[Q] Where to start for Android Kernel Development? - Android Q&A, Help & Troubleshooting

Hello Guys,
I see a lot of threads for starting with android rom development, but can anyone give me pointers for kernel development? I would like to start kernel development and do not know where to start. I am not interested in rom development at the moment, but that is because I assume that the android rom is like a user space app over the kernel. Please correct me if I am wrong. It would be great if you guys could point me to some beginner friendly kernel development tutorials. I am looking through Linux Device Drivers (LDD) book but am having a hard time comparing that with android. I have cloned mediatek 6589 source from android repository. I am submitting partial url cos I am not allowed to submit full url yet. URL(android.googlesource.com/kernel/mediatek/+/android-5.1.0_r0.2) since I am running a mtk6589 device (Walton X1/ Gionee Dream D1) and would like to understand where to start coding kernels for android. Any help would be greatly appreciated.
Oh and I would like mediatek specific help if possible. I have gone through some of the general kernel building and overclocking tutorials. I want to do some more enhancements if possible. Since mediatek seems to be the mysterious one with bare minimum source availability, I would like to take up that challenge
Thanks.

I don't have a tutorial for you but a small checklist. You need:
* Kernel source tree
* A config for your device (e.g. arch/arm/configs/*defconfig*)
* A cross compiler toolchain to generate ARM code (you can use the precompiled one from the Android source tree)
* A way to package your kernel into a boot image for your device - usually an Android boot image contains a compiled kernel (zImage), a compressed ramdisk for the root filesystem, and probably a device tree binary (dtb). Mediatek may do things differently.
* A way to install that boot image on your device - this requires an unlocked bootloader that allows custom boot images to be installed and started. Most devices use the fastboot tool for this.
Your first step should be to build a working kernel from unmodified sources. When you got that working, you can think about starting actual coding.

Thanks for the Pointer Mate
_that said:
I don't have a tutorial for you but a small checklist. You need:
* Kernel source tree
* A config for your device (e.g. arch/arm/configs/*defconfig*)
* A cross compiler toolchain to generate ARM code (you can use the precompiled one from the Android source tree)
* A way to package your kernel into a boot image for your device - usually an Android boot image contains a compiled kernel (zImage), a compressed ramdisk for the root filesystem, and probably a device tree binary (dtb). Mediatek may do things differently.
* A way to install that boot image on your device - this requires an unlocked bootloader that allows custom boot images to be installed and started. Most devices use the fastboot tool for this.
Your first step should be to build a working kernel from unmodified sources. When you got that working, you can think about starting actual coding.
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Thanks man. Really appreciate the pointers. I do have some of the checklists done. Like
* Kernel source tree
** A cross compiler toolchain to generate ARM code (using the precompiled one)
* A way to install that boot image on your device
Now the problem is, my device still does not have its source code available. I got the general source tree from google which is not my device's so I dont have the defconfig. Is there a way to rip it out from a compiled kernel? Like using some sort of a decompiler? Also I will look around for zimage packaging tools. Thanks mate. Mediatek is apparently one hell of a problem child XD

syko_kickass said:
Now the problem is, my device still does not have its source code available. I got the general source tree from google which is not my device's so I dont have the defconfig. Is there a way to rip it out from a compiled kernel? Like using some sort of a decompiler? Also I will look around for zimage packaging tools.
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If you're lucky, your existing kernel exposes its config in the file /proc/config.gz. If not, I don't know how to get a matching config - best is to avoid buying anything from GPL violators.

Related

[Q] How to add new device tree,new kernel source code to CM source & compile?

Hello everybody.
I have a noob question about compile cyanogenmod for my new device.
Now, i have: CMW recovery, Kernel source code on local computer, full repo cm source + toolchains.
How to add my device tree, kernel source code to CM source and compile CM7 ROm?
Thanks you, cheer
Anyone here?
Did you figure it out yet? I asked the same question and am waiting for an answer, tho I'm on CM 10, HTC Vivid. If I figure it out I'll post back and try and help.
nguyenhonganh said:
Hello everybody.
I have a noob question about compile cyanogenmod for my new device.
Now, i have: CMW recovery, Kernel source code on local computer, full repo cm source + toolchains.
How to add my device tree, kernel source code to CM source and compile CM7 ROm?
Thanks you, cheer
Click to expand...
Click to collapse
I met the same problem, does anyone can help?
Do you have a device tree? Or do you have an unsupported device? If you have an existing device tree from some other ROM, etc, then you just need to edit your .repo/local_manifest/roomservice.xml to pull in the trees that you need.
If you need to create a device tree, then it gets not complicated, as each device is different. The basic process is to create the necessary directories (device/manufacturer/model, kernel/manufacturer/model (may need to be kernel/manufacturer/device_family/model, for reference to that, see CM's repo for the LG G3) and finally vendor/manufacturer/device.
After you have the directories setup, you will need to actually start building the tree. The easiest way is to copy another devices files into your devices tree, and then edit the files. The closer the device you copy in is, the less work you will need to do to the files. Refer to sites like gsmarena.com, PhoneArena.com, etc for phone specs.
That's about as far as I can take you without dealing with a specific device. If you need more info, post back here with your questions, and post your device specs, or at least the model number,and I'll see if I can help.
rassawyer said:
Do you have a device tree? Or do you have an unsupported device? If you have an existing device tree from some other ROM, etc, then you just need to edit your .repo/local_manifest/roomservice.xml to pull in the trees that you need.
If you need to create a device tree, then it gets not complicated, as each device is different. The basic process is to create the necessary directories (device/manufacturer/model, kernel/manufacturer/model (may need to be kernel/manufacturer/device_family/model, for reference to that, see CM's repo for the LG G3) and finally vendor/manufacturer/device.
After you have the directories setup, you will need to actually start building the tree. The easiest way is to copy another devices files into your devices tree, and then edit the files. The closer the device you copy in is, the less work you will need to do to the files. Refer to sites like gsmarena.com, PhoneArena.com, etc for phone specs.
That's about as far as I can take you without dealing with a specific device. If you need more info, post back here with your questions, and post your device specs, or at least the model number,and I'll see if I can help.
Click to expand...
Click to collapse
I have a mt6750 devices... And there is a device from my company manufacturer.. Its a mt6750 device, it have cm device tree.. Both device working on same rom.. I can port that device rom but it always give me bugs.. So my question is how to use it?

[Q] Build a Custom ROM using only kernel source?

The HTC Desire 310 runs on a MediaTek SoC, and HTC only has the source code for the kernel. Is it possible to build a Custom ROM like CM for the device? And what are the drawbacks of doing this?
Lynuxen said:
The HTC Desire 310 runs on a MediaTek SoC, and HTC only has the source code for the kernel. Is it possible to build a Custom ROM like CM for the device? And what are the drawbacks of doing this?
Click to expand...
Click to collapse
Basically all a ROM development takes is a kernel source ,a device tree(how the source has to build your ROM {resolution,kernel source command lines....etc are set here}) , a vendor tree( usually proprietary shared libraries got from stock ROM ). Once you've got all these all you have to so is type make bacon. But since its mediatek its pretty hard to build anything since mediatek ril/libraries are not open source.
So doing this blindfolded won't work.
Lynuxen said:
So doing this blindfolded won't work.
Click to expand...
Click to collapse
Won't work, unless you set up a device tree for your SoC. MT6589 device tree may work for building only recovery but nothing further.
Yes, as @MasterAwesome said you need actually 3 components: Vendor tree, kernel source and device tree. Making vendor and device tree from scratch is hard.
GeekyDroid said:
Yes, as @MasterAwesome said you need actually 3 components: Vendor tree, kernel source and device tree. Making vendor and device tree from scratch is hard.
Click to expand...
Click to collapse
Hard, but not impossible? I really want to invest my time in something like this. Pretty long shot, will something like a method for reversed engineering the vendor and device tree work?
Lynuxen said:
Hard, but not impossible? I really want to invest my time in something like this. Pretty long shot, will something like a method for reversed engineering the vendor and device tree work?
Click to expand...
Click to collapse
Vendor tree is pretty easy to setup. You'd want to start with the CyanogenMod version which is similar your current android version. If your device has kitkat download cm11 sources. Read their docs about setting up a device tree(its not that hard). Vendor tree is basically just your stock ROM use it as a base to get your libs which are required for your ROM to start(logcats are helpful here). Since you have a similar SoC, you can use my device tree as a reference https://github.com/MasterAwesome/a210_device_tree/tree/master/micromax/a210. Initially just build a kernel and check if it works. And I have guides for kernel and ROM building,you could check it out.
MasterAwesome said:
Vendor tree is pretty easy to setup. You'd want to start with the CyanogenMod version which is similar your current android version. If your device has kitkat download cm11 sources. Read their docs about setting up a device tree(its not that hard). Vendor tree is basically just your stock ROM use it as a base to get your libs which are required for your ROM to start(logcats are helpful here). Since you have a similar SoC, you can use my device tree as a reference https://github.com/MasterAwesome/a210_device_tree/tree/master/micromax/a210. Initially just build a kernel and check if it works. And I have guides for kernel and ROM building,you could check it out.
Click to expand...
Click to collapse
Massive thanks MasterAwesome. :highfive:

How to get kernel, device tree and vendor blobs?

I've seen one tutorial on developing custom rom from source. To do that device specific files like kernel, device tree and vendor blobs are needed. I have following problems regarding those files.
* Kernel - I have zip file of kernel downloaded from my device manufacturer site. How can i make use of that to build a rom?
* device tree - I'm not able to find a device tree for my device anywhere (github or anywhere), how can I build device tree using (kernel/stockrom...)
I'm totally new for this so I don't know if it is even possible or not. Or Is there any other way to create device tree.
* vendor blobs - I've same problem for vendor blobs as in device tree.
~ so from where and how I can extract or create device tree and vendor?
~ and make things ready to develop a custom rom
My device is HTC one (m8 eye)
code name : melsuhl
I have not found any tutorial to build vendor tree but there is an outstanding tutorial on building device tree..
Check this out : https://youtu.be/Uw_caMHZRC4
hello @HarshOne i am looking for the same things as you. Trying to build a lineageOS ROM for my cph2025 OPPO Find X2 Pro. Did you find a way to find those trees?

Need help with errors when compiling kernel from source.

So, I recently got a ASUS Zenfone 4 Selfie Pro, the phone is stuck on android 7.1 and doesn't have any roms, nothing, just TWRP. So I'm on a journey trying to build stuff for this device from the ground up, I already made a device tree based on Zenfone 3 (which has the same SoC) and I tried to build lineage/cyanogenmod 14.1 for it and got a lot of kernel errors, so I went to try to compile the kernel from the source ASUS gave on their website and uploaded it to my github. In this past 3 days was able to fix and workaround some of the errors I got while building, but now I'm stuck on this one: https://hastebin.com/iqisuzegeg.coffeescript | any help would be greatly apreciated .
For easier access to the kernel source I uploaded it to my github and made some fixes/workarounds for some errors: https://github.com/2003Frost/android_kernel_asus_Z01M_stock
I'm using Linaro 7.5.0 as arm64 toolchain.
I'm using Zorin OS 15.2 as OS.
If any more information is needed I'll be glad to give out.
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Seppppx said:
Hmm. There is probably no definition for 'drivers/platform' and 'drivers/platform/msm' . But there is a reference (probably). Also have you tried to build the kernel with the defconfig "the manual way". If there is something wrong with the kernel I have almost no way of helping you because I'm not a real developer.
EDIT : There is a kernel source for your phone that on a developer's github https://github.com/shakalaca/android_kernel_asus_zd552kl . That is also the person who is the maintainer for official twrp. He has some large commits on the kernel so his kernel should build.
Click to expand...
Click to collapse
I already tried his kernel and got the same exact error :/
I didn't understand fully what you said with "the manual way" but I'm trying to compile the kernel outside the rom build environment, by using my device's defconfig and compiling with linaro.
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Seppppx said:
By the manual way I mean the with the defconfig. Also I made a pull request to your Device Tree (adds persist partition and Shakalaca's kernel).
Also if you're trying to build with defconfig there is a tutorial by google. https://source.android.com/setup/build/building-kernels-deprecated .
After that you will have to put it to the boot image. Another guide for that. https://source.android.com/setup/build/building-kernels#embedding-into-Android .
Edit : Isn't the Android kernel build with the defconfig when you run a source build? I think it actually builds the kernel when you build android so you don't build the kernel separately.
Click to expand...
Click to collapse
I accepted your pull request. Yes when you build a rom from source it also compiles the kernel, but I wasn't able to build the rom because it gave me kernel errors, so I went and started compiling separately because it's easier to fix kernel errors like this.
I am not using Google's tutorial, I'm following one that has almost the same steps and I'm using the same toolchain.
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Seppppx said:
By toolchain you mean tools that you need to compile a kernel? Why doesn't one just install the tools needed to compile a kernel source.
The guide I linked doesn't specify any toolchain (thus idk if I need one). It also doesn't have anything to do with build.sh script used to compile a kernel. Instead it uses the defconfig. The commands are actually very simple.
cd kernel-source_code
export ARCH=arm64
export CROSS_COMPILE=aarch64-linux-android-
make ZD552KL-Phoenix_defconfig
make
Also have you tried to build another kernel that you are sure builds? If another kernel builds. The issues have to do something with the kernel itself. If it does not it's most likely something else.
Click to expand...
Click to collapse
To compile a kernel from source you need something a cross compiler or toolchain in my case I'm actually using the exact same commands you commented with linaro toolchain/cross compiler (aarch64-linux-android). As far as I know you need that to compile a kernel and I don't think the toolchain is the problem but the kernel itself. I can try another kernel later to see if it compiles.
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Seppppx said:
Okay thanks!
If you manage to compile the kernel for your device make sure to mention/quote me. I would like to contribute. I'm on my way to make another pull request (now about cameras).
Click to expand...
Click to collapse
If you want to talk to me more quickly you can message me on telegram https://t.me/Frost_2003
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what software/packages do you need to get a specific device working from AOSP stock

hello again peeps,
ive been gently banging my head around these past few days because i keep walking into knowledge pockets and nothing i can find, in the form of help or internet information, is filling in these holes. i originally planned to take my oneplus device and obtain the source code for oxygenos so i could build and customise it. this seems to have become a dead end so now i just want to build stock android via AOSP, but i dont understand what software i need to get the AOSP working on any device, so far i understand that you need 3 components; 1) Kernel 2) Vendor files (if any) 3) "Proprietary binaries".
The problems are, i have no idea how to obtain these "proprietary binaries", i have no idea where to put any 3 of them in the downloaded android source tree (after repo sync), and i dont know if thats all the information i need to atleast build and flash a stock image onto any phone. i think i have the kernel files i need on OnePlusOSS github and there is a vendor.img in the OTA update files, and a directory in my phone. if anybody could please guide me in the right direction, it'd be very cool. i just want to get started and have some fun.
0
Seppppx said:
You can't customize Oxygen Os as the source code doesn't exist for that. (It's not required for companies to publish that.)
What phone do you have? You already might have the required trees to build AOSP (or at least LineageOS)
You need
1. A Device Tree
2. The kernel (you can use the prebuilt kernel if you really want)
3. The proprietary vendor blobs located in the vendor partition.
You will probably have to download the aosp-caf source code instead of aosp for it to be more easy.
https://www.youtube.com/channel/UCnGqG_jyyXmTzdamBpKfeHA
This is a great channel about Android building and has about everything you need to know.
Click to expand...
Click to collapse
thank you for every inch of text in your reply. I have a oneplus 8. Ah right, so the vendor folder CONTAINS the proprietary binaries/blobs.
it seems safest for me to use the kernel in the manufacturers github for the first flash as i want to be careful with making changes. may i ask what "aosp-caf" is? or can i find out using the resource you provided? thank you again.
my new understanding is, you need; 1) android source (e.g android-10-r5) 2) kernel 3) proprietary blobs. this helps a lot and is a lot clearer. the last issue i have is with knowing where to put the kernel and the blobs. i think if i am not mistaken you put the blobs in a vendor folder after the build? i am unsure with the kernel. i am going to definitely check this guy out. your time means a lot to me.

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