Real-time kerel not detected on patched 6.12

Does this patch allow you to select fully preemptible kernel, when configuring the kernel ?

From my experience building with the mainline rt "patch" it was required to edit kconfig under arch. Otherwise there were only 3 options for RT kernel, which didn't include the fully preemptible option.

Cant do this anymore bye all wrote:

Does this patch allow you to select fully preemptible kernel, when configuring the kernel ?

From my experience building with the mainline rt "patch" it was required to edit kconfig under arch. Otherwise there were only 3 options for RT kernel, which didn't include the fully preemptible option.
 

From 6.12 you don't need to apply a patch to build fully preemptible anymore. The patch only puts pack the indicator "/sys/kernel/realtime" which LinuxCNC checks to see if the kernel is real time. It might be that you need to enable EXPERT in the menuconfig to make the fully preemptible option visible, but no need to edit the kconfig

I see a lot of talk regarding enabling expert, that’s a sub menu with quite a few options, non relating to enabling a fully preemptible kernel.
The mod to the kconfig is a switch, as far as I can see, that the platform is RT capable.

OK,
There still seems to be patches required for RT.
One does include the above mentioned patch and the other does touch on what I mentioned but this depends of KVM being disabled.
So I would guess that the patches here:
www.kernel.org/pub/linux/kernel/projects/rt/6.12/
Would be correct for 6.12.8 ?

Which include the patch that allows Linuxcnc to detect a RT kernel and also allows the selection of a fully preemtible kernel.

Cant do this anymore bye all wrote:

I see a lot of talk regarding enabling expert, that’s a sub menu with quite a few options, non relating to enabling a fully preemptible kernel.
The mod to the kconfig is a switch, as far as I can see, that the platform is RT capable.

As you can see in my previous post, I built the kernel without additional patches besides the one that adds the rt indicator and didn't need to edit the kconfig.
About preempt_rt:
 
 

Are we talking arm or amd64 ?

I'm talking about RPi platform.

ARM64 but the same applies for AMD64

Tip, in menuconfig press the "/" key and you can search for the option you need, to see the location, but also the dependings.

Edit: I think you're right about the kconfig edit to add rt support for arm, probably I used an old config as template where the ARCH_SUPPORTS_RT=y was already in. Still "Expert=y" also needs to be selected

Yeah I know that,but a good tip anyhow, I built my first kernel on a 486......pre 2000 lol

Having a look at the RT patches for 6.12 there's a bit of extra stuff for arm/arm64, the patch code you've referenced is included is included as well.

ATM I'm running thru rod's image builder to see if it all comes good.

Seems like "real time" being included in the mainline kernel, as reported by tech blogs isn't the full story, seems there is some patching required, otherwise I guess the patches wouldn't be up.

I feel it's getting a bit confuddling when you start to dig deeper and actually build a kernel.

Sorry to keep banging on about this.

It's kind of doubly confusing at my end, as I'm not really sure this whole cnc thing is for me.

Yeah a bit confusing indeed, actually I wasn't aware that these patches are available, at the beginning of 6.12 they weren't. One of them is indeed to add support for arm and also one to add the realtime indicator.

Then for now still applying those patches seems to be the best way to go

Cheers mate