subsys_param_cb(9)

📦 version 7.3.1, in nixpkgs unstable

🎀 subsys_param_cb — the Kernel API Manual, bestie edition 🎀

okay so picture this: it's a manpage from the Kernel API Manual and it's about one (1) very specific little function. let's get into it 💅

✨ NAME ✨

subsys_param_cb — the general callback for a module/cmdline parameter, and she gets evaluated before the subsys initcall level 👑 (yes, before. she's early. she's punctual. we stan.)

🌸 SYNOPSIS 🌸

subsys_param_cb (name , ops , arg , perm );

that's it. that's the whole vibe check. four things, in that order, no cap 🫶

💖 ARGUMENTS 💖

  • name — a valid C identifier that is the parameter name. literally just has to be a valid C identifier, that's the whole assignment bestie ✨
  • ops — the set & get operations for this parameter. this is where the actual doing happens 🔥
  • arg — args for ops. they get passed along, she's just the messenger 🎀
  • perm — visibility in sysfs. it's giving "who's allowed to see me" energy 🙈

🦋 DESCRIPTION 🦋

so the important tea ☕: the ops can have NULL set or get functions. like, genuinely, that's allowed. NULL set? fine. NULL get? fine. it's not a bug, it's a feature, periodt 💀

ngl this is the entire description and honestly? iconic of her. short, sweet, zero filler. she said "the ops can have NULL set or get functions" and then dipped 🌈

🧚 SEE ALSO 🧚

she has a LOT of friends, and you're gonna meet all of them, okay? every single one:

like I said. a whole friend group. a whole squad. iykyk 😭💜

and that's the page, bestie!! shoutout to ./include/linux for housing all this and to October 2026 for being the date on the tin — mwah, love u, go read your kernel headers 🍓💅✨

📦 where this page comes from