Thanks Johannes, keep growing up. I hope in the future you can make tutorial related to Virtualization/Hypervisor like KVM, XEN, Jailhouse....

I really appreciate your videos. Thank you for producing such informative content.

Hi, The BAR's are mapped to some 32-bit address right, Are there any possibilities to use/access those addresses? How?

This is the KZbin channel that I've been looking for!!

Hi Johannes, I keep getting operation not permitted when I try to load the dev_nr module. I am using sudo, and I tried as root. Still not permitted. The Major number is definitely not in use before I attempt insmod, but it does show up in /proc/devices after I attempt insmod even though insmod fails. I tried downgrading my version of raspian to buster which uses a kernel version nearer to the one you use, but get the same issue. edit0: if I pass 0 to register_chrdev as the major, it works, and dmesg tells me it chose major 0 and minor 237, but /proc/devices looks like it is saying 237 is the major. If I reboot, and check 237 and my_dev_nr not longer visible in /proc/devices, and try setting MYMAJOR to 237, then it still fails with operation not permitted. edit: I have no such problem with the hello world insmod edit2: I also posted to reddit (more detailed look here): www.reddit.com/r/linuxquestions/comments/1fdpuwn/requesting_help_with_a_baffling_kvm_chrdev/

I don't quite understand. Are there 2 types of DMA controllers? One inside PCI device (if device provides it) and another in CPU itself? And can I use any of them to copy data PCI <--> RAM or I have to rely on PCI device (to implement DMA inside) only?

Can you please let me know to get workshop discussion details?

Thanks! have a nice day!

whenever i try to do echo > 1 /dev/my_gpio_driver it doesnt change the value to 1 also there is an error shown in the kernel log as invalid input. can u help me with this?

Only just been watching this - useful pointer on how to get the cp2112 board LED to switch on / off as a way of verifying operation. Just a point of interest: you can use i2cdetect -r -y 'bus-number' to get a listing of addresses via the cp2112 adapter.

How feasible would it be to port an existing Linux driver that you have the source code for to an older windows version? More specifically, Windows 98? The reason I ask is that I am kind of into retro computers and retro gaming and some of the old graphics cards that work in windows 98 are becoming increasingly rare and pricey. So having a driver even for a low end modern graphics card for win 98 would be extremely helpful.

Using this approach, is it possible to pass data from kernel to user space? Replacing the button by a temperature sensor, I get the temperature as an int allocated in kernel space memory: is it possible to pass this int (or a copy of it) to a user space application and covert it into an int allocated in user space memory?

I just found that pwm_request and pwm_free is deprecated and it's not found in Kernel v.6.6. May I ask for a tutorial? I try to find tutorial but nothing comes to mind.

CK h tee cyoyp rhoczieiel niler

thoughts on plan9 arg macros? ARGBEGIN ARGEND etc

A gem in my suggestion list... LOVE IT!

Lopez Kenneth Lewis Amy Robinson Karen

Haha what are the odds that I started learning Ethernet and you dropped a series on this.. excellent. Keep going. A suggestion would be to improve audio quality as I can hear little even on full volume. Or maybe adjustments to mic gain levels would help Thanks

This is going to be a great tutorial series. Thanks!

I love this channel. There, i said it! You provide wonderful introduction to Linux development for new developers that his the perfect mark between beginner friendly yet still in depth

Which speeds do you plan to support?

Good idea 💡

Very cool stuff, especially looking forward to the project based stuff. I am trying to learn more about linux internals through projects as well, and so far I have created a basic linux kernel module on my own (a magic 8ball) but im trying to figure out some more advanced projects to work on to build my knowledge further. Any reccomendations?

será magnífico esta jornada... Grato por compartilhar conhecimento!

Excelente tutorial, thanks a lot!!!!

i love how relatable this video is! thank you for not pretending everything went smoothly, and being human. keep up the good work :)

Good video!! Can i know how did you increased the font size on the console? would be a great tip thanks

Hi , can u share the pins on which you connected the Seven segments on AT32U4 pro micro

Hello Johannes, facing a small issue. It says "Could not insert the module, operation not permitted" and in the kernel logs it says , read_write - Device number Major: 236, Minor: 0 was registered! Can not allocate GPIO 4. Edit: Imaged a Legacy OS, with old kernel version and the problem is resolved

cool video! i cant help but notice you have a tab width of 8 spaces… wth.

hi, can you provide example of sending control transfer with data phase?

9:16 What exactly are you pointing to when you have the following path -C /lib/modules/$(shell uname -r)/build? I'm getting a "no such file or directory"

register_chardev() is pretty old way (for kernel version < 2.6 ) to register the device. This methode registers minor numbers 0-255 and sets up a default cdev for each.

Thank you, this was very helpful.

Hey, will I need any other hardware besides a raspberry PI to follow this series?

Great Content ! I am just wondering why you are using ioread8() instead of inb() as it seems to be a port mapped I/O.

One important feature of POSIX getopt is that when you pass to it argument '--' it will stop parsing arguments and set optind into next index after '--'. Also option arguments can be written in the same argument as the option expecting it, thus [ "-f" "file.txt" ] and [ "-ffile.txt" ] are the same. This can be exploited to introduce "long" options like "--help" or "--whatever-you-want=yes". We just need to specify '-' as option flag in getopt and specify that it expects an option argument. Since argument '--' alone will always be parsed first we still have the option to explicitly stop parsing arguments, but '--help' for example will be parsed as option '-' with optarg "help". Bingo, we have now long options! One caveat is that we can't specify "-:" at the begining of optstring since it can be interpreted by GNU versions as something else. Because of that you can put '?' as first character in optstring since it is not a valid option flag anyway and you should not try to use it because in the shell it will try glob files that look like '-a', '-A', '--', and so on.

When I try the command "./qemu-arm ../../busybox-1.36.1/busybox" I get the error: "qemu-arm: /home/thoup/kernel_hacking/busybox-1.36.1/busybox: Unable to find a guest_base to satisfy all guest address mapping requirements 00000000-ffffffff" I am running on an aarch64 linux system!

Not as good as the old AT&T System V standard. Sadly, even Unix has become bloatware.

Hey, Thanks brother for making its easier for us to understand this pcie driver

More people should use this instead of trying to come up with their own custom solutions.

Thanks Johannes for the wonderful explanation. Here why are you not using mmap() ? Is mmap() not possible here or you are trying out a different method ? Are these address space different from memory address space ?

HI! Can i replace the led in dc motor and control its speed?

Nice and to the point! I really appreciate your videos on demystifying Linux dev, thanks and keep up the good work!

you forgot to put the variable of %s for the first printf but how did it print the app name in default case?

Finally started with driver development, thanks Johannes, you make concepts easily understandable!

1st off all Thank You for this Informative video series. Please explain why calculation of the offset is required @11:27 ? In Kernel module also is it required ?

Excellent, as usual.... One objection: AT the figure @3:10, CPU is drawn as the head of the PCI tree. AFAIK this is not correct, as the cpu does not have PCI pins. Cpu connects to MCH, and IOCH, and these have PCI pins..

The keyboard resembles me of a chopper rumbling in the background.

How you are accessing 7 segment display with only 5 output pin ?