v4l2_g_ctrl(9)

📦 version 7.3.1, in nixpkgs unstable

💅 v4l2_g_ctrl (kernel API manual, bestie edition)

okay so this is a page from the Kernel API Manual — yes the man page name is literally v4l2_g_ctrl(9), we love a self-titled icon ✨ — and it's about one tiny helper function that does a very specific job. she's small, she's focused, she's giving "I only do one thing but I do it correctly" energy 🎀

🌸 NAME 🌸

v4l2_g_ctrl — the helper function you use to implement the :ref:VIDIOC_G_CTRL <vidioc_g_ctrl>`` ioctl 💫

like, that's her whole personality. that's the job. she's the glue between your driver and the userspace control-getting ioctl, no cap 🫶

✨ SYNOPSIS ✨

int v4l2_g_ctrl (struct v4l2_ctrl_handler *hdl , struct v4l2_control
*ctrl );

literally two pointers in, one int out. the signature is exactly that, spacing and line break and all — I did not touch it, I would never 🙈

🦋 ARGUMENTS 🦋

  • hdl — a pointer to struct v4l2_ctrl_handler. yes, the handler. the control handler. the main character of the control subsystem, honestly 👑
  • ctrl — a pointer to struct v4l2_control. this is the control struct itself, the thing that's gonna get its info read 📖

💜 DESCRIPTION 💜

okay so here's the entire described behaviour, and I need you to sit with it because it's short and it's important:

if hdl == NULL then they will all return -EINVAL.

that's it. that's the description. no cap, the whole documented description is that NULL check 💀 so if you pass a NULL handler, expect -EINVAL coming right back at you. that's the deal. that's the contract. respect it 🙏

(also notice the word "they" — the original says they will all return, which is doing a little hinting that this is one of a family of sibling helpers. cute. noted. anyway.)

🌈 SEE ALSO 🌈

bestie. bestie. sit down. this list is long and I am not skipping a single one of them, because every single entry is part of the page and I would never do you dirty like that 😭 so here we go, in the original order, all of them, plus the kernel file:

like I said. long list. every one of them made it, none got left at the club 🫶💅

🎀 cute sign-off 🎀

this little love letter to the control subsystem lives under the ./include/media source, dated October 2026, and it goes by v4l2_g_ctrl(9) — same name up top, same name down here, consistent queen behavior 👑✨ that's the whole page bestie, go read v4l2_ctrls.h and slay 🔥

📦 where this page comes from