BUS_BIND_INTR(9)

💖 BUS_BIND_INTR — bestie, let's pin that interrupt 💖

ok so this is a page from the Kernel Developer's Manual, section 9. Yes it's the BUS_BIND_INTR one. Come sit with me, this is actually so good.

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✨ NAME ✨

BUS_BIND_INTR, bus_bind_intr — bind an interrupt resource to a specific CPU 🎀

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🌸 SYNOPSIS 🌸

#include <sys/param.h>
#include <sys/bus.h>

int
BUS_BIND_INTR(device_t dev, device_t child, struct resource *irq,
    int cpu);

int
bus_bind_intr(device_t dev, struct resource *irq, int cpu);

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🦋 DESCRIPTION 🦋

okay so the BUS_BIND_INTR() method lets you pin an interrupt resource to one specific CPU. like, "this one. only this one. periodt." 💅

heads up bestie: the interrupt resource must already have an interrupt handler attached via BUS_SETUP_INTR(9). No handler, no binding, that's the vibe check.

The cpu parameter is the ID of a valid CPU in the system.

Here's what binding actually does, fr fr:

• it restricts the cpuset(2) of any associated interrupt threads so they only include the specified CPU
• it may also direct the low-level interrupt handling of the interrupt to the specified CPU as well — but this behavior is platform-dependent, so don't @ me

And if you pass NOCPU as the value for cpu? Then the interrupt gets “unbound” 🌈 which restores any associated interrupt threads back to the default cpuset. undoing the binding, iconic behavior.

⚠️ Non-sleepable locks such as mutexes should not be held across calls to these functions. like literally do not do that. 😭

The bus_bind_intr() function is just a simple wrapper around BUS_BIND_INTR(). tiny, adorable, does the same thing. 🫶

Note that currently there is no attempt made to arbitrate between multiple bind requests for the same interrupt — whether from the same device or from multiple devices. Also? There is no arbitration between interrupt binding requests submitted by userland via cpuset(2) and BUS_BIND_INTR(). So who wins?

The most recent binding request is the one that will be in effect. Last one in the group chat decides. that's the rule. 👑

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⭐ RETURN VALUES ⭐

Zero on success, bestie. ✨ Otherwise, an appropriate error is returned. 😔

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🌈 SEE ALSO 🌈

• cpuset(2)
• BUS_SETUP_INTR(9)
• device(9)

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🎀 HISTORY 🎀

The BUS_BIND_INTR() method and the bus_bind_intr() functions first appeared in FreeBSD 7.2. throwback era honestly.

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ok that's the whole page, you ate that 💅 this one came from the Debian crew and it's dated October 14, 2009 — so yes, this lore is old but it's still giving main character energy. go bind something (safely) 🦋✨