I followed the guide on android.com and compiled the source code. Now it runs well in the emulator. There are some .img files so I think it may be viable to flash them on real devices.
But I see on the guide there is a 4th step, which is to compile some device-specific proprietary files. But my device is not on their list. So what extra work needs to be done if I want to flash the .img files to real devices rather than the emulator? Will the real devices get bricked? Thanks.
well -- that is the "difficult" part of making a custom ROM for a device. You need to have a complex understanding of the particular hardware that you're building for, and adjust and update the codebase accordingly.
That said -- a real device will (probably) not get bricked, but you will need to use the recovery image to put a working ROM back on to use the device again. Make sure you have a rooted device and a decent recovery on it (Clockworkmod)
Related
I want to modify the system apps running on my specific phone. I am stumped about some important steps on how to do that - see my questions further below.
N.B.: I am not interested in deploying these modifications to other phones. Instead I want to play with the original code and improve it. Hence "create your own system app" is no sufficient answer.
Background
I am just starting to get into Android development (have sufficient Java knowledge, though). There are plenty of great tutorials out there (e.g. here and here) but they all seem to cover user application development. I'm more interested in getting (a little) "closer to the metal". Unfortunately I am unable to find good sources teaching how to do that.
Example
As an example let's say I want to modify how the built-in brightness control works (e.g. changing the minimum) or want to add features to the call screen (e.g. "Send SMS instead" when the line is busy).
Specific Questions
I obviously need these things to get started...
Sources
The sources for (parts of?) the OS running on my phone. This is the part that confuses me the most. Can I just download the official sources or is it likely that my vendor made modifications?
In my specific scenario (I use a Fairphone), could those modifications be contained in any of these sources:
some core apps deployed by the vendor
the image binaries (some way down the page)
sources for the Linux kernel and some other libraries
Tools
I really hope to stay in Java-land. But either case I need a development (I hope to use Android Studio or Eclipse ADT) and a debugging environment (I hope the Android Virtual Devices suffice).
Is it a valid assumption that I can use those tools for system apps or are they usually implemented in C?
Process
Assuming I can download the official sources and get started with, e.g. Android Studio. As opposed to developing a user app, do I have to do anything special to emulate the modified system app on AVD?
I'm asking because I assume that AVD already runs an unmodified version of that very app.
I am just starting to get into Android development (have sufficient Java knowledge, though). ... I'm more interested in getting (a little) "closer to the metal".
You can of course follow your own bliss, but you may find it pretty frustrating to learn Android development by hacking on the OS itself. You'll find yourself doing a lot of OS debugging and working with harder-to-use tools than normal.
Example
As an example let's say I want to modify how the built-in brightness control works (e.g. changing the minimum)
I realize this is just an example, but this could be a tough one, because there are a lot of things that contribute to brightness control -- there's the app with the UI that sets it, but that talks to the framework and ultimately the driver for the hardware that actually deals with brightness curves for the display, in coordination with the ambient light sensor.
or want to add features to the call screen (e.g. "Send SMS instead" when the line is busy).
There's a dialer app, but implementing a feature like that will be...difficult, provided it's even feasible. I don't know offhand whether that sort of call state is available to the API.
Specific Questions
I obviously need these things to get started...
Sources
The sources for (parts of?) the OS running on my phone. This is the part that confuses me the most. Can I just download the official sources or is it likely that my vendor made modifications?
If you're replacing system apps, you'll need to run an OS signed with debug keys; you don't have access to the signing keys for the installed system apps on a retail build of the OS that would enable you to replace them. That will mean either getting a debug-keys installation or building it yourself from source, and flashing it to your phone. I would most strongly discourage you from using your daily phone for this sort of work -- you don't want it to be bricked when you need to receive an important call.
If you're not running a Nexus phone, then yes, your vendor has made modifications. The system apps are probably modified, and you almost certainly won't have access to the closed source of those apps. Also, there will be closed-source device drivers that are essential to the operation of the OS that you won't have access to. If you're trying to get AOSP Android up and running on such a device, as an individual hacker it's at best very, very difficult. If you're willing to use something like CyanogenMod, you could look to see if (and to what extent) they support your hardware.
If you are running a Nexus phone, then it's a goal of the AOSP project to try to have the OS bootable on select Nexus devices, though you won't necessarily enjoy the fullest functionality of the retail OS build, depending on the state of drivers -- even Nexus phones can have closed-source drivers and bits that make life more, um, exciting for building with AOSP.
In my specific scenario (I use a Fairphone), could those modifications be contained in any of these sources:
some core apps deployed by the vendor
Almost certainly
the image binaries (some way down the page)
Not sure what you mean by that
sources for the Linux kernel and some other libraries
It's unlikely there are significant modifications to the kernel itself, though vendors sometimes do...interesting...things with system configuration. I already mentioned device drivers. Vendors also have custom implementations/modifications of some framework APIs.
Tools
Vendor-specific tools are rare.
I really hope to stay in Java-land. But either case I need a development (I hope to use Android Studio or Eclipse ADT) and a debugging environment (I hope the Android Virtual Devices suffice).
Much of what you want to do can probably be implemented in Java, though it depends on how close you're getting to the hardware which can be difficult to know.
Is it a valid assumption that I can use those tools for system apps or are they usually implemented in C?
The "system apps" are implemented in Java, but again, you sort of have to know where the dividing line is.
Process
Assuming I can download the official sources and get started with, e.g. Android Studio. As opposed to developing a user app, do I have to do anything special to emulate the modified system app on AVD?
That's actually different, because you're dealing with an emulator system image instead of a phone image. The emulator system images are completely open source, and you can build them from AOSP.
I'm asking because I assume that AVD already runs an unmodified version of that very app.
That's correct.
To come back to my initial point, if you read between the lines of what I'm saying, I won't tell you it's impossible, but the difficulty ranges from freakin' tough on the easy end to spend-years-of-your-life on the hard end. If you really want to proceed, your best bet may be to buy the phone that's best supported by CyanogenMod and work that angle; there's a more active developer community there to help you. I know you're more excited about trying to customize the OS than you are in making a user-space app, but you'll experience less frustration with the latter than the former.
I am interested in building Android for Source for a Galaxy S3 (but just knowing how to do it in general will be quite helpful)
I know how to do it for all the nexus devices in general, but I was wondering how to do it for some of the other phones. I know that it is possible because CyanogenMod and other modders do it. Usually when they announce them they include the source for the kernel.
How do you put the pieces together? Getting the android source code and the custom kernel together in something that can be flashed.
Generally it is not trivial. You need some binary files for hardware support (camera, WiFi, NFC, etc) and you need to figure out which those are and how to pull them from the device. The kernel is GPL licensed, so the the manufacturer will release their version/patches at some point, but you might have to wait. Then you have to create device build files to put all those together in an image for the particular device. Your best bet is to get CyanogenMod source and see how it is done in practice.
I need to reproduce a bug that I think is on devices running Android 2.1-update1. The emulator options exist for 2.1 but I don't see option for update 1? It is important to be able to test for all device scenarios, so i need to know how to create AVD for a specific update.
You cannot get the emulator to match exactly devices, you can only test against "vanilla" Android releases from Google.
Unless you can get images from the device manufacturer or source code for the kernel (which you should be able to find or request) and of the Android framework (which will be quite more challenging to obtain) that you can recompile and generate the proper images, then you are out of luck.
INHO, the emulator is really a great tool to help you develop applications, but it does not replace a real device when it comes to testing.
I own a Samsung Galaxy 3 and want to port kernels available for other Android Devices. I have all building environment ready. I have C knowledge also. What exactly I dont understand is how and what all things porting involves, which codes should be modified in what way?
If someone could help me. It would be great.
Thanks in advance.
Ok I got it. But the real problem is I dont understand one thing.
What needs to be changed in the source code so that to make it compatible in other device? Can someone explain me that?
Idolon gives a good suggestion. In theory what is written there is true. In practice, it's a little more involving. I've been porting Android Kernel for months now. My goal was to have a custom S5PV210 processor module on my custom board with my custom I/O. I have the source code for Samsung's galaxy tab and several Samsung's android smartphone as well as a few versions (Froyo, Gingerbread) for the Samsung's Evaluation board (SMDKV210 for S5PV210 CPU). FYI, S5PC110 is a close derivative. Here is what I found out.
Eventhough all the device drivers are supposed to be built in a very modular way and independent from each other and you should be able to replace them with similar devices, the way Samsung did it is not exactly that. To give you one example is about power management. In many low level drivers dealing with hardware devices, it calls some specific routine for other hardware devices like power management chip. So, When you change the choice of drivers in the "make xconfig" or "make menuconfig" it will remove the source code of what you don't want and add the one you want but, there are still other modules that are calling the low level function you removed. When building, you will get tons of unresolved external because you removed a power management chip that your hardware doesn't have but is used in the source you started with. I looked through several Samsung's device source code and they have branched very early on. They have been adapted by different teams and it would be a major amount of work to go from one device to the other from one source kit.
Here is how I succeeded: I bought an S5PV210 evaluation board with an already ported Android Kernel (Gingerbread). All the power management and inter dependant issues where already cleaned-up. Then, form a working kit, I could change the device I needed (the one you can't buy without a 100K unit/yr commitment) without getting stuck with the interdependancy. Then I could even change LCD resolution (from 800x480 to 1024x768), touchscreen, Cell modem etc etc. The whole thing takes about a month worth of work with only one guy (me).
Starting with a Galaxytab or other commercial device made me waste months of headakes with no useful results but the thing I've learned.
There is one requirement to succeed on my approach. You have to know the hardware you are working on. As an example, you need to know what touch screen your hardware has (chipset) to select the driver and were is it connected to hook it up to the right device (USB, Serial etc). That the same thing for all other devices (power managemnt chip, keypad, backlight, LCD etc etc)
Hope that is useful to give you an idea of the work involved and how you can do it.
You should take a look at the cached copy of Android Platform Developer's Guide and at android-porting google group.
There is also an old but useful article about porting Android to Nokia N810, which will give you some hints about Android Linux kernel porting.
I am also into android porting stuff for quite some time I suggest the following route :
Read
You need to have basic knowledge of android porting and AOSP source code, directory stucture hierarchy.
I suggest you to start reading https://books.google.co.in/books/about/Embedded_Android.html?id=plHsngEACAAJ&hl=en
and also refer https://source.android.com/devices/index.html as good guys pointed out you can also google android porting related groups and become a member there, if you are stuck on a issue there are chances similar issue might have been faced by someone else previously.
Observe
AOSP code :
Parallely you need to dive in to the android source e.g from links like https://android.googlesource.com/ observe which components are placed where in the source code, what are the updates from previous android release (like ART replaced dalvik in LL), at top level there would be generic code, code specific to your hardware called HAL in hardware/ and device/ folder.
Kernel code :
In the kernel also you need to observe the directory structure and know which things lie where like SoC specific code will be in arch/ directory defconfigs (used for selecting kernel configuration) will be arch//configs/ directory.
Also there are good books available for linux kernel, you can google them and start reading them also.
While porting kernel you need to take care of following
1.If in the new kernel there is already support of SoC which is used in hardware to be ported then you need to add only device specific changes like suppose you want to port new kernel version to samsung galaxy s3, you can take a reference android kernel having exynos support and then you need to make changes only for adding support for samsung galaxy s3.
For that you need to have reference of some old kernel having support of s3, from there you can study patches which have been added to add support for s3 and port those patches to newer kernel.
Experiment
First you can only port the bare minimum changes required to up the platform, compile and flash it on your platform, then observe the output, if everything looks fine than go on for next changes otherwise try to solve the issue.
Thanks,
Devarsh
I have a Symbian based phone with a ARM Cortex-A8 processor (SonyEricsson Vivaz) and was thinking on how hard would it be to try and port the Android OS for it. Obviously Android runs on a myriad of devices with different hardware so I imagine it shouldn't be too hard to adapt it to SE hardware. Could some one give me a clue where to start or if this is even undertakable...
How much information do you have about the hardware in the phone ? Are you starting completely from scratch ?
Porting Android is not simple task. First thing is to have Linux running (preferably 2.6.32 for more compatibility with the latest releases of AOSP.
If you can find a kernel that can run on your phone, that's one big step. After that, you want make sure that the peripherals you want to use also have the right drivers : touch interface, LCD display, SD card, audio, video. The ones that are probably most difficult will be wifi, radio (GSM) and power management module.
If you get that far, you don't have that much to go anymore, a few more changes in the kernel needed for Android, be able to compile Android correctly file system, hook up a few things like buttons and correctly interface with the drivers mentioned above...
But overall, definitely not an easy task (IMHO).