Registering Interrupt Handlers
Registering interrupt handlers is a fundamental part of writing device drivers in C for the Linux kernel. Interrupts allow hardware devices to signal the processor asynchronously, letting your driver respond to events such as data arrival or hardware errors without constantly polling the device. To handle these signals, you must register an interrupt handlerβa special function that the kernel calls when the device triggers its interrupt line. This process involves associating your handler function with a specific interrupt number, typically using the kernel's request_irq function.
register_interrupt.c
1234567891011121314151617181920212223242526272829303132333435363738394041#include <linux/module.h> #include <linux/interrupt.h> #include <linux/kernel.h> #define MY_IRQ 19 // Replace with your device's IRQ number static irqreturn_t my_interrupt_handler(int irq, void *dev_id) { printk(KERN_INFO "Interrupt %d received!\n", irq); // Handle the interrupt (read/write device registers, etc.) return IRQ_HANDLED; } static int __init my_driver_init(void) { int result; result = request_irq(MY_IRQ, // IRQ number my_interrupt_handler,// Handler function IRQF_SHARED, // Flags (IRQF_SHARED if sharing) "my_device", // Device name (void *)my_interrupt_handler); // Device ID if (result) { printk(KERN_ERR "Failed to request IRQ %d\n", MY_IRQ); return result; } printk(KERN_INFO "IRQ %d registered successfully\n", MY_IRQ); return 0; } static void __exit my_driver_exit(void) { free_irq(MY_IRQ, (void *)my_interrupt_handler); printk(KERN_INFO "IRQ %d freed\n", MY_IRQ); } module_init(my_driver_init); module_exit(my_driver_exit); MODULE_LICENSE("GPL"); MODULE_AUTHOR("Your Name"); MODULE_DESCRIPTION("Simple IRQ registration example");
The core of interrupt handling is the handler function itself. This function must match the signature expected by the kernel: it takes the interrupt number and a pointer to device-specific data, and returns an irqreturn_t value. The registration code shown above uses request_irq to associate the handler with a specific IRQ line. The handler is typically kept minimal and efficient, as it runs in interrupt context, where long or blocking operations can cause problems for the whole system. You should only perform the most essential actions in the handler, such as acknowledging the interrupt and scheduling further processing if needed.
free_interrupt.c
1234567891011121314#include <linux/module.h> #include <linux/interrupt.h> #define MY_IRQ 19 static void __exit my_driver_exit(void) { free_irq(MY_IRQ, (void *)my_interrupt_handler); printk(KERN_INFO "IRQ %d freed\n", MY_IRQ); } module_exit(my_driver_exit); MODULE_LICENSE("GPL");
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Completion rate improved to 3.85Registering Interrupt Handlers
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Registering interrupt handlers is a fundamental part of writing device drivers in C for the Linux kernel. Interrupts allow hardware devices to signal the processor asynchronously, letting your driver respond to events such as data arrival or hardware errors without constantly polling the device. To handle these signals, you must register an interrupt handlerβa special function that the kernel calls when the device triggers its interrupt line. This process involves associating your handler function with a specific interrupt number, typically using the kernel's request_irq function.
register_interrupt.c
1234567891011121314151617181920212223242526272829303132333435363738394041#include <linux/module.h> #include <linux/interrupt.h> #include <linux/kernel.h> #define MY_IRQ 19 // Replace with your device's IRQ number static irqreturn_t my_interrupt_handler(int irq, void *dev_id) { printk(KERN_INFO "Interrupt %d received!\n", irq); // Handle the interrupt (read/write device registers, etc.) return IRQ_HANDLED; } static int __init my_driver_init(void) { int result; result = request_irq(MY_IRQ, // IRQ number my_interrupt_handler,// Handler function IRQF_SHARED, // Flags (IRQF_SHARED if sharing) "my_device", // Device name (void *)my_interrupt_handler); // Device ID if (result) { printk(KERN_ERR "Failed to request IRQ %d\n", MY_IRQ); return result; } printk(KERN_INFO "IRQ %d registered successfully\n", MY_IRQ); return 0; } static void __exit my_driver_exit(void) { free_irq(MY_IRQ, (void *)my_interrupt_handler); printk(KERN_INFO "IRQ %d freed\n", MY_IRQ); } module_init(my_driver_init); module_exit(my_driver_exit); MODULE_LICENSE("GPL"); MODULE_AUTHOR("Your Name"); MODULE_DESCRIPTION("Simple IRQ registration example");
The core of interrupt handling is the handler function itself. This function must match the signature expected by the kernel: it takes the interrupt number and a pointer to device-specific data, and returns an irqreturn_t value. The registration code shown above uses request_irq to associate the handler with a specific IRQ line. The handler is typically kept minimal and efficient, as it runs in interrupt context, where long or blocking operations can cause problems for the whole system. You should only perform the most essential actions in the handler, such as acknowledging the interrupt and scheduling further processing if needed.
free_interrupt.c
1234567891011121314#include <linux/module.h> #include <linux/interrupt.h> #define MY_IRQ 19 static void __exit my_driver_exit(void) { free_irq(MY_IRQ, (void *)my_interrupt_handler); printk(KERN_INFO "IRQ %d freed\n", MY_IRQ); } module_exit(my_driver_exit); MODULE_LICENSE("GPL");
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