[TUT] Introduction into Kernel development - Motorola Droid RAZR

INTRODUCTION INTO KERNEL DEVELOPMENT
PREPARATION
This guide is NOT a full development tutorial! For development of kernels you should be familiar with C. I cannot teach you full C - would be too much for me - but I can show you how to prepare a build environment especially for RAZR Kexec Kernel building! At the end you will find some first steps about how to develop a kernel.
As soon as you have a full dev setup you will be motivated to proceed with learning C - hopefully
For me it worked!
The reason is that I would like to see more people giving it a shot! Kexec is wondeful and it would be great if there are some more people working on kernels.
Please leave me some credits if this tutorial helped you wherever you provide your work! THX!
OVERVIEW
1. Install Linux
2. Setup build environment
3. Initialize Kernel Source
3.1 Branches
3.2 How to compile a kernel
4. Create your first development branch (Add a new Governor)
5. Git Commands
I will tell you the way I started once and guide you through the preparation.
It's important to know how to setup a build environment! The best way to learn about kernel development is to learn by practice!
How to setup a build environment
1. INSTALL LINUX
I suggest Linux Mint 15 Cinnamon (or Linux Mint 15 Mate is good for older for low-spec Systems) - it's free and very easy to install near Windows 7 (dual boot). After the installation you will have a very Windows-like desktop environment which is easy to handle also for beginners. Then you need to learn the Linux Shell!
*of course you can install any other Linux, like Ubuntu. Linux Mint is based on Ubuntu 13.04 and I use it as well.
If your CPU supports 64 bit you should install the 64 bit version! This is impossible also later when it comes to install libraires for development, etc. There are mostly two versions, whether for x32 or x64.
After the installation of Linux you need to imstall related software and depencies.
2. SETUP BUILD ENVIRONMENT
Now, Linux is installed, we begin to setup the build environment.
First install Git which is the main part for using services like Github, etc..
We will install also adb and fastboot!
NOTE
The main installation command for packages in Linux is:
apt-get install (mostly used with 'sudo' ("superuser doers" - admin), then it will be:
sudo apt-get install package-name
You can combine one command to imnstall multiple packages, like:
sudo apt-get install package-name package-name ...
It doesn't matter how much names you enter!
NOTE: Sometimes you will have to confirm the installation of a specific package, means it will ask you for proceed (e.g.: ...this will take xx mb of space (J/n) ?).
Press "j" and enter in this case.
Click to expand...
Click to collapse
Let's start!
Open a shell (terminal) and type:
Code:
sudo apt-get install git android-tools-adb android-tools-fastboot
(you will have to enter your password. Keep in mind that you won't see any input when typing passwords in Linux!)
Now you have installed adb, fastboot and Git!
After this you need to create a working space which means you have to download the full Android source to be able to build your kernel later.
Still in Terminal make sure you're in your user root directory (just type "cd" to get back into your root dir). Now you have to create a new directory for Android sources. Therefor we use the "mkdir" command (make directory). We need to create a folder structure, so we create another folder inside of your new folder:
Code:
mkdir android
cd android
mkdir system
NOTE
This will create: /home/android/system
There is a simpler way to create a folder structure by using on single command. Just add a "-p" to the mkdir command to create multiple directories:
Code:
mkdir -p ~/android/system
NOTE
The "-p" lets you also create directories while being somewhere else!
The "~" symbol is a placeholder for your home folder! It tells the terminal that you want to create the folders in your "home" dir. For better understanding I'll show you the command w/o the placeholder again:
mkdir -p /home/android/system
Click to expand...
Click to collapse
Now you have install the depencies (libraires, etc, needed for compiling Android). So you are still in your terminal and type:
Code:
sudo apt-get install git-core gnupg flex bison gperf libsdl1.2-dev libesd0-dev libwxgtk2.8-dev squashfs-tools build-essential zip curl libncurses5-dev zlib1g-dev openjdk-6-jre openjdk-6-jdk pngcrush schedtool libxml2 libxml2-utils xsltproc
NOTE
These depencies are for 32 bit & 64 bit systems!!
Click to expand...
Click to collapse
Now we need some additional libs because we are using a 64 bit system. Still in terminal install them by using the apt-get command. I will only show you the package names now, so you can practice and see if you have understood it. Install these:
Code:
g++-multilib lib32z1-dev lib32ncurses5-dev lib32readline-gplv2-dev gcc-multilib
NOTE
You can simply use copy&paste
Click to expand...
Click to collapse
Next step is the creation of the repo base directory. It is needed by the repo software which lets you control and use the git repositories on your local machine (your computer). Use the "mkdir" command to create the following directory:
Code:
mkdir -p ~/bin
Now you have to install the "repo command". It's a binary file, so you have to make it "executable" (runable) by using the "chmod" command. Chmod is similar to the "set_perm("...")" command used by updater-scripts (EDIFY script language). It just sets the permissions of a file, i.e. to allow the execution of this file or to make sure the file can be accessed by any people or other programs.
Enter the following to download the "repo" binary and make it executable (runnable):
Code:
curl https://dl-ssl.google.com/dl/googlesource/git-repo/repo > ~/bin/repo
chmod a+x ~/bin/repo
NOTE
It would be too much to explaing stuff like "Curl", etc..
Click to expand...
Click to collapse
Now we have to make sure that we can call "repo" from anywhere. This means if you're in terminal in for example: $ /home/Downloads and you type "repo" it will tell you usually that "repo" is an unknown command. To avoid this we need to make it generic by adding "repo" to your static PATH (Path of execution). The command:
Code:
export PATH=${PATH}:~/bin
NOTE
if you set an "export" for anything (lkie repo) in your terminal, it will be gone as soon as you exit the terminal or also after a reboot. To keep it in your PATH forever you have to add the "export" to your bashrc file (this file stores your preferred Path commands, it's like a list where you can add whatever you need) to make this change to the path permanent for all future Terminal sessions:
Code:
gedit ~/.bashrc
This will launch a graphical text editor (if it doesn't work, try it with "sudo"). Just copy&paste the following line into it, save it and close:
Code:
export PATH=${PATH}:~/bin
Click to expand...
Click to collapse
Fine! So far we are prepared! Now we have to download the android source!
Still in terminal, type:
Code:
cd ~/android/system/
repo init -u git://github.com/CyanogenMod/android.git -b cm-10.2
NOTE
"repo init" initializes a repository oy your PC
the Git address is the link to the CM source code repo. YOu just told the computer that you just initialized a CM Git repo in the specifi folder /android/system
Click to expand...
Click to collapse
.
To start the download of all the source code to your computer:
Code:
repo sync
NOTE
This process can take a very long time - depends on your internet connection speed. The source is about 10 GB!!
"repo sync" will be your further command to keep the rpo up-to-date! Just enter it while being in the root dir of the android source (/android/system) at least once a day!
Click to expand...
Click to collapse
Now, when the download has been finished we have to download the prebuilt apps (like terminal emulator, etc):
Code:
cd ~/android/system/vendor/cm
then enter:
Code:
./get-prebuilts
Now there are the vendor files needed! There are two ways to do that: The "easy" way and - sometimes it doesn't work, then you have to use - the "harder" way.
The easy way:
Code:
source build/envsetup.sh
breakfast spyder
NOTE
this will usually download the vendor files (motorola speific device drivers). If you get an error message you have to use the second way (harder way).
Click to expand...
Click to collapse
Click to expand...
Click to collapse
The harder way:
cd to you vendor dir and clone the proprietary files manually:
Code:
cd ~/android/system/vendor
git clone https://github.com/Motorola-OMAP4-CM/proprietary_vendor_motorola.git -b cm-10.2
NOTE
"git clone" will be used always when you want to download a git repository to your computer, so you can work with it locally. e.g on Github.com there is always a clone URL given at the right side of the repo. Just type "git clone <link>" into the terminal to clone this repo.
Click to expand...
Click to collapse
Now open the file explorer (whether by using the mouse or in terminal: nautilus (maybe you you have to install this first) and head to /android/system/vendor.
You will find a folder called "proprietary_vendor_motorola".
Just rename it to "motorola".
NOTE
In the future, everytime you update your repo (repo sync) you will have to update the vendor repo too. Perform this by using "git remote update" command in terminal. Therefore you have to be in /android/system/vendor/motorola, and type:
Code:
git remote update
git pull
Click to expand...
Click to collapse
Congratulations! You have successfully setup your Android build environment!
Now we need the kernel source!
3. INITIALIZE KERNEL SOURCE
So you learned some basics about Git! Proof that you understand it and clone the kernel source repo to your PC! I'll give you the links but you have to clone it yourself! Use the clone URL you find at the following Github repo. Make sure you are NOT cloning into your Android source dir /android/system!)
The source for our 3.0.8 Kernel:
www.github.com/CyanogenMod/android_kernel_motorola_omap4-common
NOTE
Too hard? Let me help you (You can even copy&paste my stuff - but for real learning experience you should try to make it on your own)
Head into this dir:
Code:
cd ~/android
Clone the kernel source:
Code:
git clone https://github.com/CyanogenMod/android_kernel_motorola_omap4-common.git
The new folder will be: ~/android/android_kernel_motorola_omap4-common where your kernel source sits.
When done, you have successfully loaded the kernel source! Fine!
3.1 ---> BRANCHES
Now I am going explain you something about "branches" and how to use them!
A "branch" is a part of almost all git repos. It is very important and also very useful to work with branches!
A typical repository looks like that:
[CODE GIT REPO
|
master branch
/ \
/ \
branch: Test branch: Stable
\ /
\ /
\ /
MERGE changes[/CODE]
The repo contains mostly multiple branches. There is always the "master branch" (can have another name of course, branches can be named like you want) and some lower branches.
The "Master branch" is the main branch!
All other branches are custom and mainly used to test new code or sth else.
Let's say we have a kernel repo! This repo contains the JBX-Kernel. The master branch contains the current STABLE Version of the kernel. Now we want to implement a new feature. But when we use the master branch for development (which is sometimes an experiment) we could potentially break the kernel or its source and make it becoming unusable. Therefore we can use a different branch.
NOTE: A branch is always a copy of this branch where you are while creating a new branch! This means when I am currently in the JBX-Kernel master branch, and I create a new branch from there, then I will get a new branch which includes a full copy of my JBX-Kerne master branch. -- But I can work with it without being scared about breaking my repo!
Then many devs are using a "Merge branch". There we could in example copy all changes (which have been tested successfully before) together into a new branch. This process is called "merging".
Let's say we have finished our new feature inside of a test branch. Now the feature is ready to be built in into the Stable Kernel. Then we merge the test branch into the master branch. Thsi results in an updated master branch which now includes our new feature!
Another possibility to use branches can be found if you want to split our repo into different systems, such like the CM kernel source contains branches for CM10.1 and CM10.2. So there is a branch calld "cm-10.1" and another branch called "cm-10.2".
When you look at the part where we initalized the CM repo, you might notice that the repo URL includes this:
repo init -u git://github.com/CyanogenMod/android.git -b cm-10.2
The line marked with red in the URL points to a specific branch, the cm-10.2 branch.
Now we are still in the kernel source dir!
Because you want to build a 4.3 Kernel we need to be in the right branch for this! There are already branches exisiting in the kernel source (like explained above), it's splitted into different versions (4.2.2 and 4.3).
Still in terminal be sure you're inside your kernel source root dir (~/android/android_kernel_motorola_omap4-common), type:
Code:
git checkout cm-10.2
NOTE
"git checkout" is the command to switch to another branch. But it's also used to create or delete branches. More about that later...
Click to expand...
Click to collapse
The output in the terminal will tell you sth like: "Switched to branch cm-10.2"
(if it's the first time you enter a branch it will download the files first and tell you: "Switched to a new branch cm-10.2". Don't be confused by this. If you try to enter a non-existing branch it will give you an error).
Now you are in the kernel repo, in the 4.3 branch!
Before we start to play with the source code I will show you how to build a kernel! As long as the kernel source is untouched you can be sure that it will work! Also this will make sure you have done everything right so far - as soon as the kernel boots you've built!
3.2 HOW TO COMPILE A KERNEL
To get a first impression about how to build the kernel, please have a deeper look at my personal JBX build script:
https://github.com/RAZR-K-Devs/android_kernel_motorola_omap4-common/blob/JBX_4.3/build.sh
The script is very simple and contains only a few commands which can be used in the terminal as well. For your the script is only interesting until the poiont where it says: "make -j4 TARGET_KERNEL_SOURCE=/home/dtrail/android/android_kernel_motorola_omap4-common/ TARGET_KERNEL_CONFIG=mapphone_OCE_defconfig $OUT/boot.img"
Since the latest Android version and the modified kexec stuff it's not enough anymore to build the kernel only. The PVR source has been moved into the Android source and it must be built together with the kernel in order to get a working (booting) kernel! That's why I don't show you the common way.
In fact you can now build your kernel by taking my build script commands, and enter them - one by one - in your terminal. BUT you have to modify the paths because script was made for use on my computer (so, you probably are not called "dtrail!" ). You have to start in your kernel source dir (this is the location where my build script is being executed). To make it easier for you, I have pasted the script here and changed it so it will work for you. I have removed all comments and echo (output) commands so there are only the related build commands left. I just added comments just for you:
Code:
# THESE LINES (those beginning with #) ARE COMMENTS!!!
# Be in your kernel source: /android/android_kernel_motorola_omap4-common
# this command cleans all leftover files from prior compile (needed)
make mrproper
# We build the kernel and its modules
# enter the Android source dir
cd /android/system
# This command makes sure to use the additional build cache. It will make all fufutre build processes MUCH faster! (YOu have to install ccache first by using apt-get)
export USE_CCACHE=1
# Clean also the Android source dir
make mrproper
make ARCH=arm distclean
# Tell the compiler that we want to build now
source build/envsetup.sh
# Tell the compiler which device we want to build for
lunch cm_spyder-userdebug
# built kernel & modules (This command includes the full path to the kernel course and the used kernel config)
make -j4 TARGET_KERNEL_SOURCE=/home/YOUR_USERNAME_HERE/android/android_kernel_motorola_omap4-common/ TARGET_KERNEL_CONFIG=mapphone_mmi_defconfig $OUT/boot.img
After you entered this your computer will start building. The first compiling process will take longer! But future bui9lds will be built much faster thanks to the use of CCACHE!
CONGRATULATIONS!! You built your first kernel!!
Now we have to create a flashable zip file and flash the kernel to see if it works. >The advanced Linux users from you should have another look into my build script I linked above, there you can see how it automaticall pushes (copy) the fiules into a prepared folder which includes everything needed for a flashable zip and compresses it to a ready zip file!
Other less experienced users can just download my latest JBX-Kernel, unpack it, delete "logo.bin" and do this:
go to (by using mouse or terminal):
Code:
/android/system/out/target/product/spyder
There you will find a file called "kernel" - this is your fresh compiled kernel! Copy it to the unpacked JBX-Kernel folder, into:
Code:
.../JBX-Kernel_whatever.../system/etc/kexec
(and overwrite the previous kernel in there)
Now go to:
Code:
/android/system/out/target/product/spyder/system/lib/modules
There are all the modules you've just built. Copy them to:
Code:
.../JBX-Kernel_whatever.../system/lib/modules
Now compress the folders to a new zip file, copy it to your phone and flash it in recovery!
4. CREATE YOUR FIRST DEVELOPMENT BRANCH (add a new Governor)
to create a new branch locally, be in terminal inside the root of your kernel source, and type:
Code:
git checkout -b BRANCH_NAME
Replace BRANCH_NAME with whatever you want!
Now you created and switched to your new branch! Here you can start plaing with the files!
To develop Linux kernel (Android IS Linux!) you will have to learn C! The kernel is developed in pure C which is the best programming language for drivers (machine controlling).
if you're German I can suggest your the "open Book - C von A bis Z" (Galileo Computing, gratis).
Otherwiase just google for free C books or tutorials.
Take your time, this is not easy in the fist place - but as soon as you are more experienced you will find it more easy!
The best way to learn it is to read and browse others Kernel repos! You are always free to watch my JBX-Kernel Repo! Read the commit messages to see what this commit is for and look at the code-side changes! If you read carefully, and learn C at the same time, you will understand the commits, step by step.
Let me give you some more hints:
Set you some smaller goals and start to reach them one by one! Don't set yourself too high goals, otherwise you will make yourself too much pressure!
Small steps are the way to your success!
Some of you might only want to make some minor changes, such like adding new governors, etc. Therefor you can i.e. use google to find related commits. So open Google and type:
Code:
github kernel omap add governor
We hope that google will show us some repos where the dev(s) wrote commit messages like "Added XXX governor", etc, etc..
In this example Google will put out this:
https://www.google.com/search?q=github+kernel+omap+add+governor
If you click the link you will find the very first result, which leads us to:
https://github.com/broodplank/glass-omap-xrr02
There click on Commits and you will see a commit "Add SmartassV2 governor". Now open this commit, you will find this:
https://github.com/broodplank/glass-omap-xrr02/commit/f959e0e8c16412319e991b26aaa50d8fe3555a4e
There you can see now the FULL commit with all its details! It shows you exactly how to add a governor! The green parts are ALWAYS insertions on Github, while red parts are deletions! SO you can see exactly:
1. WHICH files have been changed
2. WHAT has been changed in these files
3. WHERE in the files were the changes made
4. HOW were these changes performed
Now, if you study this commit for a while, you might know what has to be done in order to add a new governor!
NOTE: The very long files which are COMPLETELY green are NEW FILES!
Let's say you want to take this SMartassV2 governor into your kernel:
You can do it with different ways.
1. Cherry-Pick
For this weay you have to add the "glass-omap-xrr02" repo as remote to your repo. So you get the clone URL and use the git remote command (in your kernel root dir with terminal):
Code:
git remote remove upstream
git remote add upstream https://github.com/broodplank/glass-omap-xrr02.git
Now we must fetch the repos content:
Code:
git fetch upstream
Wait until the fetching process is finished.
Now we need the SHA1 sum of the commits. You go to your browser and look at the commit. The SHA1 is a very large number you can find at the upper right.
In this case this is the SHA1 for the commit "add SmartassV2 governor":
Code:
f959e0e8c16412319e991b26aaa50d8fe3555a4e
So, we need to cherry-pick this commit by typing in the terminal:
Code:
git cherry-pick f959e0e8c16412319e991b26aaa50d8fe3555a4e
Now there are three possibilites! If you see a message about "...conflicts" then it didn't work correctly because your local kernel source files might be a little bit different than those from the remote repo. In this case you open these files with a text editor (gedit) and find the lines with the errors, they are looking like this:
Code:
<<<<< HEAD
..some code...
>>>>>> Add SmartassV2 governor
Compare the files to those in the remote commit in your browser qand correct the issues or just this:
Code:
git cherry-pick --abort
This reverts your cherry-pick and your files are clean and like they were before the cherry-pick!
YOu can add the governor manually by simply looking the remote commit in the browser and copy the green stuff into your local files. Make sure you insert the codes in the right places!!! When you copy it from the green parts you will have to remove EVERY SINGLE "+" at the beginninf of each line!
There is another view in github for files, called "RAW". This will shows the pure file - but also without green/red marks! But in case you add the SMartassV2 governor, you can just search for the keyword "smartass" in the raw view of the file and then copy all lines which are including "msartass" into your local files
The governor itself is a complete new file, so you canswitch to the raw view, right click --> select all --> copy. Then create as new file in the right location (/kernel_source_dir/drivers/cpufreq/cpufreq.c) with the same name like in the commit (cpufreq_smartassv2.c) and paste the whole code into it, save and close.
Don't forget the rest of the code in the other files!!
At last you have to insert the new governor into your kernel configuration! The kernel config is mostly a "defconfig" file!
ALl the related defconfigs we need are located in:
Code:
.../arch(arm/configs
The default defconfig for our RAZR is the:
Code:
mapphone_mmi_defconfig
The defconfig file inlcudedes everything which is built into the kernel later. If you search for keyword "GOV" you will see the other governos, like Hotplug, etc.. YOu can see how they are used in the defconfig file, so add your new governor the same way. This should be:
Code:
CONFIG_CPU_FREQ_GOV_SMARTASS2=y
# CPU_FREQ_DEFAULT_GOV_SMARTASS2 is not set
*The second line is for setting it as default governor.
Thats was it! Now make sure everything was done the right way, save and close all files. In terminal type:
Code:
git status
This shows you info about the current status. In this case it will show you the changed files and the new file(s) in red color.
Now you have to stage your commit:
Code:
git add .
Adds all new/changed/untracked files to the commit, then:
Code:
git commit -m "Added Smartassv2 governor"
Done! Your new commit is staged to the index and can be uploaded! (Uploading is not part of this at the moment! If you want to learn more about git, use Google)
Now repeat the compile process like you did already! See if your new governor is included and working.
For further learning it's a good way to proceed with learning C and read, compare and understand commits from other devs/repos.
Ok, guys! I hope you enjoy the guide and it's helpful for you! I will extend/fix/correct this time by time... for now I'm done!
5. GIT COMMANDS
Here are some basics about using git by Terminal:
git branch -D BRANCH_NAME - Delete a branch
git branch -b BRANCH_NAME - create a new branch (but don't switch to it)
git checkout -b BRANCH_NAME - create & switch to a new branch
git checkout BRANCH_NAME - switch to a exisitng branch
git push origin BRANCH_NAME - upload your changes to your repo on Github (You have to be in that branch you are also uploading to!)
git remote update - checks for the latest changes in the original repo (that one where you took the source)
git pull - after you used "git remote update" use "git pull" to download the changes to your computer
git diff BRANCH_NAME - shows differences between the current branch and any branch
git add . - Adds all your changed files to the index (this is important to upload your changes)
git commit -m "this is my commit message" - USe this after "git add ." to append a message to your changes, so other devs can
see why you did it, etc..
git log - Shows the commit history (the history of changes in this repo) inlcuding the related SHA1 for each commit
git revert SHA1 - this reverts (undo) one spedific commit. The SHA1 sum can be found near the commit messages (whether you
can look the with your browser or by us ing "git log")
git remote remove upstream - Removes the current upstream repository
git remote add upstream <git URL> - Adds a new upstream, useful if you want to take over changes from another repos/devs
git fetch upstream - get the new remote repo's content
git cherry-pick SHA1 - this picks one single commit from your current upstream repo - or from another branch
git cherry-pick --abort - This aborts your curerent cherry-pick, useful if you run into conflicts
Click to expand...
Click to collapse
If you find any mistakes or somethings missing in your mind, PM me or post it here.
Please leave me some credits if this tutorial helped you wherever you provide your work! THX!
CREDITS
*Cyanogenmod - took some single infos from their website
How to build Cyanogenmod for Droid Razr (website):
http://wiki.cyanogenmod.org/w/Build_for_spyder
*Hashcode - for being always helpful and supportive and of course for his great work with dhacker
*Linux, Google, XDA-DEVELOPERS

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-- reserved --

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Another reserver

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MINE

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Great write-up @dtrail1,
And I completely agree. I'm always hoping for more devs to jump into kernel development to learn and have fun with their devices.

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Deffinitely interested in this. Il be hitting this guide up soon as I pick a better internet provider for Repoing.

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Saving your book
Sent from my XT910 using xda app-developers app

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Thanks for the write up .
Sent from my XT912 using XDA Premium 4 mobile app

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Thanks. Perfect for youngsters like me
Sent from my XT910 using Tapatalk 2

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Corrected a typo where a .git extension was missing (and users might not be able to clone the repo without it)

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umts_spyder
Thank you dtrail1 for the great guide.
as XT910 owner, i guess that everywhere I see spyder in the code, I should replace it with umts_spyder ?

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tester5224 said:
Thank you dtrail1 for the great guide.
as XT910 owner, i guess that everywhere I see spyder in the code, I should replace it with umts_spyder ?
Click to expand...
Click to collapse
No, just use the SPYDER source - otherwise your kernel won't support LTE for the CDMA users. The LTE modules are only built with the SPYDER source, that's why we use it.
But you can repeat these steps with UMTS_SPYDER, it will only download the UMTS depencies then, so you are able to build CM10.2 for the XT910. For the kernel only use SPYDER source.

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dtrail1 said:
No, just use the SPYDER source - otherwise your kernel won't support LTE for the CDMA users. The LTE modules are only built with the SPYDER source, that's why we use it.
But you can repeat these steps with UMTS_SPYDER, it will only download the UMTS depencies then, so you are able to build CM10.2 for the XT910. For the kernel only use SPYDER source.
Click to expand...
Click to collapse
So if I understood correctly, the GSM\UMTS and LTE\CDMA are using the same kernel in CM ?
thanks for the reply

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tester5224 said:
So if I understood correctly, the GSM\UMTS and LTE\CDMA are using the same kernel in CM ?
thanks for the reply
Click to expand...
Click to collapse
If I understood it correctly in the normal cm there are two different kernels. One for gsm without LTE modules and one cdma with LTE modules. So in case want to build for both you need the cdma version as it has the LTE modules and so cdma users have LTE and as usually gsm users will have there normal network.
Sent from my XT910 using XDA Premium 4 mobile app

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Para94 said:
If I understood it correctly in the normal cm there are two different kernels. One for gsm without LTE modules and one cdma with LTE modules. So in case want to build for both you need the cdma version as it has the LTE modules and so cdma users have LTE and as usually gsm users will have there normal network.
Sent from my XT910 using XDA Premium 4 mobile app
Click to expand...
Click to collapse
No, the kernel has no differences! It's about the modules. The kernel is always the same but the mlodules are not. If you build the kernel with UMTS_SPYDER depencies you will get umts baseband modules only. But if you build it with the SPYDER source you will get a working modules for umts and cdma.

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:good: got it, thanks

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tester5224 said:
:good: got it, thanks
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It's special for our device. Usually it's enough to build the kernel only w/o using the full 15GB rom sources. But since 4.2.2 some parts of the kernel source were moved into the android rom source (e.g. the PVR (SGX) Sources), so we have to use the full rom source to build a working kernel - otherwise your kernel will cause a black screen on boot.

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@dtrail1 Question regarding the script you use to build the kernel.
Your script shows: make mrproper
When I run this command I receive an error message: make: *** No rule to make target 'mrproper'. Stop.
Do you have any advice on where I set the target?
Edit: After continuing with the remainder of the script the last error I receive is: make: *** Waiting for unfinished jobs....

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This command is needed to clean out the source directories. The error message is normal, just don't care about.
The second error you wrote about sounds like you tried to build without defconfig.
Make sure you have all related "export" commands AFTER the mrproper/distclean commands.
If you did so, then the error is caused by something else. Please post me the full last few lines of your terminal output, then I can tell you more.
Gesendet von meinem XT910 mit Tapatalk 4

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awesome guide brother. thank you. i ll give it a try today