STRUCT FF_PERIODIC_EFFECT(9)

💖 struct ff_periodic_effect(9) 💖

okay bestie, so this one's from the Kernel API Manual and it's literally the blueprint for a periodic force-feedback effect — like, the rumble that goes brrrr in a wave pattern instead of just one sad little buzz 🌀✨

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🌸 SYNOPSIS 🌸

here's the struct, exactly as it lives, no cap:

struct ff_periodic_effect {
    __u16 waveform;
    __u16 period;
    __s16 magnitude;
    __s16 offset;
    __u16 phase;
    struct ff_envelope envelope;
    __u32 custom_len;
    __s16 __user *custom_data;
 };

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🎀 Members 🎀

• waveform — what kind of effect this is (the wave). the vibe selector, basically 👑
• period — how long one cycle of the wave takes, in ms
• magnitude — the peak value, i.e. how hard it goes 🔥
• offset — the mean value of the wave (roughly). yes, roughly, they said it not me 🙈
• phase — (that's it, that's the whole description in the original, she's mysterious, main character energy fr)
• envelope — envelope data 🎀
• custom_len — number of samples (FF_CUSTOM only)
• custom_data — buffer of samples (FF_CUSTOM only)

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💅 Description 💅

the known waveforms are: FF_SQUARE, FF_TRIANGLE, FF_SINE, FF_SAW_UP, FF_SAW_DOWN, FF_CUSTOM. iconic lineup, honestly 🌈

heads up though — the exact syntax of FF_CUSTOM is undefined for the time being, because no driver supports it yet. so don't go building your whole personality around it, bestie, it's giving "coming soon" 💀

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✨ Note ✨

the data pointed to by custom_data gets copied by the driver. which means — and this is the slay part — you can totally dispose of that memory after the upload/update 🫶 no lingering attachments, we love a clean breakup.

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🦋 SEE ALSO 🦋

• Kernel file ./include/uapi/linux/input.h
• struct input_absinfo(9)
• struct input_keymap_entry(9)
• EVIOCGMTSLOTS(9)
• EVIOCGMASK(9)
• EVIOCSMASK(9)
• struct ff_replay(9)
• struct ff_trigger(9)
• struct ff_envelope(9)
• struct ff_constant_effect(9)
• struct ff_ramp_effect(9)
• struct ff_condition_effect(9)
• struct ff_rumble_effect(9)
• struct ff_haptic_effect(9)
• struct ff_effect(9)

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and that's the whole page, bestie 💖 it lives in ./include/uapi/linux, the version is October 2026, and the title is struct ff_periodic_effect(9) — go forth and make things vibrate on purpose 🎀✨🦋