_enable",   0660,   AID_ADB,        AID_ADB,        0 },
     { "/dev/ttyMSM0",       0600,   AID_BLUETOOTH,  AID_BLUETOOTH,  0 },
     { "/dev/ttyHS0",        0600,   AID_BLUETOOTH,  AID_BLUETOOTH,  0 },
+    { "/dev/ttyS2",         0660,   AID_RADIO,      AID_RADIO,      0 },
+    { "/dev/ttyS3",         0660,   AID_RADIO,      AID_RADIO,      0 },
     { "/dev/uinput",        0660,   AID_SYSTEM,     AID_BLUETOOTH,  0 },
     { "/dev/alarm",         0664,   AID_SYSTEM,     AID_RADIO,      0 },
     { "/dev/tty0",          0660,   AID_ROOT,       AID_SYSTEM,     0 },

Modify RIL argument and add ppp service from init:

erin@midnight:~/eclair/mydroid/build/target/board/generic$ cat system.prop
#
# system.prop for generic sdk
#

rild.libpath=/system/lib/libreference-ril.so
rild.libargs=-d /dev/ttyS2

# add these lines in system/core/rootdir/init.rc
service ppp /system/bin/pppd call gprs
 user root
 group system radio
 disabled
 oneshot

Run Android Emulator
After changing these code, rebuilt Android again. Then we can run Android emulator from below command:

erin@midnight:~/eclair/mydroid/out$ ./host/linux-x86/bin/emulator -system ./target/product/generic/system.img -sysdir ./target/product/generic/system -data ./target/product/generic/userdata.img -kernel ../kernel/arch/arm/boot/zImage -ramdisk ./target/product/generic/ramdisk.img -sdcard ./target/product/generic/sdcard.img -qemu -serial /dev/ttyUSB3 -serial /dev/ttyUSB1

Run ppp manually
After starting ppp service, it would appear one network connection called 'ppp'.

# adb shell
# start ppp
# netcfg
lo UP 127.0.0.1 255.0.0.0 0x00000049
eth0 UP 10.0.2.15 255.255.255.0 0x00001043
tunl0 DOWN 0.0.0.0 0.0.0.0 0x00000080
gre0 DOWN 0.0.0.0 0.0.0.0 0x00000080
ppp0 UP 115.82.23.238 255.255.255.255 0x000010d1

Add APN for Taiwan GSM network