I am trying to identify the interrupt used for the USB keyboard in Linux Debian. After pulling out my USB keyboad then plugging it back in dmesg shows me this:
[11614.703111] usb 3-5: new low-speed USB device number 6 using xhci_hcd
[11614.865981] usb 3-5: New USB device found, idVendor=03f0, idProduct=0024, bcdDevice= 1.30
[11614.865986] usb 3-5: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[11614.865987] usb 3-5: Product: HP Basic USB Keyboard
[11614.865988] usb 3-5: Manufacturer: CHICONY
[11614.874343] input: CHICONY HP Basic USB Keyboard as /devices/pci0000:00/0000:00:14.0/usb3/3-5/3-5:1.0/0003:03F0:0024.0004/input/input18
[11614.931239] hid-generic 0003:03F0:0024.0004: input,hidraw0: USB HID v1.11 Keyboard [CHICONY HP Basic USB Keyboard] on usb-0000:00:14.0-5/input0
So the first line:
[11614.703111] usb 3-5: new low-speed USB device number 6 using xhci_hcd
tells me it is using xhci_hcd
cat /proc/interrupts shows me:
CPU0 CPU1 CPU2 CPU3
0: 8 0 0 0 IO-APIC 2-edge timer
8: 0 1 0 0 IO-APIC 8-edge rtc0
9: 0 162 0 0 IO-APIC 9-fasteoi acpi
18: 0 0 0 2 IO-APIC 18-fasteoi i801_smbus
20: 0 0 64 0 IO-APIC 20-fasteoi ehci_hcd:usb1
23: 82 0 0 0 IO-APIC 23-fasteoi ehci_hcd:usb2
27: 0 650883 0 0 PCI-MSI-0000:00:14.0 0-edge xhci_hcd
28: 0 0 66605 0 PCI-MSI-0000:00:1f.2 0-edge ahci[0000:00:1f.2]
29: 0 0 0 159157 PCI-MSIX-0000:03:00.0 0-edge enp3s0
30: 0 0 0 322094 PCI-MSI-0000:00:02.0 0-edge i915
31: 16 0 0 0 PCI-MSI-0000:00:16.0 0-edge mei_me
32: 0 178 0 0 PCI-MSI-0000:00:03.0 0-edge snd_hda_intel:card0
33: 0 0 534 0 PCI-MSI-0000:00:1b.0 0-edge snd_hda_intel:card1
NMI: 94 96 89 108 Non-maskable interrupts
LOC: 5368769 1507714 1256607 10547240 Local timer interrupts
SPU: 0 0 0 0 Spurious interrupts
PMI: 94 96 89 108 Performance monitoring interrupts
IWI: 36845 36878 37537 325227 IRQ work interrupts
RTR: 0 0 0 0 APIC ICR read retries
RES: 204443 205158 195796 182874 Rescheduling interrupts
CAL: 692129 737982 706767 684310 Function call interrupts
TLB: 512214 552127 541894 518037 TLB shootdowns
TRM: 0 0 0 0 Thermal event interrupts
THR: 0 0 0 0 Threshold APIC interrupts
DFR: 0 0 0 0 Deferred Error APIC interrupts
MCE: 0 0 0 0 Machine check exceptions
MCP: 47 48 48 48 Machine check polls
ERR: 0
MIS: 0
PIN: 0 0 0 0 Posted-interrupt notification event
NPI: 0 0 0 0 Nested posted-interrupt event
PIW: 0 0 0 0 Posted-interrupt wakeup event
So is interrupt 27 being used for the USB keyboard? If it is why am I unable to:
int ret = request_irq(irq_number, my_interrupt_handler, irq_flags, devname, dev_id);
Full code is below:
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
static int counter = 0;
// Define your interrupt handler function
irqreturn_t my_interrupt_handler(int irq, void *dev_id)
{
// Your interrupt handling code here
//printk(KERN_INFO "key pressed\n")
pr_info("Keypress Counter:%d\n", counter++);
return IRQ_HANDLED;
}
// Module initialization function
static int __init my_init(void)
{
int irq_number = 27; // IRQ number
const char devname = "my_device"; // Device name, can be used for identifying the interrupt source
unsigned long irq_flags = IRQF_SHARED; // Flags for interrupt handling, modify as needed
void dev_id = NULL; // Device identification, can be a pointer to device-specific data
// Register the interrupt handler
int ret = request_irq(irq_number, my_interrupt_handler, irq_flags, devname, dev_id);
if (ret) {
printk(KERN_ERR "Failed to register IRQ %d\n", irq_number);
pr_info("%s: In init\n", __func__);
return ret;
}
printk(KERN_INFO "Interrupt handler registered successfully\n");
return 0;
}
// Module exit function
static void __exit my_exit(void)
{
int irq_number = 27; // IRQ number
void *dev_id = NULL; // Device identification
// Unregister the interrupt handler
free_irq(irq_number, dev_id);
printk(KERN_INFO "Interrupt handler unregistered\n");
}
// Module initialization and exit macros
module_init(my_init);
module_exit(my_exit);
// Module metadata
MODULE_LICENSE("GPL");
u1686_grawity request_irq is a function in the Linux kernel used to request an interrupt line. It can be used with both legacy IRQs and MSI-X (Message Signaled Interrupts Extended).
For legacy IRQs, you typically specify the IRQ number directly. For MSI-X interrupts, you usually specify the MSI-X vector number, which is used to request the corresponding interrupt line.
The request_irq function has been adapted to work with modern interrupt mechanisms like MSI-X to accommodate the evolving hardware architectures and support newer features efficiently.
So, yes, request_irq does work with MSI-X interrupts along with legacy IRQs in the Linux kernel.
