msi_domain_alloc_irq_at(9)

msi_domain_alloc_irq_at(9)

okay so bestie, this one is straight from the Kernel API Manual ✨ and it's literally about grabbing an interrupt from a MSI interrupt domain — either at a specific index you pick, or at the next free one. iconic behavior tbh 🎀

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✨ NAME ✨

msi_domain_alloc_irq_at — Allocate an interrupt from a MSI interrupt domain at a given index — or at the next free index 🦋

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💅 SYNOPSIS 💅

here's the signature, character-for-character, no cap:

struct msi_map msi_domain_alloc_irq_at (struct device *dev , unsigned
int domid , unsigned int index , const struct irq_affinity_desc *affdesc
, union msi_instance_cookie *icookie );

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🧚 ARGUMENTS 🧚

• dev — Pointer to device struct of the device for which the interrupts are allocated. like, the device we're doing all this for 💖
• domid — Id of the interrupt domain to operate on.
• index — Index for allocation. If index == MSI_ANY_INDEX the allocation uses the next free index. periodt ✨
• affdesc — Optional pointer to an interrupt affinity descriptor structure.
• icookie — Optional pointer to a domain specific per instance cookie. If non-NULL the content of the cookie is stored in msi_desc::data. Must be NULL for MSI-X allocations 🚨

🚨 bestie, listen: icookie Must be NULL for MSI-X allocations. that part is not a vibe suggestion, it's a hard rule 💀

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🌸 DESCRIPTION 🌸

This requires a MSI interrupt domain which lets the core code manage the MSI descriptors.

On success msi_map::index contains the allocated index number and msi_map::virq the corresponding Linux interrupt number 👑

On failure msi_map::index contains the error code and msi_map::virq is 0.

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💜 RETURN 💜

struct msi_map — that's the return type, bestie 🫶

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🌈 SEE ALSO 🌈

go read these too, iykyk:

• Kernel file ./kernel/irq/msi.c
• struct msi_device_data(9)
• struct msi_ctrl(9)
• msi_alloc_desc(9)
• msi_domain_insert_msi_desc(9)
• msi_domain_free_msi_descs_range(9)
• msi_domain_add_simple_msi_descs(9)
• msi_setup_device_data(9)
• __msi_lock_descs(9)
• __msi_unlock_descs(9)
• msi_domain_first_desc(9)
• msi_next_desc(9)
• msi_domain_get_virq(9)
• msi_device_populate_sysfs(9)
• msi_device_destroy_sysfs(9)
• msi_domain_set_affinity(9)
• msi_create_irq_domain(9)
• msi_create_parent_irq_domain(9)
• msi_parent_init_dev_msi_info(9)
• msi_create_device_irq_domain(9)
• msi_remove_device_irq_domain(9)
• msi_match_device_irq_domain(9)
• msi_domain_alloc_irqs_range_locked(9)
• msi_domain_alloc_irqs_range(9)
• msi_domain_alloc_irqs_all_locked(9)
• msi_device_domain_alloc_wired(9)
• msi_domain_free_irqs_range_locked(9)
• msi_domain_free_irqs_range(9)
• msi_domain_free_irqs_all_locked(9)
• msi_domain_free_irqs_all(9)
• msi_device_domain_free_wired(9)
• msi_get_domain_info(9)
• msi_device_has_isolated_msi(9)

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okay bye bestie 💖 — source/version: ./kernel/irq · date: October 2026 · mwah 💋