kfifo_to_user(9)

📦 version 7.3.1, in nixpkgs unstable

💅 kfifo_to_user — kernel API manual, but make it cute ✨

okay so bestie, you found the kfifo_to_user(9) page in the Kernel API Manual and honestly? it's a tiny little macro that does one job and does it slayfully. let's get into it 🎀

🌸 NAME 🌸

kfifo_to_user — copies data from the fifo into user space 💖

like literally, that's the whole personality. fifo data goes out into user space. periodt.

✨ SYNOPSIS ✨

kfifo_to_user (fifo , to , len , copied );

four args, no drama. write them out exactly like that, spaces and all, she's particular 💅

🫶 ARGUMENTS 🫶

  • fifo — address of the fifo to be used. this is your little fifo bestie, hand her over.
  • to — where the data must be copied. destination buffer energy ✨
  • len — the size of the destination buffer. don't overshoot, that's not the vibe.
  • copied — pointer to output variable to store the number of copied bytes. she reports back how much actually made it, iykyk 🔥

🦋 DESCRIPTION 🦋

so this macro copies at most len bytes from the fifo into the to buffer, and returns -EFAULT/0. that's it. that's the whole function. iconic behaviour, no notes 👑

⚠️ and here's the caveat bestie, do not skip this: with only one concurrent reader and one concurrent writer, you don't need extra locking to use these macro. only one reader and one writer though — the second that math changes, you're on your own 💀

🌈 SEE ALSO 🌈

kernel file ./include/linux/kfifo.h, plus the whole entire kfifo friend group:

that's every single one, i counted, main character energy across the whole header file fr fr 💜

and that's the page babes 🧚 from ./include/linux, dated October 2026, signed kfifo_to_user(9) — mwah, study it, love you, bye 🍓💖

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