Comparison between Raspian 12 Bookworm on Raspberry Pi 4 and Raspberry Pi 5

I have the official version of Debian 12 installed on my PI4, and I use it with my Mesa 7c81, the only problem is that for some reason the SPI port is disabled from the kernel and therefore it is not possible to write a new firmware to that card . Is there a Debian 12 kernel used on the PI4 that has the SPI port enabled by default? . As the official version of the LCN page does not depend on RASPBIAN, it is not possible to enable it with raspi-config or by modifying the config file.

The Linuxcnx version uses the raspbian kernel sources, so it is possible to enable the SPI interface on the RP4. The config.txt file is not in the same location as on a raspbian install, it's still under a sub directory of boot.
The raspbian kernel is patched to allow loading of overlays, the mainline is not.
Modify your config.txt file, reboot and look under the /dev folder for spidev.xx files and they will be there.
I've used rod images and made my own images using the same tools,for testing a diy mesa 7c81 and know that it does work.

We made sure that SPI did work, at least on the RPi4, the RPi5 is a different kettle of fish.

That's the problem, the config file is not in the /boot folder. I created a new one with the SPI=on instruction and it doesn't even work. I don't know if this config file is not in /boot but in another subdirectory.

The config.txt is not directly under boot, its there you'll have to look you don't need to create one. Have a look under /boot/broadcom

Thank you very much for this work. I have tried X times to compile kernels without ever succeeding.

thanks again for your work