STRUCT REGBIT(9)

💅 struct regbit(9) — Kernel API Manual, bestie edition 🎀

okay so bestie, welcome to the glow-up of the struct regbit manpage, from the Kernel API Manual. this one's short but she's iconic — a whole tiny struct that exists to pack one single bit into as few bytes as possible. main character energy fr fr ✨

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🦋 NAME 🦋

struct regbit — describe one bit in a register 💫

like, literally just one bit. one. tiny. bit. and this struct is the whole personality ✨

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🌸 SYNOPSIS 🌸

struct regbit {
    u16 bit:5;
    u16 reg:11;
 };

that's her!! that's the whole struct!! and yes the original has that little space before the closing }; — keeping it exactly as it is, character for character, because we respect the source 💅

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🎀 Members 🎀

• bit — which bit (0 to 31) in the register 🧚 lowkey the whole point of the struct ngl
• reg — offset of register relative to base address, expressed in units of 32-bit words (not bytes), ⚠️ not bytes ⚠️ — this is the detail everyone gets wrong, iykyk

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🔥 Description 🔥

so the whole point of this structure is that it's used to compactly encode the location of a single bit in a register 🫶 like, she's not here to be spacious, she's here to be snatched.

here's the math bestie, and it's giving bit-budget: five bits are needed to encode the bit number. and with the uint16_t data type, that leaves 11 bits to encode a register offset up to 2047 👑

and because registers are aligned on 32-bit boundaries, the offset gets specified in 32-bit words rather than bytes 💖 which means you can encode an offset up to 0x1FFC (8188) bytes. yes both numbers. no we're not rounding. we don't do that here 🌈

and the helper macro RB takes care of converting the register offset from bytes to 32-bit words for you, because she's a queen and she handles the messy part 💅✨

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⭐ SEE ALSO ⭐

• Kernel file ./drivers/clk/renesas/r9a06g032-clocks.c struct r9a06g032_gate(9), struct r9a06g032_clkdesc(9) 🦋

go read those next, bestie, they're in the same friend group 💜

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ngl this struct is tiny but she ate. packing a bit number AND a register offset into 16 bits? obsessed. 🍓

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and that's the page!! 🌸 sign-off time: this one lives over at ./drivers/clk/renesas, dated October 2026 — so she's fresh, she's Reneasas-adjacent, and she's ready for you. mwah 💋🎀💖