Fair points,
I can send PR to make `hm2_modbus` more portable, we will see how that
goes. The deprecation period, if we agree it has to go, will start in
master, and will probably be carried in the 2.10 release, and removed on
master after release, so there will be sometime before it is gone from a
release. Documentation will reflect the decision once the proposal has
had time to mature. Users going version to version will get proper
warnings, and will be able to transition mostly pain free. For
documentation out of tree, it will get feedback, it will get fixed,
there will be new tutorials, there is time for all of that to happen,
once users follow an old tutorial and the warnings point them to
`hm2_modbus` that should happen naturally. I'm not saying tomorrow
`mesa_modbus` will be gone, I'm saying lets make sure `hm2_modbus` does
everything we need it to, and slowly turn the page on the old tool, if
most are on board...
*Luca Toniolo*
On 8/13/2026 4:46 PM, Zdeněk Z wrote:
Hi Luca,
Sorry for the confusion about the versions. I got confused by the fact that
both versions involve a compilation step. Of course, they compile different
things, but from my point of view as an integrator it is more or less the
same workflow: I have a configuration file, run a compiler, and get a file
that is then used by the driver.
I have now checked my setup again and I am indeed using the newer `hm2_
modbus` version with `mesambccc`, not the old `mesa_modbus`.
However, from my point of view I don't really see a benefit of `hm2_modbus`
over the old solution yet. It works for me, but I don't see a feature that
would make me prefer it over the old driver.
There is also one thing I don't like about the new version: the `mbccbs`
parameter requires an absolute path to the MBCCB file. The current
documentation explicitly says:
https://linuxcnc.org/docs/devel/html/en/man/man9/hm2_modbus.9.html
“The path should be an absolute path to prevent nasty surprises.”
For an integrator, having to put an absolute path into the INI file is
rather inconvenient. It makes configurations less portable, because moving
the LinuxCNC configuration directory to another machine or another user's
home directory requires changing the INI file as well.
There is another issue that may be worth considering before removing the old
driver. The old `mesa_modbus` method is still being actively presented to
users in tutorials. For example, this YouTube video demonstrates the old
approach:
https://www.youtube.com/watch?v=hCF-vei3s3M
The problem is not that the old method exists in a tutorial, but that it
isn't obvious to a user that this is now the deprecated method. Someone
following that tutorial can quite reasonably end up building a new
configuration with `mesa_modbus` without realizing that there is already a
newer replacement.
So I think that if the plan is to deprecate and eventually remove `mesa_
modbus`, it would be useful to make the migration path much more visible in
the documentation and tutorials.
In my particular case, though, I am already using `hm2_modbus`, so there is
nothing I need to migrate. I just don't currently see a practical advantage
of the new system from the integrator's perspective.
Zdeněk
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