Let's code a Linux Driver: 1: A minimal Hello World Linux Kernel Module

[@jholloway77]

Oh hells yeah!!! I've decided to not only do these projects on a linux box, but to recreate each of the drivers you make on a FreeBSD machine. That way not only will I learn in a more hands on way, but I can compare and contrast the different *nix systems

[@ExplosiveAnyThing]

I am really excited about the new series. I followed the old one but I am very hyped for this and I will definitely follow this one as well! Thank you very much for this!

[@sergiogcollado]

First comment? Thanks for the video Johanes! ❤

[@rodrigoolmos9202]

So good video dude 😊

[@cat_dev_random]

This video series came at a great time! I'm looking at writing a custom tty line-discipline module that extends n_tty, so I can do ^K (ctrl+k) to send SIGKILL just like ^C (ctrl+c) sends SIGINT Partially an exercise, but at the same time useful

[@ΝίκοςΙστοσελίδα]

The first of the updated videos? Congrats!

[@johannes4gnu_linux96]

Yes, the first of the new ones. More are coming :)

[@ΝίκοςΙστοσελίδα]

@@johannes4gnu_linux96 Just one question, does the old video about installing the necessary tools still hold with updated versions, or did I miss a video?

[@johannes4gnu_linux96]

@@ΝίκοςΙστοσελίδα This video is still valid for setting up everything on Raspberry Pi OS: kzbin.info/www/bejne/iHvVYZZqmdV-rqs

[@adedayoeniola2118]

Welldone Johannes, this is so much better

[@fluctura]

Nice, thank you! I remember fixing a sound driver for Linux 2.4 in 2003 or so.. was fun. I since moved on to macOS but it's nice to see the modern Linux way -- it's EXACTLY like it used to be 20 years ago haha -- schöne Grüße.. und aufpassen.. deine Website hat kein Impressum..

[@anthony2623]

its great you are using Raspberry pi for your kernel module. It's a common board in my opinion

Well done. Thanks!

[@jamesross3939]

Liked and subscribed!

[@0x8F]

Great video! I noticed that I can do 'sudo rmmod hello' without specifying the .ko file, I guess that is using the running module name directly

[@johannes4gnu_linux96]

Yes, that is also possible. The module name of a loaded module or the path and filename of the module can be used to remove the module. We will dive into this a little bit more in the next video.

[@jeffinphilip3876]

How did you navigate to /build? There isn't even a file or directory named build when we see the ls command

[@nikolasemov2822]

PLS correct me if I am wrong but : Thats the command: cd /lib/modules/$(uname -r)/build . If you don't find it make sure that you have installed the kernel headers (sudo apt install raspberrypi-kernel-headers).

[@jeffinphilip3876]

I'm working on a x84 machine, FYI. Is something different for that configuration?

[@johannes4gnu_linux96]

Yes, thats correct.

[@johannes4gnu_linux96]

On an x86 machine the package name for the kernel headers is different. E.g. for debian based distros it should be linux-headers-$(uname -r)

[@Optmzdlyz]

Hey Johannes What would be the difference between using Static variable for the module init and exit functions vs not using one? We do not need them to retain their value after the driver is unloaded so we can just use int only?

[@johannes4gnu_linux96]

In the next video I explain it in more details. But basically static only reduces the visibility and linkage of the function. If I declare them static, they can only be used within the module.

[@Optmzdlyz]

@@johannes4gnu_linux96 Makes a lot of sense now, thanks a bunch :D

[@rohithkapse9090]

kernel headers installed proper version still not able to do make , its throws an make oldconfig && make prepare still that command is issue

[@johannes4gnu_linux96]

Ok, are you also using Raspberry Pi OS with the kernel headers installed? Can you give me the exact error message of make?

[@rishidivakar6865]

Hello, I have reached till compiling the ko file. But, when I enter the tmux command, I don't see another window like in this video where I can enter insmod command. Is there any other package I need to install?

[@rishidivakar6865]

I'm just a novice in Linux, please ignore my silly questions. Ctrl+b % will open a new pane

[@johannes4gnu_linux96]

@@rishidivakar6865 for a novice it is not a silly question. Maybe i should have mentioned it. Bit good to Here you find it out yourself 😉

[@nyeeesss2424]

Hi! Loved the tutorial. However, I'm getting the error: ""insmod: ERROR: could not insert module hello.ko: Invalid module format" Any help? I'm using PopOS

[@johannes4gnu_linux96]

Thank you. Hmm, maybe run modinfo hello.ko and uname -r to verify if you have build the module against the correct kernel version. If they match, maybe you have turned on secure boot and it only allows you to load signed modules. But that should be a different error message...

[@nyeeesss2424]

@@johannes4gnu_linux96 Hi! Thank you for your reply, I was trying to follow the tutorial with linux running in a VM. Maybe that was the issue, because I tried the same on my actual system and it ran perfectly. Once again love how easy you made it all seem!

[@ralify]

Btw are you using arch?

[@johannes4gnu_linux96]

Yes, I do

[@preetamdas4048]

yay