[CAF] Kernel development newbie

[errikosd]

Hello to all. I hope someone can help me.

Background: I am a relatively experienced programmer. I have been programming with C/C++ (and other) in Linux for the last 6 years or so. However I have never dived in Linux Kernel development yet. So I would appreciate some help from anyone that can help me.

Goal: My goal is to learn more about Linux Kernel development. I want to start from my beloved G2, which is approaching its usage EOL. The device is fine, but I am planning on investing on a new one, so I will be able to squeeze it as much as I want.

I want to create a clean kernel for AOSP (CAF) based versions of Android. My vision is to start with a clean CAF base (without CM patches, etc) and bring it up-to-date till Linux 3.4.113 and manage it to boot. Then start backporting code, enhancements, etc. and making tests.

I searched in CAF repositories and I found them to be a mess. Can someone who is experienced with how things work point to the latest clean CAF source for msm8974?

I also want to hear anyone's thoughts on the attempt. Thanks ahead and regards.

 

[errikosd]

Maybe @GalaticStryder, you can give me some guidelines. Deeply appreciated.

 

[shaneel1491]

Hello to all. I hope someone can help me.

Background: I am a relatively experienced programmer. I have been programming with C/C++ (and other) in Linux for the last 6 years or so. However I have never dived in Linux Kernel development yet. So I would appreciate some help from anyone that can help me.

Goal: My goal is to learn more about Linux Kernel development. I want to start from my beloved G2, which is approaching its usage EOL. The device is fine, but I am planning on investing on a new one, so I will be able to squeeze it as much as I want.

I want to create a clean kernel for AOSP (CAF) based versions of Android. My vision is to start with a clean CAF base (without CM patches, etc) and bring it up-to-date till Linux 3.4.113 and manage it to boot. Then start backporting code, enhancements, etc. and making tests.

I searched in CAF repositories and I found them to be a mess. Can someone who is experienced with how things work point to the latest clean CAF source for msm8974?

I also want to hear anyone's thoughts on the attempt. Thanks ahead and regards.

I think the pure branch in GalaticStryder's Github is pure caf kernel, I don't think he added anything.

 

[errikosd]

I think the pure branch in GalaticStryder's Github is pure caf kernel, I don't think he added anything.

Unfortunately, I think that that branch does not exist anymore. Except if it is now called "marshmallow-caf".

 

[shaneel1491]

Unfortunately, I think that that branch does not exist anymore. Except if it is now called "marshmallow-caf".

It could be, not sure though.. I did download the source when he had it, I can zip and upload if you need?

Edit: nevermind, I forked his source a while back. Here https://github.com/shack-32/kernel_lge_msm8974/tree/pure
Also when I built it, as well as when he built, the mpdecision seems to be busted on boot, so the cores won't hotplug, you can enable it by looking in /sys directory and echo '1' for the mpdecision file.

 

[errikosd]

It could be, not sure though.. I did download the source when he had it, I can zip and upload if you need?

Edit: nevermind, I forked his source a while back. Here https://github.com/shack-32/kernel_lge_msm8974/tree/pure
Also when I built it, as well as when he built, the mpdecision seems to be busted on boot, so the cores won't hotplug, you can enable it by looking in /sys directory and echo '1' for the mpdecision file.

Thanks a lot! I believe this would be a good start.

I will try and pair it with anykernel packager and enable mpdecision on boot.

 

[shaneel1491]

Thanks a lot! I believe this would be a good start.

I will try and pair it with anykernel packager and enable mpdecision on boot.

Cool, good luck with it!

 

[GalaticStryder]

Well, I'd first need to explain some other stuff first before you get started

The CAF release for MSM8974 Kernel is oddly one of the no longer maintained ones: LA.BF.1.1.1.x.

To initialize a brand new clean Kernel you'd need to pull the CAF source code and copy the plain LGE Kernel code from the latest release they pushed which is if I'm not mistaken D80230F, then diff it to see what has got replaced and get it back, adapting the code manually on top of the recently merged LGE source code.
This would basically be the first step, then you'd head over to compilation fixes, create the scripts and the tools to bump the image and flash it to see if it boots.
To support more devices you'd need to merge the other variants as well from LGE source code and then do the same as before...

This doesn't make sense since you'd be getting an old Kernel from CAF and yet an older one from LGE. The little updates made on top of the first CyanogenMod 12.1 (CAF Kernel) were very basic and were caught already either by CM itself on their Kernel tree or mine.
Then you'd go forward to merging the kernel-common updates for 3.4.y coming from Google source code and then head over to update the base Linux Kernel version, fix compilation and such...

Since all this is done already, all you'd need is forking the Kernel at 3.4.110 and cherry-pick the selected changes you'd like up to 3.4.113 and compile using my scripts and all that...
The HEAD for that is c8bd789d12f8299db2e5a319abeb4a95df9078b6 and you're set to freely modify it the way you think should be done...

This is the lazy way of course but a great start...

 

[errikosd]

Well, I'd first need to explain some other stuff first before you get started

The CAF release for MSM8974 Kernel is oddly one of the no longer maintained ones: LA.BF.1.1.1.x.

To initialize a brand new clean Kernel you'd need to pull the CAF source code and copy the plain LGE Kernel code from the latest release they pushed which is if I'm not mistaken D80230F, then diff it to see what has got replaced and get it back, adapting the code manually on top of the recently merged LGE source code.
This would basically be the first step, then you'd head over to compilation fixes, create the scripts and the tools to bump the image and flash it to see if it boots.
To support more devices you'd need to merge the other variants as well from LGE source code and then do the same as before...

This doesn't make sense since you'd be getting an old Kernel from CAF and yet an older one from LGE. The little updates made on top of the first CyanogenMod 12.1 (CAF Kernel) were very basic and were caught already either by CM itself on their Kernel tree or mine.
Then you'd go forward to merging the kernel-common updates for 3.4.y coming from Google source code and then head over to update the base Linux Kernel version, fix compilation and such...

Since all this is done already, all you'd need is forking the Kernel at 3.4.110 and cherry-pick the selected changes you'd like up to 3.4.113 and compile using my scripts and all that...
The HEAD for that is c8bd789d12f8299db2e5a319abeb4a95df9078b6 and you're set to freely modify it the way you think should be done...

This is the lazy way of course but a great start...

So that HEAD has to be the cleanest "working" snapshot I can get, right?

Thanks a lot for outlining the procedure and giving me the boost I needed. It will be definitely easier to get started now.

 

[GalaticStryder]

So that HEAD has to be the cleanest "working" snapshot I can get, right?

Thanks a lot for outlining the procedure and giving me the boost I needed. It will be definitely easier to get started now.

Yes, it's pretty clean. Make sure you clean anykernel too.

 

[matteo0026]

There's a lot of work for developing kernels! I would like to learn how to do step by step, but i think i have a lot of things that i must learn before starting developing a kernel... As languages i'm learning C, but i don't know other...

 

[shaneel1491]

There's a lot of work for developing kernels! I would like to learn how to do step by step, but i think i have a lot of things that i must learn before starting developing a kernel... As languages i'm learning C, but i don't know other...

Building a kernel is not too hard, adding stuff is a bit tougher. You should start but simply downloading the source of a kernel already found on GitHub. There are various guides on xda that teach you how to build. Once you are comfortable with building you can go on to adding governors and many other tweaks, that's where commits come into play as it makes everything easier to add stuff.

This is a simple tutorial, try look for some more as well http://xdaforums.com/showthread.php?t=2152819

 

[matteo0026]

Building a kernel is not too hard, adding stuff is a bit tougher. You should start but simply downloading the source of a kernel already found on GitHub. There are various guides on xda that teach you how to build. Once you are comfortable with building you can go on to adding governors and many other tweaks, that's where commits come into play as it makes everything easier to add stuff.

This is a simple tutorial, try look for some more as well http://xdaforums.com/showthread.php?t=2152819

I'm yet blocked on one step of guide... i can't find only one file g2_blablabla.deconfig...

 

[shaneel1491]

I'm yet blocked on one step of guide... i can't find only one file g2_blablabla.deconfig...

It's not actually named blablabla, the defconfig directory is basically the insturctions to build for all the different devices, so it should be g2_d802.defconfig or something along those lines for D802, as long as it has your device name, for example when Dorimanx builds, his file would be (https://github.com/dorimanx/Dorimanx-LG-G2-D802-Kernel/tree/LG-STOCK-KK/arch/arm/configs) -> dorimanx_d802_defconfig

The defconfig file is found in /arch/arm/configs directory

 

[matteo0026]

It's not actually named blablabla, the defconfig directory is basically the insturctions to build for all the different devices, so it should be g2_d802.defconfig or something along those lines for D802, as long as it has your device name, for example when Dorimanx builds, his file would be (https://github.com/dorimanx/Dorimanx-LG-G2-D802-Kernel/tree/LG-STOCK-KK/arch/arm/configs) -> dorimanx_d802_defconfig

The defconfig file is found in /arch/arm/configs directory

Ok, then there isn't nothing of d802_something_deconfig
See this too

 

[shaneel1491]

Ok, then there isn't nothing of d802_something_deconfig
See this tooView attachment 3929508

Which repo did you download source from. You can use the d802 config one from my forked version of galatic's pure branch

https://github.com/shack-32/kernel_lge_msm8974/tree/pure/arch/arm/configs

Dori's config is named: dorimanx_d802_defconfig

 

[matteo0026]

Which repo did you download source from. You can use the d802 config one from my forked version of galatic's pure branch

https://github.com/shack-32/kernel_lge_msm8974/tree/pure/arch/arm/configs

Dori's config is named: dorimanx_d802_defconfig

Ok, maybe the problem is that i took full stock sources kernel from opensource.lge.com ... Then now i try to do the same thing with lambda sources...?

 

[shaneel1491]

Ok, maybe the problem is that i took full stock sources kernel from opensource.lge.com ... Then now i try to do the same thing with lambda sources...

Hmmm, as far as I know you might run into problems building LG provided ROM for an AOSP/CM rom, so if you follow the same process with caf kernel it should work.

 

[matteo0026]

Hmmm, as far as I know you might run into problems building LG provided ROM for an AOSP/CM rom, so if you follow the same process with caf kernel it should work.

Ok then must i take a CAF kernel? Can i take lambda kernel?

 

[shaneel1491]

Ok then must i take a CAF kernel? Can i take lambda kernel?

Either, lambda is a modified caf version