v4l2_ctrl_notify(9)

📦 version 7.3.1, in nixpkgs unstable

💅 v4l2_ctrl_notify — a Kernel API Manual moment (section 9, bestie)

okay so real talk, this one's from the Kernel API Manual, section 9, and it's called v4l2_ctrl_notify ✨ it's literally the function that sets a notify callback for a control — tiny function, big main character energy 🎀

✨ NAME ✨

v4l2_ctrl_notify — Function to set a notify callback for a control. that's it, that's the whole job 💅

🦋 SYNOPSIS 🦋

void v4l2_ctrl_notify (struct v4l2_ctrl *ctrl , v4l2_ctrl_notify_fnc
notify , void *priv );

like, look at her. three args, void return, no notes 💖

🌸 ARGUMENTS 🌸

  • ctrl — The control. the actual control we're hooking up, periodt.
  • notify — The callback function. the thing that gets called, iykyk.
  • priv — The callback private handle, passed as argument to the callback. so it's your little backpack of stuff that rides along into the callback 🎒

💜 DESCRIPTION 💜

okay so here's the vibe check: this function sets a callback function for the control. it's that simple, no cap 🫶

if ctrl is NULL, then it will do nothing. like, it just politely doesn't, ghosting you but in a chill way 🙈

if notify is NULL, then the notify callback will be removed. bye bestie 👋✨

⚠️ the one-notify rule, no exceptions: There can be only one notify. If another already exists, then a WARN_ON will be issued and the function will do nothing. so yeah, don't try to stack them — the kernel will literally yell about it and then refuse 💀

🌈 SEE ALSO 🌈

Kernel file ./include/media/v4l2-ctrls.h — and honestly the whole ctrl cinematic universe shows up here, so buckle up bestie 👑

and that's the whole page, mwah 💋 this iconic little number lives in ./include/media, dated October 2026, and goes by v4l2_ctrl_notify(9) — screenshot it, cite it, love it, bye bestie 🎀💖🦋

📦 where this page comes from