STRUCT SUBLOG(9)

struct sublog(9) 💅

okay so this is from the Kernel API Manual and it's literally the subchannel logout area — a struct so packed with bitfields it's giving "I have exactly this many bits and not one more" energy. no cap, every field is a tiny slice of a __u32, and you gotta respect the bit budget. 🎀

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✨ NAME ✨

struct sublog — subchannel logout area

like, the place where logout info lives. that's the vibe. 🦋

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🌸 SYNOPSIS 🌸

struct sublog {
    __u32 res0  : 1;
    __u32 esf   : 7;
    __u32 lpum  : 8;
    __u32 arep  : 1;
    __u32 fvf   : 5;
    __u32 sacc  : 2;
    __u32 termc : 2;
    __u32 devsc : 1;
    __u32 serr  : 1;
    __u32 ioerr : 1;
    __u32 seqc  : 3;
};

count the bits bestie, they add up to 32 and that is not an accident 💀 it's one __u32 carved into eleven little pieces like a charcuterie board 🍓

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👑 Members 👑

• res0 — reserved 🙈 nothing to see here, keep scrolling
• esf — extended status flags ✨ (7 whole bits of them)
• lpum — last path used mask 🛤️
• arep — ancillary report 📋
• fvf — field-validity flags ✅ (which fields actually mean something, iykyk)
• sacc — storage access code 🗄️
• termc — termination code 🛑
• devsc — device-status check 🖥️
• serr — secondary error 😭
• ioerr — i/o-error alert 🔥
• seqc — sequence code 🔢

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💜 SEE ALSO 💜

Kernel file ./arch/s390/include/asm/cio.h — and the whole friend group:

• struct ccw1(9)
• struct ccw0(9)
• struct erw(9)
• struct erw_eadm(9)
• struct esw0(9)
• struct esw1(9)
• struct esw2(9)
• struct esw3(9)
• struct esw_eadm(9)
• struct irb(9)
• struct ciw(9)
• struct ccw_dev_id(9)
• ccw_dev_id_is_equal(9)
• pathmask_to_pos(9)

like, that's the whole s390 cio squad and they all ate 🔥 go read them too, fr fr

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that's the page bestie! 🌈 source-side it lives in the Kernel file ./arch/s390/include/asm, dated October 2026 — so go forth, read your bitfields, and slay 💅✨🫶