STRUCT CCW_DEV_ID(9)

✨ struct ccw_dev_id(9) ✨

okay so bestie, we're in the Kernel API Manual today and the star of the show is struct ccw_dev_id — literally the unique identifier for ccw devices 💅 no cap, that's the whole vibe.

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🌸 SYNOPSIS 🌸

like, here's the whole entire struct, and yes it's small but she's iconic:

struct ccw_dev_id {
    u8 ssid;
    u16 devno;
 };

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🎀 Members 🎀

okay bestie let's meet the two members, they're giving main character energy:

• ssid — the subchannel set id 🦋
• devno — the device number ⭐

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💖 Description 💖

so here's the tea: this structure is not directly based on any hardware structure. like, not even a little. 🙈

the hardware identifies a device by its device number and its subchannel — and that subchannel is in turn identified by its id. so to get a unique identifier for ccw devices across subchannel sets, struct ccw_dev_id has been introduced. periodt. 👑

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🌈 SEE ALSO 🌈

• Kernel file ./arch/s390/include/asm/cio.h — the home of it all, iykyk
• struct ccw1(9)
• struct ccw0(9)
• struct erw(9)
• struct erw_eadm(9)
• struct sublog(9)
• struct esw0(9)
• struct esw1(9)
• struct esw2(9)
• struct esw3(9)
• struct esw_eadm(9)
• struct irb(9)
• struct ciw(9)
• ccw_dev_id_is_equal(9)
• pathmask_to_pos(9)

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bestie, this one's fully documented — no hidden bugs, no warnings, no dangerous caveats to scream about. we love a clean page 🫶

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🌸 okay that's the whole page, mwah 💋 — this one lives at ./arch/s390/include/asm, dated October 2026, in the Kernel API Manual. go off, s390 girlies 🧚‍♀️💜