UNION I2C_CMD_BASE(9)

💅 union i2c_cmd_base ✨ <small>Kernel API Manual</small>

okay so bestie, gather round 🫶 this is union i2c_cmd_base from the Kernel API Manual, and it is exactly what it sounds like: a union that lets you poke at C2P commands bit by bit. that's it, that's the vibe. no cap, it's giving "tiny little bitfield icon" 🔥

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🌸 NAME 🌸

union i2c_cmd_base — bit access of C2P commands 💫

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✨ SYNOPSIS ✨

union i2c_cmd_base {
    u32 ul;
    struct {
      enum i2c_cmd i2c_cmd : 4;
      u8 bus_id : 4;
      u32 slave_addr : 8;
      u32 length : 12;
      enum speed_enum i2c_speed : 3;
      enum mem_type mem_type : 1;
    } s;
 };

so you've got two ways to look at the same thing, and they overlap on purpose 💅

• u32 ul — the whole thing as one raw 32-bit word, one chunky little unit, main character energy 👑
• struct s — the same bits, sliced up into fields ✂️ literally the "both? both. both is good" meme

and the slices inside s? let's count the bits together, it's a whole thing 🧚:

• enum i2c_cmd i2c_cmd : 4 — 4 bits of <mint>i2c_cmd</mint>
• u8 bus_id : 4 — 4 bits of <mint>bus_id</mint> (a u8, yes, with 4 bits, the page said what it said 🙈)
• u32 slave_addr : 8 — 8 bits of <mint>slave_addr</mint>
• u32 length : 12 — 12 bits of <mint>length</mint>, the biggest slice, she ate 💀
• enum speed_enum i2c_speed : 3 — 3 bits of <mint>i2c_speed</mint>
• enum mem_type mem_type : 1 — a whole 1 bit of <mint>mem_type</mint>, tiny but iconic 🎀

that's 4 + 4 + 8 + 12 + 3 + 1 = the 32 you already met in ul 🌈 cute when math works out.

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🎀 MEMBERS 🎀

so the Members heading is literally up in the original page and then… nothing. no entries. just vibes and empty space 🫠 bestie i'm not gonna lie to you and make stuff up — the only member info you're getting is the ul / s situation spelled out in the struct above ⭐ everything literal lives in the SYNOPSIS, periodt.

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🦋 SEE ALSO 🦋

like, go look at these, they're the friend group 💜

• Kernel file ./drivers/i2c/busses/i2c-amd-mp2.h 📁
• union i2c_event(9)
• struct amd_i2c_common(9)
• struct amd_mp2_dev(9)

side note: yes, all of these live in ./drivers/i2c/busses — same neighborhood, same friend group, iykyk 🦋

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and that's the whole page, bestie 🫶 the source path is ./drivers/i2c/busses, it's dated October 2026, and it's filed under union i2c_cmd_base(9) — slay, go read a struct, ily 😭💖🎀