pci_enable_msix_range(9)

📦 version 7.3.1, in nixpkgs unstable

💅 pci_enable_msix_range(9) — from the Kernel API Manual, bestie

okay so picture this: you're deep in the kernel, you've got a PCI device, and you want MSI-X interrupt mode turned on. That's literally what pci_enable_msix_range does. Let's get into it ✨

🌸 NAME 🌸

pci_enable_msix_range — enable MSI-X interrupt mode on a device. that's the whole vibe. 💖

✨ SYNOPSIS ✨

int pci_enable_msix_range (struct pci_dev *dev , struct msix_entry
*entries , int minvec , int maxvec );

🎀 ARGUMENTS 🎀

  • dev — the PCI device we're operating on. the main character, honestly.
  • entries — an input/output parameter, fr fr. it's an array of MSI-X configuration entries.
  • minvec — the minimum required number of MSI-X vectors. the bare minimum, the floor, the "i will not accept less than this" number.
  • maxvec — the maximum desired number of MSI-X vectors. the dream number. 🦋

💜 DESCRIPTION 💜

So this is the legacy device driver API — yes, legacy, we'll get to that — and what it does is enable MSI-X interrupt mode on the device and configure its MSI-X capability structure as appropriate. slay.

Here's the important part though: the entries array you pass in must have each of its members' "entry" field set to a desired (valid) MSI-X vector number. and where do you find out what vector numbers are valid? you query it through pci_msix_vec_count. iykyk 🔥

And if it all works out? the driver must invoke pci_disable_msix on cleanup. no cap, that's required, don't leave it hanging. 🙈

⚠️ NOTE ⚠️

bestie. listen. the newer pci_alloc_irq_vectors / pci_free_irq_vectors API pair should, in general, be used instead. this one is the legacy path. still works, still here, but like… the new thing is the moment. 👑

🌈 RETURN 🌈

It returns the number of MSI-X vectors allocated — and heads up, that might be smaller than maxvecs 😭. The Linux IRQ numbers for those allocated vectors get saved back into the entries array elements' "vector" field. cute, right?

Now the error lore:

  • Return -ENOSPC if fewer than minvecs interrupt vectors are available. not enough vectors to go around, sorry babe 💀
  • Return -EINVAL if one of the passed entries members' "entry" field was invalid or a duplicate — or if plain MSI interrupts mode was earlier enabled on the device. yeah, that last one will get you.
  • Return other errnos otherwise. the usual suspects, we don't list them, that's the deal. 🫶

🧚 SEE ALSO 🧚

Kernel file ./drivers/pci/msi/api.c, plus the whole friend group:

and that's the page!! 🎀 this one lives in ./drivers/pci/msi, dated October 2026 — go read the source bestie, it's giving iconic. 💅⭐

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