em_dev_regis...pd_no_update(9)

📦 version 7.3.1, in nixpkgs unstable

💖 em_dev_register_pd_no_update — bestie, let's talk perf domains ✨

Okay so real talk: you're reading the em_dev_regis...pd_no_update(9) page from the Kernel API Manual, section 9, and honestly? This one is a little niche but it slaps. It's the chill cousin of the regular perf-domain registration — the one that doesn't go touching CPU capacities behind your back. 🫶

✨ SYNOPSIS ✨

int em_dev_register_pd_no_update (struct device *dev , unsigned int
nr_states , const struct em_data_callback *cb , const cpumask_t *cpus ,
bool microwatts );

That's the whole signature, no cap. It returns an int, and yes you should check it. 👑

🌸 ARGUMENTS 🌸

  • dev — the device you're registering the PD for. Like, the main character of this whole operation. 🎀
  • nr_states — how many performance states live inside your shiny new PD. Count 'em, bestie.
  • cb — the callback functions that populate the energy model. This is where you tell the kernel what the vibes (power numbers) actually are. ✨
  • cpus — the CPUs to include in the new PD. Mandatory if dev is a CPU device — like, do not skip this one, fr fr. 💅
  • microwatts — a bool that says whether or not the power values in the EM will be in uW. Lowkey important for your units. 🌈

🦋 DESCRIPTION 🦋

So here's the tea: this function is basically em_dev_register_perf_domain, except it does not trigger a CPU capacity update after registering the PD — even if dev is a CPU device. That's the entire personality. No sneaky capacity changes, just registration and go. 💜

If you wanted the capacity update to happen, this is not the function for you, bestie. Go read the sibling page.

👑 SEE ALSO 👑

Everything lives in the kernel file ./kernel/power/energy_model.c, and while you're there, go say hi to all these icons:

Kernel source location: ./kernel/power · Dated October 2026 · Section 9, Kernel API Manual

That's the whole page, bestie — go register some perf domains responsibly. Periodt. 💅✨🎀

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