ccw_device_halt(9)

📦 version 7.3.1, in nixpkgs unstable

💅 ccw_device_halt — a Kernel API Manual moment (section 9, bestie)

Okay so picture this: you're deep in the ./drivers/s390/cio directory of the Kernel API Manual (section 9, yes that section), and you need to halt some I/O request processing. That's the whole vibe. Let me walk you through it 🫶

✨ SYNOPSIS ✨

int ccw_device_halt (struct ccw_device *cdev , unsigned long intparm );

That's the whole signature, no cap — two args, one int coming back at you.

🎀 ARGUMENTS 🎀

  • cdev — the target ccw device. Like, the device you're doing this to. Main character of the operation 💖
  • intparm — the interruption parameter that gets returned when hsch concludes. So you hand it over now, it comes back to you later. It's giving "hold my jacket, I'll want it back" 🙈

🌸 DESCRIPTION 🌸

So ccw_device_halt literally just calls hsch on cdev's subchannel. That's it. That's the function 💅

And here's the cute part: the interruption handler will echo back the intparm you specified here — unless another interruption parameter got specified by a subsequent invocation of ccw_device_clear. So keep that in mind if you're calling clear afterwards, because then your little intparm is not the one coming home 😭

🔥 RETURN 🔥

  • 0 — success, slay ✨
  • -ENODEV — device not operational
  • -EINVAL — invalid device state
  • -EBUSY — device busy or interrupt pending

👑 CONTEXT 👑

Interrupts disabled, ccw device lock held. Periodt. Don't come in here without those, fr fr 💀

🌈 SEE ALSO 🌈

Kernel file ./drivers/s390/cio/device_ops.c — go read it, iykyk 📖

And the whole friend group, in order:

Every single one, because we don't skip the boring parts in this house 💜

Bye bestie!! This page lives in ./drivers/s390/cio, and it's stamped October 2026 — go halt some I/O request processing responsibly, mwah 💋🎀

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