pci_host_br...i_msi_domain(9)

💅 pci_host_br...i_msi_domain(9) — like, the Kernel API Manual page, bestie ✨

okay so picture this: you're deep in the kernel, staring at a PCI host bridge, and you're like "girl, where is your MSI domain??" 😭 that's literally this page. it lives in the Kernel API Manual, and the function is pci_host_bridge_acpi_msi_domain (yes the header truncates it to pci_host_br...i_msi_domain(9), she's just being dramatic 💅).

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🌸 SYNOPSIS 🌸

struct irq_domain * pci_host_bridge_acpi_msi_domain (struct pci_bus *bus
);

like, it takes a bus and hands you back a struct irq_domain * — that's the whole vibe ✨

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🎀 ARGUMENTS 🎀

• bus — the PCI host bridge bus 💖 that's it, that's the one (1) argument, she's lowkey simple like that.

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🦋 DESCRIPTION 🦋

okay so here's the tea ☕: this function calls up the callback function that got registered by pci_msi_register_fwnode_provider, and uses it to retrieve the irq_domain with type DOMAIN_BUS_PCI_MSI for the specified host bridge bus. no cap, that's the whole move 🫶

and then — this is the important part, don't skip it 🙈 — it returns NULL on error, or when the domain is just… not found. so if you get NULL back, that's not a bug, that's just her telling you the domain isn't there 💀

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👑 SEE ALSO 👑

this function is hanging out in the kernel file ./drivers/pci/pci-acpi.c — go say hi 💜 and while you're in the neighborhood, here's the whole friend group (iykyk):

• pciehp_is_native(9)
• shpchp_is_native(9)
• pci_acpi_wake_bus(9)
• pci_acpi_wake_dev(9)
• pci_acpi_add_root_pm_notifier(9)
• pci_acpi_add_pm_notifier(9)
• pci_dev_acpi_reset(9)
• pci_acpi_set_companion_lookup_hook(9)
• pci_acpi_clear_companion_lookup_hook(9)
• pci_acpi_optimize_delay(9)
• pci_msi_register_fwnode_provider(9)

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reminder bestie: NULL is a real answer here, not a personal attack 😭 error or no domain found, same NULL, same energy 🎀

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✨ sign-off time ✨ this icon of a page comes from ./drivers/pci, dated October 2026 — and that's the whole manual entry, periodt 💅🦋💖