event_trigger_count(9)

📦 version 7.3.1, in nixpkgs unstable

💅 event_trigger_count(9) — from the Kernel API Manual, bestie 🎀

okay so picture this: you're deep in the kernel API manual (yes, that manual, the one from the 9 section, iykyk) and you land on event_trigger_count. It's the optional count function for event triggers, and honestly? It's giving "small but mighty." Let's get into it. ✨

🌸 NAME 🌸

event_trigger_count — the optional count function for event triggers 🫶

✨ SYNOPSIS ✨

bool event_trigger_count (struct event_trigger_data *data , struct
trace_buffer *buffer , void *rec , struct ring_buffer_event *event );

yeah that's the whole signature, no cap. four params, one bool coming back at you 💖

🦋 ARGUMENTS 🦋

okay bestie, here's who's who in this function call:

  • data — the trigger-specific data. it's your data, the trigger's own little bag of stuff 🎀
  • buffer — the ring buffer that the event is being written to. that's where the action's happening ✨
  • rec — the trace entry for the event. heads up: it's NULL for unconditional invocation 👀 (yes, literally NULL, not a vibe, an actual null)
  • event — the event meta data in the ring buffer. the meta of it all 🌈

💅 DESCRIPTION 💅

so here's the tea ☕ — if you've got a trigger that can take a count parameter and that count doesn't do anything special, you can just point its .count_func field at this function and call it a day. it's the "default outfit" of count functions, fr fr 👑

what does it actually do? it simply does a count down of the data->count field. that's it. that's the whole job. iconic, lowkey 🧚

and the logic is chef's kiss simple:

  • if data->count is greater than zero, it decrements it ⭐
  • it returns false if data->count is zero
  • otherwise it returns true ✅

so basically: zero means "nope, false," anything above zero gets ticked down one and you get a true back. that's the whole personality 💀

👑 SEE ALSO 👑

the kernel file lives at ./kernel/trace/trace_events_trigger.c — go say hi 🫶

and here's the whole friend group, all the sibling functions, not one of them skipped, periodt:

ngl bestie, if you remember nothing else: count goes down, zero returns false, everything else returns true. that's the vibe check and it passed 💯

mwah 💋 this lil page came from ./kernel/trace and it's dated October 2026 — that's the source and the date, folded in all cute at the end like a signature on a note. go read some more kernel API pages, you're doing amazing 🎀🦋💜

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