You already have can0 or vcan0 up and working, can-utils downloaded and compiled to ~/can/can-utils and you can send and receive frames without problems. However, when you want to bring up can-j1939 you get error like this:
avra@vm-debian:~/can/can-utils$ sudo modprobe can-j1939
modprobe: FATAL: Module can-j1939 not found in directory /lib/modules/5.7.0.0.bpo.2-amd64and also this:
avra@vm-debian:~/can/can-utils$ testj1939
testj1939: socket(j1939): Protocol not supportedAbove errors mean that can-j1939 was not enabled in your kernel and you need to compile it manually. There are several ways to do it. Any Linux kernel since 5.4 has can-j1939 module, but you will probably want to install fresher version, which leads to downloading kernel sources, enabling can-j1939 module, recompiling kernel and installing it. I will be using Debian 10.5 x64 (buster testing) virtual machine.
We will download Debian patched kernel 5.8. First update your sources
avra@vm-debian:~$ sudo apt update
and then look at available Debian patched kernel source packages
avra@vm-debian:~$ apt-cache search linux-source
linux-source-4.19 - Linux kernel source for version 4.19 with Debian patches
linux-source - Linux kernel source (meta-package)
linux-source-5.4 - Linux kernel source for version 5.4 with Debian patches
linux-source-5.5 - Linux kernel source for version 5.5 with Debian patches
linux-source-5.6 - Linux kernel source for version 5.6 with Debian patches
linux-source-5.7 - Linux kernel source for version 5.7 with Debian patches
linux-source-5.8 - Linux kernel source for version 5.8 with Debian patches
If kernel 5.8 does not show in your linux-sources list (it shows above in mine since I have already upgraded stock 4.19 kernel to backported 5.7), then you will need to add backports to your sources list. It is best to do it like this
echo 'deb http://deb.debian.org/debian buster-backports main contrib' | sudo tee -a /etc/apt/sources.list.d/debian-backports.list
Alternatively, or in case you have problems with installation of some packages, or you just want to have everything in a single list, here is what my /etc/apt/sources.list looks like (you will need to append at least last line to yours)
deb http://security.debian.org/debian-security buster/updates main contrib
deb-src http://security.debian.org/debian-security buster/updates main contrib
deb http://deb.debian.org/debian/ buster main contrib non-free
deb-src http://deb.debian.org/debian/ buster main contrib non-free
deb http://deb.debian.org/debian buster-backports main contrib
After adding backports in one way or another, try sudo apt update again, and after that apt-cache search linux-source should show kernel 5.8 in the list, so you can install it's source package
sudo apt install linux-source-5.8
and unpack it
avra@vm-debian:~$ cd /usr/src
avra@vm-debian:/usr/src$ sudo tar -xaf linux-source-5.8.tar.xz
avra@vm-debian:/usr/src$ cd linux-source-5.8
First we need some packages for menuconfig
sudo apt-get install libncurses5 libncurses5-dev
copy and use our old configuration to run menuconfig
avra@vm-debian:/usr/src/linux-source-5.8$ sudo cp /boot/config-$(uname -r) .config
avra@vm-debian:/usr/src/linux-source-5.8$ sudo make menuconfig
where we enable SAE J1939 kernel module as shown
- Networking Support
- Can bus subsystem support
- <M> SAE J1939
Now edit /usr/src/linux-source-5.8/.config, find CONFIG_SYSTEM_TRUSTED_KEYS, change it as following
CONFIG_SYSTEM_TRUSTED_KEYS=""
and save the file.
We will have to download necessary packages
sudo apt install build-essential libssl-dev libelf-dev bison flex
compile kernel (using threads to make it faster)
avra@vm-debian:/usr/src/linux-source-5.8$ sudo make -j $(nproc)
install
avra@vm-debian:/usr/src/linux-source-5.8$ sudo make modules_install
avra@vm-debian:/usr/src/linux-source-5.8$ sudo make install
and update grub
avra@vm-debian:/usr/src/linux-source-5.8$ sudo update-grub
avra@vm-debian:/usr/src/linux-source-5.8$ sudo reboot
Check if installation is correct with
sudo modprobe can-j1939
and if you get no error then you can enjoy can-j1939. If you get some error then you might check if this alternative command works:
sudo insmod /lib/modules/5.8.10/kernel/net/can/j1939/can-j1939.ko
If it does then all you need to do is
sudo depmod -av
reboot once, and modprobe command from the above should finally work.
You might have a problem with headers not being updated. To check that open file /usr/include/linux/can.h with
nano /usr/include/linux/can.h
If in the struct sockaddr_can you don’t see j1939, then header files did not upgrade and you need to do it manually
sudo cp /usr/src/linux-source-5.8/include/uapi/linux/can.h /usr/include/linux/can.h
sudo cp /usr/src/linux-source-5.8/include/uapi/linux/can/j1939.h /usr/include/linux/can/
That is the minimum for compiling some J1939 C code, but you might want to upgrade other header files as well. That's up to you. Enjoy!