dt_init_idle_driver(9)

🦋 dt_init_idle_driver(9) — the Kernel API Manual, bestie edition 🦋

okay so this is from the Kernel API Manual, section 9 (that's the kernel-internals girlies 💅), and it's all about dt_init_idle_driver. yes it's a mouthful, no we're not renaming it, the kernel does not take suggestions 💀

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✨ NAME ✨

dt_init_idle_driver — parse the DT idle states and initialize the idle driver states array. that's it, that's the whole vibe 🎀

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🌸 SYNOPSIS 🌸

int dt_init_idle_driver (struct cpuidle_driver *drv , const struct
of_device_id *matches , unsigned int start_idx );

literally three things go in. that's the whole function. slay.

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💖 ARGUMENTS 💖

• drv — pointer to the CPU idle driver that's getting initialized. she's the main character here, everything happens to her 🫶
• matches — the array of of_device_id match structures to search through for compatible idle state nodes. and listen, this part matters so read it twice: the data pointer for each valid struct of_device_id entry in the matches array must point to a function with this signature, the one that lines up with the CPUidle state enter function signature:

int (*)(struct cpuidle_device *dev, struct cpuidle_driver *drv, int
index);

like, that's not optional. that's the contract. no cap. 🔥

• start_idx — the first idle state index that's gonna be initialized. your starting point, your opening act ✨

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🧚 DESCRIPTION 🧚

so here's the function signature again, living its best life:

int (*)(struct cpuidle_device *dev, struct cpuidle_driver *drv, int
index);

and now the actual plot: if DT idle states are detected and they're valid, then the state count and the states array entries in the cpuidle driver get initialized accordingly — starting from index start_idx. 📍

that's the tea. detected + valid = initialized, from start_idx onward. not from zero, not from wherever, from start_idx. respect the offset bestie 💅

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👑 RETURN 👑

the number of valid DT idle states parsed 🎉 and if it goes wrong? <0 on failure. so basically negative means the vibe check failed 😭

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🌈 SEE ALSO 🌈

• Kernel file ./drivers/cpuidle/dt_idle_states.c — go read it, it's giving source-of-truth energy 📖

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mwah 💜 that's the whole page — brought to you by the ./drivers/cpuidle girlies, October 2026 edition, from the Kernel API Manual. go forth and initialize your idle states, i believe in you 🍓✨