STRUCT I3C_XFER(9)

💖 struct i3c_xfer(9) 💖

okay bestie, so this page lives in the Kernel API Manual and it's literally all about struct i3c_xfer — the I3C data transfer struct. yes, the whole page. it's one struct and it ate. 🦋

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✨ NAME ✨

struct i3c_xfer — I3C data transfer. that's it, that's the vibe. it's the little packet of dreams that carries your bytes back and forth 💅

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🌸 SYNOPSIS 🌸

here's the whole thing, copy it exactly, no cap:

struct i3c_xfer {
    union {
      u8 rnw;
      u8 cmd;
    };
    u16 len;
    u16 actual_len;
    union {
      void *in;
      const void *out;
    } data;
    enum i3c_error_code err;
 };

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👑 Members 👑

• {unnamed_union} — anonymous 🫶 no name, all mystery, main character energy fr fr
• rnw — this one encodes the transfer direction. true for a read, false for a write. she's giving binary literal, we stan 🌈
• cmd — the Read/Write command in HDR mode. read: 0x80 - 0xff, write: 0x00 - 0x7f. memorize the ranges, iykyk 🔥
• len — transfer length in bytes of the transfer. yes, "of the transfer," we're being thorough 💜
• actual_len — the actual length in bytes that the controller transferred. not what you asked for, what you got 😭
• data — the input/output buffer. she's flexible, she contains multitudes ✨
• data.in — input buffer. must point to a DMA-able buffer. not optional, bestie, DMA-able or nothing 💀
• data.out — output buffer. also must point to a DMA-able buffer. same rule, no exceptions 🎀
• err — the I3C error code (type: enum i3c_error_code). your little emotional support error field 🧚

lowkey important: both data.in and data.out have to point at DMA-able buffers. don't come crying to me when you pass it a random stack buffer 🙈

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🦋 SEE ALSO 🦋

go read these next, it's giving required reading, all from the kernel file ./include/linux/i3c/device.h:

• enum i3c_error_code(9)
• enum i3c_xfer_mode(9)
• enum i3c_dcr(9)
• struct i3c_device_info(9)
• struct i3c_driver(9)
• dev_to_i3cdev(9)
• module_i3c_driver(9)
• i3c_i2c_driver_register(9)
• i3c_i2c_driver_unregister(9)
• module_i3c_i2c_driver(9)
• struct i3c_ibi_setup(9)

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k bye bestie, this page came from ./include/linux/i3c, version October 2026, and it's filed under struct i3c_xfer(9) — slay, go write some drivers 💅💖