the previous episode
This is one in a series of articles on working with the Android Developer
Phone (ADP1) device.
editor went through the process of updating the software on the ADP1.
This time around, we'll look at the latest
software builds, then take a beginning look at the process of actually
building new software for the device.
Your editor started by testing out the Android 1.5
images provided by HTC, the manufacturer of the ADP1. The provision of
these images is a nice step forward by HTC; thus far, ADP1 owners have felt
somewhat left out when new versions of the firmware have been released.
This time around, they have the new software at about the same time as
The 1.5 update is done in the usual way: use the "adb" tool to copy it to
/sdcard/update.zip on the phone, then reboot into the recovery
image to actually install the new code. Two such iterations are required
this time around; there is an update to the (closed-source) radio code
which must be applied first.
Sidebar: USB cables
If, in the process of pushing updates to the ADP1, you get failures with
"protocol error" messages, you're not alone. It turns out that the device
is sensitive to noise introduced by low-quality USB cables; one needs a
well-built cable for this task. Note: the cable packed with the ADP1 does
not qualify as "well-built."
So what's new in Android 1.5? The biggest user-visible feature is almost
certainly the on-screen keyboard. It's no longer necessary to open the
keyboard to send a quick text message. The on-screen keyboard is somewhat
painful for your fat-fingered editor to use when the phone is in the
portrait orientation, but it works better in the landscape mode. One has
to wonder, though, what inspired the Android developers to dedicate a
significant chunk of scarce screen space to a "smiley" key. There are
plenty of characters which would have been rather more useful in that
Beyond that, the 1.5 release includes "Latitudes" support for those of you
who want to continuously report your real-world location to the Google
mother ship. There are simple screen effects which come into play when
switching between applications and orientations. Holding the power button
gives quick access to "airplane mode." The camera is quite a bit
more responsive. The zoom icons are smaller and more discrete.
GPS acquisition is said to
be faster; your editor has not had a chance to test that claim, but it
would certainly be a welcome improvement.
The orientation-awareness (turn the phone on its side and the display
switches to landscape mode) that has been a feature of the JesusFreke builds
for a while is now part of the core platform.
And so on.
Mostly small stuff, but it's enough to make for a nicer feel to the
Speaking of the JesusFreke builds, the JFv1.50
build, based on 1.5, is also available; your editor promptly installed
it. This build is basic Android 1.5 with a number of additions, including
multitouch support, tethering support, an augmented init daemon, a
whole set of busybox-based command-line utilities, and more; see the full
list for the details. As usual, these builds add a number of nice
features to the phone; anybody who is interested in really playing with the
device will likely prefer the JF version of the software.
Remaking JF builds
Playing with new builds is fun, but this is free software. The real fun
comes from rebuilding the software from the source, perhaps with specific
changes. There are two levels at which this can be done. The first is to
use the JesusFreke "build environments." Essentially, the build
environment is a tarball containing the modifications made to create the JF
image, along with the necessary scripts. There's a new kernel containing
multitouch and unionfs support, along with the patches needed to create
it. Busybox is found there, as are a number of other useful diagnostic
tools, an ssh client, and more.
To create a new build, it is necessary to get the associated official
build, place it within the build environment, then run make. With
any luck, the end result is an update.zip file ready to be flashed
into the phone.
One of the interesting things your editor learned from looking at the
images (and from talking to Mr. Freke) is that the JF builds do not
actually involve rebuilding much of the Android system. It's mostly a
matter of unpacking an official build and making a few creative
substitutions. The kernel has been remade, as has the browser application
(to support multitouch zooming). Everything else is just a matter of
shuffling files around. So the JF build environments can be useful for
somebody else wanting to do the same kind of manipulations, but more
extensive changes require building the system at a lower level.
Building Android from source
Remaking Android from the source code turns out to be a bit of a challenge.
What follows here is a brief set of instructions derived from the Android
"building for Dream" page, some hints helpfully provided by GeunSik
Lim, and a fair amount of painful experience. In summary: most of the code
needed to rebuild the platform is available, but (1) it's not a quick
or simple process, and (2) there are a few pieces missing.
There's a number of tools which must be installed on a Linux system to
rebuild the Android platform. These include flex, bison, git, and the Sun
Java system. Beyond that, one must grab the repo tool. Repo
is Google's answer to the problem of managing a whole set of related
repositories; essentially it is a tool which sits on top of git and manages
a whole set of git repositories in parallel. Once repo has been
installed, the meta-repository is set up with a command like:
repo init -u git://android.git.kernel.org/platform/manifest.git
This command pulls down the manifest file describing all the repositories
needed to build the platform. Note that if a branch other than the trunk
is desired, it must be obtained during this stage with the -b
option; repo apparently cannot switch branches in an existing
One then obtains the code by running
"repo sync" and going out for coffee.
Incidentally, when you go out for coffee, you need not hurry back. It's
entirely possible to fly to a different continent, harvest the coffee by
hand (after waiting for it to reach the perfect ripeness), fly
home, and roast it yourself. You'll still probably have time for a second
cup before the downloading of the source is complete. You are, after all,
not just downloading a huge pile of source files. You are, instead,
downloading over 100 independent git repositories, each containing a long
trail of history - about 2.4GB worth of stuff. It takes a while. And,
needless to say, some disk space.
To make things worse, you still don't have all the source; there are a few
components of the binary platform for the ADP1 which have not been released
as free software. You cannot download those binary components from
anywhere; instead, what's needed is to obtain them from a working phone.
To that end, the file vendor/htc/dream/extract-files.sh contains a
script which will pull the needed components from a USB-connected ADP1
device. These components vary from files containing mixer settings to
programs for controlling Bluetooth, the GPS receiver, firmware for the
wireless network adapter, a camera control library, and more. The
dream directory also contains a binary driver module
(wlan.ko) for the WIFI adapter, despite the fact that said driver
is open source and included
in the distribution.
After that, it's a matter of copying build/buildspec.mk.default to
buildspec.mk in the top-level directory, editing it to set
TARGET_PRODUCT to htc_dream, and typing make.
And going out for more coffee, of course. At the end of the process, with
luck (a fair amount of luck may be required), there will be new system and
boot images which can be flashed into
the phone with the fastboot tool. A reboot will run the new code.
At that point, of course, there are some surprises to be found. One is
that the newly built software is lacking a number of features found in an
official build. The reason for this is simple: several of the
applications which run on Android phones are not open source. These
include the Gmail client (which your editor will happily do without), Maps
(which cannot be done without, at least until AndNav progresses a little further), and
more. These applications can generally
be recovered by grabbing the associated package files from an official
build and slipping them into the build environment. See this
article for a terse description of how that is done.
It took your editor a little while to figure out another little surprise:
despite the fact that the Android source tree includes a kernel repository,
the build process does not actually build the kernel. One might think that
it would be hard to miss something the size of a kernel build, but ... did
your editor mention that the Android source tree is big? The Android build
system which goes with this source tree is quite a piece of work; there
must be people working full time on it, and they probably hate their lives.
Trying to figure out what is happening in an Android build requires digging
through many thousands of lines of makefile rules. What your editor
finally discovered is that the build system simply pulls a binary kernel
from a special "prebuilt" repository (that repository also contains a
cross-compiling toolchain for the creation of ARM executables). The kernel
source tree, seemingly, is just there for show. Using something other than
the prebuilt kernel requires
making it separately and pointing a build-system variable at the location
of the result.
It's clear that even people who remake Android are not, in general,
expected to remake the kernel.
It's clear that even people who remake Android are not, in general,
expected to remake the kernel. The kernel repository pulled down by the
repo command does contain the Android-specific patches, but it
lacks nice things like branches (even "master" is missing) or tags. There
are some remote branches with names like korg/android-msm-2.6.27
which contain lines of development for various kernel versions; the 2.6.27
one appears to be, as of this writing, the one which is best supported on
real hardware. But, within those branches, there are (unlike the situation
with the rest of the Android code) no tags associated
with releases. Nothing in the repository will tell a developer which
kernel was shipped with a given version of Android.
So it's hard to build a kernel which corresponds to the one found within an
official release. But not impossible: most of the official releases
include the git commit ID in the kernel version. So by digging down into
the settings menus, your editor was able to determine that the HTC 1.5
build came from commit 8312baf. After checking out that commit,
one can do a make msm_defconfig to configure the kernel
properly. Then it's just a matter of setting the ARCH and CROSS_COMPILE
environment variables and doing the build. If you have a 32-bit Linux
environment, the prebuilt ARM toolchain provided with the Android source
does the job just fine.
Once the kernel build is done, it's possible to build a new set of firmware
images which can be loaded into the device with fastboot. That's
easy to say, but it can be harder to do; the sources from the repository
often do not build, and it's not always easy to get all the pieces together
to make a working image for the ADP1. Making it possible for people
outside of the core Android project to build and install the platform
appears to be an afterthought, at best.
Android and the ADP1
In truth, Google does not really support the ADP1 as a
system people can develop and run on; this situation was somewhat explained by Jean-Baptiste Queru, who is
easily the most helpful Google developer on the mailing lists:
Yes, the ADP1 situation is currently unfortunate. We've had to pick
priorities, the priority went to open-sourcing code out of Google,
as that's something that only Googlers can do.
The truth is, ADP1 isn't a phone from Google. While Google has some
influence on it (and provides a number of proprietary apps), It's
neither manufactured nor distributed by Google, and that puts
limits on the ways Google can support it (and espcially on how
Google can not redistribute some of the ADP1-specific files).
So, while the ADP1 is one of the most open cellular phone platforms yet to
appear, it does not, yet, represent a fully-open system in the way the
OpenMoko phone does. Most people wanting to do things with this device are
likely to end up starting with the official, binary builds and tweaking
things around the edges, much like as has been done with the JF builds.
That said, there is a lot of fun to be had with this device. It's fully
hackable at the kernel level now, and more hardware information is
becoming available, which raises the hope of gaining more control over the
low-level system in time. About the time the ADP1 becomes fully obsolete
and unobtainable, we should have it figured out pretty well. With any luck
at all, at least one of the devices which replaces it will be more open
from the outset.
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