__cpufreq_cooling_register(9)

💅 __cpufreq_cooling_register(9) 💅

okay bestie, so this is a kernel API manual page, and we're gonna get into it — no cap, this whole thing lives in the Kernel API Manual and it's literally the blueprint for making a cpufreq cooling device. let's go 🫶

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✨ NAME ✨

__cpufreq_cooling_register — it's the helper function to create a cpufreq cooling device 🎀 like, that's literally its whole job and it ate

✨ SYNOPSIS ✨

struct thermal_cooling_device * __cpufreq_cooling_register (struct
device_node *np , struct cpufreq_policy *policy , struct em_perf_domain
*em );

that's the signature, don't touch it, she's iconic exactly as she is 💅

✨ ARGUMENTS ✨

• np — a valid struct device_node that points to the cooling device tree node 🌳 like yes bestie we're linking into the DT
• policy — the cpufreq policy. and ngl, normally this should be the same as cpufreq policy->related_cpus — like that's the vibe check it needs to pass
• em — the Energy Model of the cpufreq policy ⚡ it's giving power management realness

✨ DESCRIPTION ✨

okay so here's the moment, the main character energy of this whole page: this interface function registers the cpufreq cooling device with the name "cpufreq-s" 💖

and the way this API is so generous — it can support multiple instances of cpufreq cooling devices, like she's not gatekeeping, periodt 👑

it also gives you the opportunity to link the cooling device with a device tree node, in order to bind it via the thermal DT code 🦋 so yeah, that's the whole shebang and it's lowkey slay

✨ RETURN ✨

on success you get a valid struct thermal_cooling_device pointer — chef's kiss 🤌 and on failure, it returns a corresponding ERR_PTR 😭 so pls check that return value bestie, fr fr

⚠️ heads up: failure is not a vibe, it hands you back an ERR_PTR — always check!!

✨ SEE ALSO ✨

okay so this is the little friendship circle, the whole crew 🌈 — first up, the kernel file ./drivers/thermal/cpufreq_cooling.c, then all these faves:

• struct time_in_idle(9)
• struct cpufreq_cooling_device(9)
• get_level(9)
• get_load(9)
• get_dynamic_power(9)
• cpufreq_get_requested_power(9)
• cpufreq_state2power(9)
• cpufreq_power2state(9)
• cpufreq_get_max_state(9)
• cpufreq_get_cur_state(9)
• cpufreq_set_cur_state(9)
• cpufreq_cooling_register(9)
• of_cpufreq_cooling_register(9)
• cpufreq_cooling_unregister(9)

like that's the whole group chat, go say hi 💜

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and that's the page!! 🦋 this whole thing lives in ./drivers/thermal, dated October 2026, and it's part of the Kernel API Manual — signed, sealed, delivered, slay ✨💅🎀