fsm_event(9)

💅 fsm_event(9) — the kernel API manual, bestie edition

okay so you found the fsm_event(9) page, iconic, welcome 💖 this is the little function that pokes a finite state machine and tells it "hey girl, something happened."

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✨ NAME ✨

fsm_event — emits an event to a finite state machine 🎀

✨ SYNOPSIS ✨

int fsm_event (fsm_instance *fi , int event , void *arg );

literally that's the whole signature, no cap. ✨

✨ ARGUMENTS ✨

• fi — pointer to the FSM that should receive the event 🫶 she's the one getting the news.
• event — the event to be delivered 📬 like a little group-chat message but for state machines.
• arg — a generic argument, passed to the action function 🎁 it just gets handed straight over, no questions asked.

✨ DESCRIPTION ✨

so here's the vibe: if an action function is defined for the current state/event combination, that function is called with the provided arguments. that's it. that's the whole plot 💅 the state machine checks "do I have a handler for this exact state + event combo?" and if yes, it runs it with the args you gave.

✨ RETURN ✨

• 0 — success, the action function was called 🔥 ate and left no crumbs.
• 1 — state/event out of range, or no action function defined 😭 so basically nothing got called.

✨ SEE ALSO ✨

the whole friend group, go say hi 👑:

• Kernel file ./drivers/s390/net/fsm.h
• init_fsm(9)
• kfree_fsm(9)
• fsm_newstate(9)
• fsm_getstate(9)
• fsm_getstate_str(9)
• fsm_settimer(9)
• fsm_deltimer(9)
• fsm_addtimer(9)
• fsm_modtimer(9)

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and that's the page, babe 🌈 this little gem lives in ./drivers/s390/net, dated October 2026, and it's the fsm_event(9) manual — so go forth, emit your events, and slay 💜🦋