tracing_map_add_var(9)

✨ tracing_map_add_var — Kernel API Manual (section 9) ✨

okay bestie, so this is the tracing_map_add_var page from the Kernel API Manual, and it's honestly one of the shorter ones so we can absolutely get through it together. It's a kernel function, it lives in ./kernel/trace, and it's about adding a var to a tracing_map. Let's go 🫶

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🌸 NAME 🌸

tracing_map_add_var — the one that adds a field describing a tracing_map var 💫

🎀 SYNOPSIS 🎀

int tracing_map_add_var (struct tracing_map *map );

🦋 ARGUMENTS 🦋

• map — the tracing_map in question. literally just the map, she's the main character here 👑

💖 DESCRIPTION 💖

So what this does is: it adds a var to the map, and then it returns the index that identifies that var in the map and in the associated tracing_map_elts. That index is not just a little souvenir — you actually need it. It's the index you use, for instance, to update a var for one particular tracing_map_elt via tracing_map_update_var, or to read that var back via tracing_map_read_var. iykyk 🔥

⭐ RETURN ⭐

The index identifying the var in the map and its associated tracing_map_elts — or -EINVAL on error 🙈

no cap: if it hands you back -EINVAL, that's the error path, not a real index. don't go indexing anything with it bestie 😭

🌈 SEE ALSO 🌈

Kernel file ./kernel/trace/tracing_map.c — and honestly the whole tracing_map friend group shows up here:

• tracing_map_update_sum(9)
• tracing_map_read_sum(9)
• tracing_map_set_var(9)
• tracing_map_var_set(9)
• tracing_map_read_var(9)
• tracing_map_read_var_once(9)
• tracing_map_add_sum_field(9)
• tracing_map_add_key_field(9)
• tracing_map_insert(9)
• tracing_map_lookup(9)
• tracing_map_destroy(9)
• tracing_map_clear(9)
• tracing_map_create(9)
• tracing_map_init(9)
• tracing_map_destroy_sort_entries(9)
• tracing_map_sort_entries(9)

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💅 and that's the whole page, bestie. sign-off time: this one's from the ./kernel/trace corner of the world, Kernel API Manual edition, dated October 2026 — go forth and index your vars responsibly 🎀✨💜