x86_msi_prepare(9)

💅 x86_msi_prepare(9) — the Kernel API Manual, but make it a group chat

Okay bestie, gather round, because today we're talking about x86_msi_prepare(9) — it lives in the Kernel API Manual and honestly? It's giving setup-girlie energy. It doesn't do the allocation itself, it prepares for the allocation, which is a whole mood. 🎀

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✨ NAME ✨

x86_msi_prepare — setup of msi_alloc_info_t for allocations. That's it, that's the vibe. It gets the allocation info ready so the actual allocation can slay later. 💖

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🌸 SYNOPSIS 🌸

int x86_msi_prepare (struct irq_domain *domain , struct device *dev ,
       int nvec , msi_alloc_info_t *alloc );

Look at her. Four params, one int return, absolutely iconic. 🔥

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🦋 ARGUMENTS 🦋

• domain — the domain for which this setup happens. Like, whose house are we decorating? 🏠
• dev — the device for which interrupts are allocated. The main character in question. 👑
• nvec — the number of vectors to allocate. Count them, bestie. 🔢
• alloc — the allocation info structure to initialize. This is the one we're actually filling in, so pay attention. ✨

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💜 DESCRIPTION 💜

Okay so here's the tea: this function is to be used for all types of MSI domains above the x86 vector domain and any intermediates. All of them. No exceptions, no cap. 🫶

It is always invoked from the top level interrupt domain — always, fr fr, that's not a sometimes thing.

And how does it know what to do? The domain specific allocation functionality is determined via the domain's bus token, which is what allows it to map the X86 specific allocation type. So the bus token is basically the vibe check that tells this function which flavour of allocation it's dealing with. Lowkey elegant, highkey important. 💅

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🌈 SEE ALSO 🌈

• Kernel file ./arch/x86/kernel/apic/msi.c — go read the source, iykyk 🧚
• pci_dev_has_default_msi_parent_domain(9) — bestie with a long name, love that for her
• x86_init_dev_msi_info(9) — the other bestie in this friend group

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Not me ending the page already 😭 but that's genuinely the whole thing — every option, every argument, every reference, all accounted for. Periodt. 💀

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Source: ./arch/x86/kernel/apic · Version/date: October 2026 · x86_msi_prepare(9)

Mwah, that's a wrap bestie — October 2026, straight out of ./arch/x86/kernel/apic, and she ate. 💖✨🎀🦋🌸💅🫶👑🌈⭐