STRUCT W1_REG_NUM(9)

💅 struct w1_reg_num(9) — Kernel API Manual

okay so real talk bestie, this one's from the Kernel API Manual and it's about struct w1_reg_num — literally just a "broken out slave device id". that's the whole vibe. it's the 1-Wire slave's ID, all sliced up into neat little bitfields so you can actually get at the pieces. 🎀

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✨ NAME ✨

struct w1_reg_num — broken out slave device id 🦋

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🌸 SYNOPSIS 🌸

struct w1_reg_num {
  #if defined(__LITTLE_ENDIAN_BITFIELD);
    __u64 family:8, id:48, crc:8;
  #elif defined(__BIG_ENDIAN_BITFIELD);
    __u64 crc:8, id:48, family:8;
  #else;
  #error Pleasefix<asm/byteorder.h>";"
  #endif;
 };

like, yes, there's a stray #error Pleasefix<asm/byteorder.h>";" in there — that is literally what the page says, so I'm not touching it. if your byteorder header isn't playing nice, the compiler is gonna yell at you. not my problem, bestie. 💀

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🧚 Members 🧚

so the members show up twice in the source, once per endianness branch, and honestly? iconic of it. here's the full list in order, no crumbs left behind:

• family — identifies the type of device 👑
• id — along with family is the unique device id
• crc — checksum of the other bytes
• crc — checksum of the other bytes (yes, again — that's the big-endian branch, slay)
• id — along with family is the unique device id
• family — identifies the type of device

🫶 notice how little-endian puts family, id, crc and big-endian flips it to crc, id, family? same three things, different order. that's the whole point, no cap.

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🌈 SEE ALSO 🌈

go read these next, i'm obsessed:

• Kernel file ./include/linux/w1.h
• struct w1_slave(9)
• struct w1_bus_master(9)
• enum w1_master_flags(9)
• struct w1_master(9)
• struct w1_family_ops(9)
• struct w1_family(9)
• module_w1_family(9)

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and that's the whole page, bestie, we ate and left no crumbs 🍓💅 — this one lives over in ./include/linux and it's stamped October 2026, page struct w1_reg_num(9), periodt. ⭐