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Relationship between Android and kernel

Hi all,
Looking to build my first custom Rom and had some queries terminology-wise.
What is the relationship between the kernel and Google's android platform? For instance, is froyo tied to a specific kernel and is this in the source tree?
Second q: HTC release their kernel sources. Say I wanted to get a froyo build up for a device that currently only has eclair, would the procedure be to diff the HTC modifications against the vanilla version and then make the appropriate changes to froyo?
Third q: what makes a Rom specific to a device? Probably linked to first question...
Many thanks,
Martin
Sent from my HTC Wildfire using XDA App

The kernel is basically just a linux kernel with device specific drivers and such added. I've done a 'diff' between the Eris 2.6.29 kernel from HTC and the 'generic' 2.6.29 kernel from kernel.org. It's kind of neat to see the difference. I highly recommend you do that.
There are also device specific drivers in the file structure that the ROM needs in order to function.
What I've done is compile AOSP from source, compile the kernel from source, zip up the needed files/folders, signed the ROM, and then flashed it to test. If you look at Android Builder in my sig, you can figure out the difference between the Eris and your device. You'll have to change the kernel that gets downloaded, of course. And it really just gives you a basic ROM without the device specific drivers, so things will not work without figuring the rest out. Grab a stock ROM to get drivers, libs, etc. out of.
/system/usr/keychars & /system/usr/keylayout usually have the keyboard drivers, which are somewhat important.
Also in my sig is the SgtShultz ROM where I tried to make a usable ROM from as close to source as possible. You might get some ideas from there. I still haven't figured out how to get the audio to work. If I get that worked out, I'll actually start using the ROM daily and work out the rest!
Froyo seems to work with kernel versions 2.6.29+, btw.

Many thanks for this; it's given me a good set of places to start reading.
Just pulling down all the AOSP source as we speak, with the hopes of getting a basic build up in the near future

gnarlyc said:
What I've done is compile AOSP from source, compile the kernel from source, zip up the needed files/folders, signed the ROM, and then flashed it to test. If you look at Android Builder in my sig, you can figure out the difference between the Eris and your device. You'll have to change the kernel that gets downloaded, of course. And it really just gives you a basic ROM without the device specific drivers, so things will not work without figuring the rest out. Grab a stock ROM to get drivers, libs, etc. out of.
[...]
/system/usr/keychars & /system/usr/keylayout usually have the keyboard drivers, which are somewhat important.
[...]
Froyo seems to work with kernel versions 2.6.29+, btw.
Click to expand...
Click to collapse
A couple of questions on this front...
I can see, obviously, where to get the kernel source and needed drivers; I am, however, unclear as to where I should obtain AOSP drivers from (to go, for instance, in /devices/htc/buzz and/devices/htc/buzz-common). Can I extract these from my device? (or do I need to wait until they release Froyo and then extract them from a device running the newer build?) Where on the device should I be looking for this driver set?
Thanks again,
Martin

MartinEve said:
A couple of questions on this front...
I can see, obviously, where to get the kernel source and needed drivers; I am, however, unclear as to where I should obtain AOSP drivers from (to go, for instance, in /devices/htc/buzz and/devices/htc/buzz-common). Can I extract these from my device? (or do I need to wait until they release Froyo and then extract them from a device running the newer build?) Where on the device should I be looking for this driver set?
Thanks again,
Martin
Click to expand...
Click to collapse
For the most part, any Eclair drivers seem to work. At least that's what I have used for the Eris. 2.1 -> 2.2 isn't too big of a jump. I used drivers from a stock 2.1 ROM.
Look up vendor tree, vendor config, and 'extract-files.sh'. You'll see what people with other devices have done. I have yet to quite get the whole vendor tree thing worked out, but others have. You can just come up with a list of needed drivers to add to the 'extract-files.sh' script and just copy those files in manually. (That's what I have done.) This will get pretty close to making an AOSP build complete. However, it appears that actually using the vendor tree setup while compiling will get things 'right'. There appear to be some libs that will compile differently for different devices.
So, basically, if you compile AOSP without a vendor tree for your device, the build will be located in out/target/product/generic. (And, you can copy drivers in later while using the kitchen, but you might miss out on some AOSP stuff with device-specific changes.) If you use the vendor tree, it will be in /out/target/product/buzz and will contain the drivers that the 'extract-files.sh' script grabbed from your device along with custom compiled libs.
If you are able to get a working vendor tree for your device, it will be helpful to the entire community. They'll all be able to use it for their builds. I highly recommend doing that. Most groups use github or something similar to post the code.
I still have much to learn myself, and you are starting to reach my limit! Good stuff.

Hi,
Many thanks for your reply; to a degree, it's about knowing the terms to search for -- the extract-files.sh is a godsend for information that I would have otherwise missed.
Anyway, onwards to build a usable vendor tree
Best,
Martin

[Q] Compiling package from source, won't run on custom ROM?

I'm sure I'm making some sort of rookie mistake here, but I'm currently running a custom ROM (4.0.3-based) on my device. I wanted to add some functionality to one of the system packages (Exchange.apk) and rather than hacking up smali, I downloaded the AOSP 4.0.3 source and modified the code for the Exchange package directly and compiled (which compiles fine) -- however, I can't seem to actually use the compiled/output Exchange.apk on the device.
I'm assuming it has something to do with system signatures, but everywhere I read said you do not sign system APKs. Soo...
What am I missing?

[Q] Help needed porting CM11

Since development for the Sidekick 4G has stopped I decided to try and port the CM11 M10 snapshot from the Galaxy S 4G using this guide. I used the Galaxy S 4G as port ROM since most of the specs are the same as the SK4G. The base ROM I used is ayoteddy"s KJ2 Deodexed & rooted ROM. I followed the guide and flashed the ROM I made but the phone didn't boot. It stays stuck at the tmobile startup screen and then bootloops. I took a logcat and see a lot of errors but idk how to correct them. I tried uploading the ROMs I used and the one I created but it only let me upload the logcat.

Hey,
Its awesome to see some more effort in this phone but when porting a ROM one of the main prerequisites is the base being the same android version.
So to port cm11 over you would need a kitkat kernel and ROM for the sk4g already.
What would be real helpful is to get the gingerbread kernel fully functional then any GB ROM could be ported fairly easily.
Or start with a kitkat kernel but both require a bit of work. If you want to take it on a can link a bunch of guides that may help

Thanks for that info. I don't have experience coding but I would like to be able to learn how to cook and port roms so I would really appreciate some guides. As I understand it, since there is no KitKat ROM available for the sk4g I would first need to make my own KitKat kernel and ROM before I would be able to port cm11? And how long do you think it would take to learn everything needed to be able to port and cook roms?

Hey,
On mobile right now so can't post a bunch of links but xda is filled with them
The best place to start would be http://www.xda-university.com
And be sure to check out the forum links as well!
For a quick set of links see the seventh post in this thread
http://forum.xda-developers.com/showthread.php?t=2348266
For a different device but those are all great places to start learning to develop for android
Keep me posted on your progress!

Took me a while to find some useful guides since I was searching with the term "port" and not "build/compile from source" since that is essentially what I'm doing. I used wiki.cyanogenmod.org/w/Doc:_porting_intro and wiki.cyanogenmod.org/w/Build_for_galaxysmtd (can't post links yet). I forked the galaxys4g repo and modified the files to be suited for the sidekick4g. Now I'm onto the building step, a couple of things already broke and I managed to fix them, but I ran into this error and haven't been able to fix it.
brunch sidekick4"ebtables is disabled on this build"
find: `src': No such file or directory
build/core/base_rules.mk:134: *** system/extras/ext4_utils: MODULE.TARGET.EXECUTABLES.setup_fs already defined by device/samsung/sidekick4g. Stop.
I researched the MODULE.TARGET.EXECUTABLES.setup_fs already defined by device/samsung/sidekick4g issue and suggestions were to delete the setup_fs file within device/samsung/sidekick4g folder. However the setup_fs file wasn't in there, I did find a setup_fs.c file and deleted that one. Then I proceeded to try the build again and ran into the same error. Another suggestion was to use grep -R setup_fs *. This command pointed to these files,
Android.mk:LOCAL_SRC_FILES := setup_fs.c
Android.mk:LOCAL_MODULE := setup_fs
Android.mk~:LOCAL_SRC_FILES := setup_fs.c
Android.mk~:LOCAL_MODULE := setup_fs
initramfs/init.herring.rc:service setup_fs /system/bin/setup_fs /dev/block/platform/s3c-sdhci.0/by-name/userdata
sidekick4g.mk: setup_fs
But I don't know what exactly I'm supposed to delete. The device repo is located at github.com/SK4G/android_device_samsung_sidekick4g.git It is a pre-build attempt version before I made suggested changes to the local repo. I tried "git push origin master", the command went through and said everything is up to date but the remote repo still wasn't changed so I haven't been able to update it.

What are you using for the device tree? The relay is a completely different device and none of the drivers would work, did you at least pull blobs and proprietary files from a sk4g?
There is a ton of setup to be done in order to build from source, you can use the cm11 source but need to make a specific device tree for the sidekick to get a working build, not to mention a ton of kernel work will be needed

For the device tree I forked the galaxys4g repo (not the galaxy s relay 4g) and then modified the files to build the sidekick4g specific device tree. When pulling the blobs and proprietary files the guide said " Your device should already be running a build of CyanogenMod for the branch you wish to build for the extract-files.sh script to function properly". Not sure if that's relevant to the errors but I was still able to pull the blobs towards the correct ~/android/system/vendor/samsung directory. As far as the kernel I downloaded the stock kernel from the samsung source website and then put it in the kernel/samsung/sidekick4g directory. The guide said that the kernel and kernel modules would be built automatically as long as I made appropritate changes to the BoardConfig.mk and I did so. I have done every step in the guide and now I'm into building but I can't get past the previously mentioned error. Should I delete the whole part of the files mentioned by the grep -R setup_fs * command or just the red part or is there another solution?

Well the blobs that were pulled and the kernel that was used was for froyo, that won't work for kitkat without a weeks worth of modification
Also the s4 is even more different than the relay and would be much harder to use anything from there
What you need at this point is to create your own device tree on github and add this to your local manifest, then the hard part is to adapt the sk4g kernel into something that will work with kitkat, once this steps are complete you can build and then fix the errors that come up, fixing any errors at this point won't help much as the files used are incompatible from the start

I should have been more specific, I used the T-Mobile Galaxy S 4G which is one the first galaxy phones. It has the same hummingbird chipset, architecture, ram/rom size, resolution, and both originally ran froyo. The guide states that the cm buildbots build a compatible kernel for me. I didn't just fork the galaxys4g repo and leave it as is. I went through the files and substituted anything that was galaxys4g device specific to fit the sidekick4g.

No problem, should have read more clearly, yes the galaxy s is very similar minus the keyboard but you can look at the work that was done to get a GB ROM booting here
http://forum.xda-developers.com/showthread.php?t=2323617
This was done on the exhibit, another very similar phone,
Even after the kernel was adapted the keyboard never worked, you check the link to his github to see what was put into it to work
The kernel built by the bot won't adapt it to work between different versions of android so you need to build this manually first then you can use it, but even then there will be a lot to do in order to get the keyboard working

Now I'm beginning to understand what you have been trying to tell me. It was hard to grasp at fist because I never really looked into building a kernel since I usually just use the stock kernel or the cm built in kernel on my devices. Now I shall redirect my efforts into building a kernel

Hi I just wanted to know if you're still building port for the sidekick 4G I still have mine and I would like to use if you have kitkat to work. I miss my sidekick 4G
Sent from my Nexus 6 using XDA Free mobile app

Android compiling

So ive been unfortunate so i cannot get A12 on my Xperia 1(J9110). But on dev.sony there is a compile guide for 12. I tought i will compile it from there.
But it cant be "that easy", i suppose it will have bugs that i need to fix but the last language i used was html in high school(yea yea get on with it).
My question is: if i compile it for myself can i use it as out-of-the-box or do i have to fix stuff or its an useless idea?

You would need to check if your device is listed in the devices.xml. If it is listed, there is a possibility that Sony has been updating the device tree, kernel and vendor blobs for android 12 and you could try compiling.
If it's not there, you won't be able to compile at all for your device without making a device tree, extracting vendor blobs and finding the right kernel for android 12, which would take a lot of work.

Griffin is there which means there is a chance. Still, can i use it out-of-the-box?

Question attempt at learning how to compile TWRP for our device.

I am not an experienced dev, and only know enough to be dangerous. that said, i used twrpdtgen from https://github.com/twrpdtgen/twrpdtgen to generate what ought to be the berlna device tree with the necessary board files etc.
what do i have to do, specifically, to clone the twrp source via git/repo? can anybody here explain it like you realize i don't know what i am doing i'll figure git and repo out eventually, but this will go quicker if someone would enlighten me
which android version do i want to build twrp with? apparently 12.1 support isn't finished yet, so i should use 11 with aosp source?
note, for our deivce you need to use the script on upon boot.img as we've a/b format, grab from latest stock rom to gen yourself, or see attached. also, necessary to use WSL on windows with a linux distro, or a linux vm, python on windows will not work.
please feel free to use these if it furthers the cause of compiling twrp before i learn how to use git and repo and compile it.. hehe

I wanted to try my hand at this and start digging into git and repo. I got as far as getting all the files ready, setting up the tree where it needed to be, used ". build/envsetup.sh", then lunched with option 5, which is omni-berlna_eng, which is closest to the twrp minimal manifest build option.
After I lunch, the issue arrives with the fact that omni-berlna_eng uses a depreciated PRODUCT_STATIC_BOOT_CONTROL_HAL, whatever that means. So I tried using lunch option 2, which would be an aosp-arm64_eng, but that just gives me the error "#### failed to build some targets (1 seconds) ####".
As of now, I'm at a loss. I don't have the extra time to spend working on this to make it function, and I only get a few hours at a time to get a crack at it, but nothing seems to work.
Edit:
I should mention, this is my first attempt at anything android development. I got this phone as a secondary carry on and I've dirtyflashed Pixel Experience onto it using a method found for Moto G Power TONGA. Wanted to see if I could get TWRP running since dirty flashing killed my mms and calling services.