10.7. Quick Reference

These symbols related to interrupt management were introduced in this chapter:

#include <linux/interrupt.h>

int request_irq(unsigned int irq, irqreturn_t (*handler)( ), unsigned long

flags, const char *dev_name, void *dev_id);

void free_irq(unsigned int irq, void *dev_id);

Calls that register and unregister an interrupt handler.

#include <linux/irq.h.h>

int can_request_irq(unsigned int irq, unsigned long flags);

This function, available on the i386 and x86_64 architectures, returns a nonzero value if an attempt to allocate the given interrupt line succeeds.

#include <asm/signal.h>

SA_INTERRUPT

SA_SHIRQ

SA_SAMPLE_RANDOM

Flags for request_irq. SA_INTERRUPT requests installation of a fast handler (as opposed to a slow one). SA_SHIRQ installs a shared handler, and the third flag asserts that interrupt timestamps can be used to generate system entropy.

/proc/interrupts

/proc/stat

Filesystem nodes that report information about hardware interrupts and installed handlers.

unsigned long probe_irq_on(void);

int probe_irq_off(unsigned long);

Functions used by the driver when it has to probe to determine which interrupt line is being used by a device. The result of probe_irq_on must be passed back to probe_irq_off after the interrupt has been generated. The return value of probe_irq_off is the detected interrupt number.

IRQ_NONE

IRQ_HANDLED

IRQ_RETVAL(int x)

The possible return values from an interrupt handler, indicating whether an actual interrupt from the device was present.

void disable_irq(int irq);

void disable_irq_nosync(int irq);

void enable_irq(int irq);

A driver can enable and disable interrupt reporting. If the hardware tries to generate an interrupt while interrupts are disabled, the interrupt is lost forever. A driver using a shared handler must not use these functions.

void local_irq_save(unsigned long flags);

void local_irq_restore(unsigned long flags);

Use local_irq_save to disable interrupts on the local processor and remember their previous state. The flags can be passed to local_irq_restore to restore the previous interrupt state.

void local_irq_disable(void);

void local_irq_enable(void);

Functions that unconditionally disable and enable interrupts on the current processor.