UI_DEV_SETUP(9)

✨ UI_DEV_SETUP ✨

okay so bestie, we're in the Kernel API Manual (section 9, the kernel-functions girlypop section 💅) and today's main character is UI_DEV_SETUP — the ioctl that sets up your input device's parameters before it exists. yes, before. it's giving "manifesting" ✨

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🌸 SYNOPSIS 🌸

UI_DEV_SETUP

that's it. that's the whole vibe. no cap.

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🎀 DESCRIPTION 🎀

so this ioctl sets the parameters for the input device you're about to create 🫶. it supersedes the old "struct uinput_user_dev" method — you know, the one that wrote this data via write. retiring an icon tbh 💀. but heads up: if you actually wanna set the absolute axes, you use UI_ABS_SETUP for that, not this one. iykyk.

The ioctl takes a "struct uinput_setup" object as its argument, and the fields of that object are, like, super important:

• id — see the description of "struct input_id". this field is copied unchanged into the new device. literally a copy-paste moment ✨
• name — this is used unchanged as the name for the new device. iconic name stays iconic 🎀
• ff_effects_max — this limits the max number of force-feedback effects. check below for the description of FF with uinput 👑

ngl this is the flexible one: this ioctl can be called multiple times and it will overwrite previous values 🔥. so if you fumbled the first call, no biggie, just run it again bestie.

⚠️ okay real talk — if this ioctl fails with -EINVAL, it's recommended that you use the old "uinput_user_dev" method via write as a fallback, just in case you're running on an old kernel that doesn't support this ioctl. think of it as the group-chat backup plan 💖

now the failure modes, because we respect the lore:

• -EINVAL — if it's not supported, or if you passed incorrect values 🙈
• -ENOMEM — if the kernel runs out of memory 😭
• -EFAULT — if the passed uinput_setup object cannot be read/written 💀

and the spicy warning: if this call fails, partial data may have already been applied to the internal device. so like... it's not a clean undo. be careful, bestie 🫶

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🦋 SEE ALSO 🦋

• the kernel file ./include/uapi/linux/uinput.h
• UI_ABS_SETUP(9)
• UI_GET_SYSNAME(9)
• UI_GET_VERSION(9)

go read them, they're all slaying in their own way 👑

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and that's the page!! 🌈 this lil gem lives under ./include/uapi/linux and it's dated October 2026, so screenshot it and send it to the group chat 💌 periodt. 🧚