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[[!tag stable_URL]]
Damien Zammit authored libirqhelp, which lets userspace attach and
handle interupts. Suppose, a user presses a key on his keyboard, then
the keyboard can send an interrupt request (an IRQ), to the
processor. The CPU will try to interrupt the program, so that a
callback handler can run instead. A brief overview of `x86` interrupt
information can be found on
[[wikipedia|https://en.wikipedia.org/wiki/Interrupt_request]]. The
[[osdev wiki|https://wiki.osdev.org/IOAPIC]] has more technical
information. In `libirqhelp` the delivery of the interrupt is through an RPC
message that triggers a handler.
The source for `libirqhelp` can be found in `$hurd-src/libirqhelp/`.
First you must call `irqhelp_init ();` Then you can install an
interrupt handler with this function:
struct irq *
irqhelp_install_interrupt_handler (int gsi, int bus, int dev,
int fun, void (*handler)(void*),
void *context);
If `gsi` is `-1`, then ACPI will look up the global system interrupt from the PCI `bus`, `dev`, and `fun`.
If `bus`, `dev`, and `fun` are `-1`, then you must define `gsi`
(global system interrupt). You then use the returned `struct irq *`
to call the other functions.
You can enable an irq via:
void irqhelp_enable_irq (struct irq *irq);
You can disable an irq via:
void irqhelp_disable_irq (struct irq *irq);
You can deregister a handler via:
error_t irqhelp_remove_interrupt_handler (struct irq *irq);
To receive irq notifications, you have to call this next function in a separate thread, giving the `struct irq *` as `arg`.
void * irqhelp_server_loop (void *arg);
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