request_nmi(9)

💅 request_nmi(9) — like, the NMI line allocator ✨

okay so first things first, this is request_nmi(9) from the Kernel API Manual — yes, the big serious kernel docs, but we're gonna make it make sense, bestie 🫶

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✨ NAME ✨

request_nmi — allocate an interrupt line for NMI delivery 🎀

🌸 SYNOPSIS 🌸

int request_nmi (unsigned int irq , irq_handler_t handler , unsigned
long irqflags , const char *name , void *dev_id );

like, that's the whole vibe. five things in, one int out 💜

🦋 ARGUMENTS 🦋

• irq — the interrupt line you're allocating. the main character of this whole operation 👑
• handler — the function that gets called when the IRQ happens. and yeah, for threaded interrupts this is the threaded handler, no cap 🧵
• irqflags — the interrupt type flags. the little settings that say what kind of interrupt this is ✨
• name — an ascii name for the claiming device. gotta claim it, gotta name it 💅
• dev_id — a cookie 🍪 that gets passed right back to your handler function. it comes back to you, fr fr

🔥 DESCRIPTION 🔥

so this call allocates interrupt resources and enables the interrupt line AND the IRQ handling. literally does both. and the key part: it sets up the IRQ line to be handled as an NMI ⭐

okay now the rules, because there are rules and they are not optional:

• An interrupt line delivering NMIs cannot be shared, periodt. no sharing, not even with your bestie 🙅‍♀️
• IRQ handling cannot be threaded. not a thing. don't try it 💀
• Interrupt lines requested for NMI delivering must produce per cpu interrupts and must have auto enabling setting disabled. both. non-negotiable ✋

dev_id must be globally unique 🌈 normally people just use the address of the device data structure as the cookie, and honestly that makes sense since the handler receives this value — so like, why wouldn't you 🎀

and if the interrupt line just can't be used to deliver NMIs? the function fails and returns a negative value 😭 that's your vibe check failing, sorry babes.

🧚 SEE ALSO 🧚

a whole friend group of kernel file ./kernel/irq/manage.c plus all these icons 👑:

• synchronize_hardirq(9), synchronize_irq(9), irq_can_set_affinity(9)
• irq_can_set_affinity_usr(9), irq_set_thread_affinity(9), irq_affinity_schedule_notify_work(9)
• irq_update_affinity_desc(9), irq_set_affinity(9), irq_force_affinity(9)
• irq_set_affinity_notifier(9), irq_set_vcpu_affinity(9)
• disable_irq_nosync(9), disable_irq(9), disable_hardirq(9), disable_nmi_nosync(9)
• enable_irq(9), enable_nmi(9)
• irq_set_irq_wake(9), irq_wake_thread(9)
• free_irq(9), request_threaded_irq(9), request_any_context_irq(9)
• irq_percpu_is_enabled(9), free_percpu_irq(9), request_percpu_irq_affinity(9)
• request_percpu_nmi(9), prepare_percpu_nmi(9), teardown_percpu_nmi(9)
• irq_get_irqchip_state(9), irq_set_irqchip_state(9)
• irq_has_action(9), irq_check_status_bit(9)

like, that's the whole group chat, go say hi 💖

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and that's the page!! brought to you by ./kernel/irq, dated October 2026 — screenshot it, save it, frame it, slay 💅✨🦋