pwm_round_wa..._might_sleep(9)

📦 version 7.3.1, in nixpkgs unstable

✨ pwm_round_wa..._might_sleep(9) ✨

okay so real quick — this is a page straight out of the Kernel API Manual, and the star of the show is pwm_round_waveform_might_sleep. yes the title has an ellipsis in it, no that's not me being dramatic for once, that's just how it's abbreviated. 🎀

💖 NAME 💖

pwm_round_waveform_might_sleep — query hardware capabilities. Cannot be used in atomic context. periodt.

🦋 SYNOPSIS 🦋

int pwm_round_waveform_might_sleep (struct pwm_device *pwm , struct
pwm_waveform *wf );

🌸 ARGUMENTS 🌸

  • pwm — the PWM device, bestie. that's your gadget.
  • wf — the waveform that gets rounded, and also the output parameter. she does both jobs, we stan a multitasker. 💅

🌈 DESCRIPTION 🌈

so like, typically a given waveform cannot be implemented exactly by the hardware — think about it, sometimes the hardware only supports coarse period resolution, or it straight up has no duty_offset. it's giving limited, honestly. 😭

this function returns the waveform that's actually implemented if you pass wf to pwm_set_waveform_might_sleep right now.

but — and this is the important part, don't skip it — the world doesn't stop turning when you call it. so when you do:

pwm_round_waveform_might_sleep(mypwm, wf);
pwm_set_waveform_might_sleep(mypwm, wf, true);

that latter call might fail, lowkey. why? because an input clock could've changed its rate between these two calls, and then the waveform that pwm_round_waveform_might_sleep determined can't be implemented anymore. so close yet so far 💀

usually all values passed in wf are rounded down to the nearest possible value — in this order: period_length_ns, then duty_length_ns, then duty_offset_ns. order matters, iykyk. only if that isn't possible might a value grow. for a more formal description, go check the documentation for pwm_set_waveform_might_sleep. she explains it properly. 👑

⭐ RETURN ⭐

  • 0 on success 🫶
  • 1 if at least one value had to be rounded up (she had to grow, let her)
  • or a negative errno 🙈

🧚 CONTEXT 🧚

May sleep. that's it, that's the context. so like, don't be weird about it.

🔥 SEE ALSO 🔥

Kernel file ./drivers/pwm/core.c, plus the whole friend group:

and that's the whole page bestie 💜 this lil cutie lives in ./drivers/pwm and the version vibes are dated October 2026 — so yeah, she's from the future, main character energy fr fr. 🎀✨🦋

📦 where this page comes from