comedi_buf_read_alloc(9)

📦 version 7.3.1, in nixpkgs unstable

💖 comedi_buf_read_alloc(9) 💖

okay so bestie, welcome to the Kernel API Manual ✨ — this one's a kernel-function page, not your usual command-line moment, but it still eats. let's get into it 🎀

🌸 NAME 🌸

comedi_buf_read_alloc — reserve buffer space for reading 👑

🦋 SYNOPSIS 🦋

unsigned int comedi_buf_read_alloc (struct comedi_subdevice *s ,
       unsigned int nbytes );

literally the whole signature, character for character, no notes 💅

🍓 ARGUMENTS 🍓

  • s — the COMEDI subdevice 🌟 like, the thing you're working with.
  • nbytes — the maximum space to reserve, in bytes. key word maximum, she is a limit not a promise 🙈

✨ DESCRIPTION ✨

so what this function actually does: it reserves up to nbytes bytes of buffer space for reading 🫶 but — and this is the vibe — it's only the stuff that was previously written and already "munged" (yes, that's the real word, iykyk) in the COMEDI acquisition data buffer that's associated with the subdevice.

the amount it actually reserves is limited to the space available 💀 so if you ask for nbytes and there's less room, you get less room. no cap.

once it's reserved, the reader can read from that reserved space and then free it. slay 🌈

and here's the little plot twist 🎀: a reader is also allowed to read from the space before reserving it — as long as it figures out how much readable data is actually available. but listen to me bestie 👉 that space still needs to be marked as reserved before it can be freed. like, you can peek early but you can't yeet it until it's reserved. periodt 💅

🔥 RETURN 🔥

the amount of space reserved, in bytes ⭐ (again: reserved, not requested — those are different numbers and you should not be shocked)

👑 SEE ALSO 👑

kernel file ./drivers/comedi/comedi_buf.c — go read her, she's iconic 📖 and her friends:

the whole friend group fr fr 🫶

💜 tiny reminder: nbytes is a maximum. check the return value before you go reading, bestie, that's the whole point of it returning a number 😭

and that's the page! 🧚 source ./drivers/comedi, dated October 2026, filed under comedi_buf_read_alloc(9) — mwah, go reserve some space, love u, bye 💖✨🎀

📦 where this page comes from