coresight_timeout_action(9)

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

okay so picture this: you're in the coresight zone of the kernel, you poke a register, and now you're just... waiting for one specific bit to get its life together and flip. That's literally this whole function. It loops until a bit has changed to a specific register state, and it hits a callback after every single trial — yes, every one, we're checking in constantly, it's giving supportive bestie energy 🫶

No cap, it's a tiny little waiter function and it ate.

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✨ NAME ✨

coresight_timeout_action — loop until a bit has changed to a specific register state, with a callback after every trial. 💫

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🌸 SYNOPSIS 🌸

int coresight_timeout_action (struct csdev_access *csa , u32 offset , int position , int value , coresight_timeout_cb_t cb );

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🎀 ARGUMENTS 🎀

• csa — the coresight device access for the device. it's the VIP pass, the way in 🎟️
• offset — offset of the register from the base of the device. where the register lives relative to base, iykyk.
• position — the position of the bit of interest. the one main character bit we're all here for ⭐
• value — the value the bit should have. the glow-up we're waiting on.
• cb — call back after each trial. yes it's spelled "call back" in the docs, and yes it runs every single trial, not just at the end 🙈

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🔥 RETURN 🔥

It returns 0 as soon as the bit has taken the desired state, or -EAGAIN if TIMEOUT_US has elapsed — whichever happens first. fr fr, whoever gets there first wins, no waiting around for the other one. ⏰

lowkey important: the "whichever happens first" part is the whole vibe check. fast bit = 0, time runs out = -EAGAIN. periodt.

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🦋 SEE ALSO 🦋

Everything in the kernel file ./drivers/hwtracing/coresight/coresight-core.c:

• struct coresight_node(9)
• coresight_blocks_source(9)
• coresight_get_sink_by_id(9)
• coresight_get_ref(9)
• coresight_put_ref(9)
• _coresight_build_path(9)
• coresight_release_path(9)
• coresight_select_best_sink(9)
• coresight_find_sink(9)
• coresight_find_default_sink(9)
• coresight_clear_default_sink(9)

go read them, they're iconic too 👑

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okay that's the page!! 💜 it lives down in ./drivers/hwtracing/coresight, and this lil drop is dated October 2026 — mwah, sending you off with a kiss and a properly-timed bit flip 🍓✨