field_get(9)

📦 version 7.3.1, in nixpkgs unstable

💖 NAME 💖

okay so bestie, welcome to field_get(9) from the Kernel API Manual — it's a function that extracts a bitfield element, and it's lowkey iconic for when your mask isn't a compile-time constant. periodt. 💅

✨ SYNOPSIS ✨

field_get (mask , reg );

no cap, that's the whole vibe. two arguments, one little field value coming back to you. 🎀

🌸 ARGUMENTS 🌸

  • mask — the shifted mask that defines the field's length and position. it must be non-zero, bestie, like literally non-zero or don't even try it. 🫶
  • reg — the value of the entire bitfield. think of it as the whole group chat and mask is the one message you're trying to pull out. 💌

🦋 RETURN 🦋

the extracted field value. that's it, that's the tea. ✨

💜 DESCRIPTION 💜

okay so field_get extracts the field specified by mask from the bitfield passed in as reg — by masking and shifting it down. literally masking, then shifting, then slay. 💅

the big deal here is that — unlike FIELD_GET — mask is not limited to a compile-time constant. so you can be a little flexible with it. typical usage patterns are:

  • a value stored in a table, or
  • calculated by shifting a constant by a variable number of bits.

and if you do want to ensure that mask is a compile-time constant? bestie, please use FIELD_GET directly instead. it's giving "right tool for the right job," and we respect that. 👑

fr fr: FIELD_GET is your compile-time-constant queen. field_get is the flexible runtime friend. don't mix them up. 💀

🌈 SEE ALSO 🌈

kernel file ./include/linux/bitfield.h — and the whole friend group:

and that's the page, bestie 🧚 this little beauty lives under ./include/linux, comes from October 2026, and is brought to you by the field_get(9) manual page. mwah 💋✨

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