msix_prepare_msi_desc(9)

📦 version 7.3.1, in nixpkgs unstable

💅 msix_prepare_msi_desc — Kernel API Manual energy

okay so bestie, listen up, because this one is genuinely a little cutie 💖 It lives in the Kernel API Manual, and its whole job is getting a half-initialized MSI descriptor ready to go. Yes, half. We'll get there. 🎀

✨ NAME ✨

msix_prepare_msi_desc — prepare a half initialized MSI descriptor for operation 🫶

🦋 SYNOPSIS 🦋

void msix_prepare_msi_desc (struct pci_dev *dev , struct msi_desc *desc );

🌸 ARGUMENTS 🌸

  • dev — the PCI device that this descriptor is being prepared for, like the main character of the whole operation 👑
  • desc — the MSI descriptor getting prepped, glow-up incoming ✨

🔥 DESCRIPTION 🔥

So here's the tea: this function exists separately from msix_setup_msi_descs (which is mentioned "below", iykyk) so it can handle dynamic allocations for MSI-X after initial enablement. It's giving backstage-pass energy. 💅

Ideally the whole MSI-X setup would work that way, but nope 😭 there's literally no way to support that for the legacy arch_setup_msi_irqs mechanism, nor for the fake irq domains like the x86 XEN one. Sigh... 🫠

Here's exactly what happens, no cap:

  • the descriptor gets zeroed 🌈
  • and only desc::msi_index and desc::affinity are set ⭐
  • when it's called from msix_setup_msi_descs, then the is_virtual attribute gets initialized as well 🧚

Then? Fill in the rest. 🍓 That's the vibe, bestie — this function sets up the skeleton and dips.

lowkey important: it's only setting those specific fields. Don't assume it fills anything else in for you — that part is literally someone else's job. 🙈

💜 SEE ALSO 💜

all of these are your new besties, go say hi 🦋

and that's the whole page, periodt 🎀💅 this gem lives in ./drivers/pci/msi and the source version/date on the tin is October 2026 — so yes, she's from the future and she's iconic for it 👑✨💀

📦 where this page comes from