Linux Device Drivers

Quick Reference

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

#include <linux/sched.h> , int request_irq(unsigned int irq, void (*handler)(), unsigned long flags, const char *device, void *dev_id); , void free_irq(unsigned int irq, void *dev_id);

These calls are used to register and unregister an interrupt handler. Kernels older than 2.0 lack the dev_id argument.

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

These filesystem nodes are used to report information about hardware interrupts and installed handlers.

unsigned long probe_irq_on(void); , int probe_irq_off(unsigned long);

These functions are used by the driver when it has to probe to determine what 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.

void disable_irq(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. Calling these functions from a top-half handler has no effect. A driver using a shared handler must not use ...