homing a axis from a subroutine

You are making this hard for us by posting the same questions on several places, please don't.
Thank you.
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Back on topic
Andy mentioned several ways of dealing with a tool changer, there are even more ways, but you have to stop overthinking things and start testing things. That is the best advice i can give you after reading everything you wrote on this forum.
So, here is another way, if you have something like an Emco turret, that works the same way as you describe, use the emcochanger component from here:
forum.linuxcnc.org/25-classicladder/3948...ol-turret-unreliable
Get the ones at the bottom, edit the .comp file to reflect the sensors you have, compile with
sudo halcompile --install emcochanger.comp
Edit the hal file to reflect your hardware, save.
Add the emcochanger.hal entry to the ini file, add the loadrt emcochanger to the hal file, also addf emcochanger to servo period.

Ok then, use carousel component written by Andy and proposed by him on the other topic.