STRUCT MSI_DOMAIN_OPS(9)

💅 struct msi_domain_ops(9) — the MSI interrupt domain callback squad

okay bestie, so this is struct msi_domain_ops from the Kernel API Manual, section 9 (kernel internals, iykyk). it's the official list of callbacks an MSI interrupt domain can hand you. think of it as the group chat roles for your irq domain — everyone has a job, and if you don't assign one, the default kicks in. periodt. ✨

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✨ SYNOPSIS ✨

here's the whole struct, exactly as it lives — no cap, every field:

struct msi_domain_ops {
    irq_hw_number_t (*get_hwirq)(struct msi_domain_info *info,
msi_alloc_info_t *arg);
    int (*msi_init)(struct irq_domain *domain, struct msi_domain_info
*info, unsigned int virq, irq_hw_number_t hwirq, msi_alloc_info_t *arg);
    void (*msi_free)(struct irq_domain *domain, struct msi_domain_info
*info, unsigned int virq);
    int (*msi_prepare)(struct irq_domain *domain, struct device *dev,
int nvec, msi_alloc_info_t *arg);
    void (*msi_teardown)(struct irq_domain *domain, msi_alloc_info_t
*arg);
    void (*prepare_desc)(struct irq_domain *domain, msi_alloc_info_t
*arg, struct msi_desc *desc);
    void (*set_desc)(msi_alloc_info_t *arg, struct msi_desc *desc);
    int (*domain_alloc_irqs)(struct irq_domain *domain, struct device
*dev, int nvec);
    void (*domain_free_irqs)(struct irq_domain *domain, struct device
*dev);
    int (*msi_translate)(struct irq_domain *domain, struct irq_fwspec
*fwspec, irq_hw_number_t *hwirq, unsigned int *type);
 };

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🎀 MEMBERS 🎀

• get_hwirq — get the resulting hardware irq number. literally the "what's my actual hw irq" hook 🌸
• msi_init — the domain-specific init function for MSI interrupts. sets your babies up 💖
• msi_free — domain-specific function to free an MSI interrupt. cleanup queen 👑
• msi_prepare — prep the allocation of the interrupts inside the domain. the pre-game ritual ✨
• msi_teardown — reverse the effects of msi_prepare. undoing the vibe check 🫶
• prepare_desc — optional function to prepare the allocated MSI descriptor in the domain. optional but iconic 💅
• set_desc — set the MSI descriptor for an interrupt. assign the desc, no discussion 💀
• domain_alloc_irqs — optional function to override the default allocation function. main character energy, taking over the default 🔥
• domain_free_irqs — optional function to override the default free function. the matching override for cleanup 🌈
• msi_translate — optional translate callback to support the odd wire-to-MSI bridges, e.g. MBIGEN. for the weird edge cases, and honestly? obsessed 🦋

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🌟 DESCRIPTION 🌟

so get_hwirq, msi_init and msi_free are the callbacks used by the underlying irqdomain. that's their whole thing, they belong to the irqdomain. fr fr.

msi_check, msi_prepare, msi_teardown, prepare_desc and set_desc are the callbacks used by the msi_domain_alloc/free_irqs*() variants. yes — msi_check is named here in the description even though it's not one of the struct members up above. that's just how the kernel do. 🙈

domain_alloc_irqs, domain_free_irqs can be used to override the default allocation/free functions (__msi_domain_alloc/free_irqs). and the lore behind that? it's initially for a wrapper around XEN's separate MSI universe which can't be wrapped into the regular irq domains concepts by mere mortals. 😭 like, mortals literally cannot. this allows you to universally use msi_domain_alloc/free_irqs without having to special case XEN all over the place. we love a clean abstraction, periodt. 💜

ngl, the "by mere mortals" line is doing a LOT of work here and I respect it deeply. 💅

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👀 SEE ALSO 👀

• Kernel file ./include/linux/msi.h — and then the whole extended universe:
• struct msi_msg(9)
• struct pci_msi_desc(9)
• union msi_domain_cookie(9)
• struct msi_desc_data(9)
• struct msi_desc(9)
• struct msi_dev_domain(9)
• msi_first_desc(9)
• msi_domain_for_each_desc(9)
• msi_for_each_desc(9)
• msi_msg_set_addr(9)
• msi_insert_msi_desc(9)
• msi_free_msi_descs_range(9)
• msi_free_msi_descs(9)
• struct msi_domain_info(9)
• struct msi_domain_template(9)
• struct msi_parent_ops(9)

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okay that's the whole page, bestie, every last callback accounted for. 🧚

this cutie lives in ./include/linux, stamped October 2026, and the page itself is struct msi_domain_ops(9). go forth and slay your interrupt domain 💖✨